SIMPLY - EnergyNo single energy system is perfect. But some are a good deal better than others. Future energy use is likely to consist of a mix-and-match approach - ideally, phasing out conventional sources and bringing in a range of non-polluting renewable options.
Small-scale systems tap the energy of flowing water. These are not to be confused with big dam projects which totally transform ecosystems, wreaking environmental havoc.
Very simple, cheap technology
Suitable for remote and hilly regions
Produces cheap electricity
Needs a sharp drop and regular, flowing water
Needs to be small scale not to damage the environment
An ancient source undergoing a revival with modern turbine technology.
Plentiful, renewable supply
Suitable for less sunny regions
Dovetails well with other systems
Produces cheap electricity
Safe if properly maintained
Windfarms make noise in quiet places
Biomass is vegetal or organic material - including dung and plants - and biofuels are the solid or liquid or gaseous fuels that derive from it. Wood, methane and alcohol are all biofuels.
Ideal for rural communities
Recycles waste, including sewage
Fertilizer as by-product
Biofuels are less polluting fossil fuel alternatives
Specially-grown agricultural biomass could compete for land with other crops
Reliance on woodfuel contributes to deforestation
Some pollution from burning biofuels but no more carbon dioxide than would have been produced anyway by natural processes
This energy comes from the heat stored in rock below the earth's surface. The heat is 'mined' by drilling a bore hole and used to generate electricity or to heat water.
Relatively clean, non-polluting
Safe and inexhaustible
Cost effective and growing fast
Suitable sites exist in many parts of the world
Drilling is noisy and disposal of drilling fluids requires large lagoons
Produces small amounts of carbonate, chloride and sulphide pollution
The sun's power can be harnessed in various ways: by using photovoltaic cells to generate electricity directly; by using thermal collectors to make steam to generate electricity; by using passive solar materials that maximize or retain the sun's heat.
Renewable, endless supply that belongs to no-one
Operates best in the sunniest - often the poorest - parts
of the world
Dovetails with other clean systems, eg windpower, hydrogen
Flexible and modular - means systems can be any size
Research and development underfunded
Electricity produced is more expensive
Cannot be used as the only system in cloudy places
Energy has to be stored in batteries, hydrogen, water or other matter
Currently produced by 'fission'. An atom is split - using uranium - and the heat produced drives steam turbines to generate electricity.
Massive investment already committed
Does not cause global warming or air pollution
Nuclear accidents and radiation leaks cause cancers and other fatal disorders.
Legacy of radioactive waste that remains 'live' for
Decommissioning old power stations very costly
Expensive way of generating electricity
Tidal energy is harnessed by building a barrage across an estuary. At high tide the barrage traps a head of water which is released at low tide to drive turbine electricity generators.
Produces cheap power
Clean, renewable, safe
Low running costs
Water behind a barrage is clear and more biologically productive
Barrages protect against floods and storms
Lots of potential worldwide
Set-up costs are high
Tidal power comes, usually, in two daily bursts
Tidal barrages have to be carefully situated to be efficient
Large barrages affect estuary ecosystem
Derived from long-dead organic and animal matter. Oil, coal, natural gas are all fossil fuels.
World economy geared to fossil fuels
They are practical
All produce greenhouse gases that cause global warming
Oil produces toxic fumes causing air pollution, asthma and
Coal produces acid rain, air pollution and acute respiratory diseases
Sources: The Future of Energy Use by Robett Hill et al, Earthscan, London 1996. Renewable Energy: Power for a Sustainable Future ed. Godfrey Boyle, OUP/Open University 1996.
Illustrations by EARL DUKE
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