The use of used power batteries in large-scale solar energy storage projects is very commercially viable

Scientists at MIT believe that used batteries could be more commercially viable than dedicated grid-scale solar energy storage systems in California. Such "recycled" batteries could cost as little as 60% of their original purchase price, and could be efficiently aggregated for industrial-scale energy storage systems even if they have lost 80% of their original capacity.

Used batteries could be used to store electricity generated by large-scale solar farms, according to a study from MIT.

Because such second-life batteries can cost just 60% of their purchase price, even for devices that have lost 80% of their original capacity, solar-plus-storage projects in California could offer better investment prospects than purpose-built utility-scale batteries, U.S. researchers say.

Ian Mathews, co-author of the MIT study, agrees that there are still technical barriers to large-scale use of spent power batteries. Such as aggregating batteries from different manufacturers and screening which devices can be reused. However, Mathews insists that there are still enough business reasons for spent power batteries to justify the cost of recycling batteries, testing performance, and reconfiguring batteries.

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The researchers used semi-empirical models (including some "up front" calculations) to estimate the degradation of the battery and concluded that running the polymer storage device at 15-65% charge would extend the battery's life. "This finding challenges some previous assumptions that running a battery at maximum capacity initially would provide the most value," the scientists said.

Mathews said the viability of second-use battery storage depends on the regulatory and rate-setting mechanisms they will operate under. “For example, some local regulations allow the cost of storage systems to be factored into the overall cost of new renewable energy supply for price-setting purposes, while other regulations do not,” he said.

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The academic added that the potential of the system requires longer-term pilot studies to assess.

The MIT researchers note that control algorithms could be adjusted during a project to extend the viable life of such facilities. "We think this could be a great application for machine learning methods," Mathews says. "We're trying to figure out an intelligent way and predictive analytics to adjust those control strategies over the life of a project."

Mathews added that successfully using power batteries for grid-scale energy storage systems will also require the joint participation of electric vehicle manufacturers, energy storage companies, solar project developers and power electronics experts.

The MIT research project is supported by the European Union’s Horizon 2020 research program, as well as the U.S. Department of Energy and the National Science Foundation, and the National Research Foundation of Singapore through the Singapore-MIT Alliance for Research and Technology’s Engineering Research Center for Quantum Sustainable Solar Technologies.

Bern University of Applied Sciences in Switzerland is also investigating how to transform used solar cells and batteries. The Horizon 2020 project will run until 2022.