Green Energy for the Battlefield

Tuesday, July 01 2008 While biomass is the oldest form of renewable energy, hydropower is the most successful. Hydropower uses water to create electricity, usually through a dam. Water flow, regulated by the dam, turns turbines, which turn generators and create electricity. With a dam, water flow is available and controlled, producing a high, consistent flow of electricity. As an example, the Hoover Dam produces on average 4.4 billion kilowatt hours per year — enough to serve 1.3 million people. Overall, hydropower produces 42% of the nation’s renewable energy and is the second leading producer — recently surpassed by biomass.

Geothermal technologies use steam and hot water generated from the earth to produce power. Steam or hot water extracted from the ground turns a turbine linked to a generator that produces electricity. Geothermal power plants produce energy efficiently for five cents per kilowatt-hour and are almost emission- free.

Wind power is a growing source of alternative energy. In 2005, the U.S. installed more new wind farms than any other country in the world. Wind power is renewable, creates no emissions and requires no sources of oil. Wind-generated energy is also inexpensive, costing between four and six cents per kilowatthour. Today, the U.S. generates over 11,600 megawatts from wind farms — enough electricity to power over 2.3 million households.

Wind power is actually a form of solar energy, since the Sun creates wind. The wind generates electricity by turning a blade that connects to a shaft that turns a generator. The size of the windmill determines the potential power generation, which can range anywhere from 100 kilowatts to several megawatts. Multiply a single windmill output by the number of windmills in a wind farm and the power generation is significant. Because the wind must blow to generate power, creating a stable supply of electricity is a challenge for wind power. Batteries can store the energy generated or a complementary source of power can augment the system.

The Sun provides renewable energy in several manners. The two most mature and common forms of solar power include photovoltaics, a semiconductor material that converts sunlight directly to electricity and solar heating, where the Sun’s energy directly heats water or building interiors. Two areas of ongoing solar research include concentrating solar power (CSP) and solar lighting. CSP is the process where the Sun’s heat energy is concentrated through mirrors and drives a generator that produces electricity.