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A measure of volume equal to 4 quarts (231 cubic inches). One barrel equals 42 US gallons


This is a non-liquid, non-solid substnace that has no fixed shape and can expand without limit.


Complex combination of relatively volatile hydrocarbons that can have additives in it.

Gas To Liquids (GTL)

This is a process that combines hydrogen and carbon in natural gas molecules in order to create synthetic liquid petroleum products.

Gas Turbine Plant

This is a plant that has a gas turbine as its primary mover. Gas turbines typically have an axial-flow air compressor and combustion chambers where gaseous or liquid fuels are burned. These hot gases are then passed into the turbine; the hot gases expand, which drive the generator and then in turn used to run the compressor.


This is a device that turns mechanical energy into electrical energy.

Generation (Electricity)

This is the process of producing electricity from other energy forms. The amount of electric energy produced is expressed in watt hours (Wh).

Generating Capacity

This is the amount of power that an electrical plant can produce.


This is a type of geothermal resource that takes place in the depths of basins, typically where the fluid is under high pressure.

Geothermal Energy

This is steam or hot water that is extracted from geothermal reservoirs in the Earth's crust that is used to produce electricity.

Geopressured Geothermal

This is a type of geothermal resource that takes place in the depths of basins, typically where the fluid is under high pressure.

Geothermal Plant

This is a plant where a turbine is either driven from hot water or natural steam. The energy is derived from the heat in the rocks or fluids that are at various depths.


This is a thermal spring that periodically ejects water with great force from the ground.


A measuring unit of power, abbreviated as GW. 1 GW equals 1 billion watts. Power (W) multiplied by time (h) equals energy (Wh)

Gigawatt hour

A measuring unit of energy, abbreviated as GWh. 1 GWh equals 1 billion watts acting over a period of 1 hour. Energy (Wh) divided by time (h) equals power (W)


Geographic Information System

Global Warming

This is an effect that is caused by the greenhouse effect, where there is a slight continuous increase in the average temperature of the Earth.

Global insolation

This is the sum of direct and diffuse insolation (solar radiation energy).

Green field (open space)

Undeveloped or unused land where a PV Plant can be built

Green Liquor

Pulping and/or bleaching process in pulp and paper mills. Black Liquor can be retrieved from green liquor by membrane processing and evaporation.

Green Pricing

This represent a market solution for the regulatory valuation of the non-market benefits of renewables.


The layout of an electrical distribution system

Grid Availability

This is the availability of electrical transmission system of a utility for carrying the energy generated by a turbine.

Grid parity

Break even point of self-generated and purchased electric energy

Grid-connected PV system

PV plant functioning like a central electricity generating plant, supplying power to the grid


This is water that is in the subsurface zone, under pressure that is greater than the atmosphere.


Temporary change in the wind speed