Packing Factor — The ratio of array area to actual land area or building envelope area for a system; or, the ratio of
total solar cell area to the total module area, for a module.
Panel — See photovoltaic (PV) panel.
Parallel Connection — A way of joining solar cells or photovoltaic modules by connecting positive leads together and
negative leads together; such a configuration increases the current, but not the voltage.
Passivation — A chemical reaction that eliminates the detrimental effect of electrically reactive atoms on a solar
cell's surface.
Peak Demand/Load — The maximum energy demand or load in a specified time period.
Peak Power Current — Amperes produced by a photovoltaic module or array operating at the voltage of the I-V
curve that will produce maximum power from the module.
Peak Power Point — Operating point of the I-V (current-voltage) curve for a solar cell or photovoltaic module where
the product of the current value times the voltage value is a maximum.
Peak Power Tracking — see maximum power tracking.
Peak Sun Hours — The equivalent number of hours per day when solar irradiance averages 1,000 w/m2. For
example, six peak sun hours means that the energy received during total daylight hours equals the energy that
would have been received had the irradiance for six hours been 1,000 w/m2.
Peak Watt — A unit used to rate the performance of solar cells, modules, or arrays; the maximum nominal output of
a photovoltaic device, in watts (Wp) under standardized test conditions, usually 1,000 watts per square meter of
sunlight with other conditions, such as temperature specified.
Phosphorous (P) — A chemical element used as a dopant in making n-type semiconductor layers.
Photocurrent — An electric current induced by radiant energy.
Photoelectric Cell — A device for measuring light intensity that works by converting light falling on, or reach it, to
electricity, and then measuring the current; used in photometers.
Photoelectrochemical Cell — A type of photovoltaic device in which the electricity induced in the cell is used
immediately within the cell to produce a chemical, such as hydrogen, which can then be withdrawn for use.
Photon — A particle of light that acts as an individual unit of energy.
Photovoltaic(s) (PV) — Pertaining to the direct conversion of light into electricity.
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) Conversion Efficiency — The ratio of the electric power produced by a photovoltaic device to the
power of the sunlight incident on the device.
Photovoltaic (PV) Device — A solid-state electrical device that converts light directly into direct current electricity of
voltage-current characteristics that are a function of the characteristics of the light source and the materials in and
design of the device. Solar photovoltaic devices are made of various semiconductor materials including silicon,
cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multicrystalline, or amorphous
forms.
Photovoltaic (PV) Effect — The phenomenon that occurs when photons, the "particles" in a beam of light, knock
electrons loose from the atoms they strike. When this property of light is combined with the properties of
semiconductors, electrons flow in one direction across a junction, setting up a voltage. With the addition of circuitry,
current will flow and electric power will be available.
Photovoltaic (PV) Generator — The total of all PV strings of a PV power supply system, which are electrically
interconnected.
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) 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.
Physical Vapor Deposition — A method of depositing thin semiconductor photovoltaic films. With this method,
physical processes, such as thermal evaporation or bombardment of ions, are used to deposit elemental
semiconductor material on a substrate.
P-I-N — A semiconductor photovoltaic (PV) device structure that layers an intrinsic semiconductor between a p-type
semiconductor and an n-type semiconductor; this structure is most often used with amorphous silicon PV devices.
Plates — A metal plate, usually lead or lead compound, immersed in the electrolyte in a battery.
P/N — A semiconductor photovoltaic device structure in which the junction is formed between a p-type layer and an
n-type layer.
Pocket Plate — A plate for a battery in which active materials are held in a perforated metal pocket.
Point-Contact Cell — A high efficiency silicon photovoltaic concentrator cell that employs light trapping techniques
and point-diffused contacts on the rear surface for current collection.
Polycrystalline — See Multicrystalline.
Polycrystalline Silicon — A material used to make photovoltaic cells, which consist of many crystals unlike single-
crystal silicon.
Power Conditioning — The process of modifying the characteristics of electrical power (for e.g., inverting direct
current to alternating current).
Power Conditioning Equipment — Electrical equipment, or power electronics, used to convert power from a
photovoltaic array into a form suitable for subsequent use. A collective term for inverter, converter, battery charge
regulator, and blocking diode.
Power Conversion Efficiency — The ratio of output power to input power of the inverter.
Power Density — The ratio of the power available from a battery to its mass (W/kg) or volume (W/l).
Power Factor (PF) — The ratio of actual power being used in a circuit, expressed in watts or kilowatts, to the power
that is apparently being drawn from a power source, expressed in volt-amperes or kilovolt-amperes.
Primary Battery — A battery whose initial capacity cannot be restored by charging.
Projected Area — The net south-facing glazing area projected on a vertical plane.
P-Type Semiconductor — A semiconductor in which holes carry the current; produced by doping an intrinsic
semiconductor with an electron acceptor impurity (e.g., boron in silicon).
Pulse-Width-Modulated (PWM) Wave Inverter — A type of power inverter that produce a high quality (nearly
sinusoidal) voltage, at minimum current harmonics.
PV — See photovoltaic(s).
Pyranometer — An instrument used for measuring global solar irradiance.
Pyrheliometer — An instrument used for measuring direct beam solar irradiance. Uses an aperture of 5.7° to
transcribe the solar disc.
Q
Quad — One quadrillion Btu (1,000,000,000,000,000 Btu).
Qualification Test — A procedure applied to a selected set of photovoltaic modules involving the application of
defined electrical, mechanical, or thermal stress in a prescribed manner and amount. Test results are subject to a
list of defined requirements.
R
Rated Battery Capacity — The term used by battery manufacturers to indicate the maximum amount of energy that
can be withdrawn from a battery under specified discharge rate and temperature. See battery capacity.
Rated Module Current (A) — The current output of a photovoltaic module measured at standard test conditions of
1,000 w/m2 and 25�C cell temperature.
Rated Power — Rated power of the inverter. However, some units can not produce rated power continuously. See
duty rating.
Reactive Power — The sine of the phase angle between the current and voltage waveforms in an alternating current
system. See power factor.
Recombination — The action of a free electron falling back into a hole. Recombination processes are either
radiative, where the energy of recombination results in the emission of a photon, or nonradiative, where the energy
of recombination is given to a second electron which then relaxes back to its original energy by emitting phonons.
Recombination can take place in the bulk of the semiconductor, at the surfaces, in the junction region, at defects, or
between interfaces.
Rectifier — A device that converts alternating current to direct current. See inverter.
Regulator — Prevents overcharging of batteries by controlling charge cycle-usually adjustable to conform to specific
battery needs.
Remote Systems — See stand-alone systems.
Reserve Capacity — The amount of generating capacity a central power system must maintain to meet peak loads.
Resistance (R) — The property of a conductor, which opposes the flow of an electric current resulting in the
generation of heat in the conducting material. The measure of the resistance of a given conductor is the
electromotive force needed for a unit current flow. The unit of resistance is ohms.
Resistive Voltage Drop — The voltage developed across a cell by the current flow through the resistance of the cell.
Reverse Current Protection — Any method of preventing unwanted current flow from the battery to the photovoltaic
array (usually at night). See blocking diode.
Ribbon (Photovoltaic) Cells — A type of photovoltaic device made in a continuous process of pulling material from a
molten bath of photovoltaic material, such as silicon, to form a thin sheet of material.
RMS — See root mean square.
Root Mean Square (RMS) — The square root of the average square of the instantaneous values of an ac output.
For a sine wave the RMS value is 0.707 times the peak value. The equivalent value of alternating current, I, that will
produce the same heating in a conductor with resistance, R, as a dc current of value I.
total solar cell area to the total module area, for a module.
Panel — See photovoltaic (PV) panel.
Parallel Connection — A way of joining solar cells or photovoltaic modules by connecting positive leads together and
negative leads together; such a configuration increases the current, but not the voltage.
Passivation — A chemical reaction that eliminates the detrimental effect of electrically reactive atoms on a solar
cell's surface.
Peak Demand/Load — The maximum energy demand or load in a specified time period.
Peak Power Current — Amperes produced by a photovoltaic module or array operating at the voltage of the I-V
curve that will produce maximum power from the module.
Peak Power Point — Operating point of the I-V (current-voltage) curve for a solar cell or photovoltaic module where
the product of the current value times the voltage value is a maximum.
Peak Power Tracking — see maximum power tracking.
Peak Sun Hours — The equivalent number of hours per day when solar irradiance averages 1,000 w/m2. For
example, six peak sun hours means that the energy received during total daylight hours equals the energy that
would have been received had the irradiance for six hours been 1,000 w/m2.
Peak Watt — A unit used to rate the performance of solar cells, modules, or arrays; the maximum nominal output of
a photovoltaic device, in watts (Wp) under standardized test conditions, usually 1,000 watts per square meter of
sunlight with other conditions, such as temperature specified.
Phosphorous (P) — A chemical element used as a dopant in making n-type semiconductor layers.
Photocurrent — An electric current induced by radiant energy.
Photoelectric Cell — A device for measuring light intensity that works by converting light falling on, or reach it, to
electricity, and then measuring the current; used in photometers.
Photoelectrochemical Cell — A type of photovoltaic device in which the electricity induced in the cell is used
immediately within the cell to produce a chemical, such as hydrogen, which can then be withdrawn for use.
Photon — A particle of light that acts as an individual unit of energy.
Photovoltaic(s) (PV) — Pertaining to the direct conversion of light into electricity.
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) Conversion Efficiency — The ratio of the electric power produced by a photovoltaic device to the
power of the sunlight incident on the device.
Photovoltaic (PV) Device — A solid-state electrical device that converts light directly into direct current electricity of
voltage-current characteristics that are a function of the characteristics of the light source and the materials in and
design of the device. Solar photovoltaic devices are made of various semiconductor materials including silicon,
cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multicrystalline, or amorphous
forms.
Photovoltaic (PV) Effect — The phenomenon that occurs when photons, the "particles" in a beam of light, knock
electrons loose from the atoms they strike. When this property of light is combined with the properties of
semiconductors, electrons flow in one direction across a junction, setting up a voltage. With the addition of circuitry,
current will flow and electric power will be available.
Photovoltaic (PV) Generator — The total of all PV strings of a PV power supply system, which are electrically
interconnected.
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) 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.
Physical Vapor Deposition — A method of depositing thin semiconductor photovoltaic films. With this method,
physical processes, such as thermal evaporation or bombardment of ions, are used to deposit elemental
semiconductor material on a substrate.
P-I-N — A semiconductor photovoltaic (PV) device structure that layers an intrinsic semiconductor between a p-type
semiconductor and an n-type semiconductor; this structure is most often used with amorphous silicon PV devices.
Plates — A metal plate, usually lead or lead compound, immersed in the electrolyte in a battery.
P/N — A semiconductor photovoltaic device structure in which the junction is formed between a p-type layer and an
n-type layer.
Pocket Plate — A plate for a battery in which active materials are held in a perforated metal pocket.
Point-Contact Cell — A high efficiency silicon photovoltaic concentrator cell that employs light trapping techniques
and point-diffused contacts on the rear surface for current collection.
Polycrystalline — See Multicrystalline.
Polycrystalline Silicon — A material used to make photovoltaic cells, which consist of many crystals unlike single-
crystal silicon.
Power Conditioning — The process of modifying the characteristics of electrical power (for e.g., inverting direct
current to alternating current).
Power Conditioning Equipment — Electrical equipment, or power electronics, used to convert power from a
photovoltaic array into a form suitable for subsequent use. A collective term for inverter, converter, battery charge
regulator, and blocking diode.
Power Conversion Efficiency — The ratio of output power to input power of the inverter.
Power Density — The ratio of the power available from a battery to its mass (W/kg) or volume (W/l).
Power Factor (PF) — The ratio of actual power being used in a circuit, expressed in watts or kilowatts, to the power
that is apparently being drawn from a power source, expressed in volt-amperes or kilovolt-amperes.
Primary Battery — A battery whose initial capacity cannot be restored by charging.
Projected Area — The net south-facing glazing area projected on a vertical plane.
P-Type Semiconductor — A semiconductor in which holes carry the current; produced by doping an intrinsic
semiconductor with an electron acceptor impurity (e.g., boron in silicon).
Pulse-Width-Modulated (PWM) Wave Inverter — A type of power inverter that produce a high quality (nearly
sinusoidal) voltage, at minimum current harmonics.
PV — See photovoltaic(s).
Pyranometer — An instrument used for measuring global solar irradiance.
Pyrheliometer — An instrument used for measuring direct beam solar irradiance. Uses an aperture of 5.7° to
transcribe the solar disc.
Q
Quad — One quadrillion Btu (1,000,000,000,000,000 Btu).
Qualification Test — A procedure applied to a selected set of photovoltaic modules involving the application of
defined electrical, mechanical, or thermal stress in a prescribed manner and amount. Test results are subject to a
list of defined requirements.
R
Rated Battery Capacity — The term used by battery manufacturers to indicate the maximum amount of energy that
can be withdrawn from a battery under specified discharge rate and temperature. See battery capacity.
Rated Module Current (A) — The current output of a photovoltaic module measured at standard test conditions of
1,000 w/m2 and 25�C cell temperature.
Rated Power — Rated power of the inverter. However, some units can not produce rated power continuously. See
duty rating.
Reactive Power — The sine of the phase angle between the current and voltage waveforms in an alternating current
system. See power factor.
Recombination — The action of a free electron falling back into a hole. Recombination processes are either
radiative, where the energy of recombination results in the emission of a photon, or nonradiative, where the energy
of recombination is given to a second electron which then relaxes back to its original energy by emitting phonons.
Recombination can take place in the bulk of the semiconductor, at the surfaces, in the junction region, at defects, or
between interfaces.
Rectifier — A device that converts alternating current to direct current. See inverter.
Regulator — Prevents overcharging of batteries by controlling charge cycle-usually adjustable to conform to specific
battery needs.
Remote Systems — See stand-alone systems.
Reserve Capacity — The amount of generating capacity a central power system must maintain to meet peak loads.
Resistance (R) — The property of a conductor, which opposes the flow of an electric current resulting in the
generation of heat in the conducting material. The measure of the resistance of a given conductor is the
electromotive force needed for a unit current flow. The unit of resistance is ohms.
Resistive Voltage Drop — The voltage developed across a cell by the current flow through the resistance of the cell.
Reverse Current Protection — Any method of preventing unwanted current flow from the battery to the photovoltaic
array (usually at night). See blocking diode.
Ribbon (Photovoltaic) Cells — A type of photovoltaic device made in a continuous process of pulling material from a
molten bath of photovoltaic material, such as silicon, to form a thin sheet of material.
RMS — See root mean square.
Root Mean Square (RMS) — The square root of the average square of the instantaneous values of an ac output.
For a sine wave the RMS value is 0.707 times the peak value. The equivalent value of alternating current, I, that will
produce the same heating in a conductor with resistance, R, as a dc current of value I.
GLOSSARY OF TERMS
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