Solar Energy Glossary
Solar Energy Facts
The language of solar energy can be confusing for consumers wishing to learn more about the topic.
The following glossary is adapted from Department of Energy sources.
AC: Alternating current, a type of electrical current which reverses direction 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 of the ease it provides for voltage control.
Amorphous Semiconductor: A non-crystalline semiconductor material with no long-range order.
Ampere or 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.
Anode: The positive electrode in an electrochemical cell (battery).
Base Load: he average amount of electric power that a utility must supply in any period.
Battery: Two or more electrochemical cells enclosed in a container and electrically interconnected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels.
Blocking Diode: A semiconductor connected in series with a solar cell or cells and a storage battery to keep the battery from discharging through the cell when there is no output, or low output, from the solar cell.
Bypass Diode: A diode connected across one or more solar cells in a photovoltaic module such that the diode will conduct if the cells) become reverse biased. It protects these solar cells from thermal destruction in case of total or partial shading of individual solar cells while other cells are exposed to full light.
Cadmium Telluride (CdTe): A polycrystalline thin-film photovoltaic material.
Charge Controller: A component of a photovoltaic system that controls the flow of current to and from the battery to protect it from over-charge and over-discharge.
Converter: A unit that converts a direct current (dc) voltage to another dc voltage.
Crystalline Silicon: A type of photovoltaic cell made from a slice of single-crystal silicon or polycrystalline silicon.
DC: Direct current.
Deep-Cycle Battery: A battery with large plates that can withstand many discharges to a low state-of-charge.
Deep Discharge: Discharging a battery to 20% or less of its full charge capacity.
A type of electricity transmission and distribution by which electricity flows in one direction through the semionductor, 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.
Distributed Power: General term related to a power supply located near the point where the power is used.
Dry Cell: A cell (battery) with a captive electrolyte. A primary battery that cannot be recharged.
Electrode: A conductor that is brought in conducting contact with a ground.
Electrolyte: A nonmetallic (liquid or solid) conductor that carries current by the movement of ions (instead of electrons) with the liberation of matter at the electrodes of an electrochemical cell.
Float Charge: The voltage required to counteract the self-discharge of the battery at a certain temperature.
Full Sun: The amount of power density in sunlight received at the earth's surface at noon on a clear day (about 1,000 Watts/square meter).
Gallium Arsenide (GaAs): A crystalline, high-efficiency compound used to make certain types of solar cells and semiconductor material.
Gel-Type Battery: Lead-acid battery in which the electrolyte is composed of a silica gel matrix.
Gigawatt (GW): A unit of power equal to 1 billion Watts; 1 million kilowatts, or 1,000 megawatts.
Inverter: A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.
Junction Box: A photovoltaic (PV) generator junction box is an enclosure on the module where PV strings are electrically connected and where protection devices can be located, if necessary.
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 1 hour. The kWh is a unit of energy. 1 kWh=3600 kJ.
Lead-Acid Battery: A general category that includes batteries with plates made of pure lead, lead-antimony, or lead-calcium immersed in an acid electrolyte.
Maintenance-Free Battery: A sealed battery to which water cannot be added to maintain electrolyte level.
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.
Modified Sine Wave: A waveform that has at least three states (i.e., positive, off, and negative).
Multicrystalline: A semiconductor (photovoltaic) material composed of variously oriented, small, individual crystals. Sometimes referred to as polycrystalline or semicrystalline.
Nickel Cadmium Battery: A battery containing nickel and cadmium plates and an alkaline electrolyte.
Ohm: A measure of the electrical resistance of a material equal to the resistance of a circuit in which the potential difference of 1 volt produces a current of 1 ampere.
Overcharge: Forcing current into a fully charged battery. The battery will be damaged if overcharged for a long period.
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.
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 (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) 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.
Polycrystalline Silicon: A material used to make photovoltaic cells, which consist of many crystals unlike single-crystal silicon.
Silicon (Si): A semi-metallic chemical element that makes an excellent semiconductor material for photovoltaic devices. It's commonly found in sand and quartz.
Sine Wave: A waveform corresponding to a single-frequency periodic oscillation that can be mathematically represented as a function of amplitude versus angle in which the value of the curve at any point is equal to the sine of that angle.
Sine Wave Inverter: An inverter that produces utility-quality, sine wave power forms.
Single-Crystal Silicon: Material with a single crystalline formation. Many photovoltaic cells are made from single-crystal silicon.
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. It is the product of voltage and current (amperage).
© 2011-2012 Patricia A. Michaels