Fuel for Thought

Does hydrogen have a viable future in passenger cars?

Diesel car eco ev hydrogen

Hydrogen fuel cell power is being pushed hard by a number of global car manufacturers, with one of the main headline attractions being that the emissions are essentially just H2O, oxygen as a useful by-product of the overall process, and nothing else… well, apart from brake dust and tyre wear emissions, subjects for which I think I will leave alone just now, as they are almost unavoidable for anything that rolls along on wheels. 

I am more and more questioning the reasons for the enthusiasm, and the true motives behind manufacturers pushing hydrogen power for passenger car road transport. Looking beneath the surface gloss of clean green hydrogen, the energy efficiency of existing hydrogen powered fuel cell cars is highly questionable. Realistic tests show that travelling 80 miles on one kilogram of hydrogen is possible, with maybe as much as 100 miles using hypermiling measures. The Guinness Book of Records shows a hydrogen powered car record set by the Toyota Mirai (it used to be sold in the UK at around £50k) of 845 miles covered on 5.65 kilograms of hydrogen, or around 150 miles per kilogram of hydrogen gas. But what does that represent in a real world comparison to pure electric power? One kilogram of hydrogen gas takes at the very least 50kWh of electricity to produce. It means the record car, in covering 150 miles on hydrogen, made using 50kWh of electricity, covers three miles for every kiloWatt hour (kWh). This compares with many battery electric vehicles which, driven with a little care, would deliver 200 miles with a little effort. Four miles per kilowatt hour is the typical return for any off the shelf Tesla Model 3, driven at a sensible pace by most drivers, so even a record-setting hydrogen fuel cell car cannot compete with everyday use of pure battery electric transport.

The figures for hydrogen fuel cell power efficiency are the result of the undeniable energy losses involved in the various stages of turning green hydrogen into usable energy. To produce green hydrogen from water, the water must be purified, using significant energy. Over 20% of the energy input is lost in the electrolytic hydrogen production process itself. Compression of the hydrogen gas, and then cooling it to a very low temperature, to make a compact liquid viable for bulk storage and transport, loses another 10%. Finally, over 30% of the energy is lost in the fuel cell itself. At the very best, only around 40% of the total initial energy input is left to drive a hydrogen fuelled car. It’s just not a good enough figure to meet today’s zero carbon challenges when battery electric vehicles, using green zero carbon electricity, offer vastly higher energy efficiencies. 

Hydrogen fuel cell technology may suit certain niche transport and power situations, such as off-road construction machinery, and quite possibly heavy goods vehicles, but it cannot rival simple battery electric power in terms of energy efficiency for everyday personal road travel. There are those who suggest that, if you’re using green hydrogen, made using zero carbon electricity, derived from, wind, solar, or nuclear power, it doesn’t matter if you use more electricity, as it’s not harming the planet by making more carbon dioxide. But it is further heating up the global environment, with the waste heat lost during the manufacturing process, and use in a fuel cell. It’s waste energy that cannot be justified, even if it is green waste energy, and the significant capital cost of building a plant for making green hydrogen, and the added demand on the electricity grid, must not be forgotten when the energy would be better used for charging EV batteries.

So, what is the big deal with heavy backing of hydrogen power for cars all about? Do those backing hydrogen power have some vested interests in distracting us from the problems and challenges of the ongoing conversion to battery electric power? We all need to seriously focus now on making ownership of EVs a practical proposition for everyone, rich and poor, with competitive vehicle pricing, wider availability of charging facilities, and making sure there is plenty of electricity to go round. It’s certainly not a cheaper option to offer hydrogen fuel power as an alternative to battery EV ownership, as it is greedy on electricity demand, and it’s just not as ecologically efficient as pure electric power. The evidence for the defence of hydrogen power gentlemen? Case closed m’lord!

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