Renewable Energy
In today's world of climbing fuel prices, approaching the peak oil supply limit, and discussions of global warming, renewable energy is gaining more public attention and receiving more financial and legislative support. Here you can learn more about the different types of renewable energy and help educate your family, friends, and policymakers about ways to move toward energy independence and environmental sustainability.
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Biomass
Biomass is a type of material that is derived from plants rather than petroleum. This material can be used to create fuels such as ethanol and biodiesel, which are essentially carbon-neutral. Unlike the burning of fossil fuels which utilize carbon that was previously locked up underground, biofuels utilize plants that take up carbon dioxide. Ethanol and biodiesel can by mixed with or replace gasoline and diesel respectively.
Biomass fuels (or biofuels) and biogas reduce greenhouse gas emissions and dependence on imported oil, while supporting agriculture and rural economies. Biogas can be created from waste (such as manure and garbage), and is used to generate electricity.
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Geothermal
Geothermal energy is harnessed by capturing heat from the earth (Geo=earth, thermal=heat) and using it to produce electricity and provide heating and cooling. Geothermal energy is an underused resource that emits little to no greenhouse gas emissions, is highly reliable, and is produced locally.
Geothermal energy can be used in a variety of ways, such as using a reservoir to generate electricity at a power plant, using piped hot water to warm buildings or melt snow, or using shallow ground energy to heat and cool buildings.
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Hydrogen
Hydrogen gas (or H2) is an abundant element on earth, but because it readily binds to other elements it is rarely found in isolation. Hydrogen can be found in substances such as water, hydrocarbons, alcohol, and biomass. It can be produced using diverse domestic resources including nuclear; natural gas and coal; and biomass and other renewables such as solar, wind, hydroelectric, or geothermal energy. Ideally, hydrogen should be produced using renewable energy that generates little to no greenhouse gas emissions.
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Hydropower
Hydropower - using water to power machinery or create electricity - is the nation's largest renewable energy source. Hydropower takes advantage of the endless nature of the water cycle, which constantly recharges the system through evaporation and precipitation.
There are several types of hydroelectric facilities, and all are powered by the kinetic energy of flowing water as it moves downstream. Turbines and generators convert the energy into electricity, which is then fed into the electrical grid to be used in homes, businesses, and by industry. The use of hydropower must be carefully balanced with preservation of habitats that are altered by changes in water flow.
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Methane Recovery
Methane is the major component of the "natural" gas used in many homes for cooking and heating. By using a biodigesters, methane can be recovered from animal manure through a process called anaerobic digestion. During the digestion process, anaerobic bacteria break down or "digest" organic material in the absence of oxygen and produce "biogas" as a waste product.
Biogas produced in anaerobic digesters consists of methane (50–80 percent), carbon dioxide (20–50 percent), and trace levels of other gases such as hydrogen, carbon monoxide, nitrogen, oxygen, and hydrogen sulfide. This type of energy is most efficient for farms and ranches, since a biodigester usually requires manure from more than 150 large animals to cost effectively generate electricity.
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Nuclear
Nuclear energy is a clean and efficient way of boiling water to make steam which drives turbine generators. Except for the reactor itself, a nuclear power station works like most coal or gas-fired power stations. Commercial nuclear power generation involves containing and controlling the fission reactions of uranium atoms so that the heat produced can be used to make steam, which in turn generates electricity. Nuclear energy has distinct environmental advantages over fossil fuels, in that virtually all its wastes are contained and managed, and there are no greenhouse gas emissions.
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Fusion
Fusion is the process that powers the sun and the stars. In one type of fusion reaction, energy is created during the fusion (or combining) of two hydrogen atoms to create one atom of helium. Since the easiest fusion reaction to create uses materials that are readily available (one of which is water), fusion has the potential to be an inexhaustible source of energy.
Fusion would be environmentally friendly, producing no combustion products or greenhouse gas emissions. While fusion is a nuclear process, the products of the fusion reaction (helium and a neutron) are not intrinsically radioactive. Scientists have sought to make fusion work on earth for more than 50 years. Potentially, commercial application should be possible by the middle of the 21st century.
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Ocean
Oceans cover more than 70 percent of the Earth's surface. As the world's largest solar collectors, oceans generate thermal energy from the sun and produce mechanical energy from the tides and waves. Three different types of ocean energy are tidal power, wave power, and ocean thermal energy conversion.
Some of the oldest ocean energy technologies use tidal power. Tidal power technologies include barrages (or dams), tidal fences, and tidal turbines. Wave power devices extract energy directly from surface waves or from pressure fluctuations below the surface. This energy can be converted into electricity through both offshore and onshore systems. Ocean Thermal Energy Conversion (OTEC) uses the heat energy stored in the Earth's oceans to generate electricity. OTEC technology can also be used to provide air conditioning, chilled-soil agriculture, and cold-water aquaculture.
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Solar
Solar radiation is a general term for the electromagnetic radiation emitted by the sun. We can capture and convert solar radiation into useful forms of energy (such as heat and electricity) using a variety of technologies. The feasibility of these technologies at a specific location depends on the amount of solar access.
Solar access is the availability of unobstructed, direct sunlight, which is important if you use solar energy for space heating (and cooling), water heating, electricity, and/or day lighting. One example of a solar energy system is the photovoltaic (PV) system, which can be a reliable and pollution-free producer of electricity for your home or office. Small PV systems also provide a cost-effective power supply in locations where it is expensive or impossible to send electricity through conventional power lines. Solar landscaping and solar building design are two more ways you can use the sun's energy to your advantage.
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Wind
Wind energy is the process by which the wind is used to generate mechanical power or electricity. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Therefore, wind energy is a form of solar energy.
Wind energy is one of the lowest-priced renewable energy technologies available today. The major challenge to using wind as a source of power is that the wind is intermittent and it does not always blow when electricity is needed.
Additional Resources
- Office of Energy Efficiency and Renewable Energy | U.S. Department of Energy
- Making Biodiesel
- Florida Solar Energy Center
- Post Carbon Institute
- The Oil Depletion Protocol