Glossary
- Amorphous
- A plastic-wrap-like variant of photovoltaics. These can be directly nailed onto roofs and are often put into modules. They are less expensive and correspondingly less efficient. United Solar Ovonic (Uni-Solar) is a popular manufacturer of thin-film amorphous photovoltaics. Efficiencies are typically 5%.
- Cell
- The smallest division of crystalline photovoltaics. They are typically 4x4" square, but can be found in hexagonal, round, half-round, and other shapes as well. Cells are always quite thin and very fragile; about 30 per inch can be stacked depthwise. An approximate power output is 3A at 0.5V. Modules are made up of 36 to 144 of these cells in series. If one cell is covered, the module's power output is typically reduced to about zero, but the power from the uncovered cells can be instead used to heat the dark cell. For this reason, cells have been known to burn catastrophically if subjected to current while accepting no sunlight.
- Concentrated PV
- A method using a magnifying glass or similar apparatus to focus all of the photons from a given area onto a smaller area in order to reduce the amount of photovoltaics needed, as well as increase the photon density to aid absorption and hence boost efficiency. Concentration ratios are usually around 500 in order to make the production economically competitive with coal or nuclear power.
- Crystalline
- A regular grouping of atoms in a material structure. Silicon solar cells are typically monocrystalline or multicrystalline. Each has its own manufacturing process and associated pros and cons. More information can be found here. A crystalline cell is usually about 4x4" square and puts out around 3A at 0.5V. These are by far the most common type of photovoltaics. Efficiencies are typically 15%.
- Disconnect
- Nothing more than a switch to remove power in any direction from some unit, typically an inverter. In general, a DC disconnect isolates a renewable generating source and an inverter or battery charger when off, and an AC disconnect isolates a utility power line and an inverter when off. These switches allow the inverter to be serviced. There are too many other applications of disconnects to cover here, but the latter uses are the most important to home solar and wind installations.
- Module
- A group of photovoltaic cells covered with a sheet of glass or plastic along with an aluminum grounding rim. This is the most basic unit for solar installations. Modules are not as fragile as cells alone because of their rigid mounting structure, though they still should be handled and shipped with care. Amorphous modules are not split into cells per-se, but appear almost identical and can be used in the same way.
- Multijunction cell
- Sandwiched layers of crystalline solar cells that accept a wider range of photon frequencies, from infrared to ultraviolet, at a higher efficiency than a single-junction cell. Because of their cost, they are typically used in concentrator systems. Boeing's subsidiary Spectrolab is a manufacturer of multijunction cells. Their mass-produced C2MJ cells can reach almost 40% efficiency at a high concentration ratio.
- Net Metering
- An agreement where a homeowner is paid for surplus power sent to the utility. Much more information can be found here.
- Photovoltaics (PV)
- The field of converting light energy into electrical energy by photodiodes or similar devices. More information can be found here and here.
- Renewable energy
- A manner of converting (not creating) energy from one form to another that does not deplete the resources of the Earth in the long run, and can therefore be used indefinitely while the sun is still shining. This is also referred to as sustainability or sustainable living. Fossil fuels are not renewable resources in the manner in which they are used, because very little oil is being recreated each day.
- Tracker
- A system set up to keep photovoltaic modules pointed directly at the sun throughout the day, to enhance power output. Most tracking systems will be mounted on the ground, but some, like Ed Begley Jr.'s, will be mounted on a roof.
