Copy of `US Department of Energy - Solar power glossary`

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US Department of Energy - Solar power glossary
Category: Sciences > Solar power
Date & country: 01/06/2011, US
Words: 238


AC
see alternating current.

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.

AIC
See amperage interrupt capability.

Ambient Temperature
The temperature of the surrounding area.

Amorphous Semiconductor
A non-crystalline semiconductor material that has no long-range order.

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 Meter
An instrument that monitors current with time. The indication is the product of current (in amperes) and time (in hours).

Ampere-Hour (Ah/AH)
A measure of the flow of current (in amperes) over one hour; used to measure battery capacity.

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.

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.

Barrier Energy
The energy given up by an electron in penetrating the cell barrier; a measure of the electrostatic potential of the barrier.

Base Load
The average amount of electric power that a utility must supply in any period.

Boron (B)
The chemical element commonly used as the dopant in photovoltaic device or cell material.

Btu (British Thermal Unit)
The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit; equal to 252 calories.

Bypass Diode
A diode connected across one or more solar cells in a photovoltaic module such that the diode will conduct if the cell(s) become reverse biased. It protects these solar cells from thermal destruction in case of total or partial shading of individual solar cells while other cells are exposed to full light.

Cadmium (Cd)
A chemical element used in making certain types of solar cells and batteries.

Cadmium Telluride (CdTe)
A polycrystalline thin-film photovoltaic material.

Capacity (C)
See battery capacity.

Capacity Factor
The ratio of the average load on (or power output of) an electricity generating unit or system to the capacity rating of the unit or system over a specified period of time.

Captive Electrolyte Battery
A battery having an immobilized electrolyte (gelled or absorbed in a material).

Cathodic Protection
A method of preventing oxidation of the exposed metal in structures by imposing a small electrical voltage between the structure and the ground.

Cd
see cadmium.

CdTe
see cadmium telluride.

Cell (battery)
A single unit of an electrochemical device capable of producing direct voltage by converting chemical energy into electrical energy. A battery usually consists of several cells electrically connected together to produce higher voltages. (Sometimes the terms cell and battery are used interchangeably). Also see photovoltaic (PV) cell.

Cell Junction
The area of immediate contact between two layers (positive and negative) of a photovoltaic cell. The junction lies at the center of the cell barrier or depletion zone.

Charge
The process of adding electrical energy to a battery.

Charge Carrier
A free and mobile conduction electron or hole in a semiconductor.

Charge Controller
A component of a photovoltaic system that controls the flow of current to and from the battery to protect it from over-charge and over-discharge. The charge controller may also indicate the system operational status.

Charge Rate
The current applied to a cell or battery to restore its available capacity. This rate is commonly normalized by a charge control device with respect to the rated capacity of the cell or battery.

Cloud Enhancement
The increase in solar intensity caused by reflected irradiance from nearby clouds.

Combined Collector
A photovoltaic device or module that provides useful heat energy in addition to electricity.

Contact Resistance
The resistance between metallic contacts and the semiconductor.

Conversion Efficiency
See photovoltaic (conversion) efficiency.

Converter
A unit that converts a direct current (dc) voltage to another dc voltage.

Crystalline Silicon
A type of photovoltaic cell made from a slice of single-crystal silicon or polycrystalline silicon.

Current
See electric current.

Current at Maximum Power (Imp)
The current at which maximum power is available from a module.

Cutoff Voltage
The voltage levels (activation) at which the charge controller disconnects the photovoltaic array from the battery or the load from the battery.

Cycle
The discharge and subsequent charge of a battery.

Days of Storage
The number of consecutive days the stand-alone system will meet a defined load without solar energy input. This term is related to system availability.

DC
See direct current.

Deep Discharge
Discharging a battery to 20% or less of its full charge capacity.

Deep-Cycle Battery
A battery with large plates that can withstand many discharges to a low state-of-charge.

Dendritic Web Technique
A method for making sheets of polycrystalline silicon in which silicon dendrites are slowly withdrawn from a melt of silicon whereupon a web of silicon forms between the dendrites and solidifies as it rises from the melt and cools.

Depletion Zone
Same as cell barrier. The term derives from the fact that this microscopically thin region is depleted of charge carriers (free electrons and hole).

Design Month
The month having the combination of insolation and load that requires the maximum energy from the photovoltaic array.

Diffuse Radiation
Radiation received from the sun after reflection and scattering by the atmosphere and ground.

Diffusion Furnace
Furnace used to make junctions in semiconductors by diffusing dopant atoms into the surface of the material.

Diffusion Length
The mean distance a free electron or hole moves before recombining with another hole or electron.

Diode
An electronic device that allows current to flow in one direction only. See blocking diode and bypass diode.

Direct Beam Radiation
Radiation received by direct solar rays. Measured by a pyrheliometer with a solar aperture of 5.7

Direct Insolation
Sunlight falling directly upon a collector. Opposite of diffuse insolation.

Discharge
The withdrawal of electrical energy from a battery.

Disconnect
Switch gear used to connect or disconnect components in a photovoltaic system.

Distributed Generation
A popular term for localized or on-site power generation.

Distributed Power
Generic term for any power supply located near the point where the power is used. Opposite of central power. See stand-alone systems.

Donor Level
The level that donates conduction electrons to the system.

Dopant
A chemical element (impurity) added in small amounts to an otherwise pure semiconductor material to modify the electrical properties of the material. An n-dopant introduces more electrons. A p-dopant creates electron vacancies (holes).

Doping
The addition of dopants to a semiconductor.

Downtime
Time when the photovoltaic system cannot provide power for the load. Usually expressed in hours per year or that percentage.

Dry Cell
A cell (battery) with a captive electrolyte. A primary battery that cannot be recharged.

Duty Cycle
The ratio of active time to total time. Used to describe the operating regime of appliances or loads in photovoltaic systems.

Duty Rating
The amount of time an inverter (power conditioning unit) can produce at full rated power.

Edge-Defined Film-Fed Growth (EFG)
A method for making sheets of polycrystalline silicon for photovoltaic devices in which molten silicon is drawn upward by capillary action through a mold.

Electrode
A conductor that is brought in conducting contact with a ground.

Electrodeposition
Electrolytic process in which a metal is deposited at the cathode from a solution of its ions.

Electrolyte
A nonmetallic (liquid or solid) conductor that carries current by the movement of ions (instead of electrons) with the liberation of matter at the electrodes of an electrochemical cell.

Electron
An elementary particle of an atom with a negative electrical charge and a mass of 1/1837 of a proton; electrons surround the positively charged nucleus of an atom and determine the chemical properties of an atom. The movement of electrons in an electrical conductor constitutes an electric current.

Electron Volt (eV)
The amount of kinetic energy gained by an electron when accelerated through an electric potential difference of 1 Volt; equivalent to 1.603 x 10^-19; a unit of energy or work.

Energy Contribution Potential
Recombination occurring in the emitter region of a photovoltaic cell.

Energy Density
The ratio of available energy per pound; usually used to compare storage batteries.

Energy Levels
The energy represented by an electron in the band model of a substance.

Epitaxial Growth
The growth of one crystal on the surface of another crystal. The growth of the deposited crystal is oriented by the lattice structure of the original crystal.

Equalization
The process of restoring all cells in a battery to an equal state-of-charge. Some battery types may require a complete discharge as a part of the equalization process.

Equalization Charge
The process of mixing the electrolyte in batteries by periodically overcharging the batteries for a short time.

Equinox
The two times of the year when the sun crosses the equator and night and day are of equal length; usually occurs on March 21st (spring equinox) and September 23 (fall equinox).

Extrinsic Semiconductor
The product of doping a pure semiconductor.

Fill Factor
The ratio of a photovoltaic cell's actual power to its power if both current and voltage were at their maxima. A key characteristic in evaluating cell performance.

Fixed Tilt Array
A photovoltaic array set in at a fixed angle with respect to horizontal.

Flat-Plate Array
A photovoltaic (PV) array that consists of non-concentrating PV modules.

Flat-Plate Module
An arrangement of photovoltaic cells or material mounted on a rigid flat surface with the cells exposed freely to incoming sunlight.

Float Charge
The voltage required to counteract the self-discharge of the battery at a certain temperature.

Float Life
The number of years that a battery can keep its stated capacity when it is kept at float charge.

Frequency Regulation
This indicates the variability in the output frequency. Some loads will switch off or not operate properly if frequency variations exceed 1%.

Fresnel Lens
An optical device that focuses light like a magnifying glass; concentric rings are faced at slightly different angles so that light falling on any ring is focused to the same point.

Ga
See gallium.

GaAs
See gallium arsenide.

Gassing
The evolution of gas from one or more of the electrodes in the cells of a battery. Gassing commonly results from local action self-discharge or from the electrolysis of water in the electrolyte during charging.

Gassing Current
The portion of charge current that goes into electrolytical production of hydrogen and oxygen from the electrolytic liquid. This current increases with increasing voltage and temperature.

Gel-Type Battery
Lead-acid battery in which the electrolyte is composed of a silica gel matrix.

Grid
See electrical grid.

Grid Lines
Metallic contacts fused to the surface of the solar cell to provide a low resistance path for electrons to flow out to the cell interconnect wires.