Wednesday, July 2, 2008

Hydrogen vs. Electric Cars

It seems to me the "Hydrogen Economy" has gone a bit quiet and I wonder if that's because people have been doing some sums. Assume you start with 100kWh of wind power and you can either use that to create hydrogen for your hydrogen car or put into a battery for your electric car. Which is more efficient?

This diagram from Ulf Bossel of the Lucerne Fuel Cell Forum (see their reports). Because of the number of processes involved in converting electricity to hydrogen, compressing and transporting it and then converting it back to electricity, the process cannot beat the simplicity of the battery approach, even with significant improvement. That's not to say battery power for cars is without problems (weight, environmental) or that hydrogen doesn't have a big advantage (you can recharge in 5 mins). But to me the sums do not add up, especially when the additional infrastructure cost of getting hydrogen to filling stations is added.

Interestingly, reviewing other blogs comparing hydrogen with electric, many are keen to point out how electric cars are not really green because they are charged using electricity from coal etc. They don't seem to question where the hydrogen comes from though.

Hear a podcast by Ulf given to The Watt here:


Patrick said...

Working for the National Hydrogen Association, I think it's a shame that Ulf Bossel's points are so often one-sided. Here's the other side. There are two issues with battery only cars that Bossel always fails to acknowledge: short range and long refueling. Even with large advances in battery technology, you won't be able to build family sized cars that have a range of 300-400 miles and refuel in a couple minutes. With hydrogen cars you can.

But let's not get too cynical. You can have the best of both worlds with batteries and hydrogen technologies together. There's no need to choose between the two technologies and we shouldn't.

A hydrogen and battery car that uses the battery for the first several miles and then uses hydrogen to cleanly and efficiently extend its range is the best of both worlds. You can use renewable electricity to fuel the whole system.

Phoebe Bright said...

I think 'where there's a will there's a way'. If we decide to go the hydrogen route we will develop technology that will solve the storage problems etc. If we go for batteries we will develop systems for hot swapping batteries or fast charging and as to range, I can't guess. I don't see the point in putting both technologies in a vehicle as both systems are heavy on their own, never mind putting them together. Electric/petrol or hydrogen/petrol hybrids make sense in the short term though.

The point Ulf Bossel left me with, is now can the hydrogen fuel route ever be more efficient than the battery route because of the increased number of steps in the process. Are there new technologies coming along that can do improve on this?

wildlifer said...

MIT recently developed solar technology that can split water into hydrogen and oxygen without using exotic, expensive materials.

If everyone used this technology at home, you wouldn't need centralized production facilities nor a need to transport energy. This would bring the number of processes for using hydrogen down to 3... electrolysis, compression/storage and fuel cell conversion to electricity. With no need for the heavy batteries that lose their capacity over time and require exotic, expensive materials to make.