https://arstechnica.com/cars/2017/08/parked-electric-cars-are-earning-money-balancing-the-grid-in-denmark/
People have been talking about this for years, but I did not realize anyone had implemented it. The US grid needs so many upgrades, but this is key to making renewables work. If everyone has an electric car wit a 200+ mile range and the average commute is 20 miles, that creates a massive energy store.
Nice! I wasen't aware of that test. Great idea.
more general info
https://www.vox.com/energy-and-environment/2017/8/15/16148084/electric-vehicle-batteries-v2g