[silentm]

the biggest problem when looking at hydrogen as your fuel of the future is that it's terribly energy inefficient.

i will summarize some points that i found while reading my chemistry book:

at first glance hydrogen can produce a massive amount of energy per mass unit 120 MJ/kg that's really impressive and about 3 or 4 times better than petrol. but when we are talking about fuel in a car we have to look at how much energy it can produce per unit of volume and here hydrogen puts out a measily 2.8 GJ/m³ (that's 1000 litres) at 35 MPa in its gaseous state. (i don't have the exact number for petrol here as it's not written in the text, but when i look at the graph i have it's about 1/10th of petrol)

when hydrogen is a liquid things look a bit better, where we have about 8.5 GJ/m³ but that means cooling the hydrogen to 20 K (that's -423 °F and -253 °C) which takes in itself a huge amount of energy.

all numbers are taken from Housecroft and Sharpe, Inorganic Chemistry 2nd Edition (german version)

now the biggest problem probably is obtaining the hydrogen... the easiest way to obtain it is splitting water into Oxygen and Hydrogen. sounds good eh? but then you have to realize that this process needs energy too and in the end we are just recombining the 2 elements to form water again.

so the energy we invested in the first place will be produced again when burning the hydrogen so we end up neither gaining nor loosing energy. which is not very efficient right?

so in the end i think i will have to quote what nthfinity said once on this board (sorry i don't know the exact wording but it went something like this) "the future of transportation is not the car it will be something completely and radically new."