My take is that any proposed vehicle power source must first prove itself in base-load or dedicated point applications. So far, we haven't seen H_{2} power show up in laptops and Japan has a small experiment with home co-generation systems but nothing recent to indicate it has been a rousing success.
We do know ordinary batteries and in spite of their energy density limitations, they remain a proven, 'in your hand' technology. We also know how to make efficient heat engines (or fairly close to the maximum efficiency materials allow today.) So I tend to prefer what can be applied versus "a miracle occurs here" technologies.
Fuel cell powered vehicles still depend upon several different sources of "unobtanium:"
- expensive yet vulnerable catalytic electrode materials
- pure hydrogen fuel - to avoid poisoning the electrode material
- hydrogen storage - both vehicle and to distribution stations
- air w/o electrode poisoning gasses
- conventional batteries or ultracapacitors - for peak power
By establishing a base of hybrid-electric vehicles, the natural result will be, over time, a decrease in the size of the thermodynamic engine with higher efficiencies and a stronger electric part. For example, the Prius:
- NHW10 (1997-2001): 43 KW gas, 30 KW electric (41%)
- NHW11 (2001-2003): 52 KW gas, 33 KW electric (39%)
- NHW20 (2004-now ): 57 KW gas, 50 KW electric (46%)
When you check the "Classic" database you'll find one NHW10 at the top of the list, the most efficient. We already know the NHW20 out performs the NHW11. The figure of merit, the percent of electric over total power, seems to follow the vehicle mileage performance. It will be fairly easy to substitute a functioning fuel-cell (if it ever arrives) for the ICE.
As for running the ICE on hydrogen, the storage and efficiency problems remain and they are daunting. Now if the exhaust then runs a topping turbine, it may make a little more sense. But there would be lubrication issues to solve as oil and water are a very bad mix.
Bob Wilson