English Glossary

Since 02.06.2017

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specific power of wind turbines

Rated power of generator (W) / rotor swept area (m2).

spinning reserve

The difference between the total available capacity of all fossil fuelled power generators already coupled to the power system and their actual loading.


A party wishing to develop and finance (with equity) a project. Shareholders of project companies are known as sponsors.

spot market

The market for buying and selling a specific commodity, foreign currency, or asset at the prevailing price for immediate delivery.

spot price

The current market price of the actual physical commodity. Also called the cash price.


Small Power Producer

spread-skill relationship

For ensemble prediction the spread between the ensemble members gives a hint to the skill (accuracy) of the prediction. At higher spreads a larger forecast error is more likely.


special purpose vehicle

squirrel cage induction generator

SCIG - induction generator in which the rotor shape is a cylinder mounted on a shaft. Internally it contains longitudinal conductive bars (usually made of aluminum or copper) set into grooves and connected at both ends by shorting rings forming a cage-like shape. In wind turbine technology it is often referred to as a IEC Type 1 machine.


spinning reserve


Shuttle Radar Topography Mission


Stability of a power system refers to the abilitiy to continue intact operation following a disturbance.


An equilibrium state reached in a solar thermal collector (energy captured equals energy lost) during periods of continuous high solar irradiation without consumption

stagnation temperature

The solar thermal collector temperature at which stagnation occurs


Description of the aerodynamical effect that the air stream around an airfoil (e.g. rotor blade) breaks away and which results in a reduction of the lift coefficient

stall control

Power limitation method in a wind turbine. Stalling works by increasing the angle at which the relative wind strikes the blades (angle of attack), and it reduces the induced drag (drag associated with lift). Stall controlled rotors are generally operated at two speeds.

stand-alone PV System

A photovoltaic system that operates independent of the utility grid, an off-grid PV system.

stand-alone system

A power source/generator that operates independently of or is not connected to an electric transmission and distribution network; used to meet a load(s) physically close to the generator. (Syn. Off-grid system)

standard deviation

SD - a measure that is used to quantify the amount of variation or dispersion of a set of data values from the average value.

standard test conditions

STC - accepted standard for controlled laboratory testing and certification of PV cells and module output. Standard Test Conditions are defined as 1,000 W/m2 of light intensity with a replicated solar spectrum of AM 1.5 and 25°C cell (or module) temperature.

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