Question by loudwalker: What would be the c limate effects of a complete conversion to hydrogen powered cars?
I want to know if anyone has modeled this scenario. And please educate me if I have some fundamental misunderstandings about any of this. But less just say that tomorrow, all cars suddenly were converted to hydrogen powered cars emitting nothing but water as exhaust. What would the climatological effects be of introducing all that water into the atmosphere? My gut tells me that there would be fairly significant effects related to weather, water levels, ozone, whatever.

I have asked this question before and been called a left wing, environmentalist cook. I have no political agenda in asking this. I just want a thoughtful answer and some references to facts and data related to this topic.

Best answer:

Answer by Nickel Johann
Hydrogen is not an energy source (primary energy). It is an energy carrier (secondary energy) just like electricity and HAS TO BE PRODUCED.

Fuel cells which can use hydrogen have a higher efficiency than regular reciprocical engines… nevertheless, the conversion from oil or another source to hydrogen is not very efficient and is expensive.

Therefore, you just DISPLACE the energy consumption to other parts of the chain.

I just give you an example: H2 can be easily produced with methane (CH4)… and the efficiency of the conversion is 70%. Then your fuel cell has also 70% efficiency. This means globally you have a 50% efficiency compared to the 40% of the diesel motor.
You also used an expensive and very clean fuel (methane) which you could have burned directly.
What remains of the reaction is pure carbon… which I guess you are also going to burn. Well so on the CO2 balance, there is no difference.

What do you think? Answer below!