Here’s an write up from a Stanford University Professor of Computer science about the various uses and drawbacks for hydrogen as a fuel. Seems not much has changed since he started writing the page in 1996. Has useful data about the power available in hydrogen.

Hydrogen is the lightest of the elements with an atomic weight of 1.0. Liquid hydrogen has a density of 0.07 grams per cubic centimeter, whereas water has a density of 1.0 g/cc and gasoline about 0.75 g/cc. These facts give hydrogen both advantages and disadvantages. The advantage is that it stores approximately 2.6 times the energy per unit mass as gasoline, and the disadvantage is that it needs about 4 times the volume for a given amount of energy. A 15 gallon automobile gasoline tank contains 90 pounds of gasoline. The corresponding hydrogen tank would be 60 gallons, but the hydrogen would weigh only 34 pounds.

In terms of energy contained, 9.5 kg of hydrogen is equivalent to 25kg of gasoline ( Peschka 1987). Storing 25 kg of gasoline requires a tank with a mass of 17 kg, whereas the storage of 9.5 kg of hydrogen requires 55kg, (Peschka 1987). Part of the reason for this difference is that the volume of hydrogen fuel is about 4 times greater for the same energy content of gasoline. Although the hydrogen storage vessel is large, hydrogen burns 1.33 times more efficiently than gasoline in automobiles ( Bockris and Wass 1988). In tests a BMW 745h liquid-hydrogen test vehicle with a 75 kg tank and the energy equivalent of 40 liters of gasoline had a cruising range in traffic of 400 km, or a fuel efficiency of 10 km per liter ( Winter 1986).

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