Solar energy, or solar power, is the harnessing of solar radiation as an energy source for homes, offices, factories, and transportation. Solar energy systems capture the sun’s energy using solar panels, which themselves are composed of solar cells (also called photovoltaic cells or PV cells). A PV solar system can immediately convert solar energy into an electric current, which can power appliances, charge home batteries, or be fed back into the electrical power grid. Meanwhile, solar thermal systems collect heat from the sun’s rays and apply that heat to a variety of applications.

Solar energy technologies offer benefits over fossil fuels such as coal, oil, and natural gas.

1. The supply is essentially unlimited. The sun is the most powerful energy source in our solar system; without it, our planet could not even exist. This makes the sun the ultimate source of energy production.

2. It’s useful in a variety of applications. Small solar energy installations can power homes without being connected to a power grid. Meanwhile, solar power plants, which typically occupy large areas in sunny, rural regions, can meet the energy demands of small towns and areas within cities. An enormous amount of energy could come from solar power, provided that storage technology and transmission lines can keep up with energy demands.

3. It’s more renewable than other forms of energy. Though the capture of solar energy requires the manufacture, maintenance, and eventual replacement of solar panels, its conversion into usable energy produces no greenhouse gases such as methane or carbon dioxide—both of which result from the burning of fossil fuels. And, unlike current nuclear power plants, solar power does not leave behind toxic nuclear waste. (Note that nuclear fusion plants would not produce nuclear waste, but such technology is not yet viable for meeting global energy needs.)

Most solar energy production comes in one of two forms:

• Photovoltaic energy production: In this form of solar electricity production, solar panels containing photovoltaic cells receive photons from the sun’s rays. The solar energy charges a semiconductor within these PV cells, in turn generating an electric current that flows through electrical wires. This current manifests as direct current (DC), but to work with the U.S. electrical grid, it must convert to alternating current (AC). A device called a solar inverter handles this final step.
• Solar thermal energy capture: This form of solar technology can capture the heat energy from sunlight and put it to a variety of uses. High temperature solar thermal energy can generate electric power, sometimes by heating water in a storage tank. The water turns to steam, which turns turbines and thereby produces electrical current. This use of solar energy is quite similar to the energy conversion processes of hydropower and fossil fuel plants.

Solar energy can power entire towns or individual homes.

• Large-scale solar power: The sun’s energy reaches all parts of the earth’s surface, although it is particularly intense near the equator and at higher altitudes. Many of the globe’s largest solar power systems exist in such regions—or in desert areas where plant foliage does not block incoming sunlight. On a solar power plant, an expanse of solar panels and mirrors called a solar array captures incoming sunlight. Photovoltaic cells convert this solar energy into electrical current, which power lines carry to population centers.
• Small-scale solar power: Homes may provide their own solar power thanks to solar panels on residential roofs. Since solar power only exists when the sun is shining, most home solar systems use large batteries for energy storage. These batteries charge up during sunny days and then steadily discharge as the home consumes energy through the night and on cloudy or rainy days. Solar thermal energy shows up in technology such as solar water heaters. In this form of solar heating, solar collectors capture radiation and channel the heat into water tanks. This heats the water in lieu of a natural gas flame, which makes solar water heating another green technology.