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> showed that the battery had a charge densities of about 1,322 watts per liter of electrolyte and a discharge density of about 306 W/L Isn't the relevant meas

> showed that the battery had a charge densities of about 1,322 watts per liter of electrolyte and a discharge density of about 306 W/L Isn't the relevant measurement energy density (Wh/L) rather than power (W/L)? I guess there's some limit on the power generated by a given volume of the battery, but in practice it seems like the main question is how big the tank has to be per MWH/KWH, rather than how big the power module has to be to convert that back to energy over the duration of the discharge period.

amluto 4y ago
No. From the article: > Liu and colleagues focused on redesigning the power module A flow battery separates the power portion (the electronics, electrodes, pumps, etc) from the energy portion (tanks, fluid). Which is not so amazing for a car or a UPS where you want tens of minutes to a few hours of charge or discharge time, but is potentially great for grid use, where a discharge time of days to months is useful.
- mgerdts 4y ago
  Why wouldn’t it be good for cars? It seems a fluid exchange could recharge the car, limited by how fast you can pump out the discharged fluid and pump in charged fluid. I have no idea whether there are containment or environmental challenges that make this especially hard.
  - randall 4y ago
    That sounds like moving to a non solid state situation, right? One of the big benefits, imo, is removing as many moving parts from a car, not reintroducing them.
    - mgerdts 4y ago
      Surely it is more complicated. It may be able to serve the goal of eliminating fossil fuels from the car while not getting the full simplicity of (not really) solid state batteries we have today. It would seemingly also allow you to carry around 50 miles of juice when you are running around town and bump up to 400 miles of juice when you are taking a road trip. This really only makes sense if the car is able to recharge the juice. Maybe a new hybrid model (not gas electric hybrid) could emerge. The base (say 50 mile) capacity is solidish state like we have today and a flow battery range extender could be filled with fluid when the extended range is needed. This would make it so the car wouldn’t need to charge the fluid, if that helps.
      - m463 4y ago
        I could see a hierarchy of power in a car, or truck/rv. motor <-> lithium <-> flow battery the low current from the flow battery could be continuously augmenting and replenishing the lithium ion battery or even: supercapacitor <-> lithium <-> flow battery
    - jacobn 4y ago
      Being able to "refuel" quickly is a pretty big plus, so in the balance it could still be better to accept some moving parts in exchange for that. And it's easy to imagine retrofitting a gas station to all of a sudden have charged electrolyte instead of gas, but I'm sure that has all sorts of additional complexities that I know nothing about... ;)
    - jccooper 4y ago
      Probably adds two low-pressure low-volume pumps. Which is more, but not a large increase in complexity for a car. The driver's seat probably has more moving parts.
  - hinkley 4y ago
    It’s going to depend on the details. In a power substation space and weight are fairly flexible. In a vehicle they matter quite a bit. If you can build a flow battery that rivals solid state batteries for weight and volume, you’ve made an improvement because the fluid is swappable in ways that batteries are not. Batteries meant to move will move in a crash. Fixed batteries tend to stay put but complicate road trips. In a UPS the tanks and valves and pumps are new points of failure, as the other responder states. In a car they are many times more complicated than electric vehicles, yes, but still less complicated than ICE vehicles by far. Your heater has more moving parts. Hell, the emissions control gear is probably more complex than the entire drivetrain of the electric vehicle.
  - amluto 4y ago
    If one can actually make a useful economy out of replacing flow battery fluid at a station, sure. But I’m making a different point: A Li-Ion battery can charge and discharge in something like an hour. If you double the number of cells in a battery or installation, you can store twice as much energy and you can draw twice as much power. (You don’t have to provision twice as much power circuitry, but you do need to purchase that extra power worth of electrodes in the cells.) If you’re building something for which a roughly predetermined power to energy ratio (i.e. hours of use at a reasonable rate of discharge for the technology), this is fine. Similarly, if overprovisioning power or energy is not a problem for cost or weight, also fine. But for grid use, wide differences in the duration of energy storage for different purposes can make sense. And a flow battery can separately provision power and energy. This gives a possible cost benefit to flow batteries.
  - ilyt 4y ago
    Flow batteries have way less current capacity so it could plainly not be powerful enough. It also have lower energy density so you pumping 600l of new electrolyte on the station might still give you only 200km of range
    - m463 4y ago
      Could it be good for a long-haul truck? or maybe a locomotive, which is less sensitive to weight and cargo capacity?
      - ilyt 4y ago
        It kinda depends to what power density it gets. Trading say 30% range for ability to refill the truck within minutes might just make enough sense to work. But if, say, electric truck gets enough range to run the full 9 hours (max allowed driving time per day in EU for truck drivers), then it doesn't matter as trucker can do "100% of their work", get to stop and leave it to charge for rest of the day. For locomotives ? I'd imagine the simplest solution would be to have "battery wagon" ; get on the station, replace the battery wagon, and be on your merry way while it is recharging in the station waiting for next train to pick it up, at least for the long haul stuff. But capacity density still matters, if flow batteries are being close and cheaper then it makes sense, but if you need to pay slighty more per KWh but get 2x the capactity... thats 2x the range and less maintenance. Or, you know, just electric rail. It already works fine in many places. I wonder if making some hybrid solution with electric rails also being covered by solar panels (basically so same maintenance crew can manage both) would make sense So it all depends to what level of density it gets. If it is same capacity per kg but lower power there are still many places it can be used, if it is much lower it stops being sensible for moving stuff. And the price would need to be significantly below the normal batteries for anyone to even bother.
      - Schroedingersat 4y ago
        Trucks are weight limited with LFP, costs already favour electric even with NMC but the tradeoff is payload. Trains maybe, but surely the money is better spent on overhead wire? Even if tunnels/bridges/etc. can't take it you're better with just the power-buffer battery and no flow battery.
- gumby 4y ago
  > for grid use, where a discharge time of days to months is useful. Not sure I know the use case for a duration of that length. It's possible today with pumped hydro, but I don't think it's used in that mode. The DoE's "long duration storage earthshot" effort is loking for 10+ hours, which makes more sense: https://www.energy.gov/eere/long-duration-storage-shot https://www.energy.gov/eere/long-duration-storage-shot
  - jfoutz 4y ago
    The standard reply to any sort of gravity storage is "geography and land availability". I don't find that argument compelling enough to dismiss gravity storage outright, but I'll admit Oklahoma is pretty darn flat. Chemical storage could be a big win when a mountain isn't readily available. Or the land is too expensive to use for power storage.
    - marmadukester39 4y ago
      Decommissioned mines. Saw an article about it somewhere recently.
      - bobthepanda 4y ago
        Really, you just need any elevation difference. I would imagine Oklahoma already builds water towers.
  - michaelt 4y ago
    A zero-carbon northern Europe that replaced all gas heating with heat pumps would benefit from being able to store electricity during the warm summer months, to power heating in the cold winter months. There are other options, of course - new nuclear plants, importing renewable power from countries with better weather, huge numbers of wind turbines, and so on - but cost-effective long-term power storage would address some issues if it was available.
    - nl 4y ago
- somethoughts 4y ago
  Form Energy seems to be landing new pilot projects with US utilities. Form Energy is an American energy storage company focused on developing a new class of cost-effective, multi-day energy storage systems that will enable a reliable and fully-renewable electric grid year-round. Form Energy's first commercial product is a rechargeable iron-air battery capable of storing electricity for 100 hours at system costs competitive with legacy power plants. [1] [1] https://en.wikipedia.org/wiki/Form_Energy https://en.wikipedia.org/wiki/Form_Energy
deleted 4y ago
[deleted]
imtringued 4y ago
A smaller charger/discharger simply costs less which lets you buy more electrolyte. This is especially relevant for smaller installations.
LeanderK 4y ago
(I know nothing about batteries or chemistry) I think this research only focuses on power generation, the device where you combine the liquids to get energy. Changing the energy density means changing the type of liquid, I assume, which this research is just not about. I understand it as analogous to a ICE, where you have the fuel and the motor. But with flow batteries you can also go in reverse to create fuel from energy. The research featured here is about the motor but if you need a different energy density you have to change the type of fuel since that's how the energy is just stored in huge tanks.
marcosdumay 4y ago
The article is about the size of the ion-exchange element, so I'd guess no, it's not supposed to be Wh/l. If you want the storage density, you can look by the battery chemistry. But I'm not sure the article got this one right, or else the researchers didn't actually work on flow batteries and that part is only speculation.
dtgriscom 4y ago
If you go to the source article, this is stated as: >our SBMT cell shows peak charge and discharge power densities of 1,322 W/Lcell and 306.1 W/Lcell, respectively, compared with average charge and discharge power densities of <60 W/Lcell and 45 W/Lcell, respectively, of conventional planar flow battery cells. So, it's not per volume of electrolyte, but per volume of the entire cell (housing included).

amluto 4y ago

No. From the article: > Liu and colleagues focused on redesigning the power module A flow battery separates the power portion (the electronics, electrodes, pumps, etc) from the energy portion (tanks, fluid). Which is not so amazing for a car or a UPS where you want tens of minutes to a few hours of charge or discharge time, but is potentially great for grid use, where a discharge time of days to months is useful.

mgerdts 4y ago
Why wouldn’t it be good for cars? It seems a fluid exchange could recharge the car, limited by how fast you can pump out the discharged fluid and pump in charged fluid. I have no idea whether there are containment or environmental challenges that make this especially hard.
- randall 4y ago
  That sounds like moving to a non solid state situation, right? One of the big benefits, imo, is removing as many moving parts from a car, not reintroducing them.
  - mgerdts 4y ago
    Surely it is more complicated. It may be able to serve the goal of eliminating fossil fuels from the car while not getting the full simplicity of (not really) solid state batteries we have today. It would seemingly also allow you to carry around 50 miles of juice when you are running around town and bump up to 400 miles of juice when you are taking a road trip. This really only makes sense if the car is able to recharge the juice. Maybe a new hybrid model (not gas electric hybrid) could emerge. The base (say 50 mile) capacity is solidish state like we have today and a flow battery range extender could be filled with fluid when the extended range is needed. This would make it so the car wouldn’t need to charge the fluid, if that helps.
    - m463 4y ago
      I could see a hierarchy of power in a car, or truck/rv. motor <-> lithium <-> flow battery the low current from the flow battery could be continuously augmenting and replenishing the lithium ion battery or even: supercapacitor <-> lithium <-> flow battery
  - jacobn 4y ago
    Being able to "refuel" quickly is a pretty big plus, so in the balance it could still be better to accept some moving parts in exchange for that. And it's easy to imagine retrofitting a gas station to all of a sudden have charged electrolyte instead of gas, but I'm sure that has all sorts of additional complexities that I know nothing about... ;)
  - jccooper 4y ago
    Probably adds two low-pressure low-volume pumps. Which is more, but not a large increase in complexity for a car. The driver's seat probably has more moving parts.
- hinkley 4y ago
  It’s going to depend on the details. In a power substation space and weight are fairly flexible. In a vehicle they matter quite a bit. If you can build a flow battery that rivals solid state batteries for weight and volume, you’ve made an improvement because the fluid is swappable in ways that batteries are not. Batteries meant to move will move in a crash. Fixed batteries tend to stay put but complicate road trips. In a UPS the tanks and valves and pumps are new points of failure, as the other responder states. In a car they are many times more complicated than electric vehicles, yes, but still less complicated than ICE vehicles by far. Your heater has more moving parts. Hell, the emissions control gear is probably more complex than the entire drivetrain of the electric vehicle.
- amluto 4y ago
  If one can actually make a useful economy out of replacing flow battery fluid at a station, sure. But I’m making a different point: A Li-Ion battery can charge and discharge in something like an hour. If you double the number of cells in a battery or installation, you can store twice as much energy and you can draw twice as much power. (You don’t have to provision twice as much power circuitry, but you do need to purchase that extra power worth of electrodes in the cells.) If you’re building something for which a roughly predetermined power to energy ratio (i.e. hours of use at a reasonable rate of discharge for the technology), this is fine. Similarly, if overprovisioning power or energy is not a problem for cost or weight, also fine. But for grid use, wide differences in the duration of energy storage for different purposes can make sense. And a flow battery can separately provision power and energy. This gives a possible cost benefit to flow batteries.
- ilyt 4y ago
  Flow batteries have way less current capacity so it could plainly not be powerful enough. It also have lower energy density so you pumping 600l of new electrolyte on the station might still give you only 200km of range
  - m463 4y ago
    Could it be good for a long-haul truck? or maybe a locomotive, which is less sensitive to weight and cargo capacity?
    - ilyt 4y ago
      It kinda depends to what power density it gets. Trading say 30% range for ability to refill the truck within minutes might just make enough sense to work. But if, say, electric truck gets enough range to run the full 9 hours (max allowed driving time per day in EU for truck drivers), then it doesn't matter as trucker can do "100% of their work", get to stop and leave it to charge for rest of the day. For locomotives ? I'd imagine the simplest solution would be to have "battery wagon" ; get on the station, replace the battery wagon, and be on your merry way while it is recharging in the station waiting for next train to pick it up, at least for the long haul stuff. But capacity density still matters, if flow batteries are being close and cheaper then it makes sense, but if you need to pay slighty more per KWh but get 2x the capactity... thats 2x the range and less maintenance. Or, you know, just electric rail. It already works fine in many places. I wonder if making some hybrid solution with electric rails also being covered by solar panels (basically so same maintenance crew can manage both) would make sense So it all depends to what level of density it gets. If it is same capacity per kg but lower power there are still many places it can be used, if it is much lower it stops being sensible for moving stuff. And the price would need to be significantly below the normal batteries for anyone to even bother.
    - Schroedingersat 4y ago
      Trucks are weight limited with LFP, costs already favour electric even with NMC but the tradeoff is payload. Trains maybe, but surely the money is better spent on overhead wire? Even if tunnels/bridges/etc. can't take it you're better with just the power-buffer battery and no flow battery.
gumby 4y ago
> for grid use, where a discharge time of days to months is useful. Not sure I know the use case for a duration of that length. It's possible today with pumped hydro, but I don't think it's used in that mode. The DoE's "long duration storage earthshot" effort is loking for 10+ hours, which makes more sense: https://www.energy.gov/eere/long-duration-storage-shot https://www.energy.gov/eere/long-duration-storage-shot
- jfoutz 4y ago
  The standard reply to any sort of gravity storage is "geography and land availability". I don't find that argument compelling enough to dismiss gravity storage outright, but I'll admit Oklahoma is pretty darn flat. Chemical storage could be a big win when a mountain isn't readily available. Or the land is too expensive to use for power storage.
  - marmadukester39 4y ago
    Decommissioned mines. Saw an article about it somewhere recently.
    - bobthepanda 4y ago
      Really, you just need any elevation difference. I would imagine Oklahoma already builds water towers.
- michaelt 4y ago
  A zero-carbon northern Europe that replaced all gas heating with heat pumps would benefit from being able to store electricity during the warm summer months, to power heating in the cold winter months. There are other options, of course - new nuclear plants, importing renewable power from countries with better weather, huge numbers of wind turbines, and so on - but cost-effective long-term power storage would address some issues if it was available.
  - nl 4y ago
somethoughts 4y ago
Form Energy seems to be landing new pilot projects with US utilities. Form Energy is an American energy storage company focused on developing a new class of cost-effective, multi-day energy storage systems that will enable a reliable and fully-renewable electric grid year-round. Form Energy's first commercial product is a rechargeable iron-air battery capable of storing electricity for 100 hours at system costs competitive with legacy power plants. [1] [1] https://en.wikipedia.org/wiki/Form_Energy https://en.wikipedia.org/wiki/Form_Energy

deleted 4y ago

[deleted]

imtringued 4y ago

A smaller charger/discharger simply costs less which lets you buy more electrolyte. This is especially relevant for smaller installations.

LeanderK 4y ago

(I know nothing about batteries or chemistry) I think this research only focuses on power generation, the device where you combine the liquids to get energy. Changing the energy density means changing the type of liquid, I assume, which this research is just not about. I understand it as analogous to a ICE, where you have the fuel and the motor. But with flow batteries you can also go in reverse to create fuel from energy. The research featured here is about the motor but if you need a different energy density you have to change the type of fuel since that's how the energy is just stored in huge tanks.

marcosdumay 4y ago

The article is about the size of the ion-exchange element, so I'd guess no, it's not supposed to be Wh/l. If you want the storage density, you can look by the battery chemistry. But I'm not sure the article got this one right, or else the researchers didn't actually work on flow batteries and that part is only speculation.

dtgriscom 4y ago

If you go to the source article, this is stated as: >our SBMT cell shows peak charge and discharge power densities of 1,322 W/Lcell and 306.1 W/Lcell, respectively, compared with average charge and discharge power densities of <60 W/Lcell and 45 W/Lcell, respectively, of conventional planar flow battery cells. So, it's not per volume of electrolyte, but per volume of the entire cell (housing included).