Unconventional Energy Sources

Energy from the Sun

• According to the U.S. Energy Information Administration, 8 percent of the total U.S. energy consumption in 2009 came from renewable energy sources, and 1 percent of the renewable energy sources came from solar energy. Sunlight can be converted into heat and electricity. Solar heat collectors are used to concentrate the heat of the sun and produce steam that drives electric generators. Another form of solar technology, photovoltaic or "solar cells," can change sunlight directly into electricity. Electricity generated by solar cells is stored in batteries and transformed to 120 or 240 volts of AC electricity using electric inverters.

Energy from the Wind

• One the fastest-growing sources of energy worldwide, wind generates electricity that powers millions of homes and businesses. The U.S. Energy Information Administration reports that in 2008, worldwide wind power generation exceeded 200 billion kilowatt-hours, or about the same as the annual electricity consumption of more 18 million U.S. households. The wind's energy is harnessed using wind turbines. When the wind blows, it turns the turbine's blades, which spin a shaft that connects to a generator. The generator makes electricity that is then converted into high-voltage electric currents.

Energy from Plants

• Energy can be derived from various plants to produce biodiesel or ethanol. Biodiesel is a renewable and biodegradable diesel fuel extracted from plant oil through a process called transesterification. The U.S. Department of Energy reports that as of 2008, U.S. biodiesel production has increased to a little less than 700 million barrels in 2008 from less than 100 million gallons in 2004. Ethanol is another form of fuel produced from starch and sugar-based plants such as corn grain and sugar cane. Ethanol is a high-octane fuel that works well in specifically designed internal combustion engines.

Hydroelectric Power

• Hydroelectric power is generated from water. As of 2011, the U.S. Department of Energy reports that the equivalent of nearly 500 million barrels of oil can be generated by hydroelectric power facilities in the United States. By using the gravitational force of water as it flows downward, hydroelectric power plants supply electricity to the public. The private sector also uses hydroelectric power to generate electricity to factories and other facilities.