In a photovoltaic device, the blackened material that readily absorbs photons to generate charge carriers (free electrons or holes).
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Absorptance
The ratio of solar energy absorbed by a surface to the solar energy striking it.
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Absorption Coefficient
The factor by which photons are absorbed as they travel a unit distance through a material.
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AC
see alternating current.
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AC Converter
AC converters are electronic components that convert direct current to alternating current. In solar electricity technology, they are needed in order to feed the electricity generated by cells or modules into the public grid. The AC Converter takes the output of the photovoltaic system at the Maximum Power Point.
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Acceptor
A dopant material, such as boron, which has fewer outer shell electrons than required in an otherwise balanced crystal structure, providing a hole, which can accept a free electron.
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Activated Shelf Life
The period of time, at a specified temperature, that a charged battery can be stored before its capacity falls to an unusable level.
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Activation Voltage(s)
The voltage(s) at which a charge controller will take action to protect the batteries.
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Active solar heater
A solar water or space-heating system that moves heated air or water using pumps or fans.
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Active System
A solar heating or cooling system that requires external mechanical power to move the collected heat.
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Adjustable Set Point
A feature allowing the user to adjust the voltage levels at which a charge controller will become active.
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AGM
Absorbed Glass Mat, a newer type of battery construction that uses saturated absorbent glass mats rather than gelled or liquid electrolyte. Somewhat more expensive than flooded (liquid), but offers very good reliability.
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AIC
See amperage interrupt capability.
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Air mass (sometimes called air mass ratio)
Equal to the cosine of the zenith angle-that angle from directly overhead to a line intersecting the sun. The air mass is an indication of the length of the path solar radiation travels through the atmosphere. An air mass of 1.0 means the sun is directly overhead and the radiation travels through one atmosphere (thickness).
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Air System
Solar domestic hot water systems employing air-type collectors are available. Hot air generated by these collectors is fan forced through an air-to-liquid heat exchanger with the potable water being pumped through the liquid section of the exchanger. The heated water is then circulated through the storage tank in a similar fashion to the liquid collector system. Air does not need to be protected from freezing or boiling, is non-corrosive, and is free. However, air ducts and air handling units require greater spac
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Air-Type Collector
A collector that uses air as the heat transfer fluid.
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Alternating Current
Electric current in which the direction of flow is reversed at frequent intervals.
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Alternating Current (AC)
A type of electrical current, the direction of which is reversed at regular intervals or cycles. In the United States, the standard is 120 reversals or 60 cycles per second. Electricity transmission networks use AC because voltage can be controlled with relative ease.
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Alternator
A device that produces alternating current (AC) electricity, either through a motor or other sources, such as water and wind power.
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Altitude
The angular distance from the horizon to the sun.
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AM
Airmass-The ratio of the mass of atmosphere in the actual observer-sun path to the mass that would exist if the observer was at sea level, at standard barometric pressure, and the sun was directly overhead. AM0 corresponds to the solar spectrum in outer space, and the reference spectrum for STC was defined to be AM1.5
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Ambient Temperature
The temperature of the surrounding air.
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Ammeter
A device that is used to measure current flow in an electrical circuit
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Amorphous Silicon
A thin-film, silicon photovoltaic cell having no crystalline structure. Manufactured by depositing layers of doped silicon on a substrate. See also single-crystal silicon an polycrystalline silicon.
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Amorphous Solar Cell
Solar cell made from amorphous silicon. Technology used for production is similar to the one for thin-film panels.
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Amortisation
This is the time the PV system needs to produced an equivalent amount of power to cover its initial cost. Depending on the price for electricity in a country, this period can be longer or shorter
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Amperage Interrupt Capability (AIC)
direct current fuses should be rated with a sufficient AIC to interrupt the highest possible current.
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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.
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Ampere Hour (Ah)
The quantity of electrical energy equal to the flow of current of one ampere for one hour. The term is used to quantify the energy stored in a battery.
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Ampere Hour Meter
An instrument that monitors current with time. The indication is the product of current (in amperes) and time (in hours).
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Ampere
Hour (Ah/AH)-A measure of the flow of current (in amperes) over one hour; used to measure battery capacity.
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Amp
hour (Ah)-The amount of electrical energy related to the flow of current of one ampere for one hour. Amp hours measure the amount of energy stored into a battery, commonly rated in Ah.
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Angle of Incidence
The angle that a ray of sun makes with a line perpendicular to the surface. For example, a surface that directly faces the sun has a solar angle of incidence of zero, but if the surface is parallel to the sun (for example, sunrise striking a horizontal rooftop), the angle of incidence is 90°.
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Angle of inclination
The angle of inclination is the angle between a sloping reception plane (e.g. the roof) and the horizontal plane. There are different optimal angles of inclination depending on the geographic latitude of the mounting site of a photovoltaic system.
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Annual Solar Savings
The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building.
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Anode
The positive electrode in an electrochemical cell (battery). Also, the earth ground in a cathodic protection system. Also, the positive terminal of a diode.
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Antireflection Coating
A thin coating of a material, which reduces the light reflection and increases light transmission, applied to a photovoltaic cell surface.
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Array
Any number of photovoltaic modules connected together to provide a single electrical output. Arrays are often designed to produce significant amounts of electricity.
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Array Current
The electrical current produced by a PV array when it is exposed to sunlight.
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Array Operating Voltage
The voltage produced by a photovoltaic array when exposed to sunlight and connected to a load.
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ASHRAE
Abbreviation for the American Society of Heating and Air-Conditioning Engineers.
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autonomous system
A stand-alone PV system that has no back-up generating source. May or may not include storage batteries. Most battery systems are designed for a certain minimum "days of autonomy" - which means that the batteries can supply sufficient power with no sunlight to charge the batteries. This varies from 3-5 days in the sunbelt, to 5 to 10 days elsewhere.
Auxiliary Heat The extra heat provided by a conventional heating system for periods of
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Availability
The quality or condition of a photovoltaic system being available to provide power to a load. Usually measured in hours per year. One minus availability equals downtime.
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AWG
American Wire Gauge, a standard system for designating the size of electrical wire. The higher the number, the smaller the wire. Most house wiring is #12 or 14. In most other countries, wire is specified by the size in millimeters.
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Azimuth
The angular distance between true south and the point on the horizon directly below the sun.
