Solar power converts the sun's energy into a pollution-free source of heat, lighting and electricity. Thanks to technological leaps in solar panels, the cost for solar power has come down dramatically in the past few decades, and solar is now spreading across the suburban United States and into businesses, industry and power plants. We also rely on solar energy for many of the conveniences of modern life, from highway signs to ATM machines.

How It Works

The sun's energy can be actively captured to generate electricity or passively harnessed to heat water or buildings.

• Solar, or photovoltaic cells, convert sunlight directly into electricity. They're usually made primarily of silicon, the same material used in computer semiconductor chips. When sunlight hits a solar cell, the energy knocks electrons free of their atoms, allowing them to flow through the material, resulting in direct current (DC) electricity.



• Concentration systems use mirrors to focus the sun's energy. The concentrated sunlight heats water or a heat-transferring fluid to generate steam. This steam is used just like in a conventional power plant -- to spin a turbine and generate electricity.



• Collectors use heat-absorbing material to harness sunlight for heating water or buildings.



• Windows, sunrooms and skylights allow the sun to heat and light buildings.

Where It's Used

Solar power can be used wherever the sun shines, even in outer space. It can work on cloudy days, too.

• More suburban homeowners across the country are turning to solar panels to drive down electrical bills. In California, residential installations rose 53 percent in 2004, thanks to a generous state rebate program. New Jersey expects the number of homeowners applying for state rebates to double in 2005. (To find out if your state and utility have such programs, visit www.dsireusa.org.)



• In the southwestern United States, nine commercial concentrated solar power plants produce about 354 megawatts of electricity. That's enough to power more than 85,500 homes per year.



• Many of the technological advances that make daily life more convenient rely on solar energy, including highway traffic signs, cell phones, automated teller machines, pagers, global positioning systems, microwave transmissions and direct TV.



• Because they are so reliable and require virtually no maintenance, solar cells generate power for nearly every communications satellite circling Earth and space missions such as the Mars Sojourner and Mir Space Station.



• Solar water heaters provide hot water for private homes and institutions and warm up outdoor swimming pools and spas. (Could a solar water heater provide enough hot water for your home? Learn more.)

How Much It Costs

The cost of solar energy has been sharply reduced over the past 20 years. Still, electricity from concentrated solar power plants costs about 10 to 14 cents per kilowatt-hour, while electricity from a coal or natural gas power plant costs about 4 cents per kilowatt-hour. Electricity from solar panels installed on homes and businesses costs 25 to 40 cents per kilowatt-hour, but these prices should continue to fall thanks to lower installation costs and the growing number of incentives and tax packages now offered by more than 30 states.

Advantages

• Sunlight is free and infinitely renewable.



• Unlike conventional power plants, solar panels produce no polluting emissions, including those that cause global warming.



• With no moving parts, solar panels are silent, easy to operate and rarely need maintenance.



• Solar panels help utilities avoid brownouts and blackouts. When electricity demand is high, such as during a heat wave, utilities could use solar panels to generate energy rather than firing up expensive and polluting "peak" power plants designed only to operate when demand is highest.



• Solar panels installed on the roofs of residential and commercial buildings can slash utility bills. For instance, by installing solar roof tiles, Hawaii's Mauna Lani Bay Hotel will save enough in energy bills to pay for the investment in just five years.



• Solar energy is produced here in the United States, employing about 20,000 men and women in high-tech, high-earning jobs. This domestic industry helps reduce our dependence on foreign oil, coal and natural gas for heating or powering our homes.

What's Around the Corner

• One million solar energy systems will be installed on rooftops across the United States by 2010. The Department of Energy's Million Solar Roofs program kicked off in 1998 and is already ahead of schedule. The installation of these systems could eliminate carbon dioxide emissions equal to that produced by 850,000 cars.



• More concentrated solar power plants will be built in the Southwest, providing clean electricity for millions of homes and businesses around the region. According to Sandia National Labs, costs are predicted to fall to about 5 cents per kilowatt-hour by 2020, a price competitive with new coal- or gas-fired power plants.



• Solar cells will become cheaper and more efficient, both through the use of less expensive materials, improved production methods and easier installation systems. Researchers aim to make them cost-competitive with traditional electricity by 2015.

Overview | Wind | Solar | Biomass

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