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.
Parallel line-commutated inverter
Inverter which can commutate the direct current generated by a PV array into 50 Hz 220 V o 380 V three-phase alternating current, in order to put on directly into a low voltage local grid.
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
The maximum load demand on a system.
Peak power [Wp]
It's the maximum power produced by a PV device in standard operative conditions (radiance 100 W/m˛ and temperature 25 °C).
Peak Watt [Wp]
The amount of power a photovoltaic module will produce at standard test conditions (normally 1000 W/m2 and 25° cell temperature).
Performance ratio
Ratio of the final annual (monthly, daily) yield to the reference annual (monthly, daily) yield, where the reference annual (monthly, daily) yield is the theoretically annual (monthly, daily) available energy per kilowatt of installed power.
Photon
A particle of light that acts as an individual unit of energy. Its energy depends on wavelength.
Photovoltaic
Term composed by “photo” (from the Greek “light”) and “voltaic” (from the name of scientist Alessandro Volta, one of the first to study electrical phenomena and inventor of the battery).
Photovoltaic array
Any number of Photovoltaic modules connected together electrically to provide a single electrical output. An array is a mechanically integrated assembly of modules or panels together with support structure (including foundation and other components, as required) to form a free-standing field installed unit that produces DC power.
Photovoltaic cell
Semiconductor device converting solar radiation into electricity: it is the smallest unity for the generation of PV energy.
Photovoltaic conversion
According to this phenomenon, the incident light on a solid-state electronic device (photovoltaic cell) produces electric energy.
Photovoltaic device
PV cell, module, panel, string or array.
Photovoltaic generator
Electric generator made of one or more photovoltaic modules, panels or strings.
Photovoltaic module
A group of PV cells connected together and sealed with an encapsulant, on the front with glass and on the back with glass and/or plastic material. The external edge can be protected by a frame of anodized aluminium.
Photovoltaic panel
Electrical device consisting of a large array of connected PV modules.
Photovoltaic system
Installation of PV modules and other components designed to provide electric power from the conversion of solar energy.
Polycrystalline silicon
Silicon having more than one crystal.
Power [W]
The rate of transfer or absorption of energy per unit time in a system. It's the product of the voltage applied to the circuit ends and the current flowing through it. It is measured in W = J/s.
Multiples of W are:
Kilowatt: kW = 1.000 W
Megawatt: MW = 1.000.000 W
Gigawatt: GW = 1.000.000.000 W
Terawatt: TW = 1.000.000.000.000 W
Protection board and B.T. Interface
Board for the parallel-connection of the plant to the power-grid. It's used to connect in parallel all the inverters; it's provided with magnetothermical protections on the entries and exits of each leg and with protections against induced overvoltages. The general parallel switch of the system is placed in the same board.
P-type silicon
Silicon having a crystalline structure containing impurities with positive charge.
PV
Abbreviation for Photovoltaic(s).
Pyranometer
An instrument for measuring global solar irradiance. It can be used to measure the irradiance inciding on both horizontal and inclined surfaces; in this last case, irradiance reflected by the ground will be measured too.
Thermopile Pyranometer: it is provided with an amount of series-connected thermocouples, producing an output voltage proportional to the incident solar irradiance.
Photovoltaic Effect Pyranometer: it is provided with a PV device of mono or polycrystalline silicon, producing an output voltage proportional to the intensity of the incident solar irradiance.
Pyroheliometer
An instrument used for measuring direct beam solar irradiance. Uses an aperture of 5.7° to transcribe the solar disc.
