I recently recorded a YouTube video on the notion of hydrogen fuel cell cars (it will be posted soon, and I will add the link when it’s up). One question I did not get into in the video, but which is an interesting thought experiment, is hydrogen – plug-in battery hybrid vehicles. I can find just one model coming online in Australia, the Hyundai N Vision 74. This approach could, theoretically, save hydrogen from losing the the competition to replace internal combustion engine cars. I still don’t think so, but it’s an interesting idea.

First let me state why I think battery electric vehicles (BEVs) are winning and will win this competition. BEV technology is already past the point where there is enough range for most users. While upfront costs are still higher than ICE vehicles, lifetime costs are lower. For those who own their own parking space, which will be the early adopters, there is an extreme convenience to charging at home. And – this is critical – battery technology is still improving, and quickly. There are already production batteries using silicone as the anode in lithium ion batteries with twice the energy density as existing BEV batteries (for now used in aircraft). They will likely go into production ground vehicles in a few years, and this same tech will likely double energy density again by the 2030s. BEVs have other advantages. They can be used for regenerative braking. There is already a reasonable infrastructure for recharging, and this is being built out fast. And, they are among the most efficient vehicles. The round-trip energy storage efficiency is >90%, and they are about twice as efficient in translating energy to the wheels as ICE vehicles.

The negatives for BEVs is the recharging time. Fast charging can take 15-20 minutes, although the newer batteries coming out in a few years claim 0-80% recharge in 10 minutes. In practice, I have not personally found this to be a problem. The only time I fast charge on the road is on long trips, and even a 15 or 20 minute recharge is basically a rest stop. Go to the bathroom, get some snacks or drinks for the ride, and your done. It does take a little planning, but software can do most of this for you. But sure, faster charging would be nice. The real negative for BEVs, in my opinion, is the raw material necessary to make them: lithium, cobalt, nickel, manganese and graphite (although the graphite will be replaced by silicone which is more abundant). Again, research is working on replacing the cobalt and nickel with more abundant elements, but for now this is a potential choke point.

What about hydrogen fuel cells? These exist and the technology works. Hydrogen cars with ranges in the 300 mile range are in production. The big advantage to hydrogen is that they can be refueled in five minutes, essentially similar to gassing up an ICE vehicle. But hydrogen has many downsides, which I think make it a distant second choice behind BEVs for everyday use. The big one is that we don’t currently have a robust hydrogen infrastructure, and many technologists will argue that infrastructure is everything. That is probably why ICE vehicles beat out BEVs a century ago. Building out a system to produce and distribute hydrogen will be a massive project taking years. Also, hydrogen has efficiencies of only about 25-35%, less than half BEVs. That’s a lot of wasted energy, and if we are thinking of putting billions of such cars on the road, that kind of calculation is necessary. Also, there is no regenerative braking with hydrogen. Further, both hydrogen production and fuel cells require platinum and iridium to separate out the ions. These are rare elements, and there is simply not enough for a hydrogen fleet. Again, there is research looking to replace them with more abundant elements, but this is an unknown.

But the big negative is hydrogen itself. Right now 96% of hydrogen is black, brown, or gray – meaning that it is made with fossil fuel. Some is blue, which just means it uses carbon capture, but only about 1%. And blue hydrogen is only a little better than gray hydrogen, which means it is still bad in terms of carbon footprint. In fact, in most cases you are better off just burning natural gas for energy than using it to make hydrogen. Less than 1% is currently green – using electrolysis with clean energy, like wind or solar. This is a huge problem. It will be years, even decades, before a green hydrogen infrastructure exists. And there is a huge demand for hydrogen in industry, so arguably that green hydrogen should be used first to replace dirtier hydrogen necessary for industry, before using extra for cars. To me, this is a deal-killer for hydrogen for now. Until we are making massive amounts of green hydrogen, hydrogen fuel cell cars are bad for the environment. Further, by the time we do have lots of green hydrogen, battery technology will be significantly better than it is today. Hydrogen is simply behind the curve.

Which brings us to the idea of hydrogen battery hybrids. Eventually, once we have the green hydrogen thing worked out, this could be a good idea. Such vehicles could either work in series or parallel. In series means the battery always drives the wheels, and the hydrogen fuel cell is used to exclusively charge the battery. This simplifies the electronics and the whole system. In parallel means that either the fuel cell or the battery can drive the wheels.

Either way, there can be significant advantages to this system. First, you get all the advantages of a BEV listed above. If you had a battery with a 100 mile range, for example, this would cover most daily commuting for most people. You would probably drive 90% or more of your miles just on the battery, charged up at home (from those solar panels you have on the roof). But you also have enough hydrogen for 200 miles of additional range. You would rarely have to dip into this hydrogen, but it’s there when you need it. Also, on long trips you get the rapid refill advantage, perhaps even charging the smaller battery a bit as well.

The main advantage to a hybrid car from an infrastructure point of view is that it significantly reduces the need for all the necessary raw materials. If battery production for cars was reduced to one third what all BEV vehicles would need, that would greatly reduce the strain on the supply chain of raw material. Likewise, much less hydrogen would be required, as it is only used as a backup for long distance. Having a one-technology solution is always challenging, because it tends to strain infrastructure, so having a hybrid solution can be the answer.

Also, it should be noted that for longer range vehicles needed to routinely drive long distances, hydrogen gains in advantage over batteries. This is primarily because longer range means bigger batteries, which is more weight that has to be dragged around. So hydrogen, by itself or hybrids, may have a roll in long haul trucking, for example. This would also reduce the infrastructure needed to trucking routes. Trains are another possibility.

None of this solves the problem of dirty hydrogen. I suspect, and I hope, in fact, that hydrogen fuel cell vehicles remain a small fringe for now. Develop the technology, but widespread adoption before we have a green hydrogen infrastructure would be a colossal mistake. But in 20-30 years, if and when we do have green hydrogen (or if we discover massive hydrogen stores underground) then I think hydrogen-battery hybrids may be the way to go. But also by then batteries may be so cheap and powerful that hydrogen just can’t compete. We’ll see.