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-P -

Parallel Connection
A way of joining two or more electricity-producing devices (i.e., PV cells or modules) by connecting positive leads together and negative leads together; such a configuration increases the current.

Peak Load; Peak Demand
The maximum load, or usage, of electrical power occurring in a given period of time, typically a day.

Peak/Rated kWac
The ratio of the peak kWac recorded divided by the the system's rated kWac. An indicator of system performance, as systems can generally be expected to operate near their peak at some point during. Low values do not always indicate a problem, as they may be due to poor seasonal sunlight conditions (e.g. near-horizontal arrays in northern latitudes during winter).

Photovoltaic (PV)
Literally, "light" (photo) and "electricity" (voltaic). The class of equipment used to generate electricity directly from sunlight.

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 a common support or mounting. In smaller systems, an array can consist of two modules plus a support structure or mounting.

Photovoltaic (PV) Cell
A device that converts light directly into electricity. The basic building block of a PV system . Individual PV cells are wired together in series and parallel to make modules.

Photovoltaic (PV) Efficiency
The ratio of electric power produced by a cell at any instant to the power of the sunlight striking the cell. This is typically about 9% to 14% for commercially available cells.

Photovoltaic (PV) Module
A number of PV cells electrically interconnected (in either series or parallel) and mounted together, usually in a sealed unit of convenient size to make shipping, handling and assembly into arrays easier.

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.

Photovoltaic (PV) System
A complete set of components for converting sunlight into electricity by the PV process, including the array and balance of system components.

Plane of Array
Refers to the orientation of a sensor - usually a pyranometer - to the same azimuth and tilt as a PV array in order to accurately measure the solar radiation actually available to the array.

Polycrystalline
See 'Multi-crystalline.'

Potential
The difference in electrical potential between two points in an electric circuit; measured in volts and expressed as the voltage (V). The relationship between power, current and voltage is expressed in the Power Equation, P=IV. The relationship between voltage, current, and resistance is expressed in Ohm's Law, V=IR.

Power
The rate at which energy is produced, typically expressed in watts (W), kilowatts (kW), or megawatts (MW). The relationship between power, current and voltage is expressed in the Power Equation, P=IV.

Power Equation (P=IV)
The equation expressing the relationship between power (P, in watts), current (I, in amps), and voltage (V, in volts). For example, a 20 amp breaker on a 110 volt circuit is designed to trip when loads on the circuit exceed 2,200 watts (2,200 watts = 20 amps * 110 volts).

PV
Abbreviation for photovoltaic(s).

Pyranometer
A sensor that measures solar radiation.