[El Gato]

Hydrogen must be extracted from either a hydrocarbon or water, and more energy is used extracting it than comes from actually using it.

This is really no different than with gasoline, more energy, in the form of crude oil, is used to produce it than you get out of it. But thought about another way, gasoline is just a convienient way to storee and use the energy available from crude oil, which itself cannot be used in any internal combustion engine you'd want in your car. Similary hyrdogen could be a convenient way of storing and using nuclear energy, solar power satellite energy or a number of other forms.

As far as having leftover carbon if hydrocarbon is used as the feed stock, is this not true of crude oil too? Only a small portion of the crude is made into gasoline, diesel or other light fuels, the rest must be disposed of, often by burning as "bunker fuel" in power plants. I'm sure some use could be found for all that carbon, and maybe not just burning it. Fuel cells have the additional advantage of being a non-thermodynamic process, and not subject to the same "rules", so the higher effeciencies are *theoretically* possible.

[No Left Turn]

I'm glad you pointed this out. I never understood the criticism of needing energy to produce the hyrdrogen needed for fuel cells. The amount of energy needed to crack crude oil into gasoline is enormous, as is the overall expense of running aging refineries. What also costs a whole heap, though it's not paid for directly at the pump but is syphoned off by your tax bill, is the hundreds of billions we've spent over the years keeping Mid East shipping lanes open.

[WOSG]

As far as having leftover carbon if hydrocarbon is used as the feed stock, is this not true of crude oil too? Only a small portion of the crude is made into gasoline, diesel or other light fuels, .. misleading comment at best, it really *is* different ... most of the energy in a barrel of crude goes to useful oil grades. but the method used to create hydrogen - methane reformation - takes already processed natural gas and in an expensive and energy inefficient way converts it into hydrogen. This is the LEAST expensive method - hydrolysis etc., costs more.

It is more efficient to take natural gas and use it in an efficient ICE car, than to convert it to hydrogen for a fuel cell car.

Fuel cells have the additional advantage of being a non-thermodynamic process, and not subject to the same "rules", so the higher effeciencies are *theoretically* possible. dont imply that thermodynamics is repealed. The PEM cell efficiencies have limits too, around 50%, based on the voltage gaps and current flow - decent current flow forces lower efficiency.

whatever theoretic efficiencies, the REAL fuel efficiencies of fuel cell cars is not better than the best hybrid technology (~40% engine+ drivetrain efficiency). Car cost differentials FAR OUTWEIGH the minor cost differentials of different fuel efficiencies.