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Stylized Text: Glossary.

Activation Voltage(s):

The voltage(s) at which the controller will take action to protect the batteries.



Amperage interrupt capability. DC fuses should be rated with a sufficient AIC to interrupt the highest possible load.


Alternating Current (AC):

Electrical current (flow of electrons) in which the direction of flow is reversed at constant intervals, such as 60 cycles per second.



A collection of photovoltaic modules electrically wired together in one structure to produce a specific amount of power.


British Thermal Unit (Btu):

The quantity of heat needed to raise the temperature of 1 pound of water by 1°F at or near 39.2°F.


Centrifugal Pump (rotating pump):

A water pump using a rotating element or screw to move water. The faster the rotation, the greater the flow.


Charge Controller:

A component of a photovoltaic system that controls the flow of current to and from the battery subsystem to protect batteries from overcharge, over discharge, or other control functions. The charge controller may also monitor system operational status.



The production of electricity and another form of useful energy (such as heat or steam) used for industrial, commercial, heating, or cooling purposes.


Commercial Building:

A building with more than 50 percent of its floor space used for commercial activities. Commercial buildings include stores, offices, schools, churches, gymnasiums, libraries, museums, hospitals, clinics, warehouses, and jails. Government buildings are also included, except buildings on military bases or reservations.


Commercial Sector:

Business establishments that are not engaged in transportation or in manufacturing or other types of industrial activity (agriculture, mining, or construction). Commercial establishments include hotels, motels, restaurants, wholesale businesses, retail stores, laundries, and other service enterprises; religious and nonprofit organizations; health, social, and educational institutions; and federal, state, and local governments. Street lights, pumps, bridges, and public services are also included if the establishment operating them is considered commercial.


Conversion Factor:

A number that translates units of one system into corresponding values of another system. Conversion factors can be used to translate physical units of measure for various fuels into Btu equivalents.


Direct Current (DC):

Electric current (flow of electrons) in which the flow is in only one direction.


Displaced or Volumetric Pump:

A type of water pump that utilizes a piston, cylinder and stop valves to move packets of water.


District Heat:

Steam or hot water from an outside source used as an energy source in a building. The steam or hot water is produced in a central plant and is piped into the building. District heat may be purchased from a utility or provided by a physical plant in a separate building that is part of the same facility (for example, a hospital complex or university).


Duty Rating:

The amount of time an inverter (power conditioning unit) can produce at full rated power.


Dynamic Head:

The vertical distance from the center of the pump to the point of free discharge of the water. Pipe friction is included.


Electric Power Plant:

A station containing prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or fission energy into electric energy.


Electricity Generation:

The process of producing electric energy or transforming other forms of energy into electric energy. Also, the amount of electric energy produced or ex pressed in watt-hours (Wh).


End-Use Sectors:

The residential, commercial, industrial, and transportation sectors of the economy.



The capacity for doing work as measured by the capability of doing work (potential energy), or the conversion of this capability to motion (kinetic energy). Energy has several forms, some of which are easily convertible and can be changed to another form useful for work. Most of the world’s convertible energy comes from fossil fuels that are burned to produce heat that is then used as a transfer medium to mechanical or other means in order to accomplish tasks. Electrical energy is usually measured in kilowatt-hours, while heat energy is usually measured in British thermal units.


Energy Consumption:

The use of energy as a source of heat or power or as an input in the manufacturing process.


Energy Density:

The ratio of the energy available from a battery to its volume (wh/m^3) or weight (wh/kg).


Energy Source:

A substance, such as oil, natural gas, or coal, that supplies heat or power. Electricity and renewable forms of energy, such as wood, waste, geothermal, wind, and solar, are considered to be energy sources.



Shipments of goods from the 50 states and the District of Columbia to foreign countries and to Puerto Rico, the Virgin Islands, and other U.S. possessions and territories.


Federal Energy Regulatory Commission (FERC):

The federal agency with jurisdiction over interstate electricity sales, wholesale electric rates, hydroelectric licensing, natural gas pricing, oil pipeline rates, and gas pipeline certification. FERC is an independent regulatory agency within the Department of Energy and is the successor to the Federal Power Commission.


Friction Head:

The energy that must be overcome by the pump to offset the friction losses of the water moving through a pipe.


High Voltage Disconnect Hysteresis:

The voltage difference between the high voltage disconnect set point and the voltage at which the full PV array current will be reapplied.


Independent Power Producer:

Wholesale electricity producers (other than qualifying facilities under the Public Utilities Regulatory Policies Act of 1978) that are unaffiliated with franchised utilities in the area in which the independent power producers are selling power and that lack significant marketing power. Unlike traditional electric utilities, independent power producers do not possess transmission facilities that are essential to their customers and do not sell power in any retail service territory where they have a franchise.


Industrial Sector:

Manufacturing industries, which make up the largest part of the sector, along with mining, construction, agriculture, fisheries, and forestry. Establishments in this sector range from steel mills, to small farms, to companies assembling electronic components.



The amount of energy in sunlight reaching an area. Usually expressed in watts per square meter (W/m^2), but also expressed on a daily basis as watts per square meter per day (W/m^2/day).



Any device or appliance in an electrical circuit that uses power, such as a light bulb.


Low Voltage Disconnect Hysteresis:

The voltage difference between the low voltage disconnect set point and the voltage at which the load will be reconnected.


Low Voltage Warning:

A warning buzzer or light that indicates the low battery voltage set point has been reached.



A number of photovoltaic cells wired together to form a unit, usually in a sealed frame of convenient size for handling and assembling into arrays. Also called a panel.



Metal Oxide Varistor. Used to protect electronic circuits from surge currents such as produced by lighting.



National Electrical Manufacturers Association. This organization sets standards for some non-electronic products like junctions boxes.


North American Electric Reliability Council (NERC):

A council formed in 1968 by the electric utility industry to promote the reliability and adequacy of bulk power supply in the electric utility systems of North America. The NERC consists of ten regional reliability councils and encompasses essentially all the power systems of the contiguous United States and Canada.


Organization for Economic Cooperation and Development (OECD):

Current members are Australia, Austria, Belgium, Canada, Czech Republic, Denmark and its territories (Faroe Islands and Greenland), Finland, France, Germany, Greece, Greenland, Hungary, Iceland, Ireland, Italy, Japan, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, South Korea, Spain, Sweden, Switzerland, Turkey, United Kingdom, and United States and its territories (Guam, Puerto Rico, and Virgin Islands).


Organization of Petroleum Exporting Countries (OPEC):

Countries that have organized for the purpose of negotiating with oil companies on matters of oil production, prices, and future concession rights. Current members are Algeria, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, United Arab Emirates, and Venezuela.


Outgas (gassing):

Gas by-products, primarily hydrogen, produced when charging a battery. Also, termed out-gassing.


Peak Sun Hours:

The equivalent number of hours when solar insolation averages 1000 watts per square meter and produces the same total insolation as actual sun conditions.


Photovoltaic Energy:

Direct-current electricity generated from sunlight through solid-state semiconductor devices that have no moving parts.


Photovoltaic (PV) System:

A complete set of interconnect components for converting sunlight into electricity by the photovoltaic process, including array, balance-of-system components, and the load.



An instrument used for measuring direct beams of solar irradiance. Uses an aperture of 5.7 deg. to transcribe the solar disc.


Renewable Energy:

Energy obtained from sources that are essentially inexhaustible (unlike, for example, fossil fuels, of which there is a finite supply). Renewable sources of energy include conventional hydroelectric power, wood, waste, geothermal, wind, photovoltaic, and solar thermal energy.


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 AC current, I, that will produce the same heating in a conductor with resistance, R, as a DC current of value I.the corrosion of the protected structure.


Static Head:

The vertical distance from the water level to the point of free discharge of the water. It is measured when the pump is not operating.


Sacrificial Anode:

A piece of metal buried near a structure that is to be protected from corrosion. The metal of the sacrificial anode is intended to corrode and reduce the corrosion of the protected structure.


Solar Insolation (Insolation):

The solar radiation incident on an area over time. Equivalent to energy and usually expressed in kilowatt-hours per square meter.



Supplies of fuel or other energy source(s) stored for future use. Stocks are reported as of the end of the reporting period.



This term has dual meaning for water pump systems. Storage can be achieved by pumping water to a storage tank, or storing energy in a battery subsystem.


Suction Head:

The vertical distance from the surface of the water source to the center of the pump (when the pump is located above the water level).


TC, TW, THHN, UF, USE (Wire Types):

See article 300 of National Electric Code for more information.


Transportation Sector:

Private and public vehicles that move people and commodities. Included are automobiles, trucks, buses, motorcycles, railroads, and railways (including streetcars), aircraft, ships, barges, and natural gas pipelines.



A voltage-dependant variable resistor. Normally used to protect sensitive equipment from power spikes or lightning strikes by shunting the energy to ground.


Voltage (V):

A measure of the force or "push" given the electrons in an electrical circuit; a measure of electrical potential. One volt produces one amp of current when acting against a resistance of one ohm.


Watt (W):

A measure of electrical power or amount of work done in a unit of time and equal to the rate of current flow (amps) multiplied by the voltage of that flow (volts). One amp of current flowing at a potential of one volt produces one watt of power.


Wind Energy:

The kinetic energy of wind converted into mechanical energy by wind turbines (i.e., blades rotating from a hub) that drive generators to produce electricity.