In the wake of Katrina and over last several days I've had to do some modeling work on US energy dependence and how to replace oil dependency.
I can't go into details (duh: I get paid for giving the details), but it's possible. It'll just take three decades to complete (from the time point of signing a national energy bill to the conversion of the last gasoline station to hydrogen). The Skeptical Optimist, who I read regularly, has by far the most sensible post regarding what it will take to make such a conversion: the willingness of consumers to foot the bill, coupled with the political will to reduce US dependence on foreign sources of energy.
Suffice to say: it can and should be done. Not only would it reduce US energy dependence and improve the terms of trade, it would also be an enormous technological advantage that can be translated into significant exports to further reduce the US trade deficit.
But: three decades, 30 years, 120 quarters, 360 months, 1560 weeks. That convers probably two or even three political generations (of actual politicians in office), and I can't think of any US program that has kept its erstwhile eye on the ball for that long a period of time.
The thirty years is the economically optimum model with the least disruption of energy supply and economic dislocation: it can be done in five years, but only with significant disruption and would cost like significantly more than what the US spends on defense right now each year for those five years (damn, I'm going into detail...).
So what do we do: fiddle around for 10 years and then toss money at the problem, or plan it out sensibly and get the job done? Knowing how Washington DC operates, the former is probably the most likely scenario.