absorbers--Dark-colored objects that soak up heat in thermal solar power collectors used to produce heat energy.
active solar heater--A solar water or space-heating system that moves heated air or water using pumps or fans.
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.
ampere-hour (Ah) --Quantity of electricity or measure of charge. How many amps of flow or which can be provided over a one hour period. Deep cycle batteries used in solar power systems are rated in Ah (amp-hour).
cell--The basic unit of a photovoltaic panel or battery.
deep discharge--Discharging a battery to 20-percent or less of its full charge.
diffuse insolation--Sunlight received indirectly as a result of scattering due to clouds, fog, haze, dust, or other obstructions in the atmosphere. Opposite of direct insolation.
direct current (dc) --Electric current in which electrons flow in one direction only. Opposite of alternating current.
direct insolation--Sunlight falling directly upon a collector. Opposite of diffuse insolation.
discharge rate--The rate, usually expressed in amperes or time, at which electrical current is taken from the battery.
electric circuit--Path followed by electrons from a power source (generator or battery) through an external line (including devices that use the electricity) and returning through another line to the source.
electric current--A flow of electrons; electricity, amps.
electrolyte--A liquid conductor of electricity. In batteries, usualy H2SO4, sulfuric acid, but may be any number of things. Seawater is the mostcommon electrolyte in the world - and by suspending a zinc and a steel sheet in it, you can get a little electricity.
energy--The ability to do work. Stored energy becomes working energy when we use it.
energy payback time--The time required for any energy producing system or device to produce as much energy as was required in its manufacture. For solar electric panels, this is about 16-20 months.
hybrid system--A PV system that includes other sources of electricity generation, such as wind or fossil fuel generators.
incident light--Light that shines onto the face of a solar cell or module.
junction diode--A semiconductor device with a junction and a built-in potential that passes current better in one direction than the other. All solar cells are junction diodes.
kilowatt (kW) --1000 watts.
kilowatt-hour (kWh) --One thousand watts acting over a period of 1 hour. The kWh is a unit of energy. 1 kWh=3600 kJ.
load--Anything in an electrical circuit that, when the circuit is turned on, draws power from that circuit.
ohm--The unit of resistance to the flow of an electric current.
one-axis tracking--A system capable of rotating about one axis.
open-circuit voltage (Voc) --The maximum possible voltage across a photovoltaic cell or module; the voltage across the cell in sunlight when no current is flowing.
passive solar home--A house that uses a room or another part of the building as a solar collector, as opposed to active solar, such as PV.
peak load; peak demand--The maximum load, or usage, of electrical power occurring in a given period of time, typically a day.
photon--A particle of light that acts as an individual unit of energy.
photovoltaic (PV) --Pertaining to the direct conversion of light into electricity.
photovoltaic (PV) cell--The smallest semiconductor element within a PV module to perform the immediate conversion of light into electrical energy (dc voltage and current).
photovoltaic (PV) system--A complete set of components for converting sunlight into electricity by the photovoltaic process, including the array and balance of system components.
photovoltaic-thermal (PV/T) system--A photovoltaic system that, in addition to converting sunlight into electricity, collects the residual heat energy and delivers both heat and electricity in usable form. Also called a total energy system.
pyronometer--An instrument for measuring total hemispherical solar irradiance on a flat surface, or "global" irradiance; thermopile sensors have been generally identified as pyranometers, however, silicon sensors are also referred to as pyranometers.
solar constant--The strength of sunlight; 1353 watts per square meter in space and about 1000 watts per square meter at sea level at the equator at solar noon.
solar energy--Energy from the sun. The heat that builds up in your car when it is parked in the sun is an example of solar energy.
solar spectrum--The total distribution of electromagnetic radiation emanating from the sun.
thermal electric--Electric energy derived from heat energy, usually by heating a working fluid, which drives a turbogenerator. See 'solar thermal electric.'
total internal reflection--The trapping of light by refraction and reflection at critical angles inside a semiconductor device so that it cannot escape the device and must eventually be absorbed by the semiconductor.
tracking array--PV array that follows the path of the sun to maximize the solar radiation incident on the PV surface. The two most common orientations are (1) one axis where the array tracks the sun east to west and (2) two-axis tracking where the array points directly at the sun at all times. Tracking arrays use both the direct and diffuse sunlight. Two-axis tracking arrays capture the maximum possible daily energy. Typically, a single axis tracker will give you 15% to 25% more power per day, and dual axis tracking will add about 5% to that- Depends somewhat on latitude and season.
two-axis tracking--A system capable of rotating independently about two axes (e.g., vertical and horizontal) and following the sun for maximum efficiency of the solar array.
utility-interactive inverter--An inverter that can function only when tied to the utility grid, and uses the prevailing line-voltage frequency on the utility line as a control parameter to ensure that the PV system's output is fully synchronized with the utility power.
VAC--Volts ac
VDC--Volts dc
Vmp--Voltage at maximum power
Voc--Open-circuit voltage
volt (V) --A unit of measure of the force, or 'push,' given the electrons in an electric circuit. One volt produces one ampere of current when acting a resistance of one ohm.
voltage at maximum power (Vmp) --The voltage at which maximum power is available from a module.
wafer--A thin sheet of semiconductor material made by mechanically sawing it from a single-crystal or multi-crystal ingot or casting.
watt (W) --The unit of electric power, or amount of work (J), done in a unit of time. One ampere of current flowing at a potential of one volt produces one watt of power.
watt-hour (Wh) --See 'Kilowatt-hour.'
waveform--The shape of the curve graphically representing the change in the ac signal voltage and current amplitude, with respect to time.
