Solar Power

Solar power is throwing light on the possibilities of using renewable energy sources instead of fossil fuels to generate electricity.

Imagine generating enough power from the sun to handle all of the nation's electricity needs. Using today's technology, some scientists say it would take 10,000 square miles of solar panels to meet demand. That sounded like lot of real estate, until they calculated it's about one-fourth of all the space taken up by rooftops and pavement in US cities.

The Energy Foundation is taking a different view. The group said installing solar panels on all the roofs of homes and businesses across the US could provide 710,000 megawatts of electricity. That's nearly three-fourths of the nation's 950,000 megawatt capacity.

What's stopping the nation from turning rooftops into electricity generators? The cost.

Energy from solar panels, just one form of directly harnessing the sun's energy, costs $4 to $6 per watt, compared to an average $1 per watt for energy from traditional fossil fuels - coal, natural gas and oil. However, as the costs of fossil fuels go up, technological advances in generating electricity from several types of solar power devices are lowering the cost and increasing efficiency. Add to that the state and federal incentives for renewable energy, and observers see solar as a competitive option.

The production and installation of solar panels (made of hundreds of photovoltaic cells that directly turn sunlight into energy) are the fastest-growing type of solar power in the US. Small photovoltaic cells can power a hand-held calculator, but hundreds mounted on a roof can power appliances in a home. What's more, surplus electricity can be stored in batteries or sent back across the grid to the power utility - in many states for a subsidized rate paid back to the owner of the solar panels.

Industry reports show the US experienced a 27 percent growth in photovoltaic cell system installations in 2004, accounting for about 83 megawatts. That's nine percent of the worldwide growth, led by Germany and Japan where governmental programs push renewable energy.

Photovoltaic system costs are high partly because of the clean-room fabricating conditions necessary for its major component, crystalline silicon. A shortage of that material has caused a bottleneck in production. Higher production rates and newer technology is needed to bring the price down to $2 to $2.50 per watt; that's where the Energy Foundation says solar will be competitive (when state and federal incentives are figured) with electricity from traditional sources. If that price is reached by 2010, the foundation forecasts PV solar installations of 2,900 megawatts a year - enough to power half a million average US homes.

While photovoltaic solar panels have enjoyed double-digit growth the past few years, the biggest impact might be made by large systems called concentrating solar power (CSP). Although all the traditional solar panels in the US produce an estimated 340 megawatts of electricity, an array of nine CSP units in the California desert have been producing 350 megawatts directly for utilities since the late 1980s. Although construction of these types of high capital-cost facilities has been stagnant for a decade, several are in the planning stages in the sunny Southwest.

CSP systems either utilize large solar dishes, parabolic troughs or a tower arrangement to reflect the sun's energy to heat liquid - water, oil, or molten salt - which in turn powers a turbine that generates electricity. The Department of Energy's National Renewable Energy Laboratory (NREL) says these CSP systems can cover peak electricity demand for utilities in western states where unreliable natural gas supplies, decreasing hydro power due to drought, and increasing demand create brownouts and blackouts for consumers.

The NREL and Department of Energy are working with utilities, private industry and state governments throughout the west to install 1,000 megawatts of new CSP generating capacity by 2010. Engineers say these large-scale projects could reduce the startup costs for solar power plants to a competitive level.

The first such project in the solar pipeline is Nevada Solar One in Boulder City, Nevada, a 64-megawatt system that NREL says would be the largest solar power facility built in the world in the past 14 years. It's scheduled to go online in 2007. Two others, which would eventually generate a combined 800 megawatts, are under consideration in California.

Observers don't expect interest in solar power to dim. The Energy Policy Act enacted in 2005 offers tax breaks for installation of home solar power projects and supports large commercial operations. Paired with the interest to reduce greenhouse gas emissions, it could mean there is a light at the end of the tunnel for solar power.