Drinking rainwater from banana leaf, Nigeria. (c) I. Uwanaka/UNEP peopleandplanet.net
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Drinking rainwater from banana leaf, Nigeria. (c) I. Uwanaka/UNEP
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renewable energy > factfile

Energy: supply and demand
Global energy use doubled between 1971 and 2005. Energy demand has risen at just over 2 per cent per year for the past 25 years (more than the rate of human population growth) and will continue to climb at the same rate over the next 15 years if current use patterns persist, according to the International Energy Agency (IEA). ... more

Fossil fuels and carbon emissions
Fossil fuels account for some 80 per cent of the world�s primary energy consumption and supply roughly 90 per cent of the world�s commercial energy. By 2010, global energy consumption will have risen by almost 50 per cent from 1993 levels, and unless successful efforts are made to reduce them, annual CO2 emissions will rise by the same proportion. The developing nations� share of commercial energy consumption is expected to grow from one-third to nearly 40 per cent by this date. ... more

Nuclear power is not a renewable energy source. It can provide energy without emitting conventional air pollutants and greenhouse gases, although the nuclear fuel cycle does release CO2 during mining, fuel enrichment and plant construction. But although nuclear energy dominates electricity generation in some countries (78 per cent in France) and accounts for 16 per cent of electricity world-wide, its initial promise has not been realised. It is more costly than originally projected, competition from alternative technologies is increasing, and there are concerns related to safety, radioactive waste management, and potential nuclear weapons proliferation. ... more

Large-scale hydro power supplies 20 per cent of global electricity, and is currently the largest source of renewable power. It is a �clean� power source, in that it does not generate air pollution or carbon emissions, and has low maintenance costs, but in the industrialised countries it has nearly reached its economic capacity and it scope for expansion is very limited. ... more

Wind power
A wind turbine converts the energy in the wind into electrical energy or mechanical energy to pump water or grind grain. Wind turbines are rated by their maximum power output in kilowatts (kW) or megawatts (MW - 1000 kW). For commercial utility-sized projects, the most common turbines sold are in the range of 600 kW-1000 kW (one megawatt) � large enough to supply electricity to 600-1000 homes. The newest commercial turbines are rated at 2 megawatts. A typical 600 kW turbine has a blade diameter of 35 metres and is mounted on a 50-metre concrete or steel tower. ... more

There are a variety of technologies which have been developed to take advantage of solar energy. These include concentrating solar power systems, passive solar heating and daylighting, photovoltaic systems, solar hot water, and solar process heat and space heating and cooling. ... more

Wood and other vegetation (biomass) is an important source of fuel in the production of biogas, bioethanol and other biofuels. Biomass accounts for about 15 per cent of global primary energy use and 38 per cent of the primary energy use in developing countries, where it is mainly used for cooking and heating (fuelwood). The main sources of biomass include: ... more

Hydrogen is one of the most promising energy carriers for the future. It is a high-efficiency, low polluting fuel that can be used for transportation, heating and power generation in places where it is difficult to use electricity. Liquid hydrogen is the fuel that has propelled the space shuttle and other rockets since the 1970s, and hydrogen fuel cells power the shuttle�s electrical systems, producing water as a by-product. ... more

Geothermal energy is the thermal energy contained in the rock and the fluid within the rock in the earth's crust. It is believed that the ultimate source of geothermal energy is radioactive decay occurring deep within the earth. ... more

The World Energy Council says that the oceans can supply more than two times the energy the world currently consumes. The tidal movements of the oceans are caused by the gravitational pulls of the moon and the sun, and involve enormous amounts of energy. If this could be tapped, it could provide a large portion of the energy mankind uses, but to date it has only been harnessed on a relatively small scale. Tidal mills have been used for centuries. These were water wheels located in estuaries, where the water is trapped in the mill pond at high tide and then released through the wheel at low tide. Wave power can also potentially be harnessed. ... more

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