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 FAQ Glossary
 Absorber- In a photovoltaic device, the material that readily absorbs photons to
generate charge carriers (free electrons or holes).
AC - alternating current.
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.
Activation Voltage(s) - The voltage(s) at which a charge controller will take action to protect the
batteries.
Adjustable Set Point - A feature allowing the user to adjust the voltage levels at which a charge
controller will become active.
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.
Acceptor - A do pant 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.
AIC - See amperage interrupt capability.
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).
Ambient Temperature - The temperature of the surrounding area.
Amorphous Semiconductor - A non-crystalline semiconductor material that has no long-range order.
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 a polycrystalline silicon.
Amperage Interrupt Capability (AIC) - direct current fuses should be rated with a sufficient AIC to
interrupt the highest possible current.
Ampere (amp) - A unit of electrical current or rate of flow of electrons. One volt across one ohm of
resistance causes a current flow of one ampere.
Ampere-Hour (Ah/AH) - A measure of the flow of current (in amperes) over one hour; used to measure
battery capacity.
Ampere Hour Meter- An instrument that monitors current with time. The indication is the product of current (in amperes) and time (in hours).
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 .
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.
Anode - The positive electrode in an electrochemical cell (battery). Also, the earth or ground in a cathode
protection system. Also, the positive terminal of a diode.
Antireflection Coating - A thin coating of a material applied to a solar cell surface that reduces the light
reflection and increases light transmission.
Array - see photovoltaic (PV) array.
Array Current - The electrical current produced by a photovoltaic array when it is exposed to sunlight.
Array Operating Voltage - The voltage produced by a photovoltaic array when exposed to sunlight and
connected to a load.
Autonomous System - See stand-alone system. 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.Azimuth Angle - The angle between true south and the point on the horizon
directly below the Sun.
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