Renewable Energy Terminology


If you’re new to Renewable Energy, you’ll likely come across a whole host of new phrases, ab...

NES Fircroft

By NES Fircroft

If you’re new to Renewable Energy, you’ll likely come across a whole host of new phrases, abbreviations and terms. To help you adapt, we’ve collated a list of the terminology you may need to know.

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A term used in the Solar Power sector to describe a material in Photovoltaic devices that easily absorbs photons.


An abbreviation for ‘alternating current’ which refers to a type of electrical current in which the direction of electricity is reversed regularly.

Activated shelf life

Refers to the time limit in which a charged battery can be stored before its capacity decreases below a usable level.

Activation voltage(s)

The voltage required for the charge controller (a component within a photovoltaic system used to control the flow of current from the battery) to act and prevent the batteries from over-charge and over-discharge – which would cause damage.


A term used to measure how capable a power system is of supplying the energy required. Planned and unplanned outages of system components will be considered.

Adjustable set point

Refers to a feature that allows the voltage levels at which a charge controller will become active to be altered.


An abbreviation for ‘Alternative Fuel Vehicle’ which refers to a vehicle that runs on a fuel alternative to traditional petrol or diesel.

Ambient heat (or heat pumps)

Refers to the process of extracting energy from the air, ground or water and subsequently converting it to energy that can be used elsewhere – for example, to heat space via underfloor heating.

Ampere (Amp)

Refers to the unit of measurement for electrical currents.


A term used to measure the amount of electrical current flowing for an amount of time.

Ampere hour meter

An instrument that monitors the electrical current with time.

Ancillary services

Refers to services that assist the grid operator in maintaining balance to the system. These include regulation, contingency reserves and in some regions, supplemental operating reserve. It could also refer to the provision of reactive power or frequency response.


Can refer to the positive electrode in a battery, the earth or ground in a cathodic protection system or the positive terminal of a diode.


An abbreviation for ‘Application Programming Interface’ which is the term used to describe how one computer programme communicates with another. When in use, an API can enable software programmes to connect with the internet to request and/or exchange information.

Arc ASCII Grid format

A specific interchange format consisting of a header that specifies the geographic domain and resolution, followed by the grid cell values.


Refers to the second phase in a renewable energy project’s development life cycle. The Assessment phase determines if a site is suitable for development and includes an analysis of power capacity along with long term performance.


A term used to describe an energy source's potential to generate power. For example, in wind power, available describes the amount of the time that the wind turbine is functional.

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Batteries are a key part of the Renewable Energy industry – without them, it would be impossible to store energy generated. They are even more important in remote areas that aren’t connect to strong grids.

Generally, they consist of two or more electrochemical cells enclosed in a container. The cells are electrically interconnected to provide the required operating voltage and current levels.

Battery Bank

A term used to describe an array of batteries that stores renewable energy.

Battery Cycle Life

Refers to the number of cycles that a battery can undergo before it fails to meet its specified energy performance criteria.


Biodiesel is the term used to describe an alternative fuel produced with sustainable/renewable sources such as plant oils and algae. It doesn’t contain petroleum but can be combined with petroleum to create a biodiesel blend to fuel engines.


Refers to chemicals such as alcohols, ethers and esters made from biological materials like plants, forestry residues, industrial waste and woody plants.


A term used to describe organic waste from livestock, or agriculture. Lumber industry products are also included such as dead trees. Biomass is used to make fuels like biodiesel and is burned like oil to produce energy.

Bottleneck Facility

Refers to the point on an electric system through which all electricity passes – such as a transmission line. If there is limited capacity available at any point, power will be prioritised depending on needs of the buyers. Additional facilities can be built to relieve constraint.


Is an abbreviation for ‘British thermal unit’. This refers to the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit under stated conditions of pressure and temperature.

Bulk Power Supply

Sometimes referred to as ‘wholesale power supply’. This term is used to describe the combination of electric generating plans, transmission lines and related equipment.

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Refers to the components of a solar PV module that converts the solar energy to electricity.

CF (Cubic Foot)

The U.S. customary unit used to measure the volume of gas. Essentially, it’s the amount of gas required to fill a volume of one cubic foot under stated conditions of temperature, pressure and water vapor.

CO—Carbon Monoxide

A tasteless, colourless and odourless flammable gas. CO is slightly less dense than air and consists of one carbon atom and one oxygen atom.

CO2 —Carbon Dioxide

Carbon dioxide is also colourless, odourless, and tasteless but has a slightly higher density of dry air. CO2 consists of one carbon atom covalently double bonded to two oxygen atoms.

Cogeneration (also Combined Heat and Power)

Refers to the creation of electricity from steam, heat, or other forms of energy produced as a by-product of another process.

Combined Cycle

An electric generating technology in which process steam and electricity is produced from otherwise lost waste heat escaping from one or more combustion turbines. This process raises the efficiency of the electric generating unit.

Combined hydroelectric plant

Refers to a hydroelectric plant that uses both natural streamflow and pumped water for the production of power.

Control Area

An electric system surrounded by transmission lines that are equipped with metering and telemetry equipment to track and report power flows with neighboring control areas.

Cooperative electric association or utility

A type of cooperative that is tasked with delivering public utilities such as water or electricity. It’s owned and operated by its members.

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A physical barrier constructed across a river or waterway used to control/restrict flow of water. In renewable energy, a dam is often used within the hydropower sector to generate electricity.


Stands for ‘direct current’ and describes a one directional flow of electric charge.


The rate at which electric energy is delivered to a system or by a system at a given instant or averaged over any designated interval of time. Generally measured in kilowatts (kW), megawatts (MW), or gigawatts (GW).

Demand Charge

A charge based on the peak quantity of electricity used during a billing cycle.


When a previously regulated industry or sector / sector goes through a regulation restructure or removal.

Distributed Generation (DG)

(Also called distributed energy resources, distributed power, distributed energy, distributed generation, on-site generation)

A distributed generation system refers to electrical generation and storage performed by a variety of small, grid-connected or distribution system-connected devices – generally located on a utility’s distribution system for the purpose of meeting local (substation level) peak loads and/or displacing the need to build additional (or upgrade) local distribution lines.


Refers to the final stage in the delivery of electric power – essentially the delivery of electricity to a retail customer’s home or business through low voltage distribution lines. Typically the voltage ranges between 2 KV and 35 KV.

DSM (Demand Side Management)

Refers to programmes used to influence the amount and/or timing of retail customers’ energy use.

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Energy Efficiency & Renewable Energy, U.S. Department of Energy


The United States Department of Energy’s Energy Information Administration.

Electric Energy

Refers to the creation or use of electric power by a device over a period, expressed in kilowatt-hours (kWh), megawatt-hours (MWh), or gigawatt-hours (GWh).

Electric System Losses

Total electric energy losses in the electric system. Losses can occur due to electric resistance within transmission system lines and transformers.


​Stands for Electromagnetic fields which are classical fields produced by accelerating electric charges.

Energy Conservation

Refers to describe using less energy. This can be achieved either by greater energy efficiency or by decreasing the types of appliances that require electricity to function.

Energy Efficiency

Using less energy (electricity and/or natural gas) to perform the same function without a drop in quality.


Stands for the U.S. Environmental Protection Agency.


Stands for ‘Electric Vehicle’. An EV is a vehicle that is powered by energy stored in batteries rather than traditional fuel sources such as petrol or diesel. It doesn’t have an internal combustion engine.

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Refers to an existing or planned location where equipment used to convert chemical, mechanical or nuclear energy into electric energy is or will be situated.

Federal Energy Regulatory Commission (FERC)

A government body in the USA that regulates the price, terms and conditions of power sold in interstate commerce and of all transmission services.

Feed-in-Tariff ("FIT")

Refers to money paid to a customer by a power company if they generate power by a renewable energy source, such as solar or wind power. Feed-in-tariffs are implemented to encourage customers to install renewable energy equipment and sell excess renewable energy back to the utility company.


Refers to the part of an incandescent lamp which electricity passes through to produce light.

Flow control

The laws, regulations, and economic incentives or disincentives used by waste managers to control the flow of waste from one geography to a designated area for processing, such as a waste-to-energy facility.

Fluorescent light

A lighting device that uses an electrified gas produce light over a traditional Filament.

Fuel wood

Wood and/or wood products used to generate energy by direct combustion.

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Gallium (Ga)

Is a chemical element that is metallic in nature. Gallium is used most in the Solar Power sector to make solar cells and semiconductor devices.

Geothermal energy

Refers to the energy available (as heat) found within the earth’s crust. Usually this energy is in the form of hot water or steam.


A gigawatt refers to one billion watts of electrical energy.

Global Warming

The Earth's gradual warming due to the ‘greenhouse effect’ – sometimes referred to as ‘climate change’.

Greenhouse Effect

Refers to a process in which certain gases (such aa water vapor, carbon dioxide, nitrous oxide, and methane) in the atmosphere trap energy from the sun, causing the Earth’s temperature to rise. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF/ 15°C colder.

Greenhouse Gases

Gases in the Earth's atmosphere that produce the greenhouse effect (see above). Changes in the concentration of certain greenhouse gases, increase the risk of global climate change.

Green pricing

Green pricing programs allow electricity customers to express their willingness to pay for renewable energy development through direct payments on their monthly utility bills.


The network of wires and cables that transport electricity from a power plant to the general public.

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Hydropower or Hydroelectric Power

Refers to the electricity generated from the potential and kinetic energy of water in hydroelectric plants.

Harmonic content

Used in reference to Solar Power and refers to the number of frequencies in the output waveform in addition to the primary frequency (50 or 60 Hz.). Energy in these harmonic frequencies is lost and can cause over-heating.


An area of electrical contact between two different materials.

High Voltage Disconnect

Used in reference to solar power and refers to the voltage at which a charge controller will disconnect the photovoltaic array from the batteries to prevent overcharging.

Hydrogen Fuel Cell

An emerging technology which uses a combination of hydrogen and oxygen to produce electrical current. Water vapor is given off as a by-product.


Refers to the region between an n-layer and a p-layer in a single material, photovoltaic cell.

Hybrid System

Refers to a solar electric or photovoltaic system that also includes other power generating sources such as wind generators.

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An abbreviation for the ‘International Energy Agency’.

Independent System Operator (ISO)

Refers to an independent organization that oversees the operation of a transmission system. Ultimately, they have final authority over the dispatch of electricity from generations to consumers. They have no financial interest thus can preserve reliability and ensure non-discriminatory access.

Interconnected System

A system defined by two or more individual electric systems that are connected and have synchronized operations.


Refers to the facilities that connect two systems or control areas.


An abbreviation for Integrated Resource Planning.

Investment Tax Credit (ITC)

Refers to an incentive in the USA for installing a solar power system in ones home. The tax credit equates to 30% and can be applied to tax bill.

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Joint-use facility

Refers to a multiple-purpose hydroelectric plant. For example, a joint-use facility could be a dam that stores water for both flood control and power production.


A metric unit of energy - 1 joule per second equals 1 watt or 0.737 foot-pounds; 1 Btu equals 1,055 joules.


Refers to the area of transition between semiconductor layers (such as a p/n junction).

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Kaplan turbine

A type of water turbine that has adjustable blades. Kaplan turbines are now widely used throughout the world in high-flow, low-head power production.

Kilowatt ("kW")

Refers to 1,000 watts of electricity.

Kilowatt-hour ("kW-h")

One thousand watt-hours. Calculated by multiplying the number of watts being used times the length of time in hours that amount of electricity is used.


Is an abbreviation for kilovolt and equals 1,000 volts.

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An abbreviation for "Leadership in Energy and Environmental Design".

LEED Rating Systems 

Refers to a certification program for the design, construction, and operation of high-performance green buildings. LEED provides building owners and operators with the tools they need to have an immediate and measurable impact on their buildings' performance.

Four levels of certification are offered, and the final certification is decided depending on the number of accrued “credits” in green design categories such as water efficiency and sustainability.

Light Emitting Diode ("LED") 

Refers to an extremely efficient source of light - "LED" lamps convert from 65% to 95% of the electric energy to light energy and typically last 50,000 to 100,000 hours.


A unit of luminous flux which essentially measures the total quantity of light emitted that is visible to the human eye.

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Refers to a unit of measurement for volumes of natural gas (one thousand cubic feet).


An abbreviation for a megavolt-ampere - this equals 1,000 kVA.

Megawatt (MW)

A unit of measurement - a megawatt equals 1,000 kilowatts or 1 million watts.

Megawatt-hour (MWh)

The unit of energy equivalent to that used in one hour at a rate of one million watts.

Monocrystalline Solar PV

Refers to high-performance solar cells – they achieve 17% efficiency.

Mass burn facility

A type of municipal solid waste (MSW) incineration facility. At a Mass burn facility, MSW is burned with minor pre-sorting to remove hazardous, or explosive materials.

Minimum streamflow

Refers to the lowest rate of flow of water to a given point during a specified time.


Photovoltaic cells intended for/shipped for final consumption or to another organization for resale. When shipped, incomplete modules and unencapsulated cells are also included.

Multiple purpose reservoir

Refers to stored water that is most used to generate hydroelectric power. Other uses are irrigation, flood control and wilderness protection.

Municipal solid waste

Residential solid waste and some non-hazardous commercial, institutional, and industrial wastes.

Municipal waste

Defined as waste collected and treated by or for municipalities. This includes waste from households, any organic matter, including sewage, sewage sludge, and industrial or commercial waste.

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​NEG and NEM

Abbreviations for ‘Net Energy Generation’ and ‘Net Energy Metering’. When a person can generate their own electricity (usually through solar panels), NEG refers to the total electricity produced minus the electricity used from the grid.

Therefore, NEM refers to the electricity generated that will feed into the grid leading to a reduction in the person’s utility bill.

Net head

Defined as the head available at the inlet of the turbine minus all hydraulic losses (except those chargeable to the turbine).

Nickel cadmium battery

A battery containing nickel and cadmium plates and an alkaline electrolyte.

Nominal voltage

Refers to voltage used to describe batteries, modules, or systems.

Non-biomass waste

Material of non-biological origin. Non-biomass waste is usually a byproduct or a discarded product such as municipal solid waste like plastics, and tire-derived fuels.

NO x

Is an abbreviation for Nitrogen Oxides.

Nuclear Power

​Electricity produced by the use of nuclear reactions. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions.

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Ocean energy systems

Refers to energy conversion technologies that utilize the energy in tides, waves, and thermal gradients in the oceans.

Ocean thermal energy conversion (OTEC)

The process or technologies used to harness energy from thermal gradients between ocean surface waters and that of ocean depths.

Warmer surface water is pumped through an evaporator that contains a working fluid in a closed Rankine-cycle system. The vaporized fluid then drives a turbine/generator to create energy or produce desalinized water. Systems may be either open-cycle, closed-cycle, or hybrid.

Off-Grid Systems

A term used to describe systems that are not connected to the main commercial or national power transmission grid.

Organic waste

Waste material originating from animals or plants.

Oscillating water columns

(OWCs) are a type of Wave Energy Converter (WEC). Energy is harnessed from the oscillation of ocean/seawater inside a chamber caused by the action of waves.

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Parabolic dish

A high temperature (above 180 degrees Fahrenheit), reflective surface used to collect light. It gets its name from it’s bowl-shape and has two-axis tracking. Sometimes it’s referred to as a parabolic reflector.

Parabolic trough

A high-temperature (above 180 degrees Fahrenheit) solar thermal concentrator with the capacity for tracking the sun using one axis of rotation. It’s made up of a set of concave mirrors that concentrate solar rays on the receiver tube to generate energy.

Passive solar heating

A solar heating system that doesn’t use external mechanical power, like pumps or blowers, to transport the collected solar heat.

Peak Load or Peak Demand

A term used to describe the electric load that corresponds to a maximum level of electric demand within a specified period. It’s typically characterized as annual, daily, or seasonal.

Performance Based Incentive (PBI)

A payment or rebate paid based on energy production on a $/kWh basis. A PBI benefits those with larger solar power systems.

Photovoltaic cell (PVC)

An electronic device consisting of layers of semiconductor materials - sometimes called solar cells. These cells make up photovoltaic modules and are used to produce energy from sunlight.

Photovoltaic module

An integrated assembly of interconnected photovoltaic cells.


Usually refers to the amount of water stored behind a hydroelectric dam of a relatively small storage capacity.

Power Pool

Two or more interconnected electric systems used together to balance the electrical load over a large network.


An abbreviation for Photovoltaic.

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A unit of measure used to describe very large quantities of energy - one quadrillion Btu (1,000,000,000,000,000 Btu). One quad is equal to one quadrillion.

Qualification test

Qualification testing is performed in a variety of different sectors to verify any design and manufacturing processes. In this context, this test can be used on photovoltaic modules and involves the application of defined electrical, mechanical, or thermal stress in a prescribed manner and amount. Test results are subject to a list of defined requirements.

Quantum efficiency (QE)

The quantum efficiency of a solar cell is defined as the ratio of the number of charge carriers collected by a photovoltaic cell to the number of photons of a given energy shining on the cell.

Optimally, a solar cell should generate considerable electrical current for wavelengths that are most abundant in sunlight.

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Stands for ‘refuse derived fuel’. This type of fuel is used in some electric generation plants and is composed of processed garbage.

Real time pricing

Refers to the instantaneous pricing of electricity depending on the consumer demand and the cost of electricity available for use at the time.

Renewable Energy

Sometimes referred to as ‘renewables’ or abbreviated to ‘RE’ - renewable energies include energy sources that don’t come from finite resources, such as wind energy, hydropower, solar energy (solar thermal, photovoltaics), bioenergy (biomass and biogas) and geothermal energy.


Refers to how dependable an electricity system is. The reliability is assessed by looking at the adequacy and security:

  • Adequacy is the ability of the electric system to always meet the energy requirements of consumers.

  • Security is the ability of the electric system to withstand sudden disturbances such as an unanticipated loss of system facilities.

Renewable Energy Certificate (REC)

A REC certifies that the bearer owns/has generated one megawatt-hour (MWh) of electricity from a renewable energy resource.

For example, owners who generate solar electricity are credited with 1 solar REC for every MWh of electricity they produce. Once this energy is fed into the grid, the REC’s received can then be sold on the open market.

​Reserve Margin

Refers to excess energy capacity above or over the anticipated consumer need. The reserve margin is kept providing operational flexibility and system reliability in the case of a planned or unplanned outage.


A catalytic process used to convert methane or other hydrocarbons and water into hydrogen and carbon monoxide to create hydrogen.

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Series connection

Refers to a way of linking solar power cells by connecting positive leads to negative leads. This configuration increases the voltage.

Solar energy

Refers to solar thermal energy (which is radiation utilized for solar heat) and solar photovoltaic energy used in electricity production.

Solar pond

A body of water that contains highly saline water. The saline forms layers of differing salinity that, in turn, absorb and trap solar energy. Solar ponds can be used to provide heat for industrial or agricultural processes and to generate electricity.

Solar power tower

A solar energy conversion system that uses independently adjustable mirrors to focus solar rays on a single point on a fixed tower.

This concentrated energy can then be used to heat specific areas, such as the working fluid of a Rankine cycle engine or to heat an intermediary thermal storage medium (such as a molten salt).

Solar radiation

A general term for the ultraviolet and near-infrared electromagnetic radiation that is emitted by the sun.

Solar thermal collector

A device designed to receive solar radiation and convert it to thermal energy. The heat collected by this device is used immediately or stored for later use. Solar collectors are most often used for domestic hot water heating and heating swimming pools, hot tubs, or spas.


Refers to the rate at which water passes a given point in a stream, usually expressed in cubic feet per second.

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Tare loss

Tare loss refers to the loss caused by a charge controller. One minus tare loss, most often expressed as a percentage, equals the controller efficiency.

Tertiary control

Tertiary control refers to any manual or automatic change in the working points of generators, generally by rescheduling, to re-establish a sufficient secondary control reserve at the appropriate time. The power connected under tertiary control is referred to as the tertiary control reserve. This power, when used, contributes to restoring the secondary control range when necessary.

Thermal rating (electric)

Thermal rating is the maximum amount of electrical current that an electrical facility or transmission line can conduct during a specific period before it drops to the point where it violates public safety requirements or before it sustains permanent damage by overheating.

Thermophotovoltaic (TPV)

Thermophotovoltaic denotes the capacity to convert infrared radiation into electricity. TPV energy conversion is a direct conversion process from heat to electricity via photons. A basic TPV system involves a photovoltaic diode cell and a thermal emitter.

Thin film

A thin film is a layer of material ranging from a fraction of a nanometre (monolayer) to several micrometres in thickness. In photovoltaic panel manufacturing, thin film modules are made by placing a thin layer of semiconductor material, such as gallium arsenide or copper indium diselenide, on a plastic or glass substrate.

Tilt angle

The tilt angle is the angle between a solar panel and the horizontal plane which can be adjusted to maximize energy collection.

Tip speed

The tip speed refers to the speed (in metres per second) of the tip of a turbine blade through the air.


A tracker is an automatic mechanical device that decreases the angle of incidence between incoming sunlight and a photovoltaic panel. This leads to an increase in the power of the solar radiation picked up by the panel, meaning more energy is produced.


A transformer is an electromagnetic device that changes the voltage of alternating electric currents.

Transmission System Operator (TSO)

A Transmission System Operator is an entity responsible for transporting electrical power on a regional or national level using fixed infrastructure. This entity will oversee operating, maintaining and developing the transmission system for a given area and its interconnections.

Terawatt hour (TWh)

A terawatt hour is a unit of measurement for energy, equivalent to 1,000 gigawatt hours (GWh) or a billion kilowatt hours (kWh).


In a wind generator blade, the twist is the difference in pitch between the tip and the root of the blade. Most often, the twist enables more pitch at the root for easier start-up and less pitch at the tip for better high-speed performance.

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Ultraviolet (UV) refers to a form of electromagnetic radiation with a wavelength ranging from 10 nanometres (with a corresponding frequency around 30 PHz) and 400 nanometres (750 THz). This is shorter than the wavelength of visible light and longer than that of X-rays.

Underground Feeder (UF)

An underground feeder is a cable sometimes used for photovoltaic array wiring if sunlight resistant coating is specified. It can be used for connecting balance-of-system (also known as a BOS, it refers to all the components of a photovoltaic system other than the photovoltaic panels) components, but its use isn’t recommended within battery enclosures.

Underground Service Entrance (USE)

An underground service entrance may be built within a battery enclosure and for linking balance-of-systems.

Unglazed Solar Collector

An unglazed solar collector is a solar collector that comprises an absorber without the glass covering of a glazed flat-plate collector.

These are often used for swimming pool heating systems because they can circulate relatively large volumes of water through the collector whilst still taking in near 80% of available solar power.

They are usually made of black plastic that has been stabilised to withstand UV light. Because they don’t have glazing, they can absorb a large portion of the sun’s energy. However, they aren’t insulated so a large portion of the absorbed heat is lost, especially if it’s windy or cold outside. Still, unglazed solar collectors are extremely good at transferring heat to and from the air, meaning they can capture heat even at night if it’s warm outside.

Uninterruptible Power Supply (UPS)

This refers to a power supply that provides continuous uninterruptible service. A UPS will provide emergency power to a load when the mains or the input power source fails.

An uninterruptible power supply is different from an emergency or auxiliary power system or standby generator in that it will procure near-instant protection from input power interruptions by providing energy stored in supercapacitors, flywheels, or batteries.

Unitary Energy Gross Margin

The unitary energy gross margin refers to the ratio of gross margin (proceeds from energy generation and other proceeds from non-core activities net of variable costs) and consolidated net production.

Unity with the landscape

Unity with the landscape designates the degree to which people perceive wind turbines to fit into the surrounding landscape. The perceived impact of wind turbines on a landscape is one of the biggest factors influencing public attitudes towards wind farms, and whether they are approved of or opposed.

U-Shape Curve

A U-Shape Curve refers to the model that states shifting attitudes towards wind farms. Attitudes will generally be positive before the announcement of a project. They will then become more negative once the project has been announced and improve once construction has ended.


The utility is the incumbent electricity supplier to end-users. Utility companies can often be state-owned and will generally own and operate other electricity supply assets such as generation plants and transmission networks.

Utility-Interactive Inverter

A utility-interactive inverter is an inverter that only functions when tied to a utility grid. It uses the dominant line-voltage frequency on the utility line as a control parameter to make sure that a photovoltaic system’s output is fully synchronized with the utility power.

Utility-Scale Wind

Utility-scale wind refers to wind energy projects that are higher than 100 kilowatts in capacity and for which the electricity generated is sold rather than used on site. This category can encompass anything from a single locally-owned turbine that is bigger than 100 kilowatts in size to large arrays of wind turbines owned by major corporations.

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Variable air volume (VAV) system on the heating and cooling system

A type of heating, ventilating and/or air conditioning system. A variable air volume system maintains the air flow at a constant temperature but supplies varying quantities of conditioned air in different parts of the building according to the heating and cooling needs.

Variable fuel vehicle

Refers to a vehicle that can operate on varying fuel sources, such as 100-percent petroleum-based fuels, alternative fuels (such as biodiesel or hydrogen) or any mixture of an alternative fuel (or fuels) and a petroleum-based fuel.

Variable-speed wind turbines

Refers to Turbines that are specifically designed to operate with varying rotor speeds, which can increase or decrease depending on the wind speed. This means electricity is produced with a variable frequency.

Vertical-axis wind turbine (VAWT)

Refers to a type of wind turbine in which the axis of rotation is perpendicular to the windstream and the ground. This arrangement allows the generator and gearbox to be located close to the ground, facilitating service and repair.

Volt (V)

The volt is the International System of Units(SI) measure of electric potential or electromotive force. One volt is defined as the electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points.


Refers to the difference in electrical potential between any two conductors or between a conductor and ground.

Voltage reduction

Refers to an intentional reduction of system voltage by 3 percent or greater. A reduction in the voltage across the resistance will result in a reduction in the power dissipated by the circuit.

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NES Fircroft and supporting the Renewable Energy sector

At NES we’re excited to see such a sustained and unprecedented growth in renewable technologies supporting the energy industry.

If you’re looking for skilled personnel our discipline-specific consultants can support all stages of your renewable project life cycle, from the funding, design and installation phases’ right through to project management and grid installations.

We work on some of the most exciting renewables projects globally, meaning we have plenty of renewable job opportunities for engineers looking to enhance their energy careers.