Re-Thinking Energy in Homes

Where does green electricity come from?

By harnessing wind, sunlight, plant matter or heat from the Earth's core, we can produce electricity in ways that curtail global warming pollution. And because electricity demand is based on consumer choices, the more we demand green power, the more cleaner sources will be used. That means a lot less heat-trapping pollution.

Wind. Wind turbines, or windmills, use strong wind to create pollution-free, renewable electricity. Wind power is already as cheap as fossil fuel-generated electricity in some places. The windier the location, the lower the cost is, and the more energy that can be produced. Wind energy is most economical in places where average wind speed is at least 17 miles per hour. New York-based Brooklyn Brewery is one company powered completely by wind. Its annual savings of heat-trapping emissions are about 335,000 lbs of CO2.

Solar. The sun's energy can help produce electricity in two ways: photovoltaic (PV) systems and solar thermal systems. PV systems change sunlight directly into electricity. They are common where it is relatively expensive to run electrical wires or use batteries, such as in rural homes, remote research stations and freeway call boxes. Solar thermal systems use the sun's energy to heat a fluid that produces steam, which then turns a turbine and generator. California's Luz SEGS plants are the principal solar thermal generators in America. Although solar technologies are more expensive than other options now, they are cost-effective where people are allowed to sell electricity back to the grid, and several states offer subsidies to stimulate investment.

Geothermal. Geothermal energy is generated by converting the hot water or steam from deep beneath the Earth's surface into electricity. Geothermal plants emit very little air pollution and have minimal impacts on the environment. They are very economical, competing favorably with fossil fuel generation. Currently, geothermal plants in the U.S. provide enough electricity to supply the homes of 3.5 million people. Known geothermal reserves and technology could supply the entire country with electricity for 30 years.

Biomass. Biomass — crop parts or animal waste that can make energy — is an extremely versatile fuel source. It can provide electricity, heat buildings and factories, and power cars and trucks.

When the technology first took off, biomass was burned in an incinerator to produce energy. In newer facilities, the biomass is converted into a combustible gas, allowing for greater efficiency and cleaner performance. Biomass sources include agricultural, forestry and food processing byproducts, as well as gas emitted from landfills. Though not as clean as wind and solar energy and a bit more expensive (because of transportation costs from source to incinerator), its environmental benefits are a significant plus because biomass generates few or no heat-trapping gases. Biomass supplies 2% of the electricity used in California.

Sources

Emissions of Greenhouse Gases in the United States 2003. Energy Information Administration. www.eia.doe.gov/oiaf/1605/gg04rpt/carbon.html (18 February 2006).

National Renewable Energy Laboratory.

Renewable Energy Trends, 2003, Energy Information Administration, July 2004, www.eia.doe.gov/cneaf/solar.renewables/page/rea_data/trends.pdf

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