Biomass
 | Most biopower plants use direct-fired systems. They burn bioenergy feedstocks directly to produce steam. This steam drives a turbine, which turns a generator that converts the power into electricity. In some biomass industries, the spent steam from the power plant is also used for manufacturing processes or to heat buildings. Such combined heat and power systems greatly increase overall energy efficiency. Paper mills, the largest current producers of biomass power, generate electricity or process heat as part of the process for recovering pulping chemicals. Learning about Renewable Energy: Biopower. Retrieved August 3, 2007 from http://www.nrel.gov/learning/re_biopower.html |
Geothermal
 | Geothermal power plants, however, use steam produced from reservoirs of hot water found a couple of miles or more below the Earth's surface. There are three types of geothermal power plants: dry steam, flash steam, and binary cycle. This geothermal power plant generates electricity for the Imperial Valley in California.
Learning about Renewable Energy: Geothermal Energy Production. Retrieved August 3, 2007 from http://www.nrel.gov/learning/re_geo_elec_production.html. |
Wind Power
 | Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor.
A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity. Learning about Renewable Energy: Wind Energy Basics. Retrieved August 3, 2007 from http://www.nrel.gov/learning/re_wind.html |
Solar Power
 | The sun's heat and light provide an abundant source of energy that can be harnessed in many ways. There are a variety of technologies that have been developed to take advantage of solar energy. These include concentrating solar power systems, passive solar heating and daylighting, photovoltaic systems, solar hot water, and solar process heat and space heating and cooling. Beyond these localized uses of solar power, utilities and power plants are also taking advantage of the sun's abundant energy resource and offering the benefits to their customers. Concentrating solar power systems allow power plants to produce electricity from the sun on a larger scale, which in turn allows consumers to take advantage of solar power without making the investment in personal solar technology systems. Learning about Renewable Energy: Solar Energy Basics. Retrieved August 3, 2007 http://www.nrel.gov/learning/re_solar.html |
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