Many countries, including the United Kingdom, take a simplistic attitude to wind generated electricity. They rather regard it as an unconditionally good thing and use vast amounts of taxpayers’ money in incentivising it. But things are not so simple; wind has plenty of advantages but also plenty of disadvantages.The first problem is to understand exactly what wind energy provides. With remarkable but perhaps intentional confusion wind turbines are usually subsidised on the basis of so much per kWh of installed power rating. Turbines reach their installed power when the wind blows at 28 miles per hour, which is 6 on the Beaufort Scale. At lower speeds the energy generated is lower; exponentially so. Not many places reach a wind speed of 28 mph, which is just shy of storm force. If the wind speed halves from 28 mph to 14 mph, the energy generated is not reduced by half, but by an eighth. If the wind speed doubles to 56 mph, the turbines do not produce eight times more electricity, but shut down, for safety reasons, producing no electricity.
Germany, which has invested heavily in wind turbines, has an average wind speed (when it is windy) of about 6 mph, so the average wind turbine generated electricity is less than 10% of the wind turbine’s rating.
As a wind turbine operates it removes energy from the wind converting the energy into electricity. Air flow behind the turbine is like a wake of a ship – turbulent and not terribly useful in terms of providing more wind energy to the next turbine. For that reason turbines should be located at least five rotor diameters apart (none rotor diameters is ideal), otherwise they will be operating at a reduced rate in all windy conditions.
Wind turbines also only generate electricity when it is windy, and it is not windy all the time. There is no environmentally friendly way of storing electricity, so it will, like all renewable energy, provide some electricity when none is needed and provide no electricity when some is needed. Pump storage facilities for a windless week would take up far too much land to be viable economically or environmentally, so some means has to be found for generating electricity on windless days.
This disadvantage is overcome by using traditional power stations as a backup, and if a gas power plant is used for back up there will be lower emissions than coal or oil. Nuclear energy is not suitable for back up because of the lengthy time it takes to turn on and on a nuclear power plant.
Interestingly in Germany with its many windy turbines not a single traditional power plant has closed. In fact on 4th November 2006 much of Denmark and Germany lost electricity supplies when widely fluctuating wind produced electricity made the grid unstable and it shut down.
Of course wind turbines have one advantage- they produce clean and almost carbon dioxide free electricity. They are good at doing that when the wind blows and we should not take the marketing propaganda for the wind turbine industry too seriously; wind turbines produce good clean power, but not always and not in predictable quantities.
This then leads to the question as to why so many nations have invested so heavily in wind power which suffers from the problem of being unable to store the power in times of plenty and use it in windless conditions. Perhaps the real reason is the strength of the wind lobby, its access to governments looking for a cheap solution to climate change, when no cheap solution exists.
I have no doubt that if these wind investing nations had invested in small scale solar thermal systems (heat is easy and cheap to store) they would burn less fossil fuel and provide heat energy in a more cost effective way. The money invested in wind turbines would produce more useful energy than wind if it were spent on solar thermal not just for hot water but also for heating.