Can’t you just break down water, use the hydrogen to power the electric motor, and I don’t think O2 as a byproduct is bad, now this is of course an ideal condition, but why hasn’t this been looked into more?
I’m not a chemist/physicist, but if I had to guess it’s because it takes more energy to break apart the water into Hydrogen than what you will get by burning the Hydrogen to power the motor.
Your guess is accurate.
The other side of the issue is that “water” is rarely only water. There are tons of other shit floating in the water that cause problems with the splitting process, so you usually have to clean the water first which takes even more energy/resources.
Correct. Splitting hydrogen from water is quite energy intensive. Burning hydrogen into oxygen to make water releases energy, but not as much energy as it takes to split the hydrogen off in the first place. The reason to use hydrogen fuel cells is that the extra energy needed to generate the hydrogen is still far better than the carbon output and costly materials needed for making and charging a battery. Batteries need rare earth metals, and they lose their charging ability over time. Splitting water into hydrogen creates “potential energy” from the later creation of water again, making it a useful, clean way to store electricity.
Same as the plans for using cranes stacking concrete bricks to store electricity. It takes more electric to stack them than is produced by unstacking them. But it’s a clean way to store potential energy, and far more efficient and sustainable than a battery.
The reason to use hydrogen fuel cells is that the extra energy needed to generate the hydrogen is still far better than the carbon output and costly materials needed for making and charging a battery.
This is just absolutely a false statement. Hydrogen is a carbon fuel, because all of it for practical purposes comes from natural gas. Although it is possible to get hydrogen through electrical hydrolysis, this simply is not where hydrogen as a fuel source comes from today.
If you see or hear hydrogen being discussed, translate the word hydrogen to mean ‘natural gas’ or fossil fuels, because that’s what you are actually talking about. We do not currently get hydrogen as a fuel by splitting. We currently get hydrogen as a fuel by splitting hydrogen from natural gas. You would likely be better off just driving a gas car than a hydrogen powered if your goal is overall emissions reductions. Batteries represent an actual renewable technology because right now (not hypothetically) we can and do power the electrical networks that charge them with renewables. In as far as renewable hydrogen is concerned, there basically is none, because it costs so much more so to produce in this manner than it does to get hydrogen from fossil fuels.
Correct. Green hydrogen is expensive and energy intensive, and is not as cost effective as getting it from natural gas. So currently most hydrogen comes from natural gas.
But, unless we find ways to make batteries without rare earth metals, we will be better suited to moving towards fuel cell, once we have the excess electricity from renewables needed to split hydrogen from water. For now, batteries are the better option.
As a lot of people have already said, breaking water down into hydrogen and O2 requires more energy than that produced by running a car on hydrogen.
Luckily, there’s some promising research underway, on solar panels that converts water vapour in the air into hydrogen. Last I read, they’re approaching kilowatt scale, but it takes a big system to produce just 500 grams of hydrogen in a day. Which will only produce around 2kW of output power.
Assuming they can somehow make all of that much smaller, and produce much, much more hydrogen from that smaller system, there’s the secondary problem of storing and pressurizing the hydrogen produced, for use in a vehicle. That will take more energy again.
“Hydrogen powered” generally means burning hydrogen in oxygen to make water: 2(HH) + OO -> 2(HHO). To run a car on water as you say is a lot like trying to make a fire out of ash, rather than wood. You can’t burn the ash because it has already been burned.
Technically speaking, no one outside of college demonstration engines are burning hydrogen. Almost all hydrogen powered EVs use fuel cell stacks that mediate the proton exchange through an electrolyte. This allows the capture of far more energy than could be possible by just letting the hydrogen burn, as in a internal combustion engine, for example.
Technically speaking, no one outside of college demonstration engines are burning hydrogen
Toyota has made various working prototype hydrogen combustion engines, so it’s not impossible these could end up in production in the nearish future (they’ve done a hydrogen version of at least the GR Yaris/Corolla engine, a V6, and a V8).
They specifically said they were R&D units and never intended any to go to production. Sometimes they do that to gather data. Hydrogen combustion simply isn’t efficient enough for a production vehicle. You’ll be surprised by the amount of crazy tests car manufacturers do. This includes methanol/ethanol cars, natural gas ICE engines, solar panels, all sort of crazy experimental batteries.
Where does the energy to break down the water in the car come from?
Iirc the energy required to break down water into hydrogen and oxygen is greater than what burning the mixture produces, but in theory solar power might be a viable option to a certain extent.
Efficiency/viability would probably be nonexistent without some sort of miracle catalyst for the breakdown process.
Kinda like internal combustion, you can probably use a battery or something to start it and then use part of the energy from the motor to further continue the process, but yeah lol this seems wishful thinking🤷🏼♂️
That would be a perpetual motion machine, and violate the first law of thermodynamics.
The amount of energy you get by burning hydrogen (creating water) is exactly the same as you spent to split water into hydrogen and oxygen.
No it’s not. They’re referring to exactly what a car or fusion does. To “break even”( in fusion terms), you must produce more energy than is being put in to maintain it. In a car, you turn some of that combustion power back into electrical power via the alternator and recharge the battery that you used to start the car.
They’re just asking if the same principle can apply: using a quick burst of auxillary power to get it going that you then recoup from the excess power created by the hydrogen combustion. And keep in mind, you ARE creating excess power. It’s what moves the vehicle lol.
Water is the exhaust product. Once you have water, the potential energy in the original chemical mix has already been released.
H2 + O --> H2O + energy (in the form of heat or electric potential)
To break down water you have to reverse the reaction and put that energy back in. That’s how electrolysis works:
H2O + energy (in the form of electric potential) --> H2 + O
And since no thermodynamic process is 100% efficient, you will lose some of the energy each time you go back and forth between these reactions.
Out of curiosity, would you end up with the same resultant amount of water before and after hydrolysis? I’m aware some energy would be lost, but would hydrolysis actually decrease the amount of water? (sorry if this a dumb question, but I haven’t actually seen it explicitly answered before)
Mass is conserved. If you split water into hydrogen and oxygen, then combine them back into water, you will have the same amount of water as when you started.
That’s assuming you don’t have leaky equipment in your lab, of course.
