Renewable resources are valuable because they provide "green" energy.
Renewable resources are an important aspect of sustainability. According to the U.S. Energy Information Administration, the most frequently used renewable resources are biomass, water, geothermal, wind and solar (see References 1). Unlike fossil fuels, we can regenerate or replenish these resources. Although biomass in the form of wood once supplied 90 percent of U.S. energy needs, all renewable energy sources combined supplied only about 8 percent of in 2009 (see References 1). With the rising cost and decreasing availability of nonrenewable fossil fuels, renewable resources are receiving increasing attention.
Biomass resources include trees, food crops, algae, agricultural and forestry byproducts, and even Methane fumes from landfills. These biomass resources provide fuels, power production and products typically made from nonrenewable fossil fuels. Such bioproducts include plastics, insulation, adhesives and fabric. Energy production from biomass is important because it can help reduce dependence on foreign oil. In addition, it has the potential to reduce greenhouse gas emissions. The agricultural and forestry industries also benefit from the demand for biomass. (See References 3)
Water, or hydropower, is the renewable energy source that produces the most electricity in the United States. In 2009, it accounted for 7 percent of total U.S. electricity generation and 35 percent of generation from renewables in 2009, according to the U.S. Energy Administration. Like wood, water has a long history as an energy source. Paddle wheels used to grind grain are an early example. In the 1880s, the Wolverine Chair Factory in Michigan made use of a water turbine and the first hydroelectric plant was built on Wisconsin's Fox River to harness the power of swiftly-moving water. Hydroelectric power plants proliferated with the ability to transmit electricity over longer distances. The release, as needed, of water stored in reservoirs behind dams produces electricity by spinning turbines as it flows through pipes. (See References 4)
Geothermal energy comes from harnessing heat from the Earth. A large utility company, for example, can directly use a geothermal reservoir to drive generators and produce electricity for their municipality. In contrast, residential heat pumps use the shallow ground temperature of the Earth to heat and cool a home on a smaller scale. The shallow ground temperature remains between 50 and 60 degrees Fahrenheit. Other applications put geothermal heat to use in commercial buildings, roads, agriculture and industrial factories. (See References 5)
Wind is just moving air created as the sun heats the Earth's surface. As long as the sun is shining, the wind remains an infinite, renewable resource. Wind power is clean energy because wind turbines do not produce any emissions. The classic Dutch windmill harnessed the wind's energy hundreds of years ago. Modern wind turbines with three blades dot the landscape today, turning wind into electricity. Although wind only generated little power in the United States in 2009, it is the fastest-growing source of new electric power, according to U.S. Energy Information Administration. (See References 6)
The sun has produced energy in the form of heat and light since the Earth formed. Solar energy systems do not produce emissions and are often not harmful to the environment. Thermal solar energy can heat water or buildings. Photovoltaic devices, or solar cells, directly convert solar energy into electricity. Individual solar cells grouped into panels range from small applications that charge calculator and watch batteries, to large systems that power residential dwellings. PV power plants and concentrating solar power plants are the largest solar applications, covering acres. (See References 2)
Clean and Renewable Energy Systems
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