Offshore wind energy in the North and Baltic Seas: A challenge for maritime spatial planning

As part of this year’s Elia Group Viewpoint, the project “Enpowering Europe’s next phase of offshore wind” aims to optimize the cabling of offshore wind farms by 2050 and minimize conflicts of use. Two scenarios, Minimum Asset and Nature First, were developed to analyze the costs and efficiency of cabling. The results demonstrate that international cooperation can reduce costs, even in the presence of heightened restrictions.

Motivation

The implementation of maritime spatial planning in the North Sea and Baltic Sea is already characterized by an increasing pressure of use (see Figure 1). In addition to the establishment of protected areas for the conservation of natural resources, military training grounds, mining operations for raw materials and aquaculture, there has been a notable increase in the construction and interconnection of wind farms. Considering the ambitious expansion targets set by coastal states for offshore wind energy generation, it is likely that utilization pressure will continue to increase, leading to an increased likelihood of conflicts of use. By 2050, the installation of offshore energy in the North and Baltic Seas is projected to reach approximately 370 GW, a significant increase from the current levels. At present, most wind farms are connected radially, which is inadequate for the future challenges posed by the expansion targets. The creation of new grid topologies, such as networks or interconnectors, and the fostering of increased cooperation between coastal states represent potential avenues for achieving the expansion targets without the necessity of imposing restrictions on the various uses.

Objective

The aim of the “Enpowering Europe’s next phase of offshore wind” project is to optimize the cabling between wind farms and landfall points in extreme and combined scenarios for the years 2030 and 2050. These scenarios differ in the extent to which co-utilization of areas can save costs. Connection topologies for a cooperative and networked cabling system are also identified. As a result of the overall optimization, possible cooperations between individual riparian states are examined and evaluated in order to exploit synergies and increase the overall efficiency of offshore wind energy projects.

Methodology

Two scenarios are considered in total: Minimum Asset and Nature First. The difference between Minimum Asset and Nature First is that Minimum Asset has hardly any restrictions to prevent co-use, while the Nature First scenario prioritizes nature conservation areas and requires significantly higher costs for the crossing of protected areas and other forms of use. All maritime spatial plans of the coastal states are taken into account, through which the relevant forms of use, such as infrastructure corridors, wind farm areas, shipping routes, anchorages, military areas, nature conservation areas, aquaculture and sand, material and oil exploration areas are located. These areas are weighted using an analytical hierarchy process (AHP) based on their protection requirements [2]. After verification, this weighting is used as a cost parameter for calculating the shortest routes. The A* algorithm of the PostgreSQL extension pgRouting is used to calculate the shortest routes between wind farms and connection points or ‘Points of Connection’ (POC).

Finally, the overall costs of the system are minimized through allocation optimization. This ensures that the various wind farms are connected onshore, taking into account various restrictions, including the achievement of expansion targets per country and a minimum installed capacity per connection point. Finally, an initial assessment of the resilience of the optimized system was carried out. In particular, the width of a cable corridor and the transmitted energy are considered.

Results

The results demonstrate that collaboration between a considerable number of countries is a viable proposition (see Figure 3). It is possible to reduce costs not only by utilizing interconnectors and hybrid intermediate connections, but also by connecting a wind farm from a neighboring Exclusive Economic Zone. To illustrate, the connection of wind farms from neighboring Denmark to Germany is a more cost-effective solution than the utilization of the priority areas of the Dogger Bank in their entirety.

As the variable costs between the scenarios are largely determined by the length of the cable route, Figures 4 and 5 illustrate the results of the optimized system for the North Sea and Baltic Sea, considering the overall cable length.

The data presented in Figure 5 suggests that the cost difference between the two scenarios is negligible despite the higher restrictions on co-utilization of land in the Minimum Cuts scenario. This indicates that future offshore planning should rely more on cooperation than on the co-utilization of land. A final resilience assessment and optimization of a resilient system, which will be of future importance given the current global political situation, was carried out in this project with a simplified approach through the analysis of critical corridors. The results of this analysis demonstrate the necessity for further investigation of this topic in the future.

Literatur

[1] Elia Group launches vision paper on the virtuous circle of offshore wind benefits in Europe

[2] Klaus D. Goepel, (2013). Implementing the Analytic Hierarchy Process as a Standard Method for Multi-Criteria Decision Making In Corporate Enterprises – A New AHP Excel Template with Multiple Inputs, Proceedings of the International Symposium on the Analytic Hierarchy Process, Kuala Lumpur 2013. DOI: https://doi.org/10.13033/isahp.y2013.047