Kirk Smith and Colleagues Aim to "Democratize Flow Batteries" with an Open Source Development Kit

Scientist Kirk Smith has shared fresh details on an ongoing effort to "democratize flow batteries" — with the creation and release of a development kit for an open source battery, tailored for the capture and storage of renewable energy.

"There's not really a great option for an open-source battery," Smith explains of the inspiration behind the project. "And even if there was an open-source lithium battery, you'd probably need a billion dollars to set up a factory to produce it according to the requirements. That's why I'm working primarily on water-based batteries, particularly flow batteries. We started a project called the Flow Battery Research Collective. We've already made a development kit that lets us test different flow battery chemistries at a two-centimeter scale, and we're in the process of testing different chemistries in this kit and then trying to scale it up."

The current boom in renewables means it's possible to build systems for harvesting solar, wind, and other forms of energy at a very low cost — and much of the hardware in a commercial energy harvesting system can be replicated using open source equivalents. That's not true of the battery, however, and an energy-harvesting system with no battery is unable to store energy from peak harvesting times for use at peak consumption times, making it considerably less effective.

Smith and colleagues' efforts, then, aim to bridge this gap. Where commercial systems use ltihium-ion, lithium-polymer, or lithium-iron-phosphate (LiFePO₄) batteries, the Flow Battery Research Collective is concentrating its efforts on chemistries and production techniques which are easier to work with using hobbyist-level technology. "A flow battery is just a battery that has forced convection, or flowing liquid," Smith explains. "A flow battery will generally always have one pump for the positive side, one pump for the negative side, one reservoir tank for the positive side, one reservoir tank for the negative side, and then the actual electrochemical cell where you make the connections and where the reactions happen."

"[For] all the parts we try to maximize laser cutting, vinyl cutting, 3D printing, FDM [Fused Deposition Modeling, also known as Fused Filament Fabrication] when possible, and eventually you probably have to have injection and mold things, but for now we're trying to make it as accessible as possible," Smith continues. "We are quite picky on the chemistries that we work with because we want to make sure that they're relatively safe and accessible in many places. So, this rules out vanadium flow batteries: vanadium's pretty toxic, it's actually hard to get, and pretty expensive because the price is controlled by the steel industry. We're focused on electrolytes where we're plating metallic iron and/or zinc on the negative side, so they're hybrid [batteries]."

The team's development kit is open hardware, and makes it possible to experiment with different chemistries on a small scale. It's not all about experimental cells, though: Smith and colleagues have already built some larger-scale batteries based on their testing, going from 2cm² in testing to 175cm² to prove the design. More information is available on the project website, with design files and source code available on Codeberg under the strongly reciprocal variant of the CERN Open Hardware License.