Energy density measures how much energy you can get out of a given weight of fuel. The higher it is, the more compact the fuel is and the less energy you waste carting it around. The best batteries (lithium thionyl chloride) hold 2.5 Megajoules of energy in every kilogram of fuel, methanol (biofuel) holds 19.7 MJoules/Kg, gasoline holds 43.54 MJoules/Kg, propane holds 49.6 MJoules/Kg. and hydrogen holds a whopping 143 MJoules/Kg. Uranium is in a totally different league with 88,250,000 MJoules/Kg. What does this mean? Batteries have a long way to go before they are efficient for long distance transportation. Hydrogen is the most efficient fuel for long distance transportation. We should get on with hydrogen powered cars.
~ Roedy (born: 1948-02-04 age: 64)