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Sacrificial anode |
A piece of metal electrically connected to a buried or submerged structure that is to be protected from corrosion. The metal of the sacrificial anode is selected to corrode preferentially to the metal of the protected structure and so reduce its corrosion rate. |
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SE |
Selective emitter. |
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Sealed battery |
A battery with a captive electrolyte and a re-sealing vent cap to which electrolyte cannot be added. Also called a valve-regulated battery. |
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Sealed lead-acid battery |
A form of lead-acid battery where the electrolyte is immobilized, either by being contained in an absorbent fibre separator or gel between the batteries plates. |
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Secondary battery |
A battery that can be recharged. |
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Self discharge |
Energy lost to internal chemical reactions within the cell. |
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Self discharge rate |
The rate at which a battery will lose its charge when at open circuit (with no load connected). |
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Semiconductor |
A material that has an electrical conductivity in between that of a metal and an insulator. Transistors and other electronic devices are made from semiconducting materials, and are often called semiconductors. Typical semiconductors for PV cells include silicon, gallium arsenide, copper indium diselenide, and cadmium telluride. |
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Series connected |
A method of connection in which the positive terminal of one device is connected to the negative terminal of another. The voltages add and the current is limited to the least of any device in the string. |
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Series regulator |
A type of battery charge controller or regulator in which the charging current is controlled by a switch, transistor, or field-effect transistor connected in series with the PV module or array. |
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Series resistance |
Resistance to current flow within a cell due to factors such as the bulk resistance of the cell materials and contact resistances. |
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Shallow-cycle battery |
A battery with small plates that cannot withstand many deep discharges (i.e. to a low state of charge). |
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Shelf life |
The time for which a device can be stored and still retain its specified performance. |
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Shipments |
The quantity of modules manufacturers sold on an arms length basis to downstream entities. |
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Short circuit current (Isc) |
The current generated by an illuminated solar PV cell, module, or array when its output terminals are shorted; the maximum current possible. |
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Shunt controller |
A controller or regulator that re-directs, or shunts, the charging current away from the battery. Generally used for smaller systems. |
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Si |
Silicon. |
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Silicon (Si) |
A chemical element with atomic number 14, a dark gray semi-metal. Occurs in a wide range of silicate minerals and makes up approximately 28% of the earth's crust (by weight). Silicon has a face-centered cubic lattice structure like diamond. The most common semiconductor material used in making PV cells either traditionally in its crystalline form or more recently as an amorphous thin film. |
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Sine wave |
A waveform that is defined by an equation in which one variable is proportional to the sine of the other, as generated by an oscillator in simple harmonic motion. The sine wave is the most ideal form of electricity for running more sensitive appliances, such as radios, TVs, computers and the like. |
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Sine wave inverter |
An inverter that produces grid-quality, sine wave AC electricity. |
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Single-crystal silicon |
Silicon material with a single crystal structure. A common material for the construction of solar PV cells. |
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Solar constant |
The power density of solar radiation on a plane perpendicular to the direction of the sun at the mean earth-sun distance outside the earth's atmosphere; its value is 1.37 kW per square meter. |
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Solar energy |
Energy from the sun. |
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Solar module |
A device used to convert light from the sun directly into DC electricity by using the photovoltaic effect. Usually made of multiple solar cells bonded between glass and a backing material. A typical solar module has 100 Watts of power output (but module powers can range from 1 Watt to 300 Watts) and dimensions of 2 feet by 4 feet. |
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Solar noon |
The mid-point between sunrise and sunset; the time when the sun reaches its highest point in its daily arc across the sky. |
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Solar power |
Electricity generated by conversion of sunlight, either directly through the use of photovoltaic panels, or indirectly through solar-thermal processes. |
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Solar resource |
The amount of solar insolation received at a site, normally measured in units of kWh/m2/day which equates to the number of peak sun hours. |
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Solar spectrum |
The total distribution of electromagnetic radiation emanating from the sun. |
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Solar thermal |
A form of power generation using concentrated sunlight to heat water or other fluid that may then used to drive a motor or turbine. |
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Solar thermal electric |
Method of producing electricity from solar energy by using focused sunlight to heat a working fluid, which in turn drives a turbogenerator. |
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Solar-grade silicon |
Intermediate-grade silicon used in the manufacture of solar cells. Less expensive than electronic-grade silicon. |
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Specific gravity |
The ratio of the weight of a solution to the weight of an equal volume of water at a specified temperature; used with reference to the sulfuric acid electrolyte solution in a lead acid battery as an indicator of battery state of charge. More recently called relative density. |
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Split-spectrum cell |
A compound photovoltaic device in which sunlight is first divided into spectral regions by optical means. Each region is then directed to a different photovoltaic cell optimized for converting that portion of the spectrum into electricity. Such a device achieves significantly greater overall conversion of incident sunlight into electricity. |
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Square wave |
A train of rectangular voltage pulses that alternate between two fixed values for equal lengths of time. |
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Square wave inverter |
The simplest and the least expensive type of inverter, which produces the lowest quality of power. The inverter uses switches that can carry a large current and withstand a high voltage that are turned on and off in the correct sequence and at a certain frequency. |
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Stand-alone (PV system) |
A solar PV system that operates without connection to a grid supplying electricity. |
