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.
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.
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.
array — See photovoltaic (PV) array.
azimuth angle — The angle between true south and the point on the horizon directly below the sun.
Community Solar Garden (CSG) — Refers to a centrally-located solar photovoltaic (PV) system that provides electricity to participating subscribers.
conductor — The material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line.
current — See electric current.
direct current (DC) — A type of electricity transmission and distribution by which electricity flows in one direction through the conductor, usually relatively low voltage and high current. To be used for typical 120 volt or 220-volt household appliances, DC must be converted to alternating current, its opposite.
distributed generation — DG refers to electricity that is produced at or near the point where it is used. A distributed solar energy generation system can be located on rooftops or can be ground mounted, and is typically connected to the local utility.
distributed power — Generic term for any power supply located near the point where the power is used. Opposite of central power.
distributed systems — Systems that are installed at or near the location where the electricity is used, as opposed to central systems that supply electricity to grids. A residential photovoltaic system is a distributed system.
electric current — The flow of electrical energy (electricity) in a conductor, measured in amperes.
electrical grid — An integrated system of electricity distribution, usually covering a large area.
energy audit — A survey that shows how much energy used in a home, which helps find ways to use less energy.
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.
grid — An integrated system of electricity distribution, usually covering a large area.
grid-connected system — A solar electric or photovoltaic (PV) system in which the PV array acts like a central generating plant, supplying power to the grid.
grid-interactive system — Same as grid-connected system.
kilowatt (kW) — A standard unit of electrical power equal to 1000 watts, or to the energy consumption at a rate of 1000 joules per second.
kilowatt-hour (kWh) — 1,000 thousand watts acting over a period of one hour. The kWh is a unit of energy. 1 kWh=3600 kJ.
life — The period during which a system is capable of operating above a specified performance level.
life-cycle cost — The estimated cost of owning and operating a photovoltaic system for the period of its useful life.
load — The demand on an energy producing system; the energy consumption or requirement of a piece or group of equipment. Usually expressed in terms of amperes or watts in reference to electricity.
megawatt (MW) — 1,000 kilowatts, or 1 million watts; standard measure of electric power plant generating capacity.
megawatt-hour — 1,000 kilowatt-hours or 1 million watt-hours.
module — See photovoltaic (PV) module.
orientation — Placement with respect to the cardinal directions, N, S, E, W; azimuth is the measure of orientation from north.
panel — See photovoltaic (PV) panel.
photovoltaic (PV) array — An interconnected system of PV modules that function as a single electricity-producing unit. The modules are assembled as a discrete structure, with common support or mounting. In smaller systems, an array can consist of a single module.
photovoltaic (PV) cell — The smallest semiconductor element within a PV module to perform the immediate conversion of light into electrical energy (direct current voltage and current). Also called a solar cell.
photovoltaic (PV) module — The smallest environmentally protected, essentially planar assembly of solar cells and ancillary parts, such as interconnections, terminals, (and protective devices such as diodes) intended to generate direct current power under unconcentrated sunlight. The structural (load carrying) member of a module can either be the top layer (superstrate) or the back layer (substrate).photovoltaic (PV) panel — often used interchangeably with PV module (especially in one-module systems), but more accurately used to refer to a physically connected collection of modules (i.e., a laminate string of modules used to achieve a required voltage and current).
photovoltaic (PV) panel — often used interchangeably with PV module (especially in one-module systems), but more accurately used to refer to a physically connected collection of modules (i.e., a laminate string of modules used to achieve a required 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 or solar thermal system.
power — The amount of electrical energy available for doing work, measured in horsepower, Watts, or Btu per hour.
PV — See photovoltaic(s).
solar cell — See photovoltaic (PV) cell.
solar energy — Electromagnetic energy transmitted from the sun (solar radiation). The amount that reaches the earth is equal to one billionth of total solar energy generated, or the equivalent of about 420 trillion kilowatt-hours.
solar panel — See photovoltaic (PV) panel.
tilt angle — The angle at which a photovoltaic array is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection.
tracking array — A photovoltaic (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.
volt (V) — A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.
voltage — The amount of electromotive force, measured in volts, that exists between two points.
watt — The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals 1/746 horsepower, or one joule per second. It is the product of voltage and current(amperage).