Tenfold improvement in liquid batteries mean electric car refuelling could take minutesdiscovered that if we made an electrolyte out of a very high concentration of a metal oxide, it was able to absorb much more charge than we expected. The result was a flow battery with roughly ten times more energy density than had previously been achieved – 225 watt-hours per litre, with the possibility of up to 1,000 watt-hours per litre. I suddenly realised that with this energy density, application to vehicles could be possible.’
‘A flow battery can produce a lot of power – you get more bang for your buck .’ – Professor Lee Cronin, University of Glasgow, UK.How does the performance compare with the current batteries inside electric vehicles? ‘A Tesla Model 3, for example, has a 70 kilowatt-hour battery. To have the same capacity as that, we would need at least 70 litres of the best version of our battery – that’s around the same size as the fuel tank in a petrol car.’ How hard would this be to implement in practice? ‘There is no reason why a flow battery could not be retrofitted into an existing electric vehicle, provided it generates the same output and takes up the same space. Meanwhile, all the petrol stations in the world have pumps, and are used to handling liquids, so a lot of the infrastructure is already there. The liquids we’re using are corrosive, but it is possible to consider retrofitting piping to cope with this. Perhaps the storage tanks would have to be upgraded, but upgrading something is a lot cheaper than building entirely new infrastructure. The major benefit is that our electrolytes are green – the depleted ones can be recharged, hopefully using renewable electricity, and given to the next customer.’ What’s stopping us from doing this right now? ‘There’s a lot of engineering to be done, to make sure that it can work safely and reliably. Currently, we’re transferring our knowledge from the laboratory to a test rig, and developing a prototype. We want to check that we’re getting the energy densities we expect, and that the mechanics of the pumping works. If I had all the money, I could imagine three steps: build a prototype to validate all the workings and optimise efficiency, build another for use in a stationary application, and finally bung it in a car. ‘I’m hoping that other people will now adopt this idea, and treat it seriously because of the increased energy density. Big companies from around the world have already got in contact, and I’ve just got to work out the best course of action. I’m a university professor, so my job is to understand how the universe works, but I’m not afraid to do some engineering if there’s the potential to solve a massive problem, if the funding for the vision was available.’ The research in this article was funded by the EU’s European Research Council. If you liked this article, please consider sharing it on social media. Originally published at Horizon.