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Battery Storage? Try Thermal Batteries

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Rakesh  Sharma's picture
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I am a New York-based freelance journalist interested in energy markets. I write about energy policy, trading markets, and energy management topics. You can see more of my writing...

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As battery storage gains ground in electricity grids, lithium-ion batteries have become the most popular options to incorporate storage technology into the grid.

But their use is beset by myriad problems. Such batteries are expensive in comparison to natural gas plants. They are time-limited due to constraints in their charge capacity. The supply for lithium, the raw material for such batteries, is concentrated in regions wracked by conflict. Lithium-ion batteries also have problems cycling up or down to meet emergency demand.

No wonder then, other storage technologies are being developed to overcome Li-ion’s shortcomings. The latest storage technology contender that shows promise is thermal battery storage or storage that uses thermal energy.

There’s an interesting post on the IEEE website about two startups that use thermal energy to store energy produced by renewable sources. One of them is Antora energy. The Sunnyvale, Calif., - based startup is proposing the use of carbon blocks for energy storage. It plans to use graphite blocks, used as electrodes in electric furnaces in the steel industry, that are heated up to 1,000 degrees Celsius to store energy produced by renewable sources. This will solve supply chain issues that plague lithium-ion batteries, the startup’s founders say. The heated blocks will be encased in rockwool – an insulating material made with basalt and slag, a byproduct of the steel industry.

The blocks are hooked onto a thermophotovoltaic (TPV) system that can be used to harvest energy from the blocks. According to startup’s founders, TPV is “leftover light” and can be reflected back into the thermal source (as opposed to silicon-based photovoltaic systems).

TPV systems, typically, have efficiency of 20%, a figure comparable to silicon-based systems.

But Antora’s founders produced research that claims to have increased its efficiency to 30% by switching from silicon cells to III-V semiconductors. They say their system can connect directly to solar panels or wind turbines and even to the electrical grid in order to store energy in batteries.

Another startup, Electrified Thermal Solutions, plans to use honeycomb-shaped ceramic blocks to store energy. They are working on a plan to make ceramic conductive to electricity and slow down the oxidization process for ceramics. On the plus side, they think that their solution will last 20 years, much longer than any of the available storage solutions in the market.

Given the current market for storage technology, both ideas have found quite a few takers. Antora has been funded by the likes of ARPA-E and the Shell and National Renewable Energy Laboratory program while Electrified is part of an accelerator program run by U.S. – based funders and research laboratories.

Thermal Storage: An Idea Whose Time Is Yet to Come?    

These two startups are the not only ones experimenting with thermal battery construction. EnergyNest, a startup in Norway, has built a container-sized thermal battery using carbon pipes. Climate Change Technologies (CCT), a South Australia startup, has built a thermal battery using molten silicon. 

The idea of thermal storage using material that is available in abundance is promising. But the kinks still need to be worked out. 

Their supply chain could be plagued by the same charges of not being environment-friendly as Li-ion. The steel industry is considered among the worst global polluters. Rockwool, the insulating mechanism, carries significant environmental impact baggage because it is hard to dispose of and manufactured using byproducts from a harmful industry.

There’s also the question of economies of scale. According to 2017 research, III-V – based TPVs, used in Antora’s systems, have high semiconductor growth and substrate costs that make fabrication roughly 100-fold more expensive than silicon cells. The total costs of these systems, and of connecting them to the grid, are yet to be determined.

But these are early days. Both companies are part of early venture programs and it might be a while before they see them connected to the grid. Meanwhile, Li-ion will continue to dominate, regardless of its problems. The success of these startups really depends on how well they are able to tackle the challenges accompanying the development of a cost-effective renewable energy storage mechanism.

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