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heeton

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.

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> ~100KWh lithium batteries are around the $20-30k. (Used Tesla pack for reference)

Nitpick: that seems high, and probably very specific to high capacity Model S packs. A brand new 75kWh Tesla pack for a Model 3 is around $10K installed these days.

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.

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.

>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.

Every other year, (solar-)electric cars scratch-built by high school students drive on public roads from Texas to (usually) California. This is considered a reasonable level of challenge, and something which insurers will cover (entrants are required to have vehicle liability insurance).

https://www.solarcarchallenge.org/challenge/about.shtml

https://www.solarcarchallenge.org/challenge/docs/rules2023.p...

Or from Darwin to Adelaide in Austrlia, where they have road trains to contend with. DIYing cars is very doable.

And you would daily drive one of those?

You would be ok getting into an accident with one the same as you would get in an accident driving a civic?

Or maybe those are just learning vehicles meant to teach, and not meant to be car replacements? Just like this flow battery project?

Ironically your post validates my whole point: This is a student project at best, and likely worthless as a "democratization of energy storage". The same way those EV's would never be considered "democratization of EV cars".

C'mon...

I take your criticism, but as for your comment that it's "a student project at best"... we do have PhDs (mine in flow batteries !) and manage this project in our spare time, at our homes...

Our small team is fully qualified to work at any flow battery company. Just give us some time and let us work on it full-time for a bit (which will happen soon). The linked post on top was a blogpost I cranked out in a few minutes one night, not something I ever expected to be on HN.

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