Harness the power of wind

Farm Weekly
Thursday 26/10/2006, Page: 26

THE world has never been short of wind; for thousands of years it has turned windmills, flown kites, cooled houses and filled sails. Now, technological advances are breathing new life into the use of wind power as a clean, renewable, cost-effective means of generating electricity.

The first electricity-generating wind turbines were invented in the US and Europe in the late 1800s. In the early 1900s, as electricity became more widely available in towns and cities, many rural communities and homesteads turned to small-scale wind turbines for their electricity supply.

Many were built on-site, using old car generators and hand-carved rotor blades or old biplane propellers. Despite continued popularity in remote areas, wind power has not really had much puff as a means of generating electricity for the masses.

But the industry is growing; much of the growth is in European countries such as Holland, Denmark, the UK red Germany. Denmark, for example, currently obtains about 5pc of its electricity from wind turbines and aims to increase this to 40pc by 2030.

Interest in wind power is also growing in countries such as India and China, and Australia is paying increasing attention to the concept. There are probably two main reasons for the increasing interest in wind power. First, most electricity generated today uses non-renewable fuels such as coal, oil and gas. These contribute vast quantities of carbon dioxide to the atmosphere, which many scientists think cause an enhanced greenhouse effect, leading to a warming of the earth's atmosphere.

The second reason is that advances in wind power science and technology are reducing the cost of wind power to a point at which it is becoming competitive with many other energy sources (at about 8-10c/kw). The world has long been searching for a non-polluting, renewable source of energy that is as cheap as coal and oil.

In a coal-fired power station, chemical energy stored in coal is converted first to heat energy by burning and then into kinetic energy (energy of motion) by heating water to produce steam. A high-pressure jet of steam is used to turn a turbine (mechanical energy), which is then used to turn a generator to produce electrical energy.

In generating electricity from wind, the chemical and heat energy steps are not needed: the kinetic energy of-the wind turns the turbine (or blades), which then turns a generator to produce electricity. The power available from a wind turbine increases rapidly with wind speed: a doubling of wind speed results in as much as an eight-fold increase in power.

Therefore it is important to site wind generators in a place where the wind speed is high, as well as reasonably constant. The length of the rotor blades is also important: doubling the diameter of the circle made by the blades produces a four-fold increase in power.

A drawback to wind power is that the wind can be erratic, changing direction by the hour. There may be no wind at all one day and a howling gale the next. It may blow hard at times when electricity demand is low, and be a mere gentle breeze when demand is high. But many of the problems of wind power are now being solved. It could supply a significant proportion of the nation's electricity needs - just as long as the wind keeps blowing.