Despite the freak gales that battered parts of the country last week, climate experts are warning that many of Britain’s wind farms may soon run out of puff.
According to government figures, 13 of the past 16 months have been calmer than normal – while 2010 was the “stillest” year of the past decade.
Meteorologists believe that changes to the Atlantic jet stream could alter the pattern of winds over the next 40 years and leave much of the nation’s growing army of power-generating turbines becalmed.
The Coalition has drawn up plans to open more wind farms in an effort to meet Britain’s European Union target of providing 15 per cent of its energy from renewable sources by 2020.More than 3,600 turbines are expected to be installed in offshore wind farms over the next nine years.
But statistics suggest that the winds that sweep across the British Isles may be weakening. Last year, wind speeds over the UK averaged 7.8 knots (8.9mph), a fall of 20 per cent on 2008, and well below the mean for this century, which stands at 9.1 knots (10.5mph).
Usually Britain has warm, wet and windy winters, thanks to Caribbean air carried here by the Atlantic jet stream, a fast-flowing current of air.
But the last two winters have featured exceptionally low temperatures and were remarkably still when they should have been the windiest seasons of all, as high pressure diverted the jet stream from its normal position.
Meteorologists have found that the position of the jet stream has been influenced by the lower levels of activity on the Sun. This decline in sun-spot activity is expected to continue for the next 40 years, with potentially serious consequences for the viability of wind farms.
Professor Mike Lockwood, from Reading University, said: “Changes in the jet stream will change the pattern of winds that we get in the UK. That, of course, is a problem for wind power.
“You have to site your wind farms in the right place and if you site your wind farm in the wrong place then that will be a problem.”
Dr David Brayshaw, also from Reading’s Department of Meteorology, added: “If wind speed lowers, we can expect to generate less electricity from turbines – that’s a no-brainer.”
The gales that swept Scotland last week, with gusts of over 80mph, were the worst in the month of May for almost 50 years. The power to almost 30,000 homes was temporarily cut and two people died.
Prof Lockwood said the recent spell of exceptionally dry weather in the south and wet conditions in the northern half of the UK was influenced by the position of the jet stream.
“The jet stream is sitting over the north of England so we are getting very dry weather to the south of the jet stream,” he said.
The Atlantic jet stream brings warm, wet weather to the UK and Europe from the south-west. If it is “blocked” as a result of changes in solar activity, cold air flows across Britain from the east.
One such period of prolonged blocking of the jet stream is thought to have occurred between 1645 and 1715, when Britain experienced a mini ice age, yet also spells of hot, dry summer weather.
Prof Lockwood said solar activity was especially low during this period, adding that current levels of sun-spot activity were continuing to decline. “We reached a high point of solar activity in 1985,” he said.
“Since then, it has been declining. We are now halfway back to the levels seen during the Maunder Minimum. The probability is that that decline will continue for the next 40 years.”
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