We see so many battery electric cars being purchased but very little of hydrogen fuel cell vehicles. What are the reasons?
In: Technology
Engineering hydrogen cells is tricky – to store a decent amount of it, you have to store it at really high pressure, and high-pressure flammable explosive gas is a bit of a safety nightmare.
If you’re designing that, you have to be able to explain why no head-on, rear-end or T-bone collision could possibly rupture your hydrogen storage and start a fire, and that has proven difficult. Even once you had perfect cars, you’d have to develop safe hydrogen tanks and safe fueling station infrastructure and build it nationwide.
We’ve already got electrical-power infrastructure in every home; it’s tough to compete with that.
*Edit: Really fast math tells me that a gallon of gasoline is 33 moles of octane, which releases 181 megajoules of energy when it turns. A mole of hydrogen burns for (being generous and assuming liquid water as the product) 285.8 kilojoules, so it takes 633 moles of hydrogen to match a gallon of gasoline. 633 moles of hydrogen at ambient conditions would be a 15.7m^3 cloud, so a ball about ten feet across. If you want to get that down to the size of a fuel tank, you need a pressure of about 200 atmospheres, or around 3000 pounds per square inch. Quick reminder, this isn’t replacing a tank of gasoline; this is replacing a gallon of gasoline. For flammable gas you probably design that tank for at least 12,000 psi. Now you get to calculate how heavy that tank is, and see what it’s doing to your car’s performance and efficiency, and you’re probably not going to like the answers. :)*
Electricity is everywhere. It’s in your house so you can plug in your car there. It’s also in every single business and street so chargers can be installed basically everywhere. There is a whole network of electricity running around the country that is designed to be easy to tap into.
Hydrogen is nowhere. It would be incredibly expensive and difficult to make a network of hydrogen gas stations for new hydrogen cars. Nobody wants the cars because there is no way to fill them, no one wants to build hydrogen stations because there are no cars.
Hydrogen is a horrible fuel for automobiles. It’s produced by electrolysis, i.e. pumping a ton of electricity into water to separate the oxygen and hydrogen. You end up using a lot more energy to create it than you get from it, and it stores less energy than gasoline, so you can’t drive as far on the same size tank.
Electric Cars are more efficient and thus cheaper to maintain. If you charge a battery with electricity you loose near to nothing in the process. Meanwhile with hydrogen you need to create it first. There a different methods but all use only up to 60 or 80 percent (forgot the exact values) of the energy for the hydrogen which then has to be compressed to some level, aswell as transported to a designated infrastructure that also cost money to maintain.
There’s a distribution network across the world to distribute electricity. This makes it very easy to have recharge stations for EVs. Anywhere there is a power line, you can setup an EV charging station. Electricity is also fairly cheap. The average cost of electricity across the US depending on the source is between 12-25 cents per kWh.
For hydrogen, that distribution network doesn’t exist. The US Department of Energy says there are currently only 59 hydrogen refill stations in the entire US. There are plans for 50 more to be built. Now compare that to 168,000 EV recharging stations. Even if all of those 50 for built, there’s 1400 EV stations for every 1 possible hydrogen recharge station.
Now granted, it is a bit of a chicken and egg situation with the recharging stations for hydrogen fuel cells. There aren’t refill stations because there aren’t a lot of hydrogen fuel cell cars. And there aren’t a lot of hydrogen fuel cell cars because there aren’t a lot of fuel stations.
The final factor though is the price. Even if a distribution network did exist, hydrogen is much more expensive to create, and it is expensive to store. Because of its size, hydrogen will eventually leak out of anything you store it in.
The biggest one is that there fuelling infrastructure is basically nonexistent. Most operators of hydrogen vehicles have to make their own, so it’s mostly limited to industrial plants. The few commercially sold hydrogen cars suffer from this.
The other issue is that the technology just isn’t quite market ready, even after all this time. The fuel cells are still not optimal, and the actual storage of hydrogen in a fuel tank remains genuinely dangerous. Hydrogen loves to leak through solid steel, and makes it brittle on the way out. Plus it’s really explosive.
Lastly, even if both above issues were resolved, green hydrogen (made from electrolysis of water) is actually expensive and not made in large quantities. Most hydrogen is actually made from methane and contributes to CO2 emissions, which makes it less desirable for the purpose of a green transition. And it’s still not made in sufficient quantities to satisfy the consumer market.
The only advantage hydrogen has over BEV is fast refueling time. So for use cases where it’s critical to minimize downtime (eg long distance truck hauling), then it can make sense. Or if weight is a big factor and you can just burn the hydrogen, like in aviation. Otherwise, BEV is just better. You can charge at home, it’s a lot more energy efficient (huge losses to create, distribute and contain hydrogen), the technology is much simpler and cheaper.
The thing about fuel cells is that they have more in common with BEVs (Battery Electric Vehicles) than they do with ICE (Internal Combustion Engines). You might think that hydrogen replaces gasoline, but it’s really much more like the battery.
In an ICE, the gasoline basically explodes, generating mechanical energy that is used to do things (i.e. move the car) and also provide electricity for the 12V battery and the electrical system.
In a BEV the battery stores electricity that powers the electric motor, which is used to move the car.
In a hydrogen fuel cell vehicle, the hydrogen isn’t burned like you might expect. It’s pushed through the fuel cells which basically react it in a way to make electricity, which is used to power an electric motor.
So between BEVs and hydrogen fuel cell vehicles, you’re really just deciding between; how do you want to store your electricity? As hydrogen, or in a battery.
As other people have mentioned, hydrogen has some drawbacks (storage is difficult, it can explode, there’s very infrastructure). Electric has drawbacks too, but a huge factor for the end user is convenience; there’s electricity everywhere, and a lot of people can just charge at home.
Hydrogen is around $35 USD/kg. A full tank on a Toyota Mirai is $180-200 for ~350 miles. That’s in part to supply/demand, and the necessary infrastructure to transport, store, and deliver hydrogen.
Creating hydrogen from clean sources is also inefficient, losing about 30-40% of energy compared to just 5-10% in electricity from the grid. It’s a bit better from natural gas extraction, but cost to capture isn’t quite there with cost to sell.
Ignoring the cost and transport of getting hydrogen to enough locations to fill you car whenever you need. The problem with hydrogen as a fuel is that it’s not dense enough, so you dont have a lot of range.
The other challenge for the density problem is that you need to store as a liquid to have enough, which is at -250°C which is pretty difficult to maintain, then the off gas stores at 5000-10000psi, which again… kinda difficult to maintain as hydrogen is literally smaller than other materials and will leak out of every storage device with enough time.
So to prevent the constant risk of making a pressure vessel bomb from above, hydrogen intentionally leaks out when not in use, so after say 2 weeks of your car sitting in the garage, your fuel tank would be empty…. also your garage would then be full of hydrogen unless theres an opening to let it out so thats not great.
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