Glossary

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Termsort icon Definition
a-Si/µc-Si Dual amorphous silicon / micro-crystalline silicon absorber (also referred to as tandem, micromorph). Micro and nano-crystalline are interchangeable.
a:Si Amorphous silicon. Silicon material having no definite or regular crystal structure.
Absorber Layers used to absorb light.
Acreage Acreage that is taken up by the PV system.
Activated shelf life The time it takes for the capacity of a charged battery to fall to an unusable level when stored at a specified temperature.
Activation voltage The voltage at which the controller will operate to protect the batteries.
AGM (Adsorbed Glass Mat) A type of battery construction that uses saturated adsorbant glass mats rather than gelled or liquid electrolyte. AGM batteries are typically more expensive than flooded (liquid), but offer enhanced reliability.
Air mass The air mass relates to the path length of solar radiation through the atmosphere. An air mass of 1.0 means the sun is directly overhead and the radiation travels through one atmosphere thickness. Approximately equal to the secant of the zenith angle, i.e. the angle from directly overhead to a line to the sun.
Alternating current (AC) Electrical current that continually reverses direction of flow. The frequency at which it reverses is measured in cycles-per-second, or Hertz (Hz). The magnitude of the current itself is measured in amps (A).
Alternator A device for producing Alternating Current (AC) electricity. Usually driven by a motor, but can also be driven by other means, including water and wind power.
Ambient temperature The temperature of the surroundings.
Ammeter A device used for measuring current flow at any point in an electrical circuit.
Amorphous silicon A thin-film solar PV cell material which has a glassy rather than crystalline structure. Made by depositing layers of doped silicon on a substrate normally using plasma-enhanced chemical vapor deposition of silane.
Amp hour The quantity of electrical energy corresponding to the flow of current of one ampere for one hour. The term is used to quantify the energy stored in a battery. Most batteries are rated in Ah.
Ampere (A) or amp The unit for the electric current; the flow of electrons. One amp is 1 coulomb passing in one second. One amp is produced by an electric force of 1 volt acting across a resistance of 1 ohm.
Anemometer A device used to measure wind speed.
Angle of incidence Angle between the normal to a surface and the direction of incident radiation; applies to the aperture plane of a solar panel. Only minor reductions in power output within plus/minus 15 degrees.
Anode The positive electrode in a battery. The positive terminal of a diode.
Anti-reflection coating A thin coating of a material with a specific refractive index applied to a cell to reduce the reflection of light.
APCVD Atmospheric pressure chemical vapor deposition.
Array A number of solar modules connected together in a single structure.
Array current The electrical current output of a PV array when exposed to sunlight.
Array operating voltage The voltage output of a PV array when exposed to sunlight and feeding a load.
ASP Average selling price.
Autonomous system A PV system that operates without any other energy generating source.
Availability The quality or condition of a PV system that is available to provide power to a load. Usually measured in hours per year.
AWG American Wire Gauge
Azimuth The angle between the north direction and the projection of the surface normal into the horizontal plane; measured clockwise from north. As applied to the PV array, 180 degree azimuth means the array faces due south.
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