Importance of Lawyer
Residential vs. Industrial
Solar Project Law
Green Energy Act
Alberta Farm Leases
SOLAR ENERGY GLOSSARY
Activated shelf life: The time it takes for the capacity of a
charged battery to fall to an unusable level when stored at a
Activation voltage: The voltage at which
the controller will operate to protect the batteries.
(Adsorbed Glass Mat): a newer type of battery construction that uses
saturated adsorbant glass mats rather than gelled or liquid
electrolyte. AGM batteries are typically more expensive than flooded
(liquid), but offer enhanced reliability.
Air mass: The air mass
relates to the path length of solar radiation through the
atmosphere. An air mass of 1.0 means the sun is directly overhead
and the radiation travels through one atmosphere thickness.
Approximately equal to the secant of the zenith angle, i.e. the
angle from directly overhead to a line to the sun.
current (AC): Electrical current that continually reverses direction
of flow. The frequency at which it reverses is measured in
cycles-per-second, or Hertz (Hz). The magnitude of the current
itself is measured in amps (A).
Alternator: A device for
producing Alternating Current ("AC") electricity. Usually driven by
a motor, but can also be driven by other means, including water and
Ambient temperature: The temperature of the
Ammeter: A device used for measuring current flow
at any point in an electrical circuit.
Amorphous silicon: A
thin-film solar PV cell material which has a glassy rather than
crystalline structure. Made by depositing layers of doped silicon on
a substrate normally using plasma-enhanced chemical vapor deposition
Amp hour: The quantity of electrical energy
corresponding to the flow of current of one ampere for one hour. The
term is used to quantify the energy stored in a battery. Most
batteries are rated in Ah.
Ampere (A) or amp: The unit for the
electric current; the flow of electrons. One amp is 1 coulomb
passing in one second. One amp is produced by an electric force of 1
volt acting across a resistance of 1 ohm.
Anemometer: A device
used to measure wind speed.
Angle of incidence: Angle between
the normal to a surface and the direction of incident radiation;
applies to the aperture plane of a solar panel. Only minor
reductions in power output within plus/minus 15 degrees.
The positive electrode in a battery. The positive terminal of a
Anti-reflection coating: A thin coating of a material
with a specific refractive index applied to a cell to reduce the
reflection of light.
Array: A number of solar modules connected
together in a single structure.
Array current: The electrical
current output of a PV array when exposed to sunlight.
operating voltage: The voltage output of a PV array when exposed to
sunlight and feeding a load.
Autonomous system: A PV System that
operates without any other energy generating source.
Availability: The quality or condition of a PV system that is
available to provide power to a load. Usually measured in hours per
AWG: American Wire Gauge: a standard system for
designating the size of electrical wire. The higher the number, the
smaller the wire. Most house wiring is #12 or 14.
Angle between the north direction and the projection of the surface
normal into the horizontal plane; measured clockwise from north. As
applied to the PV array, 180 degree azimuth means the array faces
Balance of system (BOS): All the parts of a PV
System excluding the solar module
Ballast: a circuit used to
stabilize an electric current, for example, in a fluorescent light.
Battery: A system in which stored chemical energy is converted
directly into electrical energy. Can be either rechargeable or
non-rechargeable. Different to a fuel cell in that it contains a
fixed quantity of stored chemical energy rather than a continuous
supply of fuel.
Battery capacity: The total number of
ampere-hours (Ah) that a fully charged battery can output.
Battery cell: An individual unit of a battery that can store
electrical energy and is capable of furnishing a current to an
external load. For lead-acid batteries the voltage of a cell (fully
charged) is about 2.2 volts dc. A battery may consist of a number of
Battery charger: A device used to charge a battery by
converting (usually) mains voltage AC to a DC voltage suitable for
the battery. Chargers often incorporate some form of regulator to
prevent overcharging and damage to the battery.
Life: The number of times a battery can undergo a cycle of discharge
and recharge before failing. Cycle Life is normally specified as a
function of discharge rate and temperature.
self-discharge: Energy loss by a battery that is not under load.
Battery state of charge (SOC): Extent of battery charge status as a
percentage of full charge. Also 100 per cent minus the Depth of
BIPV: Building Integrated Photovoltaics. As the name
suggests, this is where PV modules are integrated in to the building
construction materials as on integrated unit.
Blocking diode: A
diode used to prevent current flow in an undesirable direction e.g.
from the rest of the PV array to a failed module or from the battery
to the PV array when current generation is low.
Unit (BTU): The amount of heat energy required to raise one pound of
water from a temperature of 60 degrees F to 61 degrees F at one
atmosphere pressure. One Watt hour equals 3,413 BTU.
diode: A diode connected across one or more solar cells in a
photovoltaic module such that the diode will conduct if the cell(s)
become reverse biased. [UL 1703]
Capacitor: An electronic
component used for the temporary storage of electricity, as well for
removing unwanted noise in circuits. A capacitor will block Direct
Current but will pass Alternating Current.
Capacity: See Battery
Captive electrolyte battery: A battery with an
immobilized electrolyte (gelled or absorbed in a material).
Cathode: The negative electrode in an electrochemical cell. Also,
the negative terminal of a diode.
Cathodic protection: A method
of preventing oxidation (rusting) of exposed metal structures, such
as bridges and pipelines, by imposing between the structure and the
ground a small electrical voltage that opposes the flow of electrons
and that is greater than the voltage present during oxidation.
Cell efficiency: The ratio of the electrical energy produced by a
photovoltaic cell (under full sun conditions or 1 kW/m2) to the
energy from sunlight falling upon the photovoltaic cell.
junction: The area of immediate contact between two layers (positive
and negative) of a photovoltaic cell. The junction lies at the
center of the cell barrier or depletion zone.
Cell: The basic
unit of a PV module or battery. The most basic unit that contains
the necessary materials, such as electrodes and electrolyte in a
battery, to produce electricity.
Charge: The process of
inputting electrical energy to a battery.
Charge controller: A
component that controls the flow of current to and from the battery
subsystem to protect the batteries from overcharge and over
discharge. Essential for ensuring that batteries obtain maximum
state of charge and longest life. The charge controller may also
monitor system performance and provide system protection. Charge
Controllers are also sometimes called Regulators.
A number corresponding to the time (in hours) for which a battery
can be charged at a constant current without damaging it. Usually
expressed as a function of battery capacity, e.g. C/10 indicates a
charge factor of 10 hours. Related to Charge Rate.
A measure of the current used to charge a battery as a proportion of
Circuit: A continuous system of conductors
providing a path for electricity
Circuit breaker: A circuit
breaker acts like an automatic switch that can shut the power off
when it senses too much current.
Cloud enhancement: The increase
in solar intensity due to reflected light from nearby clouds.
Cogeneration: The joint production of electricity and useful heat at
a single facility, resulting in more efficient use of the thermal
Concentrator: A photovoltaic device that uses optical
elements (e.g. mirrors or lenses) to increase the amount of light
incident on a solar PV cell. Concentrator arrays track the sun and
use only direct sunlight since the diffuse portion cannot be
focused. Concentrators therefore work best in clear sky locations.
Efficiency is increased, but cell life may be reduced because
operating temperatures are higher.
Conductor: A material used to
transfer, or conduct, electricity, often in the form of wires.
Conduit: A pipe or elongated box used to house and protect
Conversion efficiency: The ratio of the
electrical energy generated by a solar PV cell to the solar energy
impacting the cell.
Cross-flow turbine: A turbine where the flow
of water is at right angles to the axis of rotation of the turbine.
Crystalline silicon: A type of PV cell material made from a single
crystal or polycrystalline ingot of silicon.
Current: Current is
the flow of electric charge in a conductor between two points having
a difference in electrical potential (voltage) and is measured in
Current at maximum power (Imp): The current at which
maximum power is available from a module. [UL 1703]
voltage: The voltage levels at which the charge controller
(regulator) disconnects the PV array from the battery, or the load
from the battery.
Cycle: The discharge and re-charge of a
battery, one complete charge/discharge cycle of the battery.
Cycle life: Number of charge-discharge cycles a battery can perform
under specified conditions before it fails to meet its specified
performance (e.g. capacity decreases to 80% of nominal capacity).
Days of storage: The number of days that a stand-alone system
will power a specified load without solar energy input. A measure of
DC to DC converter: Electronic circuit to
convert dc voltages (e.g., PV module voltage) into other levels
(e.g., load voltage). Can be part of a maximum power point tracker
Dealer: A Retailer of PV products and/or PV Systems
Deep cycle battery: A battery designed to regularly discharge 80% of
its capacity before recharging.
Deep discharge: Discharging a
battery by more than 80% of its full charge.
Depth of discharge
(DOD): the amount of energy withdrawn from a battery or cell
expressed as a percentage of its rated capacity.
The month in which the combination of insolation and load requires
the maximum energy from the array.
Diffuse insolation: Incident
sunlight received indirectly because of scattering due to clouds,
fog, particulates, or other obstructions in the atmosphere. The
other component of sunlight is Direct.
Radiation received from the sun after reflection and scattering by
the clouds, fog, haze, dust or other substances in the atmosphere,
and the ground.
Diode: Electronic device that allows current
flow only in one direction.
Direct beam radiation: Radiation
received by direct sunlight. Measured by a pyrheliometer with a
solar aperture of 5.7° to transcribe the solar disc.
current (DC): Electrical current that flows only in one direction,
although it may vary in magnitude. Contrasts with alternating
Direct insolation: Sunlight falling directly upon a
collector. Opposite of diffuse insolation.
Light that has traveled in a straight path from the sun (also
referred to as beam radiation). An object in the path of direct
radiation casts a shadow on a clear day.
of electrical energy from a battery.
Discharge factor: A number
equivalent to the time in hours during which a battery is discharged
at constant current usually expressed as a percentage of the total
battery capacity, i.e., C/5 indicates a discharge factor of 5 hours.
Discharge rate: A measure of the current withdrawn from a
battery over time, expressed as a percentage of battery capacity. A
C/5 discharge rate indicates a current of one-fifth of the rated
capacity of the battery.
Disconnect: Switch used to connect or
disconnect components in a PV system.
ability of a generating unit or other source of electric power to
Dispatchable power: Energy output that can be
planned on and typically provides a continuous power output. Solar
power and Wind power in not dispatchable without configuration with
out some other power or storage mechanism. Hydrocarbon based power
plants or nuclear plants are dispatchable.
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
Distributor: Using means a wholesaler of PV
Downtime: Time when the PV system cannot provide power
to the load, expressed either in hours per year or as a percentage.
Dry cell battery: A battery that uses a solid paste for an
Duty cycle: The ratio of active to total time, used
to describe the operating regime of loads in PV systems.
rating: The amount of time an inverter can operate at full rated
power. Some inverters can operate at their rated power for only a
short time without overheating.
Earth: Refers to physically
connecting a part of an electrical system to the ground, done as a
safety measure, by means of a conductor embedded in suitable soil.
Earth-leakage circuit breaker (ELCB): A device used to prevent
electrical shock hazards in mains voltage power systems, including
independent power systems. Also known as residual current devices
Efficiency: The ratio of output power or energy to
input power or energy, expressed as a percentage.
circuit: Path followed by electrons from a power source (generator
or battery) through an external line (including devices that use the
electricity) and returning through another line to the source.
Electric current: The flow of electrons measured in Amps.
Electrical grid: A network for electricity distribution across a
Electricity: The movement of electrons (a sub-atomic
particle), produced by a voltage, through a conductor.
Electrode: An electrically conductive material, forming part of an
electrical device, often used to lead current into or out of a
liquid or gas. In a battery, the electrodes are also known as
Electrolysis: A chemical reaction caused by the passage
of electricity from on electrode to another.
medium that provides ionic transport between the electrodes of a
battery. All common batteries contain an electrolyte, such as the
sulfuric acid used in lead-acid batteries.
Energy density: The
ratio of the energy available from an energy storage device such as
a battery to its volume (Wh/m3) or weight (Wh/kg).
payback time: The time required for any energy producing system or
device to produce as much energy as was required in its manufacture.
For solar electric panels, this is normally in the range 6-36
Energy: Power consumed multiplied by the duration of
use. For example, 1000 Watts used for four hours is 4000 Watt hours.
Equalization charge: Periodical overcharging the batteries for a
short time to mix the electrolyte solution in batteries.
(Ethylene Vinyl Acetate): An encapsulant used between the glass
cover and the solar cells in PV modules. It is durable, transparent,
resistant to corrosion, and flame retardant.
Fill factor: On
an I-V (current-voltage) curve characterizing the output of a solar
cell or module, the ratio of the maximum power to the product of the
open-circuit voltage and the short-circuit current. The higher the
fill factor (FF) the "squarer" the shape of the I-V curve.
tilt array: A solar PV array set at a fixed angle to the horizontal.
Flat-plate PV: A solar PV array or module that does not contain
concentrating devices and so responds to both direct and diffuse
Float charge: A battery charge current that is equal
to, or slightly greater than, the self-discharge rate.
life: The time (usually in years) a battery can maintain its stated
capacity when kept at float charge.
Flooded cell battery: A form
of rechargeable battery where the plates are completely immersed in
a liquid electrolyte. Most cars use flooded-cell batteries. Flooded
cell batteries are the most commonly used type for independent and
remote area power supplies.
Fluorescent light: A form of
lighting that uses long thin tubes of glass which contain mercury
vapor and various phosphor powders (chemicals based on phosphorus)
to produce white light. Generally considered to be the most
efficient form of home lighting.
Frequency: The number of cycles
or repetitions per unit time of a complete waveform, in electrical
applications usually expressed in cycles per second or Hertz (Hz).
Electrical equipment in the United States requires 60 Hz, in Europe
Fresnel lens: A concentrating lens, positioned above and
concave to a PV material to concentrate light on the material.
Fuel cell: An electrochemical device that converts the energy of a
fuel directly into electricity and heat and is therefore very energy
Fuse: A fuse is a device used to protect electrical
equipment from short circuits. Fuses are made with metals that are
designed to melt, when the current passing through them is high
enough. When the fuse melts, the electrical connection is broken,
interrupting power to the circuit or device.
Gaseous by-products when charging a battery, e.g. hydrogen from a
lead acid battery.
Gel-type battery: Lead-acid battery in which
the electrolyte is immobilized in a gel. Usually used for mobile
installations and when batteries will be subject to high levels of
shock or vibration.
Generator: A mechanical device used to
produce DC electricity. Power is produced by coils of wire passing
through magnetic fields inside the generator. Most alternating
current generating sets are also referred to as generators.
Gigawatt (GW): A measurement of power equal to a thousand million
Gigawatt-hour (GWh): A measurement of energy. One
Gigawatt-hour is equal to one Gigawatt being used for a period of
one hour, or one Megawatt being used for 1000 hours.
electrical utility distribution network.
energy producing system connected to the utility transmission grid.
Also called Grid tied.
Ground loop: An undesirable feedback
condition caused by two or more circuits sharing a common electrical
line, usually a grounded conductor.
Halogen lamp: A special
type of incandescent globe made of quartz glass and a tungsten
filament, enabling it to run at a much higher temperature than a
conventional incandescent globe. Efficiency is better than a normal
incandescent, but not as good as a fluorescent light.
content: Frequencies in the output waveform in addition to the
primary frequency (usually 50 or 60 Hz.) Energy in these harmonics
is lost and can cause undue heating of the load.
vertical distance that water will fall from the inlet of the
collection pipe to the water turbine in a hydro power system.
Hertz (Hz): Unit of measurement for frequency. Home mains power is
normally 50Hz in Europe and 60Hz in the USA. The magnitude of the
current is measured in Amps.
High voltage disconnect: Voltage at
which the charge controller will disconnect the array to prevent
overcharging the batteries.
Hot spot: A phenomenon where one or
more cells within a PV module or array act as a resistive load,
resulting in local overheating or melting of the cells.
system: A PV system that includes solar PV and some other
electricity generating power source.
Incandescent light: an
electric lamp which is evacuated or filled with an inert gas and
contains a filament (commonly tungsten). The filament emits visible
light when heated to extreme temperatures by passage of electric
current through it.
Incident light: Light that shines on to the
surface of a PV cell or module.
Independent power system: A
power generation system that is independent of the mains grid.
Insolation: The amount of sunlight reaching an area, usually
expressed in Watt hours per square meter per day.
Usually a retailer and installer of PV Systems
material used to prevent the flow of electricity. Normally used on
electrical wires to prevent electric shock. Typical materials used
include plastics such as PVC and polypropylene.
Integrates PV components in to a complete PV System
A conductor within a module or other means of connection which
provides an electrical interconnection between the solar cells. [UL
Inverter: An inverter converts DC power from the PV
array/battery to AC power. Used either for stand-alone systems or
Irradiance: The solar power incident on
a surface, usually expressed in kilowatts per square meter.
Irradiance multiplied by time gives insolation.
I-V curve: A
graph that plots the current versus the voltage from a PV cell as
the electrical load (or resistance) is increased from short circuit
(no load) to open circuit (maximum voltage). The shape of the curve
characterizing cell performance. Three important points on the I-V
curve are the open-circuit voltage, short-circuit current, and peak
or maximum power (operating) point.
I-V data: The relationship
between current and voltage of a photovoltaic device in the
power-producing quadrant, as a set of ordered pairs of current and
voltage readings in a table, or as a curve plotted in a suitable
coordinate system [ASTM E 1036]
Joule (J): The energy
conveyed by one Watt of power for one second, unit of energy equal
to 1/3600 kilowatt-hours.
Junction box: A PV junction box is a
protective enclosure on a PV module where PV strings are
electrically connected and where electrical protection devices such
as diodes can be fitted.
Junction diode: A semiconductor device,
having a junction and a built-in potential, that passes current
better in one direction than the other. All solar cells are junction
Kilowatt(kW): A unit of electrical power, one
Kilowatt-hour (kWh): The amount of energy that
derives from a power of one thousand Watts acting over a period of 1
hour. The kWh is a unit of energy. 1 kWh=3600 kJ.
Unit of solar irradiance, one calorie per square centimeter. 1 L =
Lead-acid battery: A type of battery that consists
of plates made of lead, lead-antimony, or lead-calcium and
lead-oxide, surrounded by a sulfuric acid electrolyte. The most
common type of battery used in RAPS systems.
Life: The period
during which a system can operate above a specified performance
Life-cycle cost: The estimated cost of owning, operating
and disposing of a system over its useful life.
diode: A semi conductor device composed of a p-n junction designed
such that electrons emit visible light during their migration across
Light trapping: The trapping of light inside a
semiconductor material by refracting and reflecting the light at
critical angles; trapped light will travel further in the material,
greatly increasing the probability of absorption and hence of
producing charge carriers.
Light-induced defects: Defects, such
as dangling bonds, induced in an amorphous silicon semiconductor
upon initial exposure to light.
Line wire loss: refers to the
voltage or power lost due to the resistance of any wire or wires in
any electrical circuit.
Linear current booster: an electronic
circuit that matches PV output directly to a motor. Used in array
direct water pumping.
Liquid electrolyte battery: A battery
containing a liquid solution of an electrolyte in a solvent (e.g.
sulfuric acid in water). Also called a flooded battery because the
plates are covered with the electrolyte solution.
electrical power being consumed at any given moment or averaged over
a specified period. The load that an electric generating system
supplies varies greatly with time of day and to some extent season
of year. Also, in an electrical circuit, the load is any device or
appliance that is using power.
Load circuit: The wiring
including switches and fuses that connects the load to the power
Load current: The current required to power the
Load resistance: The electrical resistance of
Low voltage cut-off: The voltage at which a controller
will disconnect the load from the battery.
disconnect (LVD): The voltage at which the charge controller will
disconnect the load from the batteries to prevent over-discharging.
Low voltage warning: A warning buzzer or light that indicates
the low battery voltage set-point has been reached.
Maintenance free battery: A sealed battery to which water cannot be
added to maintain the level of the electrolyte solution.
power point (MPP): Operating a PV array at that voltage will produce
maximum power. The point on the current-voltage (I-V) curve of a
module under illumination, where the product of current and voltage
is maximum. [UL 1703] This corresponds to the point on an I-V curve
that represents the largest area rectangle that can be drawn under
the curve. For a typical silicon cell panel, this is about 17 volts
for a 36 cell configuration.
Maximum power point tracker (MPPT):
A power conditioning unit that automatically operates the PV
generator at its MPP under all conditions. An MPPT will typically
increase power delivered to the system by 10% to 40%, depending on
climate conditions and battery state of charge.
Megawatt (MW): A
measurement of power equal to one million Watts.
A measurement of power with respect to time (i.e. energy). One
megawatt-hour is equal to one megawatt being used for a period of
one hour, or one kilowatt being used for 1000 hours.
Microgroove: A small groove scribed into the surface of a cell which
may be filled with metal for contacts.
Modified sine wave: A
waveform with at least three states (positive, off, and negative)
used to simulate a sine wave. It has less harmonic content than a
square wave. This type of waveform is better than a square wave, but
not as suitable for some appliances as a sine wave.
The use of complete sub-assemblies to produce a larger system. Also
the use of multiple inverters connected in parallel to service
Module: An encapsulated panel containing a
number of electrically connected PV cells.
factor: A factor that lowers the power output of a module to account
for field operating conditions e.g. dirt build-up on the module.
Monocrystalline solar cell: A form of solar cell made from a thin
slice of a single large crystal of silicon.
Fabricated as a single structure, as used to describe thin film
series interconnected PV cells on a single sheet substrate.
Multicrystalline: A material that has solidified at a rate such that
many small crystals (crystallites) form. The atoms within a single
crystallite are symmetrically arranged with a particular
orientation, whereas the crystallites themselves are differently
oriented. The multitude of grain boundaries in the material (between
the crystallites) reduce the cell efficiency. Multicrystalline is
also referred to as polycrystalline.
Multi-junction device: A PV
device containing two or more cell junctions each of which may be
different in nature and optimized to absorb a particular part of the
solar spectrum in order to achieve higher overall cell efficiency.
Multi-stage controller: A charge controller that allows different
charging currents as the battery approaches full state of charge.
NEC: US National Electrical Code which contains guidelines for
all types of electrical installations which should be followed when
installing a PV system.
NEMA: US National Electrical
Manufacturers Association, sets standards for some non-electronic
products e.g. junction boxes.
Net metering: The practice of
exporting surplus solar power during the day (to actual power needs)
to the electricity grid, which either causes the home owner electric
meter to (physically) go backwards and/or simply creates a financial
credit on the home owner's electricity bill. (At night, the
homeowner draws from the electricity grid in the normal way).
Nickel-cadmium battery (NiCad): A form of rechargable battery,
having higher storage densities than that of lead-acid batteries,
that uses a mixture of nickel hydroxide and nickel oxide for the
anode, and cadmium metal for the cathode. The electrolyte is
Noise: Unwanted electrical signals produced
by electric motors and other machines that can cause circuits and
appliances to malfunction.
Nominal voltage: A rounded voltage
value used to describe batteries, modules, or systems based on their
specification (e.g. a 12V, 24V or 48V battery, module, or system).
Normal Operating Cell Temperature (NOCT): The estimated
temperature of a solar PV module when it is operating under 800 W/m2
irradiance, 20°C ambient temperature and a wind speed of 1 meter per
second. NOCT is used to estimate the nominal operating temperature
of a module in the field.
N-type semiconductor: A semiconductor
produced by the doping of an intrinsic semiconductor with an
electron-donor impurity, for example phosphorous in silicon.
N-Type silicon: Silicon doped with an element that has more
electrons in its atomic structure than does silicon (e.g.
Ohm: The resistance between two points of a
conductor when a constant potential difference of one Volt applied
between these points produces in the conductor a current of one Amp.
Ohm's Law: A simple mathematical formula that allows either
voltage, current or resistance to be calculated when the other two
values are known. The formula is: V = I x R, where V is the voltage,
I is the current, and R is the resistance.
One-axis tracking: A
PV System structure that is capable of rotating on a single axis in
order to track the movement of the sun.
Open circuit voltage: The
maximum voltage produced by an illuminated solar PV cell, module, or
array when no load is connected. OCV increases as the temperature of
the PV material decreases.
Operating point: Defined by the
current and voltage that a module or array produces when connected
to a load. It is dependent on the load or the batteries connected to
the output terminals.
Orientation: Position with respect to the
cardinal directions, N, S, E, W.
Overcharge: Applying current to
a fully charged battery. This can damage the battery.
Used interchangeably with "module".
Parallel connected: A method
of connection in which positive terminals are connected together and
negative terminals are connected together. Current output adds and
voltage remains the same.
Passive solar home: A house that
utilizes part of the building as a solar collector, as opposed to
active solar, such as PV.
Peak load: The maximum usage of
electrical power occurring in a given period of time, typically a
day. The electrical supply must be able to be meet the peak load if
it is to be reliable.
Peak power current: Current in Amperes
produced by a module or array operating at the voltage on the I-V
curve that will produce its maximum power.
Peak sun hours: The
equivalent number of hours per day when solar irradiance averages
Peak Watt: The amount of power a solar PV cell or
module will produce under standard test conditions (normally 1000
W/m2 and 25°C cell temperature, AM 1.5 spectrum).
is composed of energy particles called photons which have variable
energy but constant speed.
Photovoltaic (PV) array: A number of
PV modules connected together in a single structure.
Photovoltaic (PV) cell: The smallest discrete element in a PV module
that performs the conversion of light into electrical energy to
produce a DC current and voltage.
Photovoltaic (PV) conversion
efficiency: The ratio of the electrical power generated by a PV
device to the power of the light incident on it. This is typically
in the range 5% to 15% for commercially available modules.
Photovoltaic (PV) generator: The total of all PV strings of a PV
power supply system, which are electrically interconnected.
Photovoltaic (PV) module: A single assembly of solar cells and
ancillary parts, such as interconnections, terminals, (and
protective devices such as diodes) intended to generate DC power
under un-concentrated sunlight. The structural (load carrying)
member of a module can either be the top layer (superstrate) or the
back layer (substrate). [UL 1703]
Photovoltaic (PV) panel: a
term often used interchangeably with PV module (especially in single
Photovoltaic (PV): refers to any device which
produces free electrons when exposed to light.
system: All the parts connected together that are required to
produce solar electricity.
Photovoltaic cell: The semiconductor
device that converts solar irradiance (light) into dc electricity.
Photovoltaic effect: The effect that causes a voltage to be
developed across the junction of two different materials when they
are exposed to light.
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
Plates: The electrodes in a battery, usually take the
form of metal plates.
Polycrystalline cell: a wafer of silicon
with a multi-grained structure. All grains have the same atomic
crystal lattice, however, each grain has a unique orientation in
space thereby producing a unique reflection of light.
Polycrystalline silicon: A material used to make solar PV cells
which consists of many crystals, compared to single crystal silicon.
Poly-vinyl chloride (PVC): A plastic used as an insulator on
electrical cables. A toxic material, which is being replaced with
alternatives made from more benign chemicals
Basic unit of electricity equal to the product of current and
voltage (in DC circuits).
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 e.g. of an inverter.
The ratio of the power available from a battery to its volume (Watts
per liter) or weight (Watts per kilogram).
Power factor: The
cosine of the phase angle between the voltage and the current
waveforms in an AC circuit. A measure of inverter performance.
Power: The rate of doing work. Expressed as Watts (W). For example,
a generator rated at 800 watts can provide that amount of power
continuously. 1 Watt = 1 joule/sec.
Primary battery: A battery
that cannot be re-charged.
PV array: two or more photovoltaic
panels wired in series and or parallel.
PV: Short hand for
PV components: The individual parts of a PV
System. Individual items like Batteries, Inverters, Regulators,
PV system: All the parts in combination required to
generate solar electricity
Pyranometer: An instrument for
measuring total hemispherical solar irradiance on a flat surface, or
"global" irradiance; thermopile sensors have been generally
identified as pyranometers, however, silicon sensors are also
referred to as pyranometers.
Qualification test (PV): A
testing procedure for PV modules relating to electrical, mechanical,
or thermal stress.
Quasi sine-wave: A description of the type of
waveform produced by some Inverters.
RAPS (Remote Area Power
Supply): A power generation system used to provide electricity to
remote and rural homes, usually incorporating power generated from
renewable sources such as solar panels and wind generators, as well
as non-renewable sources such as petrol-powered generators.
Rated battery capacity (Ah): Term used by battery manufacturers to
indicate the maximum amount of energy that can be withdrawn from a
battery at a specified discharge rate and temperature.
module current (A): The current output of a PV module measured under
standard test conditions of 1000 W/m2 and 25°C cell temperature.
Rated power: Nominal power output of an inverter, some units cannot
produce rated power continuously.
Reactive power: The sine of
the phase angle between the current and voltage waveforms in an AC
Rechargeable battery: A type of battery that uses a
reversible chemical reaction to produce electricity, allowing it to
be re-used many times. The chemical reaction is reversed by forcing
electricity through the battery in the opposite direction to normal
Rectifier: A device that converts ac to dc, as in a
battery charger or converter.
Regulator: A device used to limit
the current and voltage in a circuit, normally to allow the correct
charging of batteries from power sources such as solar panels and
Remote site: A site with no electrical utility
Renewable energy: Energy that is produced from
a renewable source.
Resistance (R): The property of a material
which resists the flow of electric current when a potential
difference is applied across it, measured in Ohms.
voltage drop: The voltage developed across a cell by the current
flow through the resistance of the cell which may result from the
bulk resistance of the materials in the cell and at interfaces
Resistor: An electronic component used to restrict
the flow of current in a circuit. Sometimes used specifically to
produce heat, such as in a water heater element.
Condition where the current producing capability of a PV cell is
significantly less than that of other cells in its series string.
This can occur when a cell is shaded, cracked, or otherwise degraded
or when it is electrically poorly matched with other cells in its
Reverse current protection: Any means of preventing
current flow from the battery to the solar PV array (e.g. at night)
that would discharge the battery.
Sacrificial anode: A piece
of metal electrically connected to a buried or submerged structure
that is to be protected from corrosion. The metal of the sacrificial
anode is selected to corrode preferentially to the metal of the
protected structure and so reduce its corrosion rate.
battery: A battery with a captive electrolyte and a re-sealing vent
cap to which electrolyte cannot be added. Also called a
Sealed lead-acid battery: A form of
lead-acid battery where the electrolyte is immobilized, either by
being contained in an absorbent fibre separator or gel between the
Secondary battery: A battery that can be
recharged; a rechargeable battery.
Self discharge: Self
discharge represents energy lost to internal chemical reactions
within the cell.
Self discharge rate: The rate at which a
battery will lose its charge when at open circuit (with no load
Semiconductor: A material that has an electrical
conductivity in between that of a metal and an insulator.
Transistors and other electronic devices are made from
semiconducting materials, and are often called semiconductors.
Typical semiconductors for PV cells include silicon, gallium
arsenide, copper indium diselenide, and cadmium telluride.
Series connected: A method of connection in which the positive
terminal of one device is connected to the negative terminal of
another. The voltages add and the current is limited to the least of
any device in the string.
Series regulator: A type of battery
charge controller or regulator in which the charging current is
controlled by a switch, transistor, or field-effect transistor
connected in series with the PV module or array.
resistance: Resistance to current flow within a cell due to factors
such as the bulk resistance of the cell materials and contact
Shallow-cycle battery: A battery with small plates
that cannot withstand many deep discharges (i.e. to a low state of
Shelf life: The time for which a device can be stored
and still retain its specified performance.
current (Isc) : The current generated by an illuminated solar PV
cell, module, or array when its output terminals are shorted; the
maximum current possible.
Shunt controller: A controller or
regulator that re-directs, or shunts, the charging current away from
the battery. Generally used for smaller systems.
Silicon (Si): A
chemical element with atomic number 14, a dark gray semi-metal.
Occurs in a wide range of silicate minerals and makes up
approximately 28% of the earth's crust (by weight). Silicon has a
face-centered cubic lattice structure like diamond. The most common
semiconductor material used in making PV cells either traditionally
in its crystalline form or more recently as an amorphous thin film.
Sine wave: A waveform that has is defined by an equation in which
one variable is proportional to the sine of the other, as generated
by an oscillator in simple harmonic motion. The sine wave is the
most ideal form of electricity for running more sensitive
appliances, such as radios, TVs, computers and the like.
wave inverter: An inverter that produces grid-quality, sine wave AC
Single-crystal silicon: Silicon material with a
single crystal structure. A common material for the construction of
solar PV cells.
Solar constant: The power density of solar
radiation on a plane perpendicular to the direction of the sun at
the mean earth-sun distance outside the earth's atmosphere; its
value is 1.37 kW per square meter.
Solar energy: Energy from the
Solar noon: The mid-point between sunrise and sunset; the
time when the sun reaches its highest point in its daily arc across
Solar power: Electricity generated by conversion of
sunlight, either directly through the use of photovoltaic panels, or
indirectly through solar-thermal processes.
Solar module: A
device used to convert light from the sun directly into DC
electricity by using the photovoltaic effect. Usually made of
multiple solar cells bonded between glass and a backing material. A
typical Solar Module would be 100 Watts of power output (but module
powers can range from 1 Watt to 300 Watts) and have dimensions of 2
feet by 4 feet.
Solar resource: The amount of solar insolation
received at a site, normally measured in units of kWh/m2/day which
equates to the number of peak sun hours.
Solar spectrum: The
total distribution of electromagnetic radiation emanating from the
Solar thermal electric: Method of producing electricity
from solar energy by using focused sunlight to heat a working fluid,
which in turn drives a turbogenerator.
Solar thermal: A form of
power generation using concentrated sunlight to heat water or other
fluid that may then used to drive a motor or turbine.
Solar-grade silicon: Intermediate-grade silicon used in the
manufacture of solar cells. Less expensive than electronic-grade
Specific gravity: The ratio of the weight of a solution
to the weight of an equal volume of water at a specified
temperature; used with reference to the sulfuric acid electrolyte
solution in a lead acid battery as an indicator of battery state of
charge. More recently called relative density.
cell: A compound photovoltaic device in which sunlight is first
divided into spectral regions by optical means. Each region is then
directed to a different photovoltaic cell optimized for converting
that portion of the spectrum into electricity. Such a device
achieves significantly greater overall conversion of incident
sunlight into electricity.
Square wave: A train of rectangular
voltage pulses that alternate between two fixed values for equal
lengths of time.
Square wave inverter: The simplest and the
least expensive type of inverter, but which produces the lowest
quality of power. The inverter uses switches that can carry a large
current and withstand a high voltage that are turned on and off in
the correct sequence and at a certain frequency.
system): A solar PV system that operates without connection to a
grid a supply of electricity.
Standard test conditions (STC):
Conditions under which a module is typically tested in a laboratory:
(1) Irradiance intensity of 1000 W/square meter (0.645 watts per
square inch), AM1.5 solar reference spectrum, and (3) a cell
(module) temperature of 25 degrees C, plus or minus 2 degrees C (77
degrees F, plus or minus 3.6 degrees F). [IEC 1215]
current: The current used by the inverter when no load is active,
corresponding to lost power.
Stand-off mounting: Technique for
mounting a PV array on a sloped roof, which involves mounting the
modules a short distance above the pitched roof and tilting them to
the optimum angle.
State of charge (SOC): The capacity of a
battery at a particular time expressed at a percentage of its rated
Static head: The height of the water level above the
point of free discharge of the water, normally measured when the
pump is off.
Storage: Storing energy in a battery or battery
stack. In water pumping, storage can be achieved by pumping water to
a storage tank.
Storage density: The capacity of a battery, in
amp-hours compared to its weight. Measured in Watt-hours per
Stratification: Occurs in a liquid electrolyte
solution when its concentration varies from top to bottom. Can be
solved by periodic controlled charging at voltages that produce
gassing to mix the electrolyte solution.
String: A number of
cells, modules or panels interconnected electrically in series to
produce the required operating voltage.
Substrate: The physical
material upon which a photovoltaic cell is made. Sub-system: Any one
of several components in a PV system (i.e., array, controller,
batteries, inverter, load).
Suction head: The height of pump
above the surface of the water source when the pump is located above
the water level.
Sulfation: The formation of lead-sulfate
crystals on the plates of a lead-acid battery; large crystals of
lead sulfate grow on the plate, instead of the usual tiny crystals,
making the battery extremely difficult to recharge. If the crystals
get large enough, shorting of the cell may occur.
The covering on the sun side of a PV module, providing protection
for the PV materials from impact and environmental degradation while
allowing maximum transmission of the appropriate wavelengths of the
Surge capacity: The ability of an inverter or
generator to deliver instantaneous high currents when starting
motors, for example.
Surge: An excessive amount of power drawn
by an appliance when it is first switched on. An unexpected flow of
excessive current, usually caused by excessive voltage, that can
damage appliances and other electrical equipment.
common device which breaks an electrical circuit thereby halting the
flow electricity through the circuit.
Switch-mode: A form of
converting one form of electricity to another by rapidly switching
it on and off and feeding it through a transformer to effect a
System availability: The proportion of time
(usually expressed in hours per year) that a solar PV system will be
able to meet fully the load demand.
System operating voltage:
The output voltage of a solar PV array under load, dependent on the
electrical load and size of the battery stack connected to the
Temperature compensation: Adjustment via
the use of electronic circuitry to change the charge controller
activation points depending on battery temperature. This is
desirable if the battery temperature is expected to vary by more
than 5 deg C from the ambient temperature. The temperature
coefficient for lead acid batteries is typically -3 to -5 millivolts/deg
C per cell.
Temperature factors: Are used to decrease battery
capacity at cold temperatures, to decrease PV module voltage at high
temperatures and to increase the resistance of wire at high
Thermal electric: Electric energy derived from
heat energy, usually by heating a working fluid, which drives a
Thermophotovoltaic (TPV) device: A device in
which solar energy is concentrated on to a radiator which reaches a
high temperature and emits the energy in a different part of the
spectrum, better matched to the bandgap of the matched solar cell.
This approach should enable high cell efficiencies to be obtained.
Thick cells : Conventional solar cells in most types of PV modules,
such as crystalline silicon cells, which are typically from 200-400
micrometers thick. In contrast, thin-film cells are several microns
Thick-crystalline materials: Semiconductor material,
typically measuring from 200-400 micromterers thick, that is cut
from boules, ingots or ribbons.
Thin film PV module: A solar PV
module constructed with sequential layers of thin film semiconductor
materials usually only micrometers thick. Currently, thin film
technologies account for around 12% of all solar modules sold around
the world. This share is expected to increase, since thin film
technologies represent a potential route to lower costs.
film: A layer of semiconductor material, such as copper indium
diselenide, cadmium telluride, gallium arsenide, or amorphous
silicon, a few microns or less in thickness, used to make
Tilt angle: The angle of inclination of a
solar collector or solar module measured from the horizontal.
Total AC load demand: The sum of the AC loads; its value is
important to select the correct Inverter.
reflection: The trapping of light within the PV cell by internal
reflection of incident light at angles greater than the critical
angles for the interfaces, so that the light cannot escape the cell
and is therefore eventually absorbed by the semiconductor.
Tracker: any device used to direct a PV array towards the sun.
Tracking array: A PV array that is moved to follow the path of the
sun in order to maintain the maximum incident solar radiation on its
surface. The two most common methods are firstly single-axis
tracking in which the array tracks the sun from east to west, and
secondly, two-axis tracking in which the array points directly at
the sun all the time. Two-axis tracking arrays capture the maximum
possible daily energy. Typically, a single axis tracker will give
15% to 25% more power per day, and dual axis tracking will add a
Transformer: A transformer is a device that changes
voltage from one level to another. A device used to transform
voltage levels to facilitate the transfer of power from the
generating plant to the customer.
Transistor: A semi-conductor
device used to switch or otherwise control the flow of electricity.
Trickle charge: A small charging current designed to keep a
battery fully charged.
Two-axis tracking: A system capable of
rotating independently about two axes (e.g., vertical and
horizontal) and following the sun for maximum efficiency of the
Uninterruptible power supply (UPS): A power
supply capable of providing continuous uninterruptible service;
normally containing batteries to provide energy storage.
Utility-interactive inverter: An inverter that can operate only when
connected to the utility grid supply and an output voltage frequency
fully synchronized with the utility power.
Varistor: A non-ohmic or voltage-dependent
variable resistor. Normally used as over-voltage limiters to protect
sensitive equipment from power spikes or lightning strikes by
shunting the energy to ground.
VDC: Volts direct current
Vented cell: A battery with a vent to expel gases liberated during
Vmp: The voltage at which a PV device is operating at
Voc: Open-circuit voltage Volt (V): The unit of
electromotive force that will force a current of one ampere through
a resistance of one ohm. Voltage at maximum power
Volt: The unit
if electric potential and potential difference. The amount of work
done per unit charge in moving a charge from one place to another.
The potential difference across a resistance of 1 Ohm when a current
of 1 Amp is flowing.
Voltage drop: The voltage lost along a
length of wire or conductor due to the resistance of that conductor.
This also applies to resistors. The voltage drop is calculated by
using Ohm's Law.
Voltage protection: A sensing circuit on an
Inverter that will disconnect the unit from the battery if input
voltage limits are exceeded.
Voltage regulator: A device that
controls the operating voltage of a photovoltaic array.
Unit of measurement for the electrical `pressure' of electricity.
Measured in Volts (V).
Voltmeter: An electrical or electronic
device used to measure voltage.
Wafer: A thin sheet of
crystalline semiconductor material either made by mechanically
sawing it from a single-crystal boule or multicrystalline ingot or
block, or made directly by casting. The wafer is "raw material" for
the solar cell.
Watt (W) : The unit of electrical power commonly
used to define the electricity consumption of an appliance. The
power developed when a current of one ampere flows through a
potential difference of one volt; 1/746 of a horsepower. 1 Watt = 1
Watt hour (Wh): A unit of energy equal to one Watt of
power being used for one hour.
Waveform: The shape of a wave or
pattern representing a vibration. The shape characterizing an AC
current or voltage output.
Watt peak (User friendly definition):
Is the Direct Current Watts output of a Solar Module as measured
under an Industry standardized Light Test before the Solar Module
leaves the Manufacturers facility.
Watt peak: (technical
definition): The Watt Power output of a Solar module is the number
of Watts Output when it is illuminated under standard conditions of
1000 Watts/meter2 intensity, 25°C ambient temperature and a spectrum
that relates to sunlight that has passed through the atmosphere (AM
or Air Mass 1.5).
Wet shelf life: The period over which a
charged battery, filled with electrolyte, can remain unused before
its performance falls below a specified.
Zenith angle: The angle between directly overhead and a line through
the sun. The elevation angle of the sun above the horizon is 90°
minus the zenith angle.