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renewable energy > glossary
GlossaryBio-gas: A combustible gas (composed primarily of methane) produced when sewage or manure is fermented in the absence of oxygen. The solid material that remains in the digester after fermentation can be used as an organic fertilizer.
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Biofuel: Renewable hydrocarbon fuel, usually alcohol, e.g. methanol, ethanol, derived from corn (maize) and other grains.
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Biogas: The generation of gas from animal dung or farm and household wastes. It provides a cheap source of energy, especially in rural regions in developing countries.
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Biomass energy: Energy available from organic material in the environment, that originated as solar energy absorbed by plants and was converted into chemical energy by photosynthesis. Biomass energy, mainly in the form of wood, was the main source of energy prior to the development of fossil fuels. It includes energy available in wood, crops, crop residues, industrial and municipal organic waste, food processing waste and animal wastes.
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Carbon dioxide (CO2): One of the major greenhouse gases. Human-generated carbon dioxide is caused mainly by the burning of fossil fuels.
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Carbon tax: A policy that would tax fossil fuels according to the amount of carbon they contained. This would reduce the demand for fossil fuels in general and cause a realignment away from coal to less polluting natural gas, or renewable sources of energy.
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CFC�s (Chlorofluorocarbons): A group of chemicals containing chlorine (Cl), fluorine (F) and carbon (C), sometimes referred to by their trade name Freon. These synthetic compounds were used extensively for refrigeration and aerosol sprays until it was realized that they destroy ozone (they are also very powerful greenhouse gases) and have a very long lifetime once in the atmosphere (more than 100 years). The Montreal Protocol agreement of 1987 has resulted in the scaling down of CFC production and use in industrialised countries.
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Coal: A black or brown combustible material composed of carbon (C), various carbon compounds and other materials such as sulphur (S). The most abundant of the fossil fuels, it was formed through the accumulation of vegetable matter over millions of years in environments (e.g. swamps, deltas) which reduced the rate of decay of the organic material and allowed the preservation of the solar energy to absorbed by it when it was growing. When coal is burned, it is that energy which is released.
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Cogeneration: The combined production of heat and power from one plant. The power is usually in the form of electricity and the heat in the form of steam produced from a single fuel source.
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Cogeneration: A facility in which two or more forms of energy are generated simultaneously or interchangeably. Commonly, a cogeneration facility produces steam for an industrial or commercial process and uses some of the steam to turn a turbine that generates electricity. Another type of cogeneration arrangement combines several energy sources in a single facility to provide a mix of energy forms (heat, electricity, etc.) in varying proportions according to the needs of the energy users.
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Combustion: A chemical reaction in which a substance combines with oxygen (O)(oxidation) to release energy in the form of heat and light.
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Conservation (nature): Protection against irreversible destruction and other undesirable changes, including the management of human use of organisms or ecosystems to ensure such use is sustainable.
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Converter: Unit that converts alternating current to direct current or visa versa.
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Current: Flow of electricity
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Development: A process of economic and social transformation that defies simple definition. Though often viewed as a strictly economic process involving growth and diversification of a country's economy, development is a qualitative concept that entails complex social, cultural, and environmental changes. There are many models of what 'development' should look like and many different standards of what constitutes 'success'.
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District heating: Delivery of steam or hot water through a network of pipes to heat a number of buildings in a district.
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Ecology: Originally defined by Ernst Haeckel in 1866, ecology is the study of the relationships that develop among living organisms and between these organisms and the environment.
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Electricity: The phenomenon associated with stationary or moving electric charges. Electric charge is a fundamental property of matter and is borne by elementary particles. In electricity the particle involved is the electron, which carries a charge designated, by convention, as negative. Thus, the various manifestations of electricity are the result of the accumulation or motion of numbers of electrons.
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Energy: The capacity to do work. Energy takes a variety of forms and can be converted from one form to another to meet specific needs. There is no simple universally accepted classification of energy forms, but most classifications include:
- kinetic - the energy possessed by an object in motion
- potential - the energy possessed by an object as a result of its position. A bag of flour on a shelf, for example, retains the energy expended to place it in that position. If the bag falls off the shelf the potential energy will become kinetic energy.
- thermal - heat energy
- electrical - the energy associated with an electric charge in an electric field
- chemical - the energy released during a chemical reaction
- nuclear - the energy released during nuclear reaction
- radiant - energy transmitted in the form of radiation
Energy can be converted from one form to another. The chemical energy in coal, for example, is converted into thermal energy through combustion, which in turn can be converted into electrical energy in a thermal electric power station.
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Energy budget: An accounting of the flow of energy through a system. Originally applied by ecologists to ecosystems, the approach is also useful in industry to check the energy efficiency of industrial processes.
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Energy conservation: Using less energy to achieve the same amount of work or decreasing the amount of fuel used to produce the same energy output. By reducing demand and improving energy efficiency, energy resources can be conserved.
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Energy efficiency: The percentage of total energy input that does useful work and is not lost or converted to low temperature, usually useless, heat. With the growing concern for declining energy resources, rising energy costs and the impact of large-scale energy consumption on the environment, the term refers to, for example, the willingness of society to change its user habits so that less energy is wasted.
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Environment: A combination of the various physical and biological elements that affect the life of an organism. Although it is common to refer to �the� environment, there are in fact many environments eg, aquatic or terrestrial, microscopic to global, all capable of change in time and place, but all intimately linked and in combination constituting the whole earth/atmosphere system.
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Environmentally-sound: The maintenance of a healthy environment and the protection of life-sustaining ecological processes. It is based on thorough knowledge and requires or will result in products, manufacturing processes, developments, etc. which are in harmony with essential ecological processes and human health.
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Ethanol: Ethyl alcohol (C2H5OH). One of the most common alcohols, traditionally produced by fermentation of the natural sugars in grain and fruit, and the base for many alcoholic beverages.
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Fossil fuels: Fuels such as coal, oil and gas made by decomposition of ancient animal and plant remains which give of carbon dioxide when burned.
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Fuel cells: Fuel cells are electrochemical devices that convert a fuel�s energy directly to electrical energy through a chemical reaction instead of combustion. Fuel cells operate much like continuous batteries when supplied with fuel to the anode (negative electrode). Fuel cells forego the traditional extraction of energy in the form of combustion heat, conversion of heat energy to mechanical energy (as with a turbine), and finally turning mechanical energy into electricity (e.g. using a dynamo). Instead, fuel cells chemically combine the molecules of a fuel and oxidizer without burning, dispensing with the inefficiencies and pollution of traditional combustion.
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Gasohol: A mixture of gasoline (petrol) and ethanol or methanol used as a fuel for gasoline-powered motors. Since ethanol and methanol can be produced from waste agricultural and wood products, the production of gasohol has been seen as a means of reducing energy loss caused when these materials are discarded, while at the same time reducing the demand for gasoline.
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Generator: Technology that produces electricity.
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Geothermal energy: Energy available in the molten and semimolten rocks beneath the earth�s crust. The high temperatures that this creates in adjacent solid rocks in certain areas causes sub-surface water to be superheated or converted into steam, which can be used for direct space heating or converted into electricity in a conventional power plant.
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Gigawatt: A billion watts, written GW
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Global warming: The idea that increased greenhouse gases cause the Earth�s temperature to rise globally.
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Green electricity: Refers to electricity produced by generators considered to have acceptably low environmental impact.
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Greenhouse effect: The cause of global warming. Incoming solar radiation is transmitted by the atmosphere to the Earth�s surface, which it warms. The energy is retransmitted as thermal radiation, but some of it is absorbed by molecules of greenhouse gases instead of being retransmitted out to space, causing the temperature of the atmosphere to rise. The name comes from the ability of greenhouse glass to transmit incoming solar radiation but retain some of the outgoing thermal radiation to warm the interior of the greenhouse. The �natural� greenhouse effect is due to the greenhouse gases present for natural reasons, and is also observed for the neighbouring planets in the solar system. The �enhanced� greenhouse effect is the added effect caused by the greenhouse gases present in the atmosphere due to human activities, such as burning of fossil fuels and deforestation.
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Greenhouse gases: Molecules in the Earth�s atmosphere such a carbon dioxide (CO2), methane (CH4) and CFCs which warm the atmosphere because they absorb some of the thermal radiation emitted from the earth's surface.
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Grid: Network of high-voltage transmission lines.
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Household fuel: Either gaseous (natural gas), liquid (fuel oil or kerosene) or solid (coal or wood) fuel used for domestic cooking and/or heating.
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Hydro-power: The use of water-power to generate electricity. Electricity produced by using the kinetic energy available in flowing water. Where the gradient of a stream is steep or a natural waterfall exists, the water can be directed through a turbine to drive an electric generator.
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Industrialization: A development path based on expanding a country's capacity to process raw materials and manufacture products for consumers, businesses, and export. This approach to development, first seen in northern Europe in the Industrial Revolution typically entails heavy financial investment in factories and power plants and a rapidly growing demand for energy, particularly fossil fuels.
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Integrated waste management: A strategy that employs several waste management methods, usually in the following order of preference: source reduction, recycling and reuse, incineration, and disposal in landfills.
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Kilowatt: Unit of power, 1000 watts, written kW
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Kilowatt-hour: Unit of electrical energy, written kWh
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Kinetic energy: The energy an object possesses as result of its motion. Kinetic energy is often produced by the conversion of other forms of energy. For example, the thermal energy obtained by burning coal can be used to produce steam that in turn provides kinetic energy through a mechanical device such as a piston engine or turbine. Moving fluids such as wind or water possess kinetic energy that can be used to drive windmills or hydroelectric generators.
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Landfill: A site designated for disposal of solid or chemical wastes by burial. It may be essentially an open pit or a highly-engineered facility that includes special linings to prevent wastes from leaking into water supplies.
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Megawatt: A million watts, written MW
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Megawatt-hour: One thousand kilowatt hours, written MWh
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Methane: A simple hydrocarbon gas (CH4) produced during the decomposition of organic material under anaerobic conditions. It is the main constituent of natural gas and therefore and important fuel.
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Montreal Ozone Agreement: An agreement signed by 24 nations in 1987 (and since then endorsed by more than 30 others), that set a timetable for the reduction of chlorofluocarbon and halon production levels by 50 per cent by the year 2000 to control damage to the ozone layer. The Montreal Ozone Agreement is considered a model of the global environmental diplomacy needed to address the more complex issue of the greenhouse effect.
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Natural gas: A mixture of hydrocarbons in gaseous from, found in pockets beneath the earth's surface, usually in association with liquid petroleum products. It consists largely of methane (CH4) (c. 85 per cent), but contains other hydrocarbons such as ethane (CH6) and propane (C3H8), and was formed as the result of the anaerobic decay of organic matter.
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Negawatts: A term coined by energy analyst Amory Lovins to signify that a unit of energy saved is exactly equivalent to an additional unit of energy supplied. If it is cheaper for a utility to save energy than to generate an equivalent amount of additional energy, the utility has more incentive to invest in negawatts than in megawatts.
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Non-renewable resource: A natural resource that cannot be replaced after it has been consumed. It applies particularly to fossil fuels, which can only be used once, but it also describes other mineral resources that are present in only fixed quantities in the earth�s crust, although metals can be reused through recycling. Central to the concept is human time frame. Oil and natural gas are being formed beneath the earth�s surface at present and new mineral ores are also being created. However, replacement may take millions of years, and society can consume them much more rapidly that they can be replaced. Thus in human terms they are effectively non-renewable.
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Nuclear power: Electricity generated by using heat from a nuclear reactor to produce steam for a steam turbine.
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Oil:
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OPEC: Organisation of Petroleum Exporting Countries. A group of Middle Eastern, Asian, African and Latin American nations that includes the world�s major petroleum producers and exporters. They came together in 1960, recognising the importance of oil as a source of future development, and with the intention of using their petroleum resources to advance their economic interests.
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Ozone: An unstable and chemically-reactive gas containing three oxygen atoms, formed at high altitudes by the action of sunlight on molecular oxygen. Present at low concentration in the stratosphere, ozone absorbs ultraviolet radiation from the sun and reduces the amount of this damaging radiation that reaches the Earth's surface. Ozone is also formed at ground level - by the interaction of sunlight with exhaust gases from automobiles and industry, and by the action of sunlight on nitrogen oxides and hydrocarbons-where it is a primary component of smog that aggravates breathing problems and damages plants.
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Ozone hole: A popular name given to a phenomenon discovered in 1987, when scientists measured unexpectedly low ozone concentrations in the stratosphere above the South Pole during the Antarctic spring. It is now generally accepted that the loss of stratospheric ozone is caused by chemical reactions initiated by chlorofluorocarbons.
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Petrochemicals: Chemicals derived from oil and natural gas � for example, ethylene, propylene, toluene � which act as feedstocks for the manufacture of products such as plastics, pesticides, fertilisers, antiseptics and pharmaceuticals. Petrochemicals play a very important role in modern society, but they also create pollution problems. Plastics are a major component of solid waste, for example, fertilisers contribute to eutrophication of lakes and rivers and pesticide residues in food and water present health problems.
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Petroleum: A mixture of naturally occurring hydrocarbons, that may exist in a solid (e.g. bitumen), liquid (e.g. crude oil) or gaseous state (e.g. natural gas). It commonly contains variable amounts of other chemicals such as sulphur (S) and nitrogen (N). Petroleum is the end-product of the partial decay of living organisms which once inhabited the world�s oceans. As they died they sank to the bottom of the oceans, where the anaerobic conditions allowed them to be preserved.
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Photovoltaic (PV) cells: Thin silicone wafers that convert any light, not only sunlight, directly into electricity.
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Pollution: An undesirable contaminate (gas, liquid, noise, solid) which has been released into, and is now a part of, the environment.
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Power: The amount of energy delivered in a unit of time, measured in watts, written W
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Power station / power plant: One or more large generators, connected through a switchyard to an electricity system.
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Primary energy: Energy sources, such as fossil fuels, nuclear or wind power, which are not used directly for energy but transformed into light, useful heat, motor power and so on. For example, a coal-fired power station which generates electricity uses coal as its primary energy.
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Proper resource pricing: The pricing of natural resources at levels which reflect their combined economic and environmental values.
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Radiant energy: Energy transmitted in the form of radiation � i.e. as rays, waves, or streams of particles. The main source of radiant energy in the earth/atmosphere system is the sun.
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Renewable energy: Energy from natural sources, that can be replaced as it is used or at least within a very limited time frame. Renewable energy is supplied by flowing water, wind, biomass and the sun.
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Renewable resource: A resource that is replaced at the rate which is faster than, or at least as fast as, it can be used. The oxygen (O) in the air, the plants and animals in the environment, the water in the hydrological system and energy from the sun are all renewable.
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Solar energy: Radiant energy produced in the Sun as a result of nuclear fusion reactions. It is transmitted to the Earth through space by electromagnetic radiation in quanta of energy called photons, which interact with the Earth's atmosphere and surface. Since the sun is a very hot body, radiating at a temperature of about 57000 K, the bulk of the radiation is high energy at ultraviolet and visible light wavelengths.
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Solar thermal energy: Energy produced by using the sun's rays to heat a gas or liquid that then performs useful work, such as powering an electrical generator. Electricity from solar thermal power plants is now nearly competitive in cost with electricity from conventinal fossil-fuel power plants.
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Subsidy: A financial benefit or form of assistance given to producers (e.g., grants, loans, tax allowances)which enables them to sell or export goods at less than their costs of production, thus creating unfair competition.
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Sustainable development: Sustainable development has as many definitions as subscribers. In essence, it refers to economic development that meets the needs of all without leaving future generations with fewer natural resources than those we enjoy today. It is widely accepted that achieving sustainable development requires balance between three dimensions of complementary change:
- Economic (towards sustainable patterns of production and consumption)
- Ecological (towards maintenance and restoration of healthy ecosystems)
- Social (towards poverty eradication and sustainable livelihoods)
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Thermal electric power station: An electricity generating station in which the electricity is produced by burning coal, oil or natural gas, with coal being the most common fuel used. The thermal energy released when the coal is burned is used to heat water and produce steam, which is directed under pressure through turbines. These in turn power generators to produce the electricity.
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Tidal/wave power: Power that can be generated in coastal locations from the twice-daily ebb and flow of the tides. As the tide rises, water is allowed to flow through gates in the dam to fill the basin behind it. At high tide the gates are closed and as the tide falls the water in the basin is retained behind the dam. Once a sufficient head of water is built up, the water behind the dam is released and the potential energy it possesses is converted into kinetic energy which drives generators to produce electricity.
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Turbine: Rotary engine that converts the energy of a moving stream of water, steam, or gas into mechanical energy. The basic element in a turbine is a wheel or rotor with paddles, propellers, blades, or buckets arranged on its circumference in such a fashion that the moving fluid exerts a tangential force that turns the wheel and imparts energy to it. This mechanical energy is then transferred through a drive shaft to operate a machine, compressor, electric generator, or propeller. Turbines are classified as hydraulic, or water, turbines, steam turbines, or gas turbines. Today turbine-powered generators produce most of the world's electrical energy. Windmills that generate electricity are known as wind turbines.
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Utility: A public or private company that supplies a basic service to the general public, such as electricity, gas, or water.
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Volt: Unit of electrical pressure, written V
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Voltage: Electrical pressure between different points in a circuit, measured in volts, written V
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Waste-to-energy incinerator: An incinerator that uses waste products as fuel, to provide energy for space or water heating. Various types or refuse are used, from simple paper products to plastic and scrap car tyres. In many cases they are used as fuel supplements, since on their own they have an energy content that may be only 30 to 50 per cent that of solid fuels.
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Watt: Unit of power, written W
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Wind energy: Energy from moving air which is converted to electricity, by using wind to turn electricity generators. Wind energy has a number of advantages over conventional forms of energy. It is pollution-free and renewable.
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Wind farm: A cluster of wind turbines (up to several hundred) for generating electrical energy, erected in areas where there is a nearly steady prevalent wind; such areas generally occur near mountain passes.
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World Commission on Environment and Development: Established by the United Nations General Assembly in 1983 to examine international and global environmental problems and to propose strategies for sustainable development. Chaired by Norwegian Prime Minister Gro Harlem Brundtland, the independent commission held meetings and public hearing around the world and submitted a report on its inquiry to the General Assembly in 1987.
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World Summit on Sustainable Development (WSSD): The World Summit on Sustainable Development takes place from 26 August - 4 September 2002 in Johannesburg, South Africa. Governments, UN agencies, and civil society organisations will come together to assess progress since the UN Conference on Environment and Development held in Rio in 1992 (hence the title 'Rio + 10' for the Johannesburg meeting). Sustainable development is defined in the report from the Rio meeting as being 'economic progress which meets all of our needs without leaving future generations with fewer resources than those we enjoy'.
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