Modeling greenhouse gas emissions from dairy farms.

Science.gov (United States)

Rotz, C Alan

2017-11-15

Dairy farms have been identified as an important source of greenhouse gas emissions. Within the farm, important emissions include enteric CH 4 from the animals, CH 4 and N 2 O from manure in housing facilities during long-term storage and during field application, and N 2 O from nitrification and denitrification processes in the soil used to produce feed crops and pasture. Models using a wide range in level of detail have been developed to represent or predict these emissions. They include constant emission factors, variable process-related emission factors, empirical or statistical models, mechanistic process simulations, and life cycle assessment. To fully represent farm emissions, models representing the various emission sources must be integrated to capture the combined effects and interactions of all important components. Farm models have been developed using relationships across the full scale of detail, from constant emission factors to detailed mechanistic simulations. Simpler models, based upon emission factors and empirical relationships, tend to provide better tools for decision support, whereas more complex farm simulations provide better tools for research and education. To look beyond the farm boundaries, life cycle assessment provides an environmental accounting tool for quantifying and evaluating emissions over the full cycle, from producing the resources used on the farm through processing, distribution, consumption, and waste handling of the milk and dairy products produced. Models are useful for improving our understanding of farm processes and their interacting effects on greenhouse gas emissions. Through better understanding, they assist in the development and evaluation of mitigation strategies for reducing emissions and improving overall sustainability of dairy farms. The Authors. Published by the Federation of Animal Science Societies and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article

Bi-Level Decentralized Active Power Control for Large-Scale Wind Farm Cluster

DEFF Research Database (Denmark)

Huang, Shengli; Wu, Qiuwei; Guo, Yifei

2018-01-01

This paper presents a bi-level decentralized active power control (DAPC) for a large-scale wind farm cluster, consisting of several wind farms for better active power dispatch. In the upper level, a distributed active power control scheme based on the distributed consensus is designed to achieve...... fair active power sharing among multiple wind farms, which generates the power reference for each wind farm. A distributed estimator is used to estimate the total available power of all wind farms. In the lower level, a centralized control scheme based on the Model Predictive Control (MPC) is proposed...... to regulate active power outputs of all wind turbines (WTs) within a wind farm, which reduces the fatigue loads of WTs while tracking the power reference obtained from the upper level control. A wind farm cluster with 8 wind farms and totally 160 WTs, was used to test the control performance of the proposed...

Wind Farm parametrization in the mesoscale model WRF

DEFF Research Database (Denmark)

Volker, Patrick; Badger, Jake; Hahmann, Andrea N.

2012-01-01

, but are parametrized as another sub-grid scale process. In order to appropriately capture the wind farm wake recovery and its direction, two properties are important, among others, the total energy extracted by the wind farm and its velocity deficit distribution. In the considered parametrization the individual...... the extracted force is proportional to the turbine area interfacing a grid cell. The sub-grid scale wake expansion is achieved by adding turbulence kinetic energy (proportional to the extracted power) to the flow. The validity of both wind farm parametrizations has been verified against observational data. We...... turbines produce a thrust dependent on the background velocity. For the sub-grid scale velocity deficit, the entrainment from the free atmospheric flow into the wake region, which is responsible for the expansion, is taken into account. Furthermore, since the model horizontal distance is several times...

The Interactive Effect of Diversification and Farming Scale on Productivity of Family Farm:Taking Rice Cultivation as An Example

Science.gov (United States)

Wei, Zhou

2017-05-01

Based on the diversification and cultivation scale, the rice cropping data of rural fixed observation points in 2011 were selected and the effect of diversification degree on rice productivity was analyzed by the Tobit model. The empirical results of the model show that diversification of sample farm will lead to loss of rice production efficiency. With the increase of rice planting scale, the loss of rice production efficiency will need to be further increased by diversification. Thus, we should stick to the family farm of specialized production operation. The transfer of land, the price and quantity of leasing, respecting the law of the market; the raising of funds can be considered non-subsidized capital market financing to help, while maintaining a certain degree of diversification, to avoid idle assets, low resource efficiency loss.

Modelling the smart farm

Directory of Open Access Journals (Sweden)

Michael J. O'Grady

2017-09-01

Full Text Available Smart farming envisages the harnessing of Information and Communication Technologies as an enabler of more efficient, productive, and profitable farming enterprises. Such technologies do not suffice on their own; rather they must be judiciously combined to deliver meaningful information in near real-time. Decision-support tools incorporating models of disparate farming activities, either on their own or in combination with other models, offer one popular approach; exemplars include GPFARM, APSIM, GRAZPLAN amongst many others. Such models tend to be generic in nature and their adoption by individual farmers is minimal. Smart technologies offer an opportunity to remedy this situation; farm-specific models that can reflect near real-time events become tractable using such technologies. Research on the development, and application of farm-specific models is at a very early stage. This paper thus presents an overview of models within the farming enterprise; it then reviews the state-of the art in smart technologies that promise to enable a new generation of enterprise-specific models that will underpin future smart farming enterprises.

Optimal management of on-farm resources in small-scale dairy systems of Central Mexico: model development and evaluation.

Science.gov (United States)

Castelán-Ortega, Octavio Alonso; Martínez-García, Carlos Galdino; Mould, Fergus L; Dorward, Peter; Rehman, Tahir; Rayas-Amor, Adolfo Armando

2016-06-01

This study evaluates the available on-farm resources of five case studies typified as small-scale dairy systems in central Mexico. A comprehensive mixed-integer linear programming model was developed and applied to two case studies. The optimal plan suggested the following: (1) instruction and utilization of maize silage, (2) alfalfa hay making that added US$140/ha/cut to the total net income, (3) allocation of land to cultivated pastures in a ratio of 27:41(cultivated pastures/maize crop) rather than at the current 14:69, and dairy cattle should graze 12 h/day, (4) to avoid grazing of communal pastures because this activity represented an opportunity cost of family labor that reduced the farm net income, and (5) that the highest farm net income was obtained when liquid milk and yogurt sales were included in the optimal plan. In the context of small-scale dairy systems of central Mexico, the optimal plan would need to be implemented gradually to enable farmers to develop required skills and to change management strategies from reliance on forage and purchased concentrate to pasture-based and conserved forage systems.

Whole-farm models to quantify greenhouse gas emissions and their potential use for linking climate change mitigation and adaptation in temperate grassland ruminant-based farming systems

DEFF Research Database (Denmark)

del Prado, A; Crosson, P; Olesen, Jørgen E

2013-01-01

The farm level is the most appropriate scale for evaluating options for mitigating greenhouse gas (GHG) emissions, because the farm represents the unit at which management decisions in livestock production are made. To date, a number of whole farm modelling approaches have been developed to quant......The farm level is the most appropriate scale for evaluating options for mitigating greenhouse gas (GHG) emissions, because the farm represents the unit at which management decisions in livestock production are made. To date, a number of whole farm modelling approaches have been developed...... components and the sensitivity of GHG outputs and mitigation measures to different approaches. Potential challenges for linking existing models with the simulation of impacts and adaptation measures under climate change are explored along with a brief discussion of the effects on other ecosystem services....

Effects of farm heterogeneity and methods for upscaling on modelled nitrogen losses in agricultural landscapes

International Nuclear Information System (INIS)

Dalgaard, T.; Hutchings, N.; Dragosits, U.; Olesen, J.E.; Kjeldsen, C.; Drouet, J.L.; Cellier, P.

2011-01-01

The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20-30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N accumulation (p > 0.95) was also identified and needs to be included when modelling landscape level N-fluxes and greenhouse gas emissions. - Highlights: → Farm-N balances and the distribution on types of N-losses are modelled for 56 farms. → Farm type significantly affects N-losses and soil-N accumulation. → A non-linear relation between livestock density and ammonia loss is identified. → Approaches for upscaling from farm to landscape level are discussed. → Accounting farm heterogeneity is important when upscaling N-losses. - This study illustrates the importance of including non-linear effects of farm and landscape heterogeneity on the modelling and upscaling of farm nitrogen losses and greenhouse gas emissions in agricultural landscapes.

Effects of farm heterogeneity and methods for upscaling on modelled nitrogen losses in agricultural landscapes

Energy Technology Data Exchange (ETDEWEB)

Dalgaard, T., E-mail: tommy.dalgaard@agrsci.dk [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Hutchings, N. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Dragosits, U. [CEH Edinburgh, Bush Estate, Penicuik, Midlothian EH26 0QB, Scotland (United Kingdom); Olesen, J.E.; Kjeldsen, C. [Aarhus University, Department of Agroecology, Blichers Alle 20, P.O. Box 50, DK-8830 Tjele (Denmark); Drouet, J.L.; Cellier, P. [INRA, UMR Environnement et Grandes Cultures, BP 01, 78850 Thiverval-Grignon (France)

2011-11-15

The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20-30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N accumulation (p > 0.95) was also identified and needs to be included when modelling landscape level N-fluxes and greenhouse gas emissions. - Highlights: > Farm-N balances and the distribution on types of N-losses are modelled for 56 farms. > Farm type significantly affects N-losses and soil-N accumulation. > A non-linear relation between livestock density and ammonia loss is identified. > Approaches for upscaling from farm to landscape level are discussed. > Accounting farm heterogeneity is important when upscaling N-losses. - This study illustrates the importance of including non-linear effects of farm and landscape heterogeneity on the modelling and upscaling of farm nitrogen losses and greenhouse gas emissions in agricultural landscapes.

Field Scale Spatial Modelling of Surface Soil Quality Attributes in Controlled Traffic Farming

Science.gov (United States)

Guenette, Kris; Hernandez-Ramirez, Guillermo

2017-04-01

The employment of controlled traffic farming (CTF) can yield improvements to soil quality attributes through the confinement of equipment traffic to tramlines with the field. There is a need to quantify and explain the spatial heterogeneity of soil quality attributes affected by CTF to further improve our understanding and modelling ability of field scale soil dynamics. Soil properties such as available nitrogen (AN), pH, soil total nitrogen (STN), soil organic carbon (SOC), bulk density, macroporosity, soil quality S-Index, plant available water capacity (PAWC) and unsaturated hydraulic conductivity (Km) were analysed and compared among trafficked and un-trafficked areas. We contrasted standard geostatistical methods such as ordinary kriging (OK) and covariate kriging (COK) as well as the hybrid method of regression kriging (ROK) to predict the spatial distribution of soil properties across two annual cropland sites actively employing CTF in Alberta, Canada. Field scale variability was quantified more accurately through the inclusion of covariates; however, the use of ROK was shown to improve model accuracy despite the regression model composition limiting the robustness of the ROK method. The exclusion of traffic from the un-trafficked areas displayed significant improvements to bulk density, macroporosity and Km while subsequently enhancing AN, STN and SOC. The ability of the regression models and the ROK method to account for spatial trends led to the highest goodness-of-fit and lowest error achieved for the soil physical properties, as the rigid traffic regime of CTF altered their spatial distribution at the field scale. Conversely, the COK method produced the most optimal predictions for the soil nutrient properties and Km. The use of terrain covariates derived from light ranging and detection (LiDAR), such as of elevation and topographic position index (TPI), yielded the best models in the COK method at the field scale.

A socio-hydrologic model of coupled water-agriculture dynamics with emphasis on farm size.

Science.gov (United States)

Brugger, D. R.; Maneta, M. P.

2015-12-01

Agricultural land cover dynamics in the U.S. are dominated by two trends: 1) total agricultural land is decreasing and 2) average farm size is increasing. These trends have important implications for the future of water resources because 1) growing more food on less land is due in large part to increased groundwater withdrawal and 2) larger farms can better afford both more efficient irrigation and more groundwater access. However, these large-scale trends are due to individual farm operators responding to many factors including climate, economics, and policy. It is therefore difficult to incorporate the trends into watershed-scale hydrologic models. Traditional scenario-based approaches are valuable for many applications, but there is typically no feedback between the hydrologic model and the agricultural dynamics and so limited insight is gained into the how agriculture co-evolves with water resources. We present a socio-hydrologic model that couples simplified hydrologic and agricultural economic dynamics, accounting for many factors that depend on farm size such as irrigation efficiency and returns to scale. We introduce an "economic memory" (EM) state variable that is driven by agricultural revenue and affects whether farms are sold when land market values exceed expected returns from agriculture. The model uses a Generalized Mixture Model of Gaussians to approximate the distribution of farm sizes in a study area, effectively lumping farms into "small," "medium," and "large" groups that have independent parameterizations. We apply the model in a semi-arid watershed in the upper Columbia River Basin, calibrating to data on streamflow, total agricultural land cover, and farm size distribution. The model is used to investigate the sensitivity of the coupled system to various hydrologic and economic scenarios such as increasing market value of land, reduced surface water availability, and increased irrigation efficiency in small farms.

Wind farm production estimates

DEFF Research Database (Denmark)

Larsen, Torben J.; Larsen, Gunner Chr.; Aagaard Madsen, Helge

2012-01-01

In this paper, the Dynamic Wake Meandering (DWM) model is applied for simulation of wind farm production. In addition to the numerical simulations, measured data have been analyzed in order to provide the basis for a full-scale verification of the model performance. The basic idea behind the DWMm......In this paper, the Dynamic Wake Meandering (DWM) model is applied for simulation of wind farm production. In addition to the numerical simulations, measured data have been analyzed in order to provide the basis for a full-scale verification of the model performance. The basic idea behind...... the DWMmodel is to model the in- stationary wind farm flow characteristics by considering wind turbine wakes as passive tracers continuously emitted from the wind farm turbines each with a downstream transport pro- cess dictated by large scale turbulent eddies (lateral and ver- tical transportation; i.......e. meandering) and Taylor advection. For the present purpose, the DWM model has been im- plemented in the aeroelastic code HAWC2 [1], and the per- formance of the resulting model complex is mainly verified by comparing simulated and measured loads for the Dutch off-shore Egmond aan Zee wind farm [2]. This farm...

Medium fidelity modelling of loads in wind farms under non-neutral ABL stability conditions – a full-scale validation study

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Larsen, Torben J.; Chougule, A.

2017-01-01

The aim of the present paper is to demonstrate the capability of medium fidelity modelling of wind turbine component fatigue loading, when the wind turbines are subjected to wake affected non-stationary flow fields under non-neutral atmospheric stability conditions. To accomplish this we combine......) in description of both large- and small scale atmospheric boundary layer turbulence is facilitated by a generalization of the classical Mann spectral tensor, which consistently includes buoyancy effects. With non-stationary wind turbine inflow fields modelled as described above, fatigue loads are obtained using...... the state-of-the art aeroelastic model HAWC2. The Lillgrund offshore wind farm (WF) constitute an interesting case study for wind farm model validation, because the WT interspacing is small, which in turn means that wake effects are significant. A huge data set, comprising 5 years of blade and tower load...

Contribution of large scale coherence to wind turbine power: A large eddy simulation study in periodic wind farms

Science.gov (United States)

Chatterjee, Tanmoy; Peet, Yulia T.

2018-03-01

Length scales of eddies involved in the power generation of infinite wind farms are studied by analyzing the spectra of the turbulent flux of mean kinetic energy (MKE) from large eddy simulations (LES). Large-scale structures with an order of magnitude bigger than the turbine rotor diameter (D ) are shown to have substantial contribution to wind power. Varying dynamics in the intermediate scales (D -10 D ) are also observed from a parametric study involving interturbine distances and hub height of the turbines. Further insight about the eddies responsible for the power generation have been provided from the scaling analysis of two-dimensional premultiplied spectra of MKE flux. The LES code is developed in a high Reynolds number near-wall modeling framework, using an open-source spectral element code Nek5000, and the wind turbines have been modelled using a state-of-the-art actuator line model. The LES of infinite wind farms have been validated against the statistical results from the previous literature. The study is expected to improve our understanding of the complex multiscale dynamics in the domain of large wind farms and identify the length scales that contribute to the power. This information can be useful for design of wind farm layout and turbine placement that take advantage of the large-scale structures contributing to wind turbine power.

Effects of farm heterogeneity and methods for upscaling on modelled nitrogen losses in agricultural landscapes

DEFF Research Database (Denmark)

Dalgaard, Tommy; Hutchings, Nicholas John; Dragosits, U

2011-01-01

The aim of this study is to illustrate the importance of farm scale heterogeneity on nitrogen (N) losses in agricultural landscapes. Results are exemplified with a chain of N models calculating farm-N balances and distributing the N-surplus to N-losses (volatilisation, denitrification, leaching......) and soil-N accumulation/release in a Danish landscape. Possible non-linearities in upscaling are assessed by comparing average model results based on (i) individual farm level calculations and (ii) averaged inputs at landscape level. Effects of the non-linearities that appear when scaling up from farm...... to landscape are demonstrated. Especially in relation to ammonia losses the non-linearity between livestock density and N-loss is significant (p > 0.999), with around 20–30% difference compared to a scaling procedure not taking this non-linearity into account. A significant effect of farm type on soil N...

Antimicrobial use and antimicrobial susceptibility in Escherichia coli on small- and medium-scale pig farms in north-eastern Thailand

Directory of Open Access Journals (Sweden)

G. Ström

2017-07-01

Full Text Available Abstract Background Intensification of livestock production seen in many low- and middle-income countries is often believed to be associated with increased use of antimicrobials, and may hence contribute to the emergence of antimicrobial resistance. The aim of this study was to map antimicrobial use on small- (n = 25 and medium-scale (n = 27 pig farms in north-eastern Thailand, and to compare antimicrobial susceptibility of commensal Escherichia coli isolated from sows on these farms. Methods Information regarding pig husbandry and antimicrobial treatment regimens was obtained by the use of semi-structured questionnaires. Faecal samples were collected from three healthy sows at each farm, and Escherichia coli was cultured and analysed for antimicrobial susceptibility using the broth microdilution method. Multilevel regression models were used to compare antimicrobial susceptibility between isolates from small- and medium-scale farms. Results All farms included in the study administered antimicrobials to their sows. Small-scale farmers most commonly (64% decided themselves when to give antimicrobials and the majority (60% bought the medicines at the local store or pharmacy, whereas farmers on medium-scale farms always discussed antimicrobial treatment with a veterinarian. Medium-scale farms used a greater diversity of antimicrobials than small-scale farms and did also administer antimicrobials in feed to a higher extent. High levels of antimicrobial resistance to several critically important antimicrobials for human medicine (including ciprofloxacin, streptomycin and ampicillin were found in isolates from both small- and medium-scale farms. Resistance levels were significantly (P < 0.05 higher in isolates from medium-scale farms for several of the antimicrobials tested, as well as the level of multidrug-resistance (P = 0.026. Conclusion The routines regarding access and administration of antimicrobials differed between the small- and

Improving Wind Farm Dispatchability Using Model Predictive Control for Optimal Operation of Grid-Scale Energy Storage

Directory of Open Access Journals (Sweden)

Douglas Halamay

2014-09-01

Full Text Available This paper demonstrates the use of model-based predictive control for energy storage systems to improve the dispatchability of wind power plants. Large-scale wind penetration increases the variability of power flow on the grid, thus increasing reserve requirements. Large energy storage systems collocated with wind farms can improve dispatchability of the wind plant by storing energy during generation over-the-schedule and sourcing energy during generation under-the-schedule, essentially providing on-site reserves. Model predictive control (MPC provides a natural framework for this application. By utilizing an accurate energy storage system model, control actions can be planned in the context of system power and state-of-charge limitations. MPC also enables the inclusion of predicted wind farm performance over a near-term horizon that allows control actions to be planned in anticipation of fast changes, such as wind ramps. This paper demonstrates that model-based predictive control can improve system performance compared with a standard non-predictive, non-model-based control approach. It is also demonstrated that secondary objectives, such as reducing the rate of change of the wind plant output (i.e., ramps, can be considered and successfully implemented within the MPC framework. Specifically, it is shown that scheduling error can be reduced by 81%, reserve requirements can be improved by up to 37%, and the number of ramp events can be reduced by 74%.

A Hybrid Wind-Farm Parametrization for Mesoscale and Climate Models

Science.gov (United States)

Pan, Yang; Archer, Cristina L.

2018-04-01

To better understand the potential impact of wind farms on weather and climate at the regional to global scales, a new hybrid wind-farm parametrization is proposed for mesoscale and climate models. The proposed parametrization is a hybrid model because it is not based on physical processes or conservation laws, but on the multiple linear regression of the results of large-eddy simulations (LES) with the geometric properties of the wind-farm layout (e.g., the blockage ratio and blockage distance). The innovative aspect is that each wind turbine is treated individually based on its position in the farm and on the wind direction by predicting the velocity upstream of each turbine. The turbine-induced forces and added turbulence kinetic energy (TKE) are first derived analytically and then implemented in the Weather Research and Forecasting model. Idealized simulations of the offshore Lillgrund wind farm are conducted. The wind-speed deficit and TKE predicted with the hybrid model are in excellent agreement with those from the LES results, while the wind-power production estimated with the hybrid model is within 10% of that observed. Three additional wind farms with larger inter-turbine spacing than at Lillgrund are also considered, and a similar agreement with LES results is found, proving that the hybrid parametrization works well with any wind farm regardless of the spacing between turbines. These results indicate the wind-turbine position, wind direction, and added TKE are essential in accounting for the wind-farm effects on the surroundings, for which the hybrid wind-farm parametrization is a promising tool.

Modeling a farm population to estimate on-farm compliance costs and environmental effects of a grassland extensification scheme at the regional scale

DEFF Research Database (Denmark)

Uthes, Sandra; Sattler, Claudia; Piorr, Annette

2010-01-01

We used a farm-level modeling approach to estimate on-farm compliance costs and environmental effects of a grassland extensification scheme in the district of Ostprignitz-Ruppin, Germany. The behavior of the regional farm population (n = 585) consisting of different farm types with different...... and environmental effects were heterogeneous in space and farm types as a result of different agricultural production and site characteristics. On-farm costs ranged from zero up to almost 1500 Euro/ha. Such high costs occurred only in a very small part of the regional area, whereas the majority of the grassland had...... low on-farm costs below 50 Euro/ha. Environmental effects were moderate and greater on high-yield than on low-yield grassland. The low effectiveness combined with low on-farm costs in large parts of the region indicates that the scheme is not well targeted. The soft scheme design results from...

Modelling potential production of macroalgae farms in UK and Dutch coastal waters

Directory of Open Access Journals (Sweden)

J. van der Molen

2018-02-01

Full Text Available There is increasing interest in macroalgae farming in European waters for a range of applications, including food, chemical extraction for biofuel production. This study uses a 3-D numerical model of hydrodynamics and biogeochemistry to investigate potential production and environmental effects of macroalgae farming in UK and Dutch coastal waters. The model included four experimental farms in different coastal settings in Strangford Lough (Northern Ireland, in Sound of Kerrera and Lynn of Lorne (north-west Scotland and in the Rhine plume (the Netherlands, as well as a hypothetical large-scale farm off the UK north Norfolk coast. The model could not detect significant changes in biogeochemistry and plankton dynamics at any of the farm sites averaged over the farming season. The results showed a range of macroalgae growth behaviours in response to simulated environmental conditions. These were then compared with in situ observations where available, showing good correspondence for some farms and less good correspondence for others. At the most basic level, macroalgae production depended on prevailing nutrient concentrations and light conditions, with higher levels of both resulting in higher macroalgae production. It is shown that under non-elevated and interannually varying winter nutrient conditions, farming success was modulated by the timings of the onset of increasing nutrient concentrations in autumn and nutrient drawdown in spring. Macroalgae carbohydrate content also depended on nutrient concentrations, with higher nutrient concentrations leading to lower carbohydrate content at harvest. This will reduce the energy density of the crop and thus affect its suitability for conversion into biofuel. For the hypothetical large-scale macroalgae farm off the UK north Norfolk coast, the model suggested high, stable farm yields of macroalgae from year to year with substantial carbohydrate content and limited environmental effects.

Modelling potential production of macroalgae farms in UK and Dutch coastal waters

Science.gov (United States)

van der Molen, Johan; Ruardij, Piet; Mooney, Karen; Kerrison, Philip; O'Connor, Nessa E.; Gorman, Emma; Timmermans, Klaas; Wright, Serena; Kelly, Maeve; Hughes, Adam D.; Capuzzo, Elisa

2018-02-01

There is increasing interest in macroalgae farming in European waters for a range of applications, including food, chemical extraction for biofuel production. This study uses a 3-D numerical model of hydrodynamics and biogeochemistry to investigate potential production and environmental effects of macroalgae farming in UK and Dutch coastal waters. The model included four experimental farms in different coastal settings in Strangford Lough (Northern Ireland), in Sound of Kerrera and Lynn of Lorne (north-west Scotland) and in the Rhine plume (the Netherlands), as well as a hypothetical large-scale farm off the UK north Norfolk coast. The model could not detect significant changes in biogeochemistry and plankton dynamics at any of the farm sites averaged over the farming season. The results showed a range of macroalgae growth behaviours in response to simulated environmental conditions. These were then compared with in situ observations where available, showing good correspondence for some farms and less good correspondence for others. At the most basic level, macroalgae production depended on prevailing nutrient concentrations and light conditions, with higher levels of both resulting in higher macroalgae production. It is shown that under non-elevated and interannually varying winter nutrient conditions, farming success was modulated by the timings of the onset of increasing nutrient concentrations in autumn and nutrient drawdown in spring. Macroalgae carbohydrate content also depended on nutrient concentrations, with higher nutrient concentrations leading to lower carbohydrate content at harvest. This will reduce the energy density of the crop and thus affect its suitability for conversion into biofuel. For the hypothetical large-scale macroalgae farm off the UK north Norfolk coast, the model suggested high, stable farm yields of macroalgae from year to year with substantial carbohydrate content and limited environmental effects.

Multicriteria GIS modeling of wind and solar farms in Colorado

Energy Technology Data Exchange (ETDEWEB)

Janke, Jason R. [Metropolitan State College of Denver, Department of Earth and Atmospheric Sciences, CB 22 P.O. Box 173362-22, Denver, CO 80217-3362 (United States)

2010-10-15

The majority of electricity and heat in Colorado comes from coal and natural gas; however, renewable energy sources will play an integral role in the state's energy future. Colorado is the 11th windiest state and has more than 250 sunny days per year. The objectives of this research are to: 1) determine which landcover classes are affiliated with high wind and solar potential; and 2) identify areas that are suitable for wind and solar farms using multicriteria GIS modelling techniques. Renewable potential (NREL wind speed measurements at 50 m above the ground and NREL annual insolation data), landcover, population density, federal lands, and distance to roads, transmission lines, and cities were reclassified according to their suitability. Each was assigned weights based on their relative importance to one another. Superb wind classes are located in high alpine areas. Unfortunately, these areas are not suitable for large-scale wind farm development due to their inaccessibility and location within a sensitive ecosystem. Federal lands have low wind potential. According to the GIS model, ideal areas for wind farm development are located in northeastern Colorado. About 41 850 km{sup 2} of the state has model scores that are in the 90-100% range. Although annual solar radiation varies slightly, inter-mountain areas receive the most insolation. As far as federal lands, Indian reservations have the greatest solar input. The GIS model indicates that ideal areas for solar development are located in northwestern Colorado and east of Denver. Only 191 km{sup 2} of the state had model scores that were in the 90-100% range. These results suggest that the variables used in this analysis have more of an effect at eliminating non-suitable areas for large-scale solar farms; a greater area exists for suitable wind farms. However, given the statewide high insolation values with minimal variance, solar projects may be better suited for small-scale residential or commercial

Assessing biodiversity on the farm scale as basis for ecosystem service payments.

Science.gov (United States)

von Haaren, Christina; Kempa, Daniela; Vogel, Katrin; Rüter, Stefan

2012-12-30

Ecosystem services payments must be based on a standardised transparent assessment of the goods and services provided. This is especially relevant in the context of EU agri-environmental programs, but also for organic-food companies that foster environmental services on their contractor farms. Addressing the farm scale is important because land users/owners are major recipients of payments and they could be more involved in data generation and conservation management. A standardised system for measuring on-farm biodiversity does not yet exist that concentrates on performance indicators and includes farmers in generating information. A method is required that produces ordinal or metric scaled assessment results as well as management measures. Another requirement is the ease of application, which includes the ease of gathering input data and understandability. In order to respond to this need, we developed a method which is designed for automated application in an open source farm assessment system named MANUELA. The method produces an ordinal scale assessment of biodiversity that includes biotopes, species, biotope connectivity and the influence of land use. In addition, specific measures for biotope types are proposed. The open source geographical information system OpenJump is used for the implementation of MANUELA. The results of the trial applications and robustness tests show that the assessment can be implemented, for the most part, using existing information as well as data available from farmers or advisors. The results are more sensitive for showing on-farm achievements and changes than existing biotope-type classifications. Such a differentiated classification is needed as a basis for ecosystem service payments and for designing effective measures. The robustness of the results with respect to biotope connectivity is comparable to that of complex models, but it should be further improved. Interviews with the test farmers substantiate that the assessment

Experimental study of the impact of large-scale wind farms on land–atmosphere exchanges

International Nuclear Information System (INIS)

Zhang Wei; Markfort, Corey D; Porté-Agel, Fernando

2013-01-01

Large-scale wind farms, covering a significant portion of the land and ocean surface, may affect the transport of momentum, heat, mass and moisture between the atmosphere and the land locally and globally. To understand the wind-farm–atmosphere interaction, we conducted wind-tunnel experiments to study the surface scalar (heat) flux using model wind farms, consisting of more than ten rows of wind turbines—having typical streamwise and spanwise spacings of five and four rotor diameters—in a neutral boundary layer with a heated surface. The spatial distribution of the surface heat flux was mapped with an array of surface heat flux sensors within the quasi-developed regime of the wind-farm flow. Although the overall surface heat flux change produced by the wind farms was found to be small, with a net reduction of 4% for a staggered wind farm and nearly zero change for an aligned wind farm, the highly heterogeneous spatial distribution of the surface heat flux, dependent on the wind-farm layout, was significant. The difference between the minimum and maximum surface heat fluxes could be up to 12% and 7% in aligned and staggered wind farms, respectively. This finding is important for planning intensive agriculture practice and optimizing farm land use strategy regarding wind energy project development. The well-controlled wind-tunnel experiments presented in this study also provide a first comprehensive dataset on turbulent flow and scalar transport in wind farms, which can be further used to develop and validate new parameterizations of surface scalar fluxes in numerical models. (letter)

Optimal Selection of AC Cables for Large Scale Offshore Wind Farms

DEFF Research Database (Denmark)

Hou, Peng; Hu, Weihao; Chen, Zhe

2014-01-01

The investment of large scale offshore wind farms is high in which the electrical system has a significant contribution to the total cost. As one of the key components, the cost of the connection cables affects the initial investment a lot. The development of cable manufacturing provides a vast...... and systematical way for the optimal selection of cables in large scale offshore wind farms....

Farm-scale biogas development in Southern Germany

Energy Technology Data Exchange (ETDEWEB)

Koeberle, E [Biogaskontor, Obermarchtal (Germany)

1997-08-01

This work provides a description of the development of farm-scale plants in Bayern and Baden-Wuerttemberg. The historical development is explained as well as the technical. Main topics are digester concepts, stirring system and co-generation with dual-fuel and gas-engines. (au)

Distributed Model Predictive Control for Active Power Control of Wind Farm

DEFF Research Database (Denmark)

Zhao, Haoran; Wu, Qiuwei; Rasmussen, Claus Nygaard

2014-01-01

This paper presents the active power control of a wind farm using the Distributed Model Predictive Controller (D- MPC) via dual decomposition. Different from the conventional centralized wind farm control, multiple objectives such as power reference tracking performance and wind turbine load can...... be considered to achieve a trade-off between them. Additionally, D- MPC is based on communication among the subsystems. Through the interaction among the neighboring subsystems, the global optimization could be achieved, which significantly reduces the computation burden. It is suitable for the modern large......-scale wind farm control....

Modelling Farm Animal Welfare

Science.gov (United States)

Collins, Lisa M.; Part, Chérie E.

2013-01-01

Simple Summary In this review paper we discuss the different modeling techniques that have been used in animal welfare research to date. We look at what questions they have been used to answer, the advantages and pitfalls of the methods, and how future research can best use these approaches to answer some of the most important upcoming questions in farm animal welfare. Abstract The use of models in the life sciences has greatly expanded in scope and advanced in technique in recent decades. However, the range, type and complexity of models used in farm animal welfare is comparatively poor, despite the great scope for use of modeling in this field of research. In this paper, we review the different modeling approaches used in farm animal welfare science to date, discussing the types of questions they have been used to answer, the merits and problems associated with the method, and possible future applications of each technique. We find that the most frequently published types of model used in farm animal welfare are conceptual and assessment models; two types of model that are frequently (though not exclusively) based on expert opinion. Simulation, optimization, scenario, and systems modeling approaches are rarer in animal welfare, despite being commonly used in other related fields. Finally, common issues such as a lack of quantitative data to parameterize models, and model selection and validation are discussed throughout the review, with possible solutions and alternative approaches suggested. PMID:26487411

A model of ammonia volatilization from a grazing livestock farm

Science.gov (United States)

Hutchings, N. J.; Sommer, S. G.; Jarvis, S. C.

A dynamic model was developed to predict the ammonia volatilization from grazing livestock farms and to allow potential control measures to be evaluated. The relationships within the model were based on the underlying physical and chemical processes but empirically based factors were used to reduce the demand for input data and where the understanding of the underlying processes was inadequate. On a daily basis, the model simulates the partitioning of dietary nitrogen into dung and urine and its subsequent fate within the pasture or the slurry handling system. The fate of dry matter and water added in dung, urine and from other sources is also predicted. The model illustrates the indirect interactions between ammonia sources, highlights the influence of slurry management on ammonia losses, stresses the need for integrated, whole farm measurements and demonstrates that assessments of the impact of control measures may be misleading unless considered at the scale of the whole farm.

Modelling Farm Animal Welfare

Directory of Open Access Journals (Sweden)

Chérie E. Part

2013-05-01

Full Text Available The use of models in the life sciences has greatly expanded in scope and advanced in technique in recent decades. However, the range, type and complexity of models used in farm animal welfare is comparatively poor, despite the great scope for use of modeling in this field of research. In this paper, we review the different modeling approaches used in farm animal welfare science to date, discussing the types of questions they have been used to answer, the merits and problems associated with the method, and possible future applications of each technique. We find that the most frequently published types of model used in farm animal welfare are conceptual and assessment models; two types of model that are frequently (though not exclusively based on expert opinion. Simulation, optimization, scenario, and systems modeling approaches are rarer in animal welfare, despite being commonly used in other related fields. Finally, common issues such as a lack of quantitative data to parameterize models, and model selection and validation are discussed throughout the review, with possible solutions and alternative approaches suggested.

Design considerations for a farm-scale biogas plant based on pilot-scale anaerobic digesters loaded with rice straw and piggery wastewater

International Nuclear Information System (INIS)

Mussoline, Wendy; Esposito, Giovanni; Lens, Piet; Garuti, Gilberto; Giordano, Andrea

2012-01-01

Two pilot-scale (1 m 3 ) digesters filled with untreated rice straw and co-digested with raw pig wastewater were operated to obtain design parameters for a farm-scale biogas plant. Both digesters contained 50 kg of dry straw mixed with diluted pig wastewater to create dry digestion conditions (20% TS) and operated for 189 days with leachate recirculation. Digester A was designed for optimum performance (150 L of pig wastewater and mesophilic temperatures) while Digester B was designed to establish minimum inputs (60 L of pig wastewater at ambient temperatures). The pig wastewater provided sufficient buffering capacity to maintain appropriate pH values (between 7.0 and 8.1) and nutrient balances (TOC to TKN ratios of 20 in Digester A and 32 in Digester B). Total biogas production was 22,859 L in Digester A and 1420 L from Digester B, resulting in specific methane yields of 231 and 12 L CH 4 /kgVS added, respectively. Gas production in Digester A was directly correlated with temperature, but the overall lack of methanogenic activity was caused primarily by the reduced wastewater volume. Two theoretical farm-scale scenarios (considering both untreated and pretreated rice straw) were developed for a 100-ha rice farm. Either scenario can produce 100,000 m 3 CH 4 per year, yielding 328 MWh. Major differences including heat input, space requirements, loading frequency, digester volume, engine size, wastewater quantities, and additives are quantitatively defined. The appropriate choice for a farm-scale operation is the simplest model using untreated rice straw without additives, although six times more heat and twice as much reactor volume is required. -- Highlights: ► The co-digestion of untreated rice straw and piggery wastewater is investigated. ► Gas production increases with the volume of pig wastewater added and temperature. ► Pig wastewater alone can provide appropriate buffering capacity and nutrient balance. ► Pilot-scale results are used to establish

Prospective and participatory integrated assessment of agricultural systems from farm to regional scales: Comparison of three modeling approaches.

Science.gov (United States)

Delmotte, Sylvestre; Lopez-Ridaura, Santiago; Barbier, Jean-Marc; Wery, Jacques

2013-11-15

Evaluating the impacts of the development of alternative agricultural systems, such as organic or low-input cropping systems, in the context of an agricultural region requires the use of specific tools and methodologies. They should allow a prospective (using scenarios), multi-scale (taking into account the field, farm and regional level), integrated (notably multicriteria) and participatory assessment, abbreviated PIAAS (for Participatory Integrated Assessment of Agricultural System). In this paper, we compare the possible contribution to PIAAS of three modeling approaches i.e. Bio-Economic Modeling (BEM), Agent-Based Modeling (ABM) and statistical Land-Use/Land Cover Change (LUCC) models. After a presentation of each approach, we analyze their advantages and drawbacks, and identify their possible complementarities for PIAAS. Statistical LUCC modeling is a suitable approach for multi-scale analysis of past changes and can be used to start discussion about the futures with stakeholders. BEM and ABM approaches have complementary features for scenarios assessment at different scales. While ABM has been widely used for participatory assessment, BEM has been rarely used satisfactorily in a participatory manner. On the basis of these results, we propose to combine these three approaches in a framework targeted to PIAAS. Copyright © 2013 Elsevier Ltd. All rights reserved.

Parameter study of electric power production in wind farms - experiments using two model scale wind turbines

OpenAIRE

Ceccotti, Clio

2015-01-01

Wind farms are widely developed even if several unsolved problems need to be faced. The rotor-wake interaction involves different physical phenomena, not yet fully understood, directly affecting the overall wind farm power production. Numerical models and engineering rules have always been used to design wind farm layout but a spread between power predictions and results is verified. In this context wind energy research assumes a "back to basic" approach, by means of wind tunne...

Prototyping and farm system modelling - Partners on the road towards more sustainable farm systems?

NARCIS (Netherlands)

Sterk, B.; Ittersum, van M.K.; Leeuwis, C.; Wijnands, F.G.

2007-01-01

Farm system modelling and prototyping are two research methods proposed to enhance the process of developing sustainable farm systems. Farm system models provide means to formalize, expand and refine expert knowledge and to integrate this with scientific agro-ecological knowledge at the farm level.

Simultaneous nested modeling from the synoptic scale to the LES scale for wind energy applications

DEFF Research Database (Denmark)

Liu, Yubao; Warner, Tom; Liu, Yuewei

2011-01-01

This paper describes an advanced multi-scale weather modeling system, WRF–RTFDDA–LES, designed to simulate synoptic scale (~2000 km) to small- and micro-scale (~100 m) circulations of real weather in wind farms on simultaneous nested grids. This modeling system is built upon the National Center f...

An aggregate model of grid-connected, large-scale, offshore wind farm for power stability investigations-importance of windmill mechanical system

DEFF Research Database (Denmark)

Akhmatov, Vladislav; Knudsen, H.

2002-01-01

. Because the shaft system gives a soft coupling between the rotating wind turbine and the induction generator, the large-scale wind farm cannot always be reduced to one-machine equivalent and use of multi-machine equivalents will be necessary for reaching accuracy of the investigation results....... This will be in cases with irregular wind distribution over the wind farm area. The torsion mode of the shaft systems of large wind turbines is commonly in the range of 1-2 Hz and close to typical values of the electric power grid eigenfrequencies why there is a risk of oscillation between the wind turbines...... and the entire network. All these phenomena are different compared to previous experiences with modelling of conventional power plants with synchronous generators and stiff shaft systems....

Biogas infrastructure from farm-scale to regional scale, line-pack storage in biogas grids

NARCIS (Netherlands)

Hengeveld, Evert Jan

2016-01-01

Biogas infrastructure from farm-scale to regional scale, line-pack storage in biogas grids. The number of local and regional initiatives encouraging the production and use of regional produced energy grows. In these new developments biogas can play a role, as a producer of energy, but also in

Including spatial data in nutrient balance modelling on dairy farms

Science.gov (United States)

van Leeuwen, Maricke; van Middelaar, Corina; Stoof, Cathelijne; Oenema, Jouke; Stoorvogel, Jetse; de Boer, Imke

2017-04-01

The Annual Nutrient Cycle Assessment (ANCA) calculates the nitrogen (N) and phosphorus (P) balance at a dairy farm, while taking into account the subsequent nutrient cycles of the herd, manure, soil and crop components. Since January 2016, Dutch dairy farmers are required to use ANCA in order to increase understanding of nutrient flows and to minimize nutrient losses to the environment. A nutrient balance calculates the difference between nutrient inputs and outputs. Nutrients enter the farm via purchased feed, fertilizers, deposition and fixation by legumes (nitrogen), and leave the farm via milk, livestock, manure, and roughages. A positive balance indicates to which extent N and/or P are lost to the environment via gaseous emissions (N), leaching, run-off and accumulation in soil. A negative balance indicates that N and/or P are depleted from soil. ANCA was designed to calculate average nutrient flows on farm level (for the herd, manure, soil and crop components). ANCA was not designed to perform calculations of nutrient flows at the field level, as it uses averaged nutrient inputs and outputs across all fields, and it does not include field specific soil characteristics. Land management decisions, however, such as the level of N and P application, are typically taken at the field level given the specific crop and soil characteristics. Therefore the information that ANCA provides is likely not sufficient to support farmers' decisions on land management to minimize nutrient losses to the environment. This is particularly a problem when land management and soils vary between fields. For an accurate estimate of nutrient flows in a given farming system that can be used to optimize land management, the spatial scale of nutrient inputs and outputs (and thus the effect of land management and soil variation) could be essential. Our aim was to determine the effect of the spatial scale of nutrient inputs and outputs on modelled nutrient flows and nutrient use efficiencies

Equivalent models of wind farms by using aggregated wind turbines and equivalent winds

International Nuclear Information System (INIS)

Fernandez, L.M.; Garcia, C.A.; Saenz, J.R.; Jurado, F.

2009-01-01

As a result of the increasing wind farms penetration on power systems, the wind farms begin to influence power system, and therefore the modeling of wind farms has become an interesting research topic. In this paper, new equivalent models of wind farms equipped with wind turbines based on squirrel-cage induction generators and doubly-fed induction generators are proposed to represent the collective behavior on large power systems simulations, instead of using a complete model of wind farms where all the wind turbines are modeled. The models proposed here are based on aggregating wind turbines into an equivalent wind turbine which receives an equivalent wind of the ones incident on the aggregated wind turbines. The equivalent wind turbine presents re-scaled power capacity and the same complete model as the individual wind turbines, which supposes the main feature of the present equivalent models. Two equivalent winds are evaluated in this work: (1) the average wind from the ones incident on the aggregated wind turbines with similar winds, and (2) an equivalent incoming wind derived from the power curve and the wind incident on each wind turbine. The effectiveness of the equivalent models to represent the collective response of the wind farm at the point of common coupling to grid is demonstrated by comparison with the wind farm response obtained from the detailed model during power system dynamic simulations, such as wind fluctuations and a grid disturbance. The present models can be used for grid integration studies of large power system with an important reduction of the model order and the computation time

DairyWise, a whole-farm dairy model.

Science.gov (United States)

Schils, R L M; de Haan, M H A; Hemmer, J G A; van den Pol-van Dasselaar, A; de Boer, J A; Evers, A G; Holshof, G; van Middelkoop, J C; Zom, R L G

2007-11-01

A whole-farm dairy model was developed and evaluated. The DairyWise model is an empirical model that simulated technical, environmental, and financial processes on a dairy farm. The central component is the FeedSupply model that balanced the herd requirements, as generated by the DairyHerd model, and the supply of homegrown feeds, as generated by the crop models for grassland and corn silage. The output of the FeedSupply model was used as input for several technical, environmental, and economic submodels. The submodels simulated a range of farm aspects such as nitrogen and phosphorus cycling, nitrate leaching, ammonia emissions, greenhouse gas emissions, energy use, and a financial farm budget. The final output was a farm plan describing all material and nutrient flows and the consequences on the environment and economy. Evaluation of DairyWise was performed with 2 data sets consisting of 29 dairy farms. The evaluation showed that DairyWise was able to simulate gross margin, concentrate intake, nitrogen surplus, nitrate concentration in ground water, and crop yields. The variance accounted for ranged from 37 to 84%, and the mean differences between modeled and observed values varied between -5 to +3% per set of farms. We conclude that DairyWise is a powerful tool for integrated scenario development and evaluation for scientists, policy makers, extension workers, teachers and farmers.

Comparing offshore wind farm wake observed from satellite SAR and wake model results

Science.gov (United States)

Bay Hasager, Charlotte

2014-05-01

are modeled by various types of wake models. In the EERA DTOC project the model suite consists of engineering models (Ainslie, DWM, GLC, PARK, WASP/NOJ), simplified CFD models (FUGA, FarmFlow), full CFD models (CRES-flowNS, RANS), mesoscale model (SKIRON, WRF) and coupled meso-scale and microscale models. The comparison analysis between the satellite wind wake and model results will be presented and discussed. It is first time a comprehensive analysis is performed on this subject. The topic gains increasing importance because there is a growing need to precisely model also mid- and far-field wind farms wakes for development and planning of offshore wind farm clusters.

Farms, pastures and woodlands: the fine-scale distribution of Palearctic Culicoides spp. biting midges along an agro-ecological gradient.

Science.gov (United States)

Rigot, T; Drubbel, M Vercauteren; Delécolle, J-C; Gilbert, M

2013-03-01

The spatial epidemiology of Bluetongue virus (BTV) at the landscape level relates to the fine-scale distribution and dispersal capacities of its vectors, midges belonging to the genus Culicoides Latreille (Diptera: Ceratopogonidae). Although many previous researches have carried out Culicoides sampling on farms, little is known of the fine-scale distribution of Culicoides in the landscape immediately surrounding farms. The aim of this study was to gain a better understanding of Culicoides populations at increasing distances from typical dairy farms in north-west Europe, through the use of eight Onderstepoort-type black-light traps positioned along linear transects departing from farms, going through pastures and entering woodlands. A total of 16 902 Culicoides were collected in autumn 2008 and spring 2009. The majority were females, of which more than 97% were recognized as potential vectors. In pastures, we found decreasing numbers of female Culicoides as a function of the distance to the farm. This pattern was modelled by leptokurtic models, with parameters depending on season and species. By contrast, the low number of male Culicoides caught were homogeneously distributed along the transects. When transects entered woodlands, we found a higher abundance of Culicoides than expected considering the distance of the sampling sites to the farm, although this varied according to species. © 2012 The Authors. Medical and Veterinary Entomology © 2012 The Royal Entomological Society.

Analysis of small-scale biogas utilization systems on Ontario cattle farms

International Nuclear Information System (INIS)

White, Andrew J.; Kirk, Donald W.; Graydon, John W.

2011-01-01

The production of biogas through the anaerobic digestion of cattle manure and its subsequent use in the generation of electricity on larger farms in Ontario is currently economically attractive. This is a result of the Ontario Feed-In Tariff (FIT) program, which provides incentivized rates for the production of electricity from biogas. Although larger farms can take advantage of the higher rates for electricity, there are substantially more smaller farms for which individually designed and engineered biogas systems would be prohibitively expensive. By employing the concept of modular biogas plants, this analysis evaluates the economics of small-scale biogas utilization systems. Dairy farms with at least 33 animals and beef farms with at least 78 animals can operate economically attractive biogas systems. This analysis shows that approximately 9000 additional Ontario cattle farms would be able to take advantage of the FIT program, which would add 120 MW e of renewable energy capacity to the Ontario electrical grid. (author)

Environmental consequence analyses of fish farm emissions related to different scales and exemplified by data from the Baltic--a review.

Science.gov (United States)

Gyllenhammar, Andreas; Håkanson, Lars

2005-08-01

The aim of this work is to review studies to evaluate how emissions from fish cage farms cause eutrophication effects in marine environments. The focus is on four different scales: (i) the conditions at the site of the farm, (ii) the local scale related to the coastal area where the farm is situated, (iii) the regional scale encompassing many coastal areas and (iv) the international scale including several regional coastal areas. The aim is to evaluate the role of nutrient emissions from fish farms in a general way, but all selected examples come from the Baltic Sea. An important part of this evaluation concerns the method to define the boundaries of a given coastal area. If this is done arbitrarily, one would obtain arbitrary results in the environmental consequence analysis. In this work, the boundary lines between the coast and the sea are drawn using GIS methods (geographical information systems) according to the topographical bottleneck method, which opens a way to determine many fundamental characteristics in the context of mass balance calculations. In mass balance modelling, the fluxes from the fish farm should be compared to other fluxes to, within and from coastal areas. Results collected in this study show that: (1) at the smallest scale (impact areas of fish cage farm often corresponds to the size of a "football field" (50-100 m) if the annual fish production is about 50 ton, (2) at the local scale (1 ha to 100 km2), there exists a simple load diagram (effect-load-sensitivity) to relate the environmental response and effects from a specific load from a fish cage farm. This makes it possible to obtain a first estimate of the maximum allowable fish production in a specific coastal area, (3) at the regional scale (100-10,000 km2), it is possible to create negative nutrient fluxes, i.e., use fish farming as a method to reduce the nutrient loading to the sea. The breaking point is to use more than about 1.1 g wet weight regionally caught wild fish per gram

Integrating Agent Models of Subsistence Farming With Dynamic Models of Water Distribution

Science.gov (United States)

Bithell, M.; Brasington, J.

2004-12-01

Subsistence farming communities are dependent on the landscape to provide the resource base upon which their societies can be built. A key component of this is the role of climate, and the feedback between rainfall, crop growth and land clearance, and their coupling to the hydrological cycle. Temporal fluctuations in rainfall on timescales from annual through to decadal and longer, and the associated changes in in the spatial distribution of water availability mediated by the soil-type, slope and landcover determine the locations within the landscape that can support agriculture, and control sustainability of farming practices. We seek to make an integrated modelling system to represent land use change by coupling an agent based model of subsistence farming, and the associated exploitation of natural resources, to a realistic representation of the hydrology at the catchment scale, using TOPMODEL to map the spatial distribution of crop water stress for given time-series of rainfall. In this way we can, for example, investigate how demographic changes and associated removal of forest cover influence the possibilities for field locations within the catchment, through changes in ground water availability. The framework for this modelling exercise will be presented and preliminary results from this system will be discussed.

Wind-Farm Parametrisations in Mesoscale Models

DEFF Research Database (Denmark)

Volker, Patrick; Badger, Jake; Hahmann, Andrea N.

2013-01-01

In this paper we compare three wind-farm parametrisations for mesoscale models against measurement data from the Horns Rev I offshore wind-farm. The parametrisations vary from a simple rotor drag method, to more sophisticated models. Additional to (4) we investigated the horizontal resolution dep...

Risk management strategies on small-scale commercial farms in three zobatat of Eritrea

Directory of Open Access Journals (Sweden)

MA Mohammed

2014-05-01

Full Text Available In this study the perceptions of small-scale commercial farmers in Eritrea of the importance of various risk responses are ascertained and analysed to gain insight into their risk-management strategies.  Data were elicited through a survey of 186 small-scale commercial farmers conducted in three zobatat (regions of Eritrea. Factor Analysis is used to investigate heterogeneity in sample farmers’ responses.  Results indicate that relatively more important risk responses include the use of internal and external sources of information, on-farm and off-farm diversification, choice of production system and product marketing arrangements. Farmers’ perceptions of risk responses vary according to farm type, geographical location, farm and farmer characteristics, as well as the existence of enterprise specific risk responses (e.g. livestock insurance and differences in the marketing regulations of various agricultural products.

Processor farming method for multi-scale analysis of masonry structures

Science.gov (United States)

Krejčí, Tomáš; Koudelka, Tomáš

2017-07-01

This paper describes a processor farming method for a coupled heat and moisture transport in masonry using a two-level approach. The motivation for the two-level description comes from difficulties connected with masonry structures, where the size of stone blocks is much larger than the size of mortar layers and very fine finite element mesh has to be used. The two-level approach is suitable for parallel computing because nearly all computations can be performed independently with little synchronization. This approach is called processor farming. The master processor is dealing with the macro-scale level - the structure and the slave processors are dealing with a homogenization procedure on the meso-scale level which is represented by an appropriate representative volume element.

Modelling farm vulnerability to flooding: A step toward vulnerability mitigation policies appraisal

Science.gov (United States)

Brémond, P.; Abrami, G.; Blanc, C.; Grelot, F.

2009-04-01

flood. In the case of farm activities, vulnerability mitigation consists in implementing measures which can be: physical (equipment or electric power system elevation), organizational (emergency or recovery plan) or financial (insurance). These measures aim at decreasing the total damage incurred by farmers in case of flooding. For instance, if equipment is elevated, it will not suffer direct damage such as degradation. As a consequence, equipment will be available to continue production or recovery tasks, thus, avoiding indirect damage such as delays, indebtedness… The effects of these policies on farms, in particular vulnerability mitigation cannot be appraised using current methodologies mainly because they do not consider farm as a whole and focus on direct damage at the land plot scale (loss of yield). Moreover, since vulnerability mitigation policies are quite recent, few examples of implementation exist and no feedback experience can be processed. Meanwhile, decision makers and financial actors require more justification of the efficiency of public fund by economic appraisal of the projects. On the Rhône River, decision makers asked for an economic evaluation of the program of farm vulnerability mitigation they plan to implement. This implies to identify the effects of the measures to mitigate farm vulnerability, and to classify them by comparing their efficacy (avoided damage) and their cost of implementation. In this presentation, we propose and discuss a conceptual model of vulnerability at the farm scale. The modelling, in Unified Modelling Language, enabled to represent the ties between spatial, organizational and temporal dimensions, which are central to understanding of farm vulnerability and resilience to flooding. Through this modelling, we encompass three goals: To improve the comprehension of farm vulnerability and create a framework that allow discussion with experts of different disciplines as well as with local farmers; To identify data which

Dairy Wise, A Whole-Farm Dairy Model

NARCIS (Netherlands)

Schils, R.L.M.; Haan, de M.H.A.; Hemmer, J.G.A.; Pol, van den A.; Boer, de J.A.; Evers, A.G.; Holshof, G.; Middelkoop, van J.C.; Zom, R.L.G.

2007-01-01

A whole-farm dairy model was developed and evaluated. The DairyWise model is an empirical model that simulated technical, environmental, and financial processes on a dairy farm. The central component is the FeedSupply model that balanced the herd requirements, as generated by the DairyHerd model,

IEA-Task 31 WAKEBENCH: Towards a protocol for wind farm flow model evaluation. Part 2: Wind farm wake models

Science.gov (United States)

Moriarty, Patrick; Sanz Rodrigo, Javier; Gancarski, Pawel; Chuchfield, Matthew; Naughton, Jonathan W.; Hansen, Kurt S.; Machefaux, Ewan; Maguire, Eoghan; Castellani, Francesco; Terzi, Ludovico; Breton, Simon-Philippe; Ueda, Yuko

2014-06-01

Researchers within the International Energy Agency (IEA) Task 31: Wakebench have created a framework for the evaluation of wind farm flow models operating at the microscale level. The framework consists of a model evaluation protocol integrated with a web-based portal for model benchmarking (www.windbench.net). This paper provides an overview of the building-block validation approach applied to wind farm wake models, including best practices for the benchmarking and data processing procedures for validation datasets from wind farm SCADA and meteorological databases. A hierarchy of test cases has been proposed for wake model evaluation, from similarity theory of the axisymmetric wake and idealized infinite wind farm, to single-wake wind tunnel (UMN-EPFL) and field experiments (Sexbierum), to wind farm arrays in offshore (Horns Rev, Lillgrund) and complex terrain conditions (San Gregorio). A summary of results from the axisymmetric wake, Sexbierum, Horns Rev and Lillgrund benchmarks are used to discuss the state-of-the-art of wake model validation and highlight the most relevant issues for future development.

IEA-Task 31 WAKEBENCH: Towards a protocol for wind farm flow model evaluation. Part 2: Wind farm wake models

International Nuclear Information System (INIS)

Moriarty, Patrick; Rodrigo, Javier Sanz; Gancarski, Pawel; Chuchfield, Matthew; Naughton, Jonathan W; Hansen, Kurt S; Machefaux, Ewan; Maguire, Eoghan; Castellani, Francesco; Terzi, Ludovico; Breton, Simon-Philippe; Ueda, Yuko

2014-01-01

Researchers within the International Energy Agency (IEA) Task 31: Wakebench have created a framework for the evaluation of wind farm flow models operating at the microscale level. The framework consists of a model evaluation protocol integrated with a web-based portal for model benchmarking (www.windbench.net). This paper provides an overview of the building-block validation approach applied to wind farm wake models, including best practices for the benchmarking and data processing procedures for validation datasets from wind farm SCADA and meteorological databases. A hierarchy of test cases has been proposed for wake model evaluation, from similarity theory of the axisymmetric wake and idealized infinite wind farm, to single-wake wind tunnel (UMN-EPFL) and field experiments (Sexbierum), to wind farm arrays in offshore (Horns Rev, Lillgrund) and complex terrain conditions (San Gregorio). A summary of results from the axisymmetric wake, Sexbierum, Horns Rev and Lillgrund benchmarks are used to discuss the state-of-the-art of wake model validation and highlight the most relevant issues for future development

SWEET CORN FARMING: THE EFFECT OF PRODUCTION FACTOR, EFFICIENCY AND RETURN TO SCALE

Directory of Open Access Journals (Sweden)

Dwijatenaya I.B.M.A.

2017-10-01

Full Text Available This research aims to determine the effect of production factors on the sweet corn production, the efficiency of sweet corn farming, and the return to scale of sweet corn production. The sampling technique was taken by proportionate stratified random sampling method with the sample number of 57 people while the analyzer used was the program of Frointer 4.1c. The results show that the production factors of the land farm, seed, and fertilizer have a positive and significant effect on sweet corn production. On the other hand, labor production factors have a positive but not significant effect on sweet corn production. It also found that technical efficiency, price efficiency, and economic efficiency of sweet corn farming in Muara Wis Sub-district of Kutai Kartanegara Regency are not efficient yet. The return to scale of sweet corn yield has an increasing return to scale condition.

Are large farms more efficient? Tenure security, farm size and farm efficiency: evidence from northeast China

Science.gov (United States)

Zhou, Yuepeng; Ma, Xianlei; Shi, Xiaoping

2017-04-01

How to increase production efficiency, guarantee grain security, and increase farmers' income using the limited farmland is a great challenge that China is facing. Although theory predicts that secure property rights and moderate scale management of farmland can increase land productivity, reduce farm-related costs, and raise farmer's income, empirical studies on the size and magnitude of these effects are scarce. A number of studies have examined the impacts of land tenure or farm size on productivity or efficiency, respectively. There are also a few studies linking farm size, land tenure and efficiency together. However, to our best knowledge, there are no studies considering tenure security and farm efficiency together for different farm scales in China. In addition, there is little study analyzing the profit frontier. In this study, we particularly focus on the impacts of land tenure security and farm size on farm profit efficiency, using farm level data collected from 23 villages, 811 households in Liaoning in 2015. 7 different farm scales have been identified to further represent small farms, median farms, moderate-scale farms, and large farms. Technical efficiency is analyzed with stochastic frontier production function. The profit efficiency is regressed on a set of explanatory variables which includes farm size dummies, land tenure security indexes, and household characteristics. We found that: 1) The technical efficiency scores for production efficiency (average score = 0.998) indicate that it is already very close to the production frontier, and thus there is little room to improve production efficiency. However, there is larger space to raise profit efficiency (average score = 0.768) by investing more on farm size expansion, seed, hired labor, pesticide, and irrigation. 2) Farms between 50-80 mu are most efficient from the viewpoint of profit efficiency. The so-called moderate-scale farms (100-150 mu) according to the governmental guideline show no

IEA-Task 31 WAKEBENCH: Towards a protocol for wind farm flow model evaluation. Part 2: Wind farm wake models

DEFF Research Database (Denmark)

Moriarty, Patrick; Rodrigo, Javier Sanz; Gancarski, Pawel

2014-01-01

Researchers within the International Energy Agency (IEA) Task 31: Wakebench have created a framework for the evaluation of wind farm flow models operating at the microscale level. The framework consists of a model evaluation protocol integrated with a web-based portal for model benchmarking (www.......windbench.net). This paper provides an overview of the building-block validation approach applied to wind farm wake models, including best practices for the benchmarking and data processing procedures for validation datasets from wind farm SCADA and meteorological databases. A hierarchy of test cases has been proposed...

Fuel from farms: a guide to small-scale ethanol production

Energy Technology Data Exchange (ETDEWEB)

None

1980-02-01

A guide on fermentation processes with emphasis on small-scale production of ethanol using farm crops as a source of raw material is published. The current status of on-farm ethanol production as well as an overview of some of the technical and economic factors is presented. Decision and planning worksheets and a sample business plan for use in decision making are included. Specifics in production including information on the raw materials, system components, and operational requirements are also provided. Diagrams of fermentors and distilling apparatus are included. (DC)

Multi-time scale energy management of wind farms based on comprehensive evaluation technology

Science.gov (United States)

Xu, Y. P.; Huang, Y. H.; Liu, Z. J.; Wang, Y. F.; Li, Z. Y.; Guo, L.

2017-11-01

A novel energy management of wind farms is proposed in this paper. Firstly, a novel comprehensive evaluation system is proposed to quantify economic properties of each wind farm to make the energy management more economical and reasonable. Then, a combination of multi time-scale schedule method is proposed to develop a novel energy management. The day-ahead schedule optimizes unit commitment of thermal power generators. The intraday schedule is established to optimize power generation plan for all thermal power generating units, hydroelectric generating sets and wind power plants. At last, the power generation plan can be timely revised in the process of on-line schedule. The paper concludes with simulations conducted on a real provincial integrated energy system in northeast China. Simulation results have validated the proposed model and corresponding solving algorithms.

Wind Farms: Modeling and Control

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam

2012-01-01

is minimized. The controller is practically feasible. Yet, the results on load reduction in this approach are not very significant. In the second strategy, the wind farm control problem has been divided into below rated and above rated wind speed conditions. In the above rated wind speed pitch angle and power....... Distributed controller design commences with formulating the problem, where a structured matrix approach has been put in to practice. Afterwards, an H2 control problem is implemented to obtain the controller dynamics for a wind farm such that the structural loads on wind turbines are minimized.......The primary purpose of this work is to develop control algorithms for wind farms to optimize the power production and augment the lifetime of wind turbines in wind farms. In this regard, a dynamical model for wind farms was required to be the basis of the controller design. In the first stage...

Wind farms providing secondary frequency regulation: Evaluating the performance of model-based receding horizon control

International Nuclear Information System (INIS)

Shapiro, Carl R.; Meneveau, Charles; Gayme, Dennice F.; Meyers, Johan

2016-01-01

We investigate the use of wind farms to provide secondary frequency regulation for a power grid. Our approach uses model-based receding horizon control of a wind farm that is tested using a large eddy simulation (LES) framework. In order to enable real-time implementation, the control actions are computed based on a time-varying one-dimensional wake model. This model describes wake advection and interactions, both of which play an important role in wind farm power production. This controller is implemented in an LES model of an 84-turbine wind farm represented by actuator disk turbine models. Differences between the velocities at each turbine predicted by the wake model and measured in LES are used for closed-loop feedback. The controller is tested on two types of regulation signals, “RegA” and “RegD”, obtained from PJM, an independent system operator in the eastern United States. Composite performance scores, which are used by PJM to qualify plants for regulation, are used to evaluate the performance of the controlled wind farm. Our results demonstrate that the controlled wind farm consistently performs well, passing the qualification threshold for all fastacting RegD signals. For the RegA signal, which changes over slower time scales, the controlled wind farm's average performance surpasses the threshold, but further work is needed to enable the controlled system to achieve qualifying performance all of the time. (paper)

Fate and occurrence of steroids in swine and dairy cattle farms with different farming scales and wastes disposal systems

International Nuclear Information System (INIS)

Liu Shan; Ying Guangguo; Zhang Ruiquan; Zhou Lijun; Lai Huajie; Chen Zhifeng

2012-01-01

Fate and occurrence of fourteen androgens, four estrogens, five glucocorticoids and five progestagens were investigated in three swine farms and three dairy cattle farms with different farming scales and wastes disposal systems in China. Twenty-one, 22, and 12 of total 28 steroids were detected in feces samples with concentrations ranging from below method limit of quantitation (< LOQ for estrone) to 8100 ± 444 ng/g (progesterone), in wastewater samples with concentrations ranging from < LOQ (estrone) to 20,700 ± 1490 ng/L (androsterone), in suspended particles with concentrations ranging from < LOQ (17β-trenbolone) to 778 ± 82.1 ng/g (5α-dihydrotestosterone) in the six farms, respectively. The steroids via swine farms and human sources were mainly originated from wastewater into the receiving environments while those steroids via cattle farms were mainly from cattle feces. The total contributions of steroids to the environment in China are estimated to be 139, 65.8 and 60.7 t/year from swine, dairy cattle and human sources, respectively. - Highlights: ► 28 steroids were investigated in three swine farms and three cattle farms. ► Eight detected synthetic steroids were from exogenous usage. ► Lagoon systems were more effective in removing steroids than sedimentation tanks. ► The steroids via swine and human sources were mainly from wastewater. ► The steroids via cattle were mainly originated from feces. - The swine and cattle farms contribute higher steroids masses to the environment than the human sources.

Wind Speed Estimation and Parametrization of Wake Models for Downregulated Offshore Wind Farms within the scope of PossPOW Project

DEFF Research Database (Denmark)

Göçmen Bozkurt, Tuhfe; Giebel, Gregor; Poulsen, Niels Kjølstad

2014-01-01

With increasing installed capacity, wind farms are requested to downregulate more frequently, especially in the offshore environment. Determination and verification of possible (or available) power of downregulated offshore wind farms are the aims of the PossPOW project (see PossPOW.dtu.dk). Two ...... period. The re-calibrated model has to be further parametrized to include dynamic effects such as wind direction variability and meandering also considering different averaging time scales before implemented in full scale wind farms....

Large-Eddy Simulation of Waked Turbines in a Scaled Wind Farm Facility

Science.gov (United States)

Wang, J.; McLean, D.; Campagnolo, F.; Yu, T.; Bottasso, C. L.

2017-05-01

The aim of this paper is to present the numerical simulation of waked scaled wind turbines operating in a boundary layer wind tunnel. The simulation uses a LES-lifting-line numerical model. An immersed boundary method in conjunction with an adequate wall model is used to represent the effects of both the wind turbine nacelle and tower, which are shown to have a considerable effect on the wake behavior. Multi-airfoil data calibrated at different Reynolds numbers are used to account for the lift and drag characteristics at the low and varying Reynolds conditions encountered in the experiments. The present study focuses on low turbulence inflow conditions and inflow non-uniformity due to wind tunnel characteristics, while higher turbulence conditions are considered in a separate study. The numerical model is validated by using experimental data obtained during test campaigns conducted with the scaled wind farm facility. The simulation and experimental results are compared in terms of power capture, rotor thrust, downstream velocity profiles and turbulence intensity.

On wake modeling, wind-farm gradients, and AEP predictions at the Anholt wind farm

Directory of Open Access Journals (Sweden)

A. Peña

2018-04-01

Full Text Available We investigate wake effects at the Anholt offshore wind farm in Denmark, which is a farm experiencing strong horizontal wind-speed gradients because of its size and proximity to land. Mesoscale model simulations are used to study the horizontal wind-speed gradients over the wind farm. From analysis of the mesoscale simulations and supervisory control and data acquisition (SCADA, we show that for westerly flow in particular, there is a clear horizontal wind-speed gradient over the wind farm. We also use the mesoscale simulations to derive the undisturbed inflow conditions that are coupled with three commonly used wake models: two engineering approaches (the Park and G. C. Larsen models and a linearized Reynolds-averaged Navier–Stokes approach (Fuga. The effect of the horizontal wind-speed gradient on annual energy production estimates is not found to be critical compared to estimates from both the average undisturbed wind climate of all turbines' positions and the undisturbed wind climate of a position in the middle of the wind farm. However, annual energy production estimates can largely differ when using wind climates at positions that are strongly influenced by the horizontal wind-speed gradient. When looking at westerly flow wake cases, where the impact of the horizontal wind-speed gradient on the power of the undisturbed turbines is largest, the wake models agree with the SCADA fairly well; when looking at a southerly flow case, where the wake losses are highest, the wake models tend to underestimate the wake loss. With the mesoscale-wake model setup, we are also able to estimate the capacity factor of the wind farm rather well when compared to that derived from the SCADA. Finally, we estimate the uncertainty of the wake models by bootstrapping the SCADA. The models tend to underestimate the wake losses (the median relative model error is 8.75 % and the engineering wake models are as uncertain as Fuga. These results are specific for

Empirical Analysis of Farm Credit Risk under the Structure Model

Science.gov (United States)

Yan, Yan

2009-01-01

The study measures farm credit risk by using farm records collected by Farm Business Farm Management (FBFM) during the period 1995-2004. The study addresses the following questions: (1) whether farm's financial position is fully described by the structure model, (2) what are the determinants of farm capital structure under the structure model, (3)…

Wind speed dynamical model in a wind farm

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam; Wisniewski, Rafal

2010-01-01

, the dynamic model for wind flow will be established. The state space variables are determined based on a fine mesh defined for the farm. The end goal of this method is to assist the development of a dynamical model of a wind farm that can be engaged for better wind farm control strategies....

Wind Farm Decentralized Dynamic Modeling With Parameters

DEFF Research Database (Denmark)

Soltani, Mohsen; Shakeri, Sayyed Mojtaba; Grunnet, Jacob Deleuran

2010-01-01

Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...... local models. The results of this report are especially useful, but not limited, to design a decentralized wind farm controller, since in centralized controller design one can also use the model and update it in a central computing node.......Development of dynamic wind flow models for wind farms is part of the research in European research FP7 project AEOLUS. The objective of this report is to provide decentralized dynamic wind flow models with parameters. The report presents a structure for decentralized flow models with inputs from...

How do farm models compare when estimating greenhouse gas emissions from dairy cattle production?

DEFF Research Database (Denmark)

Hutchings, Nicholas John; Özkan, Şeyda; de Haan, M

2018-01-01

The European Union Effort Sharing Regulation (ESR) will require a 30% reduction in greenhouse gas (GHG) emissions by 2030 compared with 2005 from the sectors not included in the European Emissions Trading Scheme, including agriculture. This will require the estimation of current and future...... from four farm-scale models (DairyWise, FarmAC, HolosNor and SFARMMOD) were calculated for eight dairy farming scenarios within a factorial design consisting of two climates (cool/dry and warm/wet)×two soil types (sandy and clayey)×two feeding systems (grass only and grass/maize). The milk yield per...

An LP-model to analyse economic and ecological sustainability on Dutch dairy farms: model presentation and application for experimental farm "de Marke"

NARCIS (Netherlands)

Calker, van K.J.; Berentsen, P.B.M.; Boer, de I.J.M.; Giesen, G.W.J.; Huirne, R.B.M.

2004-01-01

Farm level modelling can be used to determine how farm management adjustments and environmental policy affect different sustainability indicators. In this paper indicators were included in a dairy farm LP (linear programming)-model to analyse the effects of environmental policy and management

Assessing the Economic Situation of Small-Scale Farm Forestry in Mountain Regions: A Case Study in Austria

Directory of Open Access Journals (Sweden)

Philipp Toscani

2017-08-01

Full Text Available Austria is one of the few countries with a long tradition of monitoring the economic performance of forest holdings. The national Farm Accountancy Data Network also addresses some forestry-specific issues, given the high significance of farm forestry in this country. However, it is not possible to assess the profitability of small-scale farm forestry in mountainous regions based on a representative sample. In this paper, we demonstrate how information gaps can be overcome by means of economic modeling and present results of this approach for mountain forestry for the first time. In spite of the unfavorable conditions of an alpine setting, forestry tends to be of special significance for the viability and resilience of family farms in these regions. Sustainable forest management that safeguards the ecosystem services provided by forests relies mostly on the profitability of timber production. Thus, the economic development of farm forestry is a key factor in achieving targets 15.1 and 15.4 of the United Nations Sustainable Development Goals in mountain regions.

Farm scale biogas concepts in Europe

Energy Technology Data Exchange (ETDEWEB)

Wellinger, A [Nova Energie, Ettenhausen (Switzerland)

1997-08-01

The near future of farm scale biogas production looks bright as long as the high electricity prices are maintained by political will and subsidies remain higher than approx. 20%. If in all the number of biogas plants is growing as it is in Germany (Within the last two years about 200 new plants have been built) then biogas will add its share to a nuclear power free electricity production, as does wind energy in Germany, Holland or Denmark. The standard for manure digesters is set. There is still some way to go for solid waste digesters. However, first inputs have been given. (EG) 10 refs.

Economic and agricultural transformation through large-scale farming : impacts of large-scale farming on local economic development, household food security and the environment in Ethiopia

NARCIS (Netherlands)

Bekele, M.S.

2016-01-01

This study examined impacts of large-scale farming in Ethiopia on local economic development, household food security, incomes, employment, and the environment. The study adopted a mixed research approach in which both qualitative and quantitative data were generated from secondary and primary

Monitoring, modeling and mitigating impacts of wind farms on local meteorology

Science.gov (United States)

Baidya Roy, Somnath; Traiteur, Justin; Kelley, Neil

2010-05-01

Wind power is one of the fastest growing sources of energy. Most of the growth is in the industrial sector comprising of large utility-scale wind farms. Recent modeling studies have suggested that such wind farms can significantly affect local and regional weather and climate. In this work, we present observational evidence of the impact of wind farms on near-surface air temperatures. Data from perhaps the only meteorological field campaign in an operational wind farm shows that downwind temperatures are lower during the daytime and higher at night compared to the upwind environment. Corresponding radiosonde profiles at the nearby Edwards Air Force Base WMO meteorological station show that the diurnal environment is unstable while the nocturnal environment is stable during the field campaign. This behavior is consistent with the hypothesis proposed by Baidya Roy et al. (JGR 2004) that states that turbulence generated in the wake of rotors enhance vertical mixing leading to a warming/cooling under positive/negative potential temperature lapse rates. We conducted a set of 306 simulations with the Regional Atmospheric Modeling System (RAMS) to test if regional climate models can capture the thermal effects of wind farms. We represented wind turbines with a subgrid parameterization that assumes rotors to be sinks of momentum and sources of turbulence. The simulated wind farms consistently generated a localized warming/cooling under positive/negative lapse rates as hypothesized. We found that these impacts are inversely correlated with background atmospheric boundary layer turbulence. Thus, if the background turbulence is high due to natural processes, the effects of additional turbulence generated by wind turbine rotors are likely to be small. We propose the following strategies to minimize impacts of wind farms: • Engineering solution: design rotors that generate less turbulence in their wakes. Sensitivity simulations show that these turbines also increase the

Occurrence of Eimeria species parasites on small-scale commercial chicken farms in Africa and indication of economic profitability.

Directory of Open Access Journals (Sweden)

Kimberly M Fornace

Full Text Available Small-scale commercial poultry production is emerging as an important form of livestock production in Africa, providing sources of income and animal protein to many poor households, yet the occurrence and impact of coccidiosis on this relatively new production system remains unknown. The primary objective of this study was to examine Eimeria parasite occurrence on small-scale commercial poultry farms in Ghana, Tanzania and Zambia. Additionally, farm economic viability was measured by calculating the farm gross margin and enterprise budget. Using these economic measures as global assessments of farm productivity, encompassing the diversity present in regional husbandry systems with a measure of fundamental local relevance, we investigated the detection of specific Eimeria species as indicators of farm profitability. Faecal samples and data on production parameters were collected from small-scale (less than 2,000 birds per batch intensive broiler and layer farms in peri-urban Ghana, Tanzania and Zambia. All seven Eimeria species recognised to infect the chicken were detected in each country. Furthermore, two of the three genetic variants (operational taxonomic units identified previously in Australia have been described outside of Australia for the first time. Detection of the most pathogenic Eimeria species associated with decreased farm profitability and may be considered as an indicator of likely farm performance. While a causal link remains to be demonstrated, the presence of highly pathogenic enteric parasites may pose a threat to profitable, sustainable small-scale poultry enterprises in Africa.

Occurrence of Eimeria Species Parasites on Small-Scale Commercial Chicken Farms in Africa and Indication of Economic Profitability

Science.gov (United States)

Fornace, Kimberly M.; Clark, Emily L.; Macdonald, Sarah E.; Namangala, Boniface; Karimuribo, Esron; Awuni, Joseph A.; Thieme, Olaf; Blake, Damer P.; Rushton, Jonathan

2013-01-01

Small-scale commercial poultry production is emerging as an important form of livestock production in Africa, providing sources of income and animal protein to many poor households, yet the occurrence and impact of coccidiosis on this relatively new production system remains unknown. The primary objective of this study was to examine Eimeria parasite occurrence on small-scale commercial poultry farms in Ghana, Tanzania and Zambia. Additionally, farm economic viability was measured by calculating the farm gross margin and enterprise budget. Using these economic measures as global assessments of farm productivity, encompassing the diversity present in regional husbandry systems with a measure of fundamental local relevance, we investigated the detection of specific Eimeria species as indicators of farm profitability. Faecal samples and data on production parameters were collected from small-scale (less than 2,000 birds per batch) intensive broiler and layer farms in peri-urban Ghana, Tanzania and Zambia. All seven Eimeria species recognised to infect the chicken were detected in each country. Furthermore, two of the three genetic variants (operational taxonomic units) identified previously in Australia have been described outside of Australia for the first time. Detection of the most pathogenic Eimeria species associated with decreased farm profitability and may be considered as an indicator of likely farm performance. While a causal link remains to be demonstrated, the presence of highly pathogenic enteric parasites may pose a threat to profitable, sustainable small-scale poultry enterprises in Africa. PMID:24391923

Occurrence of Eimeria species parasites on small-scale commercial chicken farms in Africa and indication of economic profitability.

Science.gov (United States)

Fornace, Kimberly M; Clark, Emily L; Macdonald, Sarah E; Namangala, Boniface; Karimuribo, Esron; Awuni, Joseph A; Thieme, Olaf; Blake, Damer P; Rushton, Jonathan

2013-01-01

Small-scale commercial poultry production is emerging as an important form of livestock production in Africa, providing sources of income and animal protein to many poor households, yet the occurrence and impact of coccidiosis on this relatively new production system remains unknown. The primary objective of this study was to examine Eimeria parasite occurrence on small-scale commercial poultry farms in Ghana, Tanzania and Zambia. Additionally, farm economic viability was measured by calculating the farm gross margin and enterprise budget. Using these economic measures as global assessments of farm productivity, encompassing the diversity present in regional husbandry systems with a measure of fundamental local relevance, we investigated the detection of specific Eimeria species as indicators of farm profitability. Faecal samples and data on production parameters were collected from small-scale (less than 2,000 birds per batch) intensive broiler and layer farms in peri-urban Ghana, Tanzania and Zambia. All seven Eimeria species recognised to infect the chicken were detected in each country. Furthermore, two of the three genetic variants (operational taxonomic units) identified previously in Australia have been described outside of Australia for the first time. Detection of the most pathogenic Eimeria species associated with decreased farm profitability and may be considered as an indicator of likely farm performance. While a causal link remains to be demonstrated, the presence of highly pathogenic enteric parasites may pose a threat to profitable, sustainable small-scale poultry enterprises in Africa.

Efficiency of Estonian grain farms in 2000 2004

Directory of Open Access Journals (Sweden)

N. VASILIEV

2008-12-01

Full Text Available The aim of this study is to analyse the efficiency of Estonian grain farms after Estonia’s transition to a market economy and during the accession period to the European Union (EU. The non-parametric method Data Envelopment Analysis (DEA was used to estimate the total technical, pure technical and scale efficiency of Estonian grain farms in 2000–2004. Mean total technical efficiency varied from 0.70 to 0.78. Of the grain farms 62% are operating under increasing returns to scale. Solely based on the DEA model it is not possible to determine optimum farm scale and the range of Estonian farm sizes operating efficiently is extensive. The most pure technically efficient farms were the smallest and the largest but the productivity of small farms is low compared to larger farms because of their small scale. Therefore, they are the least competitive. Since pre-accession period to the EU, large input slacks of capital have replaced the former excessive use of labour and land. This raises the question about the effects on efficiency of the EU’s investment support schemes in new member states.;

Accurate wind farm development and operation. Advanced wake modelling

Energy Technology Data Exchange (ETDEWEB)

Brand, A.; Bot, E.; Ozdemir, H. [ECN Unit Wind Energy, P.O. Box 1, NL 1755 ZG Petten (Netherlands); Steinfeld, G.; Drueke, S.; Schmidt, M. [ForWind, Center for Wind Energy Research, Carl von Ossietzky Universitaet Oldenburg, D-26129 Oldenburg (Germany); Mittelmeier, N. REpower Systems SE, D-22297 Hamburg (Germany))

2013-11-15

The ability is demonstrated to calculate wind farm wakes on the basis of ambient conditions that were calculated with an atmospheric model. Specifically, comparisons are described between predicted and observed ambient conditions, and between power predictions from three wind farm wake models and power measurements, for a single and a double wake situation. The comparisons are based on performance indicators and test criteria, with the objective to determine the percentage of predictions that fall within a given range about the observed value. The Alpha Ventus site is considered, which consists of a wind farm with the same name and the met mast FINO1. Data from the 6 REpower wind turbines and the FINO1 met mast were employed. The atmospheric model WRF predicted the ambient conditions at the location and the measurement heights of the FINO1 mast. May the predictability of the wind speed and the wind direction be reasonable if sufficiently sized tolerances are employed, it is fairly impossible to predict the ambient turbulence intensity and vertical shear. Three wind farm wake models predicted the individual turbine powers: FLaP-Jensen and FLaP-Ainslie from ForWind Oldenburg, and FarmFlow from ECN. The reliabilities of the FLaP-Ainslie and the FarmFlow wind farm wake models are of equal order, and higher than FLaP-Jensen. Any difference between the predictions from these models is most clear in the double wake situation. Here FarmFlow slightly outperforms FLaP-Ainslie.

Modeling livestock population structure: a geospatial database for Ontario swine farms.

Science.gov (United States)

Khan, Salah Uddin; O'Sullivan, Terri L; Poljak, Zvonimir; Alsop, Janet; Greer, Amy L

2018-01-30

Infectious diseases in farmed animals have economic, social, and health consequences. Foreign animal diseases (FAD) of swine are of significant concern. Mathematical and simulation models are often used to simulate FAD outbreaks and best practices for control. However, simulation outcomes are sensitive to the population structure used. Within Canada, access to individual swine farm population data with which to parameterize models is a challenge because of privacy concerns. Our objective was to develop a methodology to model the farmed swine population in Ontario, Canada that could represent the existing population structure and improve the efficacy of simulation models. We developed a swine population model based on the factors such as facilities supporting farm infrastructure, land availability, zoning and local regulations, and natural geographic barriers that could affect swine farming in Ontario. Assigned farm locations were equal to the swine farm density described in the 2011 Canadian Census of Agriculture. Farms were then randomly assigned to farm types proportional to the existing swine herd types. We compared the swine population models with a known database of swine farm locations in Ontario and found that the modeled population was representative of farm locations with a high accuracy (AUC: 0.91, Standard deviation: 0.02) suggesting that our algorithm generated a reasonable approximation of farm locations in Ontario. In the absence of a readily accessible dataset providing details of the relative locations of swine farms in Ontario, development of a model livestock population that captures key characteristics of the true population structure while protecting privacy concerns is an important methodological advancement. This methodology will be useful for individuals interested in modeling the spread of pathogens between farms across a landscape and using these models to evaluate disease control strategies.

A Response Surface-Based Cost Model for Wind Farm Design

International Nuclear Information System (INIS)

Zhang Jie; Chowdhury, Souma; Messac, Achille; Castillo, Luciano

2012-01-01

A Response Surface-Based Wind Farm Cost (RS-WFC) model is developed for the engineering planning of wind farms. The RS-WFC model is developed using Extended Radial Basis Functions (E-RBF) for onshore wind farms in the U.S. This model is then used to explore the influences of different design and economic parameters, including number of turbines, rotor diameter and labor cost, on the cost of a wind farm. The RS-WFC model is composed of three components that estimate the effects of engineering and economic factors on (i) the installation cost, (ii) the annual Operation and Maintenance (O and M) cost, and (iii) the total annual cost of a wind farm. The accuracy of the cost model is favorably established through comparison with pertinent commercial data. The final RS-WFC model provided interesting insights into cost variation with respect to critical engineering and economic parameters. In addition, a newly developed analytical wind farm engineering model is used to determine the power generated by the farm, and the subsequent Cost of Energy (COE). This COE is optimized for a unidirectional uniform “incoming wind speed” scenario using Particle Swarm Optimization (PSO). We found that the COE could be appreciably minimized through layout optimization, thereby yielding significant cost savings. - Highlights: ► We present a Response Surface-Based Wind Farm Cost (RS-WFC) model for wind farm design. ► The model could estimate installation cost, Operation and Maintenance cost, and total annual cost of a wind farm. ► The Cost of Energy is optimized using Particle Swarm Optimization. ► Layout optimization could yield significant cost savings.

Wind farm related mortality among avian migrants - a remote sensing study and model analysis

Energy Technology Data Exchange (ETDEWEB)

Desholm, M

2006-11-15

This thesis is the result of a PhD study on bird-wind farm collisions and consists of a synopsis, five published papers, one submitted manuscript and another ready for submission. The papers describe the findings from pre- and post-construction visual, radar and thermal imaging studies (1999-2006) of migrating birds at the Nysted offshore wind farm in the Baltic Sea, Denmark. This thesis poses and answers the following questions: a) what hazard factors do offshore wind farming pose to wild birds, b) how should one choose the key focal species to study, c) how can remote sensing techniques be applied to the study of bird wind farm interactions, and d) specifically, how do water birds react when approaching an offshore wind farm? The main aim of the study was the development of a predictive bird-wind farm collision model that incorporates the avoidance rate of birds at multiple scales. Out of 235,136 migrating sea ducks only 47 individuals were predicted to collide with the wind turbine rotor-blades, equivalent to an overall mean collision risk of c. 0.02%. This thesis shows the added value of modelling in supplementing sound empirical studies in accessing the effects of major human development pressures on migratory bird populations. (au)

Marine Model Trout Farms: developments in marine RAS

DEFF Research Database (Denmark)

Pedersen, Per Bovbjerg

2011-01-01

, nitrogen is removed in a full-scale experimental set-up where sludge from the drum filter is hydrolysed and the VFAs generated used as energy-source for the denitrification process in separate tanks/filters. Final polishing follows in a constructed wetland. For the first 2 years of operation production......Economical and environmentally sustainable production of large salmonids in sea water has in Denmark been called for during some years. Based on the experience gained from the Danish Model Trout Farms in freshwater, a rather similar concept has been developed for farming of larger fish in sea water...... temperature the pumps can be individually turned on/off primarily in relation to oxygen need and consumption in the fish tank. In a 1 year batch production some 20 t of fish will be introduced in April and some 80 t are supposed to be harvested in December. End-of-pipe treatment is a two-step process. First...

Dispersive stresses in wind farms

Science.gov (United States)

Segalini, Antonio; Braunbehrens, Robert; Hyvarinen, Ann

2017-11-01

One of the most famous models of wind farms is provided by the assumption that the farm can be approximated as a horizontally-homogeneous forest canopy with vertically-varying force intensity. By means of this approximation, the flow-motion equations become drastically simpler, as many of the three-dimensional effects are gone. However, the application of the horizontal average operator to the RANS equations leads to the appearance of new transport terms (called dispersive stresses) originating from the horizontal (small-scale) variation of the mean velocity field. Since these terms are related to the individual turbine signature, they are expected to vanish outside the roughness sublayer, providing a definition for the latter. In the present work, an assessment of the dispersive stresses is performed by means of a wake-model approach and through the linearised code ORFEUS developed at KTH. Both approaches are very fast and enable the characterization of a large number of wind-farm layouts. The dispersive stress tensor and its effect on the turbulence closure models are investigated, providing guidelines for those simulations where it is impossible to resolve the farm at a turbine scale due to grid requirements (as, for instance, mesoscale simulations).

Does limited data availability prevent adequate water use estimates on farm scale?

Science.gov (United States)

Kayatz, Benjamin; Kuster, Benjamin; Percy, Barbara; Hillier, Jonathan; Freese, Dirk; Wattenbach, Martin

2015-04-01

Increasing food production for a growing world population and at the same time mitigating climate change as well as adapting to its consequences is one of the key global challenges. Therefore producing crops with fewer resources such as water and fertilizers and less emissions of greenhouse gases is an important question that has to be answered on farm scale. The cool farm tool (CFT) is a farm scale emission calculator and was developed in 2010 to help farmers to reduce their carbon footprint. In order to adapt to future climate change an easy to use and at the same time robust water footprinting tool is needed for the CFT to take a more holistic approach on environmental sustainability. However data on farm level is often scarce. We investigated the effect of limited data on actual evapotranspiration using the FAO56 standard to assess the quality of farm water footprint estimates. Calculations are based on various agricultural sites from the Fluxnet database and estimates are compared to eddy covariance measurements. Results show that higher data availability is not directly linked to more accurate estimates of actual evapotranspiration. Estimates based only on temperature and relative humidity are still able to reproduce daily patterns. However cumulative values over one growing season show a considerable offset to eddy covariance observations for all data input levels. Finding the optimum between data requirements and an accuracy that fulfills farmer needs is crucial. Engagement of farmers and using a global network as the Fluxnet database will help to achieve this goal.

Automatic Installation and Configuration for Large Scale Farms

CERN Document Server

Novák, J

2005-01-01

Since the early appearance of commodity hardware, the utilization of computers rose rapidly, and they became essential in all areas of life. Soon it was realized that nodes are able to work cooperatively, in order to solve new, more complex tasks. This conception got materialized in coherent aggregations of computers called farms and clusters. Collective application of nodes, being efficient and economical, was adopted in education, research and industry before long. But maintainance, especially in large scale, appeared as a problem to be resolved. New challenges needed new methods and tools. Development work has been started to build farm management applications and frameworks. In the first part of the thesis, these systems are introduced. After a general description of the matter, a comparative analysis of different approaches and tools illustrates the practical aspects of the theoretical discussion. CERN, the European Organization of Nuclear Research is the largest Particle Physics laboratory in the world....

Metrics and methods for characterizing dairy farm intensification using farm survey data.

Science.gov (United States)

Gonzalez-Mejia, Alejandra; Styles, David; Wilson, Paul; Gibbons, James

2018-01-01

Evaluation of agricultural intensification requires comprehensive analysis of trends in farm performance across physical and socio-economic aspects, which may diverge across farm types. Typical reporting of economic indicators at sectorial or the "average farm" level does not represent farm diversity and provides limited insight into the sustainability of specific intensification pathways. Using farm business data from a total of 7281 farm survey observations of English and Welsh dairy farms over a 14-year period we calculate a time series of 16 key performance indicators (KPIs) pertinent to farm structure, environmental and socio-economic aspects of sustainability. We then apply principle component analysis and model-based clustering analysis to identify statistically the number of distinct dairy farm typologies for each year of study, and link these clusters through time using multidimensional scaling. Between 2001 and 2014, dairy farms have largely consolidated and specialized into two distinct clusters: more extensive farms relying predominantly on grass, with lower milk yields but higher labour intensity, and more intensive farms producing more milk per cow with more concentrate and more maize, but lower labour intensity. There is some indication that these clusters are converging as the extensive cluster is intensifying slightly faster than the intensive cluster, in terms of milk yield per cow and use of concentrate feed. In 2014, annual milk yields were 6,835 and 7,500 l/cow for extensive and intensive farm types, respectively, whilst annual concentrate feed use was 1.3 and 1.5 tonnes per cow. For several KPIs such as milk yield the mean trend across all farms differed substantially from the extensive and intensive typologies mean. The indicators and analysis methodology developed allows identification of distinct farm types and industry trends using readily available survey data. The identified groups allow the accurate evaluation of the consequences of the

Metrics and methods for characterizing dairy farm intensification using farm survey data.

Directory of Open Access Journals (Sweden)

Alejandra Gonzalez-Mejia

Full Text Available Evaluation of agricultural intensification requires comprehensive analysis of trends in farm performance across physical and socio-economic aspects, which may diverge across farm types. Typical reporting of economic indicators at sectorial or the "average farm" level does not represent farm diversity and provides limited insight into the sustainability of specific intensification pathways. Using farm business data from a total of 7281 farm survey observations of English and Welsh dairy farms over a 14-year period we calculate a time series of 16 key performance indicators (KPIs pertinent to farm structure, environmental and socio-economic aspects of sustainability. We then apply principle component analysis and model-based clustering analysis to identify statistically the number of distinct dairy farm typologies for each year of study, and link these clusters through time using multidimensional scaling. Between 2001 and 2014, dairy farms have largely consolidated and specialized into two distinct clusters: more extensive farms relying predominantly on grass, with lower milk yields but higher labour intensity, and more intensive farms producing more milk per cow with more concentrate and more maize, but lower labour intensity. There is some indication that these clusters are converging as the extensive cluster is intensifying slightly faster than the intensive cluster, in terms of milk yield per cow and use of concentrate feed. In 2014, annual milk yields were 6,835 and 7,500 l/cow for extensive and intensive farm types, respectively, whilst annual concentrate feed use was 1.3 and 1.5 tonnes per cow. For several KPIs such as milk yield the mean trend across all farms differed substantially from the extensive and intensive typologies mean. The indicators and analysis methodology developed allows identification of distinct farm types and industry trends using readily available survey data. The identified groups allow the accurate evaluation of the

Design tool for offshore wind farm cluster planning

DEFF Research Database (Denmark)

Hasager, Charlotte Bay; Madsen, Peter Hauge; Giebel, Gregor

2015-01-01

In the framework of the FP7 project EERA DTOC: Design Tool for Offshore wind farm Cluster, a new software supporting the planning of offshore wind farms was developed, based on state-of-the-art approaches from large scale wind potential to economic benchmarking. The model portfolio includes WAs......P, FUGA, WRF, Net-Op, LCoE model, CorWind, FarmFlow, EeFarm and grid code compliance calculations. The development is done by members from European Energy Research Alliance (EERA) and guided by several industrial partners. A commercial spin-off from the project is the tool ‘Wind & Economy’. The software...... by the software and several tests were performed. The calculations include the smoothing effect on produced energy between wind farms located in different regional wind zones and the short time scales relevant for assessing balancing power. The grid code compliance was tested for several cases and the results...

Effect of inter-annual variability in pasture growth and irrigation response on farm productivity and profitability based on biophysical and farm systems modelling.

Science.gov (United States)

Vogeler, Iris; Mackay, Alec; Vibart, Ronaldo; Rendel, John; Beautrais, Josef; Dennis, Samuel

2016-09-15

Farm system and nutrient budget models are increasingly being used in analysis to inform on farm decision making and evaluate land use policy options at regional scales. These analyses are generally based on the use of average annual pasture yields. In New Zealand (NZ), like in many countries, there is considerable inter-annual variation in pasture growth rates, due to climate. In this study a modelling approach was used to (i) include inter-annual variability as an integral part of the analysis and (ii) test the approach in an economic analysis of irrigation in a case study within the Hawkes Bay Region of New Zealand. The Agricultural Production Systems Simulator (APSIM) was used to generate pasture dry matter yields (DMY) for 20 different years and under both dryland and irrigation. The generated DMY were linked to outputs from farm-scale modelling for both Sheep and Beef Systems (Farmaxx Pro) and Dairy Systems (Farmax® Dairy Pro) to calculate farm production over 20 different years. Variation in DMY and associated livestock production due to inter-annual variation in climate was large, with a coefficient of variations up to 20%. Irrigation decreased this inter-annual variation. On average irrigation, with unlimited available water, increased income by $831 to 1195/ha, but when irrigation was limited to 250mm/ha/year income only increased by $525 to 883/ha. Using pasture responses in individual years to capturing the inter-annual variation, rather than the pasture response averaged over 20years resulted in lower financial benefits. In the case study income from irrigation based on an average year were 10 to >20% higher compared with those obtained from individual years. Copyright © 2016 Elsevier B.V. All rights reserved.

A model to predict the power output from wind farms

Energy Technology Data Exchange (ETDEWEB)

Landberg, L. [Riso National Lab., Roskilde (Denmark)

1997-12-31

This paper will describe a model that can predict the power output from wind farms. To give examples of input the model is applied to a wind farm in Texas. The predictions are generated from forecasts from the NGM model of NCEP. These predictions are made valid at individual sites (wind farms) by applying a matrix calculated by the sub-models of WASP (Wind Atlas Application and Analysis Program). The actual wind farm production is calculated using the Riso PARK model. Because of the preliminary nature of the results, they will not be given. However, similar results from Europe will be given.

Complete wind farm electromagnetic transient modelling for grid integration studies

International Nuclear Information System (INIS)

Zubia, I.; Ostolaza, X.; Susperregui, A.; Tapia, G.

2009-01-01

This paper presents a modelling methodology to analyse the impact of wind farms in surrounding networks. Based on the transient modelling of the asynchronous generator, the multi-machine model of a wind farm composed of N generators is developed. The model incorporates step-up power transformers, distribution lines and surrounding loads up to their connection to the power network. This model allows the simulation of symmetric and asymmetric short-circuits located in the distribution network and the analysis of transient stability of wind farms. It can be also used to study the islanding operation of wind farms

Wind model for low frequency power fluctuations in offshore wind farms

DEFF Research Database (Denmark)

Vigueras-Rodríguez, A.; Sørensen, Poul Ejnar; Cutululis, Nicolaos Antonio

2010-01-01

of hours, taking into account the spectral correlation between different wind turbines. The modelling is supported by measurements from two large wind farms, namely Nysted and Horns Rev. Measurements from individual wind turbines and meteorological masts are used. Finally, the models are integrated......This paper investigates the correlation between the frequency components of the wind speed Power Spectral Density. The results extend an already existing power fluctuation model that can simulate power fluctuations of wind power on areas up to several kilometers and for time scales up to a couple...

Evaluation model of wind energy resources and utilization efficiency of wind farm

Science.gov (United States)

Ma, Jie

2018-04-01

Due to the large amount of abandoned winds in wind farms, the establishment of a wind farm evaluation model is particularly important for the future development of wind farms In this essay, consider the wind farm's wind energy situation, Wind Energy Resource Model (WERM) and Wind Energy Utilization Efficiency Model(WEUEM) are established to conduct a comprehensive assessment of the wind farm. Wind Energy Resource Model (WERM) contains average wind speed, average wind power density and turbulence intensity, which assessed wind energy resources together. Based on our model, combined with the actual measurement data of a wind farm, calculate the indicators using the model, and the results are in line with the actual situation. We can plan the future development of the wind farm based on this result. Thus, the proposed establishment approach of wind farm assessment model has application value.

Small signal modeling of wind farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2017-01-01

-Input Multi-Output (MIMO) dynamic system, where the current control loops with Phase-Locked Loops (PLLs) are linearized around an operating point. Each sub-module of the wind farm is modeled as a 2×2 admittance matrix in dq-domain and all are combined together by using a dq nodal admittance matrix....... The frequency and damping of the oscillatory modes are calculated by finding the poles of the introduced MIMO matrix. Time-domain simulation results obtained from a 400-MW wind farm are used to verify the effectiveness of the presented model....

Wind farm models and control strategies

Energy Technology Data Exchange (ETDEWEB)

Soerensen, Poul; Hansen, Anca D.; Iov, F.; Blaabjerg, F.; Donovan, M.H.

2005-08-01

This report describes models and control strategies for 3 different concepts of wind farms. Initially, the potential in improvement of grid integration, structural loads and energy production is investigated in a survey of opportunities. Then simulation models are described, including wind turbine models for a fixed speed wind turbine with active stall control and a variable speed wind turbine with doubly-fed induction generator. After that, the 3 wind farm concepts and control strategies are described. The 3 concepts are AC connected doubly fed turbines, AC connected active stall turbines and DC connected active stall turbines. Finally, some simulation examples and conclusions are presented. (au)

Modeling needs assessment for Hanford Tank Farm Operations. Vadose Zone Characterization Project at the Hanford Tank Farms

International Nuclear Information System (INIS)

1996-04-01

This report presents the results of a modeling-needs assessment conducted for Tank Farm Operations at the Hanford Site. The goal of this project is to integrate geophysical logging and subsurface transport modeling into a broader decision-based framework that will be made available to guide Tank Farm Operations in implementing future modeling studies. In support of this goal, previous subsurface transport modeling studies were reviewed, and stakeholder surveys and interviews were completed (1) to identify regulatory, stakeholder, and Native American concerns and the impacts of these concerns on Tank Farm Operations, (2) to identify technical constraints that impact site characterization and modeling efforts, and (3) to assess how subsurface transport modeling can best be used to support regulatory, stakeholder, Native American, and Tank Farm Operations needs. This report is organized into six sections. Following an introduction, Section 2.0 discusses background issues that relate to Tank Farm Operations. Section 3.0 summarizes the technical approach used to appraise the status of modeling and supporting characterization. Section 4.0 presents a detailed description of how the technical approach was implemented. Section 5.0 identifies findings and observations that relate to implementation of numerical modeling, and Section 6.0 presents recommendations for future activities

Regional climate model simulations indicate limited climatic impacts by operational and planned European wind farms.

Science.gov (United States)

Vautard, Robert; Thais, Françoise; Tobin, Isabelle; Bréon, François-Marie; Devezeaux de Lavergne, Jean-Guy; Colette, Augustin; Yiou, Pascal; Ruti, Paolo Michele

2014-01-01

The rapid development of wind energy has raised concerns about environmental impacts. Temperature changes are found in the vicinity of wind farms and previous simulations have suggested that large-scale wind farms could alter regional climate. However, assessments of the effects of realistic wind power development scenarios at the scale of a continent are missing. Here we simulate the impacts of current and near-future wind energy production according to European Union energy and climate policies. We use a regional climate model describing the interactions between turbines and the atmosphere, and find limited impacts. A statistically significant signal is only found in winter, with changes within ±0.3 °C and within 0-5% for precipitation. It results from the combination of local wind farm effects and changes due to a weak, but robust, anticyclonic-induced circulation over Europe. However, the impacts remain much weaker than the natural climate interannual variability and changes expected from greenhouse gas emissions.

Agricultural Incentives: Implications for Small-Scale and Subsistence Farming in the US Caribbean Islands

Science.gov (United States)

Alvarez-Berrios, N.; Parés-Ramos, I.; Gould, W. A.

2017-12-01

The effects of climate change threaten the world's most sensitive agroecosystems and our potential to reach agricultural productivity levels needed to feed a projected global population of 9.7 billion people by 2050. The US Caribbean agriculture is especially vulnerable to the effects of climate change, due to the region's frequent exposure to extreme weather events, its geographic and economic scale, shortage of labor force, and rapid urban expansion. Currently, agriculture contributes less than 1% of the island's GDP, and over 80% of the food consumed in the region is imported. Despite low production levels, there is widespread interest in reinvigorating the agricultural sector's contribution to the economy. Local and federal institutions play a major role strengthening the agricultural sector by providing access to incentives, loans, and education for best management practices. However, many of these efforts conform to agricultural systems of larger scale of production and temperate environments. In this study, we explore agricultural incentives programs and their implication for highly diverse, small-scale, and subsistence operations that characterize agricultural systems in Puerto Rico and the US Virgin Islands. We analyze records and maps from the USDA Farm Service Agency, to typify participating farms, and to track changes in land cover, farm size, crop diversity, practices, and production levels resulting from their enrollment in such programs. Preliminary results indicate that many incentives programs are not tailored to agricultural tropical systems and prescribe alternatives that exclude traditional farming methods employed in small-scale and subsistence farms (e.g. crop insurance that benefit monoculture over intercropped systems). Moreover, many of the incentives are contradictory in their recommendations (e.g., crop insurance benefit sun-grown coffee production, while best agricultural practices recommend agroforestry with shade-grown coffee

Integrative modeling and novel particle swarm-based optimal design of wind farms

Science.gov (United States)

Chowdhury, Souma

allowing simultaneous optimization of the type and the location of the turbines. Layout optimization (using UWFLO) of a hypothetical 25-turbine commercial-scale wind farm provides a remarkable 4.4% increase in capacity factor compared to a conventional array layout. A further 2% increase in capacity factor is accomplished when the types of turbines are also optimally selected. The scope of turbine selection and placement however depends on the land configuration and the nameplate capacity of the farm. Such dependencies are not clearly defined in the existing literature. We develop response surface-based models, which implicitly employ UWFLO, to quantify and analyze the roles of these other crucial design factors in optimal wind farm planning. The wind pattern at a site can vary significantly from year to year, which is not adequately captured by conventional wind distribution models. The resulting ill-predictability of the annual distribution of wind conditions introduces significant uncertainties in the estimated energy output of the wind farm. A new method is developed to characterize these wind resource uncertainties and model the propagation of these uncertainties into the estimated farm output. The overall wind pattern/regime also varies from one region to another, which demands turbines with capabilities uniquely suited for different wind regimes. Using the UWFLO method, we model the performance potential of currently available turbines for different wind regimes, and quantify their feature-based expected market suitability. Such models can initiate an understanding of the product variation that current turbine manufacturers should pursue, to adequately satisfy the needs of the naturally diverse wind energy market. The wind farm design problems formulated in this dissertation involve highly multimodal objective and constraint functions and a large number of continuous and discrete variables. An effective modification of the PSO algorithm is developed to address such

Fishing Farmers or Farming Fishers? Fishing Typology of Inland Small-Scale Fishing Households and Fisheries Management in Singkarak Lake, West Sumatra, Indonesia

Science.gov (United States)

Yuerlita; Perret, Sylvain Roger; Shivakoti, Ganesh P.

2013-07-01

Technical and socio-economic characteristics are known to determine different types of fishers and their livelihood strategies. Faced with declining fish and water resources, small-scale fisheries engage into transformations in livelihood and fishing practices. The paper is an attempt to understand these changes and their socio-economic patterns, in the case of Singkarak Lake in West Sumatra, Indonesia. Based upon the hypothesis that riparian communities have diverse, complex yet structured and dynamic livelihood systems, the paper's main objective is to study, document and model the actual diversity in livelihood, practices and performance of inland small-scale fisheries along the Singkarak Lake, to picture how households are adapted to the situation, and propose an updated, workable model (typology) of those for policy. Principal component analysis and cluster analysis were used to develop a typology of fishing households. The results show that small-scale fishers can be classified into different types characterized by distinct livelihood strategies. Three household types are identified, namely "farming fishers" households (type I, 30 %), "fishing farmers" households (type II, 30 %), and "mainly fishers" households (type III, 40 %). There are significant differences among these groups in the number of boats owned, annual fishing income, agriculture income and farming experience. Type I consists of farming fishers, well equipped, with high fishing costs and income, yet with the lowest return on fishing assets. They are also landowners with farming income, showing the lowest return on land capital. Type II includes poor fishing farmers, landowners with higher farming income; they show the highest return on land asset. They have less fishing equipment, costs and income. Type III (mainly fishers) consists of poorer, younger fishers, with highest return on fishing assets and on fishing costs. They have little land, low farming income, and diversified livelihood

The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF

Directory of Open Access Journals (Sweden)

P. J. H. Volker

2015-11-01

Full Text Available We describe the theoretical basis, implementation, and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP, uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated for a neutral atmospheric boundary layer against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements, and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.

Magnitude, spatial scale and optimization of ecosystem services from a nutrient extraction mussel farm in the eutrophic Skive Fjord, Denmark

DEFF Research Database (Denmark)

Nielsen, Pernille; Cranford, P. J.; Maar, M.

2016-01-01

Suspended mussel aquaculture has been proposed as a possible mechanism by which to remove excess nutrients from eutrophic marine areas. In this study, seasonal mussel growth and water clarification (through seston and phytoplankton depletion) were studied at a commercial-scale nutrient extractive...... mussel farm in a highly eu - trophic Danish fjord. Spatial variations in mussel biomass were examined throughout the year and no significant differences were detected within the farm. Food depletion by mussels was examined at spatial scales ranging from individuals to the entire farm and surrounding area....... Phytoplankton depletion on the scale of individual mussel loops, determined using the siphon mimic approach, indicated between 27 and 44% depletion of chlorophyll a (chl a). Farm-scale depletion was detected and visualized based on intensive 3D spatial surveys of the distribution of chl a and total suspended...

Using a whole farm model to determine the impacts of mating management on the profitability of pasture-based dairy farms.

Science.gov (United States)

Beukes, P C; Burke, C R; Levy, G; Tiddy, R M

2010-08-01

An approach to assessing likely impacts of altering reproductive performance on productivity and profitability in pasture-based dairy farms is described. The basis is the development of a whole farm model (WFM) that simulates the entire farm system and holistically links multiple physical performance factors to profitability. The WFM consists of a framework that links a mechanistic cow model, a pasture model, a crop model, management policies and climate. It simulates individual cows and paddocks, and runs on a day time-step. The WFM was upgraded to include reproductive modeling capability using reference tables and empirical equations describing published relationships between cow factors, physiology and mating management. It predicts reproductive status at any time point for individual cows within a modeled herd. The performance of six commercial pasture-based dairy farms was simulated for the period of 12 months beginning 1 June 2005 (05/06 year) to evaluate the accuracy of the model by comparison with actual outcomes. The model predicted most key performance indicators within an acceptable range of error (residualprofitability of changes in farm "set-up" (farm conditions at the start of the farming year on 1 June) and mating management from 05/06 to 06/07 year. Among the six farms simulated, the 4-week calving rate emerged as an important set-up factor influencing profitability, while reproductive performance during natural bull mating was identified as an area with the greatest opportunity for improvement. The WFM presents utility to explore alternative management strategies to predict likely outcomes to proposed changes to a pasture-based farm system. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Wake Measurements in ECN's Scaled Wind Farm

Energy Technology Data Exchange (ETDEWEB)

Wagenaar, J.W.; Schepers, J.G. [ECN Wind Energy, Petten (Netherlands)

2013-02-15

In ECN's scaled wind farm the wake evolution is studied in two different situations. A single wake is studied at two different locations downstream of a turbine and a single wake is studied in conjunction with a triple wake. Here, the wake is characterized by the wind speed ratio, the turbulence intensity, the vertical wind speed and the turbulence (an)isotropy. Per situation all wake measurements are taken simultaneously together with the inflow conditions.

Modelling seabird collision risk with off-shore wind farms

Energy Technology Data Exchange (ETDEWEB)

Mateos, Maria; Arroyo, Gonzalo Munoz; Rosario, Jose Juan Alonso del

2011-07-01

Full text: Recent concern about the adverse effects of collision mortality of avian migrants at wind farms has highlighted the need to understand bird-wind turbine interactions. Here, a stochastic collision model, based on data of seabird behaviour collected on- site, is presented, as a flexible and easy to take tool to assess the collisions probabilities of off-shore wind farms in a pre-construction phase. The collision prediction model considering the wind farm area as a risk window has been constructed as a stochastic model for avian migrants, based on Monte Carlo simulation. The model calculates the probable number of birds collided per time unit. Migration volume, wind farm dimensions, vertical and horizontal distribution of the migratory passage, flight direction and avoidance rates, between other variables, are taken into account in different steps of the model as the input variables. In order to assess the weighted importance of these factors on collision probability predictions, collision probabilities obtained from the set of scenarios resulting from the different combinations of the input variables were modelled by using Generalised Additive Models. The application of this model to a hypothetical project for erecting a wind farm at the Strait of Gibraltar showed that collision probability, and consequently mortality rates, strongly depend on the values of the avoidance rates taken into account, and the distribution of birds into the different altitude layers. These parameters should be considered as priorities to be addressed in post-construction studies. (Author)

Dynamic simulation of sustainable farm development scenarios using cognitive modeling

Directory of Open Access Journals (Sweden)

Tuzhyk Kateryna

2017-03-01

Full Text Available Dynamic simulation of sustainable farm development scenarios using cognitive modeling. The paper presents a dynamic simulation system of sustainable development scenarios on farms using cognitive modeling. The system incorporates relevant variables which affect the sustainable development of farms. Its user provides answers to strategic issues connected with the level of farm sustainability over a long-term perspective of dynamic development. The work contains a description of the model structure as well as the results of simulations carried out on 16 farms in northern Ukraine. The results show that the process of sustainability is based mainly on the potential for innovation in agricultural production and biodiversity. The user is able to simulate various scenarios for the sustainable development of a farm and visualize the influence of factors on the economic and social situation, as well as on environmental aspects. Upon carrying out a series of simulations, it was determined that the development of farms characterized by sustainable development is based on additional profit, which serves as the main motivation for transforming a conventional farm into a sustainable one. Nevertheless, additional profit is not the only driving force in the system of sustainable development. The standard of living, market condition, and legal regulations as well as government support also play a significant motivational role.

Determinants of wind and solar energy system adoption by U.S. farms: A multilevel modeling approach

International Nuclear Information System (INIS)

Borchers, Allison M.; Xiarchos, Irene; Beckman, Jayson

2014-01-01

This article offers the first national examination of the determinants of adoption of wind and solar energy generation on U.S. farming operations. The inclusion of state policies and characteristics in a multilevel modeling approach distinguishes this study from past research utilizing logit models of technology adoption which focus only on the characteristics of the farm operation. Results suggest the propensity to adopt is higher for livestock operations, larger farms, operators with internet access, organic operations, and newer farmers. The results find state characteristics such as solar resources, per capita income levels, and predominantly democratic voting increasing the odds of farm adoption. This research suggests the relevance of state policy variables in explaining farm level outcomes is limited, although in combination best practice net metering and interconnection policies—policies designed to encourage the development of small scale distributed applications—are shown to increase the likelihood of farm solar and wind adoption. The prevalence of electric cooperatives—which are often not subject to state renewable energy policies and often service farms—is negatively related with the propensity to adopt and suggests that policy design may be a factor. - Highlights: • This is the first national examination of wind and solar energy adoption on U.S. farms. • Controlling for state policies distinguishes this study from past research of technology adoption. • We find net metering and interconnection policies increase the likelihood of farm adoption. • Results suggest that the design of renewable energy policies may limit their impact on farms

Impacts of large-scale offshore wind farm integration on power systems through VSC-HVDC

DEFF Research Database (Denmark)

Liu, Hongzhi; Chen, Zhe

2013-01-01

The potential of offshore wind energy has been commonly recognized and explored globally. Many countries have implemented and planned offshore wind farms to meet their increasing electricity demands and public environmental appeals, especially in Europe. With relatively less space limitation......, an offshore wind farm could have a capacity rating to hundreds of MWs or even GWs that is large enough to compete with conventional power plants. Thus the impacts of a large offshore wind farm on power system operation and security should be thoroughly studied and understood. This paper investigates...... the impacts of integrating a large-scale offshore wind farm into the transmission system of a power grid through VSC-HVDC connection. The concerns are focused on steady-state voltage stability, dynamic voltage stability and transient angle stability. Simulation results based on an exemplary power system...

ANEMOS: Development of a next generation wind power forecasting system for the large-scale integration of onshore and offshore wind farms.

Science.gov (United States)

Kariniotakis, G.; Anemos Team

2003-04-01

Objectives: Accurate forecasting of the wind energy production up to two days ahead is recognized as a major contribution for reliable large-scale wind power integration. Especially, in a liberalized electricity market, prediction tools enhance the position of wind energy compared to other forms of dispatchable generation. ANEMOS, is a new 3.5 years R&D project supported by the European Commission, that resembles research organizations and end-users with an important experience on the domain. The project aims to develop advanced forecasting models that will substantially outperform current methods. Emphasis is given to situations like complex terrain, extreme weather conditions, as well as to offshore prediction for which no specific tools currently exist. The prediction models will be implemented in a software platform and installed for online operation at onshore and offshore wind farms by the end-users participating in the project. Approach: The paper presents the methodology of the project. Initially, the prediction requirements are identified according to the profiles of the end-users. The project develops prediction models based on both a physical and an alternative statistical approach. Research on physical models gives emphasis to techniques for use in complex terrain and the development of prediction tools based on CFD techniques, advanced model output statistics or high-resolution meteorological information. Statistical models (i.e. based on artificial intelligence) are developed for downscaling, power curve representation, upscaling for prediction at regional or national level, etc. A benchmarking process is set-up to evaluate the performance of the developed models and to compare them with existing ones using a number of case studies. The synergy between statistical and physical approaches is examined to identify promising areas for further improvement of forecasting accuracy. Appropriate physical and statistical prediction models are also developed for

Ammonia emission model for whole farm evaluation of dairy production systems.

Science.gov (United States)

Rotz, C Alan; Montes, Felipe; Hafner, Sasha D; Heber, Albert J; Grant, Richard H

2014-07-01

Ammonia (NH) emissions vary considerably among farms as influenced by climate and management. Because emission measurement is difficult and expensive, process-based models provide an alternative for estimating whole farm emissions. A model that simulates the processes of NH formation, speciation, aqueous-gas partitioning, and mass transfer was developed and incorporated in a whole farm simulation model (the Integrated Farm System Model). Farm sources included manure on the floor of the housing facility, manure in storage (if used), field-applied manure, and deposits on pasture (if grazing is used). In a comprehensive evaluation of the model, simulated daily, seasonal, and annual emissions compared well with data measured over 2 yr for five free stall barns and two manure storages on dairy farms in the eastern United States. In a further comparison with published data, simulated and measured barn emissions were similar over differing barn designs, protein feeding levels, and seasons of the year. Simulated emissions from manure storage were also highly correlated with published emission data across locations, seasons, and different storage covers. For field applied manure, the range in simulated annual emissions normally bounded reported mean values for different manure dry matter contents and application methods. Emissions from pastures measured in northern Europe across seasons and fertilization levels were also represented well by the model. After this evaluation, simulations of a representative dairy farm in Pennsylvania illustrated the effects of animal housing and manure management on whole farm emissions and their interactions with greenhouse gas emissions, nitrate leaching, production costs, and farm profitability. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Leverages for on-farm innovation from farm typologies? An illustration for family-based dairy farms in north-west Michoacán, Mexico

NARCIS (Netherlands)

Cortez Arriola, J.; Rossing, W.A.H.; Amendola Massiotti, R.D.; Scholberg, J.M.S.; Groot, J.C.J.; Tittonell, P.A.

2015-01-01

Knowledge on farm diversity provides insight into differences among farms, enables scaling from individual farm to farm population level and vice versa, and has been used in the definition of recommendation domains for introduction of novel technologies. Farm diversity can be broadly described in

Results of Sexbierum Wind Farm: single wake measurements

NARCIS (Netherlands)

Cleijne, J.W.

1993-01-01

In the framework of the JOULE-0064 'Full-scale Measurements in Wind Turbine Arrays' in the period between June-November 1992 measurements have been performed in the Sexbierum Wind Farm. The aim of the measurements is to provide data for the validation of wake and wind farm models, which are being

Farming in an Agriburban Ecovillage Development

Directory of Open Access Journals (Sweden)

Lenore Newman

2014-12-01

Full Text Available A growing desire for local food systems has increased interest in peri-urban farming, leading to the rise of agriburban landscapes, in which a desire to farm or to be near farmland is a contributing factor to development patterns. Interviews and site visits to the Yarrow Ecovillage near Vancouver, Canada, outline an example of a development that allows new farmers access to land in a setting with few tensions between farming and non-farming residents in a zone on the edge of a protected agricultural region. Although there are limitations to replication of this model, we suggest that intentional settlements with an agricultural element on the rural/urban fringe could buffer traditional tensions between farm usage and residential usage, while allowing small-scale farmers a place to farm in areas with prohibitively high land values.

The impact of farm size on sustainability of dutch dairy farms

NARCIS (Netherlands)

Meulen, van der H.A.B.; Dolman, M.A.; Jager, J.H.; Venema, G.S.

2014-01-01

Sustainable milk production systems require economically viable, environmentally sound and socially acceptable practices. This study compared the economic, environmental and societal impact of large-scale farms with other dairy farms in the Dutch Farm Accountancy Data Network (FADN). Moreover the

Modeling and Simulation of a 12 MW Wind Farm

Directory of Open Access Journals (Sweden)

GROZA, V.

2010-05-01

Full Text Available The installation of wind turbines in power systems has developed rapidly through the last 20 years. In this paper a complete simulation model of a 6 x 2 MW wind turbines is presented using data from a wind farm installed in Denmark. A model of the wind turbine with cage-rotor induction generator is presented in details. A set of simulations are performed and they show that it is possible to simulate a complete wind farm from wind to the grid. The simulation tool can also be used to simulate bigger wind farms connected to the grid.

Prevalence and concentration of Salmonella and Campylobacter in the processing environment of small-scale pastured broiler farms.

Science.gov (United States)

Trimble, Lisa M; Alali, Walid Q; Gibson, Kristen E; Ricke, Steven C; Crandall, Philip; Jaroni, Divya; Berrang, Mark; Habteselassie, Mussie Y

2013-11-01

A growing niche in the locally grown food movement is the small-scale production of broiler chickens using the pasture-raised poultry production model. Limited research exists that focuses on Salmonella and Campylobacter contamination in the environment associated with on-farm processing of pasture-raised broilers. The objective of this study was to establish data relative to Salmonella and Campylobacter prevalence and concentration in soil and mortality compost resulting from prior processing waste disposal in the small-scale, on-farm broiler processing environment. Salmonella and Campylobacter concentrations were determined in soil (n = 42), compost (n = 39), and processing wastewater (PWW; n = 46) samples from 4 small broiler farms using a 3-tube most probable number (MPN) method for Salmonella and direct plating method for Campylobacter. Salmonella prevalence and concentration (mean log10 MPN per sample weight or volume) in soil [60%, 0.97 (95% CI: 0.66 to 1.27)], compost [64%, 0.95 (95% CI: 0.66 to 1.24)], and wastewater [48%, 1.29 (95% CI: 0.87 to 1.71)] were not significantly different (P > 0.05). Although Campylobacter prevalence was not significantly different by sample type (64.3, 64.3, and 45.7% in soil, compost, and PWW, respectively), the concentration (mean log10 cfu) of this pathogen was significantly lower (P poultry production waste disposal practices and provides a record of data that may serve as a guide for future improvement of these practices. Further research is needed regarding the small-scale broiler production environment in relation to improving disposal of processing waste for optimum control of human pathogens.

Farm production performance in Russian regions: farm panel data analysis

NARCIS (Netherlands)

Bezlepkina, I.

2003-01-01

The Russian agricultural sector has experienced many problems since the beginning of the 1990s that resulted in a fall in farm output. Employing a production function approach and, unlike other studies, farm-level data on more than 20,000 Russian large-scale farms for the period 1995-2000, this

Using Satellite SAR to Characterize the Wind Flow around Offshore Wind Farms

DEFF Research Database (Denmark)

Hasager, Charlotte Bay; Vincent, Pauline; Badger, Jake

2015-01-01

Offshore wind farm cluster effects between neighboring wind farms increase rapidly with the large-scale deployment of offshore wind turbines. The wind farm wakes observed from Synthetic Aperture Radar (SAR) are sometimes visible and atmospheric and wake models are here shown to convincingly repro...

Collective action and technology development: up-scaling of innovation in rice farming communities in Northern Thailand

NARCIS (Netherlands)

Limnirankul, B.

2007-01-01

Keywords:small-scale rice farmers, collective action, community rice seed, local innovations, green manure crop, contract farming, participatory technology development, up-scaling, technological configuration, grid-group theory,

High-resolution computational algorithms for simulating offshore wind turbines and farms: Model development and validation

Energy Technology Data Exchange (ETDEWEB)

Calderer, Antoni [Univ. of Minnesota, Minneapolis, MN (United States); Yang, Xiaolei [Stony Brook Univ., NY (United States); Angelidis, Dionysios [Univ. of Minnesota, Minneapolis, MN (United States); Feist, Chris [Univ. of Minnesota, Minneapolis, MN (United States); Guala, Michele [Univ. of Minnesota, Minneapolis, MN (United States); Ruehl, Kelley [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Guo, Xin [Univ. of Minnesota, Minneapolis, MN (United States); Boomsma, Aaron [Univ. of Minnesota, Minneapolis, MN (United States); Shen, Lian [Univ. of Minnesota, Minneapolis, MN (United States); Sotiropoulos, Fotis [Stony Brook Univ., NY (United States)

2015-10-30

The present project involves the development of modeling and analysis design tools for assessing offshore wind turbine technologies. The computational tools developed herein are able to resolve the effects of the coupled interaction of atmospheric turbulence and ocean waves on aerodynamic performance and structural stability and reliability of offshore wind turbines and farms. Laboratory scale experiments have been carried out to derive data sets for validating the computational models.

Combination of Deterministic and Probabilistic Meteorological Models to enhance Wind Farm Power Forecasts

International Nuclear Information System (INIS)

Bremen, Lueder von

2007-01-01

Large-scale wind farms will play an important role in the future worldwide energy supply. However, with increasing wind power penetration all stakeholders on the electricity market will ask for more skilful wind power predictions regarding save grid integration and to increase the economic value of wind power. A Neural Network is used to calculate Model Output Statistics (MOS) for each individual forecast model (ECMWF and HIRLAM) and to model the aggregated power curve of the Middelgrunden offshore wind farm. We showed that the combination of two NWP models clearly outperforms the better single model. The normalized day-ahead RMSE forecast error for Middelgrunden can be reduced by 1% compared to single ECMWF. This is a relative improvement of 6%. For lead times >24h it is worthwhile to use a more sophisticated model combination approach than simple linear weighting. The investigated principle component regression is able to extract the uncorrelated information from two NWP forecasts. The spread of Ensemble Predictions is related to the skill of wind power forecasts. Simple contingency diagrams show that low spread corresponds is more often related to low forecast errors and high spread to large forecast errors

EFFECTS OF LARGE-SCALE POULTRY FARMS ON AQUATIC MICROBIAL COMMUNITIES: A MOLECULAR INVESTIGATION.

Science.gov (United States)

The effects of large-scale poultry production operations on water quality and human health are largely unknown. Poultry litter is frequently applied as fertilizer to agricultural lands adjacent to large poultry farms. Run-off from the land introduces a variety of stressors into t...

Adoption of Small-Scale Irrigation Farming as a Climate-Smart Agriculture Practice and Its Influence on Household Income in the Chinyanja Triangle, Southern Africa

Directory of Open Access Journals (Sweden)

Nelson Mango

2018-04-01

Full Text Available This article is concerned with the adoption of small-scale irrigation farming as a climate-smart agriculture practice and its influence on household income in the Chinyanja Triangle. Chinyanja Triangle is a region that is increasingly experiencing mid-season dry spells and an increase in occurrence of drought, which is attributed largely to climate variability and change. This poses high agricultural production risks, which aggravate poverty and food insecurity. For this region, adoption of small-scale irrigation farming as a climate-smart agriculture practice is very important. Through a binary logistic and ordinary least squares regression, this article determines factors that influence the adoption of small-scale irrigation farming as a climate-smart agriculture practice and its influence on income among smallholder farmers. The results show that off-farm employment, access to irrigation equipment, access to reliable water sources and awareness of water conservation practices, such as rainwater harvesting, have a significant influence on the adoption of small-scale irrigation farming. On the other hand, the farmer’s age, distance travelled to the nearest market and nature of employment negatively influence the adoption of small-scale irrigation farming decisions. Ordinary least squares regression results showed that the adoption of small-scale irrigation farming as a climate-smart agriculture practice has a significant positive influence on agricultural income. We therefore conclude that to empower smallholder farmers to respond quickly to climate variability and change, practices that will enhance the adoption of small-scale irrigation farming in the Chinyanja Triangle are critical, as this will significantly affect agricultural income. In terms of policy, we recommend that the governments of Zambia, Malawi and Mozambique, which cover the Chinyanja Triangle, formulate policies that will enhance the adoption of sustainable small scale

The economic efficiency of conservation measures for amphibians in organic farming--results from bio-economic modelling.

Science.gov (United States)

Schuler, Johannes; Sattler, Claudia; Helmecke, Angela; Zander, Peter; Uthes, Sandra; Bachinger, Johann; Stein-Bachinger, Karin

2013-01-15

This paper presents a whole farm bio-economic modelling approach for the assessment and optimisation of amphibian conservation conditions applied at the example of a large scale organic farm in North-Eastern Germany. The assessment focuses mainly on the habitat quality as affected by conservation measures such as through specific adapted crop production activities (CPA) and in-field buffer strips for the European tree frog (Hyla arborea), considering also interrelations with other amphibian species (i.e. common spadefoot toad (Pelobates fuscus), fire-bellied toad (Bombina bombina)). The aim of the approach is to understand, analyse and optimize the relationships between the ecological and economic performance of an organic farming system, based on the expectation that amphibians are differently impacted by different CPAs. The modelling system consists of a set of different sub-models that generate a farm model on the basis of environmentally evaluated CPAs. A crop-rotation sub-model provides a set of agronomically sustainable crop rotations that ensures overall sufficient nitrogen supply and controls weed, pest and disease infestations. An economic sub-model calculates the gross margins for each possible CPA including costs of inputs such as labour and machinery. The conservation effects of the CPAs are assessed with an ecological sub-model evaluates the potential negative or positive effect that each work step of a CPA has on amphibians. A mathematical programming sub-model calculates the optimal farm organization taking into account the limited factors of the farm (e.g. labour, land) as well as ecological improvements. In sequential model runs, the habitat quality is to be improved by the model, while the highest possible gross margin is still to be achieved. The results indicate that the model can be used to show the scope of action that a farmer has to improve habitat quality by reducing damage to amphibian population on its land during agricultural activities

Analytical Model for Mean Flow and Fluxes of Momentum and Energy in Very Large Wind Farms

Science.gov (United States)

Markfort, Corey D.; Zhang, Wei; Porté-Agel, Fernando

2018-01-01

As wind-turbine arrays continue to be installed and the array size continues to grow, there is an increasing need to represent very large wind-turbine arrays in numerical weather prediction models, for wind-farm optimization, and for environmental assessment. We propose a simple analytical model for boundary-layer flow in fully-developed wind-turbine arrays, based on the concept of sparsely-obstructed shear flows. In describing the vertical distribution of the mean wind speed and shear stress within wind farms, our model estimates the mean kinetic energy harvested from the atmospheric boundary layer, and determines the partitioning between the wind power captured by the wind turbines and that absorbed by the underlying land or water. A length scale based on the turbine geometry, spacing, and performance characteristics, is able to estimate the asymptotic limit for the fully-developed flow through wind-turbine arrays, and thereby determine if the wind-farm flow is fully developed for very large turbine arrays. Our model is validated using data collected in controlled wind-tunnel experiments, and its usefulness for the prediction of wind-farm performance and optimization of turbine-array spacing are described. Our model may also be useful for assessing the extent to which the extraction of wind power affects the land-atmosphere coupling or air-water exchange of momentum, with implications for the transport of heat, moisture, trace gases such as carbon dioxide, methane, and nitrous oxide, and ecologically important oxygen.

Dynamical and statistical-dynamical modelling of wind farm flows with WRF

DEFF Research Database (Denmark)

Volker, Patrick; Badger, Jake; Hahmann, Andrea N.

2016-01-01

the power production of a target wind farm and (II) how large wind farms can get if they are to remain efficient and productive power generators. The modelling of wind farm wake flows is challenging, since it includes processes from the micro- to mesoscale meteorology. We use the Weather Research......A pledge to increase the share of renewable energies has led to a focus on offshore wind energy in many western European countries. With an increasing number of offshore wind farms to be installed it becomes important to understand (I) the degree to which wakes from neighbouring wind farms affect...... and Forecast (WRF) model that allows us to simulate mesoscale features of wind farm wakes. Its limited horizontal resolution – in microscale terms – however, requires flow characteristics, such as single turbine wakes, to be parametrised....

Wind farm density and harvested power in very large wind farms: A low-order model

Science.gov (United States)

Cortina, G.; Sharma, V.; Calaf, M.

2017-07-01

In this work we create new understanding of wind turbine wakes recovery process as a function of wind farm density using large-eddy simulations of an atmospheric boundary layer diurnal cycle. Simulations are forced with a constant geostrophic wind and a time varying surface temperature extracted from a selected period of the Cooperative Atmospheric Surface Exchange Study field experiment. Wind turbines are represented using the actuator disk model with rotation and yaw alignment. A control volume analysis around each turbine has been used to evaluate wind turbine wake recovery and corresponding harvested power. Results confirm the existence of two dominant recovery mechanisms, advection and flux of mean kinetic energy, which are modulated by the background thermal stratification. For the low-density arrangements advection dominates, while for the highly loaded wind farms the mean kinetic energy recovers through fluxes of mean kinetic energy. For those cases in between, a smooth balance of both mechanisms exists. From the results, a low-order model for the wind farms' harvested power as a function of thermal stratification and wind farm density has been developed, which has the potential to be used as an order-of-magnitude assessment tool.

Reducing Turbine Mechanical Loads Using Flow Model-Based Wind Farm Controller

DEFF Research Database (Denmark)

Kazda, Jonas; Cutululis, Nicolaos Antonio

Cumulated O&M costs of offshore wind farms are comparable with wind turbine CAPEX of such wind farm. In wind farms, wake effects can result in up to 80% higher fatigue loads at downstream wind turbines [1] and consequently larger O&M costs. The present work therefore investigates to reduce...... these loads during the provision of grid balancing services using optimal model-based wind farm control. Wind farm controllers coordinate the operating point of wind turbines in a wind farm in order to achieve a given objective. The investigated objective of the control in this work is to follow a total wind...... farm power reference while reducing the tower bending moments of the turbines in the wind farm. The wind farm controller is tested on a 8 turbine array, which is representative of a typical offshore wind farm. The operation of the wind farm is simulated using the dynamic wind farm simulation tool S imWind...

Long Island Solar Farm

Energy Technology Data Exchange (ETDEWEB)

Anders, R.

2013-05-01

The Long Island Solar Farm (LISF) is a remarkable success story, whereby very different interest groups found a way to capitalize on unusual circumstances to develop a mutually beneficial source of renewable energy. The uniqueness of the circumstances that were necessary to develop the Long Island Solar Farm make it very difficult to replicate. The project is, however, an unparalleled resource for solar energy research, which will greatly inform large-scale PV solar development in the East. Lastly, the LISF is a superb model for the process by which the project developed and the innovation and leadership shown by the different players.

A Simulation Software for the Analysis of Cropping Systems in Livestock Farms

Directory of Open Access Journals (Sweden)

Tommaso Maggiore

2011-02-01

Full Text Available Simulation models can support quantitative and integrated analyses of agricultural systems. In this paper we describe VA.TE., a computer program developed to support the preparation and evaluation of nitrogen fertilising plans for livestock farms in the Lombardy region (northern Italy. The program integrates the cropping systems simulation model CropSyst with several regional agricultural databases, and provides the users with a simple framework for applying the model and interpreting results. VA.TE. makes good use of available data, integrating into a single relational database existing information about soils, climate, farms, animal breeds, crops and crop managements, and providing estimates of missing input variables. A simulation engine manages the entire simulation process: choice of farms to be simulated, model parameterisation, creation of model inputs, simulation of scenarios and analysis of model outputs. The program permits to apply at farm scale a model originally designed for the lower scale of homogeneous land parcel. It manages alternative simulation scenarios for each farm, helping to identify solutions to combine low nitrate losses and satisfactory crop yields. Example simulation results for three farms located on different soils and having varying levels of nitrogen surplus show that the integrated system (model + database can manage various simulations automatically, and that strategies to improve N management can be refined by analysing the simulated amounts and temporal patterns of nitrogen leaching.We conclude by discussing the issues regarding the integration of existing regional databases with simulation models.

A Simulation Software for the Analysis of Cropping Systems in Livestock Farms

Directory of Open Access Journals (Sweden)

Luca Bechini

2008-09-01

Full Text Available Simulation models can support quantitative and integrated analyses of agricultural systems. In this paper we describe VA.TE., a computer program developed to support the preparation and evaluation of nitrogen fertilising plans for livestock farms in the Lombardy region (northern Italy. The program integrates the cropping systems simulation model CropSyst with several regional agricultural databases, and provides the users with a simple framework for applying the model and interpreting results. VA.TE. makes good use of available data, integrating into a single relational database existing information about soils, climate, farms, animal breeds, crops and crop managements, and providing estimates of missing input variables. A simulation engine manages the entire simulation process: choice of farms to be simulated, model parameterisation, creation of model inputs, simulation of scenarios and analysis of model outputs. The program permits to apply at farm scale a model originally designed for the lower scale of homogeneous land parcel. It manages alternative simulation scenarios for each farm, helping to identify solutions to combine low nitrate losses and satisfactory crop yields. Example simulation results for three farms located on different soils and having varying levels of nitrogen surplus show that the integrated system (model + database can manage various simulations automatically, and that strategies to improve N management can be refined by analysing the simulated amounts and temporal patterns of nitrogen leaching.We conclude by discussing the issues regarding the integration of existing regional databases with simulation models.

Sustaining Small Scale Farming: Evidence of Poverty and income Disparity among Rural Farming Households in South-South Region of Nigeria

Directory of Open Access Journals (Sweden)

Sunday B. Akpan

2016-09-01

Full Text Available The incidence of poverty is evidenced among rural farm households in developing societies. As a result of persistence poverty among rural farm households, there is a sudden upsurge in agricultural livelihood diversification and rural-urban migration resulting in high rate of urban unemployment. To help generate suitable policy variables to help tackle this rampaging issue in the South- south region of Nigeria, this study specifically analyses poverty and income inequality as well as identified determinants of poverty among rural farm households in Akwa Ibom State, Nigeria. Data were collected from 390 rural farm household heads spread across the rural areas of the State. Combination of sampling methods was employed to sample cross-sectional data from respondents. The study used descriptive tools and regression analysis (Tobit regressions to analyse information collected. The socio-economic analysis reveals that most farming household heads were male; an average of 12.3 years of formal was discovered; social capital formation was poor, while average age stood at 42.5 years. About 33.08 % of male headed households and 22.05 % of female-headed households live below poverty line in the study area. Income inequality index revealed 0.4210 for male headed households and 0.4531 for the female counterpart. The Tobit model estimates revealed that, household head farming experience, years in the social organisation, a level of formal education, farm and non-farm income were negative drivers of rural poverty in the region. Household’s age, household size, structure of land ownership and gender were positive drivers of poverty among rural farming households. It is recommended that sound family welfare packages should be implemented in the rural communities. Also, the social capital formation should be promoted among rural farming households, while adult education policies should be re-visited. The government of the region should also improve educational

Modelling the Spread of Farming in the Bantu-Speaking Regions of Africa: An Archaeology-Based Phylogeography

OpenAIRE

Russell, Thembi; Silva, Fabio; Steele, James

2014-01-01

We use archaeological data and spatial methods to reconstruct the dispersal of farming into areas of sub-Saharan Africa now occupied by Bantu language speakers, and introduce a new large-scale radiocarbon database and a new suite of spatial modelling techniques. We also introduce a method of estimating phylogeographic relationships from archaeologically-modelled dispersal maps, with results produced in a format that enables comparison with linguistic and genetic phylogenies. Several hypothese...

Shadowing effects of offshore wind farms - an idealised mesoscale model study

DEFF Research Database (Denmark)

Volker, Patrick; Badger, Jake; Hahmann, Andrea N.

The study of wind farm (WF) interaction is expected to gain importance, since the offshore wind farm density will increase especially in the North Sea in the near future. We present preliminary results of wind farm interaction simulated by mesoscale models. We use the Explicit Wake Parametrisatio...

Scheduling models in farm management : a new approach

NARCIS (Netherlands)

Wijngaard, P.J.M.

1988-01-01

Three operational planning models to calculate schedules for an arable farm are examined. These models are a linear programming model, a dynamic programming model and a simulation model. They are examined at different levels of aggregation and relaxation in a retrospective way. Also a

On wake modeling, wind-farm gradients and AEP predictions at the Anholt wind farm

DEFF Research Database (Denmark)

Pena Diaz, Alfredo; Hansen, Kurt Schaldemose; Ott, Søren

2017-01-01

of the mesoscale simulations and supervisory control and data acquisition (SCADA), we show that for westerly flow in particular, there is a clear horizontal wind-speed gradient over the wind farm. We also use the mesoscale simulations to derive the undisturbed inflow conditions that are coupled with three commonly....... When looking at westerly flow wake cases, where the impact of the horizontal wind-speed gradient on the power of the undisturbed turbines is largest, the wake models agree with the SCADA fairly well; when looking at a southerly flow case, where the wake losses are highest, the wake models tend...... to underestimate the wake loss. With the mesoscale-wake model setup, we are also able to estimate the capacity factor of the wind farm rather well when compared to that derived from the SCADA. Finally, we estimate the uncertainty of the wake models by bootstrapping the SCADA. The models tend to underestimate...

Simulations of an Offshore Wind Farm Using Large-Eddy Simulation and a Torque-Controlled Actuator Disc Model

Science.gov (United States)

Creech, Angus; Früh, Wolf-Gerrit; Maguire, A. Eoghan

2015-05-01

We present here a computational fluid dynamics (CFD) simulation of Lillgrund offshore wind farm, which is located in the Øresund Strait between Sweden and Denmark. The simulation combines a dynamic representation of wind turbines embedded within a large-eddy simulation CFD solver and uses hr-adaptive meshing to increase or decrease mesh resolution where required. This allows the resolution of both large-scale flow structures around the wind farm, and the local flow conditions at individual turbines; consequently, the response of each turbine to local conditions can be modelled, as well as the resulting evolution of the turbine wakes. This paper provides a detailed description of the turbine model which simulates the interaction between the wind, the turbine rotors, and the turbine generators by calculating the forces on the rotor, the body forces on the air, and instantaneous power output. This model was used to investigate a selection of key wind speeds and directions, investigating cases where a row of turbines would be fully aligned with the wind or at specific angles to the wind. Results shown here include presentations of the spin-up of turbines, the observation of eddies moving through the turbine array, meandering turbine wakes, and an extensive wind farm wake several kilometres in length. The key measurement available for cross-validation with operational wind farm data is the power output from the individual turbines, where the effect of unsteady turbine wakes on the performance of downstream turbines was a main point of interest. The results from the simulations were compared to the performance measurements from the real wind farm to provide a firm quantitative validation of this methodology. Having achieved good agreement between the model results and actual wind farm measurements, the potential of the methodology to provide a tool for further investigations of engineering and atmospheric science problems is outlined.

Plot-, farm-, and watershed-scale effects of coffee cultivation in runoff and sediment production in western Puerto Rico.

Science.gov (United States)

Ramos-Scharrón, Carlos E; Figueroa-Sánchez, Yasiel

2017-11-01

The combination of a topographically abrupt wet-tropical setting with the high level of soil exposure that typifies many sun-grown coffee farms represents optimal conditions for high erosion rates. Although traditionally considered as a main cause for water resource degradation, limited empirical evidence has existed to document its true contribution. This study relies on plot-scale experimental results conducted in western Puerto Rico to assess the impact of cultivated surfaces and farm access roads on runoff and sediment production from the plot to the farm and watershed scales. Results show that unsurfaced and graveled road surfaces produce one- to two-orders of magnitude more per unit area runoff than cultivated lands. Similarly, erosion rates from unsurfaced roads are about 102 g m -2 per cm of rainfall and these are two-orders of magnitude greater than from actively cultivated surfaces. Mitigation practices such as uncompacting road surfaces by ripping and gravel application reduce onsite erosion rates to 0.6% and 8% of unsurfaced conditions, respectively. At the farm scale, coffee farms are estimated to produce sediment at a rate of 12-18 Mg ha -1 yr -1 , and roads are undoubtedly the dominant sediment source responsible for 59-95% of the total sediment produced. The costs associated to ameliorating erosion problems through road graveling are high. Therefore, a combined approach that treats road erosion onsite with one that traps sediment before it reaches river networks is the viable solution to this problem. Copyright © 2017 Elsevier Ltd. All rights reserved.

Measuring power output intermittency and unsteady loading in a micro wind farm model

OpenAIRE

Bossuyt, Juliaan; Howland, Michael; Meneveau, Charles; Meyers, Johan

2016-01-01

In this study porous disc models are used as a turbine model for a wind-tunnel wind farm experiment, allowing the measurement of the power output, thrust force and spatially averaged incoming velocity for every turbine. The model's capabilities for studying the unsteady turbine loading, wind farm power output intermittency and spatio temporal correlations between wind turbines are demonstrated on an aligned wind farm, consisting of 100 wind turbine models.

FACTORS INFLUENCING DECISIONS FOR USING OUTSIDE FUNDS FOR FARM INVESTMENTS AND PROPRIETOR WITHDRAWALS BY SMALL-SCALE FARMERS IN ABIA STATE, NIGERIA

Directory of Open Access Journals (Sweden)

Chriso O. EMEROLE

2013-08-01

Full Text Available This study on factors influencing decisions for using outside funds for Farm investments and for proprietor withdrawals was carried out among rural small-scale farm households in Abia state, Nigeria. A cross-sectional survey of ninety (90 rural farm households of multi-type (varied enterprises was carried out using cluster random sampling technique in three communities, each chosen from one of the three agricultural zones of the state. Results indicated rural household level variables that positively influenced decisions to source farm investment fund to include level of education, gender, membership of cooperative society, interest charge, land acquisition method, and ease of getting loan. Other factors that negatively influenced decisions include farming as major occupation, household savings, household size, and distance of farmers’ home to source of credit. Proprietor withdrawal decisions were positively influenced by household level variables like taking farming as major occupation, payment of school fees for children of farmers, and amount of credit so far repaid by a farm household. Other factors namely household size, being member of cooperative society or savings group, interest charges on loan, off-farm income, and household savings had negative influences on proprietor withdrawal decisions. We recommended that small-scale farmers should not borrow their start-up capital from outside their households but as their farm businesses stabilize, they could decide to take loans from outside to cover their working capital and/or expand their farms and be prepared to repay such loans according to contractual agreements.

8th international workshop on large-scale integration of wind power into power systems as well as on transmission networks for offshore wind farms. Proceedings

International Nuclear Information System (INIS)

Betancourt, Uta; Ackermann, Thomas

2009-01-01

Within the 8th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Farms at 14th to 15th October, 2009 in Bremen (Federal Republic of Germany), lectures and posters were presented to the following sessions: (1) Keynote session and panel; (2) Grid integration studies and experience: Europe; (3) Connection of offshore wind farms; (4) Wind forecast; (5) High voltage direct current (HVDC); (6) German grid code issues; (7) Offshore grid connection; (8) Grid integration studies and experience: North America; (9) SUPWIND - Decision support tools for large scale integration of wind; (10) Windgrid - Wind on the grid: An integrated approach; (11) IEA Task 25; (12) Grid code issues; (13) Market Issues; (14) Offshore Grid; (15) Modelling; (16) Wind power and storage; (17) Power system balancing; (18) Wind turbine performance; (19) Modelling and offshore transformer.

Analysis of costs and returns in rice farming by farm size in Ebonyi ...

African Journals Online (AJOL)

This study was designed to analyze the costs and returns of rice farming by farm size in Ebonyi state of Nigeria. Data were collected through the cost-route approach with pre-tested structured questionnaire from 40 randomly selected small scale and 40 purposively selected large-scale rice farmers, Data were analyzed by ...

Short-term Wind Forecasting at Wind Farms using WRF-LES and Actuator Disk Model

Science.gov (United States)

Kirkil, Gokhan

2017-04-01

Short-term wind forecasts are obtained for a wind farm on a mountainous terrain using WRF-LES. Multi-scale simulations are also performed using different PBL parameterizations. Turbines are parameterized using Actuator Disc Model. LES models improved the forecasts. Statistical error analysis is performed and ramp events are analyzed. Complex topography of the study area affects model performance, especially the accuracy of wind forecasts were poor for cross valley-mountain flows. By means of LES, we gain new knowledge about the sources of spatial and temporal variability of wind fluctuations such as the configuration of wind turbines.

Modelling the wind-borne spread of highly pathogenic avian influenza virus between farms.

Directory of Open Access Journals (Sweden)

Amos Ssematimba

Full Text Available A quantitative understanding of the spread of contaminated farm dust between locations is a prerequisite for obtaining much-needed insight into one of the possible mechanisms of disease spread between farms. Here, we develop a model to calculate the quantity of contaminated farm-dust particles deposited at various locations downwind of a source farm and apply the model to assess the possible contribution of the wind-borne route to the transmission of Highly Pathogenic Avian Influenza virus (HPAI during the 2003 epidemic in the Netherlands. The model is obtained from a Gaussian Plume Model by incorporating the dust deposition process, pathogen decay, and a model for the infection process on exposed farms. Using poultry- and avian influenza-specific parameter values we calculate the distance-dependent probability of between-farm transmission by this route. A comparison between the transmission risk pattern predicted by the model and the pattern observed during the 2003 epidemic reveals that the wind-borne route alone is insufficient to explain the observations although it could contribute substantially to the spread over short distance ranges, for example, explaining 24% of the transmission over distances up to 25 km.

Fuzzy generation scheduling for a generation company (GenCo) with large scale wind farms

International Nuclear Information System (INIS)

Siahkali, H.; Vakilian, M.

2010-01-01

Wind power is a promising alternative in power generation because of its tremendous environmental and social benefits. Generation scheduling (GS) is more important in a power system integrating wind farms. Unlike conventional power generation sources, wind power generators supply intermittent power because of uncertainty in resource. This paper presents a fuzzy approach to the generation scheduling problem of a GenCo considering uncertainties in parameters or constraints such as load, reserve and available wind power generation. The modeling of constraints is an important issue in power system scheduling. A fuzzy optimization approach is an approach that can be used to obtain the generation scheduling under an uncertain environment. In this paper, a fuzzy optimization-based method is developed to solve power system GS problem with fuzzy objective and constraints. The crisp formulation of this GS problem is firstly defined and is rearranged by introduction of a membership function of some constraints and objective function. Then, this fuzzy optimization problem is converted to a crisp optimization and solved using GAMS software by mixed integer nonlinear programming. Employing the fuzzy optimization GS, it is expected that in practice a higher profit would be achieved in the operation and cost management of a real power system with large scale wind farms in different level of constraints' satisfaction. The proposed approach is applied to a sample system (including six conventional units and two wind farms) and the results are compared with the results of crisp solution. This approach is also applied to a larger test case to demonstrate the robustness of this fuzzy optimization method.

Spatial downscaling of soil prediction models based on weighted generalized additive models in smallholder farm settings.

Science.gov (United States)

Xu, Yiming; Smith, Scot E; Grunwald, Sabine; Abd-Elrahman, Amr; Wani, Suhas P; Nair, Vimala D

2017-09-11

Digital soil mapping (DSM) is gaining momentum as a technique to help smallholder farmers secure soil security and food security in developing regions. However, communications of the digital soil mapping information between diverse audiences become problematic due to the inconsistent scale of DSM information. Spatial downscaling can make use of accessible soil information at relatively coarse spatial resolution to provide valuable soil information at relatively fine spatial resolution. The objective of this research was to disaggregate the coarse spatial resolution soil exchangeable potassium (K ex ) and soil total nitrogen (TN) base map into fine spatial resolution soil downscaled map using weighted generalized additive models (GAMs) in two smallholder villages in South India. By incorporating fine spatial resolution spectral indices in the downscaling process, the soil downscaled maps not only conserve the spatial information of coarse spatial resolution soil maps but also depict the spatial details of soil properties at fine spatial resolution. The results of this study demonstrated difference between the fine spatial resolution downscaled maps and fine spatial resolution base maps is smaller than the difference between coarse spatial resolution base maps and fine spatial resolution base maps. The appropriate and economical strategy to promote the DSM technique in smallholder farms is to develop the relatively coarse spatial resolution soil prediction maps or utilize available coarse spatial resolution soil maps at the regional scale and to disaggregate these maps to the fine spatial resolution downscaled soil maps at farm scale.

Modelling Options for Policy Impact Analysis on African Dairy Farms

Directory of Open Access Journals (Sweden)

Oghaiki Asaah NDAMBI

2008-01-01

Full Text Available Studies on the priorities for agricultural research in Eastern and CentralAfrica concluded that milk is the most important commodity for research anddevelopment in the region, based on its potential contribution to the agriculturalGDP. It has been presumed that, the right policies, marketing systems and technicalsupport must be sought for dairy development in Africa. In order to determine theright development pattern, appropriate analytical tools must be applied. The TIPICAL(Technology Impact Policy Impact model was used to analyse the impact ofdifferent policies on two typical dairy farming systems in Uganda, which accountfor more than 70% of milk produced in the country. Seven influential policy areaswere also identified: provision of veterinary services, consumption promotion,marketing promotion, input provision, credit access improvement, milk qualityimprovement and genetic improvement. In general, the policy impacts are very littleon farms with local cows but can be magnified up to threefold, if the farms havegraded cows. Policies which improve farmers’ accessibility to markets have thegreatest impacts. The results obtained from this model were compared to thoseusing the EXTRAPOLATE model. This comparison shows that both models couldcomplement each other in analysing policy impacts on African dairy farms.However, differences in results from the models indicate that more focus should bemade on farmers’ willingness to adopt new technology.

Modeling Commercial Freshwater Turtle Production on US Farms for Pet and Meat Markets.

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Ivana Mali

Full Text Available Freshwater turtles are being exploited for meat, eggs, traditional medicine, and pet trade. As a response, turtle farming became a booming aquaculture industry in the past two decades, specifically in the southeastern states of the United States of America (US and across Southeast Asia. However, US turtle farms are currently producing turtles only for the pet trade while commercial trappers remain focused on catching the largest individuals from the wild. In our analyses we have created a biological and economic model that describes farming operations on a representative turtle farm in Louisiana. We first modeled current production of hatchling and yearling red-eared slider turtles (Trachemys scripta elegans (i.e., traditional farming for foreign and domestic pet markets, respectively. We tested the possibility of harvesting adult turtles from the breeding stock for sale to meat markets to enable alternative markets for the farmers, while decreasing the continued pressures on wild populations (i.e., non-traditional farming. Our economic model required current profit requirements of ~$13/turtle or ~$20.31/kg of meat from non-traditional farming in order to acquire the same profit as traditional farming, a value which currently exceeds market values of red-eared sliders. However, increasing competition with Asian turtle farms and decreasing hatchling prices may force the shift in the US toward producing turtles for meat markets. In addition, our model can be modified and applied to more desirable species on the meat market once more knowledge is acquired about species life histories and space requirements under farmed conditions.

Modeling Commercial Freshwater Turtle Production on US Farms for Pet and Meat Markets

Science.gov (United States)

Mali, Ivana; Wang, Hsiao-Hsuan; Grant, William E.; Feldman, Mark; Forstner, Michael R. J.

2015-01-01

Freshwater turtles are being exploited for meat, eggs, traditional medicine, and pet trade. As a response, turtle farming became a booming aquaculture industry in the past two decades, specifically in the southeastern states of the United States of America (US) and across Southeast Asia. However, US turtle farms are currently producing turtles only for the pet trade while commercial trappers remain focused on catching the largest individuals from the wild. In our analyses we have created a biological and economic model that describes farming operations on a representative turtle farm in Louisiana. We first modeled current production of hatchling and yearling red-eared slider turtles (Trachemys scripta elegans) (i.e., traditional farming) for foreign and domestic pet markets, respectively. We tested the possibility of harvesting adult turtles from the breeding stock for sale to meat markets to enable alternative markets for the farmers, while decreasing the continued pressures on wild populations (i.e., non-traditional farming). Our economic model required current profit requirements of ~$13/turtle or ~$20.31/kg of meat from non-traditional farming in order to acquire the same profit as traditional farming, a value which currently exceeds market values of red-eared sliders. However, increasing competition with Asian turtle farms and decreasing hatchling prices may force the shift in the US toward producing turtles for meat markets. In addition, our model can be modified and applied to more desirable species on the meat market once more knowledge is acquired about species life histories and space requirements under farmed conditions. PMID:26407157

Modeling Commercial Freshwater Turtle Production on US Farms for Pet and Meat Markets.

Science.gov (United States)

Mali, Ivana; Wang, Hsiao-Hsuan; Grant, William E; Feldman, Mark; Forstner, Michael R J

2015-01-01

Freshwater turtles are being exploited for meat, eggs, traditional medicine, and pet trade. As a response, turtle farming became a booming aquaculture industry in the past two decades, specifically in the southeastern states of the United States of America (US) and across Southeast Asia. However, US turtle farms are currently producing turtles only for the pet trade while commercial trappers remain focused on catching the largest individuals from the wild. In our analyses we have created a biological and economic model that describes farming operations on a representative turtle farm in Louisiana. We first modeled current production of hatchling and yearling red-eared slider turtles (Trachemys scripta elegans) (i.e., traditional farming) for foreign and domestic pet markets, respectively. We tested the possibility of harvesting adult turtles from the breeding stock for sale to meat markets to enable alternative markets for the farmers, while decreasing the continued pressures on wild populations (i.e., non-traditional farming). Our economic model required current profit requirements of ~$13/turtle or ~$20.31/kg of meat from non-traditional farming in order to acquire the same profit as traditional farming, a value which currently exceeds market values of red-eared sliders. However, increasing competition with Asian turtle farms and decreasing hatchling prices may force the shift in the US toward producing turtles for meat markets. In addition, our model can be modified and applied to more desirable species on the meat market once more knowledge is acquired about species life histories and space requirements under farmed conditions.

Multiple-criteria approach of evaluation of milk farm models in Bosnia and Herzegovina

Directory of Open Access Journals (Sweden)

Črtomir Rozman

2016-07-01

Full Text Available Cattle breeding is a very important part of agricultural production in Bosnia and Herzegovina (B&H, and milk production has a vital place in cattle breeding production. From an economic point of view, milk production is interesting as it is a daily production which presupposes faster marketing, which accelerates capital movement in agriculture, which in turn enhances liquidity. This research uses analyses of the existing state in milk production. The collected data are processed and cost calculation has been designed which enables the analysis of economic indicators of 4 dairy farm production models in B&H. Based on the collected data on features and values of dairy farm production models in B&H an analysis of expert evaluation was conducted as input data for DEXi method. The aim of this paper is to ascertain the basic indicators of business success of 4 dairy farm production models in B&H. Production-ecological, economic and socio-political features of the mentioned dairy farm models were analyzed. Based on the used criteria a rate of dairy farm production models using DEXi method was conducted. The results of the research in this paper using DEXi method show that the best model for dairy farm is model number four, which includes 45 milk cows.

Identifying key entry-points for strategic management of smallholder farming systems in sub-Saharan Africa using the dynamic farm-scale simulation model NUANCES-FARMSIM

NARCIS (Netherlands)

Wijk, van M.T.; Tittonell, P.A.; Rufino, M.C.; Herrero, M.; Pacini, C.; Ridder, de N.; Giller, K.E.

2009-01-01

African smallholder farming systems are complex, dynamic systems with many interacting biophysical subcomponents. In these systems the major inputs and outputs are managed by human agency ¿ the farmers. To analyse potential developmental pathways of smallholder farming systems in sub-Saharan Africa

Wind energy potential in Chile: Assessment of a small scale wind farm for residential clients

International Nuclear Information System (INIS)

Becerra, Miguel; Morán, José; Jerez, Alejandro; Cepeda, Francisco; Valenzuela, Miguel

2017-01-01

Highlights: • An assessment of a small scale wind farm was carried out. • Two Chilean locations were selected, which are geographically dissimilar. • The software tool selected for the project’s evaluation was HOMER. • All the project’s financial evaluations were negative. • Government policy tools and their applications were discussed. - Abstract: This work presents a techno-financial evaluation of two Chilean locations with promising wind potential: Laguna Verde placed in the central region of the country, and Porvenir in the southern region. A small scale wind farm was studied, considering a nominal electrical production capacity of 90 kW. This facility is comprised of three wind turbine models, all available in the national market. Currently, the tariff method used in Chile is the net billing scheme, where the energy bought and sold to the grid has different prices. The study is based on 300 hypothetical residential households. The software tool used to perform the assessment was the Hybrid Optimization of Multiple Energy Resources (HOMER). For all the scenarios the results showed a Net Present Cost (NPC), instead of a financial profit from the proposed projects. A sensitivity analysis was also carried out. From the group of variables studied, the NPC exhibited itself as more sensitive to the price of buying energy from the grid and to the annual average wind speed. Finally, a few government policies and their applications are discussed.

An industry-scale mass marking technique for tracing farmed fish escapees.

Directory of Open Access Journals (Sweden)

Fletcher Warren-Myers

Full Text Available Farmed fish escape and enter the environment with subsequent effects on wild populations. Reducing escapes requires the ability to trace individuals back to the point of escape, so that escape causes can be identified and technical standards improved. Here, we tested if stable isotope otolith fingerprint marks delivered during routine vaccination could be an accurate, feasible and cost effective marking method, suitable for industrial-scale application. We tested seven stable isotopes, (134Ba, (135Ba, (136Ba, (137Ba, (86Sr, (87Sr and (26Mg, on farmed Atlantic salmon reared in freshwater, in experimental conditions designed to reflect commercial practice. Marking was 100% successful with individual Ba isotopes at concentrations as low as 0.001 µg. g-1 fish and for Sr isotopes at 1 µg. g-1 fish. Our results suggest that 63 unique fingerprint marks can be made at low cost using Ba (0.0002 - 0.02 $US per mark and Sr (0.46 - 0.82 $US per mark isotopes. Stable isotope fingerprinting during vaccination is feasible for commercial application if applied at a company level within the world's largest salmon producing nations. Introducing a mass marking scheme would enable tracing of escapees back to point of origin, which could drive greater compliance, better farm design and improved management practices to reduce escapes.

Design Performance Standards for Large Scale Wind Farms

DEFF Research Database (Denmark)

Gordon, Mark

2009-01-01

of connection into the Eastern Australian power system under the Rules and guidelines set out by AEMC and NEMMCO (AEMO). Where applicable some international practices are also mentioned. Standards are designed to serve as a technical envelope under which wind farm proponents design the plant and maintain...... ongoing technical compliance of the plant during its operational lifetime. This report is designed to provide general technical information for the wind farm connection engineer to be aware of during the process of connection, registration and operation of wind power plants interconnected into the HV TSO......’s network. No special NER Rule has been used in this document, however V30 (year 2009) has been used as the latest reference on some of the topics discussed. Care has been taken to emphasise certain wind farm design and connection issues that could be considered throughout different stages of the wind farm...

Impact on food productivity by fossil fuel independence - A case study of a Swedish small-scale integrated organic farm

Energy Technology Data Exchange (ETDEWEB)

Johansson, Sheshti [Dept. of Energy and Technology, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden); Belfrage, Kristina [Centre for Sustainable Agriculture, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden); Olsson, Mats [Dept. of Soil and Environment, Swedish Univ. of Agricultural Sciences, Uppsala (Sweden)

2013-02-15

The large-scale industrial agriculture that provides the majority of food at present is dependent upon fossil fuels in the form of tractor fuel, mineral fertilizers, pesticides, and irrigation. Yet, the age of cheap and abundant fossil fuels will likely come to an end within the coming decades. In this case study, the productivity of a small-scale farm (8 ha arable land, 5.5 ha meadow, 3.5 ha pasture and 18 ha forest) independent on fossil fuels by using organic methods and draught horse power was investigated. The aim was to quantify its productivity when the animal composition and possible alternatives to tractive power were varied. After an analysis of possible solutions, three scenarios for tractive power were selected: draught horse power, diesel tractor, and combination of draught horse power and rapeseed oil fueled tractor. A model that calculates the amount of food available at the farm in terms of meat, milk egg, and crops, converts it into energy units and calculates how many people can be supplied from the farm was developed. The most reasonable of the scenarios studied was when draught horse power was combined with tractor (and combine harvester) driven on locally produced rapeseed oil. Then the farm will have access to all advantages with the tractor and harvester, e.g., timeliness in harvest and lifting heavy loads, and the renewability and efficiency of draught horse power on smaller fields, and lighter operations. This system was able to support between 66 and 82 persons depending on crop yields, milk yields, meat production, fuel demand for the tractor, and availability of forest grazing. Most likely the production capacity lands on ability to support approximately 68 - 70 persons, and the farm may require fossil fuels to support more than 80 persons. If all farmland globally was to be operated with the same productivity, this would be enough for supplying the global population with food at present.

Unstructured grid modelling of offshore wind farm impacts on seasonally stratified shelf seas

Science.gov (United States)

Cazenave, Pierre William; Torres, Ricardo; Allen, J. Icarus

2016-06-01

Shelf seas comprise approximately 7% of the world's oceans and host enormous economic activity. Development of energy installations (e.g. Offshore Wind Farms (OWFs), tidal turbines) in response to increased demand for renewable energy requires a careful analysis of potential impacts. Recent remote sensing observations have identified kilometre-scale impacts from OWFs. Existing modelling evaluating monopile impacts has fallen into two camps: small-scale models with individually resolved turbines looking at local effects; and large-scale analyses but with sub-grid scale turbine parameterisations. This work straddles both scales through a 3D unstructured grid model (FVCOM): wind turbine monopiles in the eastern Irish Sea are explicitly described in the grid whilst the overall grid domain covers the south-western UK shelf. Localised regions of decreased velocity extend up to 250 times the monopile diameter away from the monopile. Shelf-wide, the amplitude of the M2 tidal constituent increases by up to 7%. The turbines enhance localised vertical mixing which decreases seasonal stratification. The spatial extent of this extends well beyond the turbines into the surrounding seas. With significant expansion of OWFs on continental shelves, this work highlights the importance of how OWFs may impact coastal (e.g. increased flooding risk) and offshore (e.g. stratification and nutrient cycling) areas.

A SIMULATION OF CONTRACT FARMING USING AGENT BASED MODELING

Directory of Open Access Journals (Sweden)

Yuanita Handayati

2016-12-01

Full Text Available This study aims to simulate the effects of contract farming and farmer commitment to contract farming on supply chain performance by using agent based modeling as a methodology. Supply chain performance is represented by profits and service levels. The simulation results indicate that farmers should pay attention to customer requirements and plan their agricultural activities in order to fulfill these requirements. Contract farming helps farmers deal with demand and price uncertainties. We also find that farmer commitment is crucial to fulfilling contract requirements. This study contributes to this field from a conceptual as well as a practical point of view. From the conceptual point of view, our simulation results show that different levels of farmer commitment have an impact on farmer performance when implementing contract farming. From a practical point of view, the uncertainty faced by farmers and the market can be managed by implementing cultivation and harvesting scheduling, information sharing, and collective learning as ways of committing to contract farming.

Assessing the impact of marine wind farms on birds through movement modelling.

Science.gov (United States)

Masden, Elizabeth A; Reeve, Richard; Desholm, Mark; Fox, Anthony D; Furness, Robert W; Haydon, Daniel T

2012-09-07

Advances in technology and engineering, along with European Union renewable energy targets, have stimulated a rapid growth of the wind power sector. Wind farms contribute to carbon emission reductions, but there is a need to ensure that these structures do not adversely impact the populations that interact with them, particularly birds. We developed movement models based on observed avoidance responses of common eider Somateria mollissima to wind farms to predict, and identify potential measures to reduce, impacts. Flight trajectory data that were collected post-construction of the Danish Nysted offshore wind farm were used to parameterize competing models of bird movements around turbines. The model most closely fitting the observed data incorporated individual variation in the minimum distance at which birds responded to the turbines. We show how such models can contribute to the spatial planning of wind farms by assessing their extent, turbine spacing and configurations on the probability of birds passing between the turbines. Avian movement models can make new contributions to environmental assessments of wind farm developments, and provide insights into how to reduce impacts that can be identified at the planning stage.

Cost optimization of wind turbines for large-scale offshore wind farms

International Nuclear Information System (INIS)

Fuglsang, P.; Thomsen, K.

1998-02-01

This report contains a preliminary investigation of site specific design of off-shore wind turbines for a large off-shore wind farm project at Roedsand that is currently being proposed by ELKRAFT/SEAS. The results were found using a design tool for wind turbines that involve numerical optimization and aeroelastic calculations of response. The wind climate was modeled in detail and a cost function was used to estimate costs from manufacture and installation. Cost of energy is higher for off-shore installations. A comparison of an off-shore wind farm site with a typical stand alone on-shore site showed an increase of the annual production of 28% due to the difference in wind climate. Extreme loads and blade fatigue loads were nearly identical, however,fatigue loads on other main components increased significantly. Optimizations were carried out to find the optimum overall off-shore wind turbine design. A wind turbine for the off-shore wind farm should be different compared with a stand-alone on-shore wind turbine. The overall design changed were increased swept area and rated power combined with reduced rotor speed and tower height. Cost was reduced by 12% for the final 5D/14D off-shore wind turbine from 0.306 DKr/kWh to 0.270 DKr/kWh. These figures include capital costs from manufacture and installation but not on-going costs from maintenance. These results make off-shore wind farms more competitive and comparable to the reference on-shore stand-alone wind turbine. A corresponding reduction of cost of energy could not be found for the stand alone on-shore wind turbine. Furthermore the fatigue loads on wind turbines in on-shore wind farms will increase and cost of energy will increase in favor of off-shore wind farms. (au) EFP-95; EU-JOULE-3; 21 tabs., 7 ills., 8 refs

Spatiotemporal distribution of nitrogen dioxide within and around a large-scale wind farm – a numerical case study

Directory of Open Access Journals (Sweden)

J. Mo

2017-12-01

Full Text Available As a renewable and clean energy source, wind power has become the most rapidly growing energy resource worldwide in the past decades. Wind power has been thought not to exert any negative impacts on the environment. However, since a wind farm can alter the local meteorological conditions and increase the surface roughness lengths, it may affect air pollutants passing through and over the wind farm after released from their sources and delivered to the wind farm. In the present study, we simulated the nitrogen dioxide (NO2 air concentration within and around the world's largest wind farm (Jiuquan wind farm in Gansu Province, China using a coupled meteorology and atmospheric chemistry model WRF-Chem. The results revealed an edge effect, which featured higher NO2 levels at the immediate upwind and border region of the wind farm and lower NO2 concentration within the wind farm and the immediate downwind transition area of the wind farm. A surface roughness length scheme and a wind turbine drag force scheme were employed to parameterize the wind farm in this model investigation. Modeling results show that both parameterization schemes yield higher concentration in the immediate upstream of the wind farm and lower concentration within the wind farm compared to the case without the wind farm. We infer this edge effect and the spatial distribution of air pollutants to be the result of the internal boundary layer induced by the changes in wind speed and turbulence intensity driven by the rotation of the wind turbine rotor blades and the enhancement of surface roughness length over the wind farm. The step change in the roughness length from the smooth to rough surfaces (overshooting in the upstream of the wind farm decelerates the atmospheric transport of air pollutants, leading to their accumulation. The rough to the smooth surface (undershooting in the downstream of the wind farm accelerates the atmospheric transport of air pollutants, resulting in

PORFLOW Modeling Supporting The H-Tank Farm Performance Assessment

International Nuclear Information System (INIS)

Jordan, J. M.; Flach, G. P.; Westbrook, M. L.

2012-01-01

Numerical simulations of groundwater flow and contaminant transport in the vadose and saturated zones have been conducted using the PORFLOW code in support of an overall Performance Assessment (PA) of the H-Tank Farm. This report provides technical detail on selected aspects of PORFLOW model development and describes the structure of the associated electronic files. The PORFLOW models for the H-Tank Farm PA, Rev. 1 were updated with grout, solubility, and inventory changes. The aquifer model was refined. In addition, a set of flow sensitivity runs were performed to allow flow to be varied in the related probabilistic GoldSim models. The final PORFLOW concentration values are used as input into a GoldSim dose calculator

PORFLOW Modeling Supporting The H-Tank Farm Performance Assessment

Energy Technology Data Exchange (ETDEWEB)

Jordan, J. M.; Flach, G. P.; Westbrook, M. L.

2012-08-31

Numerical simulations of groundwater flow and contaminant transport in the vadose and saturated zones have been conducted using the PORFLOW code in support of an overall Performance Assessment (PA) of the H-Tank Farm. This report provides technical detail on selected aspects of PORFLOW model development and describes the structure of the associated electronic files. The PORFLOW models for the H-Tank Farm PA, Rev. 1 were updated with grout, solubility, and inventory changes. The aquifer model was refined. In addition, a set of flow sensitivity runs were performed to allow flow to be varied in the related probabilistic GoldSim models. The final PORFLOW concentration values are used as input into a GoldSim dose calculator.

Wind Farm Reliability Modelling Using Bayesian Networks and Semi-Markov Processes

Directory of Open Access Journals (Sweden)

Robert Adam Sobolewski

2015-09-01

Full Text Available Technical reliability plays an important role among factors affecting the power output of a wind farm. The reliability is determined by an internal collection grid topology and reliability of its electrical components, e.g. generators, transformers, cables, switch breakers, protective relays, and busbars. A wind farm reliability’s quantitative measure can be the probability distribution of combinations of operating and failed states of the farm’s wind turbines. The operating state of a wind turbine is its ability to generate power and to transfer it to an external power grid, which means the availability of the wind turbine and other equipment necessary for the power transfer to the external grid. This measure can be used for quantitative analysis of the impact of various wind farm topologies and the reliability of individual farm components on the farm reliability, and for determining the expected farm output power with consideration of the reliability. This knowledge may be useful in an analysis of power generation reliability in power systems. The paper presents probabilistic models that quantify the wind farm reliability taking into account the above-mentioned technical factors. To formulate the reliability models Bayesian networks and semi-Markov processes were used. Using Bayesian networks the wind farm structural reliability was mapped, as well as quantitative characteristics describing equipment reliability. To determine the characteristics semi-Markov processes were used. The paper presents an example calculation of: (i probability distribution of the combination of both operating and failed states of four wind turbines included in the wind farm, and (ii expected wind farm output power with consideration of its reliability.

Modeling and Identification of Harmonic Instability Problems In Wind Farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2016-01-01

In power electronics based power systems like wind farms, the interactions between the inner control systems of the power converters and the passive components may lead to high frequency oscillations, which can be called harmonic instability. In this paper, a simple methodology is presented...... to identify harmonic instability problems in wind farms, where many wind turbines, cables, transformers, capacitor banks, shunt reactors, etc, typically are located. This methodology introduces the wind farm as a Multi-Input Multi-Outpur (MIMO) control system, where the linearized models of fast inner control....../EMTDC software environment for a 400-MW wind farm. The proposed analytical analysis method and time-domain simulation results show that both dynamics of the power electronic converter and the parameters of the passive component can effect on the wind farm stability....

Reliability, availability and maintenance aspects of large-scale offshore wind farms, a concepts study

NARCIS (Netherlands)

Van Bussel, G.J.W.; Zaayer, M.B.

2001-01-01

The DOWEC projects aims at implementation of large wind turbines in large scale wind farms. part of the DOWEC project a concepts study was performed regarding the achievable reliability and availability levels. A reduction with a factor of 2 with regard to the present state of the art seems fairly

The Impact of Farming and Land Ownership on Soil Erosion

Directory of Open Access Journals (Sweden)

Olga Čermáková

2014-01-01

Full Text Available The aim of this paper was to compare two methods of farming, especially their effect on water soil erosion. The examined methods were (1 large-scale farming, where more than 50% of the land was leased, and (2 small-scale farming, where the land was almost exclusively privately owned. The research area was 8 cadastres in the district of Hodonín, South Moravia, Czech Republic. In these cadastres 48 land blocks representing both large-scale and small-scale farming (i.e. owners and tenants were chosen. The long-term average annual soil loss caused by water erosion (G was calculated using the erosion model USLE 2D and ArcGIS 10.1. The nonparametric Mann-Whitney test was used for the statistical evaluation of the data. The difference between the soil loss (G on land blocks farmed by small producers (owners and large producers (tenants was significant (p < 0.05. Differences between the values of the cropping-management factor (C were not statistically significant (p = 0.054. Based on the analysis of other variables in the USLE equation it can be stated that a continuous slope length, conditioned by the size of land blocks, played an important role in the amount of soil loss caused by water erosion. Above all, to protect the soil from erosion and maintain soil quality it is necessary to reduce the size of land blocks farmed by tenants and improve the crop rotation systems.

Evaluating expansion strategies for startup European Union dairy farm businesses.

Science.gov (United States)

McDonald, R; Shalloo, L; Pierce, K M; Horan, B

2013-06-01

A stochastic whole-farm simulation model was used to examine alternative strategies for new entrant dairy farmers to grow and develop dairy farm businesses in the context of European Union (EU) milk quota abolition in 2015. Six alternative strategies were compared: remain static, natural growth expansion, waiting until after EU milk quota abolition to expand, a full-scale expansion strategy without milk quotas and not incurring super levy penalties, a full-scale expansion strategy with milk quotas and incurring super levy penalties, and once-a-day milking until EU milk quota abolition, followed by full-scale expansion. Each discrete whole farm investment strategy was evaluated over a 15-yr period (2013-2027) using multiple financial stability and risk indicators, including overall discounted farm business profitability, net worth change, return on investment, and financial risk. The results of this study indicate that, although associated with increased risk, dairy farm expansion will ensure the future profitability of the farm business. Within the context of EU milk quotas until 2015, the most attractive expansion strategy is to increase cow numbers while avoiding super levy fines using once-a-day milking techniques, increasing to the full capacity of the dairy farm once milk quotas are removed. In contrast, the results also indicate that dairy farms that remain static will experience a significant reduction in farm profitability in the coming year due to production cost inflation. Cash flow deficits were observed during the initial year of expansion and, therefore, rapidly expanding dairy farm businesses require a significant cash reserve to alleviate business risk during the initial year of expansion. The results of this analysis also indicate that dairy farm businesses that expand using lower cost capital investments and avoid milk quota super levy fines significantly reduce the financial risks associated with expansion. Copyright © 2013 American Dairy Science

Modelization of a large wind farm, considering the modification of the atmospheric boundary layer

Energy Technology Data Exchange (ETDEWEB)

Crespo, A; Gomez-Elvira, R [Univ. Politecnica de Madrid, Mecanica de Fluidos, E.T.S.I. Industriales, Madrid (Spain); Frandsen, S; Larsen, S E [Risoe National Lab., Roskilde (Denmark)

1999-03-01

A method is presented to adapt existing models of wind farms to very large ones that may affect the whole planetary boundary layer. An internal boundary layer is considered that starts developing at the leading edge of the farm until it reaches, sufficiently far downstream, the top of the planetary boundary layer, and a new equilibrium region is reached. The wind farm is simulated by an artificial roughness that is function of the turbine spacing, drag and height. From this model the flow conditions are calculated at a certain reference height and then are used as boundary conditions for a numerical code used to model a wind farm. Three-dimensional effects are considered by applying appropriate conditions at the sides of the farm. Calculations are carried out to estimate the energy production in large wind farms, and it is found that additional losses due to modification of the planetary boundary layer may be of importance for wind farms of size larger than about 100 km. (au)

Wind Farm LES Simulations Using an Overset Methodology

Science.gov (United States)

Ananthan, Shreyas; Yellapantula, Shashank

2017-11-01

Accurate simulation of wind farm wakes under realistic atmospheric inflow conditions and complex terrain requires modeling a wide range of length and time scales. The computational domain can span several kilometers while requiring mesh resolutions in O(10-6) to adequately resolve the boundary layer on the blade surface. Overset mesh methodology offers an attractive option to address the disparate range of length scales; it allows embedding body-confirming meshes around turbine geomtries within nested wake capturing meshes of varying resolutions necessary to accurately model the inflow turbulence and the resulting wake structures. Dynamic overset hole-cutting algorithms permit relative mesh motion that allow this nested mesh structure to track unsteady inflow direction changes, turbine control changes (yaw and pitch), and wake propagation. An LES model with overset mesh for localized mesh refinement is used to analyze wind farm wakes and performance and compared with local mesh refinements using non-conformal (hanging node) unstructured meshes. Turbine structures will be modeled using both actuator line approaches and fully-resolved structures to test the efficacy of overset methods for wind farm applications. Exascale Computing Project (ECP), Project Number: 17-SC-20-SC, a collaborative effort of two DOE organizations - the Office of Science and the National Nuclear Security Administration.

Impacts of Small-Scale Industrialized Swine Farming on Local Soil, Water and Crop Qualities in a Hilly Red Soil Region of Subtropical China.

Science.gov (United States)

Zhang, Di; Wang, Xingxiang; Zhou, Zhigao

2017-12-06

Industrialized small-scale pig farming has been rapidly developed in developing regions such as China and Southeast Asia, but the environmental problems accompanying pig farming have not been fully recognized. This study investigated 168 small-scale pig farms and 29 example pig farms in Yujiang County of China to examine current and potential impacts of pig wastes on soil, water and crop qualities in the hilly red soil region, China. The results indicated that the small-scale pig farms produced considerable annual yields of wastes, with medians of 216, 333 and 773 ton yr -1 per pig farm for manure, urine and washing wastewater, respectively, which has had significant impact on surface water quality. Taking NH₄⁺-N, total nitrogen (TN) or total phosphorus (TP) as a criterion to judge water quality, the proportions of Class III and below Class III waters in the local surface waters were 66.2%, 78.7% and 72.5%. The well water (shallow groundwater) quality near these pig farms met the water quality standards by a wide margin. The annual output of pollutants from pig farms was the most important factor correlated with the nutrients and heavy metals in soils, and the relationship can be described by a linear equation. The impact on croplands was marked by the excessive accumulation of available phosphorus and heavy metals such as Cu and Zn. For crop safety, the over-limit ratio of Zn in vegetable samples reached 60%, other heavy metals in vegetable and rice samples tested met the food safety standard at present.

Impacts of Small-Scale Industrialized Swine Farming on Local Soil, Water and Crop Qualities in a Hilly Red Soil Region of Subtropical China

Directory of Open Access Journals (Sweden)

Di Zhang

2017-12-01

Full Text Available Industrialized small-scale pig farming has been rapidly developed in developing regions such as China and Southeast Asia, but the environmental problems accompanying pig farming have not been fully recognized. This study investigated 168 small-scale pig farms and 29 example pig farms in Yujiang County of China to examine current and potential impacts of pig wastes on soil, water and crop qualities in the hilly red soil region, China. The results indicated that the small-scale pig farms produced considerable annual yields of wastes, with medians of 216, 333 and 773 ton yr−1 per pig farm for manure, urine and washing wastewater, respectively, which has had significant impact on surface water quality. Taking NH4+-N, total nitrogen (TN or total phosphorus (TP as a criterion to judge water quality, the proportions of Class III and below Class III waters in the local surface waters were 66.2%, 78.7% and 72.5%. The well water (shallow groundwater quality near these pig farms met the water quality standards by a wide margin. The annual output of pollutants from pig farms was the most important factor correlated with the nutrients and heavy metals in soils, and the relationship can be described by a linear equation. The impact on croplands was marked by the excessive accumulation of available phosphorus and heavy metals such as Cu and Zn. For crop safety, the over-limit ratio of Zn in vegetable samples reached 60%, other heavy metals in vegetable and rice samples tested met the food safety standard at present.

Consequential environmental life cycle assessment of a farm-scale biogas plant.

Science.gov (United States)

Van Stappen, Florence; Mathot, Michaël; Decruyenaere, Virginie; Loriers, Astrid; Delcour, Alice; Planchon, Viviane; Goffart, Jean-Pierre; Stilmant, Didier

2016-06-15

Producing biogas via anaerobic digestion is a promising technology for meeting European and regional goals on energy production from renewable sources. It offers interesting opportunities for the agricultural sector, allowing waste and by-products to be converted into bioenergy and bio-based materials. A consequential life cycle assessment (cLCA) was conducted to examine the consequences of the installation of a farm-scale biogas plant, taking account of assumptions about processes displaced by biogas plant co-products (power, heat and digestate) and the uses of the biogas plant feedstock prior to plant installation. Inventory data were collected on an existing farm-scale biogas plant. The plant inputs are maize cultivated for energy, solid cattle manure and various by-products from surrounding agro-food industries. Based on hypotheses about displaced electricity production (oil or gas) and the initial uses of the plant feedstock (animal feed, compost or incineration), six scenarios were analyzed and compared. Digested feedstock previously used in animal feed was replaced with other feed ingredients in equivalent feed diets, designed to take account of various nutritional parameters for bovine feeding. The displaced production of mineral fertilizers and field emissions due to the use of digestate as organic fertilizer was balanced against the avoided use of manure and compost. For all of the envisaged scenarios, the installation of the biogas plant led to reduced impacts on water depletion and aquatic ecotoxicity (thanks mainly to the displaced mineral fertilizer production). However, with the additional animal feed ingredients required to replace digested feedstock in the bovine diets, extra agricultural land was needed in all scenarios. Field emissions from the digestate used as organic fertilizer also had a significant impact on acidification and eutrophication. The choice of displaced marginal technologies has a huge influence on the results, as have the

Combining offshore wind energy and large-scale mussel farming: background & technical, ecological and economic considerations

NARCIS (Netherlands)

Lagerveld, S.; Rockmann, C.; Scholl, M.M.; Bartelings, H.; Burg, van den S.W.K.; Jak, R.G.; Jansen, H.M.; Klijnstra, J.; Leopold, M.F.; Poelman, M.; Smith, S.R.; Stavenuiter, J.; Veenstra, F.A.; Veltman, C.; Westra, C.

2014-01-01

This Blauwdruk project report presents background and technical, ecological and economic considerations of the potential combination of offshore wind energy production and large-scale mussel farming in offshore areas in the North Sea. The main objective of the Blauwdruk project was to study the

Comparison of the effectiveness of analytical wake models for wind farm with constant and variable hub heights

International Nuclear Information System (INIS)

Wang, Longyan; Tan, Andy C.C.; Cholette, Michael; Gu, Yuantong

2016-01-01

Highlights: • The effectiveness of three analytical wake models is studied. • The results of the analytical wake models are compared with the CFD simulations. • The results of CFD simulation are verified by comparison to the offshore wind farm observation data. • The onshore wind farm with both constant and different hub height turbines are analyzed. • PARK model is able to predict the total wind farm power production well with tuned surface roughness value. - Abstract: Extensive power losses of wind farm have been witnessed due to the wake interactions between wind turbines. By applying analytical wake models which describe the wind speed deficits in the wake quantitatively, the power losses can be regained to a large extent through wind farm layout optimization, and this has been extensively reported in literature. Nevertheless, the effectiveness of the analytical wake models in predicting the wind farm power production have rarely been studied and compared for wind farm with both constant and variable wind turbine hub heights. In this study, the effectiveness of three different analytical wake models (PARK model, Larsen model and B-P model) is thoroughly compared over a wide range of wake properties. After the validation with the observation data from offshore wind farm, CFD simulations are used to verify the effectiveness of the analytical wake models for an onshore wind farm. The results show that when using the PARK model the surface roughness value (z 0 ) must be carefully tuned to achieve good performance in predicting the wind farm power production. For the other two analytical wake models, their effectiveness varies depending on the situation of wind farm (offshore or onshore) and the wind turbine hub heights (constant or variable). It was found that the results of B-P model agree well with the CFD simulations for offshore wind farm, but not for the onshore wind farm. The Larsen model is more accurate for the wind farm with variable wind turbine

A farm-scale pilot plant for biohydrogen and biomethane production by two-stage fermentation

Directory of Open Access Journals (Sweden)

R. Oberti

2013-09-01

Full Text Available Hydrogen is considered one of the possible main energy carriers for the future, thanks to its unique environmental properties. Indeed, its energy content (120 MJ/kg can be exploited virtually without emitting any exhaust in the atmosphere except for water. Renewable production of hydrogen can be obtained through common biological processes on which relies anaerobic digestion, a well-established technology in use at farm-scale for treating different biomass and residues. Despite two-stage hydrogen and methane producing fermentation is a simple variant of the traditional anaerobic digestion, it is a relatively new approach mainly studied at laboratory scale. It is based on biomass fermentation in two separate, seuqential stages, each maintaining conditions optimized to promote specific bacterial consortia: in the first acidophilic reactorhydrogen is produced production, while volatile fatty acids-rich effluent is sent to the second reactor where traditional methane rich biogas production is accomplished. A two-stage pilot-scale plant was designed, manufactured and installed at the experimental farm of the University of Milano and operated using a biomass mixture of livestock effluents mixed with sugar/starch-rich residues (rotten fruits and potatoes and expired fruit juices, afeedstock mixture based on waste biomasses directly available in the rural area where plant is installed. The hydrogenic and the methanogenic reactors, both CSTR type, had a total volume of 0.7m3 and 3.8 m3 respectively, and were operated in thermophilic conditions (55 2 °C without any external pH control, and were fully automated. After a brief description of the requirements of the system, this contribution gives a detailed description of its components and of engineering solutions to the problems encountered during the plant realization and start-up. The paper also discusses the results obtained in a first experimental run which lead to production in the range of previous

Certified safe farm: identifying and removing hazards on the farm.

Science.gov (United States)

Rautiainen, R H; Grafft, L J; Kline, A K; Madsen, M D; Lange, J L; Donham, K J

2010-04-01

This article describes the development of the Certified Safe Farm (CSF) on-farm safety review tools, characterizes the safety improvements among participating farms during the study period, and evaluates differences in background variables between low and high scoring farms. Average farm review scores on 185 study farms improved from 82 to 96 during the five-year study (0-100 scale, 85 required for CSF certification). A total of 1292 safety improvements were reported at an estimated cost of $650 per farm. A wide range of improvements were made, including adding 9 rollover protective structures (ROPS), 59 power take-off (PTO) master shields, and 207 slow-moving vehicle (SMV) emblems; improving lighting on 72 machines: placing 171 warning decals on machinery; shielding 77 moving parts; locking up 17 chemical storage areas, adding 83 lockout/tagout improvements; and making general housekeeping upgrades in 62 farm buildings. The local, trained farm reviewers and the CSF review process overall were well received by participating farmers. In addition to our earlier findings where higher farm review scores were associated with lower self-reported health outcome costs, we found that those with higher farm work hours, younger age, pork production in confinement, beef production, poultry production, and reported exposure to agrichemicals had higher farm review scores than those who did not have these characteristics. Overall, the farm review process functioned as expected. encouraging physical improvements in the farm environment, and contributing to the multi-faceted CSF intervention program.

Whole farm quantification of GHG emissions within smallholder farms in developing countries

International Nuclear Information System (INIS)

Seebauer, Matthias

2014-01-01

The IPCC has compiled the best available scientific methods into published guidelines for estimating greenhouse gas emissions and emission removals from the land-use sector. In order to evaluate existing GHG quantification tools to comprehensively quantify GHG emissions and removals in smallholder conditions, farm scale quantification was tested with farm data from Western Kenya. After conducting a cluster analysis to identify different farm typologies GHG quantification was exercised using the VCS SALM methodology complemented with IPCC livestock emission factors and the cool farm tool. The emission profiles of four farm clusters representing the baseline conditions in the year 2009 are compared with 2011 where farmers adopted sustainable land management practices (SALM). The results demonstrate the variation in both the magnitude of the estimated GHG emissions per ha between different smallholder farm typologies and the emissions estimated by applying two different accounting tools. The farm scale quantification further shows that the adoption of SALM has a significant impact on emission reduction and removals and the mitigation benefits range between 4 and 6.5 tCO 2  ha −1  yr −1 with significantly different mitigation benefits depending on typologies of the crop–livestock systems, their different agricultural practices, as well as adoption rates of improved practices. However, the inherent uncertainty related to the emission factors applied by accounting tools has substantial implications for reported agricultural emissions. With regard to uncertainty related to activity data, the assessment confirms the high variability within different farm types as well as between different parameters surveyed to comprehensively quantify GHG emissions within smallholder farms. (paper)

Farming for a Better Climate by Improving Nitrogen Use Efficiency and Reducing Greenhouse Gas Emissions (FarmClim)

Science.gov (United States)

Amon, Barbara; Winiwarter, Wilfried; Schröck, Andrea; Zechmeister-Boltenstern, Sophie; Kasper, Martina; Sigmund, Elisabeth; Schaller, Lena; Moser, Tobias; Baumgarten, Andreas; Dersch, Georg; Zethner, Gerhard; Anderl, Michael; Kitzler, Barbara

2014-05-01

The project FarmClim (Farming for a better climate) assesses impacts of agriculture on N and GHG fluxes in Austria and proposes measures for improving N efficiency and mitigating emissions, including their economic assessment. This paper focuses on animal husbandry and crop production measures, and on N2O emissions from soils. FarmClim applies national inventory reporting methods to assess Austrian NH3 and GHG fluxes in order to develop flux estimates with implementation of mitigation measures. Based on scientific literature and on the outcome of the Austrian working group agriculture and climate protection a list of potential mitigation measures has been produced: phase feeding, dairy cattle diet, biogas production. Data cover resulting production levels as well as GHG mitigation. In crop production, an optimisation potential remains with respect to N fertilization and nutrient uptake efficiency. Projected regional yield data and information on the N content of arable crops have been delivered from field experiments. These data complement official statistics and allow assessing the effect of increasing proportions of legume crops in crop rotations and reducing fertilizer input on a regional scale. Economic efficiency of measures is a crucial factor for their future implementation on commercial farms. The economic model evaluates investment costs as well as changes in direct costs, labour costs and economic yield. Biophysical modelling with Landscape DNDC allows establishing a framework to move from the current approach of applying the IPCC default emission factor for N2O emissions from soils. We select two Austrian model regions to calculate N fluxes taking into account region and management practices. Hot spots and hot moments as well as mitigation strategies are identified. Two test regions have been identified for soil emission modelling. The Marchfeld is an intensively used agricultural area in North-East Austria with very fertile soils and dry climate. The

A simple rule based model for scheduling farm management operations in SWAT

Science.gov (United States)

Schürz, Christoph; Mehdi, Bano; Schulz, Karsten

2016-04-01

For many interdisciplinary questions at the watershed scale, the Soil and Water Assessment Tool (SWAT; Arnold et al., 1998) has become an accepted and widely used tool. Despite its flexibility, the model is highly demanding when it comes to input data. At SWAT's core the water balance and the modeled nutrient cycles are plant growth driven (implemented with the EPIC crop growth model). Therefore, land use and crop data with high spatial and thematic resolution, as well as detailed information on cultivation and farm management practices are required. For many applications of the model however, these data are unavailable. In order to meet these requirements, SWAT offers the option to trigger scheduled farm management operations by applying the Potential Heat Unit (PHU) concept. The PHU concept solely takes into account the accumulation of daily mean temperature for management scheduling. Hence, it contradicts several farming strategies that take place in reality; such as: i) Planting and harvesting dates are set much too early or too late, as the PHU concept is strongly sensitivity to inter-annual temperature fluctuations; ii) The timing of fertilizer application, in SWAT this often occurs simultaneously on the same date in in each field; iii) and can also coincide with precipitation events. Particularly, the latter two can lead to strong peaks in modeled nutrient loads. To cope with these shortcomings we propose a simple rule based model (RBM) to schedule management operations according to realistic farmer management practices in SWAT. The RBM involves simple strategies requiring only data that are input into the SWAT model initially, such as temperature and precipitation data. The user provides boundaries of time periods for operation schedules to take place for all crops in the model. These data are readily available from the literature or from crop variety trials. The RBM applies the dates by complying with the following rules: i) Operations scheduled in the

Management of broadleaved weeds in small-scale in an on-farm perspective

International Nuclear Information System (INIS)

Ooro, P.A.; Kamwaga, J.N.; Kipkemoi, P.L.; Bor, P.K.; Mbanda, G.O.; Rogoncho; Ochieng', J.O.

2001-01-01

An on-farm trial was conducted at eight different sites in Rongai and Njoro areas of Nakuru district and only six of the sites were finally harvested. The study was mainly to evaluate different weed control methods to offer a variety of recommendations for small scale wheat farmers. Of the treatments tested Buctril Mc out performed all the treatments except for Ariane. Cultural methods of control seemed to be inferior to almost all the chemical control. (author)

On-farm characteristics and biosecurity protocols for small-scale swine producers in eastern Australia.

Science.gov (United States)

Schembri, N; Hernandez-Jover, M; Toribio, J-A L M L; Holyoake, P K

2015-01-01

Pigs are considered high risk for the introduction and spread of foot and mouth disease (FMD) in Australia. Facilities where animals from different origins are commingled, such as saleyards, pose a high risk for disease spread. Sound on-farm management practices and biosecurity protocols are the first line of defence against a potential on-farm disease outbreak. This study evaluated the practices of 104 producers (vendors who sold pigs and purchasers of live pigs for grow-out) who traded pigs at 6 peri-urban and rural saleyards in eastern Australia. Specifically, management and on-farm biosecurity practices were assessed using an in-depth questionnaire. Univariable and multivariable logistic regression analyses were used to investigate (1) producer associations: producer type, State, motivation to keep pigs, farm type, gender, years having owned pigs, and the acquisition of formal livestock qualifications; and (2) pig associations: herd size, housing, management (husbandry and feeding) practices and biosecurity (including pig movement) practices. Backyard operations (Motivation for keeping pigs was significantly associated with a number of biosecurity practices. Producers who kept pigs for primary income were more likely to provide footwear precautions (P=0.007) and ask visitors about prior pig contacts (P=0.004). Approximately 40% of backyard and small-scale producers reported not having any quarantine practices in place for incoming pigs, compared to only 9.1% among larger producers. The main reasons cited for not adopting on-farm biosecurity practices in this study included having no need on their property (43.1%) and a lack of information and support (by the industry and/or authorities; 18.5%). Up to three-quarters of all producers maintained an open breeding herd, regularly introducing new pigs to the main herd. Saleyards are an important source of income for backyard and small-scale producers as well as an important risk factor for the introduction and

Summary Report: The Shadow effect of large wind farms: measurements, data analysis and modelling

DEFF Research Database (Denmark)

Frandsen, Sten Tronæs; Barthelmie, Rebecca Jane; Rathmann, Ole

It was the goal of the project – by means of data from the demonstration wind farms Horns Rev and Nysted, analyses of these data and modelling – to facilitate prediction of the power losses from a wind farm should a new wind farm be built upwind relative to the prevailing wind direction...... it may appropriate to build new wind farms rather close to the existing wind farms. A relevant question is therefore how far away new wind farms must be placed to avoid too large power losses. Measurements have been carried out for several years at the two sites, and databases have been prepared....... Thus, if different modelling efforts results in comparable results, the quality of the models will be tested outside the physical range where data are available. All considered the project participants find that the project has been immensely successful. The main achievements of the project are...

Metabolic Profile and Inflammatory Responses in Dairy Cows with Left Displaced Abomasum Kept under Small-Scaled Farm Conditions

Directory of Open Access Journals (Sweden)

Fenja Klevenhusen

2015-10-01

Full Text Available Left displaced abomasum (LDA is a severe metabolic disease of cattle with a strong negative impact on production efficiency of dairy farms. Metabolic and inflammatory alterations associated with this disease have been reported in earlier studies, conducted mostly in large dairy farms. This research aimed to: (1 evaluate metabolic and inflammatory responses in dairy cows affected by LDA in small-scaled dairy farms; and (2 establish an Animals 2015, 5 1022 association between lactation number and milk production with the outcome of metabolic variables. The cows with LDA had lower serum calcium (Ca, but greater concentrations of non-esterified fatty acids (NEFA and beta-hydroxy-butyrate (BHBA, in particular when lactation number was >2. Cows with LDA showed elevated levels of aspartate aminotransferase, glutamate dehydrogenase, and serum amyloid A (SAA, regardless of lactation number. In addition, this study revealed strong associations between milk yield and the alteration of metabolic profile but not with inflammation in the sick cows. Results indicate metabolic alterations, liver damage, and inflammation in LDA cows kept under small-scale farm conditions. Furthermore, the data suggest exacerbation of metabolic profile and Ca metabolism but not of inflammation and liver health with increasing lactation number and milk yield in cows affected by LDA.

Metabolic Profile and Inflammatory Responses in Dairy Cows with Left Displaced Abomasum Kept under Small-Scaled Farm Conditions.

Science.gov (United States)

Klevenhusen, Fenja; Humer, Elke; Metzler-Zebeli, Barbara; Podstatzky-Lichtenstein, Leopold; Wittek, Thomas; Zebeli, Qendrim

2015-10-13

Left displaced abomasum (LDA) is a severe metabolic disease of cattle with a strong negative impact on production efficiency of dairy farms. Metabolic and inflammatory alterations associated with this disease have been reported in earlier studies, conducted mostly in large dairy farms. This research aimed to: (1) evaluate metabolic and inflammatory responses in dairy cows affected by LDA in small-scaled dairy farms; and (2) establish an Animals 2015, 5 1022 association between lactation number and milk production with the outcome of metabolic variables. The cows with LDA had lower serum calcium (Ca), but greater concentrations of non-esterified fatty acids (NEFA) and beta-hydroxy-butyrate (BHBA), in particular when lactation number was >2. Cows with LDA showed elevated levels of aspartate aminotransferase, glutamate dehydrogenase, and serum amyloid A (SAA), regardless of lactation number. In addition, this study revealed strong associations between milk yield and the alteration of metabolic profile but not with inflammation in the sick cows. Results indicate metabolic alterations, liver damage, and inflammation in LDA cows kept under small-scale farm conditions. Furthermore, the data suggest exacerbation of metabolic profile and Ca metabolism but not of inflammation and liver health with increasing lactation number and milk yield in cows affected by LDA.

Reducing Harmonic Instability and Resonance Problems in PMSG Based Wind Farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2018-01-01

Unlike conventional power systems where harmonic resonances are coming from passive inductive and capacitive elements, large-scale power electronic systems like wind farms present a more complex system, where the fast dynamics of the power electronic converters may present an inductive or capacit......Unlike conventional power systems where harmonic resonances are coming from passive inductive and capacitive elements, large-scale power electronic systems like wind farms present a more complex system, where the fast dynamics of the power electronic converters may present an inductive...... or capacitive behavior. Therefore, the interactions between the fast controllers of the power converters and the passive elements may lead to harmonic instability and new resonances at various frequencies. This paper presents an optimum design technique for the Wind Turbine (WT) inner controllers in a PMSG...... based wind farm in order to reduce the number of resonances and to mitigate harmonic instability. In the approach, a PMSG based wind farm is modeled as a Multi-Input Multi-Output (MIMO) dynamic system by modeling the high bandwidth control loops of the power converters. Resonance frequencies...

Modelling and transient stability of large wind farms

DEFF Research Database (Denmark)

Akhmatov, Vladislav; Knudsen, Hans; Nielsen, Arne Hejde

2003-01-01

by a physical model of grid-connected windmills. The windmill generators ate conventional induction generators and the wind farm is ac-connected to the power system. Improvements-of short-term voltage stability in case of failure events in the external power system are treated with use of conventional generator...... technology. This subject is treated as a parameter study with respect to the windmill electrical and mechanical parameters and with use of control strategies within the conventional generator technology. Stability improvements on the wind farm side of the connection point lead to significant reduction...

Towards uncovering the structure of power fluctuations of wind farms.

Science.gov (United States)

Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P

2017-12-01

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations Φ_{P} exhibit a power-law decay proportional to f^{-5/3-2} in the region corresponding to the turbulence inertial subrange and at relatively large scales, Φ_{P}∼f^{-2}. Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

Modeling Parasite Dynamics on Farmed Salmon for Precautionary Conservation Management of Wild Salmon

Science.gov (United States)

Rogers, Luke A.; Peacock, Stephanie J.; McKenzie, Peter; DeDominicis, Sharon; Jones, Simon R. M.; Chandler, Peter; Foreman, Michael G. G.; Revie, Crawford W.; Krkošek, Martin

2013-01-01

Conservation management of wild fish may include fish health management in sympatric populations of domesticated fish in aquaculture. We developed a mathematical model for the population dynamics of parasitic sea lice (Lepeophtheirus salmonis) on domesticated populations of Atlantic salmon (Salmo salar) in the Broughton Archipelago region of British Columbia. The model was fit to a seven-year dataset of monthly sea louse counts on farms in the area to estimate population growth rates in relation to abiotic factors (temperature and salinity), local host density (measured as cohort surface area), and the use of a parasiticide, emamectin benzoate, on farms. We then used the model to evaluate management scenarios in relation to policy guidelines that seek to keep motile louse abundance below an average three per farmed salmon during the March–June juvenile wild Pacific salmon (Oncorhynchus spp.) migration. Abiotic factors mediated the duration of effectiveness of parasiticide treatments, and results suggest treatment of farmed salmon conducted in January or early February minimized average louse abundance per farmed salmon during the juvenile wild salmon migration. Adapting the management of parasites on farmed salmon according to migrations of wild salmon may therefore provide a precautionary approach to conserving wild salmon populations in salmon farming regions. PMID:23577082

Modeling parasite dynamics on farmed salmon for precautionary conservation management of wild salmon.

Directory of Open Access Journals (Sweden)

Luke A Rogers

Full Text Available Conservation management of wild fish may include fish health management in sympatric populations of domesticated fish in aquaculture. We developed a mathematical model for the population dynamics of parasitic sea lice (Lepeophtheirus salmonis on domesticated populations of Atlantic salmon (Salmo salar in the Broughton Archipelago region of British Columbia. The model was fit to a seven-year dataset of monthly sea louse counts on farms in the area to estimate population growth rates in relation to abiotic factors (temperature and salinity, local host density (measured as cohort surface area, and the use of a parasiticide, emamectin benzoate, on farms. We then used the model to evaluate management scenarios in relation to policy guidelines that seek to keep motile louse abundance below an average three per farmed salmon during the March-June juvenile wild Pacific salmon (Oncorhynchus spp. migration. Abiotic factors mediated the duration of effectiveness of parasiticide treatments, and results suggest treatment of farmed salmon conducted in January or early February minimized average louse abundance per farmed salmon during the juvenile wild salmon migration. Adapting the management of parasites on farmed salmon according to migrations of wild salmon may therefore provide a precautionary approach to conserving wild salmon populations in salmon farming regions.

Pollen-mediated gene flow and seed exchange in small-scale Zambian maize farming, implications for biosafety assessment.

Science.gov (United States)

Bøhn, Thomas; Aheto, Denis W; Mwangala, Felix S; Fischer, Klara; Bones, Inger Louise; Simoloka, Christopher; Mbeule, Ireen; Schmidt, Gunther; Breckling, Broder

2016-10-03

Gene flow in agricultural crops is important for risk assessment of genetically modified (GM) crops, particularly in countries with a large informal agricultural sector of subsistence cultivation. We present a pollen flow model for maize (Zea mays), a major staple crop in Africa. We use spatial properties of fields (size, position) in three small-scale maize farming communities in Zambia and estimate rates of cross-fertilisation between fields sown with different maize varieties (e.g. conventional and transgene). As an additional factor contributing to gene flow, we present data on seed saving and sharing among farmers that live in the same communities. Our results show that: i) maize fields were small and located in immediate vicinity of neighboring fields; ii) a majority of farmers saved and shared seed; iii) modeled rates of pollen-mediated gene flow showed extensive mixing of germplasm between fields and farms and iv) as a result, segregation of GM and non-GM varieties is not likely to be an option in these systems. We conclude that the overall genetic composition of maize, in this and similar agricultural contexts, will be strongly influenced both by self-organised ecological factors (pollen flow), and by socially mediated intervention (seed recycling and sharing).

Diffusion of a Sustainable Farming Technique in Sri Lanka: An Agent-Based Modeling Approach

Science.gov (United States)

Jacobi, J. H.; Gilligan, J. M.; Carrico, A. R.; Truelove, H. B.; Hornberger, G.

2012-12-01

We live in a changing world - anthropogenic climate change is disrupting historic climate patterns and social structures are shifting as large scale population growth and massive migrations place unprecedented strain on natural and social resources. Agriculture in many countries is affected by these changes in the social and natural environments. In Sri Lanka, rice farmers in the Mahaweli River watershed have seen increases in temperature and decreases in precipitation. In addition, a government led resettlement project has altered the demographics and social practices in villages throughout the watershed. These changes have the potential to impact rice yields in a country where self-sufficiency in rice production is a point of national pride. Studies of the climate can elucidate physical effects on rice production, while research on social behaviors can illuminate the influence of community dynamics on agricultural practices. Only an integrated approach, however, can capture the combined and interactive impacts of these global changes on Sri Lankan agricultural. As part of an interdisciplinary team, we present an agent-based modeling (ABM) approach to studying the effects of physical and social changes on farmers in Sri Lanka. In our research, the diffusion of a sustainable farming technique, the system of rice intensification (SRI), throughout a farming community is modeled to identify factors that either inhibit or promote the spread of a more sustainable approach to rice farming. Inputs into the ABM are both physical and social and include temperature, precipitation, the Palmer Drought Severity Index (PDSI), community trust, and social networks. Outputs from the ABM demonstrate the importance of meteorology and social structure on the diffusion of SRI throughout a farming community.

Hydrologic Modeling of Conservation Farming Practices on the Palouse

Science.gov (United States)

van Wie, J.; Adam, J. C.; Ullman, J.

2009-12-01

The production of dryland crops such as wheat and barley in a semi-arid region requires a reliable and adequate water supply. This supply of water available for crop use is of heightened importance in areas such as the Palouse region of eastern Washington and northern Idaho where the majority of annual rainfall occurs during the winter months and must be retained in the soil through the dry summer growing season. Farmers can increase conservation of water at the field and watershed scales through the adoption of best management practices that incorporate tillage and crop residue management. This research analyzes conservation farming practices that may be implemented by representing them in a watershed-scale hydrologic model in order to determine whether these practices will effectively save water so that a stable crop yield may be insured. The Distributed Hydrology Soil Vegetation Model (DHSVM) is applied and calibrated to represent the physical changes to infiltration, evaporation, and runoff that result from altered soil and vegetation characteristics brought on by management practices. The model is calibrated with field observations at the basin scale as well as the point scale over individual plots that are under various implementations of conservation management scenarios. Conservation practices are accounted for in DHSVM by adjusting input parameters such as the porosity, roughness, and hydraulic conductivity of the soil to characterize varying levels of tillage. Vegetation parameters such as leaf area index and albedo are altered to represent different amounts of crop residue left on the field through the winter months. After calibration, the model is applied over the entire basin under scenarios representing traditional agricultural methods and a region-wide shift to conservation practices. The resulting water balance suggests that there is a potential to retain water in the seed-zone during the winter months by decreasing evaporation and runoff through

Productive, economic and environmental effects of optimised feeding strategies in small-scale dairy farms in the Highlands of Mexico

Directory of Open Access Journals (Sweden)

José Velarde-Guillén

2017-06-01

Full Text Available Since most dairy production in developing countries comes from small farms, there is scope to reduce their contribution to greenhouse gas (GHG emissions. In the highlands of Mexico, the limitations in these systems are high feeding costs. This paper assessed the production, economics and estimated methane emissions from traditional feeding strategies (TFS in 22 small-scale dairy farms compared to optimised feeding strategies (OFS evaluated through on-farm research in eight participating farms in the dry (DS and in the rainy (RS seasons. Results were analysed with a completely randomized design. There were no differences (P>0.05 in milk fat, body condition score (BCS or live weight between TFS and OFS, but there was higher (P

Enlarging of scale in dairy farming: Consequences for farm-bound traffic flows in the countryside

NARCIS (Netherlands)

Jaarsma, C.F.; Hermans, C.M.L.; Rienks, W.A.; Vries, de J.R.

2013-01-01

On average, farm units in the EU countryside are developing within the globalization process to an everincreasing physical and operational size. Within the last three decades, Dutch dairy farm holdings have increased their physical size by a factor of 3. This ongoing process can also be observed in

Canadian Whole-Farm Model Holos - Development, Stakeholder Involvement, and Model Application

Science.gov (United States)

Kroebel, R.; Janzen, H.; Beauchemin, K. A.

2017-12-01

Agriculture and Agri-Food Canada's Holos model, based mostly on emission factors, aims to explore the effect of management on Canadian whole-farm greenhouse gas emissions. The model includes 27 commonly grown annual and perennial crops, summer fallow, grassland, and 8 types of tree plantings, along with beef, dairy, sheep, swine and other livestock or poultry operations. Model outputs encompass net emissions of CO2, CH4, and N2O (in CO2 equivalents), calculated for various farm components. Where possible, algorithms are drawn from peer-reviewed publications. For consistency, Holos is aligned with the Canadian sustainability indicator and national greenhouse gas inventory objectives. Although primarily an exploratory tool for research, the model's design makes it accessible and instructive also to agricultural producers, educators, and policy makers. Model development, therefore, proceeds iteratively, with extensive stakeholder feedback from training sessions or annual workshops. To make the model accessible to diverse users, the team developed a multi-layered interface, with general farming scenarios for general use, but giving access to detailed coefficients and assumptions to researchers. The model relies on extensive climate, soil, and agronomic databases to populate regionally-applicable default values thereby minimizing keyboard entries. In an initial application, the model was used to assess greenhouse gas emissions from the Canadian beef production system; it showed that enteric methane accounted for 63% of total GHG emissions and that 84% of emissions originated from the cow-calf herd. The model further showed that GHG emission intensity per kg beef, nationally, declined by 14% from 1981 to 2011, owing to gains in production efficiency. Holos is now being used to consider further potential advances through improved rations or other management options. We are now aiming to expand into questions of grazing management, and are developing a novel carbon

Towards a deeper understanding of parenting on farms: A qualitative study.

Science.gov (United States)

Elliot, Valerie; Cammer, Allison; Pickett, William; Marlenga, Barbara; Lawson, Joshua; Dosman, James; Hagel, Louise; Koehncke, Niels; Trask, Catherine

2018-01-01

Children living on farms experience exceptionally high risks for traumatic injury. There is a large body of epidemiological research documenting this phenomenon, yet few complementary studies that have explored the deep underlying reasons for such trends. Fundamental to this is understanding the decision-making processes of parents surrounding their choice to bring children, or not, into the farm worksite. To (1) document farm parent views of the risks and benefits of raising children on a family farm, and, (2) understand more deeply why children are brought into the farm worksite. Interviews were conducted as part of a larger cohort study, The Saskatchewan Farm Injury Cohort. Subsequent to an initial mail-out question focused on parental decision-making, 11 semi-structured telephone interviews were conducted with rural Saskatchewan farm parents. Interviews were digitally recorded and transcribed verbatim, then thematically analyzed using interpretive description methodology. This parental decision-making process on farms fundamentally involves weighing the risks vs. benefits of bringing children into the worksite, as if on a balance scale. One side of this scale holds potential risks such as exposure to physical and chemical farm hazards, in the absence of full supervision. The other side holds potential benefits such as meeting family needs for childcare, labour, and family time; building work ethic and pride; and the positive impacts of involvement and responsibility. Decision-making 'tips the scales', in part dependent upon parental perceptions of the risk-benefit trade-off. This 'perceptual lens' is influenced by factors such as: the agricultural way of life, parents' prior knowledge and past experience, characteristics of children, and safety norms. This novel qualitative study provides deep insight into how Saskatchewan farm parents approach a fundamental decision-making process associated with their parenting. The proposed model provides insight into the

Raising surface water levels in peat areas with dairy farming upscaling hydrological, agronomical and economic effects from farm-scale to local scale.

NARCIS (Netherlands)

Vos, de J.A.; Bakel, van P.J.T.; Hoving, I.E.; Smidt, R.A.

2010-01-01

Raising surface water levels in peat areas is a measure to reduce soil subsidence, to prevent decay of wooden foundations and to stimulate wet nature restoration and reduce greenhouse gas emissions. However, in these areas dairy farms are present and farming at wetter soils is difficult due to lower

Multiregional input-output model for China's farm land and water use.

Science.gov (United States)

Guo, Shan; Shen, Geoffrey Qiping

2015-01-06

Land and water are the two main drivers of agricultural production. Pressure on farm land and water resources is increasing in China due to rising food demand. Domestic trade affects China's regional farm land and water use by distributing resources associated with the production of goods and services. This study constructs a multiregional input-output model to simultaneously analyze China's farm land and water uses embodied in consumption and interregional trade. Results show a great similarity for both China's farm land and water endowments. Shandong, Henan, Guangdong, and Yunnan are the most important drivers of farm land and water consumption in China, even though they have relatively few land and water resource endowments. Significant net transfers of embodied farm land and water flows are identified from the central and western areas to the eastern area via interregional trade. Heilongjiang is the largest farm land and water supplier, in contrast to Shanghai as the largest receiver. The results help policy makers to comprehensively understand embodied farm land and water flows in a complex economy network. Improving resource utilization efficiency and reshaping the embodied resource trade nexus should be addressed by considering the transfer of regional responsibilities.

Atmospheric stability-dependent infinite wind-farm models and the wake-decay coefficient

OpenAIRE

Peña, Alfredo; Rathmann, Ole

2014-01-01

We extend the infinite wind-farm boundary-layer (IWFBL) model of Frandsen to take into account atmospheric static stability effects. This extended model is compared with the IWFBL model of Emeis and to the Park wake model used inWind Atlas Analysis and Application Program (WAsP), which is computed for an infinite wind farm. The models show similar behavior for the wind-speed reduction when accounting for a number of surface roughness lengths, turbine to turbine separations and wind speeds und...

Potential market of wind farm in China

Energy Technology Data Exchange (ETDEWEB)

Pengfei Shi [Hydropower Planning General Inst., Beijing (China)

1996-12-31

Wind energy resources are abundant in China, in southeast coast area along with the rapid economic growth, electricity demand has been sharply increased, due to complex terrain detailed assessments are in urgent need. Advanced methodology and computer model should be developed. In this paper the existing wind farms, installed capacity, manufacturers share and projects in the near future are presented. For further development of wind farm in large scale, different ways of local manufacturing wind turbine generators (WTG) are going on. Current policy and barriers are analyzed. 4 refs., 2 figs., 4 tabs.

Farm-scale thermophilic co-digestion of dairy manure with a biodiesel byproduct in cold regions

International Nuclear Information System (INIS)

Andriamanohiarisoamanana, Fetra J.; Yamashiro, Takaki; Ihara, Ikko; Iwasaki, Masahiro; Nishida, Takehiro; Umetsu, Kazutaka

2016-01-01

Highlights: • Co-digestion of dairy manure and crude glycerin was conducted using a 60 m"3 reactor. • The highest methane yield was 0.323 m"3/kgVS obtained at 4.2% (v/v) of crude glycerin. • The optimum organic loading rate for crude glycerol was 1.32 kgVS_C_G/m"3 d. • Reactor energy self-sufficiency was observed with net energy output of 25 kW h/d. - Abstract: Conversion of organic wastes into applicable energy sources is the best way to improve organic waste management. In this study, the performance of thermophilic co-digestion of dairy manure (DM) and crude glycerol (CG) in a 60-m"3 farm-scale biogas digester located in a cold region was investigated during the winter. Compared to the anaerobic digestion of DM alone, the methane production increased by approximately twofold during co-digestion of DM and CG. The highest methane yield was 0.323 m"3/kgVS obtained at 4.2% (v/v) of CG. Despite the increase in methane production with organic loading rate, the methane yield of CG reduced remarkably at 2.64 kgVS_C_G/m"3 d, while the highest was at 1.32 kgVS_C_G/m"3 d. During the co-digestion, a net energy at an average of 25 kWh/d was obtained for farm operation, whereas a supply of kerosene and electricity from national grid were required for the digester and farm operations during anaerobic digestion of DM. During winter, the improvement of biogas yield through the addition of CG enabled the sustainability of a farm-scale biogas production system and reduced its environmental impact.

Stackelberg Game Model of Wind Farm and Electric Vehicle Battery Switch Station

Science.gov (United States)

Jiang, Zhe; Li, Zhimin; Li, Wenbo; Wang, Mingqiang; Wang, Mengxia

2017-05-01

In this paper, a cooperation method between wind farm and Electric vehicle battery switch station (EVBSS) was proposed. In the pursuit of maximizing their own benefits, the cooperation between wind farm and EVBSS was formulated as a Stackelberg game model by treating them as decision makers in different status. As the leader, wind farm will determine the charging/discharging price to induce the charging and discharging behavior of EVBSS reasonably. Through peak load shifting, wind farm could increase its profits by selling more wind power to the power grid during time interval with a higher purchase price. As the follower, EVBSS will charge or discharge according to the price determined by wind farm. Through optimizing the charging /discharging strategy, EVBSS will try to charge with a lower price and discharge with a higher price in order to increase its profits. Since the possible charging /discharging strategy of EVBSS is known, the wind farm will take the strategy into consideration while deciding the charging /discharging price, and will adjust the price accordingly to increase its profits. The case study proved that the proposed cooperation method and model were feasible and effective.

Is the increase of scale in the tropics a pathway to smallholders? Dimension and ecological zone effect on the mixed crop-livestock farms

Energy Technology Data Exchange (ETDEWEB)

Rangel, J.; Espinosa, J.A.; Pablos-Heredero, C. de; Rivas, J.; Perea, J.; Angón, E.; García-Martínez, A.

2017-07-01

Mixed crop-livestock farms are widely spread in different tropical regions in the world; they contribute to food security, rural development, sustainability and poverty alleviation. The effect of scale on performance of dual purpose (DP) cattle farms was evaluated in two Mexican ecological zones: dry (DT) and wet tropics (WT). In 2011, a questionnaire of 184 items distributed into technical and social characteristics was applied to a representative sample of 3,285 farms with 50 or less cows (0.97%). The farms were classified into three groups according to their dimension: very small (1-9 cows), small (10-19 cows) and medium (20-50 cows). A general linear model (GLM) with two factors and their interactions was applied. Significant effects in dimension and ecological zone were found as well as seven interactions between both factors (p<0.05). Native pastures were used in all farms for grazing. However, small farms’ herds frequently grazed on cultivated pastures and on crop residues (p<0.05). Medium farms showed the highest grazing surface, but in the WT silage and green fodder were used while in the DT dry fodders were used (p<0.001). The interactions between factors showed a bigger specialization in milk production in DT farms, whereas WT farms were more specialized in meat production. The mixed crop-livestock system in tropic region requires an increase in herd size according to farm’s own productive structure, which is strongly influenced by the ecological zone. The systems would improve with the active participation of smallholders to identify and achieve best practices, higher technological adoption level and with an effective support from public and private Institutions.

Is the increase of scale in the tropics a pathway to smallholders? Dimension and ecological zone effect on the mixed crop-livestock farms

Directory of Open Access Journals (Sweden)

Jaime Rangel

2017-07-01

Full Text Available Mixed crop-livestock farms are widely spread in different tropical regions in the world; they contribute to food security, rural development, sustainability and poverty alleviation. The effect of scale on performance of dual purpose (DP cattle farms was evaluated in two Mexican ecological zones: dry (DT and wet tropics (WT. In 2011, a questionnaire of 184 items distributed into technical and social characteristics was applied to a representative sample of 3,285 farms with 50 or less cows (0.97%. The farms were classified into three groups according to their dimension: very small (1-9 cows, small (10-19 cows and medium (20-50 cows. A general linear model (GLM with two factors and their interactions was applied. Significant effects in dimension and ecological zone were found as well as seven interactions between both factors (p<0.05. Native pastures were used in all farms for grazing. However, small farms’ herds frequently grazed on cultivated pastures and on crop residues (p<0.05. Medium farms showed the highest grazing surface, but in the WT silage and green fodder were used while in the DT dry fodders were used (p<0.001. The interactions between factors showed a bigger specialization in milk production in DT farms, whereas WT farms were more specialized in meat production. The mixed crop-livestock system in tropic region requires an increase in herd size according to farm’s own productive structure, which is strongly influenced by the ecological zone. The systems would improve with the active participation of smallholders to identify and achieve best practices, higher technological adoption level and with an effective support from public and private Institutions.

Is the increase of scale in the tropics a pathway to smallholders? Dimension and ecological zone effect on the mixed crop-livestock farms

International Nuclear Information System (INIS)

Rangel, J.; Espinosa, J.A.; Pablos-Heredero, C. de; Rivas, J.; Perea, J.; Angón, E.; García-Martínez, A.

2017-01-01

Mixed crop-livestock farms are widely spread in different tropical regions in the world; they contribute to food security, rural development, sustainability and poverty alleviation. The effect of scale on performance of dual purpose (DP) cattle farms was evaluated in two Mexican ecological zones: dry (DT) and wet tropics (WT). In 2011, a questionnaire of 184 items distributed into technical and social characteristics was applied to a representative sample of 3,285 farms with 50 or less cows (0.97%). The farms were classified into three groups according to their dimension: very small (1-9 cows), small (10-19 cows) and medium (20-50 cows). A general linear model (GLM) with two factors and their interactions was applied. Significant effects in dimension and ecological zone were found as well as seven interactions between both factors (p<0.05). Native pastures were used in all farms for grazing. However, small farms’ herds frequently grazed on cultivated pastures and on crop residues (p<0.05). Medium farms showed the highest grazing surface, but in the WT silage and green fodder were used while in the DT dry fodders were used (p<0.001). The interactions between factors showed a bigger specialization in milk production in DT farms, whereas WT farms were more specialized in meat production. The mixed crop-livestock system in tropic region requires an increase in herd size according to farm’s own productive structure, which is strongly influenced by the ecological zone. The systems would improve with the active participation of smallholders to identify and achieve best practices, higher technological adoption level and with an effective support from public and private Institutions.

Actual Condition of Paddy Field Levee Maintenance by Various Farm Households including Large-scale Farming in the Developed Land Renting Area

Science.gov (United States)

Sakata, Yasuyo

The survey of interview, resource acquisition, photographic operation, and questionnaire were carried out in the “n” Community in the “y” District in Hakusan City in Ishikawa Prefecture to investigate the actual condition of paddy field levee maintenance in the area where land-renting market was proceeding, large-scale farming was dominant, and the problems of geographically scattered farm-land existed. In the study zone, 1) an agricultural production legal person rent-cultivated some of the paddy fields and maintained the levees, 2) another agricultural production legal person rent-cultivated some of the soy bean fields for crop changeover and land owners maintained the levees. The results indicated that sufficient maintenance was executed on the levees of the paddy fields cultivated by the agricultural production legal person, the soy bean fields for crop changeover, and the paddy fields cultivated by the land owners. Each reason is considered to be the managerial strategy, the economic incentive, the mutual monitoring and cross-regulatory mechanism, etc.

OPTIMIZATION MODEL FOR VEHICLE ROUTING AND EQUIPMENT REPLACEMENT IN FARM MACHINERY

OpenAIRE

Grano, Carolina; Abensur, Eder

2017-01-01

ABSTRACT: An equipment replacement decision takes into account economic engineering models based on discounted cash flow (DCF) such as the Annual Equivalent Cost (AEC). Despite a large number of researches on industrial assets replacement, there is a lack of studies applied to farm goods. This study aimed at assessing an alternative model for economic decision analysis on farm machinery replacement, with no restrictions on the number of replacements and assessed goods during a defined timelin...

CleverFarm final report

Energy Technology Data Exchange (ETDEWEB)

NONE

2003-09-15

Wind turbine technology has ventured in recent years from prototypes and first deployments towards large power plant scale projects. With this, also the ownership structure of wind farms changed: from single farmers to cooperatives, and to large multi-national developers specialised in building and running wind power projects. At the same time, the best sites for wind energy were already taken, leading to more remote sites and offshore sites being developed. Both these developments lead to an increased wish for remote monitoring of turbines. Ideally, the turbine would know on its own accord when it would need maintenance, and call the maintenance crew autonomously. The crew then would have all the information they need to have before they go out to the turbine and do the necessary tasks. Having knowledge of the type of fault that has happened would help the maintenance crew to deal with it efficiently. This also could mean to wait until the next scheduled maintenance is due. The potential savings for this alone are considerable, if you think of the plans for offshore wind farms tens of kilometres from the coast, where access would probably be by helicopter. The idea behind this project was to take the existing techniques developed for optimising and enhancing the performance of wind farms, integrate them into one system and implement the system at a number of wind farms. The techniques include remote measuring of the status and production of the wind farm, short-term prediction of the expected wind speeds at and power output from the wind farm, models for wake calculations, remote control of wind farm production and so on. (au)

Scaling point/plot measurements of greenhouse gas fluxes, balances and intensities to whole-farms and landscapes

NARCIS (Netherlands)

Rosenstock, T.S.; Rufino, Mariana; Chirinda, N.; Bussel, van L.G.J.; Reidsma, P.; Butterbach-Bahl, K.

2015-01-01

Measurements of nutrient stocks and greenhouse gas (GHG) fluxes are typically collected at very local scales (<1 to 30 m2) and then extrapolated to estimate impacts at larger spatial extents (farms, landscapes, or even countries). Translating point measurements to higher levels of aggregation is

Modeling and simulation of offshore wind farm O&M processes

Energy Technology Data Exchange (ETDEWEB)

Joschko, Philip, E-mail: joschko@informatik.uni-hamburg.de [University of Hamburg, Dept. of Informatics, Vogt-Kölln-Straße 30, 22527 Hamburg (Germany); Widok, Andi H., E-mail: a.widok@htw-berlin.de [University of Hamburg, Dept. of Informatics, Vogt-Kölln-Straße 30, 22527 Hamburg (Germany); Appel, Susanne, E-mail: susanne.appel@hs-bremen.de [HSB Bremen, Institute for Environment and Biotechnology, Neustadtswall 30, 28199 Bremen (Germany); Greiner, Saskia, E-mail: saskia.greiner@hs-bremen.de [HSB Bremen, Institute for Environment and Biotechnology, Neustadtswall 30, 28199 Bremen (Germany); Albers, Henning, E-mail: henning.albers@hs-bremen.de [HSB Bremen, Institute for Environment and Biotechnology, Neustadtswall 30, 28199 Bremen (Germany); Page, Bernd, E-mail: page@informatik.uni-hamburg.de [University of Hamburg, Dept. of Informatics, Vogt-Kölln-Straße 30, 22527 Hamburg (Germany)

2015-04-15

This paper describes a holistic approach to operation and maintenance (O&M) processes in the domain of offshore wind farm power generation. The acquisition and process visualization is followed by a risk analysis of all relevant processes. Hereafter, a tool was designed, which is able to model the defined processes in a BPMN 2.0 notation, as well as connect and simulate them. Furthermore, the notation was enriched with new elements, representing other relevant factors that were, to date, only displayable with much higher effort. In that regard a variety of more complex situations were integrated, such as for example new process interactions depending on different weather influences, in which case a stochastic weather generator was combined with the business simulation or other wind farm aspects important to the smooth running of the offshore wind farms. In addition, the choices for different methodologies, such as the simulation framework or the business process notation will be presented and elaborated depending on the impact they had on the development of the approach and the software solution. - Highlights: • Analysis of operation and maintenance processes of offshore wind farms • Process modeling with BPMN 2.0 • Domain-specific simulation tool.

Modeling and simulation of offshore wind farm O&M processes

International Nuclear Information System (INIS)

Joschko, Philip; Widok, Andi H.; Appel, Susanne; Greiner, Saskia; Albers, Henning; Page, Bernd

2015-01-01

This paper describes a holistic approach to operation and maintenance (O&M) processes in the domain of offshore wind farm power generation. The acquisition and process visualization is followed by a risk analysis of all relevant processes. Hereafter, a tool was designed, which is able to model the defined processes in a BPMN 2.0 notation, as well as connect and simulate them. Furthermore, the notation was enriched with new elements, representing other relevant factors that were, to date, only displayable with much higher effort. In that regard a variety of more complex situations were integrated, such as for example new process interactions depending on different weather influences, in which case a stochastic weather generator was combined with the business simulation or other wind farm aspects important to the smooth running of the offshore wind farms. In addition, the choices for different methodologies, such as the simulation framework or the business process notation will be presented and elaborated depending on the impact they had on the development of the approach and the software solution. - Highlights: • Analysis of operation and maintenance processes of offshore wind farms • Process modeling with BPMN 2.0 • Domain-specific simulation tool

Updraft gasification of poultry litter at farm-scale--A case study.

Science.gov (United States)

Taupe, N C; Lynch, D; Wnetrzak, R; Kwapinska, M; Kwapinski, W; Leahy, J J

2016-04-01

Farm and animal wastes are increasingly being investigated for thermochemical conversion, such as gasification, due to the urgent necessity of finding new waste treatment options. We report on an investigation of the use of a farm-scale, auto-thermal gasification system for the production of a heating gas using poultry litter (PL) as a feedstock. The gasification process was robust and reliable. The PL's ash melting temperature was 639°C, therefore the reactor temperature was kept around this value. As a result of the low reactor temperature the process performance parameters were low, with a cold gas efficiency (CGE) of 0.26 and a carbon conversion efficiency (CCE) of 0.44. The calorific value of the clean product gas was 3.39 MJ m(-3)N (LHV). The tar was collected as an emulsion containing 87 wt.% water and the extracted organic compounds were identified. The residual char exceeds thresholds for Zn and Cu to obtain European biochar certification; however, has potential to be classified as a pyrogenic carbonaceous material (PCM), which resembles a high nutrient biochar. Copyright © 2016 Elsevier Ltd. All rights reserved.

Integrated Farm System Model Version 4.3 and Dairy Gas Emissions Model Version 3.3 Software development and distribution

Science.gov (United States)

Modeling routines of the Integrated Farm System Model (IFSM version 4.2) and Dairy Gas Emission Model (DairyGEM version 3.2), two whole-farm simulation models developed and maintained by USDA-ARS, were revised with new components for: (1) simulation of ammonia (NH3) and greenhouse gas emissions gene...

Modeling of the maintenance policy of an offshore wind farm

International Nuclear Information System (INIS)

Maddens, L.; Labeau, P.E.

2004-01-01

Wind energy has a key position in the market of renewable electricity production means. Offshore wind farms offer additional surfaces to exploit this form of energy, together with more favourable wind conditions. Yet offshore windmills ask for higher investment and maintenance costs. Optimising the latter costs should therefore turn out to be particularly beneficial for this technology. The present paper summarizes the main modelling aspects of the maintenance of a typical offshore wind farm, such as the accessibility of the wind turbines and the impact of weather conditions, the cost of the different transport resources, the number of maintenance teams, a tolerated unavailability of part of the windmills, the opportunity to combine corrective and preventive maintenance actions on one or several windmills. All these features were embedded in a Petri net model of the maintenance policy of the farm, allowing to estimate the maintenance costs entailed by several strategies. Advantages and drawbacks of using Petri nets for the modelling of such a maintenance strategy are finally discussed. (authors)

Modelling of offshore wind turbine wakes with the wind farm program FLaP

DEFF Research Database (Denmark)

Lange, B.; Waldl, H.P.; Guerrero, A.G.

2003-01-01

The wind farm layout program FLaP estimates the wind speed at any point in a wind farm and the power output of the turbines. The ambient flow conditions and the properties of the turbines and the farm are used as input. The core of the program is an axisymmetric wake model describing the wake...

An integrated model for estimating energy cost of a tidal current turbine farm

International Nuclear Information System (INIS)

Li, Ye; Lence, Barbara J.; Calisal, Sander M.

2011-01-01

A tidal current turbine is a device for harnessing energy from tidal currents and functions in a manner similar to a wind turbine. A tidal current turbine farm consists of a group of tidal current turbines distributed in a site where high-speed current is available. The accurate prediction of energy cost of a tidal current turbine farm is important to the justification of planning and constructing such a farm. However, the existing approaches used to predict energy cost of tidal current turbine farms oversimplify the hydrodynamic interactions between turbines in energy prediction and oversimplify the operation and maintenance strategies involved in cost estimation as well as related fees. In this paper, we develop a model, which integrates a marine hydrodynamic model with high accuracy for predicting energy output and a comprehensive cost-effective operation and maintenance model for estimating the cost that may be incurred in producing the energy, to predict energy cost from a tidal current turbine farm. This model is expected to be able to simulate more complicated cases and generate more accurate results than existing models. As there is no real tidal current turbine farm, we validate this model with offshore wind studies. Finally, case studies about Vancouver are conducted with a scenario-based analysis. We minimize the energy cost by minimizing the total cost and maximizing the total power output under constraints related to the local conditions (e.g., geological and labor information) and the turbine specifications. The results suggest that tidal current energy is about ready to penetrate the electricity market in some major cities in North America if learning curve for the operational and maintenance is minimum. (author)

Do Scale Frames Matter? Scale Frame Mismatches in the Decision Making Process of a "Mega Farm" in a Small Dutch Village

Directory of Open Access Journals (Sweden)

Maartje van. Lieshout

2011-03-01

Full Text Available Scale issues are an increasingly important feature of complex sustainability issues, but they are mostly taken for granted in policy processes. However, the scale at which a problem is defined as well as the scale at which it should be solved are potentially contentious issues. The framing of a problem as a local, regional, or global problem is not without consequences and influences processes of inclusion and exclusion. Little is known about the ways actors frame scales and the effect of different scale frames on decision making processes. This paper addresses the questions that different scale frames actors use and what the implications of scale frames are for policy processes. It does so by analyzing the scale frames deployed by different actors on the establishment of a so-called new mixed company or mega farm and the related decision making process in a Dutch municipality. We find that actors deploy different and conflicting scale frames, leading to scale frame mismatches. We conclude that scale frame mismatches play an important role in the stagnation of the decision making process.

Microbial Indicators, Pathogens, and Antibiotic Resistance in Groundwater Impacted by Animal Farming: Field Scale to Basin Scale

Science.gov (United States)

Harter, T.; Li, X.; Atwill, E. R.; Packman, A. I.

2015-12-01

Several surveys of microbial indicators and pathogens were conducted to determine the impact of confined animal farming operations (CAFOs) on shallow, local, and regional groundwater quality in the Central Valley aquifer system, California. The aquifer system consists of highly heterogeneous, alluvial, unconsolidated coarse- to fine-grained sediments and is among the largest aquifers in the U.S.. Overlying landuse includes 3 million ha of irrigated agriculture and 1.7 million mature dairy cows in nearly 1,500 CAFOs. A multi-scale survey of water-borne indicator pathogens (Enterococcus spp. and generic E. coli) and of three water-borne pathogens (Campylobacter, Salmonella, and E. coli O157:H7) was conducted at five different spatial scales, increasing with distance from animal sources of these enteric microbial organisms: moist surfaces within individual CAFO sub-systems (calf-hutches, heifer corrals, mature cow stalls, hospital barn etc.), first encountered (shallow) groundwater immediately below these sub-systems, production aquifer below CAFOs, production aquifer near CAFOs, and production aquifer away from CAFOs. Where found, indicator pathogens were tested for antibiotic resistance. Hundreds of samples were collected at each scale: continuously during irrigation events and seasonally over a multi-year period at the three smaller site-scales; and in a one-time survey at the two larger, regional scales. All three pathogens were frequently detected in moist surface samples across CAFO sub-systems, albeit at concentrations several orders of magnitude lower than enteric indicators. Two of the three pathogens (but not Campylobacter) were also detected in first encountered groundwater, at 3-9 m below ground surface, in 1% of samples. No pathogens were found at the production aquifer scales. Generic E. coli was detected in ¼ of first encountered groundwater samples, and in 4% of production aquifer samples, while Enterococcus spp. was ubiquitously present across the

Statistical meandering wake model and its application to yaw-angle optimisation of wind farms

DEFF Research Database (Denmark)

Thøgersen, Emil; Tranberg, Bo; Herp, Jürgen

2017-01-01

deterministic models to a statistical meandering wake model (SMWM), where a random directional deflection is assigned to a narrow wake in such a way that on average it resembles a broad Jensen wake. In a second step, the model is further generalised to wind-farm level, where the deflections of the multiple...... wakes are treated as independently and identically distributed random variables. When carefully calibrated to the Nysted wind farm, the ensemble average of the statistical model produces the same wind-direction dependence of the power efficiency as obtained from the standard Jensen model. Upon using...... the JWM to perform a yaw-angle optimisation of wind-farm power output, we find an optimisation gain of 6.7% for the Nysted wind farm when compared to zero yaw angles and averaged over all wind directions. When applying the obtained JWM-based optimised yaw angles to the SMWM, the ensemble-averaged gain...

Harmonic Instability Source Identification in Large Wind Farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2017-01-01

A large-scale power electronics based power system like a wind farm introduces the passive and active impedances. The interactions between the active and passive impedances can lead to harmonic-frequency oscillations above the fundamental frequency, which can be called harmonic instability....... This paper presents an approach to identify which wind turbine and which bus has more contribution to the harmonic instability problems. In the approach, a wind farm is modeled as a Multi-Input Multi-Output (MIMO) dynamic system. The poles of the MIMO transfer matrix are used to predict the system...... instability and the eigenvalues sensitivity analysis in respect to the elements of the MIMO matrix locates the most influencing buses of the wind farm. Time-domain simulations in PSCAD software environment for a 400-MW wind farm validate that the presented approach is an effective tool to determine the main...

Reindeer habitat use in relation to two small wind farms, during preconstruction, construction, and operation.

Science.gov (United States)

Skarin, Anna; Alam, Moudud

2017-06-01

Worldwide there is a rush toward wind power development and its associated infrastructure. In Fennoscandia, large-scale wind farms comprising several hundred windmills are currently built in important grazing ranges used for Sámi reindeer husbandry. In this study, reindeer habitat use was assessed using reindeer fecal pellet group counts in relation to two relatively small wind farms, with 8 and 10 turbines, respectively. In 2009, 1,315 15-m 2 plots were established and pellet groups were counted and cleaned from the plots. This was repeated once a year in May, during preconstruction, construction, and operation of the wind farms, covering 6 years (2009-2014) of reindeer habitat use in the area. We modeled the presence/absence of any pellets in a plot at both the local (wind farm site) and regional (reindeer calving to autumn range) scale with a hierarchical logistic regression, where spatial correlation was accounted for via random effects, using vegetation type, and the interaction between distance to wind turbine and time period as predictor variables. Our results revealed an absolute reduction in pellet groups by 66% and 86% around each wind farm, respectively, at local scale and by 61% at regional scale during the operation phase compared to the preconstruction phase. At the regional, scale habitat use declined close to the turbines in the same comparison. However, at the local scale, we observed increased habitat use close to the wind turbines at one of the wind farms during the operation phase. This may be explained by continued use of an important migration route close to the wind farm. The reduced use at the regional scale nevertheless suggests that there may be an overall avoidance of both wind farms during operation, but further studies of reindeer movement and behavior are needed to gain a better understanding of the mechanisms behind this suggested avoidance.

A static VAR compensator model for improved ride-through capability of wind farms

Energy Technology Data Exchange (ETDEWEB)

Akhmatov, V.; Soebrink, K.

2004-12-01

Dynamic reactive compensation is associated with reactive power and voltage control of induction generator based wind turbines. With regard to wind power, application areas of dynamic reactive compensation can be improvement of the power quality and the voltage stability, the control of the reactive power exchange between the wind farm and the power grid in the wind farm connection point as well as improvement of the ride-through capability of the wind farm. This article presents a model of a Static VAR Compensator (SVC) with dynamic generic control that is a kind of dynamic reactive compensation device. The term 'generic' implies that the model is general and must cover a variety of the SVC units and their specific controls from different manufacturers. The SVC model with dynamic generic control is implemented by Eltra in the simulation tool Powerfactory and validated from the SVC model in the tool PSCAD/EMTDC. Implementation in the tool Powerfactory makes it possible to apply the SVC model with dynamic generic control in investigations of power system stability with regard to establishment of large wind farms without restrictions on the model size of the power grid. (Author)

An Integrated Multi-Criteria Decision Making Model for Evaluating Wind Farm Performance

Directory of Open Access Journals (Sweden)

Mei-Sung Kang

2011-11-01

Full Text Available The demands for alternative energy resources have been increasing exponentially in the 21st century due to continuous industrial development, depletion of fossil fuels and emerging environmental consciousness. Renewable energy sources, including wind energy, hydropower energy, geothermal energy, solar energy, biomass energy and ocean power, have received increasing attention as alternative means of meeting global energy demands. After Japan's Fukushima nuclear plant disaster in March 2011, more and more countries are having doubt about the safety of nuclear plants. As a result, safe and renewable energy sources are attracting even more attention these days. Wind energy production, with its relatively safer and positive environmental characteristics, has evolved in the past few decades from a marginal activity into a multi-billion dollar industry. In this research, a comprehensive evaluation model is constructed to select a suitable location for developing a wind farm. The model incorporates interpretive structural modeling (ISM, benefits, opportunities, costs and risks (BOCR and fuzzy analytic network process (FANP. Experts in the field are invited to contribute their expertise in evaluating the importance of the factors and various aspects of the wind farm evaluation problem, and the most suitable wind farm can finally be generated from the model. A case study is carried out in Taiwan in evaluating the expected performance of several potential wind farms, and a recommendation is provided for selecting the most appropriate wind farm for construction.

A mechanistic model for electricity consumption on dairy farms: definition, validation, and demonstration.

Science.gov (United States)

Upton, J; Murphy, M; Shalloo, L; Groot Koerkamp, P W G; De Boer, I J M

2014-01-01

Our objective was to define and demonstrate a mechanistic model that enables dairy farmers to explore the impact of a technical or managerial innovation on electricity consumption, associated CO2 emissions, and electricity costs. We, therefore, (1) defined a model for electricity consumption on dairy farms (MECD) capable of simulating total electricity consumption along with related CO2 emissions and electricity costs on dairy farms on a monthly basis; (2) validated the MECD using empirical data of 1yr on commercial spring calving, grass-based dairy farms with 45, 88, and 195 milking cows; and (3) demonstrated the functionality of the model by applying 2 electricity tariffs to the electricity consumption data and examining the effect on total dairy farm electricity costs. The MECD was developed using a mechanistic modeling approach and required the key inputs of milk production, cow number, and details relating to the milk-cooling system, milking machine system, water-heating system, lighting systems, water pump systems, and the winter housing facilities as well as details relating to the management of the farm (e.g., season of calving). Model validation showed an overall relative prediction error (RPE) of less than 10% for total electricity consumption. More than 87% of the mean square prediction error of total electricity consumption was accounted for by random variation. The RPE values of the milk-cooling systems, water-heating systems, and milking machine systems were less than 20%. The RPE values for automatic scraper systems, lighting systems, and water pump systems varied from 18 to 113%, indicating a poor prediction for these metrics. However, automatic scrapers, lighting, and water pumps made up only 14% of total electricity consumption across all farms, reducing the overall impact of these poor predictions. Demonstration of the model showed that total farm electricity costs increased by between 29 and 38% by moving from a day and night tariff to a flat

The Relationship of Dairy Farm Eco-Efficiency with Intensification and Self-Sufficiency. Evidence from the French Dairy Sector Using Life Cycle Analysis, Data Envelopment Analysis and Partial Least Squares Structural Equation Modelling.

Directory of Open Access Journals (Sweden)

Andreas Diomedes Soteriades

Full Text Available We aimed at quantifying the extent to which agricultural management practices linked to animal production and land use affect environmental outcomes at a larger scale. Two practices closely linked to farm environmental performance at a larger scale are farming intensity, often resulting in greater off-farm environmental impacts (land, non-renewable energy use etc. associated with the production of imported inputs (e.g. concentrates, fertilizer; and the degree of self-sufficiency, i.e. the farm's capacity to produce goods from its own resources, with higher control over nutrient recycling and thus minimization of losses to the environment, often resulting in greater on-farm impacts (eutrophication, acidification etc.. We explored the relationship of these practices with farm environmental performance for 185 French specialized dairy farms. We used Partial Least Squares Structural Equation Modelling to build, and relate, latent variables of environmental performance, intensification and self-sufficiency. Proxy indicators reflected the latent variables for intensification (milk yield/cow, use of maize silage etc. and self-sufficiency (home-grown feed/total feed use, on-farm energy/total energy use etc.. Environmental performance was represented by an aggregate 'eco-efficiency' score per farm derived from a Data Envelopment Analysis model fed with LCA and farm output data. The dataset was split into two spatially heterogeneous (bio-physical conditions, production patterns regions. For both regions, eco-efficiency was significantly negatively related with milk yield/cow and the use of maize silage and imported concentrates. However, these results might not necessarily hold for intensive yet more self-sufficient farms. This requires further investigation with latent variables for intensification and self-sufficiency that do not largely overlap- a modelling challenge that occurred here. We conclude that the environmental 'sustainability' of intensive

The Relationship of Dairy Farm Eco-Efficiency with Intensification and Self-Sufficiency. Evidence from the French Dairy Sector Using Life Cycle Analysis, Data Envelopment Analysis and Partial Least Squares Structural Equation Modelling.

Science.gov (United States)

Soteriades, Andreas Diomedes; Stott, Alistair William; Moreau, Sindy; Charroin, Thierry; Blanchard, Melanie; Liu, Jiayi; Faverdin, Philippe

2016-01-01

We aimed at quantifying the extent to which agricultural management practices linked to animal production and land use affect environmental outcomes at a larger scale. Two practices closely linked to farm environmental performance at a larger scale are farming intensity, often resulting in greater off-farm environmental impacts (land, non-renewable energy use etc.) associated with the production of imported inputs (e.g. concentrates, fertilizer); and the degree of self-sufficiency, i.e. the farm's capacity to produce goods from its own resources, with higher control over nutrient recycling and thus minimization of losses to the environment, often resulting in greater on-farm impacts (eutrophication, acidification etc.). We explored the relationship of these practices with farm environmental performance for 185 French specialized dairy farms. We used Partial Least Squares Structural Equation Modelling to build, and relate, latent variables of environmental performance, intensification and self-sufficiency. Proxy indicators reflected the latent variables for intensification (milk yield/cow, use of maize silage etc.) and self-sufficiency (home-grown feed/total feed use, on-farm energy/total energy use etc.). Environmental performance was represented by an aggregate 'eco-efficiency' score per farm derived from a Data Envelopment Analysis model fed with LCA and farm output data. The dataset was split into two spatially heterogeneous (bio-physical conditions, production patterns) regions. For both regions, eco-efficiency was significantly negatively related with milk yield/cow and the use of maize silage and imported concentrates. However, these results might not necessarily hold for intensive yet more self-sufficient farms. This requires further investigation with latent variables for intensification and self-sufficiency that do not largely overlap- a modelling challenge that occurred here. We conclude that the environmental 'sustainability' of intensive dairy farming

Proximity search heuristics for wind farm optimal layout

DEFF Research Database (Denmark)

Fischetti, Martina; Monaci, Michele

2016-01-01

A heuristic framework for turbine layout optimization in a wind farm is proposed that combines ad-hoc heuristics and mixed-integer linear programming. In our framework, large-scale mixed-integer programming models are used to iteratively refine the current best solution according to the recently...

Processor farming in two-level analysis of historical bridge

Science.gov (United States)

Krejčí, T.; Kruis, J.; Koudelka, T.; Šejnoha, M.

2017-11-01

This contribution presents a processor farming method in connection with a multi-scale analysis. In this method, each macro-scopic integration point or each finite element is connected with a certain meso-scopic problem represented by an appropriate representative volume element (RVE). The solution of a meso-scale problem provides then effective parameters needed on the macro-scale. Such an analysis is suitable for parallel computing because the meso-scale problems can be distributed among many processors. The application of the processor farming method to a real world masonry structure is illustrated by an analysis of Charles bridge in Prague. The three-dimensional numerical model simulates the coupled heat and moisture transfer of one half of arch No. 3. and it is a part of a complex hygro-thermo-mechanical analysis which has been developed to determine the influence of climatic loading on the current state of the bridge.

Emergence of highly pathogenic porcine reproductive and respiratory syndrome (HP-PRRS) in medium-scale swine farms in southeastern Cambodia.

Science.gov (United States)

Tornimbene, B; Frossard, J-P; Chhim, V; Sorn, S; Guitian, J; Drew, T W

2015-01-01

Since 2006, reports from China and Viet Nam have alerted of an emergent highly pathogenic variant of porcine reproductive and respiratory syndrome virus (HP-PRRSV) in that region. The frequent occurrence of outbreaks in these countries puts Cambodian pig farms at high risk of infection, but no study had been conducted to investigate the presence of HP-PRRS in Cambodian farms. We investigated the presence of HP-PRRS in medium-scale (semi-commercial) swine farms in the Cambodian southeastern region. Specifically, one province bordering Viet Nam (Takeo) was selected due to the concentration of most semi-commercial farms in that province. A cross-sectional study was carried out, between July and September 2010 to assess whether the prevalence of infection in these farms was indicative of recent spread of PPRSV and to identify risk factors for infection. The number of farms to be sampled was established using methods for Lot Quality Assurance Surveys (LQAS), in order to achieve a pre-established ability to discriminate between two different prevalence settings. The target population comprised all semi-commercial farms in Takeo province from which a random sample of 35 farms was selected. Selected farms were visited and questionnaires administered to gather information on farm characteristics and husbandry practices. Blood samples from individual pigs were collected in each of the study farms and tested for PRRSV, along with a number of other swine respiratory pathogens in order to investigate potential interactions. Our results showed that the virus was already present in Takeo semi-commercial pig population (LQAS herd prevalence ≥85%) at the time of sampling. The presence of sows in the farm and farm density were significantly associated (P<0.05) with the introduction and the presence of PRRS - but this was an unadjusted association as small sample size precluded multivariate analysis. Spatiotemporal description of the supposed pattern of infection revealed that the

Statistical meandering wake model and its application to yaw-angle optimisation of wind farms

International Nuclear Information System (INIS)

Thøgersen, E; Tranberg, B; Greiner, M; Herp, J

2017-01-01

The wake produced by a wind turbine is dynamically meandering and of rather narrow nature. Only when looking at large time averages, the wake appears to be static and rather broad, and is then well described by simple engineering models like the Jensen wake model (JWM). We generalise the latter deterministic models to a statistical meandering wake model (SMWM), where a random directional deflection is assigned to a narrow wake in such a way that on average it resembles a broad Jensen wake. In a second step, the model is further generalised to wind-farm level, where the deflections of the multiple wakes are treated as independently and identically distributed random variables. When carefully calibrated to the Nysted wind farm, the ensemble average of the statistical model produces the same wind-direction dependence of the power efficiency as obtained from the standard Jensen model. Upon using the JWM to perform a yaw-angle optimisation of wind-farm power output, we find an optimisation gain of 6.7% for the Nysted wind farm when compared to zero yaw angles and averaged over all wind directions. When applying the obtained JWM-based optimised yaw angles to the SMWM, the ensemble-averaged gain is calculated to be 7.5%. This outcome indicates the possible operational robustness of an optimised yaw control for real-life wind farms. (paper)

Statistical meandering wake model and its application to yaw-angle optimisation of wind farms

Science.gov (United States)

Thøgersen, E.; Tranberg, B.; Herp, J.; Greiner, M.

2017-05-01

The wake produced by a wind turbine is dynamically meandering and of rather narrow nature. Only when looking at large time averages, the wake appears to be static and rather broad, and is then well described by simple engineering models like the Jensen wake model (JWM). We generalise the latter deterministic models to a statistical meandering wake model (SMWM), where a random directional deflection is assigned to a narrow wake in such a way that on average it resembles a broad Jensen wake. In a second step, the model is further generalised to wind-farm level, where the deflections of the multiple wakes are treated as independently and identically distributed random variables. When carefully calibrated to the Nysted wind farm, the ensemble average of the statistical model produces the same wind-direction dependence of the power efficiency as obtained from the standard Jensen model. Upon using the JWM to perform a yaw-angle optimisation of wind-farm power output, we find an optimisation gain of 6.7% for the Nysted wind farm when compared to zero yaw angles and averaged over all wind directions. When applying the obtained JWM-based optimised yaw angles to the SMWM, the ensemble-averaged gain is calculated to be 7.5%. This outcome indicates the possible operational robustness of an optimised yaw control for real-life wind farms.

Modelling and measurements of wakes in large wind farms

DEFF Research Database (Denmark)

Barthelmie, Rebecca Jane; Rathmann, Ole; Frandsen, Sten Tronæs

2007-01-01

The paper presents research conducted in the Flow workpackage of the EU funded UPWIND project which focuses on improving models of flow within and downwind of large wind farms in complex terrain and offshore. The main activity is modelling the behaviour of wind turbine wakes in order to improve...

Uncertainties and Wakes for Short-term Power Production of a Wind Farm

DEFF Research Database (Denmark)

Göçmen, Tuhfe; Giebel, Gregor

2018-01-01

Similar to the conventional power plants, the wind farms are expected to contribute to the grid stability and communicate with the system operators regarding the potential power production on much shorter time scales than AEP or even 10-min. Additionally, increasing interest to aerodynamic control...... of wind farms, both in the research community and in the industry, necessitates the wake models to be more accurate and reliable at shorter intervals. In this study, we discuss the uncertainties attached to an engineering wake model derived for 1-sec turbine data, and investigate the methods for reducing...... the uncertainty of such an application via further training the model for the wind farm and the time period in question using the historical data....

Wind farm electrical power production model for load flow analysis

International Nuclear Information System (INIS)

Segura-Heras, Isidoro; Escriva-Escriva, Guillermo; Alcazar-Ortega, Manuel

2011-01-01

The importance of renewable energy increases in activities relating to new forms of managing and operating electrical power: especially wind power. Wind generation is increasing its share in the electricity generation portfolios of many countries. Wind power production in Spain has doubled over the past four years and has reached 20 GW. One of the greatest problems facing wind farms is that the electrical power generated depends on the variable characteristics of the wind. To become competitive in a liberalized market, the reliability of wind energy must be guaranteed. Good local wind forecasts are therefore essential for the accurate prediction of generation levels for each moment of the day. This paper proposes an electrical power production model for wind farms based on a new method that produces correlated wind speeds for various wind farms. This method enables a reliable evaluation of the impact of new wind farms on the high-voltage distribution grid. (author)

Does Contract Farming Improve Smallholder Farmers Income? The Case of Avocado Farming in Kenya

OpenAIRE

Mwambi, Mercy; Oduol, Judith; Mshenga, Patience M.; Mwanarusi, Saidi

2013-01-01

Contract farming is seen by its proponents as a tool for creating new market opportunities as well as for providing credit and training, leading to increased incomes of smallholder farmers. Critics, however, argue that contract farming encourages unequal bargaining relationships with agribusiness firms and is likely to pass risks to farmers, thus favouring large scale farmers at the expense of smallholders. Another school of thought contends that the effect of contract farming on the liveliho...

Using Satellite SAR to Characterize the Wind Flow around Offshore Wind Farms

Directory of Open Access Journals (Sweden)

Charlotte Bay Hasager

2015-06-01

Full Text Available Offshore wind farm cluster effects between neighboring wind farms increase rapidly with the large-scale deployment of offshore wind turbines. The wind farm wakes observed from Synthetic Aperture Radar (SAR are sometimes visible and atmospheric and wake models are here shown to convincingly reproduce the observed very long wind farm wakes. The present study mainly focuses on wind farm wake climatology based on Envisat ASAR. The available SAR data archive covering the large offshore wind farms at Horns Rev has been used for geo-located wind farm wake studies. However, the results are difficult to interpret due to mainly three issues: the limited number of samples per wind directional sector, the coastal wind speed gradient, and oceanic bathymetry effects in the SAR retrievals. A new methodology is developed and presented. This method overcomes effectively the first issue and in most cases, but not always, the second. In the new method all wind field maps are rotated such that the wind is always coming from the same relative direction. By applying the new method to the SAR wind maps, mesoscale and microscale model wake aggregated wind-fields results are compared. The SAR-based findings strongly support the model results at Horns Rev 1.

Improving farm management by modeling the contamination of farm tank milk with butyric acid bacteria

NARCIS (Netherlands)

Vissers, M.M.M.; Driehuis, F.; Giffel, te M.C.; Jong, de P.; Lankveld, J.M.G.

2006-01-01

Control of contamination of farm tank milk (FTM) with the spore-forming butyric acid bacteria (BAB) is important to prevent the late-blowing defect in semi-hard cheeses. The risk of late blowing can be decreased via control of the contamination level of FTM with BAB. A modeling approach was applied

Modelling and measurements of wakes in large wind farms

International Nuclear Information System (INIS)

Barthelmie, R J; Rathmann, O; Frandsen, S T; Hansen, K S; Politis, E; Prospathopoulos, J; Rados, K; Cabezon, D; Schlez, W; Phillips, J; Neubert, A; Schepers, J G; Pijl, S P van der

2007-01-01

The paper presents research conducted in the Flow workpackage of the EU funded UPWIND project which focuses on improving models of flow within and downwind of large wind farms in complex terrain and offshore. The main activity is modelling the behaviour of wind turbine wakes in order to improve power output predictions

Economic Situation of Fish Farming in Southeastern Coast of the Black Sea

Directory of Open Access Journals (Sweden)

Ştefan Mihai Petrea

2012-10-01

Full Text Available Aquaculture industry, like most other industries, has a very powerfull correlation with the economical domain. Being an economic activity that generates profit, practicing fish farming aims profit maximization. The present study gives information regarding the economical indicators and also makes a cost structure analysis of five groups of fish farms from Southeastern Coast of the Black Sea: homestead fish farms, small scale fish farms, middle scale fish farms, big scale fish farms and floating cages. The fish farms were classified in this way by their production capacity. In order to collect data, the most representative fish farms for each group were selected and face to face interviews were made for every one of them. Data related to their source of financing, initial investment, labour costs, selling prices, feed costs and other operational costs were collected, arranged, structured and analyzed and a series of economic indicators as gross production value, gross margin, breakeven quantity, specific investment, profit, profitability ratio, rate of return or labour productivity were calculated. As a result, it was observed that fish production capacity has a big influence over the rate of return, middle scale fish farms being the most profitable, followed closely by small scale fish farms.

Mathematical modelling of a farm enterprise value on the ...

African Journals Online (AJOL)

Mathematical modelling of a farm enterprise value on the agricultural market with the ... Subsidies in the EU countries reached 45-50% of the value of commodity output ... This financing gap entailed a number of negative consequences.

Modelling of a synchronous offshore pumping mode airborne wind energy farm

International Nuclear Information System (INIS)

Coleman, J.; Ahmad, H.; Pican, E.; Toal, D.

2014-01-01

A wind farm for the deployment of pumping mode AWE (airborne wind energy) systems is presented in this paper. The topology presented is suitable for the deployment of such systems in a marine or similarly inaccessible environment. A brief technical description of AWE is provided, outlining the background, motivation and approaches taken by this emerging technology. A method of providing a continuous power supply from a cluster of AWE systems whose individual operation produces a periodic power supply is outlined. This method employs direct drive, directly interconnected permanent magnet synchronous generators on a local bus. A full-scale power converter is located at the point of grid connection, providing compliant power output for the remote cluster. In the case of a marine environment deployment, the power electronics are located onshore where maintenance and repair can be readily performed without the delays and costs associated with offshore maintenance and repair. The direct interconnection of synchronous generators introduces the requirement for a control system to control the connection of offline machines to the energised bus. A mathematical model of the system is outlined and the implementation of this model in Simulink is detailed. Simulation results under varied operating conditions are presented and discussed. - Highlights: • Airborne wind energy (AWE) is an emerging novel approach to wind energy. • ‘Pumping mode’ AWE devices in individual operation produce a periodic power output. • We do not reverse the generator during pumping mode operation. • We directly interconnect multiple AWE devices to provide continuous power output. • Simulation of proposed AWE farm operations presented, with encouraging results

Regional-scale variation in the distribution and abundance of farming damselfishes on Australia's Great Barrier Reef

KAUST Repository

Emslie, Michael J.; Logan, Murray; Ceccarelli, Daniela M.; Cheal, Alistair J.; Hoey, Andrew; Miller, Ian R.; Sweatman, Hugh P A

2012-01-01

Territorial damselfishes that manipulate ("farm") the algae in their territories can have a marked effect on benthic community structure and may influence coral recovery following disturbances. Despite the numerical dominance of farming species on many reefs, the importance of their grazing activities is often overlooked, with most studies only examining their roles over restricted spatial and temporal scales. We used the results of field surveys covering 9.5° of latitude of the Great Barrier Reef to describe the distribution, abundance and temporal dynamics of farmer communities. Redundancy analysis revealed unique subregional assemblages of farming species that were shaped by the combined effects of shelf position and, to a lesser extent, by latitude. These spatial patterns were largely stable through time, except when major disturbances altered the benthic community. Such disturbances affected the functional guilds of farmers in different ways. Since different guilds of farmers modify benthic community structure and affect survival of juvenile corals in different ways, these results have important implications for coral recovery following disturbances. © 2012 Springer-Verlag.

Regional-scale variation in the distribution and abundance of farming damselfishes on Australia's Great Barrier Reef

KAUST Repository

Emslie, Michael J.

2012-03-15

Territorial damselfishes that manipulate ("farm") the algae in their territories can have a marked effect on benthic community structure and may influence coral recovery following disturbances. Despite the numerical dominance of farming species on many reefs, the importance of their grazing activities is often overlooked, with most studies only examining their roles over restricted spatial and temporal scales. We used the results of field surveys covering 9.5° of latitude of the Great Barrier Reef to describe the distribution, abundance and temporal dynamics of farmer communities. Redundancy analysis revealed unique subregional assemblages of farming species that were shaped by the combined effects of shelf position and, to a lesser extent, by latitude. These spatial patterns were largely stable through time, except when major disturbances altered the benthic community. Such disturbances affected the functional guilds of farmers in different ways. Since different guilds of farmers modify benthic community structure and affect survival of juvenile corals in different ways, these results have important implications for coral recovery following disturbances. © 2012 Springer-Verlag.

Phosphorus management in cropping systems of the Paris Basin: From farm to regional scale.

Science.gov (United States)

Le Noë, Julia; Garnier, Josette; Billen, Gilles

2018-01-01

The sustainability of phosphorus (P) fertilization in cropping systems is an important issue because P resources on earth are limited and excess P in soils can lead to ecological damage such as eutrophication. Worldwide, there is an increasing interest in organic farming (OF) due to its good environmental performance. However, organic cropping systems are suspected of generating negative P budgets, which questions their ability to provide sustainable P management. The design of agricultural systems at a broader scale also largely influences the shape of the P cycle and the possibility of its recycling to cropland. In this context, the aim of this study was to assess the relative influence of (i) OF versus conventional farming (CF) practices and (ii) the structure of agro-food systems at the regional scale, on P cycling and availability on cropland. For this purpose, we examined P budgets and soil P status of 14 organic and conventional cropping systems in commercial farms located in the Paris Basin. Available P was analyzed using two different methods: resin P and Olsen P. The results revealed no significant differences between CF and OF in available P stocks. Phosphorus budgets were always negative and significantly lower in CF systems, indicating that P was mined from soil reserves. In parallel, we estimated P budgets over cropland in all French regions for two distinct periods, 2004-2014 and 1970-1981, and showed that specialized intensive cropping systems in the Paris Basin led to a high, positive P budget in the latter period. However, this trend was reversed in the 2004-2014 period due to a sharp reduction of the mineral fertilizer application rate. The shift from very high P budgets to much lower and sometimes negative P budgets would not be a threat for agriculture due to the current high level of Olsen P in these regions, which was consistent with our measurements at the plot scale. Overall, these results suggest that OF would not lead to more P deficiency

Limited usage of mechanical equipment in small-scale rice farming: a cause for concern

Directory of Open Access Journals (Sweden)

Gaudiose Mujawamariya

2017-06-01

Full Text Available The role of mechanization in agriculture is well documented in terms of improving productivity of farm labour and land and sustaining income status and welfare of small-scale farmers. In rice production, there is a high cost associated with labour intensive production practices especially in land preparation, weeding and harvesting, the limited adoption of mechanical equipment in these operations remains an issue of concern. The current study investigates the usage of mechanical equipment in a setting where majority of farmers are exposed to technologies but cases of non-usage/adoption are observed. The choice of usage of mechanical equipment is analysed through probit and poisson models. Mechanization generally has a positive effect on production. However, the cost associated with its usage high. The equipment should be made available and affordable to farmers especially because demand for rent is not met. Awareness is essential for adoption and ease of use of mechanization.

Numerical modelling of organic waste dispersion from fjord located fish farms

Science.gov (United States)

Ali, Alfatih; Thiem, Øyvind; Berntsen, Jarle

2011-07-01

In this study, a three-dimensional particle tracking model coupled to a terrain following ocean model is used to investigate the dispersion and the deposition of fish farm particulate matter (uneaten food and fish faeces) on the seabed due to tidal currents. The particle tracking model uses the computed local flow field for advection of the particles and random movement to simulate the turbulent diffusion. Each particle is given a settling velocity which may be drawn from a probability distribution according to settling velocity measurements of faecal and feed pellets. The results show that the maximum concentration of organic waste for fast sinking particles is found under the fish cage and continue monotonically decreasing away from the cage area. The maximum can split into two maximum peaks located at both sides of the centre of the fish cage area in the current direction. This process depends on the sinking time (time needed for a particle to settle at the bottom), the tidal velocity and the fish cage size. If the sinking time is close to a multiple of the tidal period, the maximum concentration point will be under the fish cage irrespective of the tide strength. This is due to the nature of the tidal current first propagating the particles away and then bringing them back when the tide reverses. Increasing the cage size increases the likelihood for a maximum waste accumulation beneath the fish farm, and larger farms usually means larger biomasses which can make the local pollution even more severe. The model is validated by using an analytical model which uses an exact harmonic representation of the tidal current, and the results show an excellent agreement. This study shows that the coupled ocean and particle model can be used in more realistic applications to help estimating the local environmental impact due to fish farms.

Coordinated Voltage Control of a Wind Farm based on Model Predictive Control

DEFF Research Database (Denmark)

Zhao, Haoran; Wu, Qiuwei; Guo, Qinglai

2016-01-01

This paper presents an autonomous wind farm voltage controller based on Model Predictive Control (MPC). The reactive power compensation and voltage regulation devices of the wind farm include Static Var Compensators (SVCs), Static Var Generators (SVGs), Wind Turbine Generators (WTGs) and On...... are calculated based on an analytical method to improve the computation efficiency and overcome the convergence problem. Two control modes are designed for both voltage violated and normal operation conditions. A wind farm with 20 wind turbines was used to conduct case studies to verify the proposed coordinated...

A Wind Farm Electrical Systems Evaluation with EeFarm-II

Directory of Open Access Journals (Sweden)

Jan Pierik

2010-03-01

Full Text Available EeFarm-II is used to evaluate 13 different electrical systems for a 200 MW wind farm with a 100 km connection to shore. The evaluation is based on component manufacturer data of 2009. AC systems are compared to systems with DC connections inside the wind farm and DC connection to shore. Two options have the best performance for this wind farm size and distance: the AC system and the system with a DC connection to shore. EeFarm-II is a user friendly computer program for wind farm electrical and economic evaluation. It has been built as a Simulink Library in the graphical interface of Matlab-Simulink. EeFarm-II contains models of wind turbines, generators, transformers, AC cables, inductors, nodes, splitters, PWM converters, thyristor converters, DC cables, choppers and statcoms.

The farming system component of European agricultural landscapes

DEFF Research Database (Denmark)

Andersen, Erling

2017-01-01

Agricultural landscapes are the outcome of combined natural and human factors over time. This paper explores the scope of perceiving the agricultural landscapes of the European Union (EU) as distinct patterns of farming systems and landscape elements in homogeneous biophysical and administrative...... landscapes evolve from the praxis of the farmers and takes into account the scale, intensity and specialisation of the agricultural production. From farming system design point of view, the approach can be used to integrate the landscape in the design process. From a policy point of view, the approach offers...... endowments. The focus is on the farming systems component of the agricultural landscapes by applying a typology to the sample farms of the Farm Accountancy Data Network and scaling up the results to the landscape level for the territory of the EU. The farming system approach emphasises that agricultural...

Sandia Wake Imaging System Field Test Report: 2015 Deployment at the Scaled Wind Farm Technology (SWiFT) Facility.

Energy Technology Data Exchange (ETDEWEB)

Naughton, Brian Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Herges, Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-10-01

This report presents the objectives, configuration, procedures, reporting , roles , and responsibilities and subsequent results for the field demonstration of the Sandia Wake Imaging System (SWIS) at the Sandia Scaled Wind Farm Technology (SWiFT) facility near Lubbock, Texas in June and July 2015.

Whole farm management to reduce nutrient losses from dairy farms: a simulation study

NARCIS (Netherlands)

Rotz, C.A.; Oenema, J.; Keulen, van H.

2003-01-01

Whole farm simulation provides a tool for evaluating the impact of nutrient conservation technologies and strategies on dairy farms. A farm simulation model was verified by simulating the production and nutrient flows of the De Marke experimental dairy farm in the Netherlands. Technology such as a

Statistical modeling of the power grid from a wind farm standpoint

DEFF Research Database (Denmark)

Farajzadehbibalan, Saber; Ramezani, Mohammad H.; Nielsen, Peter

2017-01-01

wind farm over several years which results in the development of a useful model for practical purposes. Secondly, the derived model is computationally inexpensive. Considering an arbitrary wind turbine generator, we show that the behavior of the power grid at the connection point can be represented......In this study, we derive a statistical model of a power grid from the wind farm's standpoint based on dynamic principal component analysis. The main advantages of our model compared to the previously developed models are twofold. Firstly, our proposed model benefits from logged data of an offshore...... by 4 out of 9 registered variables, i.e. 3-phase voltages, 3-phase currents, frequency, and generated active and reactive powers. We further prove that the dynamic nature of the system can be optimally captured by a time lag shift of two samples. To extend the derived model of a wind turbine generator...

Farm-Level Effects of Soil Conservation and Commodity Policy Alternatives: Model and Data Documentation.

Science.gov (United States)

Sutton, John D.

This report documents a profit-maximizing linear programming (LP) model of a farm typical of a major corn-soybean producing area in the Southern Michigan-Northern Indiana Drift Plain. Following an introduction, a complete description of the farm is provided. The next section presents the LP model, which is structured to help analyze after-tax…

The effects of farm management practices on liver fluke prevalence and the current internal parasite control measures employed on Irish dairy farms.

Science.gov (United States)

Selemetas, Nikolaos; Phelan, Paul; O'Kiely, Padraig; de Waal, Theo

2015-01-30

Fasciolosis caused by Fasciola hepatica is responsible for major production losses in cattle farms. The objectives of this study were to assess the effect of farm management practices on liver fluke prevalence on Irish dairy farms and to document the current control measures against parasitic diseases. In total, 369 dairy farms throughout Ireland were sampled from October to December 2013, each providing a single bulk tank milk (BTM) sample for liver fluke antibody-detection ELISA testing and completing a questionnaire on their farm management. The analysis of samples showed that cows on 78% (n=288) of dairy farms had been exposed to liver fluke. There was a difference (P0.05) between positive and negative farms in (a) the grazing of dry cows together with replacement cows, (b) whether or not grazed grassland was mowed for conservation, (c) the type of drinking water provision system, (d) spreading of cattle manure on grassland or (e) for grazing season length (GSL; mean=262.5 days). Also, there were differences (Pmanagement practices between Irish farms with dairy herds exposed or not exposed to liver fluke and stressed the need of fine-scale mapping of the disease patterns even at farm level to increase the accuracy of risk models. Also, comprehensive advice and professional support services to farmers on appropriate farm management practices are very important for an effective anthelmintic control strategy. Copyright © 2014 Elsevier B.V. All rights reserved.

Antimicrobials in small-scale urban pig farming in a lower middle-income country - arbitrary use and high resistance levels.

Science.gov (United States)

Ström, G; Boqvist, S; Albihn, A; Fernström, L-L; Andersson Djurfeldt, A; Sokerya, S; Sothyra, T; Magnusson, U

2018-01-01

Administration of antimicrobials to food-producing animals is regarded as a major contributor to the overall emergence of resistance in bacteria worldwide. However, few data are available on global antimicrobial use and resistance (AMR) in livestock, especially from low- and middle-income countries. We conducted a structured survey of 91 small-scale pig farms in the urban and peri-urban areas of Phnom Penh, Cambodia, to assess the farmers' knowledge, attitudes and practices related to antimicrobial use in their pig production. Commensal Escherichia coli was isolated from three healthy pigs from each farm ( n  = 261) and susceptibility testing was performed against 14 antimicrobials, using broth microdilution. Univariable logistic regression and generalized linear mixed models were used to investigate potential associations between farm characteristics, management factors and resistance to different types of antimicrobials. We found a widespread and arbitrary use of antimicrobials, often based on the farmer's own judgment. Around 66% of the farmers reported frequently self-adjusting treatment duration and dosage, and 45% had not heard about the term 'antimicrobial resistance'. The antimicrobials most commonly mentioned or kept by the farmers were amoxicillin, tylosin, gentamicin and colistin. Around 37% used a feed concentrate that contained antimicrobials, while antimicrobials for humans were used as a last-line treatment by 10% of the farmers. Commensal E. coli exhibited high prevalence of resistance to several antimicrobials considered to be of critical importance for human medicine, including ampicillin, ciprofloxacin and colistin, and multidrug-resistance was found in 79% of the samples. Higher prevalence of resistance was observed on farms that administered prophylactic antimicrobials and on farms that treated the entire group or herd in the event of disease. The widespread and arbitrary use of antimicrobials in pig farming in Cambodia is highly worrisome

COMMUNICATION MODEL IN SOCIALIZING OF URBAN FARMING “KAMPUNG BERKEBUN” INNOVATION PROGRAM IN BANDUNG CITY (MODEL KOMUNIKASI DALAM MEMASYARAKATKAN PROGRAM INOVASI URBAN FARMING “KAMPUNG BERKEBUN” DI KOTA BANDUNG PROPINSI JAWA BARAT

Directory of Open Access Journals (Sweden)

Henny Sri Mulyani R

2016-10-01

Full Text Available An innovation promoted by the government of the city of Bandung in 2014 that urban gardening activities by utilizing their yards, vacant land, alley, dak  and the other, better known as Urban Farming. This activity was intended for residents of the city of Bandung with the hope of meeting the food needs of the household and supporting urban green open space. The purpose of this study was to determine the model of communication used by the Department of Agriculture and Food Security in the dissemination of innovation Urban Farming "Kampung Berkebun" in Bandung. This was accomplished through qualitative description methods of data collection and analysis using some observations, personal interviews and textual analysis. The results showed that the program of promoting Urban Farming "Kampung Berkebun" consists of two activities, namely the first event, to be disseminated to the subdistrict and village heads as the city of Bandung which is held at the Department of Agriculture and Food Security in Bandung, and the second activity is to provide training to the residents in the village location. Bandung has 34 districts and 151 villages. Training was conducted at each site include a village with a maximum of 50 people of the village residents. Deployment of innovative communication model Urban Farming "Kampung Berkebun" in the form of a model that is both mechanistic and interactional namely communication model David K Berlo (1960 and Schramm communication model (1954.   Sebuah inovasi  dimasyarakatkan oleh pemerintahan Kota Bandung mulai tahun 2014 yaitu kegiatan berkebun diperkotaan dengan memanfaatkan lahan pekarangan, lahan tidur, gang, dak  dan yang lainnya   lebih dikenal dengan sebutan  Urban Farming. Kegiatan ini diperuntukan bagi   warga Kota Bandung dengan harapan dapat memenuhi kebutuhan pangan dalam skala rumah tangga dan menunjang ruang terbuka hijau perkotaan. Tujuan penelitian ini adalah untuk mengetahui model komunikasi yang

Wind farms providing secondary frequency regulation: evaluating the performance of model-based receding horizon control

Directory of Open Access Journals (Sweden)

C. R. Shapiro

2018-01-01

Full Text Available This paper is an extended version of our paper presented at the 2016 TORQUE conference (Shapiro et al., 2016. We investigate the use of wind farms to provide secondary frequency regulation for a power grid using a model-based receding horizon control framework. In order to enable real-time implementation, the control actions are computed based on a time-varying one-dimensional wake model. This model describes wake advection and wake interactions, both of which play an important role in wind farm power production. In order to test the control strategy, it is implemented in a large-eddy simulation (LES model of an 84-turbine wind farm using the actuator disk turbine representation. Rotor-averaged velocity measurements at each turbine are used to provide feedback for error correction. The importance of including the dynamics of wake advection in the underlying wake model is tested by comparing the performance of this dynamic-model control approach to a comparable static-model control approach that relies on a modified Jensen model. We compare the performance of both control approaches using two types of regulation signals, RegA and RegD, which are used by PJM, an independent system operator in the eastern United States. The poor performance of the static-model control relative to the dynamic-model control demonstrates that modeling the dynamics of wake advection is key to providing the proposed type of model-based coordinated control of large wind farms. We further explore the performance of the dynamic-model control via composite performance scores used by PJM to qualify plants for regulation services or markets. Our results demonstrate that the dynamic-model-controlled wind farm consistently performs well, passing the qualification threshold for all fast-acting RegD signals. For the RegA signal, which changes over slower timescales, the dynamic-model control leads to average performance that surpasses the qualification threshold, but further

Multiscale effects of management, environmental conditions, and land use on nitrate leaching in dairy farms.

Science.gov (United States)

Oenema, Jouke; Burgers, Saskia; Verloop, Koos; Hooijboer, Arno; Boumans, Leo; ten Berge, Hein

2010-01-01

Nitrate leaching in intensive grassland- and silage maize-based dairy farming systems on sandy soil is a main environmental concern. Here, statistical relationships are presented between management practices and environmental conditions and nitrate concentration in shallow groundwater (0.8 m depth) at farm, field, and point scales in The Netherlands, based on data collected in a participatory approach over a 7-yr period at one experimental and eight pilot commercial dairy farms on sandy soil. Farm milk production ranged from 10 to 24 Mg ha(-1). Soil and hydrological characteristics were derived from surveys and weather conditions from meteorological stations. Statistical analyses were performed with multiple regression models. Mean nitrate concentration at farm scale decreased from 79 mg L(-1) in 1999 to 63 in 2006, with average nitrate concentration in groundwater decreasing under grassland but increasing under maize land over the monitoring period. The effects of management practices on nitrate concentration varied with spatial scale. At farm scale, nitrogen surplus, grazing intensity, and the relative areas of grassland and maize land significantly contributed to explaining the variance in nitrate concentration in groundwater. Mean nitrate concentration was negatively correlated to the concentration of dissolved organic carbon in the shallow groundwater. At field scale, management practices and soil, hydrological, and climatic conditions significantly contributed to explaining the variance in nitrate concentration in groundwater under grassland and maize land. We conclude that, on these intensive dairy farms, additional measures are needed to comply with the European Union water quality standard in groundwater of 50 mg nitrate L(-1). The most promising measures are omitting fertilization of catch crops and reducing fertilization levels of first-year maize in the rotation.

Sustainable Organic Farming For Environmental Health A Social Development Model

Directory of Open Access Journals (Sweden)

Ijun Rijwan Susanto

2015-05-01

Full Text Available ABSTRACT In this study the researcher attempted 1 to understand the basic features of organic farming in The Paguyuban Pasundans Cianjur 2 to describe and understand how the stakeholders were are able to internalize the challenges of organic farming on their lived experiences in the community 3 to describe and understand how the stakeholders were are able to internalize and applied the values of benefits of organic farming in support of environmental health on their lived experiences in the community 4 The purpose was to describe and understand how the stakeholders who are able to articulate their ideas regarding the model of sustainable organic farming 5 The Policy Recommendation for Organic Farming. The researcher employed triangulation thorough finding that provides breadth and depth to an investigation offering researchers a more accurate picture of the phenomenon. In the implementation of triangulation researchers conducted several interviews to get saturation. After completion of the interview results are written compiled and shown to the participants to check every statement by every participant. In addition researchers also checked the relevant documents and direct observation in the field The participants of this study were the stakeholders namely 1 The leader of Paguyuban Pasundans Organic Farmer Cianjur PPOFC 2 Members of Paguyuban Pasundans Organic FarmersCianjur 3 Leader of NGO 4 Government officials of agriculture 5 Business of organic food 6 and Consumer of organic food. Generally the findings of the study revealed the following 1 PPOFC began to see the reality as the impact of modern agriculture showed in fertility problems due to contaminated soil by residues of agricultural chemicals such as chemical fertilizers and chemical pesticides. So he wants to restore the soil fertility through environmentally friendly of farming practices 2 the challenges of organic farming on their lived experiences in the community farmers did not

Performance and optimisation of trickling filters on eel farms

NARCIS (Netherlands)

Kamstra, A.; Heul, van der J.W.; Nijhof, M.

1998-01-01

The design of trickling filters used on commercial eel farms differs considerably with respect to dimensions, hydraulic and substrate loads and filter medium applied. In this paper, a model, developed for ammonium removal in a pilot-scale trickling filter, has been validated for a range of

Sustainable agriculture: how to make it work? : a modeling approach to support management of a mixed ecological farm

NARCIS (Netherlands)

Wolfert, S.

2002-01-01

Keywords: sustainable agriculture; organic farming; whole farm management; decision support; farming systems research; designing; modeling; beta-gamma integration

The objective of the research described in this thesis was to develop a model that helps

An assessment of the commercial cost of farm scale wood fuel procurement and processing

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-11-01

The capital cost of small scale biomass fired systems is currently significantly higher than equivalent rated fossil fuel fired systems. If the cost of producing willow or poplar coppice derived fuel can be shown to offer significant savings over the cost of conventional fossil fuel alternatives, the resultant total cost of energy production could in fact be less. The production of ''home grown'' fuel should always, in theory, be cheaper than bought in supplies due to the removal of cost components such as profit and risk and the possible use of labour during traditionally quiet periods on the farm. However, it has not been shown to date that small scale coppice plantations can successfully produce cost effective wood fuel to displace fuel that would otherwise be 'bought in'. It is likely that fuel from coppice will be harvested on a semi-manual basis using brush cutters and farm loaders etc. This report identifies appropriate systems and provides estimates of the key costs to a grower. Particular emphasis is given to operations surrounding cut-back, harvesting and comminution. The report provides an outline of the statutory requirements of employers engaged in coppice management. Key costs have been presented in their most useful form for a potential grower to compile enterprise gross margins. (Author)

Heat and Flux. Increase of Wind Farm Production by Reduction of the Axial Induction

Energy Technology Data Exchange (ETDEWEB)

Corten, G.P.; Schaak, P. [ECN Wind Energy, Petten (Netherlands)

2003-10-01

At the windward side of a wind farm, we propose to operate the wind turbines at an axial induction factor below the Lanchester-Betz optimum of 1/3. Our analysis shows that the power of the turbines under the lee will increase more than the decrease of the power of the turbines at the windward side, so that the power of the farm as a whole increases. Measurements with a 1:400 scaled model of a wind farm confirmed the hypothesis.

Amaranth farming

DEFF Research Database (Denmark)

Bjarklev, Araceli; Kjær, Tyge; Kjærgård, Bente

2008-01-01

natural resources that small-scale farmers have to combat the abovementioned problems. The study identified several local and regional barriers for increasing the level of farming, production, processing and consumption. A striking and paradoxical limitation is the monopolization practices developed...

Spatial analysis and characteristics of pig farming in Thailand.

Science.gov (United States)

Thanapongtharm, Weerapong; Linard, Catherine; Chinson, Pornpiroon; Kasemsuwan, Suwicha; Visser, Marjolein; Gaughan, Andrea E; Epprech, Michael; Robinson, Timothy P; Gilbert, Marius

2016-10-06

In Thailand, pig production intensified significantly during the last decade, with many economic, epidemiological and environmental implications. Strategies toward more sustainable future developments are currently investigated, and these could be informed by a detailed assessment of the main trends in the pig sector, and on how different production systems are geographically distributed. This study had two main objectives. First, we aimed to describe the main trends and geographic patterns of pig production systems in Thailand in terms of pig type (native, breeding, and fattening pigs), farm scales (smallholder and large-scale farming systems) and type of farming systems (farrow-to-finish, nursery, and finishing systems) based on a very detailed 2010 census. Second, we aimed to study the statistical spatial association between these different types of pig farming distribution and a set of spatial variables describing access to feed and markets. Over the last decades, pig population gradually increased, with a continuously increasing number of pigs per holder, suggesting a continuing intensification of the sector. The different pig-production systems showed very contrasted geographical distributions. The spatial distribution of large-scale pig farms corresponds with that of commercial pig breeds, and spatial analysis conducted using Random Forest distribution models indicated that these were concentrated in lowland urban or peri-urban areas, close to means of transportation, facilitating supply to major markets such as provincial capitals and the Bangkok Metropolitan region. Conversely the smallholders were distributed throughout the country, with higher densities located in highland, remote, and rural areas, where they supply local rural markets. A limitation of the study was that pig farming systems were defined from the number of animals per farm, resulting in their possible misclassification, but this should have a limited impact on the main patterns revealed

Assessment of gastrointestinal nematode infection, anthelmintic usage and husbandry practices on two small-scale goat farms in Malaysia.

Science.gov (United States)

Wong, Flora; Sargison, Neil

2018-03-01

Haemonchosis is a common problem on goat farms in tropical countries such as Malaysia. Prevention of production losses generally depends on the use of anthelmintic drugs, but is threatened by the emergence of anthelmintic resistance. This study investigates anthelmintic efficacy on small-scale Malaysian goat farms and describes putative risk factors. Adult goats had moderate to high pre-treatment faecal trichostrongyle egg counts, despite being housed on slatted floors and fed on cut-and-carry forage, raising questions about the source of nematode infection. Our results show multiple resistance to benzimidazole and macrocyclic lactone anthelmintic drugs and allow us to discuss the genetic origins of resistance with reference to farm husbandry and management. We conclude that improvement in Malaysian goat production efficiency will require the development of sustainable helminth control strategies, underpinned by a better understanding of the origins and population genetics of anthelmintic resistance.

Transient stability risk assessment of power systems incorporating wind farms

DEFF Research Database (Denmark)

Miao, Lu; Fang, Jiakun; Wen, Jinyu

2013-01-01

fed induction generator has been established. Wind penetration variation and multiple stochastic factors of power systems have been considered. The process of transient stability risk assessment based on the Monte Carlo method has been described and a comprehensive risk indicator has been proposed......Large-scale wind farm integration has brought several aspects of challenges to the transient stability of power systems. This paper focuses on the research of the transient stability of power systems incorporating with wind farms by utilizing risk assessment methods. The detailed model of double....... An investigation has been conducted into an improved 10-generator 39-bus system with a wind farm incorporated to verify the validity and feasibility of the risk assessment method proposed....

A Wind Farm Controller for Load and Power Optimization in a Farm

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam; Brand, Arno; Wisniewski, Rafal

2011-01-01

This paper describes the design procedure of an optimal wind farm controller. The controller optimizes the structural load and power production simultaneously, on the basis of an analytical wind farm model. The farm model delivers maps of wind, loads and energy in the wind farm. Moreover, the model...... computes the wind speed at the turbines, turbine bending moments and aerodynamic power and torque. The optimal control problem is formulated based on the model for two different wind directions. The controller determines the reference signals for each individual wind turbine controller in two scenarios...... based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted, taking the trade-off between power maximization and load minimization into account. In high wind speed, the power and pitch angle reference signals are determined while structural loads are minimized....

Estimating landscape-scale impacts of agricultural management on soil carbon using measurements and models

Science.gov (United States)

Schipanski, M.; Rosenzweig, S. T.; Robertson, A. D.; Sherrod, L. A.; Ghimire, R.; McMaster, G. S.

2017-12-01

Agriculture covers 40% of Earth's ice-free land area and has broad impacts on global biogeochemical cycles. While some agricultural management changes are small in scale or impact, others have the potential to shift biogeochemical cycles at landscape and larger scales if widely adopted. Understanding which management practices have the potential to contribute to climate change adaptation and mitigation while maintaining productivity requires scaling up estimates spatially and temporally. We used on-farm, long-term, and landscape scale datasets to estimate how crop rotations impact soil organic carbon (SOC) accumulation rates under current and future climate scenarios across the semi-arid Central and Southern Great Plains. We used a stratified, landscape-scale soil sampling approach across 96 farm fields to evaluate crop rotation intensity effects on SOC pools and pesticide inputs. Replacing traditional wheat-fallow rotations with more diverse, continuously cropped rotations increased SOC by 17% and 12% in 0-10 cm and 0-20 cm depths, respectively, and reduced herbicide use by 50%. Using USDA Cropland Data Layer, we estimated soil C accumulation and pesticide reduction potentials of shifting to more intensive rotations. We also used a 30-year cropping systems experiment to calibrate and validate the Daycent model to evaluate rotation intensify effects under future climate change scenarios. The model estimated greater SOC accumulation rates under continuously cropped rotations, but SOC stocks peaked and then declined for all cropping systems beyond 2050 under future climate scenarios. Perennial grasslands were the only system estimated to maintain SOC levels in the future. In the Southern High Plains, soil C declined despite increasing input intensity under current weather while modest gains were simulated under future climate for sorghum-based cropping systems. Our findings highlight the potential vulnerability of semi-arid regions to climate change, which will be

Bio-economic farm modelling to analyse agricultural land productivity in Rwanda

NARCIS (Netherlands)

Bidogeza, J.C.

2011-01-01

Keywords: Rwanda; farm household typology; sustainable technology adoption; multivariate analysis;
land degradation; food security; bioeconomic model; crop simulation models; organic fertiliser; inorganic fertiliser; policy incentives

In Rwanda, land degradation contributes to the

Evaluation of a whole-farm model for pasture-based dairy systems.

Science.gov (United States)

Beukes, P C; Palliser, C C; Macdonald, K A; Lancaster, J A S; Levy, G; Thorrold, B S; Wastney, M E

2008-06-01

In the temperate climate of New Zealand, animals can be grazed outdoors all year round. The pasture is supplemented with conserved feed, with the amount being determined by seasonal pasture growth, genetics of the herd, and stocking rate. The large number of factors that affect production makes it impractical and expensive to use field trials to explore all the farm system options. A model of an in situ-grazed pasture system has been developed to provide a tool for developing and testing novel farm systems; for example, different levels of bought-in supplements and different levels of nitrogen fertilizer application, to maintain sustainability or environmental integrity and profitability. It consists of a software framework that links climate information, on a daily basis, with dynamic, mechanistic component-models for pasture growth and animal metabolism, as well as management policies. A unique feature is that the component models were developed and published by other groups, and are retained in their original software language. The aim of this study was to compare the model, called the whole-farm model (WFM) with a farm trial that was conducted over 3 yr and in which data were collected specifically for evaluating the WFM. Data were used from the first year to develop the WFM and data from the second and third year to evaluate the model. The model predicted annual pasture production, end-of-season cow liveweight, cow body condition score, and pasture cover across season with relative prediction error pasture and supplement intake were predicted with acceptable accuracy, suggesting that the metabolic conversion of feed to fat, protein, and lactose in the mammary gland needs to be refined. Because feed growth and intake predictions were acceptable, economic predictions can be made using the WFM, with an adjustment for milk yield, to test different management policies, alterations in climate, or the use of genetically improved animals, pastures, or crops.

Business models in urban farming: A comparative analysis of case studies from Spain, Italy and Germany

Directory of Open Access Journals (Sweden)

Pölling Bernd

2017-09-01

Full Text Available The “Urban Agriculture Europe” EU COST-Action (2012–2016 has shown that the complexity of urban agriculture (UA is hardly compressible into classic business management models and has proposed new management models, such as the Business Model Canvas (BMC. Business models of UA have to be different from rural ones. In particular, factors such as differentiation and diversification, but also low cost-oriented specialisation, are characteristic and necessary business models for UA to stay profitable in the long term under challenging city conditions. This paper aims to highlight how farm enterprises have to adjust to urban conditions by stepping into appropriate business models aiming to stay competitive and profitable, and how the BMC is useful to analyse their organisation and performance, both economically and socially. The paper offers an inter-regional analysis of UA enterprises located in Spain, Italy, and Germany, which are further subdivided into: local food, leisure, educational, social, therapeutic, agri-environmental, cultural heritage and experimental farms. The analysis demonstrates that UA is differentially adjusted to specific urban conditions and that the BMC is useful for analysing urban farming. Heterogeneous local food farms and the integration of local and organic food production in social farming business models are most frequent in our case studies.

EERA-DTOC Project: Design Tools for Offshore Wind Farm Clusters; Proyecto EERA-DTOC: herramientas para el diseno de clusters de Parques Eolicos Marinos

Energy Technology Data Exchange (ETDEWEB)

Palomares, A. M.

2015-07-01

In the EERA-DTOC Project an integrated and validated software design tool for the optimization of offshore wind farms and wind farm clusters has been developed. The CIEMAT contribution to this project has change the view on mesoscale wind forecasting models, which were not so far considered capable of modeling wind farm scale phenomena. It has been shown the ability of the WRF model to simulate the wakes caused by the wind turbines on the downwind ones (inter-turbine wakes within a wind farm) as well as the wakes between wind farms within a cluster. (Author)

Adjoint-based model predictive control of wind farms : Beyond the quasi steady-state power maximization

NARCIS (Netherlands)

Vali, M.; Petrović, Vlaho; Boersma, S.; van Wingerden, J.W.; Kuhn, Martin; Dochain, Denis; Henrion, Didier; Peaucelle, Dimitri

2017-01-01

In this paper, we extend our closed-loop optimal control framework for wind farms to minimize wake-induced power losses. We develop an adjoint-based model predictive controller which employs a medium-fidelity 2D dynamic wind farm model. The wind turbine axial induction factors are considered here

Farming System Evolution and Adaptive Capacity: Insights for Adaptation Support

Directory of Open Access Journals (Sweden)

Jami L. Dixon

2014-02-01

Full Text Available Studies of climate impacts on agriculture and adaptation often provide current or future assessments, ignoring the historical contexts farming systems are situated within. We investigate how historical trends have influenced farming system adaptive capacity in Uganda using data from household surveys, semi-structured interviews, focus-group discussions and observations. By comparing two farming systems, we note three major findings: (1 similar trends in farming system evolution have had differential impacts on the diversity of farming systems; (2 trends have contributed to the erosion of informal social and cultural institutions and an increasing dependence on formal institutions; and (3 trade-offs between components of adaptive capacity are made at the farm-scale, thus influencing farming system adaptive capacity. To identify the actual impacts of future climate change and variability, it is important to recognize the dynamic nature of adaptation. In practice, areas identified for further adaptation support include: shift away from one-size-fits-all approach the identification and integration of appropriate modern farming method; a greater focus on building inclusive formal and informal institutions; and a more nuanced understanding regarding the roles and decision-making processes of influential, but external, actors. More research is needed to understand farm-scale trade-offs and the resulting impacts across spatial and temporal scales.

Reducing non-allocative costs on Danish dairy farms

DEFF Research Database (Denmark)

Lund, Mogens; Jacobsen, Brian H.; Hansen, Lars C.E.

1993-01-01

inefficiencies are far more important for dairy farms than inefficiencies due to sub-optimal farm size. Non-proportional reductions are shown to be as important as reductions due to scale economies. The paper closes with a discussion of the implications for farm policy and management practice....

Trade-offs between pasture production and farmland bird conservation: exploration of options using a dynamic farm model.

Science.gov (United States)

Sabatier, R; Teillard, F; Rossing, W A H; Doyen, L; Tichit, M

2015-05-01

In European grassland landscapes, grazing and mowing play a key role for the maintenance of high-quality habitats that host important bird populations. As grasslands are also key resources for cattle feeding, there is a need to develop management strategies that achieve the double objective of production and biodiversity conservation. The objective of this study was to use a modelling approach to generate recognisable patterns of bird dynamics in farms composed of different land use proportions, and to compare their production and ecological dimensions. We developed a dynamic model, which linked grassland management to bird population dynamics at the field and farm levels. The model was parameterised for two types of suckling farms corresponding to contrasting levels of grassland intensification and for two bird species of high conservation value. A viability algorithm was used to define and assess viable management strategies for production and ecological performance so as to draw the shape of the relationship between both types of performances for the two types of farms. Our results indicated that, at the farm level, there was a farming system effect with a negative and non-linear relationship linking performance. Improving bird population maintenance was less costly in extensive farms compared with intensive farms. At the field level, the model predicted the timing and intensity of land use, maximising either production or ecological performance. The results suggested that multi-objective grassland management would benefit from public policies that consider levels of organisation higher than the field level, such as the farm or the landscape.

Wind tunnel study of the power output spectrum in a micro wind farm

International Nuclear Information System (INIS)

Bossuyt, Juliaan; Meyers, Johan; Howland, Michael F.; Meneveau, Charles

2016-01-01

Instrumented small-scale porous disk models are used to study the spectrum of a surrogate for the power output in a micro wind farm with 100 models of wind turbines. The power spectra of individual porous disk models in the first row of the wind farm show the expected -5/3 power law at higher frequencies. Downstream models measure an increased variance due to wake effects. Conversely, the power spectrum of the sum of the power over the entire wind farm shows a peak at the turbine-to-turbine travel frequency between the model turbines, and a near -5/3 power law region at a much wider range of lower frequencies, confirming previous LES results. Comparison with the spectrum that would result when assuming that the signals are uncorrelated, highlights the strong effects of correlations and anti-correlations in the fluctuations at various frequencies. (paper)

A system-level cost-of-energy wind farm layout optimization with landowner modeling

International Nuclear Information System (INIS)

Chen, Le; MacDonald, Erin

2014-01-01

Highlights: • We model the role of landowners in determining the success of wind projects. • A cost-of-energy (COE) model with realistic landowner remittances is developed. • These models are included in a system-level wind farm layout optimization. • Basic verification indicates the optimal COE is in-line with real-world data. • Land plots crucial to a project’s success can be identified with the approach. - Abstract: This work applies an enhanced levelized wind farm cost model, including landowner remittance fees, to determine optimal turbine placements under three landowner participation scenarios and two land-plot shapes. Instead of assuming a continuous piece of land is available for the wind farm construction, as in most layout optimizations, the problem formulation represents landowner participation scenarios as a binary string variable, along with the number of turbines. The cost parameters and model are a combination of models from the National Renewable Energy Laboratory (NREL), Lawrence Berkeley National Laboratory, and Windustry. The system-level cost-of-energy (COE) optimization model is also tested under two land-plot shapes: equally-sized square land plots and unequal rectangle land plots. The optimal COEs results are compared to actual COE data and found to be realistic. The results show that landowner remittances account for approximately 10% of farm operating costs across all cases. Irregular land-plot shapes are easily handled by the model. We find that larger land plots do not necessarily receive higher remittance fees. The model can help site developers identify the most crucial land plots for project success and the optimal positions of turbines, with realistic estimates of costs and profitability

Mathematical model of the Savannah River Site waste tank farm

International Nuclear Information System (INIS)

Smith, F.G. III.

1991-01-01

A mathematical model has been developed to simulate operation of the waste tank farm and the associated evaporator systems at the Savannah River Site. The model solves material balance equations to predict the volumes of liquid waste, salt, and sludge for all of the tanks within each of the evaporator systems. Additional logic is included to model the behavior of waste tanks not directly associated with the evaporators. Input parameters include the Material Management Plan forecast of canyon operations, specification of other waste sources for the evaporator systems, evaporator operating characteristics, and salt and sludge removal schedules. The model determines how the evaporators will operate, when waste transfers can be made, and waste accumulation rates. Output from the model includes waste tank contents, summaries of systems operations, and reports of space gain and the remaining capacity to store waste materials within the tank farm. Model simulations can be made to predict waste tank capacities on a daily basis for up to 20 years. The model is coded as a set of three computer programs designed to run on either IBM compatible or Apple Macintosh II personal computers

A mechanistic model for electricity consumption on dairy farms: Definition, validation, and demonstration

OpenAIRE

Upton, J.R.; Murphy, M.; Shallo, L.; Groot Koerkamp, P.W.G.; Boer, de, I.J.M.

2014-01-01

Our objective was to define and demonstrate a mechanistic model that enables dairy farmers to explore the impact of a technical or managerial innovation on electricity consumption, associated CO2 emissions, and electricity costs. We, therefore, (1) defined a model for electricity consumption on dairy farms (MECD) capable of simulating total electricity consumption along with related CO2 emissions and electricity costs on dairy farms on a monthly basis; (2) validated the MECD using empirical d...

Effects of the 2003 CAP Reform on Investments of Dutch Dairy Farms Simulations with a Household Production Model

NARCIS (Netherlands)

Peerlings, J.H.M.; Ooms, D.L.

2005-01-01

This paper develops a non-separable household production model capable of analyzing the effects of the 2003 CAP reform, and especially EU farm payments, on individual Dutch dairy farms. Model results show that the 2003 CAP reform farm payments do not fully compensate the income loss caused by the

Topsoil N-budget model in orchard farming to evaluate groundwater nitrate contamination

Science.gov (United States)

Wijayanti, Yureana; Budihardjo, Kadarwati; Sakamoto, Yasushi; Setyandito, Oki

2017-12-01

A small scale field research was conducted in an orchard farming area in Kofu, Japan, where nitrate contamination was found in groundwater. The purpose of assessing the leaching of nitrate in this study is to understand the transformation and transport process of N-source in topsoil that leads to nitrate contamination of groundwater. In order to calculate N-budget in the soil, the model was utilized to predict the nitrogen leaching. In this res earch, the N-budget model was modified to evaluate influence of precipitation and application pattern of fertilizer and manure compost. The result shows that at the time before the addition of manure compost and fertilizer, about 75% of fertilizer leach from topsoil. Every month, the average remaining nitrate in soil from fertilizer and manure compost are 22% and 50%, respectively. The accumulation of this monthly manure compost nitrate, which stored in soil, should be carefully monitored. It could become the potential source of nitrate leaching to groundwater in the future.

Analysis of Goat Farming on Integrated Farming System in Banyumas

Directory of Open Access Journals (Sweden)

NN Hidayat

2007-05-01

Full Text Available The objective of this research were : 1 to find out the income generated from goat farming and its contribution to farmer income in several farming combination, 2 to find out the economic efficiency in goat farming with paddy and fish production, 3 to determine factors affecting level of production and income in different farming system, partially and aggregately, and 4 to determine the best combination of farming which generated maximum income. Household farmer survey method was performed to conduct this research. Farming model chosen in this research was partial and average aggregate. Cobb-Douglas function were chosen to predict functional relationship. Result stated from this research were : 1 goat farming has a significant contribution in integrated farming system, 2 integrated farming (goat and paddy, goat and fish, and goat, fish and paddy in Banyumas district was economically efficient. 3 partially, factor affecting production level in goat farming was number of goat owned (P<0.01, factor affecting paddy production were urea application and number of land owned (P<0.01, TSP application (P<0.05 and man power (P<0.10. Furthermore, factor affecting fish farming were feed, breed and number of land owned (P<0.01; 4 aggregately, factor affecting integrated farming I were urea application and number of land owned (P<0.01, feed and number of land owned (P<0.01, number of goat owned (P<0.10 integrated farming II, where as in integrated farming III were number of paddy land area and breed (P<0.01 also number of goat owned (P<0.10; 5 integrated farming III (goat, paddy and fish farming gave the highest profit, which gave Rp 6.219.283,81 with relatively high efficiency. Therefore, goat farming could be an alternative solution to be developed in integrated farming and could be combined with other farming activities such as paddy and fish farming. (Animal Production 9(2: 105-110 (2007 Key Words : Goat, income, economic efficiency, survey, contribution

Assessment of N and P status at the landscape scale using environmental models and measurements

International Nuclear Information System (INIS)

Sonneveld, M.P.W.; Vos, J.A. de; Kros, J.; Knotters, M.; Frumau, A.; Bleeker, A.; Vries, W. de

2012-01-01

We assessed the compliance of a Dutch landscape, dominated by dairy farming, with environmental quality standards using a combination of model calculations and measurements. The total ammonia emission of 2.4 kton NH 3 yr −1 does not exceed the environmental quality standard (2.6 kton NH 3 yr −1 ). Nevertheless, the total N deposition (on average 24.4 kg N ha −1 yr −1 ) is such that critical N loads are exceeded at 53% of the nature areas. The deposited N mainly results from non-agricultural sources and agricultural sources outside the area (72%). The calculated average NO 3 − concentration in the upper groundwater does not exceed the 50 mg l −1 threshold. Calculated annual average N-total and P-total concentrations in discharge water are relatively high but these cannot be directly compared with thresholds for surface water. The results suggest that compliance monitoring at the landscape scale needs to include source indicators and cannot be based on state indicators alone. - Highlights: ► There is scope for environmental monitoring programs at the landscape scale. ► Landscape assessment of state indicators for N and P require models and measurements. ► Monitoring at the landscape scale needs to consider farm management indicators. - The compliance of an agricultural landscape with quality standards is investigated using a combination of model calculations and measurements.

Stories of Success and Struggle: California's Small Farms.

Science.gov (United States)

Warnert, Jeannette; McCue, Susan

1999-01-01

Describes the University of California's Small Farms Program, which aims to support the sustainability of small farms by providing small-scale farmers with state-of-the-art information, research, support networks, and technical assistance in technology adoption and decision making. Profiles four successful small farms that grow strawberries,…

Farm scale production of combined heat and power from biogas; Gaardsbaserad och gaardsnaera produktion av kraftvaerme fraan biogas

Energy Technology Data Exchange (ETDEWEB)

Lantz, Mikael

2010-08-15

The Swedish agricultural sector accounts for a significant and unutilized part of the Swedish biogas potential. There is also considerable interest among Swedish farmers to increase the production and utilization of biogas. The purpose of this study is to analyze the prerequisites for the production of combined heat and power (CHP) from biogas based on manure in different scale and with different technologies. The purpose is also to present economic calculations and the conditions required to reach profitability. Based on current economic conditions and with the assumptions made in the assessment, it is difficult to achieve profitability with conventional production of biogas. Levels of investment and operating costs are greatly dependent of scale and a larger biogas plant is normally more profitable than a smaller. There are, however, only marginal differences between a large farm based biogas plant and a much larger plant treating manure from several farms. The reason is that the positive effects of scale regarding investments, comparing the two plants, are reduced by increased costs for transportation and sanitation. However, the sanitation unit adapted at the large plant enables the plant to receive different external substrates such as food industry waste etc. resulting in a much higher biogas production per amount of treated substrate. The following conclusions are drawn in this study: - to achieve profitability in the production of CHP from biogas based on manure it is required, in most cases, that some of the heat produced could be used externally and that the digestate is given an economic value; - there are clear positive effects of scale between the smaller and the larger farm based biogas plant. However, differences are marginal between a large farm based biogas plant and a larger plant treating manure from several farms; - thermophilic operation could improve the profitability if used to increase the amount of substrate treated and especially if it is

Review of Recent Development of Dynamic Wind Farm Equivalent Models Based on Big Data Mining

Science.gov (United States)

Wang, Chenggen; Zhou, Qian; Han, Mingzhe; Lv, Zhan’ao; Hou, Xiao; Zhao, Haoran; Bu, Jing

2018-04-01

Recently, the big data mining method has been applied in dynamic wind farm equivalent modeling. In this paper, its recent development with present research both domestic and overseas is reviewed. Firstly, the studies of wind speed prediction, equivalence and its distribution in the wind farm are concluded. Secondly, two typical approaches used in the big data mining method is introduced, respectively. For single wind turbine equivalent modeling, it focuses on how to choose and identify equivalent parameters. For multiple wind turbine equivalent modeling, the following three aspects are concentrated, i.e. aggregation of different wind turbine clusters, the parameters in the same cluster, and equivalence of collector system. Thirdly, an outlook on the development of dynamic wind farm equivalent models in the future is discussed.

Farm-level risk factors for fish-borne zoonotic trematode infection in integrated small-scale fish farms in northern Vietnam.

Directory of Open Access Journals (Sweden)

Van Thi Phan

Full Text Available BACKGROUND: Northern Vietnam is an endemic region for fish-borne zoonotic trematodes (FZT, including liver and intestinal flukes. Humans acquire the FZT infection by eating raw or inadequately cooked fish. The production of FZT-free fish in aquaculture is a key component in establishing a sustainable program to prevent and control the FZT transmission to humans. Interventions in aquaculture should be based on knowledge of the main risk factors associated with FZT transmission. METHODOLOGY/PRINCIPAL FINDINGS: A longitudinal study was carried out from June 2006 to May 2007 in Nam Dinh province, Red River Delta to investigate the development and risk factors of FZT infections in freshwater cultured fish. A total of 3820 fish were sampled six times at two-month intervals from 96 fish farms. Logistic analysis with repeated measurements was used to evaluate potential risk factors based on information collected through questionnaire interviews with 61 fish farm owners. The results showed that the FZT infections significantly increased from first sampling in June to July 2006 (65% to sixth sampling in April to May, 2007 (76%. The liver fluke, Clonorchis sinensis and different zoonotic intestinal flukes including Haplochis pumilio, H. taichui, H. yokogawai, Centrocestus formosanus and Procerovum varium were found in sampled fish. Duration of fish cultured (sampling times, mebendazole drug self-medication of household members, presence of snails in the pond, and feeding fish with green vegetation collected outside fish farms all had a significant effect on the development of FZT prevalence in the fish. CONCLUSIONS/SIGNIFICANCE: The FZT prevalence in fish increased by 11 percentage points during a one-year culture period and the risk factors for the development of infection were identified. Results also highlight that the young fish are already highly infected when stocked into the grow-out systems. This knowledge should be incorporated into control

FSSIM, a bio-economic farm model for simulating the response of EU farming systems to agricultural and environmental policies

NARCIS (Netherlands)

Louhichi, K.; Kanellopoulos, A.; Janssen, S.J.C.; Flichman, G.; Blanco, M.; Hengsdijk, H.; Heckelei, T.; Berentsen, P.; Oude Lansink, A.G.J.M.; Ittersum, van M.K.

2010-01-01

The disciplinary nature of most existing farm models as well as the issue specific orientation of most of the studies in agricultural systems research are main reasons for the limited use and re-use of bio-economic modelling for the ex-ante integrated assessment of policy decisions. The objective of

Broiler farm size in relation tot sustainability aspects

NARCIS (Netherlands)

Horne, van P.L.M.; Leenstra, F.R.

2010-01-01

In the Netherlands the number of broiler farms has been reduced by 50%, while farm size doubled between 1990 and 2008. A debate on the positive and negative aspects of large farms emerge. Many entrepreneurs in the broiler sector use increase in scale as strategy to reduce production cost. However, a

Whole Farm Management to Reduce Nutrient Losses From Dairy Farms: A Simulation Study

OpenAIRE

Rotz, C.A.; Oenema, J.; Keulen, van, H.

2006-01-01

Whole-farm simulation provides a tool for evaluating long-term impacts of nutrient conservation technologies and strategies on dairy farms. A farm simulation model was verified to predict the production and nutrient flows of the De Marke experimental dairy farm in the Netherlands. On this farm, technologies such as a low ammonia emission barn floor, enclosed manure storage, manure injection into the soil, and intraseeding of a grass cover crop on corn land were used to reduce nitrogen loss an...

Mesoscale to microscale wind farm flow modeling and evaluation

DEFF Research Database (Denmark)

Sanz Rodrigo, Javier; Chávez Arroyo, Roberto Aurelio; Moriarty, Patrick

2017-01-01

The increasing size of wind turbines, with rotors already spanning more than 150m diameter and hub heights above 100m, requires proper modeling of the atmospheric boundary layer (ABL) from the surface to the free atmosphere. Furthermore, large wind farm arrays create their own boundary layer stru...

Development of FAST.Farm: A New Multiphysics Engineering Tool for Wind-Farm Design and Analysis

Energy Technology Data Exchange (ETDEWEB)

Jonkman, Jason; Annoni, Jennifer; Hayman, Greg; Jonkman, Bonnie; Purkayastha, Avi

2017-01-09

This paper presents the development of FAST.Farm, a new multiphysics tool applicable to engineering problems in research and industry involving wind farm performance and cost optimization that is needed to address the current underperformance, failures, and expenses plaguing the wind industry. Achieving wind cost-of-energy targets - which requires improvements in wind farm performance and reliability, together with reduced uncertainty and expenditures - has been eluded by the complicated nature of the wind farm design problem, especially the sophisticated interaction between atmospheric phenomena and wake dynamics and array effects. FAST.Farm aims to balance the need for accurate modeling of the relevant physics for predicting power performance and loads while maintaining low computational cost to support a highly iterative and probabilistic design process and system-wide optimization. FAST.Farm makes use of FAST to model the aero-hydro-servo-elastics of distinct turbines in the wind farm, and it is based on some of the principles of the Dynamic Wake Meandering (DWM) model, but avoids many of the limitations of existing DWM implementations.

Evaluating nitrogen taxation scenarios using the dynamic whole farm simulation model FASSET

DEFF Research Database (Denmark)

Berntsen, Jørgen; Petersen, Bjørn Molt; Jacobsen, B.H.

2003-01-01

The whole farm model FASSET ver. 1.0 was used for evaluation of the environmental and economic consequences of implementing different nitrogen taxes. The taxation policies analysed were a tax on nitrogen in mineral fertiliser, a tax on nitrogen in mineral fertiliser and imported animal feedstuff......, and a tax on the farm nitrogen surplus. In these scenarios, the tax price was equal to the price of the nitrogen in mineral fertilisers (0.67 € kg N−1). Four farm types were considered: arable on sandy soil, arable on loamy soil, pig production on sandy soil and pig production on loamy soil. Impacts...... of the taxes for each farm type on crop rotation, fertiliser use and pig production were estimated by the Linear Programming module of FASSET. The dynamic simulation module of FASSET evaluated the environmental and economic consequences of the new production plans. The social abatement cost of reducing nitrate...

THE INFORMATIONAL SYSTEM FOR RESOURSES ADMINISTRATION IN FISH FARMS

Directory of Open Access Journals (Sweden)

Adrian ZUGRAVU

2005-01-01

Full Text Available The informational system for aquaculture activities provide a financial planning and analysis tool.The software can also be of assistance to land-based farmers who want to more thoroughly utilizetheir water resources by developing small-scale fish farm systems to provide supplementary income.Informational model has been enhanced to produce a comprehensive software package foraquaculture feasibility modeling, financial planning, sales and harvesting planning and managementinformation tools.

Wind Farm-LA Coordinated Operation Mode and Dispatch Model in Wind Power Accommodation Promotion

Directory of Open Access Journals (Sweden)

Li Lin

2018-05-01

Full Text Available With the support of a smart grid, a load aggregator (LA that aggregates the demand response resources of small- and medium-sized customers to participate in the electricity market would be a novel way to promote wind power accommodation. This paper proposes a wind farm–LA coordinated operation mode (WLCOM, which enables LAs to deal with wind farms directly at an agreement price. Afterwards, according to the accommodation demand of the wind farm, a coordinated dispatch model taking advantage of the various response capabilities of different flexible loads is set up to maximize the revenue of the LA. A case study was conducted to demonstrate the effectiveness of the proposed WLCOM and the coordinated dispatch model. The demonstration indicates that: (a load fluctuations and wind curtailment were obviously reduced; and (b both the LA and the wind farm participating in coordinated operation obtained higher revenues. Factors that influence the accommodation level, as well as revenues of wind farms and LA, are also investigated.

Coordinated control strategy for hybrid wind farms with DFIG-based and PMSG-based wind farms during network unbalance

DEFF Research Database (Denmark)

Yao, Jun; Liu, Ruikuo; Zhou, Te

2017-01-01

This paper investigates the coordinated control strategy for a hybrid wind farm with doubly fed induction generator (DFIG)-based and direct-driven permanent-magnet synchronous generator (PMSG)-based wind farms during network unbalance. The negative-sequence current output capabilities of DFIG...... to the controllable operating regions, a targets selection scheme for each control unit is proposed to improve the stability of the hybrid wind farms containing both DFIG-based and PMSG-based wind farms during network unbalance, especially to avoid DFIG-based wind farm tripping from connected power grid under severe...... grid voltage unbalance conditions. Finally, the proposed coordinated control strategy is validated by the simulation results of a 30-MW-DFIG-based wind farm and a 30-MW-PMSG-based wind farm under different operation conditions and experimental results on a laboratory-scale experimental rig under severe...

The Socioeconomic Basis of Farm Enterprise Diversification Decisions.

Science.gov (United States)

Anosike, Nnamdi; Coughenour, C. Milton

1990-01-01

Examines research relating farm size inversely to specialization and directly to farm-enterprise diversification. Develops model of farm management decision making. Tests model using survey examining land tenure, off-farm work, education, and environmental factors. Concludes diversification linked to farm size, human capital, and environmental…

Processing cereal grains, thin stillage, and cheese whey to fuel ethanol in a farm-scale plant

Energy Technology Data Exchange (ETDEWEB)

Gibbons, W R; Westby, C A

1988-01-01

Hydrous fuel ethanol (95%) and distiller's wet grain (DWG) were produced in a farm-scale plant from corn, wheat, and grain sorghum particles of various sizes, from corn combined with thin stillage-whey, and from various other cereal grains. These variations were made in a search to find the best set of conditions for maximizing the energy balance and minimizing the cost of ethanol production. We found that the optimum hammermill screen size for corn, wheat, and grain sorghum was 1.59 - 2.38 mm. In tests with thin stillage and whey a higher energy balance (2.91) occurred when one part whey was mixed with three parts stillage, rather than the reverse (2.69). However, the reverse (three parts whey and one part stillage) gave a lower ethanol cost ($0.45 liter/sup -1/) than the original ($0.47 liter/sup -1/). Tests with various cereal grains (corn, oats, wheat, barley, rye, and grain sorghum) gave identical energy balance values (2.26) when 10% (v/v) ethanol beers were produced. However, rye ($0.50 liter/sup -1/), grain sorghum ($0.46 liter/sup -1/), and corn ($0.51 liter/sup -1/) yielded ethanol at the lowest net cost. Recommendations for farm-scale plants are also provided.

Velocity field in the wake of a hydropower farm equipped with Achard turbines

International Nuclear Information System (INIS)

Georgescu, A-M; Cosoiu, C I; Alboiu, N; Hamzu, Al; Georgescu, S C

2010-01-01

The study consists of experimental and numerical investigations related to the water flow in the wake of a hydropower farm, equipped with three Achard turbines. The Achard turbine is a French concept of vertical axis cross-flow marine current turbine, with three vertical delta-blades, which operates irrespective of the water flow direction. A farm model built at 1:5 scale has been tested in a water channel. The Achard turbines run in stabilized current, so the flow can be assumed to be almost unchanged in horizontal planes along the vertical z-axis, thus allowing 2D numerical modelling, for different farm configurations: the computational domain is a cross-section of all turbines at a certain z-level. The two-dimensional numerical model of that farm has been used to depict the velocity field in the wake of the farm, with COMSOL Multiphysics and FLUENT software, to compute numerically the overall farm efficiency. The validation of the numerical models with experimental results is performed via the measurement of velocity distribution, by Acoustic Doppler Velocimetry, in the wake of the middle turbine within the farm. Three basic configurations were studied experimentally and numerically, namely: with all turbines aligned on a row across the upstream flow direction; with turbines in an isosceles triangular arrangement pointing downstream; with turbines in an isosceles triangular arrangement pointing upstream. As long as the numerical flow in the wake fits the experiments, the numerical results for the power coefficient (turbine efficiency) are trustworthy. The farm configuration with all turbines aligned on a same row leads to lower values of the experimental velocities than the numerical ones, while the farm configurations where the turbines are in isosceles triangular arrangement, pointing downstream or upstream, present a better match between numerical and experimental data.

Assessing the impact of marine wind farms on birds through movement modelling

OpenAIRE

Masden, Elizabeth A.; Reeve, Richard; Desholm, Mark; Fox, Anthony D.; Furness, Robert W.; Haydon, Daniel T.

2012-01-01

Advances in technology and engineering, along with European Union renewable energy targets, have stimulated a rapid growth of the wind power sector. Wind farms contribute to carbon emission reductions, but there is a need to ensure that these structures do not adversely impact the populations that interact with them, particularly birds. We developed movement models based on observed avoidance responses of common eider Somateria mollissima to wind farms to predict, and identify potential measu...

ECONOMICS OF DAIRY FARMING IN TURKEY

Directory of Open Access Journals (Sweden)

Özgür Bor

2014-10-01

Full Text Available In this study dairy farming activities in Turkey are employed to prove that small-scale agricultural production is disappearing rapidly due to costly investment and mechanization needs. For that purpose the cost structure and the investment needs in starting a dairy farm are analyzed. The results show that the capital requirements of building a dairy farm with optimal capacity are hard to reach for small farmers unless a system of marketing and production agricultural cooperatives and/or institutions are organized.

Development of FAST.Farm: A New Multiphysics Engineering Tool for Wind Farm Design and Analysis: Preprint

Energy Technology Data Exchange (ETDEWEB)

Jonkman, Jason; Annoni, Jennifer; Hayman, Greg; Jonkman, Bonnie; Purkayastha, Avi

2017-01-01

This paper presents the development of FAST.Farm, a new multiphysics tool applicable to engineering problems in research and industry involving wind farm performance and cost optimization that is needed to address the current underperformance, failures, and expenses plaguing the wind industry. Achieving wind cost-of-energy targets - which requires improvements in wind farm performance and reliability, together with reduced uncertainty and expenditures - has been eluded by the complicated nature of the wind farm design problem, especially the sophisticated interaction between atmospheric phenomena and wake dynamics and array effects. FAST.Farm aims to balance the need for accurate modeling of the relevant physics for predicting power performance and loads while maintaining low computational cost to support a highly iterative and probabilistic design process and system-wide optimization. FAST.Farm makes use of FAST to model the aero-hydro-servo-elastics of distinct turbines in the wind farm, and it is based on some of the principles of the Dynamic Wake Meandering (DWM) model, but avoids many of the limitations of existing DWM implementations.

Wake effects of large offshore wind farms on the mesoscale atmosphere

DEFF Research Database (Denmark)

Volker, Patrick; Badger, Jake; Hahmann, Andrea N.

to the fact that its typical horizontal grid spacing is on the order of 2km, the energy extracted by the turbine, as well as the wake development inside the turbine-containing grid-cells, are not described explicitly, but are parametrized as another sub-grid scale process. In order to appropriately capture...... the wind farm wake recovery and its direction, two properties are important, the total energy extracted by the wind farm and its velocity deficit distribution. In the considered parametrization the individual turbines apply a thrust dependent on a local sub grid scale velocity, which is influenced...... by the up-stream turbines. For the sub-grid scale velocity deficit, the entrainment from the free atmospheric flow into the wake region, is taken into account. Furthermore, since the model horizontal distance is several times larger then the turbine diameter, it has been assumed that the generated...

Intra-Household Impacts of Small Farm Commercialization of Maize ...

African Journals Online (AJOL)

This study was designed to analyze the impacts of small farm commercialization of maize enterprise on farming households in Abia State, Nigeria. Data were collected from 150 farming households through interview schedule and analysed using tables, percentages, a 4-scale Likert-type ranking method and ordinary least ...

The effect of a giant wind farm on precipitation in a regional climate model

International Nuclear Information System (INIS)

Fiedler, B H; Bukovsky, M S

2011-01-01

The Weather Research and Forecasting (WRF) model is employed as a nested regional climate model to study the effect of a giant wind farm on warm-season precipitation in the eastern two-thirds of the USA. The boundary conditions for WRF are supplied by 62 years of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) global reanalysis. In the model, the presence of a mid-west wind farm, either giant or small, can have an enormous impact on the weather and the amount of precipitation for one season, which is consistent with the known sensitivity of long-term weather forecasts to initial conditions. The effect on climate is less strong. In the average precipitation of 62 warm seasons, there is a statistically significant 1.0% enhancement of precipitation in a multi-state area surrounding and to the south-east of the wind farm.

Exploring diversity of crop and soil management within smallholder African farms: A dynamic model for simulation of N balances and use efficiencies at field scale

NARCIS (Netherlands)

Tittonell, P.A.; Leffelaar, P.A.; Vanlauwe, B.; Wijk, van M.T.; Giller, K.E.

2006-01-01

Adding a dynamic, temporal dimension to the calculation of nitrogen balances is proposed as an alternative approach to assessing the impact of crop and soil management decisions on the establishment of farmer-induced soil fertility gradients within smallholder African farms. A simulation model that

Havsnaes wind farm - The project financing of a Swedish wind farm

Energy Technology Data Exchange (ETDEWEB)

NONE

2012-07-01

In March 2008 the ground breaking project financing of the 95 MW Havsnaes wind farm was completed. Havsnaes represents one of the cornerstones in portfolio of Venus Vind, controlled by HgCapital, where sustainable Scandinavian strength is build through industrial scale wind farms with local presence. At the time, Havsnaes represented the largest energy project financing in the market, it is also the first true project financing of a major Swedish wind farm. The aim of this study is to highlight the process of project financing and additional lessons learnt from the Havsnaes transaction. Investment in renewable energy projects often includes international investors. We welcome the growing Swedish wind market, banks and other financial institutions, politicians and other relevant decision makers to take part of our findings. Sponsorship provided by the Swedish Energy Agency has enabled the completion of this study.

A Bayesian network approach to knowledge integration and representation of farm irrigation: 1. Model development

Science.gov (United States)

Wang, Q. J.; Robertson, D. E.; Haines, C. L.

2009-02-01

Irrigation is important to many agricultural businesses but also has implications for catchment health. A considerable body of knowledge exists on how irrigation management affects farm business and catchment health. However, this knowledge is fragmentary; is available in many forms such as qualitative and quantitative; is dispersed in scientific literature, technical reports, and the minds of individuals; and is of varying degrees of certainty. Bayesian networks allow the integration of dispersed knowledge into quantitative systems models. This study describes the development, validation, and application of a Bayesian network model of farm irrigation in the Shepparton Irrigation Region of northern Victoria, Australia. In this first paper we describe the process used to integrate a range of sources of knowledge to develop a model of farm irrigation. We describe the principal model components and summarize the reaction to the model and its development process by local stakeholders. Subsequent papers in this series describe model validation and the application of the model to assess the regional impact of historical and future management intervention.

Modelling Infectious Hematopoietic Necrosis Virus Dispersion from Marine Salmon Farms in the Discovery Islands, British Columbia, Canada.

Directory of Open Access Journals (Sweden)

Michael G G Foreman

Full Text Available Finite volume ocean circulation and particle tracking models are used to simulate water-borne transmission of infectious hematopoietic necrosis virus (IHNV among Atlantic salmon (Salmo salar farms in the Discovery Islands region of British Columbia, Canada. Historical simulations for April and July 2010 are carried out to demonstrate the seasonal impact of river discharge, wind, ultra-violet (UV radiation, and heat flux conditions on near-surface currents, viral dispersion and survival. Numerical particles released from infected farm fish in accordance with IHNV shedding rates estimated through laboratory experiments are dispersed by model oceanic flows. Viral particles are inactivated by ambient UV radiation levels and by the natural microbial community at rates derived through laboratory studies. Viral concentration maps showing temporal and spatial changes are produced and combined with lab-determined minimum infectious dosages to estimate the infective connectivity among farms. Results demonstrate that neighbouring naïve farms can become exposed to IHNV via water-borne transport from an IHNV diseased farm, with a higher risk in April than July, and that many events in the sequence of farm outbreaks in 2001-2002 are consistent with higher risks in our farm connectivity matrix. Applications to other diseases, transfers between farmed and wild fish, and the effect of vaccinations are also discussed.

Wind resource modelling for micro-siting - Validation at a 60-MW wind farm site

Energy Technology Data Exchange (ETDEWEB)

Hansen, J C; Gylling Mortensen, N [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark); Said, U S [New and Renewable Energy Authority, Cairo (Egypt)

1999-03-01

This paper investigates and validates the applicability of the WAsP-model for layout optimization and micro-siting of wind turbines at a given site for a 60-MW wind farm at Zafarana at the Gulf of Suez in Egypt. Previous investigations show large gradients in the wind climate within the area. For the design and optimization of the wind farm it was found necessary to verify the WAsP extrapolation of wind atlas results from 2 existing meteorological masts located 5 and 10 km, respectively, from the wind farm site. On-site measurements at the 3.5 x 3.5 km{sup 2} wind farm site in combination with 7 years of near-site wind atlas measurements offer significant amounts of data for verification of wind conditions for micro-siting. Wind speeds, wind directions, turbulence intensities and guests in 47.5 m a.g.l. have been measured at 9 locations across the site. Additionally, one of the site masts is equipped as a reference mast, measuring both vertical profiles of wind speed and temperature as well as air pressure and temperature. The exercise is further facilitated by the fact that winds are highly uni-directional; the north direction accounting for 80-90% of the wind resource. The paper presents comparisons of 5 months of on-site measurements and modeled predictions from 2 existing meteorological masts located at distances of 5 and 10 km, respectively, from the wind farm site. Predictions based on terrain descriptions of the Wind Atlas for the Gulf of Suez 1991-95 showed over-predictions of wind speeds of 4-10%. With calibrated terrain descriptions, made based on measured data and a re-visit to critical parts of the terrain, the average prediction error of wind speeds was reduced to about 1%. These deviations are smaller than generally expected for such wind resource modeling, clearly documenting the validity of using WAsP modeling for micro-siting and layout optimization of the wind farm. (au)

A fast wind-farm boundary-layer model to investigate gravity wave effects and upstream flow deceleration

Science.gov (United States)

Allaerts, Dries; Meyers, Johan

2017-11-01

Wind farm design and control often relies on fast analytical wake models to predict turbine wake interactions and associated power losses. Essential input to these models are the inflow velocity and turbulent intensity at hub height, which come from prior measurement campaigns or wind-atlas data. Recent LES studies showed that in some situations large wind farms excite atmospheric gravity waves, which in turn affect the upstream wind conditions. In the current study, we develop a fast boundary-layer model that computes the excitation of gravity waves and the perturbation of the boundary-layer flow in response to an applied force. The core of the model is constituted by height-averaged, linearised Navier-Stokes equations for the inner and outer layer, and the effect of atmospheric gravity waves (excited by the boundary-layer displacement) is included via the pressure gradient. Coupling with analytical wake models allows us to study wind-farm wakes and upstream flow deceleration in various atmospheric conditions. Comparison with wind-farm LES results shows excellent agreement in terms of pressure and boundary-layer displacement levels. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

Optimized Placement of Wind Turbines in Large-Scale Offshore Wind Farm using Particle Swarm Optimization Algorithm

DEFF Research Database (Denmark)

Hou, Peng; Hu, Weihao; Soltani, Mohsen

2015-01-01

With the increasing size of wind farm, the impact of the wake effect on wind farm energy yields become more and more evident. The arrangement of the wind turbines’ (WT) locations will influence the capital investment and contribute to the wake losses which incur the reduction of energy production....... As a consequence, the optimized placement of the wind turbines may be done by considering the wake effect as well as the components cost within the wind farm. In this paper, a mathematical model which includes the variation of both wind direction and wake deficit is proposed. The problem is formulated by using...... Levelized Production Cost (LPC) as the objective function. The optimization procedure is performed by Particle Swarm Optimization (PSO) algorithm with the purpose of maximizing the energy yields while minimizing the total investment. The simulation results indicate that the proposed method is effective...

Loads in wind farms under non-neutral ABL stability conditions: A full-scale validation study of the DWM model

DEFF Research Database (Denmark)

The purpose of this study is twofold: To validate a generalized version of the DWM approach for load prediction under non-neural atmospheric stability conditions, and to demonstrate the importance of atmospheric stability for wind turbines operating in wind farm conditions.......The purpose of this study is twofold: To validate a generalized version of the DWM approach for load prediction under non-neural atmospheric stability conditions, and to demonstrate the importance of atmospheric stability for wind turbines operating in wind farm conditions....

基于等效风速的风电场等值建模%Equivalent model of wind farm By Using the Equivalent Wind Speed

Institute of Scientific and Technical Information of China (English)

严干贵; 李鸿博; 穆钢; 崔杨; 刘玉

2011-01-01

With the increasing scale of the integration of wind power into power grids,the influence of wind power fluctuation begins even more significant on the power system,and therefore the modeling of wind farms has become an important research topic.In this paper,a new equivalent model of wind farm is proposed to represent the collective behavior of all the generator units for large power systems simulations,instead of using a complete model of wind farms where all the wind turbines are modeled.The model proposed here is based on aggregating wind turbines into an equivalent wind turbine which receives an equivalent wind of the ones incident on the aggregated wind turbines and generates the same power as the sum of all the wind turbines.Among the possible wind combinations of all wind turbines,the wind which is the most relative with the output power of all the wind turbines selected as the equivalent wind,and the concept and the calculation method of wind energy conversion efficiency is also proposed.The equivalent model of a wind farm equipped with 58 doublyfed induction wind turbines is established using the method proposed here,and the output power of the wind farm is also calculated using the model and is compared with the actual value of the wind farm.The validity of the model is also verified.The proposed equivalent model can be used for fast calculation of the output power of wind farm with given wind conditions and suitable for large-scale simulation of.wind farm interconnection to power grids.%随着风电场联网规模的不断扩大,风电功率波动对电网影响愈加显著,风电场建模已成为一项重要研究课题。本文提出了用一台等值机来表征场内风电机组整体性能的风电场等值模型,该等值机�

A Hidden Markov Model Representing the Spatial and Temporal Correlation of Multiple Wind Farms

DEFF Research Database (Denmark)

Fang, Jiakun; Su, Chi; Hu, Weihao

2015-01-01

To accommodate the increasing wind energy with stochastic nature becomes a major issue on power system reliability. This paper proposes a methodology to characterize the spatiotemporal correlation of multiple wind farms. First, a hierarchical clustering method based on self-organizing maps is ado....... The proposed statistical modeling framework is compatible with the sequential power system reliability analysis. A case study on optimal sizing and location of fast-response regulation sources is presented.......To accommodate the increasing wind energy with stochastic nature becomes a major issue on power system reliability. This paper proposes a methodology to characterize the spatiotemporal correlation of multiple wind farms. First, a hierarchical clustering method based on self-organizing maps...... is adopted to categorize the similar output patterns of several wind farms into joint states. Then the hidden Markov model (HMM) is then designed to describe the temporal correlations among these joint states. Unlike the conventional Markov chain model, the accumulated wind power is taken into consideration...

Energy Dynamics of an Infinitely Large Offshore Wind Farm

DEFF Research Database (Denmark)

Frandsen, Sten Tronæs; Barthelmie, R.J.; Pryor, S.C.

, particularly in the near-term, can be expected in the higher resource, moderate water depths of the North Sea rather than the Mediterranean. There should therefore be significant interest in understanding the energy dynamics of the infinitely large wind farm – how wakes behave and whether the extraction...... of energy by wind turbines over a large area has a significant and lasting impact on the atmospheric boundary layer. Here we focus on developing understanding of the infinite wind farm through a combination of theoretical considerations, data analysis and modeling. Initial evaluation of power losses due...... is of about the same magnitude as for the infinitely large wind farm. We will examine whether this can be proved theoretically or is indicated by data currently available. We will also evaluate whether energy extraction at the likely scale of development in European Seas can be expected to modulate...

Development of a wind farm noise propagation prediction model - project progress to date

International Nuclear Information System (INIS)

Robinson, P.; Bullmore, A.; Bass, J.; Sloth, E.

1998-01-01

This paper describes a twelve month measurement campaign which is part of a European project (CEC Project JOR3-CT95-0051) with the aim to substantially reduce the uncertainties involved in predicting environmentally radiated noise levels from wind farms (1). This will be achieved by comparing noise levels measure at varying distances from single and multiple sources over differing complexities of terrain with those predicted using a number of currently adopted sound propagation models. Specific objectives within the project are to: establish the important parameters controlling the propagation of wind farm noise to the far field; develop a planning tool for predicting wind farm noise emission levels under practically encountered conditions; place confidence limits on the upper and lower bounds of the noise levels predicted, thus enabling developers to quantify the risk whether noise emission from wind farms will cause nuisance to nearby residents. (Author)

Diversity in the dry land mixed system and viability of dairy sheep farming

Directory of Open Access Journals (Sweden)

Jose Rivas

2015-05-01

Full Text Available Castilla La Mancha is a Spanish region where sheep farming system is traditionally pasture-based. Recently, this territory has undergone a recession of dairy sheep activity, which changed the type and intensity of land utilization and led to environmental and landscape degradation. The present study analyzed the diversity and viability of dairy sheep of mixed systems. Multivariate analysis was conducted on 157 dairy sheep farms, factor analysis selected 3 productivity factors (level of intensification, land use, size and family labour, and cluster analysis classified farms into three groups. Group 1, smallholders – with the smallest size (405.5 ewes and 564.7 ha, lowest area in ownership (1.5%, and agriculture activity (6.5% crops area: family farms (90.8% highly dependent on external inputs. Group 2, large-scale farms (1058.7 ewes and 1755.1 ha – with the lowest stocking rate (0.14 livestock unit/ha and productivity: nonfamily farms (39.1% with low area in ownership (4.1% and agriculture activity (7.6%. Group 3, mixed-technified – with the highest levels of technology and least use of family labour (27.0%: large-scale farms (1387.4 ewes and 955.8 ha, combining milk production with agricultural activities (55.7% crops area, with the highest area in ownership (63.1% and the best productivity performance. In conclusion, the dry land mixed system of Castilla La Mancha showed diversity of farms. Improving viability requires a systemic approach where the key tool is grazing, allowing the mixed system to be consolidated as a model that enhances the positive impact of livestock on the environment in the Mediterranean basin.

Values, attitudes and intention to consume wild fish versus farmed fish in Nha Trang

OpenAIRE

Nelka Rajani, Pemattuge

2010-01-01

The primary purpose of this study was to investigate the consumers’ values and the difference in consumption, attitude and intention to consume wild fish versus farmed fish in Vietnam. Second, it aimed to investigate the relationship between values, attitudes and intention to consume wild versus farmed fish by applying value-attitude-behavior model. The measurement scales used here were adapted from previous studies found in the literature. The survey was conducted in Nha Trang, Vietnam, amon...

A high performance finite element model for wind farm modeling in forested areas

Science.gov (United States)

Owen, Herbert; Avila, Matias; Folch, Arnau; Cosculluela, Luis; Prieto, Luis

2015-04-01

Wind energy has grown significantly during the past decade and is expected to continue growing in the fight against climate change. In the search for new land where the impact of the wind turbines is small several wind farms are currently being installed in forested areas. In order to optimize the distribution of the wind turbines within the wind farm the Reynolds Averaged Navier Stokes equations are solved over the domain of interest using either commercial or in house codes. The existence of a canopy alters the Atmospheric Boundary Layer wind profile close to the ground. Therefore in order to obtain a more accurate representation of the flow in forested areas modification to both the Navier Stokes and turbulence variables equations need to be introduced. Several existing canopy models have been tested in an academic problem showing that the one proposed by Sogachev et. al gives the best results. This model has been implemented in an in house CFD solver named Alya. It is a high performance unstructured finite element code that has been designed from scratch to be able to run in the world's biggest supercomputers. Its scalabililty has recently been tested up to 100000 processors in both American and European supercomputers. During the past three years the code has been tuned and tested for wind energy problems. Recent efforts have focused on the canopy model following industry needs. In this work we shall benchmark our results in a wind farm that is currently being designed by Scottish Power and Iberdrola in Scotland. This is a very interesting real case with extensive experimental data from five different masts with anemometers at several heights. It is used to benchmark both the wind profiles and the speed up obtained between different masts. Sixteen different wind directions are simulated. The numerical model provides very satisfactory results for both the masts that are affected by the canopy and those that are not influenced by it.

Combined Active and Reactive Power Control of Wind Farms based on Model Predictive Control

DEFF Research Database (Denmark)

Zhao, Haoran; Wu, Qiuwei; Wang, Jianhui

2017-01-01

This paper proposes a combined wind farm controller based on Model Predictive Control (MPC). Compared with the conventional decoupled active and reactive power control, the proposed control scheme considers the significant impact of active power on voltage variations due to the low X=R ratio...... of wind farm collector systems. The voltage control is improved. Besides, by coordination of active and reactive power, the Var capacity is optimized to prevent potential failures due to Var shortage, especially when the wind farm operates close to its full load. An analytical method is used to calculate...... the sensitivity coefficients to improve the computation efficiency and overcome the convergence problem. Two control modes are designed for both normal and emergency conditions. A wind farm with 20 wind turbines was used to verify the proposed combined control scheme....

Dynamic modelling of VSC-HVDC for connection of offshore wind farms

DEFF Research Database (Denmark)

Rios, Bardo; Garcia-Valle, Rodrigo

2011-01-01

A VSC-HVDC (Voltage Source Converter – High Voltage Direct Current) dynamic model with a set of control strategies is developed in DIgSILENT Power-Factory with the objective of analyzing the converter’s operating capability for grid support during grid faults. The investigation is carried out based...... on a 165 MW offshore wind farm with induction generators and a Low Voltage Ride-Through solution of the offshore wind turbines and Static Voltage Compensator units in the point of connection with a grid represented by a reduced four-generator power grid model. VSC-HVDC promises to be a reliable alternative...... solution for interconnection with off-shore wind farms as they become larger, with a higher installed power capacity, increased number of wind turbines, and geographically situated at larger distances from suitable connection points in the transmission grids....

Comparing organic farming and land sparing: optimizing yield and butterfly populations at a landscape scale.

Science.gov (United States)

Hodgson, Jenny A; Kunin, William E; Thomas, Chris D; Benton, Tim G; Gabriel, Doreen

2010-11-01

Organic farming aims to be wildlife-friendly, but it may not benefit wildlife overall if much greater areas are needed to produce a given quantity of food. We measured the density and species richness of butterflies on organic farms, conventional farms and grassland nature reserves in 16 landscapes. Organic farms supported a higher density of butterflies than conventional farms, but a lower density than reserves. Using our data, we predict the optimal land-use strategy to maintain yield whilst maximizing butterfly abundance under different scenarios. Farming conventionally and sparing land as nature reserves is better for butterflies when the organic yield per hectare falls below 87% of conventional yield. However, if the spared land is simply extra field margins, organic farming is optimal whenever organic yields are over 35% of conventional yields. The optimal balance of land sparing and wildlife-friendly farming to maintain production and biodiversity will differ between landscapes. © 2010 Blackwell Publishing Ltd/CNRS.

The Technical Efficiency of Specialised Milk Farms: A Regional View

Directory of Open Access Journals (Sweden)

Jindřich Špička

2014-01-01

Full Text Available The aim of the article is to evaluate production efficiency and its determinants of specialised dairy farming among the EU regions. In the most of European regions, there is a relatively high significance of small specialised farms including dairy farms. The DEAVRS method (data envelopment analysis with variable returns to scale reveals efficient and inefficient regions including the scale efficiency. In the next step, the two-sample t-test determines differences of economic and structural indicators between efficient and inefficient regions. The research reveals that substitution of labour by capital/contract work explains the variability of the farm net value added per AWU (annual work unit income indicator by more than 30%. The significant economic determinants of production efficiency in specialised dairy farming are farm size, herd size, crop output per hectare, productivity of energy, and capital (at α=0.01. Specialised dairy farms in efficient regions have significantly higher farm net value added per AWU than inefficient regions. Agricultural enterprises in inefficient regions have a more extensive structure and produce more noncommodity output (public goods. Specialised dairy farms in efficient regions have a slightly higher milk yield, specific livestock costs of feed, bedding, and veterinary services per livestock unit.

Residents' Perceptions toward Utility-Scale Wind Farm Development

Science.gov (United States)

Campbell, Joseph; Romich, Eric

2015-01-01

Increased development of wind farms in the U.S. has fostered debates surrounding the siting and support for the projects. Prior research demonstrates the importance of understanding the attitudes and opinions of community members when developing projects. This article reviews a case study of an Ohio community that integrated a local survey to…

COMPARATIVE ANALYSIS OF THE ORGANIZATIONAL MODELS IN ORGANIC FARMING

Directory of Open Access Journals (Sweden)

Alexandra MUSCĂNESCU

2013-10-01

Full Text Available As regards to organic farming, organic farms have a lot of shortcomings in ensuring smooth organization of production due to climatic factors or crop sensitivity and action of pests and diseases, but especially to the high cost of inputs, reduced subsidies and difficulties in obtaining fair prices on the market. Understanding how the organizational structure of the business can compete to ensure efficiency at farm level is an important means to resolve these deficiencies. In this context, this paper aims to identify the characteristics of the organization of organic crop farms starting from an interview-based analysis of two large crop specialised farms in Tulcea and Calaraşi Counties. The information obtained through this method of investigation has been translated into a SWOT analysis and represented the basis for comparison with information gathered from other interviews from two organic farms in Scotland. The main conclusions we reached highlight two types of organization systems, one without integration and another with supply chain integration, very similar to the Scottish ones, but also showing a very obvious difference in the mentality of the farm owners; Romanians focusing on meeting the conditions for certification and maintenance of crops in organic, and the Scots at finding new markets.

Stochastic bio-economic modeling of mastitis in Ethiopian dairy farms.

Science.gov (United States)

Getaneh, Abraham Mekibeb; Mekonnen, Sefinew Alemu; Hogeveen, Henk

2017-03-01

Mastitis is an inflammation of the mammary gland that is considered to be one of the most frequent and costly diseases in the dairy industry. Also in Ethiopia, bovine mastitis is one of the most frequently encountered diseases of dairy cows. However, there was no study, so far, regarding the costs of clinical mastitis and only two studies were reported on costs of subclinical mastitis. Presenting an appropriate and complete study of the costs of mastitis will help farmers in making management decisions for mastitis control. The objective of this study was to estimate the economic effects of mastitis on Ethiopian market-oriented dairy farms. Market-oriented dairy farming is driven by making profits through selling milk in the market on a regular basis. A dynamic stochastic Monte-Carlo simulation model (bio-economic model) was developed taking into account both clinical and subclinical mastitis. Production losses, culling, veterinarian costs, treatment, discarded milk, and labour were the main cost factors which were modeled in this study. The annual incidence of clinical mastitis varied from 0 to 50% with a mean annual incidence of 21.6%, whereas the mean annual incidence of subclinical mastitis was 36.2% which varied between 0 and 75%. The total costs due to mastitis for a default farm size of 8 lactating cows were 6,709 ETB per year (838 ETB per cow per year). The costs varied considerably, with 5th and 95th percentiles of 109 ETB and 22,009 ETB, respectively. The factor most contributing to the total annual cost of mastitis was culling. On average a clinical case costs 3,631 ETB, varying from 0 to 12,401, whereas a sub clinical case costs 147 ETB, varying from 0 to 412. The sensitivity analysis showed that the total costs at the farm level were most sensitive for variation in the probability of occurrence of clinical mastitis and the probability of culling. This study helps farmers to raise awareness about the actual costs of mastitis and motivate them to timely

Guest Editorial Modeling and Advanced Control of Wind Turbines/Wind Farms

Energy Technology Data Exchange (ETDEWEB)

Hu, J.; Hou, Y.; Zhu, Z.; Xu, D.; Xu, D.; Muljadi, E.; Liu, F.; Iwanski, G.; Geng, H.; Erlich, I.; Wen, J.; Harnefors, L.; Fan, L.; El Moursi, M. S.; Kjaer, P. C.; Nelson, R. J.; Cardenas, R.; Feng, S.; Islam, S.; Qiao, W.; Yuan, X.

2017-09-01

The papers in this special section brings together papers focused on the recent advancements and breakthroughs in the technology of modeling and enhanced active/reactive power control of wind power conversion systems, ranging from components of wind turbines to wind farms.

Manure management practices on biogas and non-biogas pig farms in developing countries - using livestock farms in Vietnam as an example

DEFF Research Database (Denmark)

Cu, T. T. T.; Cuong, P. H.; Hang, L. T.

2012-01-01

This survey was carried out to study animal manure management on livestock farms with biogas technology (biogas farms) and without (non-biogas farms) in the areas surrounding the Vietnamese cities Hanoi and Hue. The objective of the study was to assess the contribution of biogas production...... to a better environment as well as to recognize the problems with livestock manure management on small-scale farms. On all the farms included in the study more than one manure management technology was used, i.e. composting, separation of manure, biogas production and discharge of liquid manure to recipients...... such as public sewers or ponds. On biogas farms, most of the manure collected was used for bio-digestion. The farmers used the fermented manure (digestate) as a source of nutrients for crops, but on more than 50% of the interviewed biogas farms digestate was discharged to the environment. On non-biogas farms...

Solutions to raptor-wind farm interactions

Energy Technology Data Exchange (ETDEWEB)

Madders, M.; Walker, D.G. [CRE Energy Ltd., Scottish Power, Glasgow (United Kingdom)

2000-07-01

Wind energy developments in the uplands have the potential to adversely impact upon a number of raptor species by lowering survival and reproductive rates. In many cases, wind farms are proposed in areas where raptors are already under pressure from existing land uses, notably sheep grazing and forestry. This paper summarises the approach used to assess the impact of a 30MW wind farm on a pair of golden eagles in the Kintyre peninsula, Scotland. We outline the method being used to manage habitats for the benefit of the eagles and their prey. By adopting management practices that are both wide-scale and long-term, we aim to reduce the impact to the wind farm to levels considered acceptable by the conservation agencies, and improve breeding productivity of the eagles using the wind farm. The implications of this innovative approach for future raptor--wind farm interactions are discussed. (Author)

Feasibility study on the wind farm; Wind farm no kanosei chosa

Energy Technology Data Exchange (ETDEWEB)

NONE

1997-03-01

For assessment of the possibility of the wind farm (collective wind power facility) in Japan, site conditions, business plans and various issues in development were arranged using some projects in a planning stage. The case study of a system design was also conducted for a typical site. Four sites were selected based on geographical conditions, topographic features and weather conditions. Scales of every site are as large as 1000-3000kW and 400- 750kW in wind turbine capacity. Every developer expects a subsidy, and governmental economic support is indispensable for the wind farm. In the case of Hisai city, Mie prefecture with the most favorable wind condition in Japan, the annual mean wind velocity of the site is valued at nearly 8m/s, suggesting that it is promising for the wind farm. From the planned scale of 750kWtimes4, the annual generated power and availability factor are valued at 9,800,000kWh/y and 37%, respectively. From the construction cost of 1 billion yen including a subsidy of its half, the generation cost is valued at 14.5 yen/kWh in durability of 15 years, and 12.2 yen/kWh in 20 years, and the profitability is dependent on the purchase price of a power company. 27 figs., 36 tabs.

Towards a ‘systems’ approach for guiding agricultural environmental management: a South African case study of a small-scale maize farming system

CSIR Research Space (South Africa)

Musvoto, Constansia D

2009-08-01

Full Text Available environmental management intervention points in an agricultural system, illustrated through a case study of a small-scale maize farming system in South Africa. A review of documented information on the ecological, socio-political and economic components...

Effects of stored feed cropping systems and farm size on the profitability of Maine organic dairy farm simulations.

Science.gov (United States)

Hoshide, A K; Halloran, J M; Kersbergen, R J; Griffin, T S; DeFauw, S L; LaGasse, B J; Jain, S

2011-11-01

United States organic dairy production has increased to meet the growing demand for organic milk. Despite higher prices received for milk, organic dairy farmers have come under increasing financial stress due to increases in concentrated feed prices over the past few years, which can make up one-third of variable costs. Market demand for milk has also leveled in the last year, resulting in some downward pressure on prices paid to dairy farmers. Organic dairy farmers in the Northeast United States have experimented with growing different forage and grain crops to maximize on-farm production of protein and energy to improve profitability. Three representative organic feed systems were simulated using the integrated farm system model for farms with 30, 120, and 220 milk cows. Increasing intensity of equipment use was represented by organic dairy farms growing only perennial sod (low) to those with corn-based forage systems, which purchase supplemental grain (medium) or which produce and feed soybeans (high). The relative profitability of these 3 organic feed systems was strongly dependent on dairy farm size. From results, we suggest smaller organic dairy farms can be more profitable with perennial sod-based rather than corn-based forage systems due to lower fixed costs from using only equipment associated with perennial forage harvest and storage. The largest farm size was more profitable using a corn-based system due to greater economies of scale for growing soybeans, corn grain, winter cereals, and corn silages. At an intermediate farm size of 120 cows, corn-based forage systems were more profitable if perennial sod was not harvested at optimum quality, corn was grown on better soils, or if milk yield was 10% higher. Delayed harvest decreased the protein and energy content of perennial sod crops, requiring more purchased grain to balance the ration and resulting in lower profits. Corn-based systems were less affected by lower perennial forage quality, as corn silage

Wind Farm Wake

DEFF Research Database (Denmark)

Hasager, Charlotte Bay; Karagali, Ioanna; Volker, Patrick

2017-01-01

On 25 January 2016 at 12:45 UTC several photographs of the offshore wind farm Horns Rev 2 were taken by helicopter pilot Gitte Lundorff with an iPhone. A very shallow layer of fog covered the sea. The photos of the fog over the sea dramatically pictured the offshore wind farm wake. Researchers got...... together to investigate the atmospheric conditions at the time of the photos by analysing local meteorological observations and wind turbine information, satellite remote sensing and nearby radiosonde data. Two wake models and one mesoscale model were used to model the case and explain what was seen....

Maximum Energy Yield Oriented Turbine Control in PMSG based Wind Farm

OpenAIRE

Tian, Jie; Zhou, Dao; Su, Chi; Blaabjerg, Frede; Chen, Zhe

2017-01-01

: In the modern power systems, with the fast integration of the wind power into the grid, it turns to develop large-scale offshore wind farms equipped with the permanent magnet synchronous generator (PMSG) wind turbine. In large-scale offshore wind farms, the wind turbine operating reliability and the wake effect in the wind farm became important issues. The pitch angle and tip speed ratio are the two degrees of freedom for the PMSG wind turbine active power control, which are also the determ...

Generalized coupled wake boundary layer model: applications and comparisons with field and LES data for two wind farms

NARCIS (Netherlands)

Stevens, Richard Johannes Antonius Maria; Gayme, Dennice F.; Meneveau, Charles

2016-01-01

We describe a generalization of the coupled wake boundary layer (CWBL) model for wind farms that can be used to evaluate the performance of wind farms under arbitrary wind inflow directions, whereas the original CWBL model (Stevens et al., J. Renewable and Sustainable Energy 7, 023115 (2015))

The EU's agenda 2000 reformand the sustainability of organic farming in Tuscany: ecological-econmic modelling at field and farm level

NARCIS (Netherlands)

Pacini, G.C.; Giesen, G.W.J.; Wossink, G.A.A.; Omodei-Zorini, L.; Huirne, R.B.M.

2004-01-01

Sustainability has become a central issue in the agricultural sector, both for researchers, producers and policy-makers. The two main objectives of this paper are: (1) to present an holistically designed ecological-economic model to evaluate farm and field-level environmental-economic tradeoffs with

Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

DEFF Research Database (Denmark)

Feng, Ju; Shen, Wen Zhong

2015-01-01

Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distribu...

Standardized facility record and report model system (FARMS) for material accounting and control

International Nuclear Information System (INIS)

Nishimura, Hideo; Ihara, Hitoshi; Hisamatsu, Yoshinori.

1990-07-01

A facility in which nuclear materials are handled maintains a facility system of accounting for and control of nuclear material. Such a system contains, as one of key elements, a record and report system. This record and report information system is a rather complex one because it needs to conform to various requirements from the national or international safeguards authorities and from the plant operator who has to achieve a safe and economical operation of the plant. Therefore it is mandatory to computerize such information system. The authors have reviewed these requirements and standardized the book-keeping and reporting procedures in line with their computerization. On the basis of this result the authors have developed a computer system, FARMS, named as an acronym of standardized facility record and report model system, mainly reflecting the requirements from the national and international safeguards authorities. The development of FARMS has also been carried out as a JASPAS - Japan Support Programme for Agency Safeguards - project since 1985 and the FARMS code was demonstrated as an accountancy tool in the regional SSAC training courses held in Japan in 1985 and 1987. This report describes the standardization of a record and report system at the facility level, its computerization as a model system and the demonstration of the developed system, FARMS. (author)

Classification of Specialized Farms Applying Multivariate Statistical Methods

Directory of Open Access Journals (Sweden)

Zuzana Hloušková

2017-01-01

Full Text Available Classification of specialized farms applying multivariate statistical methods The paper is aimed at application of advanced multivariate statistical methods when classifying cattle breeding farming enterprises by their economic size. Advantage of the model is its ability to use a few selected indicators compared to the complex methodology of current classification model that requires knowledge of detailed structure of the herd turnover and structure of cultivated crops. Output of the paper is intended to be applied within farm structure research focused on future development of Czech agriculture. As data source, the farming enterprises database for 2014 has been used, from the FADN CZ system. The predictive model proposed exploits knowledge of actual size classes of the farms tested. Outcomes of the linear discriminatory analysis multifactor classification method have supported the chance of filing farming enterprises in the group of Small farms (98 % filed correctly, and the Large and Very Large enterprises (100 % filed correctly. The Medium Size farms have been correctly filed at 58.11 % only. Partial shortages of the process presented have been found when discriminating Medium and Small farms.

Validation of farm-scale methane emissions using nocturnal boundary layer budgets

Directory of Open Access Journals (Sweden)

J. Stieger

2015-12-01

Full Text Available This study provides the first experimental validation of Swiss agricultural methane emission estimates at the farm scale. We measured CH4 concentrations at a Swiss farmstead during two intensive field campaigns in August 2011 and July 2012 to (1 quantify the source strength of livestock methane emissions using a tethered balloon system and (2 to validate inventory emission estimates via nocturnal boundary layer (NBL budgets. Field measurements were performed at a distance of 150 m from the nearest farm buildings with a tethered balloon system in combination with gradient measurements at eight heights on a 10 m tower to better resolve the near-surface concentrations. Vertical profiles of air temperature, relative humidity, CH4 concentration, wind speed, and wind direction showed that the NBL was strongly influenced by local transport processes and by the valley wind system. Methane concentrations showed a pronounced time course, with highest concentrations in the second half of the night. NBL budget flux estimates were obtained via a time–space kriging approach. Main uncertainties of NBL budget flux estimates were associated with nonstationary atmospheric conditions and the estimate of the inversion height zi (top of volume integration. The mean NBL budget fluxes of 1.60 ± 0.31 μg CH4 m-2 s-1 (1.40 ± 0.50 and 1.66 ± 0.20 μg CH4 m-2 s-1 in 2011 and 2012 respectively were in good agreement with local inventory estimates based on current livestock number and default emission factors, with 1.29 ± 0.47 and 1.74 ± 0.63 μg CH4 m-2 s-1 for 2011 and 2012 respectively. This indicates that emission factors used for the national inventory reports are adequate, and we conclude that the NBL budget approach is a useful tool to validate emission inventory estimates.

Validation of farm-scale methane emissions using nocturnal boundary layer budgets

Science.gov (United States)

Stieger, J.; Bamberger, I.; Buchmann, N.; Eugster, W.

2015-12-01

This study provides the first experimental validation of Swiss agricultural methane emission estimates at the farm scale. We measured CH4 concentrations at a Swiss farmstead during two intensive field campaigns in August 2011 and July 2012 to (1) quantify the source strength of livestock methane emissions using a tethered balloon system and (2) to validate inventory emission estimates via nocturnal boundary layer (NBL) budgets. Field measurements were performed at a distance of 150 m from the nearest farm buildings with a tethered balloon system in combination with gradient measurements at eight heights on a 10 m tower to better resolve the near-surface concentrations. Vertical profiles of air temperature, relative humidity, CH4 concentration, wind speed, and wind direction showed that the NBL was strongly influenced by local transport processes and by the valley wind system. Methane concentrations showed a pronounced time course, with highest concentrations in the second half of the night. NBL budget flux estimates were obtained via a time-space kriging approach. Main uncertainties of NBL budget flux estimates were associated with nonstationary atmospheric conditions and the estimate of the inversion height zi (top of volume integration). The mean NBL budget fluxes of 1.60 ± 0.31 μg CH4 m-2 s-1 (1.40 ± 0.50 and 1.66 ± 0.20 μg CH4 m-2 s-1 in 2011 and 2012 respectively) were in good agreement with local inventory estimates based on current livestock number and default emission factors, with 1.29 ± 0.47 and 1.74 ± 0.63 μg CH4 m-2 s-1 for 2011 and 2012 respectively. This indicates that emission factors used for the national inventory reports are adequate, and we conclude that the NBL budget approach is a useful tool to validate emission inventory estimates.

Wind farms impact on radar aviation interests - final report

Energy Technology Data Exchange (ETDEWEB)

Poupart, G.J.

2003-09-01

The main objectives of the study were: to determine the effects of siting wind turbines adjacent to primary air traffic control radar; to gather the information required for the generation of guidelines by civil, military and wind farm developer stakeholders; to determine the extent to which the design of wind turbines influences their effects on radar systems and to determine the extent to which design of the radar processing influences the effects of wind turbines on radar systems. A computer model was developed to predict the Radar Cross Section (RCS) of wind turbines and understand the interaction of radar energy and turbines. The model was designed to predict and simulate the impact of wind farms on the primary radar display. Validation of the model was carried out in a full-scale trial and modelling process, with data collected from a number of sources. The model was validated against a single turbine scenario and showed an accurate prediction capability. Further validation of the model could be gained through a multiple turbine trial. The knowledge gained from the development and validation of the predictive computer model has been used to conduct a sensitivity analysis (of the sub-elements of the radar and wind farm interaction) and to compile a list of the key factors influencing the radar signature of wind turbines. The result is a more detailed quantification of the complex interactions between wind turbines and radar systems than was previously available. The key findings of how the design, size and construction materials of wind turbines affect RCS are summarised.

Economics of small-scale on-farm use of canola and soybean for biodiesel and straight vegetable oil biofuels

International Nuclear Information System (INIS)

Fore, Seth R.; Porter, Paul; Jordan, Nicholas; Lazarus, William

2011-01-01

While the cost competitiveness of vegetable oil-based biofuels (VOBB) has impeded extensive commercialization on a large-scale, the economic viability of small-scale on-farm production of VOBB is unclear. This study assessed the cost competitiveness of small-scale on-farm production of canola- [Brassica napus (L.)] and soybean-based [Glycine max (L.)] biodiesel and straight vegetable oil (SVO) biofuels in the upper Midwest at 2007 price levels. The effects of feedstock type, feedstock valuation (cost of production or market price), biofuel type, and capitalization level on the cost L -1 of biofuel were examined. Valuing feedstock at the cost of production, the cost of canola-based biodiesel ranged from 0.94 to 1.13 L -1 and SVO from 0.64 to 0.83 L -1 depending on capitalization level. Comparatively, the cost of soybean-based biodiesel and SVO ranged from 0.40 to 0.60 L -1 and from 0.14 to 0.33 L -1 , respectively, depending on capitalization level. Valuing feedstock at the cost of production, soybean biofuels were cost competitive whereas canola biofuels were not. Valuing feedstock at its market price, canola biofuels were more cost competitive than soybean-based biofuels, though neither were cost competitive with petroleum diesel. Feedstock type proved important in terms of the meal co-product credit, which decreased the cost of biodiesel by 1.39 L -1 for soybean and 0.44 L -1 for canola. SVO was less costly to produce than biodiesel due to reduced input costs. At a small scale, capital expenditures have a substantial impact on the cost of biofuel, ranging from 0.03 to 0.25 L -1 . (author)

Contribution of fish farming to the nutrient loading of the Mediterranean

Directory of Open Access Journals (Sweden)

Ioannis Karakassis

2005-06-01

Full Text Available Mediterranean fish farming has grown exponentially during the last 20 years. Although there is little evidence of the impact on the trophy status around fish farms, there are concerns that the release of solute wastes from aquaculture might affect larger scales in the ecosystem by changing the nutrient load. After combining information from various sources on waste production and on nutrient loads, it was concluded that the overall N and P waste from fish farms in the Mediterranean represents less than 5% of the total annual anthropogenic discharge, and the overall annual increase in P and N pools in the Mediterranean, under a production rate of 150000 tons, is less than 0.01%. The proportion of fish farming discharged nutrients was slightly higher in the eastern Mediterranean. A simple model was used to assess the long-term effects of nutrients released from various sources taking into account the water renewal rate in the Mediterranean. We conclude that, in the long term, fish farm waste could cause a 1% increase in nutrient concentrations in contrast to other anthropogenic activities which might double the Mediterranean nutrient pool.

A review of Agent Based Modeling for agricultural policy evaluation

NARCIS (Netherlands)

Kremmydas, Dimitris; Athanasiadis, I.N.; Rozakis, Stelios

2018-01-01

Farm level scale policy analysis is receiving increased attention due to a changing agricultural policy orientation. Agent based models (ABM) are farm level models that have appeared in the end of 1990's, having several differences from traditional farm level models, like the consideration of

Control of Groundwater Pollution from Animal Feeding Operations: A Farm-Level Dynamic Model for Policy Analysis

Science.gov (United States)

Wang, J.; Baerenklau, K.

2012-12-01

Consolidation in livestock production generates higher farm incomes due to economies of scale, but it also brings waste disposal problems. Over-application of animal waste on adjacent land produces adverse environmental and health effects, including groundwater nitrate pollution. The situation is particularly noticeable in California. In respond to this increasingly severe problem, EPA published a type of command-and-control regulation for concentrated animal feeding operations (CAFOs) in 2003. The key component of the regulation is its nutrient management plans (NMPs), which intend to limit the land application rates of animal waste. Although previous studies provide a full perspective on potential economic impacts for CAFOs to meet nutrient standards, their models are static and fail to reflect changes in management practices other than spreading manure on additional land and changing cropping patterns. We develop a dynamic environmental-economic modeling framework for representative CAFOs. The framework incorporates four models (i.e., animal model, crop model, hydrologic model, and economic model) that include various components such as herd management, manure handling system, crop rotation, water sources, irrigation system, waste disposal options, and pollutant emissions. We also include the dynamics of soil characteristics in the rootzone as well as the spatial heterogeneity of the irrigation system. The operator maximizes discounted total farm profit over multiple periods subject to environmental regulations. Decision rules from the dynamic optimization problem demonstrate best management practices for CAFOs to improve their economic and environmental performance. Results from policy simulations suggest that direct quantity restrictions of emission or incentive-based emission policies are much more cost-effective than the standard approach of limiting the amount of animal waste that may be applied to fields (as shown in the figure below); reason being

Estimation of NH3 emissions from a naturally ventilated livestock farm using local-scale atmospheric dispersion modelling

Czech Academy of Sciences Publication Activity Database

Hensen, A.; Loubet, B.; Mosquera, J.; van den Bulk, W. C. M.; Erisman, J. W.; Daemmgen, U.; Milford, C.; Loepmeier, F. J.; Cellier, P.; Mikuška, Pavel; Sutton, M. A.

2009-01-01

Roč. 6, č. 12 (2009), s. 2847-2860 ISSN 1726-4170 Institutional research plan: CEZ:AV0Z40310501 Keywords : NH3 livestock farm emissions * concentration measurement * atmospheric dispersion Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.246, year: 2009 http://www.biogeosciences.net/6/2847/2009/

Shellfish Aquaculture from Space: Potential of Sentinel2 to Monitor Tide-Driven Changes in Turbidity, Chlorophyll Concentration and Oyster Physiological Response at the Scale of an Oyster Farm

Directory of Open Access Journals (Sweden)

Pierre Gernez

2017-05-01

Full Text Available The algorithms of Novoa et al. (2017 and Gons et al. (2005 were recalibrated and applied to Sentinel2 data to retrieve suspended particulate matter (SPM and chlorophyll a (chl a concentration in the environmentally and economically important intertidal zones. Sentinel2-derived chl a and SPM concentration distributions were analyzed at the scale of an oyster farm over a variety of tidal conditions. Sentinel2 imagery was then coupled with ecophysiological modeling to analyze the influence of tide-driven chl a and SPM dynamics on oyster clearance and chl consumption rates. Within the studied oyster farming site (Bourgneuf Bay along the French Atlantic coast, chl consumption rate mirrored the changes in chl a concentration during neap tides, whereas oyster clearance and chl consumption rates were both negatively impacted by high SPM concentration during spring tides.

Centralized configuration system for a large scale farm of network booted computers

Science.gov (United States)

Ballestrero, S.; Brasolin, F.; Dârlea, G.-L.; Dumitru, I.; Scannicchio, D. A.; Twomey, M. S.; Vâlsan, M. L.; Zaytsev, A.

2012-12-01

The ATLAS trigger and data acquisition online farm is composed of nearly 3,000 computing nodes, with various configurations, functions and requirements. Maintaining such a cluster is a big challenge from the computer administration point of view, thus various tools have been adopted by the System Administration team to help manage the farm efficiently. In particular, a custom central configuration system, ConfDBv2, was developed for the overall farm management. The majority of the systems are network booted, and are running an operating system image provided by a Local File Server (LFS) via the local area network (LAN). This method guarantees the uniformity of the system and allows, in case of issues, very fast recovery of the local disks which could be used as scratch area. It also provides greater flexibility as the nodes can be reconfigured and restarted with a different operating system in a very timely manner. A user-friendly web interface offers a quick overview of the current farm configuration and status, allowing changes to be applied on selected subsets or on the whole farm in an efficient and consistent manner. Also, various actions that would otherwise be time consuming and error prone can be quickly and safely executed. We describe the design, functionality and performance of this system and its web-based interface, including its integration with other CERN and ATLAS databases and with the monitoring infrastructure.

A Simulation Model of Combined Biogas, Bioethanol and Protein Fodder Co-Production in Organic Farming

DEFF Research Database (Denmark)

Oleskowicz-Popiel, Piotr; Thomsen, Mette Hedegaard; Thomsen, Anne Belinda

2009-01-01

In order to evaluate new strategies for the production of renewable energy within sustainable organic agriculture, a process-simulation model for a 100 ha organic farm was developed. Data used for the model was obtained from laboratory trials, literature data, consultancy with experts, and results...... ha organic farm with ethanol or biogas, respectively. This calculation was based on the assumption that the electrical efficiency of CHP (combined heat and power) unit was 38%. A variety of different scenarios can be simulated to mirror the farmer's needs....

Power fluctuations from large wind farms - Final report

Energy Technology Data Exchange (ETDEWEB)

Soerensen, Poul; Pinson, P.; Cutululis, N.A.; Madsen, Henrik; Jensen, Leo Enrico; Hjerrild, J.; Heyman Donovan, M.; Vigueras-ROdriguez, A.

2009-08-15

Experience from power system operation with the first large offshore wind farm in Denmark: Horns Rev shows that the power from the wind farm is fluctuating significantly at certain times, and that this fluctuation is seen directly on the power exchange between Denmark and Germany. This report describes different models for simulation and prediction of wind power fluctuations from large wind farms, and data acquired at the two large offshore wind farms in Denmark are applied to validate the models. Finally, the simulation model is further developed to enable simulations of power fluctuations from several wind farms simultaneously in a larger geographical area, corresponding to a power system control area. (au)

Analysis of High Frequency Resonance in DFIG-based Offshore Wind Farm via Long Transmission Cable

DEFF Research Database (Denmark)

Song, Yipeng; Ebrahimzadeh, Esmaeil; Blaabjerg, Frede

2018-01-01

During the past two decades, the Doubly Fed Induction Generator (DFIG) based wind farm has been under rapid growth, and the increasing wind power penetration has been seen. Practically, these wind farms are connected to the three-phase AC grid through long transmission cable which can be modelled...... as several II units. The impedance of this cable cannot be neglected and requires careful investigation due to its long distance. As a result, the impedance interaction between the DFIG based wind farm and the long cable is inevitable, and may produce High Frequency Resonance (HFR) in the wind farm....... This paper discusses the HFR of the large scale DFIG based wind farm connected to the long cable. Several influencing factors, including 1) the length of the cable, 2) the output active power and 3) the rotor speed, are investigated. Simulation validations using MATLAB / Simulink have been conducted...

Benefit-Cost Analysis of Foot-and-Mouth Disease Vaccination at the Farm-Level in South Vietnam.

Science.gov (United States)

Truong, Dinh Bao; Goutard, Flavie Luce; Bertagnoli, Stéphane; Delabouglise, Alexis; Grosbois, Vladimir; Peyre, Marisa

2018-01-01

This study aimed to analyze the financial impact of foot-and-mouth disease (FMD) outbreaks in cattle at the farm-level and the benefit-cost ratio (BCR) of biannual vaccination strategy to prevent and eradicate FMD for cattle in South Vietnam. Production data were collected from 49 small-scale dairy farms, 15 large-scale dairy farms, and 249 beef farms of Long An and Tay Ninh province using a questionaire. Financial data of FMD impacts were collected using participatory tools in 37 villages of Long An province. The net present value, i.e., the difference between the benefits (additional revenue and saved costs) and costs (additional costs and revenue foregone), of FMD vaccination in large-scale dairy farms was 2.8 times higher than in small-scale dairy farms and 20 times higher than in beef farms. The BCR of FMD vaccination over 1 year in large-scale dairy farms, small-scale dairy farms, and beef farms were 11.6 [95% confidence interval (95% CI) 6.42-16.45], 9.93 (95% CI 3.45-16.47), and 3.02 (95% CI 0.76-7.19), respectively. The sensitivity analysis showed that varying the vaccination cost had more effect on the BCR of cattle vaccination than varying the market price. This benefit-cost analysis of biannual vaccination strategy showed that investment in FMD prevention can be financially profitable, and therefore sustainable, for dairy farmers. For beef cattle, it is less certain that vaccination is profitable. Additional benefit-cost analysis study of vaccination strategies at the national-level would be required to evaluate and adapt the national strategy to achieve eradication of this disease in Vietnam.

Sustainable extensification as an alternative model for reducing GHG emissions from agriculture. The case of an extensively managed organic farm in Denmark