Solar array = Any number of Photovoltaic modules connected together electrically in a combination of series and parallel installed on a mechanical structure. The output from
Solar Efficiency = The ratio of the electric power produced by a photovoltaic device to the power of the sunlight incident on the device. Measured in Percentage.
Spectral irradiance = The spectral irradiance as a function of photon wavelength (or energy), denoted by F, is the most common way of characterising a light source. It gives the power density at a particular wavelength. The units of spectral irradiance are in Wm-2µm-1. The Wm-2 term is the power density at the wavelength λ(µm). Therefore, the m-2 refers to the surface area of the light emitter and the µm-1 refers to the wavelength of interest.
In the analysis of solar cells, the photon flux is often needed as well as the spectral irradiance. The spectral irradiance can be determined from the photon flux by converting the photon flux at a given wavelength to W/m2
Scheduling = The general practice of ensuring that a generator is committed and available when needed. It also can refer to scheduling of imports or exports of energy into or out of a balancing area.
Sealed (SMF) battery = A sealed battery which does not require water topping up and hence making it maintenance free. Also called a valve regulated battery. Usually the popular version is a VRLA battery.
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.
Series connection = A way of joining photovoltaic cells by connecting positive leads to negative leads; such a configuration increases the voltage.
Short-circuit current (Isc) = The current flowing freely through an external circuit that has no loador 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.
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 axis tracking = A photovoltaic array tracking system capable of rotating independently in a
single axis. It is basically a mechanical structure having other devices such as motors, drives, sensors, actuators, etc.
Smart grid = An intelligent electric power system that regulates the two-way flow of electricity and information between power plants and consumers to control grid activity.
Solar cell = The smallest semiconductor element within a PV module to perform the immediate conversion of light into electrical energy (direct current voltage and current).
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 controller = See charge controller.
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 kit = A combination of the critical items in a solar system consisting of a pre-designed solar system which is ready to install at site. Available in different combinations to meet any kind of solar system requirement such as grid tied systems, battery based systems, hybrid systems, pumping systems, etc.
Solar mounting structure = This refers to the mechanical structure used in solar photovoltaic systems to hold the solar modules. The solar mounting structures should ideally be made of a weather resistant material like Galvanized Iron (GI) or Anodized aluminium or other similar weather resistant materials.
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.
Spinning reserve = Electric power plant or utility capacity on-line and running at low power in excess of actual load.
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.
SSL = Solar LED based street lighting models from Novergy. They include the solar module, solar controller, battery, etc. They are having various features such as automatic dusk to dawn capabilities and many protection features such as battery deep discharge and overcharging protection
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.
STC (standard test conditions) = Conditions under which a module is typically tested in a laboratory. Typical STC conditions are Solar radiation of 1000 W/m2, AM of 1 and temperature of 25 Deg C.
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.
String = A number of photovoltaic modules or panels interconnected electrically in series to produce the operating voltage required by the load.
String inverters = A term used to describe a category of solar grid-tie inverters in lower power ratings. Typically models with power rating lower than 80kw are called as string inverters.
Substrate = The physical material upon which a photovoltaic cell is applied.
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 1.5 to 3 times the rated power, that can be provided over a short time by a solar Inverter. Sometimes the inverter may have different surge ratings for different durations (eg. For 30sec, 5sec, 30 cycles, etc)
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 maximum 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. Usually on-grid systems operate on either 600VDC or 1000VDC. Nowadays systems are also available in higher voltages such as 1500VDC.