By Swarna Kesavan
The North Sea has witnessed significant offshore wind power activity in the past few years. With 11.2 GW of offshore wind capacity, the North Sea accounted for 60 per cent of the global offshore wind installed base (18.8 GW) and over 70 per cent of the European offshore capacity (15.8 GW) at the end of 2017.
Offshore wind will provide a significant share of the renewable energy capacity needed by the North Sea countries to meet the Paris Agreement goals. By 2040, the North Sea offshore wind capacity is expected to reach 70-150 GW (and possibly 180 GW by 2045), accounting for around one-fifth of the European Union’s (EU) total power consumption. To achieve this goal, there must be a high degree of planning and coordination among the countries in the region.
Given the experience so far and the future potential, five companies have collaborated to develop a large-scale European electricity system for offshore wind in the North Sea – the North Sea Wind Power Hub (NSWPH). The NSWPH consortium partners are the transmission system operators (TSOs) of the Netherlands and Germany – Denmark’s TSO Energinet.dk, gas infrastructure company Gasunie and the Port of Rotterdam. In May 2018, the NSWPH presented its vision at the Clean Energy Ministerial held in Copenhagen, which was attended by the energy ministers of the largest economies (G20 countries) as well as Denmark, Norway, Sweden, Finland and the Netherlands. The NSWPH’s broad vision is to connect large-scale offshore wind power to a central hub (an artificial island) and create new energy highways and trade corridors among the North Sea countries. The partners have committed themselves to investigating the potential of the vision until mid-2019.
The overall plan is to follow an internationally coordinated roll-out (ICRO) instead of a nationally incremental roll-out (NIRO) to accomplish the green energy transition, making it both feasible and affordable. This is proposed to be achieved through the construction of one or more hubs at a suitable location in the North Sea with interconnectors to bordering North Sea countries. The whole system will function as a hub for the transport of wind energy, an interconnection hub to the connected countries, a working hub for offshore wind developers and a location for possible power-to-gas (Power2Gas – P2G) solutions.
The project – Developers and developments
In June 2016, TenneT developed a vision for building a large European electricity system in the North Sea, based on the hub-and-spoke principle. Subsequently, in March 2017, Energinet.dk entered into a trilateral agreement with the Dutch and German TSOs of TenneT to develop the project. The other two partners joined the consortium in September 2017 (Gasunie) and November 2017 (Port of Rotterdam). The two new partners bring relevant expertise on P2G, as well as port development and land reclamation.
The NSWPH project can be divided into three components – hub and spoke, island and P2G. The modular hub-and- spoke concept is the core of the NSWPH project and serves as an alternative to the current approach of connecting each offshore wind farm radially or directly to the national grids onshore as well as using point-to-point interconnectors. The main elements of this concept are an artificial island, wind farms including grid connection and interconnectors.
Each hub could connect up to 30 GW of wind power comprising 2,000-3,000 wind turbines. The hybrid nature of the hub will increase the efficient utilisation of a connection to the mainland from about 40 per cent (radial) to 100 per cent (hybrid).
The project entails building an artificial island in the North Sea to host the wind power hub at a central location and in shallow waters with optimal wind conditions. The idea is to create a near-shore environment far out at sea. An artificial island can perform different functions such as supporting heavy electrical infrastructure components; providing a base for wind farm installation operation and operations and maintenance (O&M) activities; as well as support power conversion (such as P2G) and storage technologies.
P2G is expected to lead to an improved business case for offshore wind farms connected to a hub as peak power generation could be used for conversion instead of being sold at a low market price or even curtailed due to possible interconnector constraints. This is possible as the cost of energy transmission and long-term storage in the form of gas is considerably lower per unit of energy than if transmitted and stored in the form of electricity.
The power and gas supply systems together could boost the use of hydrogen (as a sustainable solution with numerous applications in industry and transportation) and could potentially be brought ashore through the existing offshore gas infrastructure.
In November 2017, the NSWPH and a group of 30 industry representatives held a session at the WindEurope Conference in Amsterdam to discuss the NSWPH vision and solutions for the future offshore wind and onshore grid challenges. During this meeting, the first findings from detailed studies were also discussed. At least three preliminary studies have been performed so far. These include a preliminary desktop study entailing a quick scan of the geology and ecology in Denmark and parts of Germany; a quick scan of ecological impacts on Dogger Bank in the territorial waters of the Netherlands and in general; and gap analysis ecological monitoring.
The ecological quick scan was based on environmental impact assessments and appropriate assessments for offshore wind farms in the Netherlands and the UK as well as wind areas executed by Royal Haskoning DHV (RHDHV) and case study reports from the Netherlands-based Institute for Marine Resources and Ecosystem Studies.
Dogger Bank (an extensive isolated shoal in the North Sea) was chosen for the quick scan as a possible location for the power hub island as it is a shallow area in a windy region and could serve as the centre of the offshore high voltage grid. Dogger Bank has a water depth of 20-40 metres and its surface area (21,970 square km) can accommodate 110 GW of offshore wind capacity. The bank is almost 300 km long and is located in the British, Danish, German and Dutch parts of the Exclusive Economic Zones. The bank has not yet been designated as a wind energy area in the Netherlands, Germany and Denmark. However, in the UK, part of the area is designated and permits have been granted for four offshore wind farms with a total capacity of 1,200 MW.
TenneT assigned RHDHV to prepare a report on Dogger Bank’s offshore wind capacity. According to this report, the most offshore wind capacity potential is available in the British and Dutch parts of Dogger Bank as these are much larger areas (refer Table).
Once 90 per cent of the oil and gas infrastructure is decommissioned in the coming decades, 11 GW of extra offshore capacity can be developed. Most of the platforms are situated in the UK’s part of Dogger Bank, which means that most of the additional capacity will be installed there.
First results from the preliminary studies carried out by project partners are positive and indicate net socio-economic benefits of interconnectors to a NSWPH with associated uncertainties. An international approach (ICRO) will reduce infrastructure costs significantly (up to 30 per cent as per first calculations) and lead to competitive energy prices.
ICRO development is step-wise and modular, and limits the risks for stranded assets. Through this approach, economies of scale can be achieved through the development of higher capacity solutions (150-525 kV) and the development can be spread over several decades. The step-by-step development makes the solutions flexible and allows integration of future offshore innovations in transmission assets, wind farm design and O&M. Part of the cost reduction is achieved on account of hybrid connections for optimal use of cables under ICRO. Currently, wind infrastructure is radially connected to each individual country. There are separate interconnector cables between countries. The wind connector will combine the wind infrastructure and interconnector in one function.
Additional benefits are anticipated through exchange among energy markets. The NSWPH is modelled as three price areas (the Netherlands, Germany and Denmark) with a copper plate between them (market coupling between the areas) and wind capacity connected to their respective (national) price areas.
A pre-feasibility study assessing energy system indicators and socio-economic trade benefits, excluding capex costs for interconnectors based on the Ten-Year Network Development Plan 2018 (TYNDP 2018) scenarios and renewable energy sources production increases, indicates that socio-economic benefits amount to about Euro 300 million per year in the case of a sustainable transition (ST 2040) scenario and Euro 900 million per year in the case of global climate action (GCA 2040). Under the ST scenario, targets will be reached through national regulation, emission trading schemes and subsidies and by maximising the use of existing infrastructure. GCA is based on the assumption of full speed global decarbonisation and large-scale renewable energy development in both the electricity and gas sectors.
In comparison to a near alternating current (AC) solution (as in the case of the Borssele area in the Netherlands) for offshore wind farms, the NIRO approach to a far offshore solution will result in an over 20 per cent hike in the costs while the ICRO approach will lead to about 7-10 per cent reduction in the levellised cost of electricity (LCOE).
As reducing the total system cost is essential to facilitate large-scale offshore wind, all options to further reduce costs including an artificial island must be considered. The cost reduction potential of the artificial island depends on a balance between functionality and needs. It is necessary to explore the design, functional and location options of the island hosting a wind power hub. The technical feasibility of the islands far offshore has been determined for multiple locations and a detailed feasibility study was conducted for Dogger Bank. This included various aspects such as wave and surge conditions; extreme wind conditions; geotechnical data on subsoil composition for design specifications; evaluation of various layouts; living quarters; runway and its usability under local wind conditions; cable landings and high voltage direct current (HVDC) equipment; harbour; and revetment and sea defence design. Alternatively, a lean island (with minimal functionalities) provides cost-efficient support for electrical infrastructure only and can potentially reduce the LCOE by 10 per cent as compared to the business-as-usual scenario.
Based on the international consultation by the NSWPH, feedback and suggestions from the industry include maintaining high levels of transparency about the assumption to gain legitimacy for the project; undertaking a detailed study of all possible alternatives; being careful not to view the North Sea as the easy option to avoid public criticism; and focusing on integral spatial planning.
The integration of large amounts of variable renewable resources leads to strongly reduced levels of despatchable generation and thus increased use of flexibility options. A higher level of interconnectivity across the North Sea is needed for flexibility options and markets to function. Particularly, cost-efficient flexibility options such as demand response, small- or large-scale storage and P2G will become essential.
The current connection concepts entail increasing costs for far offshore wind farms in terms of construction, maintenance and infrastructure. While the suggested NSWPH concept could help reduce some of the costs, there are several knowledge gaps, which will need to be further studied.
The way forward
The project is at the conceptual and planning stage. In terms of the next steps, based on the ecological quick scans and research questions, a draft proposal will be prepared for detailed feasibility studies. Based on the consultation on the draft, a final proposal must be prepared to initiate further research. The consortium is open to inputs from the industry and willing to join hands with more partners. The consortium is expected to publish a roadmap during 2018, charting the future path.
At the EU level, the visionary NSWPH project has created excitement among policymakers. It covers five important policy dimensions, namely, regional cooperation, internal market, energy efficiency, climate action and innovation, and competitiveness. The cost-benefit analysis of creating an artificial island in the middle of large offshore wind capacity zones needs further detailed evaluation. Nonetheless, the innovative design, if implemented in the manner in which it is being conceived would change the landscape of the electricity industry and open up several opportunities for sustainable development.