Is this the Holy Grail of home energy storage for DIYers?
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Korishan
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Interesting idea. Definitely something where the batteries would need to be stable and not moving around. I would guess (still reading comments, and maybe watch a few other vids) that the solution when charged shouldn't be moved around. Altho, one of the commenters brought out that it is very similar to the way RedFlow works, which is a flow battery using ZnBr as well. But as Rob mentions, it has other agents in the solution.
One thing I wonder though is what the capacity of these batteries are. He didn't mention that in this video even though he had one on the bench he'd been charging. This is where the problems, feasibility, economics and scalability will come into play. If the battery he made on camera can only hold 1000mAh, then you'd need an awful lot of these to make them work for a house storage.
In a comment it is stated that the capacity is directly related to the amount of Zinc in solution. I suppose the more zinc you put into solution the higher the capacity. However, how much capacity is there in saturation?
Now if you have large amount of space (like several acres of land) then I think this idea would work great. I say this as it gives plenty of space to work with as you would could only build Up so far. I would imagine you would also need to keep an eye on solution levels, similar to Lead Acids, unless you could seal the containers good enough. But would need a vent hole for safety measures. This can still create acids if charged to fast, so those measures would need to be taken into account as well.
Because they must be charged at low amps, this is another reason for "many" of them, as you would need to be able to charge the bank at full amperage of your energy generators. He states that for each cell, they can only be charged at <100mA for best results. This is what we do with Lithium based cells here. However, they are "much" smaller compared.
One thing I wonder though is what the capacity of these batteries are. He didn't mention that in this video even though he had one on the bench he'd been charging. This is where the problems, feasibility, economics and scalability will come into play. If the battery he made on camera can only hold 1000mAh, then you'd need an awful lot of these to make them work for a house storage.
In a comment it is stated that the capacity is directly related to the amount of Zinc in solution. I suppose the more zinc you put into solution the higher the capacity. However, how much capacity is there in saturation?
Now if you have large amount of space (like several acres of land) then I think this idea would work great. I say this as it gives plenty of space to work with as you would could only build Up so far. I would imagine you would also need to keep an eye on solution levels, similar to Lead Acids, unless you could seal the containers good enough. But would need a vent hole for safety measures. This can still create acids if charged to fast, so those measures would need to be taken into account as well.
Because they must be charged at low amps, this is another reason for "many" of them, as you would need to be able to charge the bank at full amperage of your energy generators. He states that for each cell, they can only be charged at <100mA for best results. This is what we do with Lithium based cells here. However, they are "much" smaller compared.
OffGridInTheCity
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vspin said:
Its an interesting watch but... I didn't hear come away with the *key* info I was looking for- e.g. voltage, amps, and power of the example battery. Maybe I missed it? He alluded that a few amps discharge can be expected but wasn't clear what size of cell he was thinking of. He mentioned voltage going up/down/up during charging but didn't give an values or length of time.
Korishan
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OffGridInTheCity said:
You have to dig further down into the comments to get those answers.
Voltage is 1.85V per cell
Amps are based on surface area. He mentions that folding the electrode will give higher amp yields (I imagine like an air filter with all those folds)
Capacity is based on the amount of Zinc in solution
Charge rate is about 100-300mA. I'm guessing that is based on surface area, as well, but not sure
Discharge rate is around 1A
Each cell must be separate from another electrolyte wise. So you can't stack multiple plates in the same solution, like that of Pb batts.
OffGridInTheCity
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Did you get a sense of the overall power density or more specifically a reasonable estimate of thepower in thedemo battery?Korishan said:
For example, a discharge of 1.8v@1a = 1.8watts per cell - which would be 1.8whper hour. A 2000mah 18650 cell has 7.4wh. The sample battery would need to run (7.4wh/1.8wh) =4.1 hours be in the range of the power of a 2000mah18650 cell.
Korishan
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OffGridInTheCity said:
True, I agree. The power density is only a fraction of that of Lithium based chemistries. However, there is a price difference. As I stated earlier, unless you have the space for these, they aren't really feasible. You'd need a lot of shelf space. The advantages would be that it's super safe, no explosions. It's super easy to build and cheap. It'd be a great system for those who are out in the middle of nowhere (forest dwellers for example) because of the space requirements.
When I get the garage done, I may try building some of these myself to see how easy and reliable they are.
Could you imagine having a solar farm, and under all the panels are banks of these cells? Have the solar panel connected to the batteries through an mppt charger, then connect the batteries to the main line heading to the main storage and/or inverter.
OffGridInTheCity
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Just saw the latest youtube -
- where he made 'solid' battery cells with same chemistry of the liquid ones and stacked 7 of them for 7 * 1..85 = 12.95v. He also said they (each cell) has about 4.5w.. which is 2432mAh. That sounds fantastic.. as that's not that far from an ordinary 18650 cell and only 2-3 times larger for same power - certainly 'in range' of practicality in my view. Of course we don't know the cycle(s) etc... but still.....
I must say - it looked pretty impressive!
I must say - it looked pretty impressive!
Bubba said:
According to the Optimization and Design of ..., the estimated cost of Zinc Bromide is $2.3 to $3.1 per kg but I image the estimates are based on buying in large volume, and does not include other costs such as shipping. I don't know where you can purchase it in NA but you can get it in bulk on Alibaba.Robert Murray-Smith is going to be making a video on how to make zinc bromide electrolyte yourself but I wonder how cost effective that would be.
What's really important when building these cells is "$ per kWh over its lifetime (number of cycles) at a given energy efficiency," before going large scale.
OffGridInTheCity said:
It does! I would LOVE to see his cell analyzed with abattery analyzer/cycler. The cell he made is different from the initial, and optimized versions that were created by Princeton University.
Korishan
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Bromine is more expensive, correct. It's easily obtained from Pool/Spa stores as it's used as a Chlorine replacement in spa/hot-tub sanitizing because it's stable at higher temps. But, this is mostly BromoChloro-5, or basically Bromine and Chlorine bonded together. Probably wouldn't be able to use it without having to process it first.
However, you can get Bromine Water, which is Br2 dissolved in water
https://www.labsupplyoutlaws.com/chemicals-and-reagents/bromine-water-saturated-c2180-500ml.htm
This costs $125USD
Not sure how much of this solution you'd need, though, to make the batteries.
However, you can get Bromine Water, which is Br2 dissolved in water
https://www.labsupplyoutlaws.com/chemicals-and-reagents/bromine-water-saturated-c2180-500ml.htm
This costs $125USD
Not sure how much of this solution you'd need, though, to make the batteries.
I just thought of something! The levelized cost of energy stored (LCOES) for the minimal architecture zincbromine battery is considerablyless than the other batteries. But it's even better than that for DIYers. DIYers can reuse components, such as the case, terminals, and electrolyte too (so I read). If you design your cell right, you should be able to open it up (after discharging), and remove and replace the electrodes, and maybe make some adjustments to the electrolyte.
Edit: Cell size should be taken into consideration too. If the cell is small, the cost to replace a single cell's electrodes is cheap, but when you need to replace many or all of your cell's electrodes, you'll have a lot of work. If the cells are larger, replacing many or all your cell's electrodes will be less time consuming, but you'll spend more money when you need to replace a single cell's electrodes.
Edit: Cell size should be taken into consideration too. If the cell is small, the cost to replace a single cell's electrodes is cheap, but when you need to replace many or all of your cell's electrodes, you'll have a lot of work. If the cells are larger, replacing many or all your cell's electrodes will be less time consuming, but you'll spend more money when you need to replace a single cell's electrodes.
not2bme
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Sounds like it's not new science, so it must have its downsides. From looking at the video briefly, I can see determining full charge is based on a 'dip' so a cc/cv charging is not possible. If this was viable and affordable then it would have made it mainstream. Who knows it might, if there's a way to do it. It's akin to the edison battery, which I think would be easier to build and source diy. Nickel and iron would be the metals and potassium hydroxide which is a semi-common food or soap making powder.
I've compiled a list of design / operating suggestions from the comment section of Robert's video, and from what I've learned from reading the research papers, and other sources. I also explain how to create a carbon foam electrode (CFE), and point out the cost for materials in order to reach the projected levelized cost of storage (LCOS).
Cell Design Suggestions
a. Space top and bottom electrodes 0.4 cm apart. This was determined to be optimal spacing, according to Princeton's research.
b. Use 1.0 M ZnBr2 electrolyte. Despite Robert's comment of 1.75 M ZnBr2 electrolyte, 1.0 M was in factdetermined to beoptimal in terms of the lowest LCOS, according to Princeton's research.
c.DoNOTuse a supporting salt to reduce resistivity, despite Robert using 1 M ofsodium sulfate. Princeton tested supporting salts (includingsodium sulfate), and found that the best supporting salt (sodium chloride) decreased performance significantly as it created high levels of hydrogen.
d. Use a carbon foam electrode (positive), opposed to the carbon feltelectrode in Robert's cell. Doing so produces greater coulombic efficiencies, resulting in as much as 10% greater energy efficiency, according to Princeton's research. Note that a carbon foam electrode which is hollow on the inside (shell) will hypothetically increase cell capacity, according to Princeton. However, this makes the production of CFEs more complex, opposed to a solid foam piece.
e. Use a carbon cloth electrode (negative). Both zinc and titanium (having good resistance to the electrolyte) negative electrodeswere tested, however, their outputs were unstable opposed to the carbon cloth. Princeton also stated that to improve cell performance that they began"double-bussing" the[size=medium]carbon cloth. I think that means doubling up on the carbon cloth..?[/size]
f. Both carbon electrodes should have aluminium (affordable) current collectors coated in carbonto protect them from the electrolyte. This is just my opinion.
g. Invert electrodes (positive on top, negative on bottom), opposed to Robert's design. Princeton's exemplary battery design inverted the electrodes. By doing this, the top carbon foam electrode reacts with the hydrogen as it bubbles to the top, and redissolves it back into the solution, "thus recapturing any potential losses."
h. For a 48V battery, 30 cells in series may be optimal. The Redflow ZBM2 Battery (a zinc-bromine flow battery) has a operating range of 40-57V, and has 30 cells in series. I imagine this is for good reason [size=medium](for inverters/charge controllers?).[/size]
i. Shorter charge/discharge times (e.g., 4-hours, 8-hours, 12-hours) offer the lowest LCOS because shorter cycles allow more cycles during its lifetime, and there are lower self-discharge rates per cycle, according to P[size=medium]rinceton's research.[/size]
How to make a carbon foam electrode (general information)
To make 1 kg of carbon foam material, combine 425 g of carbon black (powder?) with 425 g of graphite[size=medium](powder?). Next, create asolution of polyvinylidene difluoride (PVDF) in N-Methyl-2-pyrrolidone (NMP). NPM can be found on ebay. It used to be a common paint stripper. Properly mix a solution of 150 g of PVDF with 2.85 kg of NPM with a magnetic hotplate with a lid on the glass beaker. Pour the solution in with the carbon mixture, and mix to create a carbon slurry. Pour the slurry into a mold(s) to create your desired shape and sizeCFE.[/size]
Princeton's CFE was cylindrical. They created a 3D printed retractable piston to compress the slurry down in the mold using a hydraulic press to ~1 psig. With a littleingenuity,you should be able to compact the slurry @ ~1 psig without a hydraulic press.
Finally, put the mold(s) in a vacuum oven, and baked for 8 hr at 130 C, evaporating the NMP and leaving behind a porous but rigid carbon foam.Time and temperature may vary depending on the size and shape of your CFE.I estimate the weight of the large cylindrical CFEwhich Princeton created to be around ~24.5 g when calculating your oven temperature and time.
[size=medium]Warning:[size=medium]N-Methyl-2-pyrrolidone (NMP) is not safe. Research it first. Never allow NPM to contact your skin or eyes, and avoidinhalation, using excellent ventilation.[/size][/size]
**Cost of materials to reach the projected LCOS (according to Princeton)
Plastic (HDPE or PTFE) cell case: $0.22 - $0.37 per liter (volume within case)
Zinc bromide (anhydrous): $2.30 - $3.10 per kilogram
Carbon foam electrode: $5.70 - $11.20 per kilogram
*Carbon cloth and Titanium current collector: $13.10 - $19.10 per square meter
* Note that this cost is bundled, and the the titanium current collector was used on the positive electrode. A more affordable solution may be to use aluminium current collectors coated in carbon to protect it from the electrolyte.Although, maybe titanium alone is the more affordable solution, as it has good chemical resistance to the electrolyte, and therefor may not need to be coated in carbon (or plastic).
** Note that to reach these figures you're most likely looking for technical (industrial) grade materials, or battery grade. Avoid expensive laboratory and reagent grades.
Cell Design Suggestions
a. Space top and bottom electrodes 0.4 cm apart. This was determined to be optimal spacing, according to Princeton's research.
b. Use 1.0 M ZnBr2 electrolyte. Despite Robert's comment of 1.75 M ZnBr2 electrolyte, 1.0 M was in factdetermined to beoptimal in terms of the lowest LCOS, according to Princeton's research.
c.DoNOTuse a supporting salt to reduce resistivity, despite Robert using 1 M ofsodium sulfate. Princeton tested supporting salts (includingsodium sulfate), and found that the best supporting salt (sodium chloride) decreased performance significantly as it created high levels of hydrogen.
d. Use a carbon foam electrode (positive), opposed to the carbon feltelectrode in Robert's cell. Doing so produces greater coulombic efficiencies, resulting in as much as 10% greater energy efficiency, according to Princeton's research. Note that a carbon foam electrode which is hollow on the inside (shell) will hypothetically increase cell capacity, according to Princeton. However, this makes the production of CFEs more complex, opposed to a solid foam piece.
e. Use a carbon cloth electrode (negative). Both zinc and titanium (having good resistance to the electrolyte) negative electrodeswere tested, however, their outputs were unstable opposed to the carbon cloth. Princeton also stated that to improve cell performance that they began"double-bussing" the[size=medium]carbon cloth. I think that means doubling up on the carbon cloth..?[/size]
f. Both carbon electrodes should have aluminium (affordable) current collectors coated in carbonto protect them from the electrolyte. This is just my opinion.
g. Invert electrodes (positive on top, negative on bottom), opposed to Robert's design. Princeton's exemplary battery design inverted the electrodes. By doing this, the top carbon foam electrode reacts with the hydrogen as it bubbles to the top, and redissolves it back into the solution, "thus recapturing any potential losses."
h. For a 48V battery, 30 cells in series may be optimal. The Redflow ZBM2 Battery (a zinc-bromine flow battery) has a operating range of 40-57V, and has 30 cells in series. I imagine this is for good reason [size=medium](for inverters/charge controllers?).[/size]
i. Shorter charge/discharge times (e.g., 4-hours, 8-hours, 12-hours) offer the lowest LCOS because shorter cycles allow more cycles during its lifetime, and there are lower self-discharge rates per cycle, according to P[size=medium]rinceton's research.[/size]
How to make a carbon foam electrode (general information)
To make 1 kg of carbon foam material, combine 425 g of carbon black (powder?) with 425 g of graphite[size=medium](powder?). Next, create asolution of polyvinylidene difluoride (PVDF) in N-Methyl-2-pyrrolidone (NMP). NPM can be found on ebay. It used to be a common paint stripper. Properly mix a solution of 150 g of PVDF with 2.85 kg of NPM with a magnetic hotplate with a lid on the glass beaker. Pour the solution in with the carbon mixture, and mix to create a carbon slurry. Pour the slurry into a mold(s) to create your desired shape and sizeCFE.[/size]
Princeton's CFE was cylindrical. They created a 3D printed retractable piston to compress the slurry down in the mold using a hydraulic press to ~1 psig. With a littleingenuity,you should be able to compact the slurry @ ~1 psig without a hydraulic press.
Finally, put the mold(s) in a vacuum oven, and baked for 8 hr at 130 C, evaporating the NMP and leaving behind a porous but rigid carbon foam.Time and temperature may vary depending on the size and shape of your CFE.I estimate the weight of the large cylindrical CFEwhich Princeton created to be around ~24.5 g when calculating your oven temperature and time.
[size=medium]Warning:[size=medium]N-Methyl-2-pyrrolidone (NMP) is not safe. Research it first. Never allow NPM to contact your skin or eyes, and avoidinhalation, using excellent ventilation.[/size][/size]
**Cost of materials to reach the projected LCOS (according to Princeton)
Plastic (HDPE or PTFE) cell case: $0.22 - $0.37 per liter (volume within case)
Zinc bromide (anhydrous): $2.30 - $3.10 per kilogram
Carbon foam electrode: $5.70 - $11.20 per kilogram
*Carbon cloth and Titanium current collector: $13.10 - $19.10 per square meter
* Note that this cost is bundled, and the the titanium current collector was used on the positive electrode. A more affordable solution may be to use aluminium current collectors coated in carbon to protect it from the electrolyte.
** Note that to reach these figures you're most likely looking for technical (industrial) grade materials, or battery grade. Avoid expensive laboratory and reagent grades.
Bubba
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vspin said:
Do you know where those prices may be found for example the Zinc Bromide. Here in Canada I could almost buy a car for the price of a 1kg.
Also being Anhydrous how are many of the companies storing it in paper bags or cardboard containers etc?
Bubba said:
Honestly, I don't know why it would be stored in paper bags or cardboard unless lined with plastic. I would expect in the very least that it was stored in plastic (zinc bromide resistant) bags.I think you will have to purchase from China (Alibaba).
EDIT -Here is zinc bromide (99%+ purity)at $1.00 per kg which requires a minimum 10 kg order:
https://www.alibaba.com/product-detail/Hot-selling-high-quality-Zinc-bromide_60769773748.html
I don't know how accurate, or current the listings is, and whether or not the supplier is reputable, however, this Gold supplier has a highResponse Rate, and number Transactions. You can find other substances on there as well (e.g.,battery grade carbon black and graphite).
You can also purchase samples (sometimes free, if you pay for shipping) from some suppliers. This may be a great option if you only need a small amount.
100kwh-hunter
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They cheapest i could find is the one used at oil rigs for drilling, but its not very pure ~70%
For school projects i could buy some but at a very high cost.
To make zinc bromide myself, to time consuming.
I sended a email to two chem suppliers(they only deliver to resellers or big quantities to companies) here in the Netherlands.
No shots fired = always a miss.
I suspect the rest of the ingredients is going to be way easier.
Overall it sound like a fun project.
@vspin,
I ordered two times via alibaba direct from factories/mines.
one time not even a shipment the other time 50% pure instead of 99%.
Both orders was for antimony and bismuth.
I don't say this one is bad, perhaps i am even going to try
For school projects i could buy some but at a very high cost.
To make zinc bromide myself, to time consuming.
I sended a email to two chem suppliers(they only deliver to resellers or big quantities to companies) here in the Netherlands.
No shots fired = always a miss.
I suspect the rest of the ingredients is going to be way easier.
Overall it sound like a fun project.
@vspin,
I ordered two times via alibaba direct from factories/mines.
one time not even a shipment the other time 50% pure instead of 99%.
Both orders was for antimony and bismuth.
I don't say this one is bad, perhaps i am even going to try
100kwh-hunter said:
Indeed, doing business with China is painful, but necessary to keep costs low. Although a supplier can bait (with sample) and switch (with large purchase), I recommend that you get samples first before investing a lot of money, and that you look for:
1. Orders with Trade Assurance. Make certain that purity is disclosed in your order.
2. Suppliers with high response rates.
3. High number of transactions.
4. Rated high with several years in business.
Korishan said:
According to Sciencing, there are four methods:
- A visual (and taste, if edible), physical comparison with a "certified" pure sample.
- By comparing the melting and boiling points of the substance with the pure substance.
- Colorimetric method which introduces a chemical(s) to turn the impurities a certain color. This method is "designed to determine the presence of impurities, not to determine the amount or the percent purity of the substance."
- The analytical method (most accurate method) "mostly involves chemical analysis, which can pinpoint the presence, identity and amount of impurities in the sample."
Edit: I suppose you were actually looking for specifics for the listed items, opposed to general methods.
Edit: [incorrect content removed]
100kwh-hunter
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100kwh-hunter
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Good morning.
For so far my reading and understanding of his video's goes:
They are very simple to make.
Chemicals are (theoretically) easy and cheap to purchase.
A cell with dimensions of 10x10x2.5cm or 4x4x1 inch, will give you ~1.85v and ~2000mah storage max.
Side note: its 100cm2 / 15,5inch2, will give ~2000mah
Length and width of your cell candependand varion the width of your purchased material.
The max storage capacityis also depending on the chemicals you are using (and filler, solidifying agents)
It is possible to make a "dry" maintenance free (gel like) cell.
But the cathode and the anode must be at the top and bottom. Not at the sides, not even if you would use filler and a solid gel electrolyte(zinc bromine based).
There are claims that those cells could have 10.000!! cycles.
If you would stack them on top of each other(connected with graphite sheets in between) you can stack them up to max 7 pieces ~12v.
Put a supporting case around it and continue stacking.
For a 48v @ 2ah cell it would be 4x4 by 20-25 inch high/10x10cm by 50-60 cm high.
For a 48v @ 200Ah = 1550 inch2 / 1m2
For comparison lifepo 48v@200Ah you would need: 550 inch2 / 0.36m2
Lifepo is roughly one third at surface area and half the height.
And 3 times more life.
So far, so good.
What I think what is the real problem is that charge/discharge vs storage ratio. 1 to 10
To charge or discharge with 10a you would need 100a of storage
Lets see if i can get all the materials needed and give it a go.
Word of advice: check your country's laws regarding those chemicals and diy ess.
Any thoughts? Thanks in advance.
For so far my reading and understanding of his video's goes:
They are very simple to make.
Chemicals are (theoretically) easy and cheap to purchase.
A cell with dimensions of 10x10x2.5cm or 4x4x1 inch, will give you ~1.85v and ~2000mah storage max.
Side note: its 100cm2 / 15,5inch2, will give ~2000mah
Length and width of your cell candependand varion the width of your purchased material.
The max storage capacityis also depending on the chemicals you are using (and filler, solidifying agents)
It is possible to make a "dry" maintenance free (gel like) cell.
But the cathode and the anode must be at the top and bottom. Not at the sides, not even if you would use filler and a solid gel electrolyte(zinc bromine based).
There are claims that those cells could have 10.000!! cycles.
If you would stack them on top of each other(connected with graphite sheets in between) you can stack them up to max 7 pieces ~12v.
Put a supporting case around it and continue stacking.
For a 48v @ 2ah cell it would be 4x4 by 20-25 inch high/10x10cm by 50-60 cm high.
For a 48v @ 200Ah = 1550 inch2 / 1m2
For comparison lifepo 48v@200Ah you would need: 550 inch2 / 0.36m2
Lifepo is roughly one third at surface area and half the height.
And 3 times more life.
So far, so good.
What I think what is the real problem is that charge/discharge vs storage ratio. 1 to 10
To charge or discharge with 10a you would need 100a of storage
Lets see if i can get all the materials needed and give it a go.
Word of advice: check your country's laws regarding those chemicals and diy ess.
Any thoughts? Thanks in advance.