A common criticism of renewable energy is its reliance on weather. Now the hunt is on for an affordable battery that allows energy to be stored for rainy days. Looking at an old technology in a new way, might be the answer.
“Batteries are a natural solution,” says Professor Thomas Maschmeyer. “They are a near instantaneous buffer, and they could enable much more renewable power to be deployed into the grid when needed.”
What Maschmeyer is talking about here isn’t traditional solid state batteries, which can’t work on the scale that’s needed, cheaply enough. He’s talking about his new battery concept built around existing zinc bromine chemistry. Though this chemistry also presented a major problem.
“Elemental bromine is dangerous,” he says. “You really don’t want to inhale its vapours, and if you put your finger in bromine liquid, it will dissolve your skin. However, this chemical translates powerfully into batteries, which is very attractive.”
Maschmeyer could have looked for a new battery chemistry to side-step the problem. Instead, he thought differently about the zinc-bromine battery and realised that it could still hold the answer.
Zinc-bromine batteries are what’s called flow batteries and hold their energy in electrolyte solutions, unlike the more familiar solid state batteries which use metal electrodes. This often makes flow batteries non-portable, inflexible and costly, so they’re mostly used for niche applications like powering army bases.
Maschmeyer found a way to make flow batteries more like solid state batteries by working at the nanoscale.
“We’ve been able to encapsulate that bromine in a nano-gel in such a way that it is still chemically aggressive,” he says. “But now I can put my finger into the gel and I just have to rinse it off to remain perfectly fine – we tamed the tiger.”
The reason so much work is being done on a new generation of batteries is simple – renewable energy is yet to fulfil its full potential.
Currently, any renewable energy supply needs backup for the times when ‘the wind doesn’t blow and sun doesn’t shine’. That back-up might be environmentally unfriendly, such as carbon dioxide generating gas turbines or oil and coalfired power plants.
Maschmeyer has created a single, versatile, battery cell that can be assembled into modules in the sizes needed; small for use in solar street lights, or very large for powering communities.
To take the battery idea forward, Gelion Technologies was formed in 2015 as a spin-off from the University of Sydney, but much of the supporting work still happens in the School of Chemistry. The technology is now in the commercial prototype phase with demonstration products being released throughout 2019 and with mass-production expected to start in 2020/21.
An example of how this technology will change things is in the building industry. Maschmeyer’s zinc-bromine batteries have fire retardant qualities, which developers are already looking at integrating into the fabric of buildings. By connecting them to solar cells on the roof, residential, commercial and industrial buildings would become more energy independent.
This will take renewables to the next level and revolutionise how we all consume energy.
Maschmeyer himself, has a further ambition for his technology, “By pairing a compact solar cell with a zinc-bromine battery, millions of people who now don’t have access to electricity at all could live different lives. For me, that’s very motivating.”
Lithium battery costs compared to the cheaper zinc-bromine alternative
Degree temperature resistance for zinc-bromine