Friday, 10 February 2012

Big, still air

I don't know if you watched yesterday evening's Tonight programme on ITV, entitled The Cost of Going Green (the programme is available in itv's ITV Player - it was originally transmitted at 19:30 on ITV1). I did, and was somewhat disappointed with regard to the lack of depth in the subject matter being broadcast. Indeed, the situation we face in Scotland was ignored completely; Eigg was showcased as a fine example of community renewable energy schemes - and that was about it for Scottish specific content. Eigg isn't really representative of the industrialisation issues we face in some areas around here - Eigg's renewable energy scheme is really about providing islanders with their own power, which to my way of thinking makes a lot of sense.

However, there were one or two interesting pieces of information to come out of the broadcast. I will focus on just one. Renewables UK's Maria McCaffery stated (start at time index 9:18 for the full effect and context): ......"what we need to do to smooth out these peaks and troughs is actually to deploy more wind because we always have wind resource in the UK, somewhere....."

Hmm. OK, lets kick this one into touch straight away. First of all, have you ever heard of an Azores high? No, its not what you may be thinking. It refers to a permanent climatic feature that is located over the Azores in the Atlantic. It is a high pressure system that quite often extends (or ridges) north east over the UK. If this happens, because of the size of the permanent high pressure system itself, it tends to lead to a long period of stable, warm, windless weather. Eventually, other low pressure systems degrade this ridge and a more variable climate is re-established. Now, Azores high pressure systems tend only to affect the UK in the summer months, but we do experience high pressure systems in the winter, and to give you an idea of the size of some of these systems, here is a snapshot of a high pressure system the met' office thinks will establish itself right over the UK in the next 48 hours:


Note the lack of isobars (grey lines) over the UK (and Europe for that matter); this means there will be little or no wind. What is shown above is actually the result of two high pressure systems colliding, one from the south west, the other from the north east (rather than the aforementioned Azores high). However, the effect is the same - little or no wind. Now, I have to admit this is a surface pressure chart, but sometimes this lack of wind can extend well above 1,000 feet. Low pressure systems can also cause a lack of wind - wind after all is only created by air moving from a high pressure system to a low pressure system (ie, when there is a pressure differential), so if a big enough system (high or low) develops over the UK, we get no wind until other systems around us start to erode and break down the stable system over the UK.

The Azores high I mentioned earlier extend from the Azores (off the west coast of Africa), right across Europe and the UK - they are truly huge systems. As a result, the ridge that sometime extends across the UK tends to take sometime to break down (hence the long period of stable, still weather). Finally, we should not forget that Stuart Young quite recently demonstrated just how often we have no wind in the UK (Analysis of UK wind Power Generation, Stuart Young Consulting March 2011); to suggest that the wind is always blowing somewhere in the UK demonstrates an ignorance of monstrous proportions; it is a generalisation that has no basis in fact. And, it is certainly not a safe assumption to make when you are talking about having enough wind to drive umpteen Gigawatts of wind turbine output, and when that output forms such a significant part of the energy mix for the whole of Scotland. I am disappointed in some ways that this quote was included - it is 'factually incorrect' and grossly misleading but then again, I suppose I have come to expect such things from Renewables UK and when wind farms are reported by the mainstream madia. Ho hum.