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Thursday, 27 July 2017

Energy Frontiers; Flow batteries coming into their own!

With the world gradually moving towards renewables the downside of intermittent power is proving a real problem. No country can afford to have its industry and population at the whim of the sun and the wind. So it is not surprising that energy storage is receiving increasing scrutiny. Indeed the purported solution to SA's blackout dilemma is, in part at least, a 100 MW Tesla battery bank, the largest in the world. While the jury is out on how such a small addition of back-up power can avoid blackouts in SA, inevitably energy storage will become a must-have adjunct for any viable renewable energy installation. 

Storage can take many forms; pumped hydro (as per the proposed Snowy 2.0), compressed air, flywheels and of course chemical storage in the form of batteries . While the high energy density and ready availability of Lithium- ion batteries has given them the lead in battery storage solutions, many novel technologies are under development.

One such technology the 'Flow battery' has taken a giant step with Germany installing a pilot plant on a grand scale. In the article titled  "German energy company wants to build flow batteries in old natural gas caverns", Megan Geuss of Ars Tecnica explained;

"A German energy company (EWE GASSPEICHER GmbH) recently announced that it’s partnering with a university to build a massive flow battery in underground salt caverns that are currently used to store natural gas. The grid-tied battery, the company says, would be able to power Berlin for an hour."
I don't want to get too technical here, but if you are interested in the science an earlier article A recipe for an affordable, safe, and scalable flow battery by Shalini Saxena, again in Ars Tecnica, gives a good background.
"RFBs (Redox Flow batteries) are composed of organic materials that are able to transport electrons (redox-active). Almost all RFBs are composed of two pools of liquid electrolyte separated by a membrane, which allows some ions to cross between the two liquids. In these systems, electrons then flow from the negatively charged liquid (anolyte) through to the positive charged liquid (catholyte). These electrons can either charge the system or be extracted for use. Since the key components of the batteries are liquid, things can be scaled up simply by making the holding tanks larger."

Flow batteries have some compelling advantages over solid batteries; they are readily scale-able. Simply add more liquid electrolyte to increase the storage capacity. The second great advantage, again because the charge carrier is liquid, is that it can the 'charged liquid electrolyte' can be transferred to discharge somewhere else. The most obvious application is in electric vehicles. Re-fueling of a flow battery is similar to the process with petrol or natural gas. Simply drive into a c'charge station., replace your discharged electrolyte by newly charged electrolyte and you're off again in no time. This contrasts with the very real range limit of Li-ion battery storage where re-charge is currently very time consuming.

The energy world is undergoing widespread massive research, so it is not surprising that there is a constant stream of announcements of the latest 'breakthroughs'. While many of these will not make it to every day use, some will. And they have the power to transform our lives. Many of the most common products of today would have been impossible to predict just a decade ago. Think of the impact of the iPhone, first released just a decade ago in 2007.

We live in interesting times!

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