Introduction - Types of renewable energy - Biomass
Current patterns of energy supply and consumption are unsustainable in the long term. Fossil-fuel reserves are finite and thier consumption is polluting.
The UK is currently responsible for the release of about 3% of the worlds global greenhouse gases, despite having only 1% of the worlds total population. The UKs energy industries are its largest single contributors to greenhouse gas emissions. The increased use of renewable energy resources is thought to be vital if sustainable energy and consumption are to be a feature of the future.
Types of renewable energy - Biomass
Living plants and decaying vegetable matter comprise the greatest bulk of the Earths biomass. Biofuel is that part of the biomass that can be converted into energy. At its simplest this involves burning fuel wood, dung, and crop residues for cooking, in less developed countries, but this is quite inefficient. Modern techniques involve gasifiying the biomass and burning the gas released. In more developed countries biofuels also include the methane that is harvested from landfill sites and municipal waste. Biofuels create lower levels of pollution than tradtional fossil fuels.
The earth recieves massives amounts of energy from the sun as incoming radiation. Some of this is lost on passing through the atmosphere but overall the surface has a net gain of energy. There are variations in energy and heat between different latitudes. The tropics have a net surplus of energy, mainly due to thier relative proximity to the sun, but high latitudes have a net deficit. Overall, although the potential for harnessing the suns energy is enourmous, the locations where the greatest amounts of solar energy could be harvested are often great distances from major centres of population.
At present the inital investment required for solar energy is high and conversion efficency is relatively low. Although development is on goin, solar power is most viable on a small scale. Many householders living in sunny Mediterranean climates use solar roof panels to heat thier water and homes and large-scale solar power stations have been built in california and spain. However, the UK sunshine is less reliable and the potential for large-scale development of this power source is limited under current levels of technology.
Wind power is the fastest growing renewable energy source. Many countries particularly in Europe and North America, are seeking ways of developing wind power as one of thier major sources of renewable energy.
Electricity is generated from the wind using a wind turbine. It is more economical of several turbines are sited in the same place in the form of a wind farm. As objections are sometimes raised to building wind farms in upland areas, wind energy companies have started to look for offshore sites, where larger capacity turbines can be used.
Wind energy is pollution free and does not contribute to global warming. In Europe and North America, wind tends to blow strongly in winter when demand for electricity is at its highest. Wind farms do not take up alot of space (appox. only 1% of the land they are sited), which allows farmland or natural habitats to exist around them. Electricity generation by wind energy is becoming increasingly competitive with coal-fired plants and is cheaper than nuclear fuel. Is is still not as cheap as gas-fired power stations, but wind energy costs are likely to go down in the future. Supporter of wind energy maintain that is represents on excellent example of sustainability.
Wind energy 2.
Opponents of wind farms claim that many of the windiest sites are also areas of natural beauty. They argue that wind turbines are an unwelcome intrusion into the landscape and an eyesore. Some people are worried about the noise the turbines create, particularly as wind farms are often sited in quiet locations; the damage they could inflict on wildlife (specially birds); and the potential effect on property prices. Critics also point out that wind farms require large areas to produce only a small amount of energy. It can take over 7000 wind turbines to produce the same amount of energy as one nuclear power station. If wind energy is to be viable, a lot of wind turbines will have to be built.
Wave power is one of the least developed renewable energy sources and is thought to be 10years behind wind power in development terms. Although offshore devices have tremendous potential in terms of the amount of electricity that could be generated, at present they are too expensive to implement on a large scale. In addition, the development of such schemes could create negative environmental changes in tidal basins.
A number of small scale schemes have been developed in the UK, including the Pelamis device off the Orkney Islands and Limpet off the island of Islay, Scotland.
This renewable souce of energy uses the movement of the tides to create power. Areas with the greatest tidal range offer the best potential for development and several sites have been suggested for the UK including the Severn and Mersey estuaries, Solway Firth and Morecambe Bay. Schemes with reversible blades could harness the power of both incoming and outgoing tides. The major drawback of tidal power is cost, in both economic and environmental terms, and this might explain why few sites are in operation. Arguements for tidal power include:
- it is renewable
- it is reliable and predicatable
- its large size - the projected Severn barrage would provide the same amount of energy as five nuclear power stations
- it is non polluting
- it benefits the estuary as erosion rates are reduced behind the barrage
The arguements against are:
- flooding of wetlands bordering estuaries, often home of many species of migrating birds, is damaging
- it could have an adverse effect on spawning fish such as salmon
- concstruction costs are extremely high.
Geothermal energy. 1
Geothermal power is derived from the hot rocks beneath the surface of the Earth. Although it is a renewable source of energy with tremendous potential for energy generation in the future, geothermal power is not entirely 'clean' resource as pollutants such as hydrogen suphide are present in the steam and heated water.
At present, most large-scale geothermal power stations operate on the steam that occurs naturally in geyers and hot springs. Steam can also be created artifically. Cold water is pumped down boreholes, where it becomes heated by contact with hot underlying rocks and turns to steam. This steam then returns to the surface and is used to generate electricity.
Geothermal energy. 2
Geothermal power is used in a variety of locations around the world, particularly in areas that are active tectonically such as the USA, Iceland and New Zealand. In Iceland geothermal heat is provided to homes, open-air swimming pools and greenhouses.
In the UK small scale projects such as the Southampton District Energy Scheme have been developed. In 1986 the council began pumping heat from a geothermal borehole, comissioned initially by the Department of Energy and started to use this to provide heating and cooling services. This scheme, which started with a single customer now has thousands of consumers. It provides heating and cooling to over 1000 homes, several large office buildings, a hospital, BBC tv studios, one of Europes largest shopping centres and a swimming diving complex. Southamton city council is comitted to the implementation of alternative sources of energy and aims to substantially reduce greenhouse gas emissions. The further expansion of local geothermal power will help it do so.
Appropriate technology for sustainable development
Sustainable development - is defined as 'development that meets the needs of the present without conprimising the ability of future generations to meet thier needs'. Energy resources should be seen as an asset, a stock of available wealth. However, if the present generation spends this without investment for the furture the world will run out of resources. If some of the wealth amassed from finite resources is used on research and development, sustainable development can be achieved. Ways in which this might happen include:
- the development of renewable sources of energy
- increasing the effiency of existing technology
- paying attention to environmental degradation and pollution caused by energy production
- government policies to encourage sustainable development.
Appropriate technology for sustainable development
The term appropriate technology is used in relation to less developed countries. It means the technical expertise and equipment being used are suited to the economic and technological levels of devlopment in a country. Sudan in east Africa is one of the poorest places in the world in terms of its economic and social development, and intermediate technology might be more appropriate to the needs of its people than high-tech energy generation.
In more developed countries, where levels of wealth are much higher, it is the responsibilty of governments and large-scale corporations to invest in sustainable methods of energy production for the future.