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United States Department of Agriculture

Agricultural Research Service

Research Project: PRODUCTION OF QUALITY POWER AND/OR HEAT FOR ON-FARM OPERATIONS
2012 Annual Report


1a.Objectives (from AD-416):
The long-term objective of this project is to develop the technology and demonstrate the equipment needed to provide heat and power for stationary on-farm energy uses. Modern agricultural activities require large amounts of heat and power to achieve the production efficiencies required to meet the demands for food, feed, fiber, and energy. Cities, industries, and service organizations require more and more of the energy produced by large central generating plants; therefore, farmers and ranchers have to seek ways to produce their own energy. Traditionally, farmers and ranchers have produced their own energy by burning wood and crop residues. They also used water, wind, and animal energy to provide the needed power. During the last 80 years, farmers have used alternative fuels derived from petroleum and coal. Now that petroleum-based energy is in limited supply and expensive, producers must return to the basic, natural, renewable energy sources. The project will focus on the following three objectives: Objective 1: Develop (1) hybrid biodiesel/wind/solar- and (2) hybrid wind/solar-based technologies that enable commercial on-farm production of heat and power. Subobjective 1A: Use hybrid wind/solar energy systems to pump water for irrigation in the Southern High Plains; Subobjective 1B: Develop industrial control algorithms that allow for the safe and efficient integration of biodiesel/wind/solar hybrid systems into agricultural operations for the production of heat and power; Subobjective 1C: Use heat from sun to either heat or preheat water for dairies in the Southern High Plains. Objective 2: Develop hybrid wind/solar-based technologies that enable commercial on-farm production of hydrogen. Objective 3: Develop microbial-based technologies that enable commercial on-farm production of fuels, power, and/or bioproducts from manures. Subobjective 3A: Identify microorganisms that are electricigens or microbial consortia that can act as electricigens that are derived from either beef or dairy concentrated animal feeding operations (CAFO); Subobjective 3B: Determine the potential power output of identified electricigens-microbial consortia in low- (H-cell type) and high-power (ministack-type) fuel cell configurations using various types and forms of 'manure fuels;' Subobjective 3C: Evaluate microbial consortia-bioreactor designs for the efficient generation of H from manure wastes.


1b.Approach (from AD-416):
This project will involve research experiments designed to develop new products that will allow farmers and ranchers to produce affordable, renewable, reliable energy from wind, solar, and biomass resources. The research team has a long history in designing remote power systems for pumping water and providing electricity to remote sites and villages. This activity will continue by the development of hybrid systems using both wind and solar energy with storage capability to provide continuous power or heat. Efforts will be expanded by including research that will examine the feasibility of producing either hydrogen or electricity using a microbial fuel cell in manure-laden waste water retention ponds.


3.Progress Report:
Field testing began on off-grid hybrid renewable energy systems at USDA-ARS-CPRL, Bushland, TX. These systems were composed of a wind turbine rated at 900 Watts and three different solar photovoltaic (PV) arrays with power ratings of 320, 480, and 640 Watts. At times, the wind turbine and solar PV arrays interfered with each other, probably because differences in the voltage between the two systems (the voltage of the wind turbine varies with wind speed; whereas, the PV arrays operate at a near-constant voltage). A controller that modifies the voltage of the wind turbine, so it can be matched to the solar PV array, was developed during the summer of 2012. A 2.4-kW, motorized tracking, on-grid solar PV system was installed at USDA-ARS-CPRL, Bushland,TX. Power data on this solar-PV system was compared with that from a 2.4-kW on-grid wind turbine. To date, the actual power output for both the wind and solar on-grid systems has compared favorably with theoretically predicted values. PV module temperature and irradiance incident were collected on:.
1)a solar-PV 2-dimensional motorized tracking system,.
2)a solar-PV 1-dimensional passive tracking system, and.
3)a solar-PV fixed system. The temperature of the different PV arrays varied between 110 and 150 degrees Fahrenheit,which indicated that designing a cooling system using 60 degree Fahrenheit irrigation water could potentially improve the performance of the PV arrays. We installed and instrumented an unglazed solar thermal hot water system in order to investigate the use of solar thermal energy to assist in the heating of water for dairies or cattle feeding operations. The system consisted of seven 4'x 12' solar collectors (336 ft**2), a modified PV module uni-strut rack (with adjustable incidence angle) for holding solar thermal collectors, a black 550-gallon water tank, a 0.5-hp pump for circulating water through the collectors, and a motor controller for varying time-of-day operation of pump motor. Data being collected are: atmospheric air temperature, inlet solar collector water temperature, outlet solar collector water temperature, solar collector temperature, water flow rate, and wind speed/direction upwind of solar collectors (e.g., needed for estimating heat transfer of solar collectors to air). To determine how well hybrid wind/solar off-grid and on-grid water pumping systems can meet irrigation well electrical loading and how well solar thermal hot water systems can meet the hot water requirements of dairies and feedyards, electrical loading data must also be measured. We began measuring the energy required to heat the water and the amount of hot water used at a feedyard (e.g., steam flaking of corn) and at a dairy. Discussions began with Texas A&M-AgriLife scientists concerning measuring electrical use on irrigation wells. Active Aero Load Control (AALC) devices have the potential to improve the efficiency of wind turbine blades. Motor-driven trailing-edge ailerons were installed on wind turbine blades to modify the aerodynamic loading of the blades and to improve dynamic blade load balancing. The test was completed and the data submitted to the Sandia wind energy group.


4.Accomplishments
1. Calculating direct normal irradiance can help evaluate whether to use solar energy systems. Solar direct normal irradiance (DNI) hourly data (measured or calculated) are required to predict the performance of concentrating solar power (CSP) systems, such as the parabolic trough CSP plants located in the Mojave Desert of California. However, the instrumentation to measure DNI is expensive, and the equipment requires daily inspection by knowledgeable personnel. An ARS scientist at the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas, collaborating with scientists at the Sandia National Laboratories, Albuquerque, New Mexico, and the National Renewable Energy Laboratory, Golden, Colorado, compared measured DNI data to that calculated by three different DNI models (DISC, DIRINT, and DIRINDEX). The DNI values calculated with the DIRINT model had sufficient accuracy to evaluate CSP systems in the Texas Panhandle. These results suggest that Texas Panhandle electrical utility planners can investigate the feasibility of constructing parabolic trough CSP plants using the DIRINT model. Installation of CSP plants, or other CSP systems (e.g., like commercial CSP hot water systems), would increase the percentage of renewable energy on the utility’' system and decrease air pollution from coal-powered plants.

2. Wind and sun join forces to pump water for livestock. On the Great Plains, wind-powered water pumping systems do not match the livestock water requirement because wind energy is usually least in July and August, when animal water requirements are greatest. A USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas, scientist field tested the capacity of wind, solar, and hybrid wind/solar water pumping systems to pump water for livestock. A single electrical helical pump (e.g., a screw-type pump) powered with electricity generated by a combination of wind and solar energy pumped more water in August than if the wind and solar systems pumped water separately on two individual helical pumps. The hybrid wind/solar energy water pumping system was also more reliable than either wind or solar energy alone, because if one system failed the other was able to continue to pump water. Also, excess wind-generated electricity in the winter can be used to power stock tank heaters. These results may be used by industry to develop improved livestock water pumping systems.

3. New acoustic analysis helps engineers design quieter wind turbines. Small wind turbines can produce a high sound emission if the blades flutter or the blade rotor speed is too high. A USDA-ARS-Conservation and Production Research Laboratory, Bushland, Texas, scientist collected acoustic data on two wind turbines, each with three different blade designs. Acoustic analysis was performed using a program developed by the ARS scientist. Blade flutter was detected by an abrupt increase in sound level with a small change in rotor speed and the analysis was able to identify blades designs and rotor speeds that minimize sound emissions. The acoustic analysis developed by the CPRL scientist will help engineers determine if their blade modifications are reducing the sound level of the wind turbine. Lower sound emission from wind turbines should increase the sale of wind turbines, especially in locations with ordinances requiring low noise levels.

4. Cooling solar photovoltaic arrays increases power. The electric power produced by solar photovoltaic (PV) arrays is reduced as the module temperature of the solar PV increases. A USDA-ARS-Conservation and Production Research Laboratory, Bushland, Texas, scientist collected data on a two-dimensional tracking 2.4-kW PV array. Results indicate that electrical power generation could potentially be increased by 20% by using pumped irrigation water to cool the solar PV array. Depending on the cost of the PV array cooling system, a 20% increase in performance could yield a cost-effective hybrid wind/solar powered irrigation system in the Southern Great Plains.

5. Solar-powered water systems for dairies save gas. Dairies use large amounts of hot water for washing milking machines, and a significant percentage of total dairy expense is for natural gas used in heating water. A USDA-ARS-Conservation and Production Research Laboratory, Bushland, Texas, scientist supervised the installation and instrumentation of an unglazed solar hot water system to determine if it could totally or partially replace the natural gas currently being used on the Southern High Plains dairies. It was found that a 336-square foot unglazed solar collector could heat water in a 550-gallon tank from 70 deg F to at least 120 deg F in July. Use of solar energy instead of natural gas for heating water at dairies will decrease atmospheric pollution, lower energy costs and increase profits.

6. Ailerons should increase longevity of wind turbine blades on the Southern High Plains. High wind shear at night in the Great Plains results in high blade loading for blades rotating above the wind turbine generator and low blade loading for blades rotating below the wind generator. Scientists at the USDA-ARS-CPRL, Bushland, Texas, in collaboration with scientists from Sandia National Laboratories, installed and instrumented motor-driven trailing-edge ailerons on wind turbine blades to modify the aerodynamic loading of the blades and to improve the balance of blade loading. Computer analysis indicated that use of ailerons on wind turbine blades could decrease the total wind turbine cost 5 to 8% by modifying the blade loading. The use of these ailerons has the potential to decrease stress on wind turbine blades, thus increasing the life time and decreasing the maintenance of wind turbines.


Review Publications
Vick, B.D., Neal, B. 2012. Analysis of off grid hybrid wind turbine/solar PV water pumping systems. Solar Energy. 86(5):1197-1207.

Last Modified: 11/28/2014
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