Electricity generation accounts for 33 percent of total U.S. greenhouse gas emissions, according to the Environmental Protection Agency. To reduce these emissions, the electricity generation industry needs to decrease its use of fossil fuels. One way of doing that is through energy efficiency, with systems like combined heat and power (CHP), district energy, and smart grids. Another way of decreasing fossil fuel use is by switching to alternative energy sources, such as renewable energy.
Renewable energy is derived from resources that are replenished naturally on a human timescale. Such resources include biomass, geothermal heat, sunlight, water, and wind. All of these sources have their strengths and weaknesses. Some are more suited to certain locations that others, for instance. Some only produce electricity intermittently (when the sun is shining in the case of solar), though they can be paired with energy storage solutions to provide reliable electricity 24 hours a day throughout the year. Others, such as biomass, hydropower, and geothermal, can be used as baseload generation, producing a constant, predictable supply of electricity. None of these sources can meet all of our electricity needs effectively. But, together, they can completely displace fossil fuels without increasing the cost of electricity.
Below you will find a quick overview of the different renewable energy technologies, with links to more in-depth information. Implementing all of these renewable energy technologies, in addition to energy efficiency measures, not only leads to fewer greenhouse gases and other air and water pollutants, but also leads to overall cost savings and enhanced energy security.
Biomass (plant or animal material) can be used to produce electricity, thermal energy, or transportation fuels. Every region has its own locally generated biomass feedstocks from agriculture, forest, and urban sources.
Hydrogen fuel cells are a clean, reliable, quiet, and efficient source of high-quality electric power. They use hydrogen as a fuel to drive an electrochemical process that produces electricity, with water and heat as the only by-products.
Water technologies can be used for electricity or thermal energy all across the country. Although there are few, if any, appropriate sites left to build large dams in the United States, there are many opportunities to expand energy production at dams without turbines and by using newer technologies in both rivers and oceans.
Wind energy can be used to generate electricity for utilities or individual buildings. The best U.S. resources for utility-scale wind farms are in the Midwest, Texas and the West, as well as on offshore sites in the Great Lakes and off the Atlantic Coast.
Geothermal energy, or the heat below the earth's surface, can be used for electricity or thermal energy. Geothermal heat pumps, which heat and cool buildings, are effective in all regions. Geothermal power plants, however, require more active geothermal sources that, in the United States, are primarily located in the West.
Solar energy systems use the sun's rays for electricity or thermal energy. In the United States, utility-scale solar power plants are located primarily in the Southwest. However, smaller scale rooftop photovoltaic cells and hot water systems are effective in all regions.