Colin's Cornucopia

Welcome to my world of discovery

Tilting At Windmills

Return to Energy

9th July 2011

The Institution of Mechanical Engineers and the Institution of Electrical Engineers are the two senior engineering institutions in Britain and their members will implement whatever energy strategy is decided upon nationally. A letter from Bill Hyde of Kent in this week’s issue of the Professional Engineer published by the Institution of Mechanical Engineers gave some interesting facts.

On 20th December 2010 an anticyclone surrounded Britain and gave excellent overall wind speeds around the country and surrounding seas. The installed capacity of 2,500 Megawatts of wind powered generators provided 61 Megawatts or around 2.44 percent of its capacity. By contrast our coal, gas, oil and nuclear generators are expected to give around 97% output under normal conditions and around 60% over their complete lifetime.

The demand that December day was 60,000 Megawatts so the wind provided one tenth of one percent of load. The opportunities for onshore wind farms are now few and far between and offshore windmills are very expensive to build, install and maintain. To run our country entirely on wind would require an installed wind base approximately 1000 times as big as the present facilities. This is clearly ridiculous but nobody actually expects wind to provide more than about 20 percent of our demand.

Michael Knowles of Cheltenham informs us that the government provides subsidies within its Renewables Obligation that top up the payments for energy to £150 per MWh for offshore windmills and £100 per MWh for onshore wind energy. The cost of offshore wind is currently estimated at £174 per MWh.  This cost estimate assumes a load factor of 30% but we have already seen in the best of likely conditions wind is only achieving 0.1%. As the wind is “free” the costs are all down to capital, operating  and maintenance. Does this not imply, then, that the true cost of offshore wind is actually £17,400 per MWh? I think we can expect a lot of wind farm operators to go broke quite quickly.

My electricity supplier currently charges almost exactly 10p per KWh or £100 per MWh. I know charges are escalating rapidly but this provides a ball-park base at which the energy companies can make a sensible profit. At 60% load factor this implies an industry wide turnover that December day of £3,600,000 per hour or £31.5 billion per year.

If the installed capacity is 100,000MWh operating at 60% load factor and basic cost of £90 per MWh is changed to incorporate 20% wind energy at £17,400 per MWh the resulting base cost becomes £3552 per MWh installed. The implication here is that the true cost of wind energy is more than thiry nine times the cost of conventional electricity generation.

Another factor is that currently we have, just, adequate installed conventional capacity. When the wind blows well, the vital coal, oil, gas and nuclear generators have to cut back their production to exactly balance supply and demand. The nature of electricity does not, essentially, allow storage. The conventional generators are therefore losing income to the government subsidised wind generators. The unit costs of the conventional generators are thereby increased and we can expect the increases to be passed on to consumers in the form of higher unit charges.

There are already reports of banks of windmills producing wind 'shadows' - that is areas of low energy wind movement behind the windmills. This is already seen as a limiting factor in the siting of groups of windmills. But no one knows what effect removing all this energy from the weather system will have. It is certain there will be an effect - and it will not necessarily be benign. Ther are no free lunches where energy is concerned. In the beginning and in the last ananlysis there is nothing but energy. Energy is everything and our universe is built upon it just as is our planet and the atmosphere which is our home. We mess with its energy balance at our peril.

The last problem of wind energy is that it has diverted a lot of engineering and political energy away from the vital issues of continuity of supply which are quite separate from “green” issues. The time scales for developing meaningful generators are from five to fifteen years and we need to take decisions now to ensure the lights do not go out before then.

The wind that once seemed to promise energy riches is clearly fraught with difficulties.

Colin Walker

Return to Energy