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watt per square metre


weighted average cost of capital

wafer-based PV module

A PV module constructed with silicon wafers. A wafer is a rectangularly-shaped (rarely round) and very thin silicon disc.

waiver of subrogation

An agreement between two parties in which one party agrees to waive subrogation rights against another in the event of a loss. The intent of the waiver is to prevent one party's insurer from pursuing subrogation against the other party. Generally, insurance policies do not bar coverage if an insured waives subrogation against a third party before a loss. However, coverage is excluded from many policies if subrogation is waived after a loss because to do so would violate the principle of indemnity.

wake effect

A wind turbine located downstream of the air flow of another wind turbine 'sees' less wind speed than the first one and consequently produces less power. This is called the 'wake effect'.

wake losses

Reduced power ouput occurring in a wind turbine due to decreased wind speed caused by another wind turbine in front to it.


Wien Automatic System Planning Package

waste heat recovery

Process in which waste heat from an industrial process is used for another purpose or process. The aim is to reduce energy consumption.

watt peak

Amount of electrical power a photovoltaic module will produce at Standard Test Conditions (AM 1.5, 1,000 W/m2 and 25°C cell temperature).


World Business Council for Sustainable Development

weather service

Public or private company creating weather forecasts.

Weibull distribution

The Weibull wind speed distribution is a mathematical idealization of the distribution of wind speed over time.

Weibull scale parameter

The scale parameter (A) in the Weibull distribution is a measure for the characteristic wind speed distribution. A is proportional to the mean wind speed. Unit: m/s

weighted average cost of capital

WACC [%] - Formula used to calculate the actual cost of capital used to finance a project. Typically refers to the weighted cost of both debt (e.g. from a bank) and equity (from private investors). For instance, if a project uses 80% debt at a rate of 5% and 20% equity at a rate of 10%, the WACC will be 6%. This represents the cost of capital used to finance that project.


Wholesale Electricity Spot Market


waste heat recovery

Wien Automatic System Planning Package

An IAEA computer software for power generating system expansion planning.

wind power class

A scale from 1 (low) to 7 (high) based on average wind speed (m/s or mph) and power density (W/m2) which rates the quality of the wind resource in an area.

wind ramps

Steep increase or decrease of wind speed.

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