Solar power & solar panels
Photovoltaic (PV) – The phenomenon by which light is converted to electricity.
Irradiance – The amount of sunlight. For home solar systems, the greater the irradiance, the more solar power is produced.
Solar Panel / Solar Module – Solar panels, also known as solar modules, are made by connecting a series of solar cells and then laminating them between a transparent cover (usually glass) and a weatherproof back cover (typically a film called a backsheet). Solar panels which use more efficient solar cells tend to be more expensive than those which use less efficient solar cells.
Solar Cells – Solar cells are made of semiconductor materials that are able to absorb light and convert it to electricity. Most solar cells are made of crystalline silicon (the same stuff that computer chips are made of), but even within the crystalline silicon, there are dozens of different variations. Some variations of solar cells are more efficient, meaning that they convert a greater percentage of sunlight into electricity. Others have better performance characteristics in different conditions (high temperatures for example – see Solar Panel Temperature Coefficient below). And some degrade less than others over time (see Solar Panel Degradation below).
Solar Panel Efficiency – Solar panel efficiency measures the percentage of sunlight that is converted to electricity. Most residential solar panels convert 18 percent to 22 percent of sunlight into electricity.
Standard Test Conditions (STC) – To maintain a level playing field, solar panels are tested and rated at STC which specifies the intensity of light, the color spectrum of the light, and the solar panel temperature. All voltage, current, and power (from which efficiency is derived) ratings of a solar panel are based on STC unless otherwise noted. It is important to understand that in the real world, solar panels almost never operate at STC. So STC ratings, while helpful in comparing solar panels, should not be confused with real world performance of solar panels under different temperature and lighting conditions.
Solar Panel Temperature Coefficient – The ability of solar cells to generate power also degrades inversely with temperature. So the hotter a solar cell is, the less power it will produce. Temperature coefficients, measured in percentage per degree celsius, tell you how much less energy solar cells and solar panels will produce as the temperature increases.
Solar Panel Degradation – The ability of solar cells, and thus solar panels, to generate power degrades over time. You’ll most likely come across solar panel degradation when reviewing solar panel warranties. Most solar panels are warranted for their power to degrade less than one percent annually over their 25 year lifetime.
Solar Panel Backsheet – Solar panel backsheets are weatherproof polymer films that sit below the solar cells and, when laminated into a solar panel, keep moisture from reaching the solar cells. While solar panel backsheets are critical for protecting the solar cells, you’ll more likely notice them from an aesthetic viewpoint since you can see the backsheet through gaps between solar cells. White backsheets reflect more light back into the cell and keep the panels cooler, improving performance when compared to black backsheets. But white backsheets also create a less homogenous aesthetic with black solar cells and strips of white in between them.
Solar Roofing – True to its name, solar roofing is solar that also functions as roofing. Despite the recent increase in awareness of solar roofing as an alternative to traditional solar panels, solar roofing products have been around for 15-20 years. Even though the low profile of solar roofing products leads to a better aesthetic, solar roofing isn’t widespread yet since it is typically more expensive than traditional solar panels. You can read more about solar roofing here.
Solar Shingles – Solar shingles are a form of solar roofing. In certain cases, they integrate with a surrounding traditional asphalt shingle roof so you can put your solar shingles in the sunniest locations and use lower-cost asphalt shingles for the rest of the roof. In some instances, the term solar shingles is used more generically to refer to any type of solar roofing.
Solar Tiles – Solar tiles are a form of solar roofing. In certain cases, they integrate with a surrounding traditional tile roof so you can put your solar tiles in the sunniest locations and use lower-cost traditional tiles for the rest of the roof. In some instances, the term solar tiles is used more generically to refer to any kind of solar roofing.
Solar Thermal – The conversion of light to heat which is then used (typically) to heat a fluid. Solar thermal panels absorb heat, which is then transferred to a fluid circulating within the panel. That fluid is used to heat water. Common examples of solar thermal applications include domestic hot water or pool heating.