As solar installations ramp up and electric vehicles have been on the market for a few years, automakers are starting to look for ways to get more life out of old electric-car batteries, repurposing them for stationary storage.

And if you're going to use vehicle old batteries for storage, you might as well use big ones.

Volvo, which builds trucks and buses in addition to cars, is experimenting with taking used batteries out of 14 of its old electric buses and using them to store energy at apartment complexes that have their own solar generation.

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The effort could provide at least the kernel of a solution for apartment dwellers to be able to charge electric cars at their apartment buildings—if batteries could allow the marginal charging energy to come from solar rather than expensive grid power, or at least bring down the cost of charging.

Volvo electric bus on Gothenburg, Sweden's Route 55 [Credit: Volvo - via YouTube]

In cooperation with Göteborg Energi, Volvo has pulled the batteries out of 14 electric buses from bus route 55 in Gothenberg (Göteborg), Sweden, and installing them at the Riksbyggen Viva housing complex. Together, they each deliver 200 kilowatt-hours of storage for the complex's solar panels, for a total of 2,800 kwh.

The big battery pack can be used to reduce peak loads by using stored energy to meet demand from residents at times of peak grid demand, they can store excess solar energy generated at times of low demand, and they can store energy produced by the grid during off-peak times at low rates to use later when rates are higher.

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Viva is a new housing complex dubbed "Positive Footprint Housing," and is billed as Sweden's most sustainable housing project. Tenants are just beginning to move in.

Johanneberg Science Park will help monitor the system to help the complex maximize energy savings.

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"Electric bus batteries have good potential for other applications such as energy storage after the end of their life in public transport," said Ylva Olofsson, Project Coordinator at Volvo in a statement. "What we are examining here is exactly how good that potential is.... At Volvo we are examining various possibilities for the reuse of bus batteries for energy storage, and Viva is one such example,”

Producing batteries for electric vehicles, especially such large batteries for buses, adds a significant environmental cost in producing the vehicles. Finding a useful way to extend the life of those batteries beyond their capability in vehicles can spread that impact and reduce the need for additional production.