I think mostly because of the efficiency and density of those fuels for a self propelled vehicle.

The steam engine can be much more efficient than gas internal combustion engines. I've heard that gas internal combustion engines are typically around 28% efficient, while a high tech steam engine is around 48% efficient.

But if we produce hydrogen directly from solar power, and/or windmill power, then there is wiggle room to choose whatever engine is most cost effective. A high tech steam engine might cost $6,000 or more to build while an internal combustion engine of similar power might cost $2,000 to build; as an example. So that's $4,000 difference in cost that can pay for fuel in the less efficient engine.

My guess is that hydrogen will begin flowing in mass production in the near future. So fuel cells will potentially provide even greater efficiency powering electric motors.

The future awaits with interesting technologies.

Fuel Cells are going to rule the roads in the near future. What about aremote African village, which will be happy with a steam car they can fixand use withe the available natural resources.

I love the efficiency of steam engines, but they've already had a run in cars before gas and gas beat them. They have lots of drawbacks. Waiting to build steam pressure, carrying around a 'bomb' pressure vessel, replacing or recovering the water, heavy radiators, etc. Some steam engines are efficient, but others are worse than IC.

But the idea of running a car off of biomass to me is the best part of this equation. Right now, decomposing biomass is still turning to CO2, so we should get some benefit from it. I'd love to see a good car that ran off of lawn-clippings.

I still believe the hydrogen-car thing is a non-starter. As of yet, noone can make hydrogen cheaply and no-one can store it very well because of it's ability to permiate tank materials.

Go steam!

You're forgetting the single biggest driver: energy density. Just because a steam engine is quoted at being 48% efficient means nothing, even if an internal combustion motor is 28% efficient. Steam has no where NEAR the energy density of standard gasoline. This is the #1 reason why steam is not used for these applications.

You can't expect a steam car to roar itself down a New York Highway.Fuel cells are very futuristic. A realistic scenario would be asteam car running on garbage in a remote African/Indian vilage.

Most people in remote African villages can't afford a car period. Burning garbage is smelly, smoky and unhealthy.

Most of the "remote" places in the world try to do things like grow sugarcane or corn and make ethanol for their cheap gas solution. Americans can barely afford fuel cells, so I really doubt developing countries will be able to.

Ethanol costs about 30 cents a litre, Petrol costs about 1.25 USD in India.We never have surplus Ethanol most of it is either drunk or used inIndustries. My idea is to have a small destructive distillation drivensteam engine which can use all types of bio-fuel. It need not be a bigsteam car, a small one which could transport atleast 2 people andmove about 250 kg of cargo.