A Site Selection of An Energy Island in the North Sea: Optimal Location in an Ecological and an Economic Scenario Using a Multicriteria Decision Analysis (MCDA)

Abstract

Max Bengtsson
A Site Selection of An Energy Island in the North Sea: Optimal Location in an Ecological and an Economic Scenario Using a Multicriteria Decision Analysis (MCDA).
The Danish Government has decided to build an energy island, either as an artificial island in sand, concrete and steel or as a platform solution in the Danish exclusive economic zone (EEZ) of the North Sea. The idea of the energy island is to connect offshore windfarms (OWFs) in the North Sea region to a central hub and re-distribute the wind energy to Denmark and its neighboring countries as the transition to a fossil free energy generation is being scaled up. The government has found a location in the North Sea Section East.
However, the North Sea is known for its sand lance (Ammodytes Sp.) fish habitats which are critical to the local ecosystem as the sand lance is at the base of the food chain and the fish is prey for other fish, marine mammals and seabirds - some of which are vulnerable to commercial fisheries, offshore development and mining.
To test whether the planned energy island would coincide with a sand lance habitat and to test if other alternative locations would be more suitable i.e. have a lower sand lance density, two other sections of the Danish North Sea were selected in this study. The other sections were the North Sea West and the Dogger Bank of the Danish EEZ, both of which have good conditions like shallow waters and sandy sea bottoms. Furthermore, the study tested all sections in an ecological scenario with a focus on sand lance and the local ecosystem and an economic scenario with a focus on economic factors such as distance to shore and the wind resource.
Multicriteria Decision Analysis (MCDA)
A so-called multicriteria decision analysis was implemented in combination with a GIS to give the different ecological and economic factors a weight relative to their importance. The two scenarios were compared to an equal weights scenario i.e. where all factors had the same importance. The multicriteria decision analysis used was the analytic hierarchy process (AHP).
Results
The North Sea Section East performed the best in both scenarios as the sand lance density here was within acceptable limits in an ecological perspective and the seabed, depth and windspeed conditions were acceptable in an economic perspective. The Dogger Bank was deemed non-suitable in both scenarios as the sand lance density was too high in an ecological perspective, the section was too distant from the shore and the windspeed was too low in an economic perspective. The study also concluded that an ecological scenario would not result in extra cable costs and an economic scenario would not result in a location with a high sand lance density. In fact, the North Sea Section East location would both have ecological and economic benefits.
A sensitivity analysis was performed of the ecological and the economic scenarios to check the robustness of the study. The sensitivity analysis confirmed the study robust.

Keywords: Geography, GIS, Energy Island, Energy Hub, Multicriteria Decision Analysis, MCDA, AHP, Offshore Windfarm, OWF, Site Selection, EEZ.

Advisor: Marko Scholze
Master’s degree project 30 credits in Geographical Information Sciences, 2024
Department of Physical Geography and Ecosystem Science, Lund University
Thesis nr 181

Popular Abstract

Max Bengtsson
Finding an optimal ecosystem friendly versus an economic site for an energy island in the North Sea
The Danish government has decided to build an energy island either as an artificial island or a platform solution like an offshore oil rig in the North Sea. The purpose is to connect offshore windfarms with the island and re-distribute wind energy to mainland Denmark and its neighboring countries. The idea is to transmit wind energy to Denmark and its neighbors more efficiently and reliable, while also promoting “green” energies like wind power while also downscaling the use of “black” energies like oil and gas from the North Sea. However, the construction of an energy island, especially an artificial island, may not be without consequences. Its construction could occupy some seabed which is an important living space for different species.
A species at risk is the sand lance (Ammodytes sp.), a fish which is at the base of the food chain and essential for the health of the ecosystem. This includes predators like bigger fish, seals, whales and birds who eat the sand lance. The construction of an energy island on such living space could cause a depletion of the sand lance which in turn could affect the rest of the ecosystem and in a worst-case scenario could make the ecosystem collapse in the North Sea. Besides, it could also result in downscaled fisheries and thereby affect local economies in the countries around the North Sea.
The Danish government has already planned a location in the North Sea Section East. This study aimed at testing the planned location against other alternative locations i.e. an adjacent location at North Sea West and the Dogger Bank section further out west in the North Sea to see whether those locations would have less sand lance densities and therefore have less impact on the sand lance population and ultimately the entire ecosystem. Alternative locations were chosen as they have been mentioned in the literature as potential areas for offshore energy development. The Dogger Bank has been mentioned due to its shallow waters (less depth) which makes it cheaper as far as building cost. Another aspect of this study was to find out if an optimal location would result in extra cable cost. A location closer to the Danish shore would be cheaper in cable costs than a location further away from the shore.
An optimal location would be considered highly suitable, locations with less potential would be considered medium to little suitable and a location with no potential and a high sand lance density would be considered unsuitable.
A geographical information system (GIS) was used to find the optimal location in combination with an analytic hierarchy process (AHP), which is an analysis method to support complex decision making. In this case two conflicting goals emerged: an ecological scenario with a focus on protecting the sand lance and an economic scenario with a focus on keeping the cable costs low and maximizing energy production. The purpose of this study was also to find out if and how the results, i.e. an ecological, an economic scenario and an equal weight scenario would differ. An equal weights scenario would have no particular focus i.e. all criteria in the analysis were given the same importance.
The results of this study showed an optimal location in the very same section East (at or near the location planned by the government) in all three scenarios. It also showed that the Dogger Bank section was considered unsuitable in all three scenarios. The reason the East section was considered suitable in an ecological scenario was due to a relatively low sand lance density in that section. In the economic scenario, the East section was also the preferred location as economic factors such as distance to shore and windspeed were given great importance and therefore influenced the analysis and favored the East Section. The Dogger Bank was considered unsuitable in all three scenarios. In the ecological scenario the Dogger Bank was considered unsuitable due to high sand lance density. In the economic scenario, the Dogger Bank was unsuitable due to the long distance to shore and a relatively low windspeed. The equal weights scenario showed a result and a geographic pattern like the economic scenario.
The method of combining GIS and AHP in selecting a location can be used in similar decision situations of conflicting goals where an assessment in different scenarios is needed e.g. location of a factory in an economic versus an ecological scenario, location of a hospital in an economic scenario versus a convenience scenario (easy people access) or location of a military facility in a security scenario (protected and/or hidden) versus an economic scenario etc.
Keywords: Geography, GIS, Energy Island, AHP, Offshore Windfarm, Site Selection, Sand Lance, Ecological Scenario, Economic Scenario, Equal weights Scenario.
Advisor: Marko Scholze
Master’s degree project 30 credits in Geographical Information Sciences, 2024
Department of Physical Geography and Ecosystem Science, Lund University

Thesis nr 181

• author: Bengtsson, Max
• supervisor: Marko Scholze
• organization: Dept of Physical Geography and Ecosystem Science
• alternative title: Finding an optimal ecosystem friendly versus an economic site for an energy island in the North Sea
• course: GISM01 20241
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: Geography, GIS, Energy Island, MCDA, AHP
• publication/series: Master Thesis in Geographical Information Science
• report number: 181
• language: English
• id: 9173925
• date added to LUP: 2024-09-09 09:45:44
• date last changed: 2024-09-09 09:45:44