Tuesday, August 9, 2011

Do the math!

I read the other day a post about how electric cars could be useful at distributed energy storages for a solar-powered economy (another version of this was the idea of Lovins that we could use hydrogen powered cars as distributed power generators - totally ignoring that hydrogen is just a carrier of energy and not a source of primary energy, which is the same for electricity).

Then I found Tom Murphy's excellent blog Do the Math where he explains that if the US would be run on solar and one would use lead batteries to have the necessary storage capacity:
"our national battery occupies a volume of 4.4 billion cubic meters, equivalent to a cube 1.6 km (one mile) on a side. The size in itself is not a problem: we’d naturally break up the battery and distribute it around the country. This battery would demand 5 trillion kg (5 billion tons) of lead."
This is some hundred times the known US reserves and many times the global reserves. Not to speak about the cost. Even with current lead prices only the lead would cost 13 trillion dollars, but obviously the prices would sky-rocket if there was such a demand....Now there is other battery technologies - but they are all more expensive, and there are certainly other ways to store solar energy. Nevertheless, even if I am non mathematician, I do appreciate that people do the math before launching to many bright ideas for solving the energy crunch.

In another post Tom says:
"No matter what the technology, a sustained 2.3% energy growth rate would require us to produce as much energy as the entire sun within 1400 years. A word of warning: that power plant is going to run a little warm. Thermodynamics require that if we generated sun-comparable power on Earth, the surface of the Earth—being smaller than that of the sun—would have to be hotter than the surface of the sun!"
 Thanks Tom

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