A Stanford research team has come up with a new mathematical formula they call the ESOI to determine the long-term energetic costs of any energy storage system.
ESOI, which stands for Energy Stored On Investment, calculates the amount of energy any storage system can store in its lifetime compared to the amount of energy used to build it.
Pumped hydro has the highest ESOI value of 210, whereas a lithium-ion battery has a mere score of 10. Lead-acid batteries fare the worst at an ESOI value of 2.
Stanford’s Charles Barnhart suggested that the best way to improve the ESOI value of batteries would be to improve its cycle life. In other words, batteries should last longer, as this would increase the number of times energy is stored in and discharged from it. “Pumped hydro storage can achieve more than 25,000 cycles,” he said. “That means it can deliver clean energy on demand for 30 years or more. It would be fantastic if batteries could achieve the same cycle life.”
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