Humans have been using the energy of the sun for pretty much as long as humans have existed. Going as far back as 5,000 years ago, people of many different religions used to “worship” the sun. For example in ancient Egypt, the sun god, Ra, was considered to be the very first Egyptian king. The sun has been influential in many other religions as well, such as Hinduism, Buddhism, Zoroastrianism, Mithraism, Roman religion, and the Aztecs of Mexico.

In modern times, what science tells us about the sun is that it is the nearest star to our planet, and without it, life on earth would not be sustainable. From the utilization of the sun’s powers to dry wet clothes hanging on a line to plants using the light from the sun to make food, the sun’s energy is used in many different ways today. In fact, in one way or another, the sun and the other stars are responsible for all of the earth’s energy, including nuclear energy, whose uranium atoms were produced in the ferocity of a nova, or an exploding star. Three more specific ways that the energy from the sun is used today are: solar hot water, solar thermal electricity, and solar cells or photovoltaic energy.

Solar water heaters have been used in the United States since the 1890’s. When they were first introduced, solar water heaters proved to be a vast improvement over wood and coal-burning stoves. However, when large deposits of oil and natural gas were discovered in the U.S., solar water heaters started to be replaced with heaters that burned fossil fuels. Solar water heaters are making a comeback today though. In the state of California alone, there are now more than half a million solar water heaters, which heat water to be used in homes, business, and swimming pools. The way that solar water heaters function is that solar panels containing water pipes are placed on the roof of a building. Then, when the sun hits the panels and pipes, it heats them up.

The energy from the sun can also be used to create electricity. The way that this feat is accomplished is through the use of a highly curved mirror called a parabolic trough which concentrates the light from the sun onto a pipe that runs the length of a central point located above the mirror’s curve. As the mirror is concentrating the light onto the pipe, the pipe becomes so hot that it is able to boil water and make steam, which can then be used to move a turbine to create electricity. In the Mojave Desert of California rows of these solar mirrors are arranged together into what is called a solar thermal power plant. This type of plant has the capacity to generate enough electricity for more than 350,000 homes.

Solar cells or photovoltaic energy is a third way of using the sun’s energy. With this method, sunlight is directly changed into electricity through the use of solar cells, which are also called photovoltaic cells or PV cells for short. First developed in the 1950’s, solar cells are composed of silicon and a special kind of melted sand. Their original purpose was to be used on U.S. space satellites, but they can also be found on many household appliances, such as calculators. When sunlight hits a solar cell, it causes electrons to be knocked loose. The disentangled electrons then migrate towards the treated front surface of the solar cell, which consequently creates an imbalance between the electron count on the front and back surfaces of the solar cell. Electricity is generated when the front and back surfaces are joined together by a wire and the positive and negative sides are connected. The individual solar cells are organized together into PV modules, which are then arranged into groups of arrays. The electrical energy from the arrays of solar cell is then able to be used directly by homes and businesses for lights and appliances. It can also be stored in batteries for later use and some experimental automobiles also function through the use of solar cells. The most common use for solar cells, however, is in satellites in outer space.