Hi guys! Saw this article on BMW saying, hydrogen is the next best thing – from electric cars.
Can anyone ova here, explain in a nutshell how hydrogen cars work? How it’s stored? How it’s made / refined heard its (h2o something)?
The safety of it, in case of an accident?
The transportation of the liquid?
Also, can hydrogen cars accelerate as quick as the Tesla’s? 😯
Thanks!
In: Engineering
Almost all (95%) of our current hydrogen production is through a process called steam reforming of natural gas. So we extract methane from the ground, probably using fracking, then we use lots of energy to break the methane apart at special plants. We capture the hydrogen for later use. Unfortunately, hydrogen is a major PITA to store and transport. Ultimately, we likely move the hydrogen to the refuelling station in very strong high pressure tanks mounted on transport trucks which are probably burning diesel. Since hydrogen is so difficult to store and transport efficiently, we cannot deliver significant quantities at a single time. Same issue for the vehicle that uses it. It must be stored under extremely high pressures in special tanks.
But, then if you purchase a hydrogen vehicle and are lucky enough to live somewhere near a very rare hydrogen station you can claim you are a climate conscious green consumer doing your part to prevent climate change. /S
Hydrogen and Oxygen can be combined into water in something called a fuel cell, and this will release energy that we can harness as electricity. It’s essentially still an electric car, but the electricity is generated in a chemical reaction rather than a battery. And the hydrogen is created in a reverse process, starting with Water and splitting it into Hydrogen and Oxygen (the Oxygen can just go freely into the atmosphere since it’s so abundant).
It has two key benefits over electric cars. The first is that there’s no battery weight. A Tesla Model 3 has over 1000 pounds of batteries. That’s about 40% of the weight of a similar sized ICE car.
The second is that you can refill your fuel much faster. You can fill up a hydrogen tank relatively fast compared, in a similar timeframe as filling a gas car.
This might actually be what long haul trucking uses for electrified vehicles because of these benefits.
There’s a great Physics Girl episode on it: https://www.youtube.com/watch?v=hghIckc7nrY
One note, hydrogen in a car is stored as compressed gas, not a liquid. To keep hydrogen a liquid, you have to keep it really cold. And it will boil off continuously from heat leakage through the insulation. This is why rockets that use liquid hydrogen keep topping the tanks off until right at liftoff. The energy density of compressed hydrogen gas is not that good. Gasoline has a lot more energy per volume, so you are going to go farther on a tank of gasoline than a same size tank of hydrogen.
Hydrogen cars typically use a hydrogen fuel cell.
The fuel cell combines hydrogen and oxygen to produce water and releases electricity. This technology has existed on a basic level since the 19th century and was used in the Apollo spacecraft.
The electricity from the fuel cell in turns powers an electric motor and can charge a capacitor bank or battery.
From an ecological perspective this is good because if Hydrogen is primarily made from seawater moving forward (it presently isn’t) the waste product would be the same as what you started with so it would be a closed loop. What we would lose is electricity to split the water molecules into Hydrogen and Oxygen, which would have to be produced somehow. Solar is likely, but Fusion power is of course the holy grail solution for this. Using traditional forms of power generation like coal or oil for this wouldn’t exactly be that helpful.
There’s arguments that all that water vapor being released by cars could also be bad for the environment, but water from a car can very easily be collected and disposed of safely.
Another problems is that fuel cells need rare earth catalysts like platinum, and platinum mining is very bad for the environment. Alternatives are actively being looked for.
An alternative to fuel cells might actually be staring at us in the face. Hydrogen can be used in a piston engine just like gasoline. This has the advantage that we already have very good understanding of piston engine technology and it wouldn’t be much of a leap to design one. They are also made out of cheap and readily available materials like aluminum and iron.
The downside being that hydrogen is far less energy dense than gasoline so you need a lot more of it for the same amount of horsepower. But a counter argument is current hybrid technologies can easily make up for this (adding batteries to the equation again).
This all has the advantage over electric cars that you can carry a tank of fuel that you can fill up in minutes just like a gas car. The downsides being that Hydrogen is way more dangerous than gas and not presently being made in industrial quantities.
Hydrogen is also the fuel of the future. Developing Hydrogen technology will be very important for future space flight and colonization.
As Xelo mentioned, the hydrogen fuel cell is essentially a battery that works by reacting hydrogen with oxygen. It’s a very interesting technology, and theoretically shows promise for the future, but with the current development of straight electric vehicles it’s unlikely to become a practical option for typical vehicles.
Currently, we make the majority of our hydrogen out of natural gas, so it doesn’t really solve the issue of dependence on fossil fuels. It is possible to make it from water through electrolysis, but this is currently very inefficient. You lose roughly 1/3 of the energy you use in the process, so straight electric vehicles are much more efficient on that front. There are companies working on improving this process, so that may change in the future.
Storing and transporting hydrogen is highly complex. It requires cryogenics and/or high pressures to store. It is also not a very dense fuel, so it’s much cheaper to transport the natural gas from which it is made, even without taking the high pressures into account.
In case of an accident, it’s not particularly dangerous. The Hindenburg went up in flames because they painted it with what was essentially thermite. A crashed hydrogen car isn’t likely to explode in a firey mess. But hydrogen is a very effective greenhouse gas, so leaking it into the atmosphere is very bad for global warming.
Being essentially an electric car with a fancy battery that weighs less than normal batteries, performance should be slightly better than electric, all else being equal.
But, even if we solve the inefficiencies, it would be much more expensive to develop the infrastructure for hydrogen cars than for electric, so it’s pretty much a non starter at this point.
Hydrogen and oxygen really want to combine to make water, a chemical reaction. Chemicals also have electric voltages, and if you do the reactions with the right materials around them you can make electricity flow. This is how batteries and fuel cells work. The difference is that batteries are closed up like a pouch. Fuel cells are more like a living thing, you feed fuel in and get waste out. For a hydrogen fuel cell you feed hydrogen and oxygen in and get water out as waste.
The most common way to get hydrogen is to break up methane, which is CH4. This take energy to do, so in a way you are storing energy by separating hydrogen out, and then releasing energy when you react it with oxygen. We can also use electricity to directly split water into hydrogen and oxygen, but this takes more power and so is less common.
If you take some water and put in 100J of energy to split it into hydrogen and oxygen, and then put that into a fuel cell, you will get 25J of electricity back out. This is not very efficient, lithium ion batteries can be around 90% efficient. The advantage of hydrogen is that it is more energy dense. 100J of stored hydrogen is a lot less weight than 100J of charged lithium ion battery. The advantage becomes less when you consider the weight of the high pressure hydrogen tank you need to store it because it is a gas, you need to cool hydrogen to almost absolute zero to make it a liquid.
Short explanation. They take hydrogen and oxygen and put them in 2 separate containers. There’s a wall between them that hydrogen can go through but electrons cannot. So the hydrogen gets pulled to the oxygen to make water but the electrons need to go around the wall and that makes electricity. Water can also be separated with electricity. It’s basically an expensive way to use water as a battery.
Not a direct response but relating to the viability of using hydrogen power for personal automobiles, I will defer to [Engineering Explained’s video on the subject](https://youtu.be/AouW9_jyZck?si=ygtvSFA5kTRj8MvO). Hydrogen is nice an all because no batteries and recharging right? Except to make hydrogen energy-dense enough to actually be viable for traveling any distance, you’re either taking up the entire interior space of the car, or effectively building a bomb under your rear seats.
Edit: yes I know this isn’t a video about the traditional hydrogen vehicles OP is talking about, but IIRC this is the one where he talks about the physics of storing hydrogen, which was my point
Hydrogen power is basically gas power but with extra steps since the hydrogen is obtained from fossil fuel refineries. Getting hydrogen from water is not economically viable and is very energy intensive compared to getting it from fossil fuels.
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