> =A0Scientists are experimenting with cell mitochondria to break down > molecules that in the process releases electrons onto a specially prepare= d > cathode material. > It may, as they state, allow different materials to be used as fuels, but the energy densities of aqueous solutions will be poor compared to any current batteries and far worse than the best ones. They also mention cooking oil - that's potentially far more energy dense - but not much different than existing fuel hydrocarbons. A suitably small Stirling engine burning a traditional longer chain hydrocarbon or Methanol would be capable of giving a fuel cell a very good run for its money for some time yet. Ultimately fuel cells will attain similar effiiciencies. (The Tessera dish Stirlings get 31%+ sun to grid - a micro sized unit is liable to be capable of even better performance from eg fuel to DC. So around 3 or 4 kWh per litre of hydrocarbon fuel. I think not too much for Methanol. Combustion products are "a problem". Direct Hydrogen combustion is less problematic but storage density so far is low compared to hydrocarbon fuels and is liable to remain so for the forseeable future. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .