Friday, April 15, 2011

Burying CO2 or burying heat?

a small part of a very large illustration by Greenpeace
14 April '11: I have become pretty convinced about the benefits of storing heat underground, as long as the geology supports it - no air pockets, gravel etc. As the delta-T is not too great, it will stick around until the following winter, for heat pumps to retrieve.

I have never believed in one of the other underground ideas, that of pumping CO2 underground. Gases in a heavy medium always want to escape. A balloon filled with CO2 above sea level will fall, but put that balloon below the sea and it will pop up as quickly as a submerged beachball. The delta-D of density is enormous, and rock/clay is more than twice the density of water.
  It seems another of the strategies designed to try to enable the public to maintain the present high consumption of power. It's true that power generation will continue to be high, as we move from a gas based heating to more heat pumps - we are going to have to rely a lot more on home generation and renewable sources. But I declare that CO2 burial will not suddenly make emission from coal burning acceptable. Pumping CO2 underground uses a lot of energy and as the geology is very three dimensional (fissures and uneven strata) none of it can be guaranteed. Also, there is increasing statistical evidence that forcible pumping downwards of gas can be associated with increasing risk of earth tremors or worse.
  Greenpeace have published a very authoritative diagram, illustrating some of the hazards of trying to depend on this technology. Click on the illustration, or click here

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