Developing an Open-Source Battery with Inspiration from Piggott Turbines

Kirk Smith

Flow Battery Research Collective

Daniel Fernández Pinto

Flow Battery Research Collective

Josh Hauser

Utrecht University/FAIR Battery Project

Sanli Faez

Utrecht University/FAIR Battery Project

October 7, 2024

Flow Battery Research Collective: Who are we?

A brand-new community of researchers, energy storage users, and enthusiasts who want to help develop and democratize technologies for affordable, sustainable energy storage

We are trying to build an open-source battery for storing solar and wind energy.

https://fbrc.dev

What is a flow battery?

A single “unit cell” of a flow battery

Stores energy in liquid electrolyte reservoirs (more volume = more energy)
“Stack” charges/discharges electrolytes with redox reactions (more area = more power)

Scaling up

“Bipolar” graphite plates connect cells in series electrically
Fluid manifolds connect cells hydraulically in parallel

Real flow batteries

Redflow’s ZBM3, 3 kW / 10 kWh zinc-bromine flow battery [1]

Rongke Power’s 200 MW/800 MWh vanadium flow battery in Dalian [2]

Flow batteries vs. lithium-ion and lead-acid

A qualitative, non-peer-reviewed comparison - assuming all technologies were manufactured at the same economies of scale

Our roadmap

Current status: prototype benchtop cell

Exploded view of current design

Exploded view of the a prior cell design

Examples of cost-saving measures: “going from neodymium to ferrite”

Affordable membrane

2,520 EUR/m² vs. 6 EUR/m² (Ion Power GmbH and Amazon UK)

Affordable current collectors

1,477 EUR/m² vs. 66 EUR/m² (FuelCellStore and Amazon US)

No glovebox/inert gas requirements

We use a potassium acetate buffer to mitigate the effects of ambient oxygen

Apartment chemistry/prototyping

Small batch run for a workshop

More info on the workshop and cell design here: https://fbrc.dev/posts/Flow4U-conference/

The chemistry

Our initial chemistry is zinc-iodide, but we plan to explore more varieties.

Negative Terminal (Anode): \(\ce{3Zn_{(s)} -> 3 Zn^2+ + 6e-}\)
Positive Terminal (Cathode): \(\ce{2I3- + 6e- -> 6I- }\)
Overall: \(\ce{3Zn_{(s)} + 2I3- -> 3Zn^2+ + 6I-}, E^\ominus = 1.298 V\)
Parasitic reaction: \(\ce{6I- + O2 + 2 H2O -> 2I3- + 4OH- }\)

Why Zn/I?

Easy to source, low-cost reagents (vs. vanadium, for example)
Compatible with cheap microporous membranes, such as paper
Resistant to dendrites
No detectable hydrogen evolution (unlike all-iron systems)
Acceptable energy density (>20Wh/L)
No strong acids or bases needed
Low toxicity (but don’t drink it!)

Current performance: low concentration, 100 mAh/cm²

1 M \(\ce{ZnCl2}\), 2 M \(\ce{KI}\), \(\ce{KAc}\) buffer, 5 mL each side, photopaper separator, 30 mA/cm², 100 mAh/cm², over 5 days

Current performance: low concentration, 120 mAh/cm²

1 M \(\ce{ZnCl2}\), 2 M \(\ce{KI}\), \(\ce{KAc}\) buffer, 5 mL each side, photopaper separator, 30 mA/cm², 120 mAh/cm², same cell from last test, 6 days (11 total)

Current performance: medium concentration, initial cycles

2 M \(\ce{ZnCl2}\), 4 M \(\ce{KI}\), \(\ce{KAc}\) buffer, 5 mL each side, photopaper separator, 30 mA/cm², 120 mAh/cm²

What can we learn from Piggott turbines and the Wind Empowerment network?

What can we do similarly?

Engage both academics and technology practioners, ie. people who install batteries for off-grid and wind/solar setups
Fund development with grants, educational workshops
Embrace open-source, knowledge sharing, community-guided approach

Possible challenges/differences:

Battery tech can require more specialized materials than small wind turbines (SWTs)
Harder to DIY individual, residential-scale batteries, compared to SWTs
- need for low or mid-scale manufacturing, unlike community Piggott builds
- could be possible in hackerspace/makerspaces?
We are much earlier on our journey!

You can get involved!

Tell us what you’d need in a battery for small wind turbine applications!

What voltage?
How many kW and kWh?
What efficiency?
Size, weight, safety constraints

We just set up a forum at https://fbrc.discourse.group/

Acknowledgements

Josh Hauser, Sanli Faez & FAIR Battery team
Daniel Fernández Pinto, chief chemist
Conference organizers!
NLnet’s NGI0 Entrust fund