[ExI] How to tame hurricanes

[Anders Sandberg]

On 2013-12-11 21:25, BillK wrote:
> They concluded that the wind turbines could have sapped Katrina of so
> much energy that wind speeds would have been reduced by up to 50
> percent at landfall and the hurricane's storm surge could have been
> reduced by about 72 percent, Jacobson said. It also would have
> generated 0.45 terawatts of wind power.
> ---------------------
>
>
> It sounds as though he is serious about this proposal.

Looking at his papers, books and courses, he seems to be serious about 
wind power. Unfortunately I think he is overly optimistic. Check out 
Vaclav Smils' data-dense paper
http://www.vaclavsmil.com/wp-content/uploads/docs/smil-articles-science-energy-ethics-civilization.pdf
where he argues wind can *at most* globally provide 10 TW. Not bad, but 
hardly enough.

Similarly the hurricane-stopping power of windfarms seem implausible. A 
hurricane is a massive heat engine involving the coordinated movement of 
millions of cubic kilometres of air: a low-altitude line of higher drag 
does not seem to be able to efficiently dissipate that much energy (how 
efficient are islands in protecting the coast?) Surely they can act as 
local help just like mangrove swamps, but a 50% decrease? Let's see, 50 
m/s winds carry 1250 W/m^2. So you need to dissipate 625 W/m^2. If we 
take a 50 km stretch of coast and try to block winds up to 100 m, I get 
3.125 GW. A typical turbine in the London Array is 3.6 MW, so we need 
868 of them. Spaced along 50 km that is one every 58 meter. Doesn't 
sound totally absurd (unless I calculated wrong somewhere). I get a 
rough cost of £4.6 billion ($7.5 billion).

If the above is right, then I do get worried about the effects of 
increasing drag on the global circulation system.

-- 
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University