Are wind farms & factories the answer to our energy challenges in the UK and particularly in Scotland?
“Wind farms will desecrate the countryside pointlessly.” – James Lovelock
Most of us tend to assume that because national Government has a policy on renewable energy then expert knowledge must be uncontentious. After all we are expected to trust Government and it’s unthinkable that a national energy policy and planning strategy could be based on judgements that are at best sloppy and at worst – wrong.
In his now highly respected book, ‘Sustainable Energy – without the hot air’ (2009, pp 32& 33) – Professor David MacKay (Professor of Physics at Cambridge University & Fellow of the Royal Society) asks:-
“How much [on-shore] wind power could we plausibly generate?”
We know from existing wind farm experience and testing that turbines , running at optimum wind speeds (between 3-5 Metres/second up to 25 M/s – average assumed 6 m/s) produce an output of about 2W/sq m of land used. What’s interesting, according to MacKay, is that it doesn’t matter how big a turbine is – this figure doesn’t increase because bigger turbines have to be be spaced further apart ( 5 x the diameter of the blade cycle) or they take wind from each other. Their benefit is in economies of scale – rather than in producing more power. So we can know that there’s a limit to wind energy production which is dependent on the area of land available.
Bigger turbines are cheaper to build per unit of power output – but if they don’t produce significantly more power per area of land it means that the massive size of today’s turbines, and their serious effects, has more to do with who benefits financially than it is to do with solving our energy crisis. Ultimately the arguments about wind factories, and the havoc they cause in communities, are not about energy supplies – but rather about political power, vested interests and money. Energy or avarice? Who gains and who loses?
So is there enough land?
According to MacKay, when we factor in the density of population (across the UK as a whole – 4000 sq. m per person) we find that wind power could generate 2 W/sq. m x 4000 sq. m/person = 8000 W/person – or in more usual terms, 200 kWh/day per person – but only if we put a wind turbine on every available piece of land throughout the whole of the UK (allowing for the 5 x diameter rule). Even the most ardent of turbine supporters could not imagine such a landscape. MacKay hastens to add that he thinks even his assumptions are generous.
How much power can wind turbines produce?
Even if we covered as much as 10% of the country with wind turbines we end up with a startling output of 20 kWh/day per person – which is “half of the power used by driving an average fossil-fuelled car 50 km per day”!
How extensive will wind factories need to be?
MacKay says that the turbines needed “to provide the UK with 20 kWh/d per person amount to 50 times the entire wind hardware of Denmark ” – who’ve been building them for 30 years – and “double the entire fleet of all the wind turbines in the world”!
Ref: MacKay, David, (2009), Sustainable Energy -without the hot air, UIT Cambridge Ltd,