(Redox) Flow Battery

Piwoslaw · 05-20-18, 03:55 PM

I just found out about a method for storing energy - the (Redox) Flow Battery or RFB.

In short - It is a battery which stores the energy in separate electrolyte tanks, instead of all together in one package. Some of the recently tested solutions are water-based, non-toxic and not flammable, so the RFB could become cheaper, and could be stored in a household basement. The power (battery/membrane) and energy (electrolyte) components are independent of each other, so either can be scaled, expanded or replaced according to needs. RFBs supposedly do not have a limit on the number of charge/discharge cycles, and can be safely discharged as deep as 0%.

I found somewhere that if the cost could come below 100USD per kWh, then it would make Renewable Energy more competitive than traditional power plants. (The lowest cost commercial RFB I could find - Imergy ESP30 - is around 300USD per kWh)

Also found an article that proposed using RFB on a micro scale in between electronic chips, as RFBs could supposedly cool these chips while powering them.

Has anyone read anything more up to date on the possibilities of these? Whether they are already mainstream for microgrids or big utilities?

oil pan 4 · 05-20-18, 07:25 PM

Sounds like an Edison cell.

$300 per KwH is astounding.
If I wanted to make 1 KwH out of LiFePO4 cells it would cost some where around $1,000 with the lowest price I have ever seen on 20AH prizmatic cells.
That's just for the cells, not hooking them up or including the enclosure.

Piwoslaw · 02-07-21, 03:40 PM

I found the below article in PV Magazine which claims that the cost of industrial scale RFBs could now be $66/kWh, and could go as low as $54/kWh.
Redox flow batteries for $66/kWh from steel industry waste

jeff5may · 02-08-21, 02:46 AM

Redox flow batteries have been around a long time. They work. Problem is that they have low energy density and low current density. You can run lead-acid batteries this way. Just change the acid.

The main way to get a high capacity, high current flow battery is to go big. The iron chemistries have an electrode power density around 200W/m², and iron is pretty heavy stuff. The vanadium and lead chemistries have high enough electrode current density to make the liquid fuel a factor. The liquid fuel energy density is around 25 to 50 watt hours per liter for the common ones. If you have a spare empty warehouse or barn, that's probably enough space for all of the equipment.

Haven't paid much attention the last couple of years. Liion batteries are gaining traction, and have ample energy density for residential applications and light commercial stuff. Tesla is putting the rubber to the road and burning donuts with Liion batteries as we speak.

Dr. Musk is pretty good about furthering the state of whatever he gets involved in, and battery technology is no different. He's chasing the "million mile battery" for his cars, and is already repurposing used car battery arrays for utility-scale power grid storage. He's talking crazy as usual, this time planning on a battery "tera factory" to ramp up production of three or more lithium chemistries. His current goal is to drive at least one of them below $60/kwh. We shall see...

Piwoslaw · 11-04-23, 03:13 PM

Read a bit more on these. Turns out they can switch between storing and producing energy very quickly, reaction time below 1 second. Many other types of batteries need to "rest" in between cycles to avoid or reduce internal deterioration.

They are guaranteed for 20k-100k cycles.
Efficiency is 70-80% .

Also, there is no danger if the '+' and '-' liquids accidentally mix - no overheating, no explosion.

Quote:

Originally Posted by jeff5may

The liquid fuel energy density is around 25 to 50 watt hours per liter for the common ones. If you have a spare empty warehouse or barn, that's probably enough space for all of the equipment.

I saw a commercial flow battery with 35 Wh per liter. For home needs (10-20 kWh) this is 300-600 liters, which would take up a corner in the basement.
A larger commercial system (120 kWh) weighs 13 tons and has dimensions 5.8x2.2x2.8 meters, so indeed utility-sized systems (100-500 kWh) would need a large room or separate building.

05-20-18, 03:55 PM	#1
Piwoslaw Super Moderator Join Date: May 2009 Location: Warsaw, Poland Posts: 964 Thanks: 189 Thanked 111 Times in 87 Posts	(Redox) Flow Battery I just found out about a method for storing energy - the (Redox) Flow Battery or RFB. In short - It is a battery which stores the energy in separate electrolyte tanks, instead of all together in one package. Some of the recently tested solutions are water-based, non-toxic and not flammable, so the RFB could become cheaper, and could be stored in a household basement. The power (battery/membrane) and energy (electrolyte) components are independent of each other, so either can be scaled, expanded or replaced according to needs. RFBs supposedly do not have a limit on the number of charge/discharge cycles, and can be safely discharged as deep as 0%. I found somewhere that if the cost could come below 100USD per kWh, then it would make Renewable Energy more competitive than traditional power plants. (The lowest cost commercial RFB I could find - Imergy ESP30 - is around 300USD per kWh) Also found an article that proposed using RFB on a micro scale in between electronic chips, as RFBs could supposedly cool these chips while powering them. Has anyone read anything more up to date on the possibilities of these? Whether they are already mainstream for microgrids or big utilities? __________________ Ecorenovation - the bottomless piggy bank that tries to tame the energy hog.

02-07-21, 03:40 PM	#3
Piwoslaw Super Moderator Join Date: May 2009 Location: Warsaw, Poland Posts: 964 Thanks: 189 Thanked 111 Times in 87 Posts	I found the below article in PV Magazine which claims that the cost of industrial scale RFBs could now be $66/kWh, and could go as low as $54/kWh. Redox flow batteries for $66/kWh from steel industry waste __________________ Ecorenovation - the bottomless piggy bank that tries to tame the energy hog.

02-08-21, 02:46 AM	#4
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	Redox flow batteries have been around a long time. They work. Problem is that they have low energy density and low current density. You can run lead-acid batteries this way. Just change the acid. The main way to get a high capacity, high current flow battery is to go big. The iron chemistries have an electrode power density around 200W/m², and iron is pretty heavy stuff. The vanadium and lead chemistries have high enough electrode current density to make the liquid fuel a factor. The liquid fuel energy density is around 25 to 50 watt hours per liter for the common ones. If you have a spare empty warehouse or barn, that's probably enough space for all of the equipment. Haven't paid much attention the last couple of years. Liion batteries are gaining traction, and have ample energy density for residential applications and light commercial stuff. Tesla is putting the rubber to the road and burning donuts with Liion batteries as we speak. Dr. Musk is pretty good about furthering the state of whatever he gets involved in, and battery technology is no different. He's chasing the "million mile battery" for his cars, and is already repurposing used car battery arrays for utility-scale power grid storage. He's talking crazy as usual, this time planning on a battery "tera factory" to ramp up production of three or more lithium chemistries. His current goal is to drive at least one of them below $60/kwh. We shall see... Last edited by jeff5may; 02-08-21 at 02:49 AM.. Reason: Spell check

05-20-18, 07:25 PM	#2
oil pan 4 Land owner Join Date: Nov 2012 Location: NM Posts: 1,026 Thanks: 12 Thanked 127 Times in 107 Posts	Sounds like an Edison cell. $300 per KwH is astounding. If I wanted to make 1 KwH out of LiFePO4 cells it would cost some where around $1,000 with the lowest price I have ever seen on 20AH prizmatic cells. That's just for the cells, not hooking them up or including the enclosure.