Less wind for the wind farms?

Thursday 06th Jan 2011 by theWeather Club

Britain leads the world in the field of harnessing the wind. It was already the biggest generator of wind energy before the opening of the world's biggest off-shore wind farm off the Kent coast late last year, and the London Array which is over twice the size of the Kent farm is due to begin construction this spring. This level of investment in wind power has always been controversial, but a new report has suggested that if you are to invest in wind energy at all getting an early start could be a very smart move.

Diandong Ren, a research scientist at the University of Texas at Austin in a paper due to appear in the American Institute of Physics Journal of Renewable and Sustainable Energy suggests that rising temperatures will lead to a fall in wind speeds, which of course would make wind farms less obviously attractive. The reason is that the prevailing winds in the atmosphere about 1,000 metres up are maintained by a temperature gradient between the lower latitudes and the polar regions. "The stronger the temperature contrast, the stronger the wind," Ren says. "But as the climate changes and global temperatures rise, the temperature contrast between the lower latitudes and the poles decreases, because polar regions tend to warm up faster." As a result the temperature contrast becomes lower, providing less energy to generate the winds, leading to lower wind speeds.

Even though all this is taking place hundreds of metres above your average wind turbine, Ren believes their efficiency is still intimately connected with what is happening higher up in the atmosphere. "Frictional effects from local topography and landscapes further influence wind speed and direction," he says. "In my study, I assume that these effects are constant - like a constant filter - so wind speed changes in the atmosphere are representative of that in the frictional layer." In other words, if there are lower wind speeds up there, there will be lower wind speeds down here. Ren calculates that a 2-4°C increase in temperatures in Earth's mid to high-latitudes would result in a 4-12% decrease in wind speeds in certain high northern latitudes. This means, Ren says, that with "everything else being the same, we need to invest in more wind turbines to gain the same amount of energy."

Which brings us back to investment. If the study's projections are accurate, wind energy is going to become increasingly expensive. Those countries with an existing wind turbine infrastructure will be much better placed to deal with this than those belatedly deciding that they need one. After all, making wind farms more efficient is far cheaper than building them from scratch. Of course there is the question of do you want wind farms at all, and that is a cost/benefit debate set to run and run.