Wakeup call for offshore wind positioning

Europe plans to fill the North Sea with wind turbines capable of generating 300 GW of power. To call this an enormous task is an understatement. Approximately 20,000 wind turbines, each around 15 MW in capacity, will need to be installed. These structures stand about 145 meters tall, with blades adding an additional 120 meters. They weigh around 1,700 tons and are supported by foundations attached to the seabed. Foundations in the North Sea can easily be 70 meters long and weigh about 2,000 tons. Additionally, electrical cables and other expensive components are required to transmit the green energy to shore. Once these giant structures are placed, they remain fixed for about 25 years. Needless to say, it's crucial to position them correctly from the start, or your mistake will be staring you in the face for 25 years to come.

The challenge of wake effects in wind farm placement

This raises the question: what is the optimal positioning? This inherently involves balancing different perspectives—economic, ecological, strategic, and more. However, one thing everyone can agree on is that the turbines need to produce clean energy, and preferably as much as possible. New studies have found that offshore energy production with wind turbines is more complex than initially thought.

Wind farms experience a phenomenon called wake effects, which causes sequential wind turbines to produce less energy. The first turbine receives an undisturbed wind flow, while turbines behind it encounter more turbulent air. These effects are not new; they have been studied onshore, and modern wind farms are configured to mitigate wake effects as much as possible. This optimization sufficed for the onshore wind industry due to the varying landscape. At sea, however, the immense open space means that the wake effects of wind farms can be noticeable up to 100 kilometers away. Now, the impact is not only felt from turbine to turbine but also from wind farm to wind farm. Energy production is reported to fall by 10 to 30 percent for wind farms that lie in the wake of another.

 

 

Figure: Exaggerated wake effects causing turbulent wind flow behind turbines (source: Vattenfall)

 

Several problems are arising from this new understanding of offshore wind farm wake effects. First, energy output reductions will decrease the profitability of offshore wind projects, which could lead to higher energy prices for consumers. Second, existing wind farms now have a strategic advantage—or a "checkmate"—over certain positions in the North Sea. Developers are reluctant to place new wind farms downwind of existing ones due to the direct impact on revenue from reduced wind speeds. Conversely, existing wind farms could suffer significant losses if new wind farms are installed upwind of them. This situation has raised questions about compensation for the wind that has been effectively "stolen."

 

The need for international coordination in wind farm placement

 

The biggest challenge lies in the current layout and framework for European wind farm placement. Each country is focused on achieving its own offshore wind goals, treating the issue as a national concern with little international coordination. The impact of wake effects will be substantial given the planned offshore wind expansions in each North Sea country. Along the coastlines of Belgium, the Netherlands, Germany, and Denmark, multiple gigawatt-scale wind farms are slated for future development. This entire area experiences prevailing winds from the southwest, which means the wind farms will be positioned in each other's wakes, leading to compounded energy losses. This adds new uncertainties to wind farm placement and development—issues that have been hindering the industry since its inception.

Figure: blue circle depicts the area where future windfarms will likely be placed on current roadmaps. Green arrow shows the main wind direction for all these wind farms, which will cause wake effects. (Source: Econopolis Strategy)

Only international cooperation can solve these problems. By viewing the North Sea basin as a shared international resource, wind farms can be optimally placed while considering cross-border effects such as wake interactions. Simply spreading out the farm placements could lead to better wind flows and increased efficiency. This philosophy is gaining traction, influenced by difficulties in supply chains, harbors, and electricity infrastructure.

The new insights into wake effects are a wake-up call that, along with Europe's high ambitions for the North Sea, a high degree of international cooperation is essential. The offshore wind industry is developing at such a rapid pace that we risk making hasty decisions that could prove detrimental in the future. It's time we stop focusing solely on high capacity numbers that look good in international agreements and start developing a clear, internationally coordinated strategy to bolster the European offshore wind industry.