Harnessing renewable energy in the North Sea
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Photo Credit: DEME group
As global decarbonization efforts ramp up to combat the impacts of climate change, governments and the maritime industry are increasingly looking towards the offshore sector as a means of producing green energy. The utilisation of ocean space has allowed for the construction of huge wind farms in the North Sea to harness renewable energy. These projects have only grown in tandem with energy needs and technological advances and represent a lucrative market for dredging and engineering companies that support the construction of these projects.
In fact, as of 2020, the largest operating wind power plants in the North Sea have an installed capacity ranging from 300 MW, from the wind farm Thanet built in 2010, to 1200MW, from the Hornsea One built in 2020, both of which were built by the UK. Though 10 years apart it demonstrates the scale at which the industry is now operating at.
Complementary offshore green technology
Goals of a net zero industry have resulted in innovative project ideas to support existing green technologies. Currently, companies are exploring the possibility of energy islands in the North Sea. Energy islands are islands or hubs which would gather electricity from surrounding wind turbines and potentially maximise energy efficiency by producing green hydrogen or storing electricity in batteries. These islands would send the power produced back to shore via interconnectors and have the ability to connect to different countries. If actualised the energy islands would be complementary to offshore wind farms by acting as central platforms for transporting energy rather than using the offshore converter platforms currently used.
Although still in the planning stages, assessments are taking place to determine the costs, practicality, safety aspects, and time frame for construction in anticipation of upcoming Danish and Belgium projects. Construction of the Danish North Sea energy island is expected to start in September 2023, 100km from the coast of Jutland, and construction of the Belgium North Sea energy island is expected to start in 2024, 45km from the coast of Belgium.
The construction of energy islands would support the continued development of offshore renewable energy in the North Sea and would help not only with decarbonisation strategies but could also help limit the potential for energy sources to be used as political tools.
Challenges of building in the North Sea
The construction of these respective energy islands brings forth the possibility of utilising locations which contain large quantities of wind turbines, such as the construction site of the Dogger Bank wind farm, as a way to better connect renewable energy to the mainland.
The Dogger Bank wind farm, which is slated to be the largest wind farm in the North Sea to date, is located more than 100 km off the northeast coast of England at the shallow offshore area of the North Sea and is designed to have a total installed capacity of 3600 MW. Construction activities began in 2020 and are split into three phases, with the first phase expected to be operational in 2023.
The wind farm's location is of significant importance for several reasons. One is that Dogger Bank is an isolated sandbank, within the central to southern area of the North Sea, which extends across the UK, Dutch, German, and Danish exclusive economic zones (EEZ). These territorial boundaries are of particular economic importance as they’re used for commercial fishing grounds, archaeological interests, oil and gas activities as well as marine renewable energy development.
Secondly, the Dogger Bank is notable for being the shallowest part of the North Sea with an average depth of 35m compared to the North Sea’s average depth of 90m. The particular area of the Dogger Bank which is being used for the Dogger Bank wind farm has water depths ranging from 18m to 63m.
Thirdly, the location of the Dogger Bank wind farm is under lease from the Crown Estate as part of their efforts to support the development of an offshore wind market, and the UK government plans of meeting net zero and energy security commitments.
Location is key
Port Consultants Rotterdam conducted a constructability assessment in the Dogger Bank area of the North Sea to assess the construction of an energy island. The assessment cited that the harsh conditions of the North Sea would mean that construction would have to account for weather conditions and safety to mitigate risks and enable high capacity efficient operations.
Wood Thilsted, the company which designed the wind turbine generator foundations for two phases of the Dogger Bank wind farm, took into consideration the condition of the North Sea when designing the monopile foundations. The design of the foundations incorporated a split-level transition piece to allow for safe access to the turbine tower for technicians. The turbine is further supported by the world’s largest offshore wind flange, 8m wide, which strengthens the connection point of the transition piece. SSE Renewables Project Director for Dogger Bank Wind Farm, Steve Wilson, states: “these foundations have been designed for what is arguably the most demanding wave environment to be encountered on an offshore wind farm.”
Wilson’s statement aligns with data gathered by Port Consultants Rotterdam who found that the operational wave statistics of the Dogger Bank area would mean that constructing an energy island at optimum efficiency and the shortest construction schedule would mean avoiding working in the months of December and January which are known to have the most adverse weather conditions of the year.
The North Sea is the current hub for European offshore renewable energy projects with the UK leading the charge by constructing the world's largest offshore wind farm in Dogger Bank. Whilst Denmark and Belgium are venturing into new territory with the planned construction of energy islands. However, it remains to be seen whether the Dogger Bank area will also get the energy island treatment to complement existing construction projects.
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