How Photovoltaic Cells Generate Electricty
First some history – Photovoltaic comes from the Greek ph?s meaning “light”, and “voltaic”, meaning electric, from Volta, an Italian physicist after whom a unit of electro-motive force, the volt, is named.
This is how they work:
- Photovoltaic (PV) cells are comprised of 2 semi-conductor layers that are usually made of silicon. One layer has a positive charge and the other negative.
- When a PV cell is exposed to sunlight the photons (packets of solar energy) are absorbed by the semiconducting materials. At this point, electrons on the negatively charged semi-conductor layer are knocked loose from their atoms.
- These freed electron then move towards the positively-charged layer and when connected to an external load the electrons flow along the circuit thus creating direct current electricity.
- Each cell can produce about 1-2watts.
- The cells themselves are packaged in a weatherproof package called a solar module (or panel) and each module is made up of approximately 10 cells.
- Modules can then we wired together and can be connected to up to several thousand other modules, which is called an array.
- Once an array of modules in installed on your roof they will continue to generate clean renewable energy for a good 25 years.