Hydrogen PEM fuel cell based storage

[Plasm]

Yeah, “next door” was tongue-in-cheek but it’s still very cool.

Have you seen this?

Ah okay, wasn't totally sure ^^

I haven't seen the video till now. He has a cool project, especially the energy recovery on the heat pump is very advanced. Energy recovery of ventilation/heating systems is just getting popular in the last years. His hydrogen storage sounds comparably low pressure, maybe the tanks aren't rated for really high pressure, but the amount of tanks he got already provide a nice amount of power. 1.5 MWh if I calculated correctly from his 40 gallons of gasoline example. I'm kind of jealous of his property. I couldn't fit any of that big tanks and am pretty sure you need a permit in Germany to put one in your yard.

 

[copec]

His hydrogen storage sounds comparably low pressure, maybe the tanks aren't rated for really high pressure, but the amount of tanks he got already provide a nice amount of power. 1.5 MWh if I calculated correctly from his 40 gallons of gasoline example. I'm kind of jealous of his property. I couldn't fit any of that big tanks and am pretty sure you need a permit in Germany to put one in your yard.

We have code here for that stuff too. You could only do that here when there is enough space to isolate it from structures around, and you would still need planning/permission. Or live in some of the remaining remote places in the US that still aren't under the jurisdiction of any building authority.

The actual PV panels are at a price point now that I would compress it into high pressure instead of using 200psi ~14bar of those propane tanks, but I remember reading about this project before the video, built in 2005 or so, and those were probably still $2k a PV Panel, so he probably decided against the complexity and energy loss of the high pressure storage.

I follow this fellow on YT, he does neat stuff:

 

[copec]

I would like to see something with a reversible PEM and storage cylinders using a high-pressure process: https://en.wikipedia.org/wiki/High-pressure_electrolysis

 

[Plasm]

With reversible PEM you mean that you don't have a separate electrolyser and fuel cell? So they are combined in the same thing and you just feed back the hydrogen? That would be a gaseous redox flow I guess. At least I don't see a difference to that.

For hydrogen there could be an efficiency problem if you try that concept. The biggest problem with hydrogen is the efficiency to produce it and convert it back to electricity. So you want that as high as possible. I've seen a new electrolyser concept, where you don't just flood the cell and instead use the capillary effect. Below is the article from last week, where they kinda show the evolution.

The Hydrogen Stream: Novel concept for alkaline capillary-fed electrolysis

Researchers from Australia’s University of Wollongong presented a study for alkaline electrolysis where the liquid electrolyte is continuously drawn up a separator, leading to bubble-free operation at the electrodes. Meanwhile, Korean researchers developed a novel heterostructured catalyst...

www.pv-magazine.com

 

[BiduleOhm]

Just mentionning it since it wasn't so far: H2 is extremely dangerous. It is explosive in pretty much all concentrations (from 4 to 75 % in air) and has a very low activation energy (i.e. even the smallest spark, arc, ... can ignite it). Even worse, it will detonate in most concentrations too (from ~20 to ~60 % in air).

Do not play with H2 if you don't know very well all the associated risks.

And personally I would never store more than a liter or two of H2 anywhere near my house or me.

 

[anonymous]

I believe you need to be in an enclosed space in order for H2 leaks to be a problem. From what I understand, hydrogen gas diffuses away too rapidly in an open environment to be an issue.

From my research, it sounds like chemical hydrogen storage is the only practical way to store hydrogen. There are way too many problems with hydrogen gas based storage.

1. The H2 molecule is too small, so, it leaks through the container walls.
2. Handling gas pressure changes is a nightmare. Also, it adds a lot of inefficiencies.
3. Metal hydride option sounds interesting but it turns out to be too expensive and inefficient.

My money would be on chemical hydrogen storage, such systems based on ammonia, ammonia borane, alane, n-ethylcarbazole, methyl-cyclopentane, etc.

What is needed is a molecule that contains hydrogen in a liquid state at room temperature and pressure that would be easy to produce and easy to disassociate hydrogen from, that would also be safe to handle. I think the best option I am aware of is ammonia, but it does require ~10 bar to be liquid (at room temperature) and is toxic and has a strong odor.

Correct me if I said anything incorrect.

 

[Plasm]

1. The H2 molecule is too small, so, it leaks through the container walls.

AFAIK, leakage through the cylinder wall is not a problem and storing pressurized hydrogen even reduces the leakage. We are looking at time frames of 10 years for negligeble loss. So nothing ground breaking for efficiency losses of the system. I don't know about the seal of the filling point though. But I would guess it's not a big problem either, even if there is a little more leakage.

My concern with chemical storage is the further efficiency loss but mostly the safety concern about those toxic gases, e.g. Ammonia. As long as it stays where it should be it should be fine. If there is a leakage you may not know of that would be a way bigger problem. Methane would be less critical, just the flammability which shouldn't be worse than hydrogen right?

 

[anonymous]

AFAIK, leakage through the cylinder wall is not a problem and storing pressurized hydrogen even reduces the leakage. We are looking at time frames of 10 years for negligeble loss. So nothing ground breaking for efficiency losses of the system. I don't know about the seal of the filling point though. But I would guess it's not a big problem either, even if there is a little more leakage.

My concern with chemical storage is the further efficiency loss but mostly the safety concern about those toxic gases, e.g. Ammonia. As long as it stays where it should be it should be fine. If there is a leakage you may not know of that would be a way bigger problem. Methane would be less critical, just the flammability which shouldn't be worse than hydrogen right?

I've seen various numbers for hydrogen gas leakage rate from months to years. However, I guess maybe if you use certain materials then this problem would not be too bad. You might be right about this one.

I suspect efficiency loss with chemical storage isn't necessarily going to be worse than loss due to the need to compress/liquefy the gas or heat metal hydride tanks (to release the gas). Although, I might be wrong on that one too.

 

[anonymous]

By the way, there was a new paper from the MacFarlane group relatively recently.