The sun is a fairly large fusion reactor and solar energy is the dominant form of primary energy on Earth, contributing about 10% to total global annual primary energy consumption. However, only a small fraction (about 1%) of this solar energy can be used easily and directly by humans as the sunlight spectrum does not contain enough visible light. But alas, perhaps this is only by design of our limited understanding of the universe and there may be other ways to harness the energy of the sun on the near or very distant horizon.
Currently, there is no efficient way to capture the sun's energy directly. It would prove to be highly difficult and we wouldn't have enough optical material to absorb it all anyway. The most viable option for solar power involves capturing the kinetic energy of particles emitted by the sun, which are called photons. Any modern solar cell consists of a number of semiconductor layers, a substrate and plastic film for covering. The cells are usually small but can be as large as rooms.
The first solar cell was built in 1883 by Charles Fritts, using a porcelain coated with selenium. The solar cells are most commonly made of silicon, because it is a semiconductor and also abundant in the Earth's crust. The efficiency of converting sunlight into electricity continues to improve over time as the technology improves; modern cells can convert up to 40% of incident light directly into electricity.
Solar cells are used to power calculators, watches, computers and other devices. In these cases they provide a small fraction of the overall energy demand. They also can be used as heating elements in solar thermal collectors. Solar energy solutions have been in development for a long time but they continue to find new waves of progress and perhaps in the future, the planet’s energy situation may involve even more solar based energy solutions.
Sources
https://www.aps.org/publications/apsnews/200904/physicshistory.cfm
