Glossary of Energy Terms

When talking ‘energy solutions’ to our clients we cover a broad range of energy terms that may not be common knowledge. The glossary below is designed to give some insight in to the various definitions and abbreviations that exist within our industry.

The following terms are found within the electrical and energy sectors:

General Electrical Terms

Joule (J) – A unit of energy to measure the force needed to transfer mass from one space to another.

Watt (W) – A unit of electrical power used to quantify the rate of energy transfer.

Kilowatt (kW) – A unit of electrical power equivalent to 1000W.

Kilowatt Hour (kWh) – A measure of electrical energy consumption equivalent to using 1000W (1kW) for a period of one hour.

Current – A flow of electricity in an ordered direction.

AC Power – Alternating current that periodically reverses direction, used commonly in power supplies.

DC Power – Electricity that flows in one direction only

Voltage (V) – A measure of electrical potential; i.e. how strong an electrical current is sent down a cable.

Amps (A) – A unit of electrical current.

Inverter – A piece of equipment that converts direct current (DC) in to alternating current (AC) or vice versa.

Transformer – A piece of equipment that modulates the voltage of current so that it can be transferred from one circuit to another that use different voltages.

Junction Box – A piece of equipment that contains a junction for combining electrical cables.

Breaker – A switch that protects an electrical circuit from damage by automatically stopping the flow of electricity if an overload or short circuit problem is detected.

Earth – Required for a safe installation, the common return path for electrical current in a circuit.

Frequency (Hz) – Measured in hertz (1Hz equals one cycle per second). For example, in the UK AC electricity is at 50Hz.

Triad – The three half-hourly periods of highest electrical demand on the National Grid between November and February every year. Businesses are sampled and billed on this usage every year.

DUoS – The Distribution Use of System is the recovering of the cost for distributing electricity by your energy supplier.

Charge Bands – The DUoS is billed across three charge bands known as ‘red’, ‘green’ and ‘amber’. Costs are highest when drawing energy in the ‘red’ periods and lowest in the ‘green’ periods.

DNO – Distribution Network Operators are energy companies licensed to distribute and sell electricity, e.g. British Gas, EDF.

Terms Used in the Solar PV Sector

Solar Panel – A device that uses a number of photovoltaic (PV) cells to capture and absorb the suns rays to turn into DC electricity.

Mounting Rail – A rail used to mount solar panels on to.

Clamp – Device used to fix to solar panels to the rail.

Performance Ratio (PR) – The primary measure of a solar PV system’s efficiency; expressing how effectively the system converts sunlight collected by the solar panels into AC electrical energy.

D-marc Edge Protection – A health and safety measure that makes the working area (roof) of the building safe from falling incidents utitlised on roofs under 15 degree pitch.

Safety Rail – A health and safety measure that makes the working area (roof) of the building safe from falling incidents utitlised on roofs iver 15 degree pitch

Access Ladder – A ladder used for access, generally to the rooftop of a site where solar is to be installed

O&M – Operation and Maintenance

Warranty – The assurance given by a manufacturer that a piece of equipment will work to a given standard within a given period.

Weather Station – A collection of devices used to measure weather and ultimately help to understand what a PV system should be outputting at any given time


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