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By Hamish Johnston
David Keith.
(Courtesy: Eliza Grinnell, Harvard SEAS Communications)
How much energy could be generated worldwide using wind turbines? That’s the sort of back-of-the-envelope calculation that physicists love.
Estimates by scientists had put the generation rate at somewhere between 56 and 400 TW. To put that into perspective, a typical nuclear or fossil-fuel power plant churns out about 1 GW.
However, these calculations don’t tend to consider the impact of huge wind farms on the wind itself. Now, David Keith of Harvard University and Amanda Adams of the University of North Carolina have used a “mesoscale” weather model to do just that.
Their conclusion is that previous estimates of global wind capacity could be as much as 10 times too high.
I suppose this shouldn’t come as a surprise – if you extract vast amounts of energy from wind, you should expect some sort of modification to how the wind blows.
While current turbine deployments are nowhere near the size where we need to worry about how they affect wind and weather, some experts are calling for a future global wind-power total of about 10 TW. According to Keith, once global capacity exceeds a few terawatts, the effects on climate become significant and therefore must be considered in any large-scale deployment plan.
You can read more about the work in this article on our sister website environmentalresearchweb.
One knows that the sun pours about 1kW/m°2 on the Earth. A few parts per thousand of this power go into the atmospheric thermodynamic engine to produce winds. As to the capacity of windmills, there should be no problem so long there is no coupling between the wind-flows running the different windmills. However, as soon the density of these mills becomes significant in an area, this coupling will have to come into play and the overall power production per mill should go down.
Uh oh, “the effects on climate become significant”. So when we’re sitting in the dark trying to do physics by candlelight, we can comfort ourselves with the superb irony that wind turbines not only bankrupt us and freeze old ladies to death, but cause climate change too.
John, this is a problem of physics to be dealt by physical means and not a club of old ladies in distress of season.
Unless we come up with some new turbine designs we will probably run out of special materials before we install 10TW worth. Assuming 10TW is average power then this represents about 30TW of WT capacity, about 3000 times current world installed capacity, I think this is going to take a while to install.
My bet is that solar will be much cheaper than wind in the not to distant future, particulaly in solar rich countries, so I doubt if we will need to consider installing this amount of wind any way.
Quick correction to my previous post.
Pulled 10GW from memory for installed wind power and realised this was a bit low as soon as I hit the ‘post comment’ button, think it may refer to solar. Double checked and figure is about 300GW so we are about 1% towards 30TW, still a few years to go but the materials argument is still valid.
Nick, the PV installed capacity in the world was more than 100GW at the end of 2012 and it is increasing more than 35% par year.
This study errs in its assessment of potential wind energy resources by ignoring real-world data and experience and instead relying on crude theoretical modeling techniques. In reality, wind project developers and investors work closely with atmospheric scientists and other experts to make sure that their projects will produce as much as expected, and real-world data from large-scale wind installations in the US and Europe confirms that they do. Regardless of who is correct, the inescapable fact is that America’s developable wind energy resources are many times greater than our country’s energy needs.
http://www.awea.org/blog/index.cfm?customel_dataPageID_1699=21714
Michael Goggin,
American Wind Energy Association
Michael, the possible mutual negative effect of the density of the windmills in a certain area is obvious and valuable to look into and patrticularly, as you are an element of the AWEA.