Solar Energy

How Solar Power Works

The sun's energy can be captured to generate electricity or heat through a system of panels or mirrors.

• Solar, or photovoltaic, cells convert sunlight directly into electricity. Most photovoltaic cells are made primarily of silicon, the material used in computer semiconductor chips, and arranged on rectangular panels. When sunlight hits a cell, the energy knocks electrons free of their atoms, allowing them to flow through the material. The resulting DC (direct current) electricity is then sent to a power inverter for conversion to AC (alternating current).
• Solar thermal collectors use heat-absorbing panels and a series of attached circulation tubes to heat water or buildings.
• Solar concentration systems use mirrors -- usually arranged in a series of long, parabolic troughs, a large round dish, or a circle surrounding a "power tower" -- to focus the sun's reflected rays on a heat-collecting element. The concentrated sunlight heats water or a heat-transferring fluid such as molten salt to generate steam, which is then used conventionally to spin turbines and generate electricity.
• Passive solar design is the creative use of windows, skylights and sunrooms, building site and orientation, and thermal construction materials to heat and light buildings, or to heat water, the natural way.

Where Solar Energy Is Used

Organic farmers in New Jersey installed solar panels in a former pasture and saw their monthly electric bill plunge from $1,500 to $2

Commercial concentrating solar power plants have proven particularly effective in the Southwest, but solar power can be used wherever the sun shines. Homeowners, farms and businesses across the country are installing solar water heaters and panels to reduce their electric bills. Many farms and businesses, with their open acreage and/or large buildings, can install enough solar to pay their entire electric bill, or at least reduce costly summer electricity rates, which is often the case for northern states.

At the Oak Grove organic farm in Hunterdon County, New Jersey, Ted and Susan Blew grow hundreds of varieties of specialty hot peppers and other vegetables, several grains, and hog-based pork products for restaurants and other buyers in the New York area. Their solar panels take up one corner of a former horse pasture, with cut flowers planted between them to make the land even more profitable. When the panels were first installed, the farm's monthly electric bill plunged instantly from $1,500 to just over $2, and the Blews had a surplus of more than 500 kilowatts going into their first winter with the system.

In Canton, Minnesota, Philip and Mary Rutter built a solar-powered greenhouse without ever connecting it to the grid, as that would have required them to clear trees, dedicate land and lose productive potential. Instead, they spent $5,600 to create a structure that is partially subterranean, superinsulated with south-facing windows and fully powered -- including lights, fans, water pump and retractable insulating shutters -- by six photovoltaic panels and a small wind turbine. The Rutters expect the energy savings to recoup their costs in ten years, and in the meantime they realize tax benefits by financing the energy system within their mortgage and depreciating it as business equipment.

In southern California's Mojave National Preserve, a 10.88-kilowatt photovoltaic hybrid system provides power for the Hole-in-the-Wall Fire Station -- a site load of 50 kilowatt-hours per day, including the garage and a 16-person dormitory. The flexible, amorphous-silicon roofing laminates are backed up by an inverter, an industrial flooded battery bank, and an on-demand propane generator. The system can be remotely monitored and controlled by the manufacturer, SunWize, if problems arise.

How Much Solar Energy Costs

The cost of solar energy has fallen sharply over the last 20 years, with accelerating price declines in the last 5 years. Still, electricity from a concentrated solar power plant can cost about 10 to 14 cents per kilowatt-hour, compared with about 4 cents per kilowatt-hour from a coal or natural gas power plant.

Electricity from small or medium-scale solar installations, such as those on homes or businesses, costs around 12 to 30 cents per kilowatt-hour, but these prices should continue to drop thanks to falling installation costs, accessible, low-cost, long-term financing, and a healthy number of incentives and tax packages offered by nearly every state government. The current federal incentives include a 30 percent investment tax credit (ITC) and a five-year modified accelerated cost recovery system (MACRS), which allows system owners to deduct federal taxes on an accelerated timetable of system value depreciation.

Advantages of Solar Energy

• Sunlight is free and infinitely renewable.
• Unlike conventional fossil fuel and nuclear power, solar power produces 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 power can slash utility bills for both residential and commercial consumers. By installing solar panels on its enormous roof, Hawaii's Mauna Lani Bay Hotel began saving enough on energy bills to pay for the investment in just five years.
• Solar panels can help utilities avoid brownouts and blackouts. When demand for electricity is high, utilities can use the panels to generate extra energy rather than fire up expensive and polluting "peak" power plants that otherwise lie dormant.
• Several solar panel manufacturers are based in the United States, employing about 20,000 people in high-earning, high-tech jobs. This domestic industry helps reduce our dependence on foreign oil, coal and natural gas.

What's around the Corner for Solar Energy

• Massive concentrating solar-power plants will be built in the Southwest, providing clean electricity for millions of homes and businesses in the region. California's Blythe Solar Power plant, the world's largest, is expected to go online by 2013. According to Sandia National Labs, costs are expected to fall to about 5 cents per kilowatt-hour by 2020, a price competitive with those at new coal- or gas-fired power plants.
• Solar panels will be cheaper and more efficient thanks to cheaper raw materials, improved production methods, more engagement from utility companies, and bold government programs like the Department of Energy's SunShot initiative. Financial analysts and industry experts expect the cost of solar power to fall below retail electricity rates in much of the country between 2013 and 2018.