As a fan of electric cars, I’ve spent much time talking down hydrogen cars. However lately I’ve come to the conclusion that there is a future for hydrogen cars, but that we have going about hydrogen cars the entirely wrong way.
First let me talk about what in my mind is wrong with hydrogen cars, and why that has made me against them for a long time.
The Problem with Hydrogen Cars Today
Detractors of electric vehicles will often claim that the car isn’t clean because that electricity has to come from somewhere and that may be from burning coal.
The problem with that argument is that most countries don’t get electricity from coal alone. In fact most of the growth in power production around the world today is from renewable and natural gas power plants. Both give lower CO2 emissions when powering an electric car than even diesel.
However for hydrogen then problem is significantly worse. Most hydrogen on the market today is made from natural gas reforming. That means a hydrogen car running on hydrogen today will indirectly produce 3x as much CO2 emissions despite only having water come out of the tail pipe.
However if you used electricity in electrolysis of water to produce hydrogen, you are not necessarily much better off. Say you produce your power from natural gas. Large gas turbines are very efficient. You get 60% efficiency. Natural gas also contains less carbon, so this is significantly better than the roughly 25% you get from an internal combustion engine. Transmission lines and losses in the battery is around 10%, but that still leaves an electric car with efficiency of 54%. Still hardly beating today’s ICE cars.
It looks much worse for Hydrogen cars. Under optimal conditions we get 70% efficiency from electrolysis and 60% efficiency in fuel cells, which gives us a total efficiency of 25.2%. That is a highly optimistic number. I am not taking into account losses from compression of hydrogen, transport etc.
Despite all this, perhaps the biggest problem by far is the utter lack of infrastructure. Compare this with electric cars. You can charge at home, and already lots of charging stations have been built up. A charging station can be built essentially anywhere, since all you need is electricity. You don’t have explosive gasses which need to be kept at high pressure.
This creates a catch-22. Nobody would want to buy a hydrogen car if it is an utter pain to refuel. Add the to the fact that potential buyer today know that hydrogen cars presently are not going to reduce CO2 emissions, and you’ve got a terrible bying proposition.
Terrible Fuel for Transport
As a space enthusiasts I know a lot about the discussion of fuel choices in the space industry. Hydrogen in this case is often loved for its theoretical properties, being a very efficient fuel. However the practical aspects make it a terrible fuel. It has to be stored cryogenically, which is fraught with problems. It can make metal brittle and cause accidents. Hydrogen atoms are so small than they leak through metal. Thus long term storage of hydrogen is impractical. That is why people like Elon Musk and Jeff Bezos favors Methane fuel in their engines. You get some of the advantages of hydrogen but with a fuel that is much easier to handle.
On earth today we have plenty of infrastructure for handling natural gas, in the form of LNG tankers and pipelines. We got almost nothing for hydrogen. That is why I’ve often considered a better choice is to combine hydrogen with CO2 to produce methane and transport that instead.
The Positive Way of Looking at Hydrogen Cars
Despite all this negativity I think there is good way of using hydrogen cars. We just have to rethink the whole concept.
Hydrogen and Battery Cars are Siblings
People tend to think about hydrogen cars as closer to fossil fuel cars than battery cars, because you fill up a tank. In reality most Hydrogen cars are not all that different from electric cars.
There is no hydrogen engine. Hydrogen cars use the same kind of electric motors and inverters as battery electric cars. A fuel cell operates in much the same way as a battery. A fuel cell is essentially a battery using gasses to produce electricity as opposed to solids and liquids as in a regular battery.
We think about it has different because you can recharge a battery with electricity from a society. However in principle you could achieved exactly the same with a hydrogen fuel cell car. If water produced from producing electricity in the fuel cell was not emitted but stored, one could use electricity with an electrolysis apparatus to produce hydrogen and oxygen. In essence you could keep the inputs and outputs in a closed loop and recharge the car just like a regular battery electric car.
We don’t do that because adding electrolysis equipment would add a lot to the cost and weight. It is more practical and efficient to have centralized hydrogen production.
So essentially a fuel cell car is like a battery-electric car, where you have put the recharging outside the car.
Market it as an Electric Car
Hydrogen cars today suffer from inferior infrastructure compared to both electric cars and gasoline cars, combined with no clear environmental advantage.
However if we rethink the hydrogen car concept as an electric car with a range extender, then we got something more practical. Hydrogen cars already have regular batteries to provide a buffer. If we make these big enough to support most regular city driving and allow recharging, then we can use a hydrogen car as an electric car most of the time. Owners don’t have to worry about locating some remote hydrogen refueling station.
The point of hydrogen is then to offer superior range. If you travel far and your battery gets flat, you can start utilizing your stored hydrogen to extend that range.
It is why hydrogen fuel cells may make most sense today for larger vehicles that need to go far such as trucks.
Ability to Utilize Renewable Surplus Power Production
The biggest problem with hydrogen cars today is perhaps poor timing. The world is in the middle of a transition to renewable energy, however fossil fuels still dominate.
That means fossil fuel based power plants can adjust its output in response to the shifting output from wind and solar power. At some point in the future however, fluctuations in output from wind and solar will frequently exceed national energy consumption.
In periods with lots of sun and wind, we will thus have excess power production. This needs to be deal with in some way. One way would be to produce hydrogen through electrolysis. This allows us to provide hydrogen at a low price which is environmentally friendly.
One could in principle use batteries to store excess capacity and it makes sense to do that as well. However while battery storage is far more energy efficient than hydrogen storage, it is considerably more expensive. There are alternatives for low cost storage of energy such as pumped hydro or compressed gas.
However the problem with these approaches is that they don’t facilitate energy transportation. Say you build vast tracts of solar cells in the Sahara dessert or geothermal power plants on Iceland. More power will be produced than can be domestically consumed. We need energy transportation of some sort and batteries, pumped hydro or compressed air does not provide that.
We could build high voltage electric transmission lines, but they are costly and don’t scale as well as tanker ships.
Benefits of Hydrogen over Other Electrofuels
To be honest I prefer other so called electrofuels over hydrogen. You make these by reacting hydrogen with CO2 to produce methane, ethanol or even gasoline. Alternatively you could use hydrogen instead of coal to produce metals from ore (in case you want to use metals as fuel).
However I think it is worth talking about the advantages Hydrogen has over other electrofuels. Electrofuels can readily be used in existing internal combustion engines, and use existing infrastructure. That is a big advantage.
However around half the efficiency is lost in an internal combustion engine compared to a fuel cell. That means a lot of these alternative electro fuels will require twice as many solar cells or windmills producing power.
The way around this would be solid oxide fuel cells which can consume almost any light hydrocarbon. However these fuel cells are not as well developed as pure hydrogen fuel cells.
Finally there is an issue of marketing and regulatory concerns where hydrogen has a benefit. Whenever I discuss using biomethane or biodiesel with people I notice that most people don’t grasp why they are “clean” given that combustion of these fuels release CO2. A lot of people still don’t have a good grasp on the difference between CO2 emitted from fossil fuels and biofuels. CO2 tends to be viewed as universally bad. Hydrogen is much easier to sell, because it has an instant appeal when you can say that the exhaust from a hydrogen fuel cell car is just water.
People are used to thinking that burning things, produce something nasty. That there are combustions producing plain water seems almost magical to many people. While such superficialness should not matter, it is still key to win hearts and minds.
Hydrogen also has an easier outlook with respect to regulation. Today a huge amount of fossil fuels is in circulation. Inserting say biogasoline and electrogasoline into the market will be difficult with respect to subsidies, taxation and restrictions. Authorities cannot easily control whether a fuel sold as biodiesel is in fact not just regular fossil diesel.
Hydrogen distribution could be built out to be based on electrolysis or renewable from the beginning.
As I’ve said before I don’t think there is really one solution that fits every problem. We need several technologies to succeed. I think battery powered EVs will dominate, because they are practical, relatively cheap and can cater to the needs of 90% of users.
However those that need long distance travel, fast refuel, long distance trucks, ships and airplanes will need some kind of fuel. Batteries will not cut it.
I think we need to experiment with both different kinds of steam engines, fuel cells and batteries, as well as different kinds of fuels: hydrogen, methanol, ethanol, biodiesel, methane, silane, metals etc.
The fluctuations in power output from renewables can potentially be deal with in a multitude of ways:
- Concentrated solar with molten salt for thermal storage.
- Surplus power stored in Steam Accumulators, e.g. as used by Terrajoule.
- Hydrogen production through electrolysis.
- Batteries. Could be a big utility battery or in individual homes such as the power pack from Tesla. Alternatively car batteries are used. Cars would be plugged in and buy and sell electric power based on prices.
- Compressed air energy storage system.
If one can make an automatic system where cars can plug themselves in automatically and monitor the price of electric power, they can utilize their batteries to buy electricity when it is cheap form the grid. E.g. when the sun is shining and the wind is blowing. Then when there is a shortage of power, and prices go up, the cars could start selling power again. That way a large fleet of electric vehicles can efficiently moderate the fluctuating output from renewable energy sources.
Whether this will work better than using excess power production to produce hydrogen, is hard to predict. We probably need to experiment with both approaches.