Original URL: http://www.theregister.co.uk/2012/09/11/latest_jacobson_windpower_stuff/

Profs: Massive use of wind turbines won't destroy the environment

Would destroy the economy, though

By Lewis Page

Posted in Science, 11th September 2012 11:17 GMT

Opinion Windy professors in the States have produced research in which they say that massive use of wind power would not, as had been thought, damage the planet's atmosphere and cause undesirable climate changes. They also argue that it would be "practical" to obtain half the energy required by the human race using wind turbines.

Professors Mark Jacobson of Stanford and Cristina Archer of Delaware undertook their latest effort with the aim of rebutting research which came out last year (pdf) by German and American scientists, which said that the potential of global wind power is much less than wind-loving academics have previously assessed. That paper also, and perhaps more controversially, used atmospheric modelling to show that extraction of massive amounts of energy from the atmosphere by huge numbers of wind turbines (as would be required if the human race were to be powered to any large degree by renewables) would have similar negative climate consequences to doubling atmospheric CO2.

Jacobson and Archer set out to disprove this, and they say they have done so in a new paper to be published this week in the Proceedings of the National Academy of Sciences.

"Wind power is very safe from the climate point of view," says Professor Archer.

The new paper contends that maximum power output of 80 terawatts could be safely obtained by covering all the Earth's land masses and ocean near them with wind turbines 100m high, spread out individually. However the two profs seem to accept that this is perhaps a little bit ambitious, and move on to discuss "fixed wind power potential for more practical applications".

In this scenario, Jacobson and Archer suggest that 4 million wind towers, spread "worldwide in windy locations" to avoid harming the atmosphere, could safely produce a steady output of 7.5 terawatts, "more than enough to power half the world's power demand in 2030". This should be quite safe for the planet:

While wind power does alter the atmosphere when extracted at massive scales – decreasing wind speed at hub height and to a lesser extent at the surface, reducing the amount of water vapor and cooling the planet – the impacts are negligible at more practical scales of extraction, such as 7.5 TW.

We here on the Reg energy desk will have to leave Jacobson and Archer to battle it out with the German/American team at the Max Planck Institute regarding the matter of atmospheric damage from wind turbines vis-a-vis carbon emissions, and the actual amount of energy that there is to be had: we haven't got the intellectual ticket to get on the atmosphere-modelling bus.

But we do at least know what a Watt is - so let's take it as read that 4 million wind towers can produce 7.5 terawatts without messing up the weather. Is that actually enough to provide half of humanity's power?

Well, 7.5 terawatts is the same as 237 exajoules each year. Total world energy supply at the moment is 490 exajoules annually right now, so it would seem that Jacobson and Archer have cocked their sums up right out of the gate. Even if they're right, wind can only do 48 per cent of the job.

But given the past history of the two profs - of which, more below - it seems safe to say that they are actually assuming that humanity will be using a good deal less power by the year 2030. The Intergovernmental Panel on Climate Change, for instance, believes that humanity must and will slash global consumption down to 390-odd exajoules per year by mid-century.

The trouble with that scenario is that it starts from a situation today where the great bulk of the world's population is miserably poor and therefore using hardly any energy at all, which hardly seems fair - and the population is set to get bigger, too. If today's seven billion people each used only two-thirds of what a present-day European does we'd need supplies of 770 exajoules, not 390. In a more realistic scenario where the human population continues to climb, energy demand in the industrialised nations continues to rise instead of falling enormously and (hopefully) the world's poor start to get a taste of the good life, supplies in the zettajoule (1000 exajoule) range will be required within decades.

So, assuming Archer and Jacobson's figures are correct, wind power can't provide even a quarter of the power the human race might reasonably ask for. The two profs know all this background: the fact is that they don't believe people should be allowed even as much energy as two-thirds of the energy a modern European uses - far less the significantly larger amounts of juice consumed by today's Americans. It's something to bear in mind.

One also notes that wind towers yield about 25 per cent of their maximum rated power capacity over time, meaning that Jacobson and Archer must be talking about towers in the 8-megawatt capacity range if just 4 million of them are to yield 7.5 terawatts over time. No such towers are in service yet, so it might seem rather bold to make assumptions about them, but they are on the drawing boards. Rather optimistically, based on the costs of existing hardware, they might cost say $600k each when land based: which gives us a total cost of perhaps five or six trillion dollars just for the towers. Supporting infrastructure for landbased wind farms (roads etc) generally costs at least as much again on top of tower cost: say $12 trillion to start off with.

Figures so far have been based on landbased farms: offshore ones, which would presumably have to account for many if not most of the professors' proposed future installations (the new 8 MW turbines are intended mainly for offshore use by the wind biz right now) cost hugely more, so much so that the British government is finding that it must offer builders doubled incentive payments under the Renewables Obligation scheme to get offshore farms built, as compared to onshore. (These aren't subsidies from the taxpayer: the British RO scheme works by forcing up electricity prices invisibly and channelling the extra cash to renewables operators.)

Then there's the matter of hooking up the farms to the grid, which generally costs a hefty additional sum - in this scenario a very hefty one indeed as these towers are spread out rather than being clustered in "a few spots", in order to prevent them damaging the climate. This will also push up infrastructure costs hugely as more roads or other transport links must be built.

Don't worry, we can solve the economic problems - literally with hot air

Then, in order to deal with the wind dropping on one continent as it sometimes does we need to be able to pipe in juice from around the world using unprecendented, planet-girdling interconnector power lines (or alternatively we need a vast pumped-storage infrastructure. When wind power reaches these kinds of levels, such relatively minor factors as millions of future electric vehicles plugged in for charging, fridges turning off for a bit etc simply can't help enough.)

It's hard to say what all this would cost as nobody has ever even attempted such things: but we might reasonably think of multiplying our $12tn cost figure a few times at the very least. And given the outrageous amounts of energy-intensive concrete, steel, copper and neodymium that would be required, the idea of doing all this while simultaneously reducing energy demands seems almost comically unrealistic. For instance, US government figures (pdf) suggest that just getting to 50 per cent wind energy (not merely electricity, but the ten-times-greater all-energy requirement) for the USA by 2030 would require something in the region of tripled US consumption of steel, concrete and copper, and multiplication of neodymium supplies many times over. As large amounts of thermal energy are used to make all these things, energy consumption would climb significantly - not fall.

Bearing in mind that the gross domestic product of the entire world is only $69tn (and this would probably contract drastically with the energy scarcity mandated by the IPCC and the two professors - indeed, modern hard-green thinking actually requires the goal of economic growth to be abandoned) we can safely say that 50 per cent energy from wind power is wildly unaffordable, and that the term "practical" isn't being used here in the sense that most people understand the word.

To be fair, however, one should note at this point that Professor Archer has a different plan for coping with windpower's can't-do-baseload problems. Rather than the conventional long-haul interconnectors or pumped storage as favoured by most windpower advocates, she also offers the idea of storing unused wind energy in the form of compressed air for use during calms or demand spikes. Earlier this year she teamed up with a Dr James Mason to look into this. (Dr Mason is not an academic of Archer and Jacobson's standing - both of them hold engineering and atmospheric-science degrees, and both work at respectable universities. Rather Dr Mason is employed at a Heartland-Institute-style nonprofit advocacy organisation called variously "American Solar Action Plan", "Hydrogen Research Institute" etc, and his degrees are in "environmental sociology" and "economic sociology".)

Compressed-air experimental installations are being constructed at present in both the US and Germany, with the idea of using such tech as a means of power storage to help make renewables viable (perhaps reflecting the serious doubts regarding interconnectors, and the undeniably titanic costs and limited capabilities of pumped storage). In power-grid applications, the air would probably be kept in suitable underground geological formations rather than in tanks as seen on the long-hoped-for but disappointing pneumatic cars.

One should bear in mind that compressed-air plants still need to burn fossil fuel (generally natural gas) to prevent the air freezing too much as it expands, which causes unacceptable inefficiencies. In fact a compressed-air storage plant used to back up intermittent wind can be expected to burn a quarter of what a normal gas-turbine plant would when doing the same job, so this is not fully green like interconnectors, pumped storage etc.

But it is potentially far less costly, perhaps requiring a mere doubling of gas prices before it becomes able to compete with straightforward gas turbines in the matter of backing up wind as happens today. Archer and Mason write:

The large-scale introduction of Wind-Compressed Air Energy Storage systems in the U.S. appears to be the prudent long-term choice.

Or if you don't like that idea, perhaps you might go for another of Professor Archer's plans, that of flying mighty windpower kites attached to high-voltage power cables up in the high altitude jet stream (though funnily enough Archer's opponents at the Max-Planck Institute in Germany say (pdf) that that idea's a non-starter as well, both on limited power output and serious damage to the climate. Again, it's hard to say who's right on the atmo-physics.)

There's evidently a good deal of uncertainty regarding the level at which wind power starts to damage the atmosphere the way carbon emissions are thought to. Another paper just out from hefty atmosphere scientists at the Lawrence Livermore lab and the Carnegie Institution says:

We find wind turbines placed on Earth’s surface could extract kinetic energy at a rate of at least 400 TW, whereas high-altitude wind power could extract more than 1,800 TW. At these high rates of extraction, there are pronounced climatic consequences. However, we find that at the level of present global primary power demand (~ 18 TW), uniformly distributed wind turbines are unlikely to substantially affect the Earth’s climate. It is likely that wind power growth will be limited by economic or environmental factors, not global geophysical limits.

"Uniformly distributed", as we've noted above, means "even more unbelievably expensive than you thought". However it would seem that actually harming the planet may not be an issue for windpower up to a point, and if Jacobson et al are right this point is well above any likely human power demand. It also seems quite plausible that a lot of power is there to be had if one is able to cover the entire world in wind turbines and associated roads, power lines etc.

What's not at all plausible, however, is that the necessary infrastructure can be built and made to deliver any reasonably comfortable level of power to the human race at any cost the human race can afford. ®