One billion equations and 50 million unknowns

08.04.2015 13:30

Students from the Technical University of Denmark (DTU) are helping DONG Energy reduce cost of electricity (CoE) through optimisation of cable systems in the offshore wind farms.

The project team


CoE must be lower. At DONG Energy, our target is to reduce CoE by 35-40%, compared to 2012, for projects with final investment decision in 2020. Individual players can make a difference, but we can often achieve even better results through cooperation. The cables at the offshore wind farm transport power to a substation onshore which then sends the power on to our sockets. But if the cables are not used in the best possible way, it has an impact on loss of power during transport and not least on the costs for cables and installation. As the wind farms grow in size and consequently require more cables, it becomes increasingly difficult to find the best cable solution. 

Iván Arana Aristi, Cable Engineer in DONG Energy, said: "We spent a lot of time on finding the best connection of cables at our offshore wind farms. Therefore in 2011, we asked Thomas Stidsen, Professor at the Technical University of Denmark (DTU), for his advice, and he set up a contact with two of their Elite Master students, Michael Lindahl and Niels-Christian Fink Bagger." 

Georgios Rogdakis, Power System Engineer in DONG Energy, explained: "The students viewed the problem in a completely different way and this has meant that instead of spending several months developing the wind farm layout, we can now do it much faster and be sure to find the optimal layout."  

A mathematical optimisation challenge

According to the two students Michael Lindahl and Niels-Christian Fink Bagger, who are now PhD students at DTU, a different approach is precisely one of the advantages of cooperating with students. Lindahl explained:

"By viewing the challenge as a mathematical optimisation problem, we got the opportunity to develop a piece of software that processes approximately one billion equations and 50 million unknowns. This means that today DONG Energy can enter the information about the offshore wind farm in the program and receive the best possible cable layout for each of the wind farm layout options."

Bagger continued: "With this program, we've saved many hours of work. We're pleased that our work contributes to lowering CoE for offshore wind."

We have used the program since late 2013, and it has been used for the cable layouts for the Burbo Bank Extension, Race Bank, Walney Extension, Hornsea and Borkum Riffgrund 2 wind farms. It saves many hours of manual work and ensures optimum cable layouts for DONG Energy's offshore wind farms.