Hey all, lurker here who’s finally decided to make a post
I’ll preface by saying that I’m a longtime lithium ion enthusiast. It’s been fun watching the technology make its way into an increasingly wide variety of applications. Still, I’ve been thinking about an article I read in the New York Times-- I can’t shake the feeling that I may have prematurely dismissed the promise of hydrogen for energy storage.
The article is about a New Jersey based hydrogen evangelist named Mike Strizki. He produces hydrogen on his property using solar power, then uses the compressed hydrogen gas to power all of his equipment.
The thing that gets me isn’t that hydrogen is a perfect fuel source (it tends to be a little explode-y) but that the chemistry is so simple. It doesn’t require rare elements, nor does it degrade over time. And as I understand it, hydrogen fuel cells don’t degrade over time the way chemical batteries do.
The issue of how to safely transport hydrogen is certainly an important one to solve. But, I have to imagine that it is solvable. We can transport other flammable gasses, after all.
Anyway, I thought I could open this up for discussion, as I’m hoping to learn more about the positives and negatives (so to speak) about using hydrogen as an energy source.
Hydrogen is an interesting one. It does many things decently, but none of them particularly well for “widespread use” sort of scenarios, and a lot of what it does decently is better handled by other technologies - or, in some cases, “We already have the other technologies with a built out infrastructure.”
This, right here, is the core of a lot of the issues with hydrogen. The energy density by weight is quite reasonable. The energy density by volume is awful, so you have to compress it to get anything decent in terms of storage density. That compression takes a lot of energy, and you generally have no good way to recover it on the use side of things, so it’s a major hurdle to overcome in terms of round trip efficiency.
The chemistry is simple, it’s entirely possible to manage it decently, and a lot of the issues with it are solved by giving it a path to escape to orbit (it goes “up” at a tremendous rate, so as long as a leak can go up, there’s really not a huge safety risk). It does ignite if you look at it wrong with a flammability range of “Yeah, it’ll burn…” in air, so don’t let it build up.
Not using rare earths is an advantage, though I believe the fuel cells use an awful lot of platinum or some other precious metals. I don’t have a good knowledge of fuel cell tech, though.
Add a carbon, make methane, and stuff it in the NG pipelines?
This is where a lot of the hydrogen people I’ve run into online tend to depart from reality entirely. We have a nearly-global electrical network already deployed. We have a substantial natural gas network deployed to an awful lot of places. And we have… no hydrogen network to speak of. I’ve seen some plans to run hydrogen through NG pipelines, and the claim is that properly adjusted appliances can handle a good amount of H2, but I’m concerned about the joints in the pipe in homes (H2 leaks a lot more readily than CH4), and the fact that you can’t assume every NG burner is well adjusted. That project might be fine for long haul transfer, but the first home that blows up on a H2/NG mix will end the project (even if it’s nothing to do with the mix).
Hauling hydrogen around by truck is a solution, but see compression (or liquification) losses, and it’s a lot more energy intensive than pipelines.
I’ve also seen some proposals to do onsite generation at fueling stations (basically, use storage as a power grid buffer), but it seems pretty well absurd (and the round trip efficiencies show it) to use electricity to generate hydrogen that you then compress, to shove into a car, to make electricity, to turn the wheels - when most people would really rather charge at home anyway.
A lot of the “end user” uses of hydrogen (mostly hydrogen cars) seem to be an effort from the fossil fuel companies to ensure that the future still involves them as much as possible. Selling hydrogen instead of selling oil is fine, as long as they’re still in the loop. Yet, for most people, charging at home (even with fairly slow charging) works fine, and is an awful lot more convenient than having to go fuel up. I personally don’t mind gas stations, but I regularly hear the sentiment that not having to every go to yucky, stinky gas stations again is an amazing part of EV ownership. We’re not going to get rid of gas entirely, but I do expect the stations to be fewer in number in 20-30 years.
If it has a place as pure hydrogen, it’s probably for longer term energy storage - weekly or monthly sort of storage, distributed at substations. It’s likely easier for that sort of leveling than batteries, and you can build up reserves in the summer for winter, but… it’s a hard sell to justify that over just adding a carbon and going to CH4. If you want to impact carbon emissions, going to CH4 is probably the right answer too, because it can be done with recovered carbon from current streams (or, eventually, atmospheric capture, but that’s a separate set of issues).
It may also have a future in shipping, but even quite high carbon taxes don’t really impact shipping much - it’s very, very efficient and runs on “waste gunk.” Yeah, the emissions are high, but in terms of how much is actually moved… eh. Quite efficient, and with newer hulls optimized for lower speeds, that’s likely to continue. It’s pretty far down my list of things to worry about, even though I find the whole “build it all in China while they clone it with your stolen IP” thing pretty distasteful.
But I just don’t see what problems it solves particularly well that don’t have better solutions. You have to start putting a lot of constraints in for hydrogen to pop out as, “Yes, this is clearly the best option.”
Battery tech advanced a ton in the last decade. Even in lead acid. The various carbon additives are new, the carbon foam stuff by Firefly is new (and those apparently behave a lot like lithium, but are fine in the cold), etc.
//EDIT to add: The Firefly stuff is still quite expensive, though. If I had to re-battery my office now, for some reason, I’d still go with flooded lead acid. It works just fine for a fraction the cost of a lithium or carbon foam pack.
That compression takes a lot of energy, and you generally have no good way to recover it on the use side of things, so it’s a major hurdle to overcome in terms of round trip efficiency.
H2 leaks a lot more readily than CH4
Really good points, and yes, I think that these qualities make hydrogen a poor replacement for natural gas. I’m not sure I’d trust my handyman to install a hydrogen stove, for instance .
The energy density problem does seem like a core limitation to widespread use. Liquid hydrogen requires storage at -423F, which, let’s face it, is hard. Thus, liquid hydrogen is pretty much just used in space travel.
But I just don’t see what problems it solves particularly well that don’t have better solutions.
There are a couple of situations I can think of where gaseous H2 seems compelling. First is home-scale energy storage, and second is grid-scale storage to smooth out the production from renewables. Both of these scenarios involve having a lot of storage space available and an abundance of cheap electricity periodically.
My thesis here is that it’s cheaper to store hydrogen on a cost-per-watt basis than it is to maintain a battery bank of equal capacity. This seems like it would be especially true over the long term (after factoring in degradation), but I haven’t actually run the numbers yet. I would accept the possibility that I’m wrong
Gaseous hydrogen also seems to have some potential in aviation, which has a whole different set of tradeoffs. A quick Google tells me that this is a pretty well-studied area so I won’t pretend to be the expert, but it seems to largely come down to storage volume. Since the weight of the tanks increases exponentially with their volume, it makes the most sense for small planes. Large airliners would require significantly better energy density (in other words, liquid hydrogen).
A lot of the “end user” uses of hydrogen (mostly hydrogen cars) seem to be an effort from the fossil fuel companies to ensure that the future still involves them as much as possible. Selling hydrogen instead of selling oil is fine, as long as they’re still in the loop.
This is why I dismissed hydrogen in the first place-- It felt like a solution in search of a problem. A solution that just happened to fit oil companies existing business models a little too well.
I hadn’t thought about the process of turning H2 into CH4, but thanks for bringing it to my attention! Wikipedia calls this the Sabatier reaction and there are all sorts of examples of it occuring at an industrial scale. Germany seems particularly sold on the idea.
I do wonder if it’s feasible to produce methane on a small scale. It appears that there are miniature power-to-gas plants for home use at least in theory, but it looks… complex. And expensive.
As I learn more about this, I can see why H2 is still limited to kooks + a select few PR-forward corporate projects. Solving the storage volume issue is pretty important to widespread adoption. Still, I wonder if there are some applications for gaseous H2 that haven’t been fully explored.
Sorry, I didn’t articulate the problem correctly. It’s not the tank weight, but fuel-to-tank weight ratio. Since larger aircraft have higher fuel demands, this ratio becomes a limiting factor as you scale up. Much of the current research on hydrogen based airliners is around improved tank design. You want to be able to squeeze in as much fuel with as little overhead as possible.
It’s the same problem as battery-powered aircraft-- The first passenger flights to electrify are small, short-hop planes (like seaplanes). Long distance airliners require more energy density.
It’s not even that good for space travel. Yeah, the ISP with LOX is amazing, but the density of even liquid hydrogen just isn’t that good - so you need big, “fluffy” tanks to hold your fuel. It’s a fine upper stage fuel, but for first stages, in the thick atmosphere, I’m fairly certain that kerosene (supercooled if you want) leads to better overall performance. The ISP isn’t as high, but the reduction in tank volume required gets you better actual performance through lower drag.
LH2 is 0.071 g/ml, RP1 is 0.820 g/ml (or a bit higher). LOX is 1.14 g/ml. The density really works against you for LH2 in just about any case - and the density for LH2 is far higher than for pressurized hydrogen. Compressed hydrogen at 700 bar (a mere 10k PSI) is about 0.04 g/ml. So, half of liquified, but… still poor. Gasoline is 0.75 g/ml.
The density just sucks, no matter what you do.
Most of the things that make hydrogen round trip efficiencies remotely not-awful are not the sort of things you’d find in small scale home storage systems. And if you wouldn’t trust a handyman to work on a natural gas system with hydrogen mixed in at around 0.25 psi (typical home line pressure), how does the thought of 5000/10000 psi pure hydrogen strike you? It’s not impossible to do, but it is somewhat challenging, and when you throw in that a hydrogen fire is (for all practical purposes) invisible, eh. I’m all for crazy storage tech, but I’d have to think pretty hard about hydrogen storage, even out at my office.
Grid scale, there’s certainly more potential, because you’ve got things more centralized and larger, but I’m still not sure how the costs really settle in vs something like lead acid batteries. FLA is still remarkably good, and if you keep them cool, mostly on float, and not stratified, the longevity is excellent.
We should do so!
As for hydrogen aviation, the problem is less the tank weight (though that’s certainly a problem) than the tank shape. As you go away from a spherical/cylindrical tank shape, the stresses to handle, say, 10k psi increase massively. Most airplanes hold their fuel at atmospheric pressure (or a hair above in flight) in the wings, with a generally wing-shaped set of tanks. Those won’t handle even a few dozen PSI without blowing the wing out of shape. You could carry liquid hydrogen, but now you need massive insulation or the wing becomes a very non-aerodynamic block of ice that doesn’t fly.
One of the books on either Skunk Works or SR-71 development discusses their attempts to get a hydrogen fueled high speed, long range airplane (the concept that eventually turned into the SR-71) working, and the size and weight and cost just kept spiraling up and up and up. Even with more or less unlimited technical talent (in the 1960s, so no CFD), they decided the idea was too insane to make work. And that’s before you consider the operational aspects of a liquid hydrogen fueling system scattered around the globe.
Don’t get me wrong - I think that surplus energy hydrogen production has a future. Just, as feedstock to either the rare few cases where it might make sense, or almost certainly more likely, as feedstock into synthetic hydrocarbons of various types. Make methane, make Jet A, and you are now directly offsetting carbon emissions without having to engineer radically new systems that involve “Well, if you totally redesign our infrastructure, you could…” sort of problems.
While “90% round trip” is “above 50%,” you’d normally not advertise it as such in a marketing video. So figure 51% round trip efficiency. I can do far better on lead acid, without even considering lithium.
And $27k buys me… oh, 37 SIND 02 2450s, for a total storage capacity of around 140kWh. Even only using 50% of that for regular cycling…