Location: Livestock Nutrient Management Research2013 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:
At the request of ONP this project was redirected to an emphasis on bioenergy in May 2013. Of the 3 project objectives, the first was mostly achieved; whereas, the other two could not be achieved due to critical vacancies and budget. The main areas that we have worked on over the past 3.75 years were: 1) developing hybrid wind/solar on-grid and off-grid water pumping systems for farms, 2) developing solar hot water systems for feedlots and dairies, and 3) use of micro-organisms from cattle manure to produce electricity and/or hydrogen. A study was conducted to evaluate use of wind turbines and solar photovoltaic (PV) arrays connected to the utility grid for providing energy for crop irrigation systems in the Southern High Plains. It was found that combining a winter crop with a summer crop improved the match of wind energy available to irrigation energy required, but it was necessary to add a solar PV array to get a good match. However, despite the large drop in solar PV module prices over the past 5 years, the wind-turbine-only system had the greatest return on investment. Research on off-grid hybrid wind/solar systems began in 2011. In this hybrid system the wind turbine and solar PV array frequently interfered with each other due to differences in voltage (wind turbine voltage varies with wind speed; whereas, the PV array operates at a near constant voltage). It was found that the wind turbine and PV array would not interfere with each other if a battery bank was used as an energy buffer. When no irrigation was necessary, the wind/solar/battery system could be used to power other electrical loads on the farm. We investigated the use of low-cost solar thermal systems in the heating of water for dairies and feedlots. Two similar unglazed solar thermal hot water systems were constructed. Performance was evaluated by changing one variable on one and not the other. It was determined that connecting the collectors in series resulted in a higher water temperature, but connecting in parallel would heat a larger volume of water. Depending on the amount and temperature of hot water needed, a solar hot water system could be designed. It was also determined the pumps should be powered by a solar PV array since pumping should only occur when the sun is shining. To determine how well a wind turbine/solar PV system will work for irrigation pumping and how well a solar hot water system will work for dairies and feedlots, information on energy usage, water flow rate, and water temperature are required. Previous work by others allowed the electricity usage and water flow rate to be estimated for irrigation. Data were collected at a feedlot for one year, but no data were collected on dairies due to insufficient personnel. To evaluate electricity or hydrogen production from manure, microbial fuel cell designs were used to isolate bacteria from feedlot samples. Hydrogen-producing bacteria were isolated and 70 strains were genetically characterized and evaluated for hydrogen production. Genetic characterizations were determined for 300 electricity-producing bacterial communities. Techniques were developed to select the best ones for producing electricity.
1. Off-grid wind/solar/battery powered water pumping. In many locations in the world (including the U.S.), water pumping systems do not have access to electricity generated by a power plant and are usually dependent on diesel-powered generators. Diesel generators use fuel that is expensive, require high maintenance, emit greenhouse gases, and also cause pollution due to fuel spills. USDA-ARS researched the use of off-grid hybrid wind/solar powered systems for on-farm use, but none of these systems are sold currently for water pumping due partly to interference of combining wind turbine with a solar photovoltaic (PV) array. An ARS scientist, in collaboration with a small wind turbine manufacturer, developed and field tested a hybrid wind/solar/battery system that allows the wind turbine to be combined with a solar PV system for pumping water using a commercial solar pump. The hybrid wind/solar/battery water pumping system was more reliable than either the wind turbine or the solar PV array alone because if the wind or solar system failed, the other system could continue to pump water. Also, when no water pumping is necessary or more renewable energy is generated than needed, the electricity can be used for other on-farm electrical loads. Therefore, adding a battery bank with an appropriately designed wind turbine controller could result in a power system that is less expensive, less polluting, and lower maintenance than a diesel generator.
2. Combining solar power plants with wind farms. Texas generates the largest amount of wind generated electricity in the U.S. (7.4% of total electricity used in Texas in 2012 was generated from wind turbines), but as the percentage increases above 10%, it will become increasingly difficult for utilities to balance the electrical load because peak wind power generation occurs around midnight when the electrical load tends to be low. An ARS scientist at Bushland, Texas, collaborated with a scientist at the Sandia National Laboratory (Albuquerque, New Mexico) to determine if combining a concentrating solar power (CSP) plant with wind farms would improve the match to the utility electrical load in the Texas Panhandle. For the Texas Panhandle, the CSP plant power rating should be half that of the wind farm to match the annual utility electrical loading. The CSP plant with 6 hours of solar thermal storage also performed very well for peak utility loading days (a major criteria for power plant selection by a utility). Although the levelized cost of energy was higher (approximately $0.04/kWh) for the combination wind farm and CSP plant compared to the wind farm only, the improvement in matching the utility electrical load and increased reliability may be worth the cost. Installation of hybrid wind farm/solar power plants could increase the percentage of renewable energy on the utility's system which will help utilities transition from fossil-fuel-powered plants that produce greenhouse gases, and have a finite fuel source.
3. Effect of wind speed on solar energy performance. A common variable overlooked in the placement of either a solar photovoltaic (PV) system or an unglazed solar thermal hot water system is the wind speed. An increase in wind speed improves the performance of a PV array because they operate more efficiently at cooler temperatures, but degrades the performance of an unglazed solar thermal collector. An ARS scientist at Bushland, Texas, measured air temperature, wind speed, solar PV module temperature, solar collector temperature, water temperature, solar irradiance, and AC power generated by a PV array to determine the effect of wind speed on a solar PV system. For days of similar irradiance and air temperature, an increase in wind speed of 5 m/s resulted in a 3 to 5% increase in electricity produced. In contrast, a 5 m/s increase in wind speed (again for days with similar irradiance and air temperature) resulted in a 50% decrease in the temperature of hot water produced using a unglazed solar thermal collector. This information should help in the design and placement of solar PV arrays and unglazed solar thermal hot water collectors.
Vick, B.D., Myers, D., Boyson, W. 2012. Using direct normal irradiance models and utility electrical loading to assess benefit of a concentrating solar power plant. Solar Energy. 86:3519-3530.