I read the Hot Hardware article thinking something was left out, but nope. Seems the research focuses solely on boiling the potato to produce a better electrolyte. This is definitely grade school stuff, the potato is not the energy source, and a magnesium-copper reaction would be better, but zinc is easier to obtain. Notice how many potato "cells" are used for the LED, which is about all you could power with such a minuscule amperage. I'm guessing an output of maybe 5 milliwatts?