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Alternative Energy

  It has become apparent over the past thirty years that the total energy from a fuel source has to be maximized to its full potential, in order to save money and mineral resources. As this fact becomes clearer governments and individuals have begun to look at different propositions in order to save on energy costs.

At this present time the main sources of energy available to the Westernized culture are oil, gas, coal and nuclear power. With the environmental problems as well as the finite supplies of the four energy sources, more time and research is being spent on alternative sources of energy.

Direct or active solar energy may be exploited in various ways, including the direct production of heat for water and space, the growing of crops which can be processed into other forms of energy (biomass route) and the production of electricity using solar panels. The use of active solar-powered systems using collectors of one form or another are only viable in countries with warm climates and plenty of sun. Solar-powered power stations have been built, notably in southern France and California (where the largest solar power plant, ‘Solar One’, is in operation with a peak output of 10MW).

In northern European countries a more important facility is the use of passive solar power. This manipulates the form and fabric of the building to maintain comfortable internal surroundings for its users. As well as saving on energy costs, passive solar design frequently adds to the amenity of the structure of the building, such as the introduction of glass atriums in shopping malls.

As the Sun is the only source of energy (apart from fusion) at the present moment, the use of solar energy (passive or active) must be seriously considered. Another source of energy directly from the Sun is wind power. The driving force of the wind is the solar radiation interacting between the Earth\'s surface and atmosphere. It is this interaction that determines the character of high altitude winds. In the first few hundred metres above the Earth\'s surface there exists a turbulent layer, known as the boundary or mixing layer. All wind turbines operate within the boundary layer, and it is important that the turbines are sited as high as possible in order to capture as much energy as possible. The siting of wind farms on high hills has been the bane of many environmentalists who argue that natural beauty spots are being destroyed in order to supply energy.

Wave energy on the other hand overcomes the problem of scarring the landscape by placing the wave turbines far from shore. The advantage in using wave or wind power is that there is good seasonal matching between power supply and demand. The major drawback with wind and wave power is the lack of control engineers have over the power supplied.

The use of water is also seen in hydroelectric power stations and tidal power stations. A typical hydroelectric scheme uses a dammed river or lake to provide a reservoir that supplies a steady flow of water to drive turbines. In areas where the demand for power fluctuates, pumped storage plants may be installed, where the surplus power created during off-peak times is used to pump water back into the same or maybe a different reservoir. Tidal power uses reversible turbines that both manipulate the flood and ebb tides. At high tide sluice gates are closed, creating a reservoir in the tidal basin. The water can then be released at will. The largest tidal scheme in La Rance, France can produce 240MW, enough to satisfy the needs of a city of several hundred thousand inhabitants. Both systems (hydroelectric and tidal) can produce vast amounts of controllable energy, and the potential to use this renewable source energy must be maximized.

Another important source of alternative energy is the use of biomass (vegetable matter). Wood, crop residues and animal dung provide 40% of the energy used on the planet. In many developing countries they are the only source of energy with emphasis now being placed on the planting of fast-growing trees in order to supply firewood. Biomass is also being converted into alcohol which is being used as fuel for internal combustion engines when mixed with petrol.

As well as the use of biomass, domestic and commercial rubbish is being burned to provide heat for ‘district heating schemes’. Such schemes are already in operation in Scandinavia where the energy produced in burning the refuse is used to heat water in pipes which eventually finds its way to nearby homes and offices. Even waste that is dumped into the ground yields useful energy. The decomposition of such material produces heat and methane, both of which can be used. Sewage when treated yields methane gas which can be used for cooking and heating. The sewage is deposited in ‘biogas plants’ and bacterial action produces the gas. Twenty million people in China use such a system.

Geothermal power is limited to countries where it is relatively easy to tap into the hot water that is heated by radioactive decay of elements below the Earth\'s surface. Places such as Iceland and New Zealand use their geothermic power to drive turbines and heat homes and factories directly. At present only such countries such as Iceland exploit this source of energy, but the technology exists to supply all the energy needs of the world for hundreds of years. Boreholes such as those drilled in Cornwall, in the UK, produce enough energy to drive turbines which generate electricity.

The use of renewable energy sources have to be taken seriously as the stocks of fossil fuels fall. With sensible conservation and the implementation of better insulation and waste heat recovery, it will be possible for the Earth to provide all of our energy requirements for centuries to come. AA

Further reading R.H. Taylor, Alternative Energy Sources.



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