Hydrogen vs. Battery Electric Cars

The gravimetric energy density of hydrogen itself is great but the volumetric energy density isn't really. If you take 1 kg of a lithium battery this will require a space of about 0,5 liters. If you take 1 kg of hydrogen even under a pressure of 700 bars it will require a space of around 21 liters meaning hydrogen tanks are always huge. And talking about the tank you also have to consider it's weight to make a fair comparison which is pretty high because the tank needs very Heavy duty walls to withstand the 700 bars of pressure. Then the gravimetric energy density of the energy storage system drops down to 330 Wh/kg not even considering the weight of the fuel cell or the small battery that's needed for the power peaks during acceleration. And you even lose this small advantage in energy density because of the low efficiency of the fuel cell.