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An introduction to energy resources
An introduction to energy resources

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S278_2 Glossary

S278_2 Glossary.
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Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL

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A

Anoxic

Conditions that are oxygen poor (lacking oxygen). Not all the fixed carbon in dead plant tissue returns to the atmosphere as CO2: some may be retained as carbon-enriched residue and yet more converted into hydrocarbons.

B

Biomass

Wood and other plant materials that can be used as fuels.

C

Carbohydrates

Organic compounds of carbon, hydrogen and oxygen, with the general formula CnH2nOn. Glucose, one of the simplest carbohydrates, has the formula C6H12O6.

Carbon cycle

The movement of carbon between the major natural stores of carbon (called ‘reservoirs’) on the Earth. The two major divisions of the cycle are the terrestrial and marine carbon cycles.

E

Energy

The capacity to do work, measured in joules (J).

Energy density

The amount of energy stored by a resource relative to the volume that it occupies.

Energy efficiency

The ratio of the useful output of work to the input of energy supplied — usually expressed as a percentage.

Enthalpy

The total energy content of a physical system.

F

Force

The means by which the direction or speed of movement of an object is changed; equal to mass x acceleration.

Fossil fuels

Combustible resources derived from ancient organisms, especially coal, oil and natural gas.

Fuels

Materials capable of liberating energy by nuclear and chemical reactions, including combustion. They commonly have a high energy density.

H

Hydrocarbons

Organic compounds, such as methane, that contain only hydrogen and carbon.

Hydropower

Conversion of the potential energy of water in rivers or reservoirs to electricity, by using the kinetic energy that is released when it flows to turn turbines. Because rainfall stems from water vapour evaporated from the ocean surface, hydropower is an indirect form of solar energy.

J

Joule (J)

The SI unit of energy and work. A joule (J) of work is done when a force of one newton moves an object through a distance of one metre.

K

Kinetic energy

Mechanical energy that exists by virtue of movement. For example, a car engine turns chemical energy (petrol) through heat into movement (engine parts and road wheels).

M

Marine carbon cycle

That part of the carbon cycle that involves the circulation of carbon in seawater through biological activity and inorganic processes.

Methane

CH4; a gaseous hydrocarbon that is the main component of natural gas.

N

Newton

The force that gives a mass of one kilogram (kg) an acceleration of one metre per second per second (m s−2), and is therefore equivalent to 1 kg m s−2.

Non-renewable energy

Energy resources that are replenished naturally over extended timescales of thousands or millions of years. As they are exploited faster than they are replenished they are considered as non-renewable.

P

Photosynthesis

A chemical reaction in green plants in which carbon dioxide from the atmosphere combines with water to form carbohydrates, using the energy of solar radiation.

Photovoltaic (PV) effect

The result of electrons being freed from impurities in semiconductors by the quantum energy of light photons, so that the electrons move to generate both electrical potential and current. The principle behind solar cells.

Potential energy

Mechanical energy that exists by virtue of position or potential in a force field — usually that of gravity.

Power

The rate at which energy is delivered or work is done, measured in watts (W). One watt is equivalent to one joule per second.

Primary energy

The energy released by directly burning fossil fuels or consumed at source in electricity generation.

R

Renewable energy

Supplies of energy on Earth from internal and external processes that are continually available, whether they are used or not. They include solar, tidal, wave, wind, hydro and geothermal energy.

Residence time

The average time that carbon stays in a reservoir before moving to another reservoir, estimated by the amount in the reservoir divided by the transfer rate.

Respiration

The process where the organisms uses oxygen from air to react with the carbohydrates to liberate energy. Carbon dioxide and water are returned to the atmosphere during the respiration process.

S

Semiconductors

Poorly conductive materials doped with impurities, which act to increase electrical conductivity to a level intermediate between non-conductors and conductors. Bonded together in photovoltaic cells, they can generate an electrical current.

Solar energy

Solar radiation that reaches the Earth’s surface is potentially available as an energy resource as direct solar energy using photovoltaic cells.

T

Terrestrial carbon cycle

That part of the carbon cycle involving biological and inorganic processes on land.

Tonne oil equivalent (toe)

The chemical energy contained in one tonne of oil, it equates approximately to 4.19 × 1010 J. Often used as a convenient means of comparing the energy contents of different fossil fuels.

W

Watts (W)

The SI unit of power. One watt (W) is equivalent to converting one joule of energy per second, or doing one joule of work every second.

Work

A force acting on an object that causes its displacement, equivalent to energy.

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