6 ms·

I cannot see how this is useful outside of being a fun student learning program. From the data it appears a battery with 1L of electrolyte provides about 18Wh

I cannot see how this is useful outside of being a fun student learning program. From the data it appears a battery with 1L of electrolyte provides about 18Wh of energy. Mind you this is at ~1.2V, which isn't especially useful without a boost converter. With a boost converter though you would need a low internal impedance from the battery, which I highly doubt is any good with a paper membrane (from what I understand it already isn't great for flow batteries). Meanwhile a pair of 18650 lithium ion batteries can be had for $5 and can provide 24Wh at a very usable 7V with no power conditioning or a range of voltages with more than enough ability to source current. And it is a fraction the size, weight, and complexity. I don't mean to tear apart the project, perhaps there is a key detail I am missing, but I just don't see what this is trying to do outside being a learning experience for students.

msandford 2y ago
Typically if you want to DIY something you first start with the smallest prototype possible and work your way up from there. This demo cell isn't super interesting on its own but to validate the chemistry it's super helpful. Once you got that done you'd then work on a stack of cells, say 10 or 20 or 40 to get up to normal system voltages. Once you have that working it's just a matter of making the tank as big as you want for your storage. Provided the initial chemistry is reasonable you could probably use a pair of IBC totes and really go somewhere.
- Gravityloss 2y ago
  Yeah! The thing about flow batteries is that if we manage to find good chemistries, they have the potential to be very cheap energy storage compared to ordinary batteries. High energy, low power, low cost. Ie the small electrodes cost something but the big bag of fluid might be cheap. Say, vitamin- like substances consisting of extremely common elements like hydrogen, oxygen, nitrogen, carbon etc could be used to store energy in a flow battery. Even with quite low performance, they could be very cheap compared to things like cobalt, nickel, manganese or lithium. Or what about quinones? And sodium, sulphur, sodium are cheap too. There are a lot of very cheap chemistries that could be explored!
- kirksmith 2y ago
  Bingo, this is exactly the plan. Of course there are non-trivial engineering challenges when scaling up, but that's the rough idea.
pjc50 2y ago
"For some scientists doing flow battery experiments in their respective homes/apartments, we’ve got some solid preliminary results" Obviously it's a research project not a commercial product. What do you expect?
Tade0 2y ago
Personally I would find it useful for applications where there needs to be little to no self-discharge and fire safety - like a remote shed with some kind of sensor.
- Workaccount2 2y ago
  You still need something to power the pumps. And we already have long term low power batteries. And solar + battery has filled this role for decades.
  - kirksmith 2y ago
    The pumping cost constitutes a 1-2% total penalty on round-trip energy efficiency for a well-designed flow battery.
heeton 2y ago
Not a battery expert, but this seems the right ballpark for useful batteries. Back of envelope stuff: 1liter for 18Wh. 1k liter 18KWh (this is an average hot tub). 10k litre for 180Kwh. This is a ~$1000 farming tank. ~100KWh lithium batteries are around the $20-30k. (Used Tesla pack for reference) Quick google shows flow electrolyte in the neighbourhood of $100 per KWh. Or $10k for a ~100KWh battery. All this is nothing definitive, but it’s not showing any 10x or 100x differences that would rule out an interesting idea.
- Workaccount2 2y ago
  In order to really make a determination though you need to know what the internal resistance characteristics looks like. 18kWh becomes near useless if it can only source enough current to power your TV at any given time. Or to put that another way: 18kWh doesn't do you much good if you can only draw 200W from it at a time. Given that flow batteries are known for their virtually zero self-discharge, and this project is aiming for a cheap/easy membrane, it seems very likely that internal impedance will kill most use cases here. Mind you I don't think flow batteries themselves are useless to pursue. It's just that I believe a viable flow battery is almost certainly going to be something that requires complex chemistries and advanced manufacturing. In the same way you can build an open source EV from scratch, but you really wouldn't want to ever take that thing on the street.
  - ajford 2y ago
    Why wouldn't you take a scratch-build EV on the road? People build kit-cars all the time, and an EV has a much simpler control system. This is a very simplified project to prove the concept and provide a test bed for further exploration, not an end-product by any stretch. This seems like the perfect project to test various membranes and electrolyte solutions.
    - Workaccount2 2y ago
      >Why wouldn't you take a scratch-build EV on the road? Because you don't want to snap your spine in a minor fender bender. Scratch built is not the same thing as an EV conversion kit, where all the hard stuff (like a frame and body panels) was already made by commercial manufacturers. This flow battery is from scratch (well except for the pumps and electronics, but the cell itself is). They are not using off the shelf electrolyte and electrochemical cells like a flow battery kit would. It's a neat project and would teach a lot, but I just cannot find a scenario in my head where I would want this (even a scaled up version) over another solution.
marcosdumay 2y ago
You are missing that this is just some salts dissolved in water, while the 18650 is a highly complex device. How much does it cost to store 10m^3 of water? And hos much does it cost to store the same energy in 18650 batteries? Also, the internal resistance depends entirely on how many cells you have. But a practical battery wouldn't use paper.
- Workaccount2 2y ago
  >Also, the internal resistance depends entirely on how many cells you have. Right, from the one study I can find, commercial flow batteries have about 10-20x the internal resistance of a lithium ion battery, so the match the power and energy capabilities of a single li-ion cell you would need a liter of electrolyte and about 30 (!) cells (3 for voltage x 10 for power). And that is for a commercial quality flow battery. And lithium ion batteries are wholesale in the $2 a piece range. I'm not trying to say flow batteries are stupid or dumb, but their use cases are going to be very limited without some huge breakthroughs that will probably dramatically increase the complexity too.
  - entropicdrifter 2y ago
    Their use cases would become extremely relevant to people trying to rebuild society from scratch, I'd imagine. This device is so simple you could probably build one in the woods with nothing but a basic survival kit given a year or two alone. So that's something. Learning how to build one from scratch seems worthwhile, much like learning to build a radio from scratch
  - Dylan16807 2y ago
    Unless you're flying a drone, you don't need to match the power and energy capabilities of lithium ion. On top of that, you don't have to match the internal resistance to match power. If you have plenty of material to absorb the heat, then you can tolerate more percentage points of loss. In particular, while lithium ion batteries can be built to sacrifice discharge rate for a bit of extra capacity, something like a 3C discharge rate is easy enough to reach. And if your use case is powering a building for several hours, you might only need a .2C discharge rate. That would mean lithium ion as a technology is 15x overqualified, and a flow battery that gives you 10x less power would still be overqualified.
K0balt 2y ago
This is awesome! Obviously we’d need a real ion exchange membrane and put 40 of them in series, but it looks pretty scalable even in its present form. This looks very practical to me, once a few more years of tinkering is done. I’d love to have more information about electrode fluid cost, life and reconditioning/reprocessing, as well as power densities for membrane area. I’d love to be able to add capacity just by adding tanks and electrode fluid! For microgrids like ours, this is a longstanding goal.
KennyBlanken 2y ago
Flow batteries are optimized for cost and capacity. Not weight, nor volume/energy density, nor instantaneous power delivery. In the case of some iron flow designs, add in "dirt-cheap, non-toxic materials." A pair of 55 gallon drums equals 7.4kWh, and I'm guessing a lot of us could easily find that much space in our basements. That's enough to power 300W of load 24x7 (a modern fridge is about 60W. 100W will get you really far in terms of LED lighting given that most "60W" bulbs are well under 10W these days.) One "car battery" sized LiFePO4 battery is about 1400Wh, and costs anywhere from $100 to $500+ depending on the manufacturer/reseller. I'm a little mystified why they didn't go with a simpler iron-flow design as it is very cheap, and can be nearly completely non-toxic.
- pfdietz 2y ago
  The actor I'm mildly paying attention to is Lockheed-Martin, who have an energy systems group that's working on flow batteries. Judging by patents, their flow battery likely uses various transition element ions that are kept in solution with any of a variety of organic ligands. The wide variety of chemistries is the attractive part, since they present many knobs to twiddle for optimization.
- kirksmith 2y ago
  Iron plating is a hydrogen evolution nightmare. It's interesting for sure, but not feasible for a simple demonstration system, due to pH issues and oxidation state drift from hydrogen evolution. We do plan to explore it in the future, and move onto larger cells/stacks that offer practical amounts of storage.
ForOldHack 2y ago
There are two key details you are missing: 1) Its scalable to dishwasher size, ( enough to power a tiny house ) 2) If you shot it with a bullet, it would just leak salt water. That is all. Lithium Ion will explode: Now here is the quiz: If you have a cell phone that is inflating, do you A) Dunk it in water? or B) Toss it in a full document safe? or c) Quickly empty your document safe, and toss it in? If a flow battery leaks, you can toss in a chicken into the delightful brine. Since you cannot scale this easily to Utility sized batteries easily, the D.O.E. is not interested. i.e. if you are looking to scale this to a couple of hundred megawatts, just stop reading and thinking about this now. This is NOT mobile. Its not useful for cars or cities. Its right sized for homes.
- 0cf8612b2e1e 2y ago
  … if you are looking to scale this to a couple of hundred megawatts, just stop reading and thinking about this now I thought that was one huge appeal of flow batteries is that you can basically infinitely scale them. China has a 100MW installation (potentially more since this 2022 report) https://www.pv-magazine.com/2022/09/29/china-connects-worlds-largest-redox-flow-battery-system-to-grid/ https://www.pv-magazine.com/2022/09/29/china-connects-worlds...
  - briffle 2y ago
    These guys in the US make a 500kwh version, that can run at 75kw of discharge power across 3 phases, and its a single shipping container: https://essinc.com/energy-warehouse/ https://essinc.com/energy-warehouse/ It doesn't seem like it would take up that much space to have 200 shipping containers sitting somewhere, i'm pretty sure the Home Depot distrubution center in our town already is close to that in their parking lot (yes, you would want them not on wheels, and farther apart)
    - 0cf8612b2e1e 2y ago
      That’s incredible. I wonder what are the costs relative to a grid scale battery of equivalent size. I only wish they made one that were barrel sized and fit for consumers. Worst case, you have a leak vs a home battery fire.
gwbas1c 2y ago
> I just don't see what this is trying to do outside being a learning experience for students. Perhaps one of those students will figure out how to make a useful large scale flow battery? I have solar, and the missing piece is being able to store electricity for the winter. Perhaps the person who figures it out learned something from a project like this?
beAbU 2y ago
This website is called hacker news. I think you are missing the point of this post.

msandford 2y ago

Typically if you want to DIY something you first start with the smallest prototype possible and work your way up from there. This demo cell isn't super interesting on its own but to validate the chemistry it's super helpful. Once you got that done you'd then work on a stack of cells, say 10 or 20 or 40 to get up to normal system voltages. Once you have that working it's just a matter of making the tank as big as you want for your storage. Provided the initial chemistry is reasonable you could probably use a pair of IBC totes and really go somewhere.

Gravityloss 2y ago
Yeah! The thing about flow batteries is that if we manage to find good chemistries, they have the potential to be very cheap energy storage compared to ordinary batteries. High energy, low power, low cost. Ie the small electrodes cost something but the big bag of fluid might be cheap. Say, vitamin- like substances consisting of extremely common elements like hydrogen, oxygen, nitrogen, carbon etc could be used to store energy in a flow battery. Even with quite low performance, they could be very cheap compared to things like cobalt, nickel, manganese or lithium. Or what about quinones? And sodium, sulphur, sodium are cheap too. There are a lot of very cheap chemistries that could be explored!
kirksmith 2y ago
Bingo, this is exactly the plan. Of course there are non-trivial engineering challenges when scaling up, but that's the rough idea.

pjc50 2y ago

"For some scientists doing flow battery experiments in their respective homes/apartments, we’ve got some solid preliminary results" Obviously it's a research project not a commercial product. What do you expect?

Tade0 2y ago

Personally I would find it useful for applications where there needs to be little to no self-discharge and fire safety - like a remote shed with some kind of sensor.

Workaccount2 2y ago
You still need something to power the pumps. And we already have long term low power batteries. And solar + battery has filled this role for decades.
- kirksmith 2y ago
  The pumping cost constitutes a 1-2% total penalty on round-trip energy efficiency for a well-designed flow battery.

heeton 2y ago

Not a battery expert, but this seems the right ballpark for useful batteries. Back of envelope stuff: 1liter for 18Wh. 1k liter 18KWh (this is an average hot tub). 10k litre for 180Kwh. This is a ~$1000 farming tank. ~100KWh lithium batteries are around the $20-30k. (Used Tesla pack for reference) Quick google shows flow electrolyte in the neighbourhood of $100 per KWh. Or $10k for a ~100KWh battery. All this is nothing definitive, but it’s not showing any 10x or 100x differences that would rule out an interesting idea.

Workaccount2 2y ago
In order to really make a determination though you need to know what the internal resistance characteristics looks like. 18kWh becomes near useless if it can only source enough current to power your TV at any given time. Or to put that another way: 18kWh doesn't do you much good if you can only draw 200W from it at a time. Given that flow batteries are known for their virtually zero self-discharge, and this project is aiming for a cheap/easy membrane, it seems very likely that internal impedance will kill most use cases here. Mind you I don't think flow batteries themselves are useless to pursue. It's just that I believe a viable flow battery is almost certainly going to be something that requires complex chemistries and advanced manufacturing. In the same way you can build an open source EV from scratch, but you really wouldn't want to ever take that thing on the street.
- ajford 2y ago
  Why wouldn't you take a scratch-build EV on the road? People build kit-cars all the time, and an EV has a much simpler control system. This is a very simplified project to prove the concept and provide a test bed for further exploration, not an end-product by any stretch. This seems like the perfect project to test various membranes and electrolyte solutions.
  - Workaccount2 2y ago
    >Why wouldn't you take a scratch-build EV on the road? Because you don't want to snap your spine in a minor fender bender. Scratch built is not the same thing as an EV conversion kit, where all the hard stuff (like a frame and body panels) was already made by commercial manufacturers. This flow battery is from scratch (well except for the pumps and electronics, but the cell itself is). They are not using off the shelf electrolyte and electrochemical cells like a flow battery kit would. It's a neat project and would teach a lot, but I just cannot find a scenario in my head where I would want this (even a scaled up version) over another solution.

marcosdumay 2y ago

You are missing that this is just some salts dissolved in water, while the 18650 is a highly complex device. How much does it cost to store 10m^3 of water? And hos much does it cost to store the same energy in 18650 batteries? Also, the internal resistance depends entirely on how many cells you have. But a practical battery wouldn't use paper.

Workaccount2 2y ago
>Also, the internal resistance depends entirely on how many cells you have. Right, from the one study I can find, commercial flow batteries have about 10-20x the internal resistance of a lithium ion battery, so the match the power and energy capabilities of a single li-ion cell you would need a liter of electrolyte and about 30 (!) cells (3 for voltage x 10 for power). And that is for a commercial quality flow battery. And lithium ion batteries are wholesale in the $2 a piece range. I'm not trying to say flow batteries are stupid or dumb, but their use cases are going to be very limited without some huge breakthroughs that will probably dramatically increase the complexity too.
- entropicdrifter 2y ago
  Their use cases would become extremely relevant to people trying to rebuild society from scratch, I'd imagine. This device is so simple you could probably build one in the woods with nothing but a basic survival kit given a year or two alone. So that's something. Learning how to build one from scratch seems worthwhile, much like learning to build a radio from scratch
- Dylan16807 2y ago
  Unless you're flying a drone, you don't need to match the power and energy capabilities of lithium ion. On top of that, you don't have to match the internal resistance to match power. If you have plenty of material to absorb the heat, then you can tolerate more percentage points of loss. In particular, while lithium ion batteries can be built to sacrifice discharge rate for a bit of extra capacity, something like a 3C discharge rate is easy enough to reach. And if your use case is powering a building for several hours, you might only need a .2C discharge rate. That would mean lithium ion as a technology is 15x overqualified, and a flow battery that gives you 10x less power would still be overqualified.

K0balt 2y ago

This is awesome! Obviously we’d need a real ion exchange membrane and put 40 of them in series, but it looks pretty scalable even in its present form. This looks very practical to me, once a few more years of tinkering is done. I’d love to have more information about electrode fluid cost, life and reconditioning/reprocessing, as well as power densities for membrane area. I’d love to be able to add capacity just by adding tanks and electrode fluid! For microgrids like ours, this is a longstanding goal.

KennyBlanken 2y ago

Flow batteries are optimized for cost and capacity. Not weight, nor volume/energy density, nor instantaneous power delivery. In the case of some iron flow designs, add in "dirt-cheap, non-toxic materials." A pair of 55 gallon drums equals 7.4kWh, and I'm guessing a lot of us could easily find that much space in our basements. That's enough to power 300W of load 24x7 (a modern fridge is about 60W. 100W will get you really far in terms of LED lighting given that most "60W" bulbs are well under 10W these days.) One "car battery" sized LiFePO4 battery is about 1400Wh, and costs anywhere from $100 to $500+ depending on the manufacturer/reseller. I'm a little mystified why they didn't go with a simpler iron-flow design as it is very cheap, and can be nearly completely non-toxic.

pfdietz 2y ago
The actor I'm mildly paying attention to is Lockheed-Martin, who have an energy systems group that's working on flow batteries. Judging by patents, their flow battery likely uses various transition element ions that are kept in solution with any of a variety of organic ligands. The wide variety of chemistries is the attractive part, since they present many knobs to twiddle for optimization.
kirksmith 2y ago
Iron plating is a hydrogen evolution nightmare. It's interesting for sure, but not feasible for a simple demonstration system, due to pH issues and oxidation state drift from hydrogen evolution. We do plan to explore it in the future, and move onto larger cells/stacks that offer practical amounts of storage.

ForOldHack 2y ago

There are two key details you are missing: 1) Its scalable to dishwasher size, ( enough to power a tiny house ) 2) If you shot it with a bullet, it would just leak salt water. That is all. Lithium Ion will explode: Now here is the quiz: If you have a cell phone that is inflating, do you A) Dunk it in water? or B) Toss it in a full document safe? or c) Quickly empty your document safe, and toss it in? If a flow battery leaks, you can toss in a chicken into the delightful brine. Since you cannot scale this easily to Utility sized batteries easily, the D.O.E. is not interested. i.e. if you are looking to scale this to a couple of hundred megawatts, just stop reading and thinking about this now. This is NOT mobile. Its not useful for cars or cities. Its right sized for homes.

0cf8612b2e1e 2y ago
… if you are looking to scale this to a couple of hundred megawatts, just stop reading and thinking about this now I thought that was one huge appeal of flow batteries is that you can basically infinitely scale them. China has a 100MW installation (potentially more since this 2022 report) https://www.pv-magazine.com/2022/09/29/china-connects-worlds-largest-redox-flow-battery-system-to-grid/ https://www.pv-magazine.com/2022/09/29/china-connects-worlds...
- briffle 2y ago
  These guys in the US make a 500kwh version, that can run at 75kw of discharge power across 3 phases, and its a single shipping container: https://essinc.com/energy-warehouse/ https://essinc.com/energy-warehouse/ It doesn't seem like it would take up that much space to have 200 shipping containers sitting somewhere, i'm pretty sure the Home Depot distrubution center in our town already is close to that in their parking lot (yes, you would want them not on wheels, and farther apart)
  - 0cf8612b2e1e 2y ago
    That’s incredible. I wonder what are the costs relative to a grid scale battery of equivalent size. I only wish they made one that were barrel sized and fit for consumers. Worst case, you have a leak vs a home battery fire.

gwbas1c 2y ago

> I just don't see what this is trying to do outside being a learning experience for students. Perhaps one of those students will figure out how to make a useful large scale flow battery? I have solar, and the missing piece is being able to store electricity for the winter. Perhaps the person who figures it out learned something from a project like this?

beAbU 2y ago

This website is called hacker news. I think you are missing the point of this post.