Alternative Energy Sources

Alternative energy sources are resources that are constantly replaced and are usually less polluting. They are not the result of the burning of fossil fuels or splitting of atoms. The use of renewable energy is contributing to our energy supply. Some alternative energy sources are: biomass, geothermal, hydroelectric, solar, wind power, fuel cells, ocean thermal energy conversion, tidal energy, and wave energy.

Biomass is renewable energy that is produced from organic matter. Biomass fuels include wood and forest and mill residues, animal waste, grains, agricultural crops, and aquatic plants. These materials are used as fuel to heat water for steam or processed into liquids and gases, which can be burned to do the same thing. With more use of biomass at lower production costs and better technology, the United States could generate as much as four-and-a-half times more biopower by 2020. It is estimated that biomass will have the largest increase among renewable energy sources, rising by 80 percent and reaching 65.7 billion kWh in 2020.

Geothermal energy uses heat from within the earth. Wells are drilled into geothermal reservoirs to bring the hot water or steam to the surface. The steam then drives a turbine-generator to generate electricity in geothermal plants. In some places this heat is used directly to heat homes and greenhouses, or to provide process heat for businesses or industries. Reykjavik, Iceland is heated by geothermal energy. Most geothermal resources are concentrated in the western part of the United States. Geothermal heat pumps use shallow ground energy to heat and cool homes almost anywhere. With technological improvements much more power could be generated from hydrothermal resources. Scientists have been experimenting by pumping water into the hot dry rock that is 3-6 miles everywhere below the earth’s surface for use in geothermal power plants.

Hydroelectric (hydropower) energy employs the force of falling water to drive turbine-generators to produce electricity. Hydropower produces more electricity than any other alternative energy sources. It has been estimated that hydroelectric power will decline from 389 billion kWh in the U.S. in 1999 to 298 billion kWh in 2020. This decline is expected because most of the best sites for hydropower have already been developed and because of concerns about the adverse impact that large-scale hydroelectric facilities may have on the environment.

Solar energy is generated without a turbine or electromagnet. Special panels of photovoltaic cells capture light from the sun and convert it directly into electricity. The electricity is stored in a battery. Solar energy can also be used to directly heat water for domestic use (solar thermal technology). The domestic photovoltaic (PV) industry could provide up to 15% of new U.S. peak electricity capacity that is expected to be required in 2020.

Wind energy can be used to produce electricity. As wind passes through the blades of a windmill, the blades spin. The shaft that is attached to the blades turns and powers a pump or turns a generator to produce electricity. Electricity is then stored in batteries. The speed of the wind and the size of the blades determine how much energy can be produced. Wind energy is more efficient in windier parts of the country. Most wind power is produced from wind farms—large groups of turbines located in consistently windy locations. Wind, used as a fuel, is free and non-polluting and produces no emissions or chemical wastes. Wind-powered electricity is gaining in popularity.

Fuel cells are electrochemical devices that produce electricity through a chemical reaction. Fuel cells are rechargeable, contain no moving parts, are clean, and produce no noise. Scientists are exploring ways that they could be used as a power source for nearly exhaust-free automobiles and how they can be used as electricity-generating plants. The high cost of manufacturing fuel cells has prevented the mass use of this valuable energy source.

Ocean sources. Oceans, which cover more than 70% of the Earth, contain both thermal energy from the sun’s heat and mechanical energy from the tides and waves.

Ocean thermal energy conversion (OTEC) converts solar radiation to electric power. OTEC power plants use the difference in temperature between warm surface waters heated by the sun and colder waters found at ocean depths to generate electricity.

The power of tides can be harnessed to produce electricity. Tidal energy works from the power of changing tides but it needs large tidal differences. The tidal process utilizes the natural motion of the tides to fill reservoirs, which are then slowly discharged through electricity-producing turbines.

Wave energy conversion extracts energy from surface waves, from pressure fluctuations below the water surface, or from the full wave. Wave energy uses the interaction of winds with the ocean surface. This technology is still in the exploratory phases in the United States.

Energy Statistics: U.S. Energy Information Administration (www.eia.doe.gov)

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