The efficiency of hydrogen cars versus battery electrics has been debated for a long time in the past decade. However, despite of all that talk, these days Toyota unveiled the first widely-available commercial hydrogen fuel cell vehicle hybrid, the Toyota Mirai.
I have nothing against hydrogen itself or the hydrogen cars currently produced – it’s clean, burning it produces water and it’s the ideal solution for our oil-hungry transportation system. But that’s it, hydrogen is only ideal – when trying to put it in cars, hydrogen causes a lot of trouble, when compared to batteries.
So, we have to take into consideration four aspects:
1. How hydrogen is produced
These are the two mainstream ways that hydrogen is being produced nowadays:
- natural gas reforming
- electrolysis, done with:
- electricity produced by burning coal
- renewable resources such as solar / wind / hydro etc.
2. The compression of hydrogen
In order to be loaded in tanks, hydrogen has to be compressed or liquefied. Current compressors, as good as they are, have their own efficiency leaks.
It’s a rule of thumb that every operation you do when handling energy is made with costs. This rule is true for both electricity, hydrogen and even gasoline. Since you can’t use energy right away, you have to store it and transport it. And that’s where the big trouble really is. You can’t compress or liquefy hydrogen with 100% efficiency – energy is being lost through the energy spent by the very compressors that liquefy hydrogen. It is being put in at compression/liquefaction and lost at decompression. You can experience that first-hand when you use a spray – you feel it getting cold as it decompresses, because decompression sucks heat out of the environment – that’s the trouble even with compressed air energy storage – but that’s another story.
3. How hydrogen is transported
Well, these days they carry oil with diesel-powered trucks, and the same is going to be happening to hydrogen. The theoretically clean-burning, carbon-free energy carrier (for hydrogen is not an energy source, it’s only a carrier) is going to be transported with losses from the production site to the delivery stations. Trucks are going to lose energy, pipes are going to lose energy, accidents can happen with disastrous circumstances.
4. Fuel cells heat up
Hydrogen fuel cells have historically been used in spacecraft since the inception of the space program – they do a good thing, theoretically, but speaking efficiently, they’re hydrogen guzzlers. Besides the fact that hydrogen fuel cells are very, very sensitive to carbon, which can ruin them in time, hydrogen fuel cells produce a lot of heat.
And guess what that heat is? Energy. You use heat to make your home comfortable in winter, and you pay for that heat. Guess what? You pay for the hydrogen wasted through that heat, as the car cools it down. The Toyota Mirai even has two big and (in my opinion) ugly air intakes in the front that ruin both the aesthetics and the aerodynamics of the car. These two inlets are being used to cool down the hydrogen fuel cell stack, which would otherwise melt down.
Now, I’m not saying batteries don’t heat up when used – but not as much as fuel cells, by a large measure.
A hydrogen fuel cell has a 50% energy conversion efficiency. Diesel engines are not far away – the best of them have 35%.
And that’s just in the fuel cell!!
Tony Seba, a Lecturer in Entrepreneurship, Disruption and Clean Energy at Stanford University, a serial Silicon Valley entrepreneur and author of “Clean Disruption of Energy and Transportation”, “Solar Trillions” and “Winners Take All,” put up a graphic that clearly depicts, with solid data, how much less efficient fuel cell car configurations are, compared battery ones.
Here it is, below:
As you can see, a hydrogen car is roughly 19 to 23% efficient, which is way, way lower than a modern diesel engine. I’m not keeping the devil’s side here, I’m against diesels, they’re responsible for maybe more pulmonary diseases than tobacco, but this is not how a so-called “disruptive” technology should behave, even if we get hydrogen for free from solar power.
And imagine how simple Tesla’s supercharger network is, compared to the whole hydrogen distribution chain. Put some solar panels to power the chargers and there you go, free energy for life, from the free solar power we have. And that scenario is already here, people are working to implement it worldwide, as I write this.
Elon Musk clearly stated once that “hydrogen is bull**it.” He even told me in an interview that he’s a great fan of ultracaps and that may mean hydrogen may not even make any sense once that technology matures.
I’ve been a hydrogen advocate for a long time, I’ve seen it in use from those pesky Joe Cell generators to BMW’s direct-burning experiments and the Toyota Mirai.
I’m also not saying Toyota has done a bad job with the Mirai, as a car – they’ll be betting their future on this technology, after all – but what Tony Seba and Elon Musk are saying finally makes sense. We don’t want gasoline version 2.0, we want to run our cars with energy, not fire, and we finally want to do that efficiently. We want our cars to move, not waste heat.
When fuel cell stacks will be 90% efficient and when we’ll be able to produce, compress and store hydrogen much more efficiently, then yes – hydrogen is an option. But by then supercaps and batteries will have evolved and who knows what they may be capable of in, say, 20 years?
I drive a Prius – and while it may not be the most efficient car in the world right now, in 2004 it was built in what was then the right direction. The Toyota Mirai may be electric, after all, but I’m afraid that after a few years people will hack them to put bigger batteries or supercaps and turn them into battery electrics, the only energy storage for cars that makes sense, at least in the foreseeable future.
I just read that Elon Musk explained his point against hydrogen cars, in January, in Detroit.
“Hydrogen is an energy storage mechanism. It is not a source of energy. So you have to get that hydrogen from somewhere. if you get that hydrogen from water, so you’re splitting H20, electrolysis is extremely inefficient as an energy process…. if you say took a solar panel and use the energy from that to just charge a battery pack directly, compared to try to split water, take the hydrogen, dump the oxygen, compress the hydrogen to an extremely high pressure (or liquefy it) and then put it in a car and run a fuel-cell, it is about half the efficiency, it’s terrible. Why would you do that? It makes no sense,” he said.