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Analysis Harvard University boffins have published an analysis of how much energy the human race could possibly produce from wind power, and we thought we'd have a bit of a play around with their numbers.

Career Harvard enviro-prof Michael McElroy, assisted by Xi Lu and Juha Kiviluoma (now working in Finland) published their paper Global Potential for wind power in the Proceedings of the National Academy of Sciences (free pdf). They say:

This statement has been widely taken to mean that "Wind Farms could supply planet's power", or even "wind power could provide for the entire world's current and future energy needs".

So can it? Bottom line, according to the Harvard trio, how much energy can the planet Earth possibly generate from wind?

Well, McElroy and Co say that if wind farms were be built absolutely everywhere onshore they possibly can be where the turbines can operate at a load factor of 20 per cent or better - that is, over time they produce an average 20 per cent of their maximum rated capacity - you get a grand worldwide total of 690 petawatt-hours every year. At the moment, people don't generally bother building a windfarm unless they think they'll get 30 per cent, but no matter.

Six hundred and ninety PWh is certainly a lot of energy. Five times the present-day human usage, as the profs say, sounds reasonable.

But hold on. There are 6.7 billion people in the world - and counting. The only reason they get by with a measly 140 PWh a year or so is that the majority live incredibly unpleasant lives. Half a billion in sub-Saharan Africa alone have no access to grid electricity at all, for instance. Electricity, roads, rails, industries, homes, laundry, food, water, welfare states, medicine, education, coolness for the hot and warmth for the cold - even the smaller things like IT and aviation - it all needs energy and plenty of it.

Profligate powerhog Americans, indeed, each use a hefty 91 megawatt-hours annually (according to Professor J C MacKay of Cambridge University). Even relatively restrained Europeans burn through 46 MWh/year.

If everyone on Earth aspires one day to live at the sort of level Americans do now, and assuming the world's population stabilises at 7bn, we're looking at global demand of 637 petawatt-hours - almost all of Professor McElroy's best-possible global output for onshore wind. Even a European lifestyle would gobble half the total possible production, leaving a rather uncomfortable margin for mistakes, future progress etc.

However, Prof McElroy then adds in bigger 3.6 megawatt offshore turbines on every bit of sea where they could do load factors of better than 20 per cent. He's not wildly unrealistic, though: he sternly restricts himself to waters less than 200m deep [!] and within 50 miles of the shore. (The most heavily-trafficked seas of all; but pass on.) That bumps the total up to 840 petawatt-hours annually.

Surely we're there now? Provided the world's population doesn't triple, everyone alive could live at European levels of energy consumption just on wind power. Problems solved, assuming we can persuade the Americans to live in apartments more often and get out of their cars now and then.

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