Flow batteries are rechargeable devices based on specific chemicals in liquids separated by a membrane.  They hold the key to cheap energy storage, especially if their dependence on expensive metals such as platinum and vanadium is reduced. Enter organic compounds called quinones.  Quinones are central to electron transport in photosynthesis (plastoquinone, phylloquinone), and aerobic respiration (ubiquinone). A discovery by Harvard biochemists suggests that quinones similar to those found in rhubarb may unlock the development of cheap flow batteries.

Marc Howe. Jan 20, 2014.  Sourceable.  The new technology, developed by a team of scientists and engineers from Harvard University, is an organic flow battery which eschews the use of expensive metals, turning instead to carbon-based molecules called quinones which are cheap and naturally abundant.

Flow batteries involve the storage of energy in chemical fluids which are sited in external tanks outside the casing of the battery itself. The external position of the tanks enables them to be scaled up independently of the electrochemical conversion hardware, which means their storage capacity is restricted solely by their size.

It is this scalable storage capacity which makes them a potential game-changer for climate-dependent forms of clean energy. The chief shortcoming of wind and solar power is their lack of consistent output due to reliance upon fickle weather conditions.

Advanced storage capacity could alleviate this shortcoming by permitting the storage of excess energy when generation outpaces consumption, for subsequent usage when the air is still or the sun doesn’t shine.

The chief impediment to the widespread adoption of large-scale flow batteries thus far has been the prohibitive cost of some of their component materials, such as vanadium and platinum.

The new organic flow battery developed by the Harvard team is already on par with vanadium flow batteries in terms of performance, yet is far more economical due to the fact that it not require copious use of precious metals. The quinones used in the battery are extremely easy to source, given their ready abundance in both green plants and crude oil.

Following a lengthy and exhaustive analysis of over 10,000 quinone molecules, the Harvard team eventually settled upon a molecule which is almost identical to that found in rhubarb – a fact which attests to the potential availability of raw material.

According to Roy G Gordon, Harvard’s Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science, the organic flow battery could be a paradigm-changing development in the field of energy storage.

“The whole world of electricity storage has been using metal ions in various charge states…[but] none of them can economically store massive amounts of renewable energy,” Gordon said.”With organic molecules, we introduce a vast new set of possibilities.”

The Harvard team behind the new battery technology received funding for their endeavours from the US Department of Energy’s Advanced Research Projects Agency-Energy ARPA-E), and have already published a paper on their results in the scientific journal Nature.

Plans are now underway for the commercial deployment of the technology. Connecticut-based Sustainable Innovations, LLC, who contributed to the battery’s development, hope to unveil a portable demonstration version of the battery by the end of a three-year development period, which can be connected to the solar panels of a commercial building for storage purposes.