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Solar Learning Center: Glossary of Terms
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A
Alternating Current (AC): An electric current that reverses direction periodically.
Ampacity: The current that is a conductor can carry continously under the conditions of use without exceeding its temperature rating.
Array: A complete PV power- generating unit consisting of a number of individual electrically and mechanically integrated modules with structural supports, trackers, or other components.
Array Tilt Angle: The vertical angle between horizontal and the array surface.
Authority Having Jurisdiction (AHJ): An organization, office, or individual designated by local government with legal powers to administer, interpret, and enforce building codes.
Autonomy: The amount of time a fully charged battery system can supply power to system loads without further charging.
B
Bimodal System: A PV system that can operate in either utility-interactive or stand-alone mode, and uses battery storage.
C
Combiner Box: A junction box used as the parallel connection point for two or more circuits.
D
Design Load: A calculated structural load used to evaluate the strength of a structure to failure.
Direct Current (DC): Electrical current that flows in one direction, either positive or negative.
Direct Mount: A type of fixed-tilt array mounting system where modules are affixed directly to an existing finished rooftop or other building surface, with little or no space between a module and the surface.
Disconnect: A device used to isolate equipment and conductors from sources of electricity for the purpose of installation, maintenance, or service.
Dual Metering: The arrangement that measures energy exported to and imported from the utility grid separately.
E
Efficiency: The ratio of power output to power input.
Energy Audit: A collection of information about a facility's energy use.
F
Fixed-Tilt Mounting System: An array mounting system that permanently secures modules in a nonmovable position at a specific tilt angle.
Flat-Plate Collector: A solar energy collector that absorbs solar energy on a flat surace without concentrating it, and can utilize solar radiation directly from the sun as well as diffuse radiation that is reflected or scattered by clouds and other surfaces.
H
H-Bridge Inverter Circuit: A circuit that switches DC input into square wave AC output by using two pairs of switching devices.
Hybrid Battery: A battery that uses a combination of plate designs to maximize the desirable characteristics of each.
I
Isolation: The solar irradiation received over a period of time, typically one day.
Interconnection Agreement: A contract between a distributed-power producer and an electrical utility that established the terms and conditions for the interconnection.
Inverter: A device that converts DC power to AC power.
L
Load: A piece of equipment that consumes electricity.
M
Maintenance Cost: An expense related to the operation and maintenance of a system.
Maintenance Plan: A checklist of all required regular maintenance tasks and their recommended intervals.
Module: A PV device consisting of a number of individual cells connected electrically, laminated, encapsulated, and packaged into a frame.
N
Net Metering: A metering arrangement where any excess energy exported to the utility is subtracted from the amount of energy imported from it.
P
Peak Sun Hours: The number of hours required for a day's total solar irradiation to accumulate at peak sun condition.
Photovoltaic Cell: A semiconductor device that converts solar radiation into direct current electricity.
Photovoltaics: A solar energy technology that uses unique properties of semiconductors to directly convert solar radiation into electricity.
Photovoltaic (PV) System: An electrical system consisting of a PV module array and other electrical components needed to convert solar energy into electricity usable by loads.
Point of Connection: The location at which an interactive distributed-generation system makes its interconnection with the electric utility system.
PV Output Circuit: The circuit connecting the PV power source to the rest of the system.
PV Source Circuit: The circuit connecting a group of modules together and to the common connection point of the DC system.
R
Renewable Energy Certificate (REC): A tradable commodity that represents a certain amount of electricity generated from renewable resources.
S
Short-Circuit Current: The maximum current on an I-V curve and is the operating point of a PV device under no load or short-circuit condition, and no voltage output.
Site Survey: A visit to the installation site to assess the site conditions and establish the needs and requirements for a potential PV system.
Soiling: The accumulation of dust and dirt on an array surface that shades the array and reduces electrical output.
Solar Altitude Angle: The vertical angle between the sun and the horizon.
Solar Irradiance: The power of solar radiation per unit area.
Solar Irradiation: The total amount of solar energy accumulated on an area over time.
Stand-Alone PV System: A type of PV system that operates autonomously and supplies power to electrical loads independently of the electric utility.
Surge Arrestor: A device that protects electrical devices from transients (voltage spikes).
T
Tax Incentive: A measure to reduce owed taxes as an inducement for investment.
U
Utility-Interactive System: A PV system that operates in parallel with and is connected to the electric utility grid.
Z
Zenith: The point in the sky directly overhead a particular location.
