DTU Elektro researchers Andreas Thingvad and Lisa Calearo, along with Mattia Marinelli working on the ACES project at Bornholm

Smart charger key to keep renewables running on Bornholm

Monday 26 Nov 18
by Rikke Høm Jensen


Mattia Marinelli
Associate Professor, Head of Section
DTU Wind
+45 46 77 49 55

The ACES project

A Danish funded research project involving Nissan, Bornholm Energi og Forsyning, NUVVE and DTU Elektro

Started in April 2017 and is running until March 2020.

The main objective is to holistically investigate technical and economic system benefits and impacts by large scale electric vehicles integration in Bornholm, augmented by real usage patterns, grid data and field testing for across continents replicability.


DTU Elektro researchers have been investigating different methods for leveraging the flexibility provided by the storage in Electric Vehicles. Amongst these, test on smart chargers have been carried out succesfully. For the first time a smart charger has been deployed in Denmark outside the University for public usage.

From time to time, the electric cable connecting the island of Bornholm to the rest of the Nordic power system is cut by accident. When this happens the local grid operator has to stop nearly all renewable plants to keep the system stable to prevent possible blackouts.

Electric vehicles can be used as a means to support the energy balance of the island also during such perilous times, allowing more renewable to remain operational. To do so smart chargers is a necessity . 

For the first time a smart charger is deployed in Denmark outside the University for public usage. The charger is hosted by Hotel Griffen in Rønne, that makes the charge available for free to customers.

Supporting the energy balance
The working principle of the smart charger is simple. Whenever a vehicle is connected, the charger will initiate the charge at a reduced power level. According to the frequency of the electric grid, the charger will either increase the power or reduce it.

"Naturally, size matters and in order to replace a conventional power plant with renewables it is necessary to deploy tens of thousands of chargers"
Mattia Marinelli, project leader of ACES

"The electrical frequency is the key indicator of any power system balance," says Mattia Marinelli, associate professor at DTU and ACES project leader.

“if there is a balance between generation and consumption the frequency will remain constant at 50 Hz. However, consumption is continuously changing and most renewables, as wind and solar, are not controlled because of economic reasons. This implies that the remaining generation plants have to adjust their power output continuously in order to keep the system stable," he continues. 

If the frequency is increasing it means that the system is facing an excess of generation and, if it is decreasing, it means that it is experiencing an excess of consumption. The underlying idea is to adjust the consumption of the vehicle in order to emulate the controlling capability of a power plant.

Naturally, size matters and in order to replace a conventional power plant with renewables it is necessary to deploy tens of thousands of chargers, says Mattia Marinelli. 

How does the smart charger work?
Practically, the EV will start charging either at 2.3 kW (11 A single phase) or 6.9 kW (11 A three-phase), depending on the capability of the vehicle internal equipment. The charging process will therefore be continuously modulated by either increasing up to 16 A or reducing to 6 A with a step granularity of 1 A.

The smart charger is different compared to another approach used to provide frequency control relying on more complex and expensive bidirectional chargers as the ones tested in Frederiksberg in the Parker project and deployed in Bornholm also as part of ACES. More details can be found in the following publication:

  • M. Marinelli, S. Martinenas, K. Knezović, and P. B. Andersen, “Validating a centralized approach to primary frequency control with series-produced electric vehicles,” J. of Energy Storage, vol. 7, pp.63-73, Aug. 2016. https://doi.org/10.1016/j.est.2016.05.008

Related activities on the island on battery degradation
As mentioned above, there are currently 20 V2G bidirectional 10 kW chargers and 20 Nissan vehicles used by the municipality employees at Bornholm during day-time for driving and for providing bidirectional frequency control during the night. 

DTU Elektro researchers Andreas Thingvad and Lisa Calearo, along with Mattia Marinelli, recently combined a trip to Bornholm for commissioning the smart charger with another important activity pursued within the ACES project: assessing how much the storage of the 20 EVs in the project will degrade after one year of driving and grid services. It is critical to measure how much the usage of the EVs for providing frequency services to the power system is potentially shortening the lifetime of the battery as this could severely reduce the profitability for providing services to the power system.

If interested in the outcome on the smart charger and battery degradation stay tuned for more news! Updated project results can be downloaded from the ACES project website.

Follow the Smart Charger live!

In order to visualize the charger's live data go to: https://evbe.elektro.dtu.dk/ -> select the charger in Bornholm -> Disable: ‘all’ -> Enable: ‘Active power sum (kW)’

(If the page https://evbe.elektro.dtu.dk/ turns blank, please try copying the URL directly into your browser.)


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