Cheap energy storage may be parked in your garage

One of the key questions about how to bring in more renewables is how do we provide low-cost storage? Batteries can cost $350 per kilowatt (kW) and pumped storage somewhat lower. Maybe we should think about another potential storage source that will be very low cost: automobiles.

California has about 24 million autos. The average horsepower is about 190 HP which converts to about 140 kW. Let’s assume that an EV will have on average a 100 kW engine. Generally cars are parked about 90% of the time, which of course varies diurnally. A rough calculation shows that about 2,000 GW of EV capacity is available with EVs at 100% of the fleet. To get to 22 GW of storage, about 1% of the state’s automobile fleet would need to be connected as storage devices. That seems to be an attainable goal. Of course, it may not be possible for the local grid to accommodate 100 kW of charging and discharging and current charging technologies are limited to 3 to 19 kW. So assuming an average of a 5 kW capability, having 20% of the auto fleet connected would still provide the 22 GW of storage that we might expect will be required to fully integrate renewables.

The onboard storage largely would be free–there probably are some opportunity costs in lower charging periods that would have to be compensated. The only substantial costs would be in installing charging stations and incorporating smart charging/storage software. I suspect those are the order of tens of dollars per kW.


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