Glossary of Solar Terms

Glossary of Solar Terms

Alternating current (AC) - A type of electricity measured according to its cycles. An electrical current is able to complete many cycles per second, and is then given its frequency rating based on that number. AC power is the type of electricity most commonly used in homes and offices, and is extremely versatile because its voltage can be changed through a transformer to suit a variety of transmission needs.

Array - A group of solar panels collectively makes up a solar array.

Community Solar – “A solar-electric system that provides power and/or financial benefit to multiple community members.” (US Dept. of Energy). Most community solar models involve groups of solar panels kept at a central location nearby so that the output can be sold and distributed to electric service consumers in the community. Those consumers may benefit by receiving a credit on their monthly electric bills for the solar energy generated without having to invest in equipment installed at their homes.

Direct current (DC) - A type of electrical current that travels through a circuit in only one direction. This is the type of electrical power that is produced by fuel cells, batteries and generators equipped with commutators.

Grid - The network of power lines that connects power plants to substations and then on to distribution lines that take power to homes or businesses. It can be used to refer to a transmission-level grid or a distribution-level grid, which have slightly different functions.

Grid-tied (or grid-connected) system - A solar electric system in which the array can receive power from the electric utility, and can also supply power to the grid.

Insolation - The amount or sunlight reaching an area, usually expressed in Watt hours per square meter per day.

Interconnection application - The form that your electric cooperative representative will ask you to complete. This form initiates the process of connecting your solar PV system to the grid.

Interconnection agreement - The document that defines the terms and conditions under which your system will be connected to the utility grid, including the technical requirements necessary to ensure safety and power quality.

Inverter - A device that converts DC power captured by the photovoltaic cells on solar panels into AC power that can be used to power your home or business. This device is an integral part of a solar PV system. Large solar PV systems may have more than one inverter.

Irradiance - The solar power incident on a surface, usually expressed in kilowatts per square meter. The sum of irradiance multiplied by time is insolation.

kW (kilowatt) - A measurement of power. A kilowatt is 1,000 Watts. The size of a solar PV system is often measured in kW. A typical size solar system for a home is 3-7 kW; for a medium sized business is 10-100 kW.

kWh (kilowatt-hour) - A measurement of energy consumption or energy generation. One kilowatt-hour is defined as the amount of energy consumed by a 1000-Watt appliance running continuously for 1 hour. This is the measurement your utility company uses to calculate your electric bill and will be the measure of your solar PV system's output.

Meter - An electricity meter or energy meter is a device that measures the amount of electric energy consumed by a residence, business or an electrically powered device.

Module - An encapsulated panel containing a number of electrically connected PV cells.
Net metering of solar electricity generation is used to calculate the difference between energy that is used and energy that is produced. The customer is then billed for the electricity he uses, or receives a payment or credit if excess electricity is produced by the solar electric system owned by the customer.

Orientation - Position with respect to the directions of north, south, east, west.

Panel - A group of modules arranged and attached in one plane, or can be used interchangeably with "module."

Photovoltaic (PV) - The process of converting light into electrical energy. A PV cell ls a device that converts light into electrical energy. The PV cells are manufactured into a module, which is then wired into an array, and ultimately into a PV system.

Pyranometer - An instrument used for measuring solar irradiance.

Racking - Structural supports used to hold the modules in place. Racking is used to mount the modules on the roof, the ground or as a panel on top of a pole.

Rated output of a module - The DC power output of a module under standard test conditions (the module is at 25 degrees C and 1000W/m2 of solar irradiance, and typically ranges from 100 to 340 Watts). It is important to note that the actual operating conditions will usually be different from the standard test conditions. 1000W/m2 can be thought of as the solar intensity or a clear sunny day. If the temperature of the panel is more than 25 degrees C (77 degrees F) it will reduce the output that you get from the panels, or if the panel is colder, the DC output can actually be higher than "'rated."

Tilt (or tilt angle) - The angle or inclination or a solar panel or solar module measured from the horizontal (plane of the ground).

Watt (W) - see kilowatt.