Solar Technology related terms beginning with S.
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- 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.
- Satellite Power System (SPS) : Concept for providing large amounts of electricity for use on the Earth from one or more satellites in geosynchronous Earth orbit. A very large array of solar cells on each satellite would provide electricity, which would be converted to microwave energy and beamed to a receiving antenna on the ground. There, it would be reconverted into electricity and distributed the same as any other centrally generated power, through a grid.
- Schottky Barrier : A cell barrier established as the interface between a semiconductor, such as silicon, and a sheet of metal.
- Scribing : The cutting of a grid pattern of grooves in a semiconductor material, generally for the purpose of making interconnections.
- Sealed Battery : A battery with a captive electrolyte and a resealing vent cap, also called a valve-regulated battery. Electrolyte cannot be added.
- Seasonal Depth of Discharge : An adjustment factor used in some system sizing procedures which "allows" the battery to be gradually discharged over a 30-90 day period of poor solar insolation. This factor results in a slightly smaller photovoltaic array.
- Secondary Battery : A battery that can be recharged.
- Self-Discharge : The rate at which a battery, without a load, will lose its charge.
- Semiconductor : Any material that has a limited capacity for conducting an electric current. Certain semiconductors, including silicon, gallium arsenide, copper indium diselenide, and cadmium telluride, are uniquely suited to the photovoltaic conversion process.
- Semicrystalline : See Multicrystalline.
- Series Connection : A way of joining photovoltaic cells by connecting positive leads to negative leads; such a configuration increases the voltage.
- Series Controller : A charge controller that interrupts the charging current by open-circuiting the photovoltaic (PV) array. The control element is in series with the PV array and battery.
- Series Regulator : Type of battery charge regulator where the charging current is controlled by a switch connected in series with the photovoltaic module or array.
- Series Resistance : Parasitic resistance to current flow in a cell due to mechanisms such as resistance from the bulk of the semiconductor material, metallic contacts, and interconnections.
- Shallow-Cycle Battery : A battery with small plates that cannot withstand many discharges to a low state-of-charge.
- Shelf Life of Batteries : The length of time, under specified conditions, that a battery can be stored so that it keeps its guaranteed capacity.
- Short-Circuit Current (Isc) : The current flowing freely through an external circuit that has no load or resistance; the maximum current possible.
- Shunt Controller : A charge controller that redirects or shunts the charging current away from the battery. The controller requires a large heat sink to dissipate the current from the short-circuited photovoltaic array. Most shunt controllers are for smaller systems producing 30 amperes or less.
- Shunt Regulator : Type of a battery charge regulator where the charging current is controlled by a switch connected in parallel with the photovoltaic (PV) generator. Shorting the PV generator prevents overcharging of the battery.
- Siemens Process : A commercial method of making purified silicon.
- Silicon (Si) : A semi-metallic chemical element that makes an excellent semiconductor material for photovoltaic devices. It crystallizes in face-centered cubic lattice like a diamond. It's commonly found in sand and quartz (as the oxide).
- Sine Wave : A waveform corresponding to a single-frequency periodic oscillation that can be mathematically represented as a function of amplitude versus angle in which the value of the curve at any point is equal to the sine of that angle.
- Sine Wave Inverter : An inverter that produces utility-quality, sine wave power forms.
- Single-Crystal Material : A material that is composed of a single crystal or a few large crystals.
- Single-Crystal Silicon : Material with a single crystalline formation. Many photovoltaic cells are made from single-crystal silicon.
- Single-Stage Controller : A charge controller that redirects all charging current as the battery nears full state-of-charge.
- Solar Cell : see photovoltaic (PV) cell.
- Solar Constant : The average amount of solar radiation that reaches the earth's upper atmosphere on a surface perpendicular to the sun's rays; equal to 1353 Watts per square meter or 492 Btu per square foot.
- Solar Cooling : The use of solar thermal energy or solar electricity to power a cooling appliance. Photovoltaic systems can power evaporative coolers ("swamp" coolers), heat-pumps, and air conditioners.
- Solar Energy : Electromagnetic energy transmitted from the sun (solar radiation). The amount that reaches the earth is equal to one billionth of total solar energy generated, or the equivalent of about 420 trillion kilowatt-hours.
- Solar-Grade Silicon : Intermediate-grade silicon used in the manufacture of solar cells. Less expensive than electronic-grade silicon.
- Solar Insolation : See insolation.
- Solar Irradiance : See irradiance.
- Solar Noon : The time of the day, at a specific location, when the sun reaches its highest, apparent point in the sky; equal to true or due, geographic south.
- Solar Panel : See photovoltaic (PV) panel.
- Solar Resource : The amount of solar insolation a site receives, usually measured in kWh/m2/day, which is equivalent to the number of peak sun hours.
- Solar Spectrum : The total distribution of electromagnetic radiation emanating from the sun. The different regions of the solar spectrum are described by their wavelength range. The visible region extends from about 390 to 780 nanometers (a nanometer is one billionth of one meter). About 99 percent of solar radiation is contained in a wavelength region from 300 nm (ultraviolet) to 3,000 nm (near-infrared). The combined radiation in the wavelength region from 280 nm to 4,000 nm is called the broadband, or total, solar radiation.
- Solar Thermal Electric Systems : Solar energy conversion technologies that convert solar energy to electricity, by heating a working fluid to power a turbine that drives a generator. Examples of these systems include central receiver systems, parabolic dish, and solar trough.
- Space Charge : See cell barrier.
- Specific Gravity : The ratio of the weight of the solution to the weight of an equal volume of water at a specified temperature. Used as an indicator of battery state-of-charge.
- Spinning Reserve : Electric power plant or utility capacity on-line and running at low power in excess of actual load.
- 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. See mulitjunction device.
- Sputtering : A process used to apply photovoltaic semiconductor material to a substrate by a physical vapor deposition process where high-energy ions are used to bombard elemental sources of semiconductor material, which eject vapors of atoms that are then deposited in thin layers on a substrate.
- Square Wave : A waveform that has only two states, (i.e., positive or negative). A square wave contains a large number of harmonics.
- Square Wave Inverter : A type of inverter that produces square wave output. It consists of a direct current source, four switches, and the load. The switches are power semiconductors that can carry a large current and withstand a high voltage rating. The switches are turned on and off at a correct sequence, at a certain frequency.
- Staebler-Wronski Effect : The tendency of the sunlight to electricity conversion efficiency of amorphous silicon photovoltaic devices to degrade (drop) upon initial exposure to light.
- Stand-Alone System : An autonomous or hybrid photovoltaic system not connected to a grid. May or may not have storage, but most stand-alone systems require batteries or some other form of storage.
- Stand-Off Mounting : Technique for mounting a photovoltaic array on a sloped roof, which involves mounting the modules a short distance above the pitched roof and tilting them to the optimum angle.
- Standard Reporting Conditions (SRC) : A fixed set of conditions (including meteorological) to which the electrical performance data of a photovoltaic module are translated from the set of actual test conditions.
- Standard Test Conditions (STC) : Conditions under which a module is typically tested in a laboratory.
- Standby Current : This is the amount of current (power) used by the inverter when no load is active (lost power). The efficiency of the inverter is lowest when the load demand is low.
- Starved Electrolyte Cell : A battery containing little or no free fluid electrolyte.
- State-of-Charge (SOC) : The available capacity remaining in the battery, expressed as a percentage of the rated capacity.
- Storage Battery : A device capable of transforming energy from electric to chemical form and vice versa. The reactions are almost completely reversible. During discharge, chemical energy is converted to electric energy and is consumed in an external circuit or apparatus.
- Stratification : A condition that occurs when the acid concentration varies from top to bottom in the battery electrolyte. Periodic, controlled charging at voltages that produce gassing will mix the electrolyte. See equalization.
- String : A number of photovoltaic modules or panels interconnected electrically in series to produce the operating voltage required by the load.
- Substrate : The physical material upon which a photovoltaic cell is applied.
- Subsystem : Any one of several components in a photovoltaic system (i.e., array, controller, batteries, inverter, load).
- Sulfation : A condition that afflicts unused and discharged batteries; large crystals of lead sulfate grow on the plate, instead of the usual tiny crystals, making the battery extremely difficult to recharge.
- Superconducting Magnetic Energy Storage (SMES) : SMES technology uses the superconducting characteristics of low-temperature materials to produce intense magnetic fields to store energy. It has been proposed as a storage option to support large-scale use of photovoltaics as a means to smooth out fluctuations in power generation.
- Superconductivity : The abrupt and large increase in electrical conductivity exhibited by some metals as the temperature approaches absolute zero.
- Superstrate : The covering on the sunny side of a photovoltaic (PV) module, providing protection for the PV materials from impact and environmental degradation while allowing maximum transmission of the appropriate wavelengths of the solar spectrum.
- Surge Capacity : The maximum power, usually 3-5 times the rated power, that can be provided over a short time.
- System Availability : The percentage of time (usually expressed in hours per year) when a photovoltaic system will be able to fully meet the load demand.
- System Operating Voltage : The photovoltaic array output voltage under load. The system operating voltage is dependent on the load or batteries connected to the output terminals.
- System Storage : See battery capacity.