So I was looking into how many yak dung pies are required to charge an iPad once, but I couldn’t find how much a dried yak dung pie weighs.

I did get some information like, an efficient yak dung stove can produce heat at a rate of 17198 kJ/kg (of dried yak dung). And that it burns at 400 degrees Celcius, which works out to a Carnot efficiency of about 60% presuming the outside environment is the Qinghai-Tibet Pleateau at 0 degrees Celcius. Okay, a little optimistic, I grant. An iPad battery is rated at 24.8 W-hr, which is like 89.28 kJ of energy, and that means it just takes 9 grams of dried yak dung to do a full charge. Incredible, at first glance.

Then I realized that an iPad doesn’t take much power to run at all. Even more of a killjoy to my nascent yak dung entrepreneurial instincts is HP Labs, which already designed a megawatt datacenter fueled by dung. They say that a single dairy cow produces 125W in recoverable electricity in dung alone (yes, I did the math). That’s not even counting making cows run circles to generate more electricity from kinetic motion. Alas.

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There is something disturbing about electric heating, especially if the electricity used is generated by thermodynamic processes, such as burning coal or natural gas. Lots of heat is sacrificed at the power plant to be able to turn a fraction of the input energy into this superb high-quality electricity that can do mechanical work. Then at the other end, an electric heater just turns it right back into waste heat without doing anything else useful.

But something useful can be done. Instead of straight heating elements, I suggest a server farm. Maybe box it up like an electric heater, sell the CPU cycles back while still getting the same heat out.

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Big bang an exploding white hole, opposite of a black hole? (paper) This sounds interesting and somehow satisfying.

LED light bulbs coming, but incandescents being phased out by mandate in January, 2012? What?! Time to stockpile bulbs. I like my black-body radiation.

Speaking of black-body radiation, suppose I have an enclosed system with a single aperture for light and only light to pass through. Do I now have a system for converting heat to light, and therefore to electricity via bandgaps? Doesn’t that violate some law of thermodynamics?
(Read the article)

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