Europe plans to fill the North Sea with 300 GW worth of wind turbines. To call this is an enormous task is an understatement to say the least. Europe will need to place 20 thousand wind turbines of around 15 MW. These structures are 145m high with an additional 120 m for the blades. They weigh about 1700 tons and are supported by foundations that attach to the seabed. Foundations for the North Sea can easily be 70 meters long weighing about 2000 tons. Additionally, electrical cables and other expensive components are needed to get the green energy to shore. Once these giant structures are placed, they stay put for about 25 years. Needless to say, you better place them in the right spot from the beginning, or your mistake will be staring you in the face for 25 years to come.
This begs the question, what is the optimal position? Inherently it is a discussion between different points of view; economic, ecologic, strategic, etc. But the one thing everyone can agree on is that the turbines need to produce clean energy, and preferably as much as possible. New studies found that the offshore production of energy with wind turbines is more complex than our initial thought.
Wind farms experience a phenomenon called ‘wake effects’. This causes sequential wind turbines to produce less energy; the first turbine gets a perfect wind flow, while the turbines behind are left with a more perturbed wind flow. These effects are not new. They have been studied onshore as well and wind farms that are placed today get such a configuration to mitigate wake effects as much as possible. This optimization was enough for the onshore wind industry due to a varying landscape. At sea, however, there is an immense open space, causing the wake effects of wind farms to be noticeable up to 100km further, new studies have found. Now, the impact is not solely felt from turbine to turbine, but from windfarm to windfarm. Energy production is reported to fall 10 to 30 percent for windfarms that lie in the wake of another.
Several problems are arising following this new insight. First, energy output drops will reduce the profitability of any offshore wind project, which will be felt in the energy prices. Second, the current windfarms now have a checkmate on certain positions in the North Sea; a developer doesn’t want to place new windfarms behind existing ones because of the direct impact on its revenue. The opposite is true as well; existing windfarms will suffer huge losses if new windfarms are allowed to be placed in front of them. This has prompted the question of compensation for the wind that has been ‘stolen’. The biggest problem is the current lay out and framework for European wind placement. Every country is looking to achieve their own offshore wind goals. It is currently viewed as a national problem, and very little international conversation is held in terms of windfarm placement. The impact of these wake effects will be huge because of the envisioned offshore wind buildout in each North Sea country. Along the shoreline of Belgium, The Netherlands, Germany and Denmark, multiple GW windfarms will be placed in the future. This entire area has a preferred wind direction coming from the southwest, effectively placing all the windfarms in each other’s wake, causing stacked energy losses. This causes new uncertainty of wind farm placement and development, something that has been hindering this industry since its conception.
Only international cooperation can solve these problems. By viewing the North Sea basin as an international entity, wind farms can be optimally placed, considering cross border effects such as wake effects. It can be as simple as implementing more spread in the farm placements to benefit from better wind flows. This philosophy is gaining more and more traction influenced by the difficulties faced in supply chain, harbors and electricity infrastructure.
New insights in wake effects are a wakeup call for the umpteenth time that along with the high ambitions Europe has placed upon the North Sea, a high degree of international cooperation is needed. The offshore wind industry is developing at such an excruciating pace, that we might make head over heel decisions that can be proven detrimental in the future. It’s time we stop asserting high capacity numbers which look good in international agreements and start developing a clear international direction to bolster the European offshore wind industry.
