|Xiarchos, Irene -|
Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: November 15, 2010
Publication Date: April 1, 2011
Citation: Xiarchos, I., Vick, B.D. 2011. Solar energy use in U.S. agriculture. Overview and policy issues. U.S. Department of Agriculture, Office of the Chief Economist. 86 p. Interpretive Summary: The supply of fossil fuels available for energy on farms and ranches in the United States, such as diesel, gasoline, and natural gas, is decreasing. It is important for farmers and ranchers to use more renewable energy, such as solar, to provide energy for the production of food in the United States. Farmers and ranchers are well aware that solar energy is necessary for growing plants, but this report looks at how solar energy can cost-effectively be used to produce electricity and heat for farms, ranches, dairies, vineyards, and other agricultural-based producers. While this report focused on the use of solar energy for farms and ranches, it also analyzed the trends of solar energy use in the United States and throughout the world. One of the biggest findings addressed in the report concerns how solar energy generated electricity in the United States has transitioned from 68% being used for off-grid systems (e.g., livestock watering, fence charging, building lighting) in 1995 to 68% being used for utility grid-tie systems (residential, commercial, and industrial electrical needs, and also large-scale irrigation) in 2008. The transition is even more dramatic around the world because 95% of the solar-generated electricity is being used for grid-tie systems. While it is important to understand the trends in solar energy, a large portion of the report is dedicated to case studies, and various ways to make solar energy economically viable for farmers, ranchers, and rural businesses. This report should help many farmers, ranchers, and rural businesses learn if it is financially viable to use solar energy for all, or a portion, of their energy needs.
Technical Abstract: Using solar energy on farms for livestock watering, electric fence charging, and building lighting is not new in the United States, but in the past five years, solar energy is now being used more for large scale irrigation, heating water in dairies, and running motors/appliances in farm houses and buildings. During the 1980's and 1990's, solar energy on farms was used mainly for off-grid applications such as livestock watering, electric fence charging, and building lighting. In 1995, the percentage of off-grid photovoltaic (PV) systems was 68%, and percentage of on-grid PV systems was 32%, while in 2008 those percentages were reversed (e.g., 32% off-grid and 68% on-grid). This flip in ratio of off-grid to on-grid is mainly due to state incentive programs. California, by far, leads the country in on-grid and off-grid PV systems (528 megawatts in 2008, which is 67% of the total capacity in the United States). Hawaii is the leader in the United States for solar hot water systems with 25%, but Florida and California were second and third with 14% and 12%, respectively. Some dairies are installing solar hot water systems, but significant incentives are required. Examples of the use of solar in agriculture include: (1) a 72-kilowatt PV array for vineyard (lighting, well pumps, etc.), (2) a 268-m2 solar thermal hot water system for a dairy, 3) a 1-megawatt PV array for irrigating various fruits and vegetables on 405 hectares, (4) a 1-kilowatt PV array for livestock watering, (5) a 5.3-kilowatt PV array for almost 100% of farm needs, (6) a co-op installation of over 200 PV systems (averaging 130 Watts per system) for livestock watering in order to save money on transmission line maintenance, and (7) several systems for crop drying using passive solar. A large portion of the report is devoted to financial considerations for use of solar energy on farms such as: (1) state and federal incentives including ones specifically for farmers, (2) cost of electricity in various states, (3) fuel historical trends and solar price trends, (4) which states have net metering and how well the net metering programs are performing, and (5) payback information in United States for residential solar hot water systems and residential solar PV systems. Solar energy use in the United States is growing faster in urban areas than in rural areas. About 1% of the energy used in the United States is in agriculture, so use of solar energy in agriculture is likely to increase; especially with the renewable energy incentives and the trend in fossil fuel prices.