Helen asks…
How does a hydrogen powered car work and still conserve energy?
The Hydrogen first needs to be separated from the oxgen in water, and this, due to the ‘conservation of energy‘ should take up at least as much energy as is produced by the engine… does this mean that H2 cars aren’t as green as they’re made out to be?
adminsta answers:
First, the answer to the question as asked – If you make the hydrogen from natural gas (~97% methane), it is not extraordinarily clean or efficient. The only benefit from this is that it concentrates the “mess” in one place where, at least theoretically, it’s easier to capture/contain/control. I’ve never met anyone that would tell you that this is how to realize the benefits of a hydrogen economy. The ideal scenario is one others here have described… You need to use renewable and clean energy not only to electrolyze the water, but also to compress the hydrogen to usuable vehicle pressures. Then you put it in a PEM fuel cell which generates electricity and water, and the cycle continues. If the energy you’re using is renewable and clean, then the efficiencies involved are less of an issue. This is done currently only on small scales for economic reasons, but is certainly possible.
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Issues brought up by others…
Most H2 powered vehicles today run on compressed gas, but other options are out there. The driving range of vehicles varies enormously, largely dependent on the amount of space the manufacturer has been able to manage for the tank (sometimes at the expense of a trunk in a prototype). Several are in the 200-300 mile range, and tank pressures are being doubled in the next generation (2x far for the same size tank). The hydrogen does not all leak out of the tank.
Hydrogen is quite small and leaks easily, but can be contained and used safely with proper design. Gasoline has at least as many “dangerous” traits, including pooling under a vehicle and being toxic, neither of which is true of hydrogen. Hydrogen is non-toxic. It is also very light and diffuses away from a leak source quickly, making accumulation unlikely. There is an incredible amount of work going into using hydrogen safely in cars – it’s been used safely in industry for years. The key, as with any fuel, is to know it’s properties and treat it with respect.
H2 can be used in an internal combustion engine (with a small amount of emissions), or a fuel cell (“zero emission”). There is still work to be done for sure, but it’s not as bad as it’s being made out to be!
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