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If we can use hydrogen to power electric motors, why can’t we use water to run a car?
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this post was submitted on 14 Feb 2024
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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.
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.
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.
Yep. Just wanted to get it out there because there are active propagandists promoting H2 as it's an extant carbon neutral technology ( I expect Hypx to show up any moment). I'm not arguing against potential but trying to ground the conversation in material reality.
Sodium-ion batteries appear promising. Like, the energy density by weight of the current market offerings is absolutely too low to be useful for vehicles, but there's hope that can be improved in a relatively short timescale. Prices should be pretty good when factories finish tooling up, and most chemistries use no rare earth metals. Current densities seem great for grid storage, which is where hydrogen has the most potential right now (imo).
I still like the idea of hydrogen for some forms of transportation (freight trains, container ships, possibly aircraft if energy density could be increased or aircraft weight decreased somehow) and as a strategic emergency energy reserve. It'd be great to have more grid resilience as the environment continues to decay. I just worry about the energy costs that come with transporting hydrogen for cars and individual transport. Pipelines seem like they'd be challenging, and trucking it around seems a bit wasteful. In-situ generation would be ideal if power and water are available and hydrolysis can be made more efficient and compact, but that's not possible everywhere.
I dunno. I'm glad it's not my job to figure out the actual energy cost of everything, but I'm really hoping grid-scale sodium-ion batteries will become a reality sooner rather than later, and that we'll see sodium-ion batteries in cars within the next 10-15 years.