Solar Dictionary: Solar Electric (Photovoltaic) Terms
AC Disconnect one of the balance of system components, this utility serviceable disconnect switch allows the current being produced from the photovoltaic system to be isolated from the utility feed during times of maintenance, service or repair.
Solar Electric
Alternating Current (AC) the type of current that most utility interconnected homes and commercial structures run on. The direction of this type of current reverses at regular intervals usually 120-reversals or 60-cycles per minute making it easy for the utility providers to control.
Solar Electric
Ampere (A) a unit of electrical current which measures the flow of electrons (similar to the measure of flow rate of water through a hose).
Solar Electric
Amp-hour Capacity (Ah/AM) referring to the size of a battery, this is a measurement of the flow of current per hour.
Solar Electric
Angle Of Incidence the angle at which solar radiation strikes a surface (collector).
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Array a group of thermal collectors or photovoltaic modules organized to produce a desired amount of energy.
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Balance of System Components all components of a solar system other than the actual array (includes everything from design costs through installation and service/maintenance).
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Battery Back-up a photovoltaic system designed with batteries of a specified amp-hour capacity to provide current to a residential or commercial structure or its key loads for a predetermined period of time.
Solar Electric
Charge Controller utilized only in systems which incorporate batteries, this component controls the flow of current to and from the batteries to protect them from over-charging and over-discharging.
Solar Electric
Current the flow of electrical energy measured in amperes (A)
Solar Electric
DC Disconnect a disconnect switch which isolates the photovoltaic array from the other system components during times of maintenance/service.
Solar Electric
Direct Current (DC) a type of electricity which flows through a conductor in only one direction with low voltage and high current. Most standard appliances will not work on DC, so the electricity must be inverted to AC.
Solar Electric
Grid-tied the photovoltaic system that is connected to the utility grid allowing the system and the grid to interact (allows for net-metering).
Solar Electric
Insolation the total amount of solar radiation - direct, diffused, and reflected - striking a surface exposed to the sky
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Inverter the component of a photovoltaic system which changes DC to AC (essential in both grid-tied and stand-alone systems).
Solar Electric
Junction Box (PV) an enclosure on the back of a module where photovoltaic modules are connected to form a string.
Solar Electric
Junction Box (roof) an enclosure mounted near the array where strings come together to be run to the inverter.
Solar Electric
Kilowatt (kW) a unit of electrical power; equals 1000-watts
Solar Electric
Kilowatt-hour (kW h) a unit of energy; equals 1000-watts acting over one hour.
Solar Electric
Magnetic South the direction on a compass pointing due-South, away from the North Pole.
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Megawatt (MW) a unit of electrical power; equals 1000-kilowatts
Solar Electric
Module a collection of photovoltaic cells connected together, as well as other components (i.e. junction box, frame, wires, etc.), designed to produce a specified number of watts under standard test conditions (STC). Also referred to as a solar panel.
Solar Electric
NABCEP North American Board of Certified Energy Professionals, organization providing certification of solar installers
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National Electric Code (NEC) the guidelines for all types of electrical installations.
Solar Electric
Net-metering an agreement with the utility provider which allows grid-tied systems to back-feed the grid during times when production exceeds usage. During these times the utility meter actually runs backwards, creating a "debit and credit" situation between the producer and the utility provider.
Solar Electric
Orientation the direction that a solar array faces with regard to magnetic directions (N, E, S, W).
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Photovoltaics (PV) the conversion of light into electricity.
Solar Electric
Racking (rails) the components used to secure a domestic hot water, pool, or photovoltaic system in place; can be ground, deck, roof or pole mounted depending on the application and the orientation of available space.
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Radiation the flow of energy across open space via electromagnetic waves, such as visible light
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Resistance (R) a unit measured in ohms, it is the opposition to the flow of electrons produced by a conductor.
Solar Electric
Solar Access the amount of sunlight a photovoltaic array should receive based upon orientation, obstructions and average annual sun hours.
Solar Electric
Solar Cell the smallest element in a solar module, it is directly responsible for the conversion of light into electricity. Usually made of mono- or poly-crystalline or amorphous silicone.
Solar Electric
Solar Index the ratio of measured solar radiation to an expected number if the sky is clear, with an average clear sky day being 100%
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Solar Noon the time the sun crosses the meridian of the site, this is the highest point the sun gets in a day. Also referred to as Solar South
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Solar South see 'Solar Noon'
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SRCC Solar Rating and Certification Committee. Organization that rates collector and system performance.
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Standard Test Conditions (STC) conditions under which a module is tested in a laboratory; each manufacturer has slightly different STC's, but most center around the following criteria: 25 degrees Celsius, 1.5 atmospheres of air pressure and 1000-watts per square meter of light energy.
Solar Electric
Tilt Angle the angle a collector or module surface forms with the horizon
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Volts (V) the unit that measures electrical force (the force required for one amp to flow through a resistance of one ohm).
Solar Electric
Watt (W) the basic unit of electrical power.
Solar Electric