The project: Breaking new ground
The offshore wind farm “Meerwind Süd | Ost“ by WindMW GmbH, including 80 wind turbines (WT) and a total wind farm area of 43 km², has been erected on budget and was fully functional with commissioning. Located 23 kilometers north-west of Helgoland in a water depth of 22 to 26 meters, the wind farm generates up to 288 megawatts (MW) that are fed in the grid by its converter platform, the Topside. Due to the large distance to the shore, the height of 149 meters of each WT and the number of WTs, the wind farm presented challenges to everyone involved. To this time there was no comparable project worldwide. In total more than 100 DNV GL experts have been involved, due to the customer’s high quality standards in securing the added value of the wind farm and its components.
The result: More performance
With the foundation of the monopiles, the installation of the transition pieces and the wind farm internal converter platform, project certification organization DNV GL successfully supported the technical pioneering work in three central issues. In doing so, the costs before and during construction were minimized.
With its unique technical expertise and cooperation in close partnership DNV GL made a decisive contribution to increasing the performance of “Meerwind Süd | Ost”. “We chose DNV GL because it offers well experienced and trained experts on renewables, extensive resources, and worldwide expertise. This enabled us to reach efficient solutions”, Jens Assheuer, Managing Director of WindMW, summarizes.
1. Foundation of monopiles: Efficient and straight development through close partnership
Prior to “Meerwind Süd | Ost” there was no comparable offshore construction within the perimeters of the German North Sea. An offshore WT with a height of 149 meters and a rotor diameter of 120 meters far away from the shore is exposed to specific strains and stress within the calculated life cycle of decades. It was an extraordinary challenge for the engineers of WindMW and DNV GL to create a secure and at the same time cost-efficient fundament.
The solution was developed in a complex process that was accompanied intensively by DNV GL from the very beginning. The early started interplay between constructor and certification organization enabled an efficient and straight development that led to performance optimized wind farm operation. In particular the external perspective of DNV GL led to new approaches on sustained optimization of the design in regard to its full life cycle.
2. Connection of monopiles and transition pieces: Acceleration of the installation
Monopiles and transition pieces of these dimensions – up to 700 tons of individual weight – had never been put together. Another challenge was the construction during winter: The used concrete had to be processed with a temperature of at least 5 degrees Celsius. In addition, the acceptable wave height and wind speed that allowed construction were a big limitation.
Within a couple of days DNV GL experts were able to provide independent evidence that even lower temperatures, bigger wave heights and stronger winds than argued before still enable construction. This reduced the time needed for construction and installation of the project and kept the project within the budget.
3. Wind Farm Internal Converter Platform: Synchronization of 80 electrical current flows under offshore weather conditions
Besides the fact that offshore converter platforms have to deal with different climate conditions than onshore projects, the main challenge was the synchronization of 80 different current flows by the Topside. To achieve this goal, comprehensive equipment was needed – and due to the lack of comparable projects worldwide there was no experience to rely on.
DNV GL brought its experts from all different branches together, such as Oil & Gas or Maritime, to evaluate pressure lines, electrical and safety systems and to enable the best possible solution for WindMW.
“We want to be the spearhead of quality assurance. Project certification with DNV GL offers a maximum of reliability for our customers to get the safe and cost-efficient wind farm they planned and ordered. In close cooperation with our customers we push the limits and achieve a higher profitability”, Fabio Pollicino, Global Service Line Leader for Project Certification at DNV GL, says. DNV GL Senior Engineer Robert Grohe adds: “The experience we made in this project increases our knowledge for future projects even in greater distance to the shore. We are looking forward to mastering these upcoming challenges with our customers.”