Introduction to Solar Energy

imagesThe sun has been used as a source of energy for thousands of years. Since the ancient times civilizations like the Mayas, the Aztecs, the Greeks and the Romans used solar power to heat their homes and cook food. The sun was regarded in many of these ancient civilizations as a God who was worshiped in religious ceremonies. Only during the modern times however the human civilization has developed the technology to capture solar energy and produce from it electricity for homes and industries.

Solar energy is essentially the radiation of the sun that reaches the Earth. In one whole year the Earth receives almost 174 petawats (PW) of incoming solar radiation. From this energy a 30% is reflected back to space and the rest is being absorbed by oceans, clouds and land. The solar light that reaches the earth ranges from the visible to the infrared part of the spectrum and equals to 3.850.000 exajoules per year.

At solar thermal power plants solar energy is captured and turned first into heat and then electricity. At these plants the heat from the sun is used to warm up water and produce steam. This steam is used to generate a turbine that produces mechanical energy. This mechanical energy is turned afterwards into electricity with the use of a turbine in order to warm up water for homes, heat up greenhouses and for other industrial purposes.

Solar energy can be turned directly into electricity through the use of Photovoltaic cells (PV). A photovoltaic cell is a non-mechanical device that is usually made of silicon. When the photons from the sun hit the surface of the photovoltaic cell they cause a certain amount of electrons to be removed. This creates an electrical charge that when connected to an external generator can produce electricity. Individual PV cells are combined into panels to produce electricity in larger scales.

Through this kind of technologies an enormous amount of solar power can be captured and used for electricity production. Given the fact that solar energy does not pollute the atmosphere solar thermal power plants and photovoltaic cells can be a great way to cover our energy needs without further destroying nature.

Photo by / NASA’s Solar Dynamic Observatory

What is your opinion on solar energy, solar thermal power plants and photovoltaic cells? Please let me know in the comments below.


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