Glossary

SOLAR TERMINOLOGY – GLOSSARY AND DEFINITIONS

• 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.

• Amorphous - There are two main types of solar panel: amorphous and crystalline. In general, amorphous perform better than crystalline under low light conditions and don’t suffer as much power loss in hot temperatures. However, in good conditions, the efficiency of amorphous panels is lower, and they are physically larger than crystalline panels of the same wattage.

• Amp Hour (Ah) - Measures a battery's total capacity. The higher the number, the larger the battery's capacity.

• Amps - Measures the strength of an electrical current.

• Blocking Diode - At night a blocking diode prevents the solar panel from acting as a power drain on your battery. Charge controllers (or regulators) include a feature that does the same job as a blocking diode.

• Bypass Diodes - These are placed within some solar panels at the manufacturing stage. If the solar panel is partly in shadow, bypass diodes prevent the shadowed cells from acting as a power drain on those cells still in the sunlight.

• 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.

• Crystalline - Crystalline silicon is generally either Mono-crystalline or Poly-crystalline.  These solar panels tend to be rigid, aluminium framed and glass fronted.  In good conditions they can be more efficient and physically smaller than amorphous panels of the same wattage.

• Current - measured in Amps (I), is the system power divided by system voltage. I = W / V.

• 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.

• 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.

• 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.

• Efficiency - The ratio of sunlight power hitting the solar cell to the electrical power it produces. Mono-Crystalline efficiency is in the region of 14% to 18%.

• 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.

• Environmentally friendly - Inflicting minimum harm on the environment.

• Flexible panel - The solar amorphous panel is usually mounted onto a thin metal or plastic backing and sealed at the edges using a pliable material, thus allowing the panel to be slightly bent.

• Framed panel - Solar panel mounted onto a thin metal backing plate which is then mounted into an aluminium frame that can be used to attach the solar panel to a building, roof or other structure.

• Green energy - Energy produced in way that is sympathetic to the environment, producing less pollutants such as carbon emissions.

• Insolation - The amount (and type) of light defined below, falling on the surface of a solar cell.

• 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.

• Ip - The current of the panel at peak power output.

• Isc - Short circuit Current = maximum current that the panel can generate (very little voltage).

• Milli Amp hour (mAh) - Measures a battery's total capacity. The higher the number, the larger the battery's capacity.

• NOCT - Normal Operating Cell Temperature = the temperature at which a cell operates with full sunlight falling on its surface (and therefore heating it).

• Open-circuit voltage - The open circuit voltage is the maximum voltage that the panel can produce. The panel is not producing its maximum power output when giving this voltage.

• Photovoltaic - Photovoltaic (PV) technology converts sunlight into electricity. Often referred to as PV for short, photo means 'light' and 'voltaic' means electric.

• Photovoltaic - The name given to the process of converting radiation (especially light) directly into electricity. As in this document, the term 'solar' is commonly used to refer to what should strictly be called photovoltaic.

• Photovoltaic - The phenomenon of converting light to electric power. Photo = light, Volt = electricity. Abbreviation: PV. PV - The common abbreviation for photovoltaic.

• Power - measured in Watts (W), is the system voltage multiplied by system current. W = V x I.

• 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).

• PV Array - A group of PV (photovoltaic) modules (also called panels) arranged to produce the voltage and power desired.

• 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.

• PV Cell - The individual photovoltaic device. The most common PV modules are made with 33 to 36 silicon cells each producing 1/2 volt.

• PV Module - An assembly of PV cells framed into a weatherproof unit. Commonly called a "PV panel". See PV array.

• Rated Power - The amount of electrical power produced by a solar panel when exposed to sunlight at an intensity of 1000W per meter squared. The rated power is measured in Watts.

• Renewable energy - Energy obtained from inexhaustible sources, such as solar energy and wind power.

• Rollable panel - The solar amorphous panel is mounted onto a plastic backing, and can be usually rolled to a diameter of around 8 inches or 20cm. The panel needs to be rolled with the solar cells on the outside.

• Short-circuit current - The short circuit current is the maximum possible current that the panel can produce. The panel is not producing its maximum power output when giving this current.

• Solar - Utilising the sun's energy or derived from the sun.

• Solar array - A collection of two or more solar modules.

• Solar cell - A semi-conducting material that converts light to DC electricity. It is the smallest generating element of a PV system.

• Solar cell - The smallest single solar electric generating device.

• Solar energy -Thermal energy or electricity created from the sun's radiation.

• Solar panel - A collection of solar cells that convert the sun's energy into electricity.

• Solar panel - A collection of two or more cells; also referred to as a solar module. With TFS, the cells are connected in series during the production process.

• Solar power - Energy harnessed from the sun's light.

• 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.

• 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.

• triple junction - Triple junction is the term used to describe the amorphous panel technology that is sensitive to three wavelengths of light. This gives the these panels a wider operating range.

• Utility Grid - Commercial electric power distribution system. Synonym: mains.

• Vnom - Nominal voltage = the voltage at which the solar cell or panel is designed to operate at.

• Voc - Open circuit voltage = maximum voltage that the panel can generate (very little current).

• Voltage - measured in Volts (V), is the system power divided by system current. V = W / I.

• Voltage - The measurement of electrical potential. Analogy: Pressure in a water pipe.

• 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.

• 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.

• 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.

• 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.

• Volts - Measures the “pressure” in an electrical circuit between two points.

• Vp - The voltage of the panel at peak (maximum) power output.

• Watts - Measures total electrical power. Watts=Volts x Amps.

• Wp - The peak power that a solar cell/panel can produce.