Most of the energy on planet earth comes from the sun. It keeps us warm in the summer. It allows us to grow plants that we consume in order to fuel our bodies and feed animals. These same animals, which get their energy from the sun, eventually break down, and over a process of millennia, become petroleum that can then provide energy to vehicles and other machines. Other plants grown from the sun's energy will be burned to produce heat or other forms of power. However, when we are talking about solar power, we are usually referring to the direct use of solar energy to produce heat or electricity, and not the more indirect methods of accessing the sun's energy. Today, solar energy is usually accessed using solar cells.
Renewable energy comes from energy sources that cannot be depleted. Something like oil or natural gas are nonrenewable energy sources because there is a finite amount of these resources on the planet. Solar power is renewable energy, however, because the sun's energy is effectively limitless. We cannot use it all up. Other renewable sources of energy include wind power and hydroelectricity, or the use of water to turn turbines and generate electricity.
Solar cells access the energy of the sun in two main ways. Photovoltaic cells take the sun's energy and convert it directly to electricity that can be used to power many different things. Non-photovoltaic cells do not generate electricity but they absorb and transmit the sun's heat. An example here would be cells used in a solar water heater. These cells do not create electricity, but they do absorb the heat energy of the sun to create hot water.
Solar power can be used to heat water or air, and this can be done passively or actively. Passive heating systems that use solar energy do not have any mechanical components for moving the heated water or air elsewhere. Passive heating might show up in construction design. For example, architects might place rooms that need to stay warmer than others on the side of a building that will receive the most sunlight. In an active system such as a solar water heater, a pump will send cold water through piping that is embedded in a solar cell. While in the cell, the water will absorb the sun's heat, and then the hot water will be pumped directly to a faucet or to a storage tank for later access.
Solar power can be used to generate electricity through the use of photovoltaic cells. When lights hit these cells, it generates movement of electrons. As these electrons move, they generate a current that is then distributed to a wire, which carries it to where the electricity is needed. Many small devices such as solar calculators use photovoltaic cells to generate electricity. Increasingly, larger cells are used to generate power for homes and businesses.
There are some cool and fun facts about solar power. Here are just a few of them: