Basic Solar Terms

albedo – ratio of light reflected from a surface.

alternating current (AC) – an electric current that reverses direction at regular intervals.

altitude – height of the sun above the horizon.

ampere (amp) – unit of electric current (refers to flow of current); one ampere corresponds to a certain number of electrons passing a fixed point each second.

array – photovoltaic modules connected together to provide a single electrical output.

azimuth – horizontal angle measured clockwise in degrees from a reference direction, usually the north or south point of the horizon, to the point on the horizon intersected by the object’s line of altitude.

cell – basic unit of a photovoltaic panel.

diffuse insolation – solar radiance that is scattered or reflected by atmospheric components, such as clouds, dust, etc.

direct current (DC) – an electric current in which electrons flow in one direction only.

direct insolation – solar radiance that directly hits the earth’s surface.

electrical efficiency – useful power output divided by the total electrical power consumed.

electric circuit – complete path of an electric current, including the generating apparatus, intervening resistors, or capacitors.

electric current – rate of flow of electric charge, measured in amperes.

electrical grid – interconnected network for distributing electricity.

energy – any source of usable power, as fossil fuel, electricity, or solar radiation.

gigawatt (GW) – 1,000,000,000 watts.

insolation – measure of solar radiation energy received on a given surface area in a given time.

inverter – device that converts DC electricity into AC electricity.

junction box – protected enclosure for electrical wiring.

kilowatt (kW) – 1,000 watts.

kilowatt-hour (kWh) – measure of kilowatt production of power in kilowatts and time in hours.

load (noun) – (1) the power consumed on an electrical circuit. (2) a power-absorbing device, such as a blender, light bulb, etc.

load (verb) – to add a power-absorbing device to an electrical circuit .

megawatt (MW) – 1,000,000 watts.

module – interconnected assembly of solar cells; also called a panel.

monocrystalline – single silicon crystal; monocrystalline panels are made from one large, single silicon crystal making it rated the most efficient solar technology available.

ohm – unit of electrical resistance.

photovoltaic (PV) – technology and research that relates to the application of solar cells for energy by converting radiant energy directly to electricity.

photovoltaic efficiency – the ratio of power produced by a solar cell at any instant to the power of radiant energy striking the cell; certain factors such as temperature can cause the efficiency rate to vary during the day.

photovoltaic system – a system which uses solar cells to convert light into electricity; consists of multiple components, including solar cells, mechanical and electrical connections and mountings and means of regulating and/or modifying the electrical output.

polycrystalline cell – solar cells produced from processed liquid silicon; when solidified, multiple silicon crystals are formed. Less efficient than monocrystalline cells.

radiance – light from the sun; also called solar radiance.

remote system – photovoltaic system not connected to the utility grid.

silicon – a chemical element from which semiconductors are made.

solar – (1) of or pertaining to the sun. (2) utilizing, operated by, or depending on solar energy. (3) manufacturing or providing solar power.

solar constant – the average density of solar radiation measured outside Earth’s atmosphere and at Earth’s mean distance from the sun, equal to 0.140 watt per square centimeter.

solar energy – energy derived from the sun in the form of solar radiation.

solar power – energy from the sun that is converted into thermal or electrical energy.

solar spectrum – distribution of energy emitted by the sun arranged in order of wavelengths.

solar thermal – method of harnessing solar energy for thermal energy (heat).

thin film – a thin layer of semiconductor material, such as amorphous silicon, which is deposited directly onto a plate of glass. Least efficient of all solar cells.

tracking array – a solar array that follows the path of the sun to maximize the solar radiation incident on the photovoltaic surface.

transformer – a device used to transfer electrical energy from one circuit to another; with an alternating current, a transformer will either raise or lower the voltage as it makes the transfer.

volt (V) – standard unit of voltage; one volt produces one ampere of current when acting a resistance of one ohm.

voltage – potential energy that makes the electrical current flow in a circuit by pushing the electrons around (pressure).

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.