by Devil » Sat 16 Jul 2005, 09:07:17
$this->bbcode_second_pass_quote('SolarDave', 'I') have a dream - that we will sequester much of the carbon we are pumping out of the ground in "whole house" sized carbon super capacitors.
Dream on. Have you any idea of how much carbon we are pumping into the air each year, from fossil sources? Some 5 gigatonnes = 5 x 10^9 tonnes = 5 x 10^15 g. One supercap uses typically about 5 g of carbon. Therefore, to sequester one year's emissions of carbon, you would need make 10^15 supercaps. This is about 170 supercaps per man, woman and child in the world per year, just to balance the emissions, not to mention the 200 or so gigatonnes that we have already stocked in the air since the start of the industrial revolution. I have a little niggling feeling that your dream couldn't even make a measurable dent in the 750 Gt of carbon in the atmosphere (even if we could find room for it all, if we extracted it).
As the C in the atmosphere is bound up in molecules like CO2 and CH4, there is another wee problem. Where would we find the energy to extract the carbon from them?
Have a look at
http://www.cypenv.org/Files/sequest.htm to get a glimpse of the magnitude of the problem.
Now, let's imagine your dream became reality. These capacitors are electrolytic. By definition, that means they are leaky. They cannot hold their charge indefinitely. This makes them ideal for floating applications where a sudden short-term load needs power. They cannot be used for storing energy in non-floating applications. One of the characteristics of electrolytics is that the leakage current varies between individual components. For this reason, in series constructions, necessary for voltages >2.5 V, a balancing network of resistors of a value such that each one is about 1/10 the resistance of the leak. is necessary. This would have the advantage that the charge in each unit would always be ± identical (otherwise, the energy available would be limited to proportionally that of the most discharged one). However, this chain of resistors would accelerate the discharge, unless they were floating.
Practically, I cannot foresee your notions being very good.
Dream on! 
