English Glossary


02.06.2017

Browse the glossary using this index

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U

U-value

The overall heat transfer coefficient that describes how well a building element conducts heat or the rate of transfer of heat (in watts) through one square metre of a structure divided by the difference in temperature across the structure.

UASB

upflow anaerobic sludge blanket

ultraviolet

Electromagnetic radiation with shorter wavelengths than visible light. Wavelengths of UV light range from approximately 10 nm to 400 nm. Because of the short wavelengths, UV light carries higher levels of energy per photon than infrared light or visible light. When speaking about solar cells, UV light is commonly referred to as ‘blue light’.

UMPP

Ultra Mega Power Project

UN

United Nations

underexcited

Describes the state of a generating plant when the plant voltage is less than the network voltage at the POC. In this state the plant current leads the network voltage and the plant absorbs reactive power from the network.

UNDP

United Nations Development Programme

UNEP

United Nations Environment Programme

UNFCCC

United Nations Framework Convention on Climate Change

unidirectional power flow

Power flow in only one direction.

Up

internal voltage (synchronous generator)

upflow anaerobic sludge blanket

A form of anaerobic digester that is used for wastewater treatment and uses an anaerobic process whilst forming a blanket of granular sludge which suspends in the tank. Wastewater (liquids with relaitvely low organic loads) flows upwards through the blanket and is processed (degraded) by the anaerobic microorganisms.

upstream

In the higher part of a stream, closer to its source

USAID

US Agency for International Development

useful energy

Energy that can be used to perform a certain task, as opposed to total energy generated (some of which may not be capable of being used, such as waste heat).

user

Everybody that makes use of a power system, such as generators, consumers, network operators

Ut

terminal voltage

UTC

Coordinated Universal Time

UV light

ultraviolet