Vehicle-to-grid system could offer frequency response, incentivize electric ownership.

A year-long trial in Denmark is showing that utilities can use parked electric vehicles (EVs) as spare batteries, and those EVs can earn quite a bit of money for their owners from the utilities.

In an interview with Bloomberg New Energy Finance, Nissan Europe’s director of energy services, Francisco Carranza, said that a fleet of 10 Nissan e-NV200 vans has earned €1,300 ($1,530) over the year.

Electricity grids around the world are facing an era of rapid change as more electric vehicles hit the road and as grid supply changes. For grid managers, sometimes small amounts of power are necessary to regulate current frequency and keep the grid working. At the same time, if a lot of electric vehicles draw power from the grid concurrently (for example, when they’re parked at home at night, or when they’re parked at work during the day), that threatens to change how grid operators plan to meet demand, as well.

Researchers and grid managers have theorized that vehicle-to-grid connections could help solve some of these problems. By installing two-way connections where an EV could charge its battery and send power back to the grid when it’s needed, an electric car battery increases its value and makes electricity infrastructure more stable.

Research has been done on vehicle-to-grid connections for years. In 2010, East Coast grid manager PJM worked with the University of Delaware to test communication control and logic between an electric vehicle and a grid.

More recently, Ford and GM have tried similar tests, working especially to synchronize charge and discharge cycles so that the owner of the EV always has enough juice to get in the car and go when necessary.

Read more: ars Techinca