How do solar panels work?

With all the news about solar power lately, I thought it would be useful to go back to how solar panels work.

The short description goes something like this: Silicon is mounted beneath non-reflective glass to produce photovoltaic (PV) panels that collect photons from the sun and convert them into DC electrical power. That DC power then flows into an inverter, which transforms it into basic AC (alternating current) electrical power.

Okay, that’s the short and simple answer, but others may want more information. A useful website, Solar Home, offers an in-depth answer to the question, especially about one of the key materials, silicon.

Solar Home writes: “Silicon has four electrons in its outer shell. However, it has the capacity to hold eight. By sharing these four electrons with other silicon atoms and their four shell electrons, the capacity of eight is filled. When they combine with each other in this way, silicon atoms develop a strong, stable bond. This structure is known as pure, crystalline silicon.”

Pure silicon, however, is not a good conductor of electricity because there aren’t any electrons that are free to move. In other words, adds the author, “The silicon is better off with impurities.”

Thus, silicon is combined with an element such as phosphorus, which has five electrons to share. As a result, a negative charge is created. Silicon can only take four of the five electrons, leaving one free electron – called a free carrier – to carry an electrical current.

Other methods for manipulating silicon are also used. For instance, when silicon is combined with an element containing three electrons, a positive charge can be created. Boron is one material that suits this purpose. When silicon and boron are combined, holes are created.

“These silicon combinations and their differing charges are used to make solar panels. As photons come down from the sunlight and strike the silicon, it shakes everything up. The free electron that was hanging onto the silicon/phosphorous combination is now forced to the outer ring. From here, it gets sucked up to the outer ring of the silicon/boron combination. This is how electricity is created.”

NASA Science also provides solid information on the subject, writing that the photoelectric effect was first noted by a French physicist, Edmund Becquerel, in 1839. He learned that certain materials would produce small amounts of electric current when exposed to light. Here we learn that, in 1905, Albert Einstein described the nature of light and the photoelectric effect on which photovoltaic technology is based. For this discovery, he eventually won a Nobel Prize in physics.



This NASA diagram illustrates the operation of a basic photovoltaic cell, also called a solar cell, the building block of solar panels. Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity. This electricity can then be used to power a load, such as a light or a tool.



http://cleantechnica.com/2011/09/30/solar-basics-how-do-solar-panels-work/?utm_sourc e=feed burner&utm_medium=feed&utm_campaign=Feed%3A+IM-cleantechnica+%28CleanTechnica%29