A | B | C| D | E | F | G | H | I | J | K| L | M | N | O | P | Q | R | S | T | U | V | W| X | Y | Z
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AC |
Alternating Current, the standard form of electrical current supplied by the utility grid and by most fuel-powered generators. The polarity (and therefore the direction of current) alternates. In U.S.A., standard voltages for small water pumps are 115V and 230V. Standards vary in different countries. See inverter.
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Converter |
An electronic device for DC power that steps up voltage and steps down current proportionally (or vice-versa). Electrical analogy applied to AC: See transformer. Mechanical analogy: gears or belt drive.
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Current |
The rate at which electricity flows through a circuit, to transfer energy. Measured in Amperes, commonly called Amps. Analogy: Flow Rate in a water pipe.
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DC |
Direct Current, the type of power produced by photovoltaic panels and by storage batteries. The current flows in one direction and polarity is fixed, defined as positive (+) and negative (-). Nominal system voltage may be anywhere from 12 to 180V. See voltage, nominal.
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Efficiency |
The percentage of power that gets converted to useful work. Example: An electric pump that is 60% efficient converts 60% of the input energy into work - pumping water. The remaining 40% becomes waste heat.
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Energy |
The product of power and time, measured in Watt-Hours. 1000 Watt-Hours = 1 Kilowatt-Hour (abbreviation: KWH). Variation: the product of current and time is Ampere-Hours, also called Amp-Hours (abbreviation: AH). 1000 watt consumed for 1 hour = 1 KWH. See power.
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Inverter |
An electronic device that converts low voltage DC to high voltage AC power. In solar-electric systems, an inverter may take the 12, 24, or 48 volts DC and convert it to 115 or 230 volts AC, conventional household power.
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Photovoltaic |
The phenomenon of converting light to electric power. Photo = light, Volt = electricity. Abbreviation: PV. PV - The common abbreviation for photovoltaic.
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Power |
The rate at which work is done. It is the product of Voltage times Current, measured in Watts. 1000 Watts = 1 Kilowatt. An electric motor requires approximately 1 Kilowatt per Horsepower (after typical efficiency losses). 1 Kilowatt for 1 Hour = 1 Kilowatt-Hour (KWH).
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PV Array |
A group of PV (photovoltaic) modules (also called panels) arranged to produce the voltage and power desired.
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PV Array-Direct |
The use of electric power directly from a photovoltaic array, without storage batteries to store or stabilize it. Most solar water pumps work this way, utilizing a tank to store water.
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PV Cell |
The individual photovoltaic device. The most common PV modules are made with 33 to 36 silicon cells each producing 1/2 volt.
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PV Module |
An assembly of PV cells framed into a weatherproof unit. Commonly called a "PV panel". See PV array.
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Solar Tracker |
A mounting rack for a PV array that automatically tilts to follow the daily path of the sun through the sky. A "tracking array" will produce more energy through the course of the day, than a "fixed array" (non-tracking) particularly during the long days of summer.
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Transformer |
An electrical device that steps up voltage and steps down current proportionally (or vice-versa). Transformers work with AC only. For DC, see converter. Mechanical analogy: gears or belt drive.
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Utility Grid |
Commercial electric power distribution system. Synonym: mains.
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Voltage |
The measurement of electrical potential. Analogy: Pressure in a water pipe.
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Voltage Drop |
Loss of voltage (electrical pressure) caused by the resistance in wire and electrical devices. Proper wire sizing will minimize voltage drop, particularly over long distances. Voltage drop is determined by 4 factors: wire size, current (amps), voltage, and length of wire. It is determined by a consulting wire sizing chart or formula available in various reference tests. It is expressed as a percentage. Water analogy: Friction Loss in pipe.
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Voltage, Nominal |
A way of naming a range of voltage to a standard. Example: A "12 Volt Nominal" system may operate in the range of 11 to 15 Volts. We call it "12 Volts" for simplicity.
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Voltage, Open Circuit |
The voltage of a PV module or array with no load (when it is disconnected). A "12 Volt Nominal" PV module will produce about 20 Volts open circuit. Abbreviation: Voc.
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Voltage, Peak Power Point |
The voltage at which a photovoltaic module or array transfers the greatest amount of power (watts). A "12 Volt Nominal" PV module will typically have a peak power voltage of around 17 volts. A PV array-direct solar pump should reach this voltage in full sun conditions. In a higher voltage array, it will be a multiple of this voltage. Abbreviation: Vpp.
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