English Glossary

Since 02.06.2017

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active power




per unit


A device that can be run into a wellbore with a smaller initial outside diameter that then expands externally to seal the wellbore.

parabolic trough collector

A CSP technology which uses a long, parabolic-shaped mirror to concentrate solar radiation onto a central receiver tube running along the focal line of the parabolic mirror to produce high temperatures.

pay-back method

A method used to calculate a pay-back period and indicate how long it will take to recover the initial investment cost.

pay-back period

Is defined as the time it takes until the cumulated outgoing cash-flows equal the cumulated incoming cash-flows, i.e. until the project breaks even.


point of common coupling


phase change material


plan-do-check-act approach

peak demand

The highest energy (or power) demand during a specific period (generally, one year).

peak load hours

Hours within a period of time during where the load is highest.

peak power

The amount of electrical power a photovoltaic module will produce at Standard Test Conditions (normally 1,000 W/m2 and 25 ⁰C cell temperature), expressed in units of watt-peak (Wp) or a related unit such as kilowatt-peak (kWp) or megawatt-peak (MWp).

peak sun hours

If a location receives an average 1,200 kWh/m2/year, it is said to receive an average 1,200 PSH per day. If a location receives an average 5 kWh/m2/day, it is said to receive an average 5 PSH per day. A peak sun hour is equivalent to 1000 watts of solar energy falling on an area of 1 square meter for 1 hour or for example as 500 watts of solar energy falling on an area of 1 square meter for 2 hours.


electric power

penstock pipe

A pipe for transporting water to the hydro turbine

performance coefficient

Cp - a non-dimensional value describes the ratio of power that is captured by the wind turbine and fed into the grid. It is used to measure the wind turbine efficiency.

performance ratio

PR -the ratio of actual electricity output from a PV system and possible electricity output under 'ideal' conditions (no losses etc.). Expressed as a factor or a percentage.

permanent magnet synchronous generator

Generator where the excitation field is provided by a permanent magnet instead of a coil.The term synchronous refers here to the fact that the rotor and magnetic field rotate with the same speed, because the magnetic field is generated through a shaft mounted permanent magnet mechanism and current is induced into the stationary armature.

permanent magnetized synchronous generator

PMSG - synchronous generator equipped with an excitation system consisting of permanent magnets.

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