Solar Power Information
This whole page is pretty dry; but it deals with the scientific principles of how solar power works. If you are a gal or guy who is really, really interested in the scientific principles behind solar power - read on - you have found heaven!
But if you just want to get enough solar power information to see if solar is right for you; then just scroll down and click one of the links below.
You will be glad that you did - otherwise, this page will make your your head hurt.
How Solar Roof Tiles Work
Solar roof tiles convert one form of energy (sunlight) into another form of energy (electricity). If the sunlight is reduced or stopped - as when a cloud passes in front of the sun or when night falls, the conversion process slows down or stops completely. When the daylight returns, the conversion process starts again. Solar cells do not store electricity. At night, a solar electric system needs some form of battery storage from which to draw power. How Solar Roof Tiles Work Solar roof tiles turn light into electricity without moving parts, without noise, pollution, radiation and without maintenance or monitoring. The special properties of semiconductor materials used in solar roof tiles make this possible. You can find more details about solar roof tiles by searching for more solar power information.
Semiconductors
Most solar roof tiles are made from silicon. Other materials are used as well, but the basic process of how those cells work is the same as for silicon cells. Silicon possesses properties of a metal and an insulator. Atoms in a metal have loosely bound electrons that will readily flow when voltage or an "electrical pressure" is applied. Atoms in insulators have tightly bound electrons that will not flow even if a strong electric voltage is applied. Atoms in a semiconductor bind their electrons significantly more tightly than metals, but somewhat more loosely than insulators. This conductivity can be altered by a factor of thousands by injecting small amounts of “dopants,” (contaminants) into the make up of the semiconductor. The two elements normally used to "dope" silicon are phosphorous and boron.
The Internal Electrostatic Field
Silicon atoms possess four outer electrons, phosphorous atoms have five, and boron atoms have three. Solar roof tiles are primarily composed of silicon, but some boron atoms are present within the cell, and a very thin layer of phosphorous-treated silicon is created at the forward surface of the cell. Some of the extra outer electrons from the phosphorous-treated layer cross over and fill the holes in the boron-treated layer. This essential displacement of electrons creates an electrostatic field under the front surface of the solar roof tiles. This fixed electric field can never happen in a metal, as the electrical imbalance would immediately disappear. Because silicon atoms hold their electrons tightly, the imbalance is maintained in the silicon crystal structure. This electrostatic field makes the solar roof tiles work.
Converting Sunlight to Electricity
At the elemental level, sunlight is comprised of energy particles - photons - that are emitted from the sun and which interact with the solar roof tiles. As photons strike a silicon atom, they ionize the atoms by transferring its energy to an outer electron, causing it to break free of the atom. The energy of the photon is converted into electron movement energy called electric current. Another reason to use silicon in solar roof tiles is because the energy needed to ionize a silicon electron equals the typical energy of photons being emitted by our sun. If the photons had less energy than they do (if our solar spectrum were more red or infrared), they would not have enough energy to free the electrons, and if the photons had more energy than they do (if our solar spectrum were more blue or ultraviolet), the energy beyond that necessary to free the electron would be lost and wasted. Additional solar power information follows below.
Cell to Cell ... To You
The internal electrostatic field pushes free electrons to the forefront of the cell. They lose part of their energy traveling through the field, but end up with about one-half volt of potential. This is the voltage of the solar roof tile. One-half volt is not much, so a typical solar roof tile array is made of many solar roof tiles connected front-to-back in series. Electrons flow along the surface of a solar roof tile and into thin, conductive gridlines that cover the entire cell surface. In a good conductor like silver, the electric current flows easily into flat tin-coated copper ribbons soldered to the front of the tile, and into the back of the next solar roof tile. As the current flows through each solar roof tile, it is energized by the photons striking and entering each tile, gaining about one-half volt in each cell. Once the electric current has passed through the entire solar roof tile module, usually 36 cells in total, it has gained about 36 x 0.5 volts; or 18 volts. If more voltage is needed, for instance, to charge a 48 volt nominal battery bank or operate a power inverter at 60 volts-solar roof tile modules are also connected in a series to make a solar roof tiles array suitable for the task. The solar electric current flows through the inverter or battery bank, and yields its energy to the electric loads of the items connected to the local grid. The electrons will not disappear; they will just lose their energy (voltage). The current flows constantly back through return cables to the original solar array and solar roof cells. The "spent" electrons are channeled back into the silicon to be re-engaged by more photons from our sun. This process will continue indefinitely; as long as there is an indefinite flow of photons. On an overcast day, the intensity of the photon flow is reduced, and the amount of current flowing from the cells, and the entire array, is reduced proportionally. When full sunlight returns, the flow of electric current rises back to optimum levels. As darkness falls, the current is reduced until there is no electric current flow from the solar roof tiles array at all. As the sun rises the next morning, the process begins again automatically. Discover more solar power information on the next page.
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