In Frederiksberg in Denmark, Nissan is collaborating with the local utility company, Frederiksberg Forsyning, software company Nuvve and Italian energy concern, Enel.

Carmakers such as Nissan, BMW and Honda are exploring vehicle-to-grid projects with energy and software companies.

Electric cars themselves can also be harnessed as energy stores. So-called “vehicle-to-grid”, or V2G, essentially uses electric vehicles as batteries on wheels.

Frederiksberg Forsyning has replaced ten of its vehicles with Nissan all-electric vans and has installed ten special “bi-directional” charging points. Its engineers unhook their vehicles in the morning, go off to their jobs around the city and return the vehicles to the charging point in the afternoon.

After that the batteries are at the disposal of the grid.

Nuvve’s software, which was developed in the University of Delaware in the US, connects to the grid and constantly monitors its energy requirements. If there is a fluctuation in power it can call on the multiple batteries on its system, to smooth it out within seconds.

“We call this a virtual power plant” says Marc Trahand, chief operations officer for Nuvve in Europe. “All these small batteries put together...become one big power plant that you can then activate onto the grid."

But how do you ensure that the engineers don’t arrive at work to find the grid has “stolen” all the power in their batteries?

“Daily operation is the king,” says Kristian Beyer, Frederiksberg Forsyning’s head of staff and strategy. Employees are equipped with an app to enable them to control the energy levels in their cars, he says, and through trial and error the company has worked out how much charge needs to be left in the battery each morning.

The vehicles don’t only help when demand on the grid is high, but also when there is a surplus of supply in windy Denmark, says Mr Beyer:

“The more we can use or store the energy when it’s available, the better we can use our infrastructure, because sometimes we are wasting energy available to us and it would be a better option to store it and use instead of power plants and so on.”

Vehicle-to-grid schemes are designed to compensate drivers for lending their car to the grid.

But Dr Kotub Uddin, a vehicle-to-grid expert from the University of Warwick and now head of energy storage at OVO Energy, says that for vehicle-to-grid technology to take off commercially, people will have to be sure that their car batteries won’t be damaged.

Taking energy out of a battery and charging it repeatedly can cause the battery to degrade depending on factors such as the ambient temperature when the battery is charging, and how the car is used by the owner.

The answer to these problems is smart charging, he says.