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What is renewable energy?
Renewable energy, as the name suggests, is energy that does not ‘run out’. The main forms of renewable energy are: HEP ( Hydro Electric Power), solar, tide, wave, biomass, geotherm and wind. All these forms can be used to generate electricity. HEP, wind, tide and wave energy use kinetic energy (movement energy) to turn turbines to generate electricity. Biomass uses burning plant material to produce heat and geotherm uses the natural heat from the earth to produce steam to turn turbines to generate electricity. Solar energy uses sunlight to generate electricity either by the use of photovoltaic cells fixed to roofs and walls or by using mirrors to focus sunlight or solar thermal collectors to absorb heat from the sun (solar thermal energy).

Renewable energy is more dependent on location than non renewable energy (e.g. geotherm is appropriate in Iceland and New Zealand but not Scotland). Scotland is suitable for HEP, wind, tide and wave but not so suitable for solar. It is therefore particularly suitable for decentralized distribution of energy using multiple sources of generating energy (see Factsheet 5, Poster 2 and Article 2).

Only three centuries ago, renewable energy sources provided virtually the entire global energy supply.

What are the consequences of using renewable energy?
Cost of production: HEP
Main costs are: land, building a dam and power station. Maintenance.
The most important renewable energy source for electricity generation at present. 17% of worldwide electricity demand was supplied by hydro-electric power in 2001. However the scope for further development may be limited.
Cost of production: wave and tide
Main costs are: building apparatus. Maintenance.
The first and largest commercial construction to use tidal power is a tidal barrage at La Rance, Brittany, which has been refurbished to extend its operating life for many years. Other technologies to derive energy from tidal and wave-power are generally in the experimental stage at present.
Cost of production: wind
Main costs are: building apparatus, land . Maintenance.
The amount of wind power installed worldwide has grown rapidly since the mid-1990s. If the growth rates of wind power are maintained over the next two decades, wind power could become the most important renewable energy source for electricity generation.
Cost of production: solar
Main costs are: building apparatus.
Although the electricity generated by solar power (photovoltaics) at present is much smaller than that generated by wind power, its use is growing at about the same rate, and particularly in Japan. Its cost is decreasing much faster than the cost of wind power. The potential of solar thermal power plants is enormous but the installation rates are still relatively low.
Cost of production: biomass
Main costs are: growing fast growing plants. Maintenance.
By 2000 the percentage contribution of biomass energy to the world's energy demands had decreased from over 70% in 1860 (wood-burning is a form of biomass energy) to about 10%. It remains the second most important renewable energy resource for electricity generation today. However, without large-scale development, biomass energy in the future is likely to be limited to niche markets.
Cost of production: geotherm
Main costs are: building apparatus. Maintenance.
As stated above, suitable for only some countries. In Iceland, El Salvador and the Philippines geothermal power plants produce about one fifth of the total electricity.

Environmental impact
Biomass will release greenhouse gases into the atmosphere. HEP involves building dams and flooding the valley behind the dam, it also has an impact on the river flow downstream. Wave and tide equipment can look unsightly and restrict shipping. Wind farms can look unsightly in some people’s view and there is some noise. There may also be a danger to birdlife (birds can become trapped in or damaged by the turning blades).

To a greater or less extent, wind, tide, solar and HEP are dependent on natural variations such as wind. Geotherm and biomass are more controllable. It is questionable whether one source of renewable energy could meet all energy needs either present or future - a combination of sources is more likely.

Political Issues
It is difficult to compare the efficiency of renewable energy with non renewable energy. The amount spent on research and development of renewable energy has been very small compared to research into nuclear energy. Two facts remain in the political debate:
1. non-renewable energy sources WILL run out (see Factsheets 1 and 2).
2. non-renewable energy sources are much more polluting compared to renewable sources.

page last updated 31 May 2006


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