Green Wombat notes that PG&E’s Battery Power Plans Could Jump Start the Electric Car Market by providing a secondary market for used but not quite used up batteries:
Electric car batteries generally retain 80 percent of their capacity even after they’re no longer good for powering cars. Thesen envisions a time in the near future when banks of EV batteries are charged at night with electricity produced by wind farms, which tend to generate the most electricity in the evening when power demands are the lowest. Normally, that energy is just lost because it isn’t stored. During the day when air conditioners crank up and energy demand rises, electricity can be released from the batteries to take the load off the power grid.
I’m not sure the green spin is fully warranted. It’s really about building less new capacity, which is quite expensive:
In theory, that means PG&E won’t have to build as many planet-warming natural gas-fired power plants to meet peak demand or as an insurance policy against blackouts. It also allows the utility to do “load leveling.” Cranking up a power plant to supply electricity when demand suddenly spikes is expensive. EV batteries could release electricity to the grid to smooth fill in the gaps between supply and demand. The same is true if batteries are used at electrical substations. “If we can put in $5,000 worth of batteries and avoid putting in a $50,000 transformer and upgrading the lines then everyone is a winner,” says Thesen.