Survival tips if you find yourself in the Middle Ages?

Re:Survival tips if you find yourself in the Middle Ages? by randallsquared on Sunday January 04, 2009 @11:37AM (#419299)

Almost certainly not more efficient, but growing plants can't use oil directly, and since we can supply enormous amounts of external energy by the standards of a crop plant, engineering them to be able to use it more effectively is useful even if the plant itself is less efficient overall.

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Re:Survival tips if you find yourself in the Middle Ages? by nostrademons on Sunday January 04, 2009 @12:32PM (#419325)

Almost any sort of mechanical or chemical process is more efficient than plants. Photosynthesis is only 3% efficient; by the time the energy enters the plant, you've lost 97% of it. Then you figure various biological pathways, and you're down to maybe 1-2% efficiency for the best plants.

This, among other reasons, is why grain ethanol was such a scam.

The worst mechanical processes, by contrast, usually get at least 10-15% efficiency. That's what photovoltaics can do, for example. Gasoline engines have a thermal efficiency of about 30%, diesel about 45%. Granted, you lose energy in the extraction/refining/transportation steps, but it's still an order of magnitude more efficient than photosynthesis.

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Re:Survival tips if you find yourself in the Middle Ages? by randallsquared on Sunday January 04, 2009 @08:34PM (#419822)

I did not know that. Thanks.

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Re:Survival tips if you find yourself in the Middle Ages? by opticksversi on Wednesday January 07, 2009 @08:48PM (#424323)

http://www.life.uiuc.edu/govindjee/whatisit.htm

The primary [photosynthetic] reactions have close to 100% quantum efficiency (i.e., one quantum of light leads to one electron transfer); and under most ideal conditions, the overall energy efficiency can reach 35%. Due to losses at all steps in biochemistry, one has been able to get only about 1 to 2% energy efficiency in most crop plants. Sugarcane is an exception as it can have almost 8% efficiency.

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Re:Survival tips if you find yourself in the Middle Ages? by ntoshev on Sunday January 04, 2009 @12:10PM (#419313)

Not sure if energy is important part of the equation. Protection from diseases and weather doesn't seem to require energy, it's about chemistry and structure.

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