Renewable Sources of Energy
Renewable energy sources are sources that are constantly replenished. This includes solar, wind, water, geothermal and biomass. Renewable sources are non-polluting and do not produce any greenhouse gases. Renewable sources of energy are becoming more and more popular around the world.

Water is the most common renewable source of energy in the United States. The most form used is hydroelectricity. This is made from hydroelectric plants by using water to turn a turbine, which turns a generator. This accounts for about 7 percent of the electricity used in the United States. It is one of the most least expensive renewable sources. The Northwest, the Tennessee Valley and Colorado are states that use the most hydroelectricity dams.

Wind is a very fast growing renewable source. It generates power without causing pollution. In the United States, wind power supplies about 1 percent of the electricity needed. The most common hazard is to wildlife. This can be kept to a minimum during manufacturing.

Solar power has great potential, yet it only provides the United States with about 1 percent of the energy needed. The more efficient solar power becomes, the higher this number will grow. Passive solar designs capture the sun’s heat to provide heating and light. Photovoltaic cells are used for creating direct electricityfrom sunlight. To obtain hot water or space heating, flat-plate collectors are used. With this system, the fluid will absorb the sun’s heat directly. The major disadvantage of solar power is the cost.

Geothermal power is the use of the internal heat of the earth. Most of the power generated in geothermal power comes from steam or in some cases, underground hot water. The good thing about this source is that it is always available. There are three systems in geothermal power. Direct use, reservoirs and heat pumps are the three main systems. The states that use geothermal power plants are Hawaii, California, Nevada and Utah. Even though it is environmentally friendly, reliable and efficient, it provides less than 1 percent of the energy needs in the United States.

Biomass power is obtained by using the energy from plants and plant-derived materials. Biomass can be used in just about anywhere in the world. It may help to reduce global warming and it produces fewer pollutants than fossil fuels. The electricity generated from biomass is called biopower. Pulp and paper industries are major producers of biopower in the United States.
References

http://www.nationalatlas.gov/articles/people/a_energy.html