Solar electricity generation represents a clean alternative to electricity from fossil fuels, with no air and water pollution, no global warming pollution, no risks of electricity price spikes, and no threats to our public health.

Solar energy can also heat water, cool and heat homes, and provide free, natural lighting. And once a system is in place to convert the solar resource into useful energy, the fuel is free.

The solar resource is enormous

Just 18 days of sunshine on Earth contains the same amount of energy as is stored in all of the planet's reserves of coal, oil, and natural gas.

Outside the atmosphere, the sun's energy contains about 1,300 watts per square meter. Once it reaches the atmosphere, about one-third of this light is reflected back into space, while the rest continues toward Earth’s surface.

Averaged over the entire surface of the planet, a square meter collects 4.2 kilowatt-hours of energy every day, or the approximate energy equivalent of nearly a barrel of oil per year.

Deserts, with very dry air and little cloud cover, receive the most sun—more than 6 kilowatt-hours per day per square meter on average over the course of the year.

Photo: NASA Goddard Space Center

Converting solar energy into electricity

Photovoltaic (PV) panels and concentrating solar power (CSP) facilities capture sunlight and convert it into useful electricity.

Rooftop PV panels make solar power viable in virtually every part. In a sunny location, a five-kilowatt residential system produces an average of 7,000 to 8,000 kilowatt-hours per year, roughly equivalent to the electricity usage of a typical household.

Solar achieves similar results in many other parts of the country as well.Like rooftop panels, large-scale PV projects use photovoltaic panels to convert sunlight into electricity. These projects often have outputs in the range of hundreds of megawatts, which can involve millions of solar panels installed over a large area of land. In addition to scale, outputs can be increased with specialized tracking mechanisms that allow panels to follow the sun and collect light at an optimal angle, greatly increasing the system’s efficiency.

Concentrated solar power (CSP), instead of using the sun’s light, takes advantage of the sun’s heat to produce a heated liquid and steam that drives a turbine.

Given the abundance of sunshine across the country, solar has the potential to supply a rapidly growing amount of electricity that is environmentally and economically attractive, nationwide.

Related:

- The solar resource >>>

- How solar panels work >>>

- Rooftop solar panels: Benefits, costs, and smart policies >>>

- Solar power plants: Large-scale PV >>>

- Concentrating solar power plants >>>

[Union of Concerned Scientists,ucsusa.org]