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United States Department of Agriculture

Agricultural Research Service

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Location: Renewable Energy and Manure Management Research

2011 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
Data were collected on hybrid renewable energy off-grid water pumping systems. The hybrid renewable energy 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 (e.g., used 160-Watt multi-crystalline modules that converted approximately 12% of solar energy to usable power). The 640-Watt solar PV array was determined to be the most efficient array to use with the 900-Watt wind turbine. In the future, we will modify the controller to determine whether adjusting the voltage output of the wind turbine will affect the hybrid wind turbine and solar PV array performance. We are planning to collect data for a grid-tied hybrid wind-solar powered irrigation system. A solar-PV motorized tracking on-grid system was purchased and installed at the laboratory. We purchased a solar pool heating system that will be installed in the fall of 2011. With this, we will investigate using the solar energy alone to heat water for dairies or animal feeding operations. This heating data will be used to determine if using a solar pool heating system can be recommended for heating water for cleaning milk equipment, cow udders, etc. at a dairy, or preheating water for steam-flaking of corn at a beef cattle feedlot. Another option for heating water is to use a parabolic trough solar collector to concentrate the energy. We have constructed a parabolic trough that ranged in efficiency from 56 to 75% for making biodiesel. This parabolic trough can also be used for heating water. In 2012, we plan to install a tracking system for the parabolic trough. A feedlot and a dairy have been identified for monitoring the electrical and heat loads of several animal feeding operations. Data loggers, power transducers, anemometers, pyranometers, and some water flow measuring equipment for these studies have been purchased. Another possible method of electricity production at feedlots is to use animal manure as a biofuel feedstock for the production of electricity for onsite usage. Manure from beef cattle animal feeding operations were evaluated for the potential to produce two forms of energy: electricity via the use of various types of microbial fuel cells (MFC) and the generation of bio-hydrogen from microorganisms belonging to anoxygenic pigmented bacteria. We were able to recover microbial consortia capable of generating low levels of power in a sediment microbial fuel cell (sMFC), whereas a single cell MFC generated several fold more power in a much shorter period of time. Use of a single MFC design will also allow for batch and continuous methods of operations, thus facilitating the cleanup and recovery of agricultural waste water. We were able to recover nearly 600 strains potentially capable of making hydrogen. The majority of the isolates were Rhodobacter capsulatus (approximately 75%), followed by Rhodopseudomonas palustris (approximately 15%), with the rest being Rubrivivax gelatinosus or closely related strains like Rhodocyclus. These three genera are capable of generating hydrogen gas by two different mechanisms.

1. Developing a method for analyzing hybrid wind/solar energy systems. Electrical output from wind turbines and solar arrays are analyzed using different independent variables; therefore, a uniform system is needed to analyze water pumping potential of wind only, solar only, and hybrid wind–solar powered water pumping systems. An ARS research engineer at the Conservation and Production Research Laboratory, Bushland, TX, determined that the power output of a hybrid wind-solar system can be analyzed using an independent variable that is in the same fundamental units used to analyze solar energy (e.g., W/m2). The independent variable used to analyze the wind systems is wind power density, which is calculated using an equation that uses the measurable values of wind speed, air temperature, and barometric pressure. Wind power density is in the same units as solar irradiance, so that the water pumping rate, daily water volume, and power production of solar, wind, and hybrid solar-wind systems can be compared. This procedure will allow other researchers to estimate and compare the potential power output of hybrid wind-solar systems.

2. Improving small wind turbines to decrease the cost of energy for farms. An ARS research engineer at the Conservation and Production Research Laboratory, Bushland, TX, worked with small wind turbine manufacturers to increase the performance of their small wind turbine systems. Improvements in blades, generators, and inverters were implemented for a 10-kilowatt (kW) wind turbine. The changes to the wind turbine system resulted in an increase in peak power of 66%, and an approximate doubling of annual energy production (e.g., 11,100 kilowatt hours compared to 22,000 kilowatt hours) at an average wind speed of 13.4 miles per hour. Reliable, high-performing small wind turbines will potentially help farmers reduce production costs by allowing the farm to produce its own energy, conserve natural resources, and reduce reliance on foreign energy sources.

3. Sediment microbial fuel cell evaluations. Sediment microbial fuel cells (sMFC) have the potential to produce energy from manure, thus allowing manure to be used as a fuel feedstock in addition to traditional uses such as a fertilizer. An ARS scientist at the Conservation and Production Research Laboratory, Bushland, TX, conducted two separate sMFC experiments using feedlot retention pond sediment and waters as the source material for microbial communities with the potential to produce electricity. In both experiments, there was a gradual increase in power production (two to four months duration) during the course of the experiment. The low power outputs of these sMFC suggest that this method may be useful for obtaining long-term power generating microbes from the manure waste-stream; however, large amounts of power generation will require different MFC designs.

4. Recovery and storage of microbes from sediment microbial fuel cell experiments. Microbial fuel cells (MFC) is a potential technology that can be used to produce electricity from agricultural byproducts using microbes; however, the best laboratory methods to recover, store, and preserve microbial strains and consortia of microbial strains in MFC have not been determined. An ARS researcher at the Conservation and Production Research Laboratory, Bushland, TX, used several different growth media types and different laboratory selection protocols to isolate and recover microbes from electrodes in sediment microbial fuel cells (sMFC). In general, when a more nutritious growth media was used, a less diverse microbial population (i.e., fewer species) was recovered, suggesting that a few subpopulations of rapidly growing bacteria were able to out-compete other members of the bacterial community. Recovery of bacteria after long-term storage at -80 degrees C was much more efficient when bacteria were stored in a glycerol-based solution than when stored in a dimethyl sulfoxide (DMSO)-based solution. The use of less nutritious bacterial growth media will potentially increase the recovery of bacterial species that can be used to generate electricity in microbial fuel cells.

Review Publications
Vick, B.D., Almas, L. 2011. Developing wind and/or solar powered crop irrigation systems for the Great Plains. Applied Engineering in Agriculture. 27(2):235-245.

Vick, B.D., Clark, R. 2011. Experimental investigation of solar powered diaphragm and helical pumps. Solar Energy. 85:945-954.

Last Modified: 4/23/2014
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