Systems engineering and modeling

[sepi]

Hey all! If everything goes well, we'll soon have a bit bigger cell and maybe cell stack to play with. This will be another step towards building an actually useful energy storage. This also means that overall systems efficiency starts becoming an important issue. In order to know what to focus on in the development but also to understand questions of dimensioning and parts selection, it would make sense to be able to model the whole RFB system including Pumps, Inverters, plumbing and cell and its chemistry.

Did anyone look into this already? I was exploring a bit what tools we could use and figured that Libreoffice Calc would be the very simplest tool, followed by python with SymPy and finally by OpenModelica. What do you think? Is this the right time to think about these things or am I overthinking it?

[danielfp248]

@sepi Thanks for opening up the thread! These are all important things to look at, but to do this successfully we first need to have at least the system well defined (meaning at least the components would be sort of already decided). At this point of the large cell format we are still within the initial implementation phase, so things that are critical to efficiency such as shunt currents, flow rates, pump models to be used, etc, are all still up for debate. You are of course welcome to give it a shot with the current configuration, but bear in mind that it is likely to change significantly before we have something steady. I have no experience with the modeling of battery stacks, so perhaps @kirk might be more helpful.

[sepi]

I've looked a bit into modeling of RFBs and found this hopefully interesting article giving a nice overview to different modeling approaches for Vanadium RFBs. https://www.sciencedirect.com/science/article/abs/pii/S2352152X22021806

[muntasirms]

Hey @sepi take a look at Bert Neyhouse's spreadsheet cycling models (https://www.bertrand-neyhouse.com/rfb-models). They might not include stack-scale calculations you're looking for though. If you're interested in more of an economic analysis vs. nitty gritty engineering design let me know.

[sepi]

@muntasirms very interesting. I'm indeed looking for the most basic models I can find to get started. Thanks for the pointer.

[sepi]

Garh, unfortunately I can't read either the Neyhouse paper nor the one I posted sonce I don't have a subscription. Sci-hub and annas-archive also fail me here.

[kirk]

@muntasirms @sepi PNNL have done a model which includes a Zn-I example system: https://github.com/pnnl/EZBattery/tree/master

Eric Fell also has a 0D model: https://github.com/ericfell/rfbzero, https://joss.theoj.org/papers/10.21105/joss.06537.pdf

I think these could both be good starting points, the former especially for considering the issues @sepi raised in the first post, the latter for understanding more the fundamentals of these systems.

[kirk]

@sepi said in Systems engineering and modeling:

Garh, unfortunately I can't read either the Neyhouse paper nor the one I posted sonce I don't have a subscription. Sci-hub and annas-archive also fail me here.

I am an ECS member (who runs the journal it's in) and even I can't get the article I'll ask around, I'm sure we can find a copy

[muntasirms]

@kirk @sepi I think Bert's models are free to download off his site, but if you wanted to read the paper, I'm happy to email them to you or you can reach out to him for a copy.