DONG Energy and Vattenfall cooperate on emergency power supply for Horns Rev

Cooperation is possible, even if you are competitors. The two companies have initiated a common project to ensure the emergency power supply for DONG Energy's wind farm, Horns Rev 2, and Vattenfall's upcoming wind farm Horns Rev 3.
Both DONG Energy and Vattenfall Vindkraft A/S now secure their billion DKK investments in the Horns Rev 2 and Horns Rev 3 wind farms in the North Sea with a mutual agreement on supply of emergency power for each other's wind turbines if their respective export cables to land fail.

The turbines must always have power supply

Niels Møller Jensen, project manager, Vattenfall

“If the export cable fails, it’s not only critical for the supply of electricity to customers on the mainland. A cable outage is also critical to the wind turbines. All turbines must always have power, especially to keep the blades’ positions correct in relation to the wind direction. Emergency power for the wind turbines normally comes from one single large, centrally located generator on a platform at sea. At Horns Rev 3, we’ve chosen to install a small generator in each of the 49 wind turbines and, as something new in the industry, we’ve made an agreement with DONG Energy that we install an 8km long 33kV cable between Horns Rev 2 and Horns Rev 3, thereby establishing a connection between both wind farms."

Optimal solution


Niels Møller Jensen emphasises that it is an optimal economic and environmental way to secure the emergency power supply. The small diesel generators in the wind turbines at Horns Rev 3 will ensure the power supply for a few days until Vattenfall knows how long a potential power failure will last. If it seems to last for a longer period, the supply from Horns Rev 2 is switched on and the wind turbines on Horns Rev 3 can be supplied with emergency power until the export cable is back in operation. The same goes for the other way.

Leif Winther, DONG Energy Asset Management, is pleased with the mutual agreement with Vattenfall:

"We see the cooperation with Vattenfall on the emergency power supply as a good guarantee for both wind farms, which keeps the wind turbines in good condition so that they can start producing again really quickly once the fault is corrected and in addition, it’s a relatively small investment in an emergency power cable if one looks at the total cost of an offshore wind farm."

For additional information,
please contact Media Relations

Tom Lehn-Christiansen +45 99 55 60 17