Second-Hand EV Batteries to Benefit Solar Energy Farms

As the electric vehicle (EV) industry keeps growing, a solution for disused EV batteries urgently needs to be put forward. Otherwise the world will end up with a huge number of EV batteries that are no longer sufficient to power vehicles, but sitting around idly still in decent condition.

An MIT study has discovered that these batteries could still prove very useful in the second part of their lives when used as backup storage for grid-scale photovoltaic installations, aka solar energy farms. 

Their findings were published in Applied Energy.

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Not as easy as it may sound

In order to test their theory out, the researchers used a hypothetical grid-scale solar farm in California.

Testing out a number of economic scenarios they discovered that installing a new battery system in solar energy farms wasn't profitable, but when they used EV batteries on their second life, a profitable investment could be met as the batteries cost under 60% of their original price. 

Ian Mathews, a postdoc at MIT and author of the study, explained it isn't quite as simple as that "There are many issues on a technical level. How do you screen batteries when you take them out of the car to make sure they’re good enough to reuse? How do you pack together batteries from different cars in a way that you know that they’ll work well together, and you won’t have one battery that’s much poorer than the others and will drag the performance of the system down?"

The next main question is: how long will the batteries last? 

The study stayed cautious and decided that once the batteries reach 70% of their lives they should be decommissioned. That's down from 80%, as this is the percentage when EVs stop using their batteries. The team acknowledged that the batteries could well continue operating safely and in a useful way at 60% capacity or even lower. 

This could all prove very useful for the second part of EV batteries' lives. A recent report by McKinsey Corp. demonstrated that as demand for backup storage for renewable energy projects keeps growing from now until 2030, this method of re-using EV batteries could prove extremely useful. 

As Mathews explained "the point that I made in the paper was that technically, economically, … this could work."

For the next step, he said, "There’s a lot of stakeholders who would need to be involved in this: You need to have your EV manufacturer, your lithium-ion battery manufacturer, your solar project developer, the power electronics guys." The point, he explained "was to say, 'Hey, you guys should actually sit down and really look at this, because we think it could really work.'"