Through exploring the feasibility and possibilities of the North Sea Wind Power Hub, the consortium has achieved many interesting findings. These are described in six concept papers. Together, the concept papers tell one story: from the challenge to meet the Paris Agreement, through the solution building on the modular Hub-and-Spoke concept, to the next steps required to meet the Paris Agreement timely and in a cost-effective manner.
Concept paper 1: the challenge
Reaching climate/energy targets in an effective timely manner
One thing is certain: the transition of the North Sea countries to a low-carbon society requires swift and massive changes in the energy system. Today’s energy use is largely fossil fuel based, resulting in significant carbon emissions. The renewable energy share in the EU is below 20%. In other words: the challenge for the energy system is enormous.
Decarbonising the power sector is generally considered to be a first step, as it is cost effective, has significant impact on CO2 emission reduction and is considered possible well before 2050. Offshore wind energy has a major potential for cost-efficient decarbonization, as cost levels have declined rapidly evidenced by new offshore wind projects with limited subsidies. However, deployment rates need to accelerate significantly, which requires a stable market framework and collaboration efforts from suppliers, developers and system operators to keep progress. A concerted action and cooperation across all North Sea stakeholders is required now.
Concept paper 2: the vision
The Hub-and-Spoke concept as modular infrastructure block to scale up fast
To facilitate the energy transition, the modular Hub-and-Spoke concept of the North Sea Wind Power Hub can be an important solution. This concept consists of modular hubs in the North Sea connecting offshore wind farms through interconnectors to bordering North Sea countries. It facilitates sector coupling through power-to-hydrogen conversion. The Hub-and-Spoke concept ensures a modular build-out approach that can start development today without having to rely on cutting edge innovation to reach sufficient maturity and reliability in fields such as DC grid protection strategies.
The modular Hub-and-Spoke concept in an internationally coordinated roll-out brings forward several key benefits:
- Higher utilization and lower costs through combined transmission and interconnection
- Optimised roll-out and connection of offshore wind areas through international coordination
- Providing flexibility to the energy system by facilitating sector coupling
- Modularity, adaptability and scalability
The consortium is well placed to develop and operate modular Hub-and-Spoke projects, and to advise on the techno-economic and operational impacts of the energy transition on the energy system. Given the significant lead times and scale that are required to realise the projects that make the energy system compatible with the Paris Agreement towards 2050, it is crucial to act now.
Concept paper 3: Modular Hub-and-Spoke: Specific solution options
Case studies have demonstrated technical feasibility
The Hub-and-Spoke concept needs to be translated into feasible project solutions. A conceptual design of a Hub-and-Spoke project depends on many factors including:
- Location and physical environment
- Proximity and capacity of offshore wind farms that the hub is required to support
- Final energy demand requirements and transmission capacity and special restrictions at onshore connection points
- Interconnection requirements of surrounding countries
- And required permitting and commissioning timelines of the Hub-and-Spoke projects
At this moment there is a lack of concrete transmission asset project commitments, spatial planning coordination and a clear and steady roll-out of offshore wind deployment beyond 2030. This introduces uncertainty as to which technical option of the Hub-and-Spoke concept is favourable. Considering this uncertainty, the consortium investigated different technical options to demonstrate technical feasibility of the concept. The Hub-and-Spoke concept has been demonstrated feasible for different locations, sizes and configurations.
From a techno-economic perspective an optimal hub size is in the range of 10-15 GW of connected offshore wind farm capacity. Hub structures can be based on different foundation types: sand island, caisson island and platforms, using a jacket or gravity-based structure as foundation. Island-based foundations can enable larger scale interconnection hubs at relatively lower costs. However, the smaller platforms can reduce environmental impact, planning risk and construction timelines.
Different hub configurations were investigated by the consortium: all-electric transmission, fully hydrogen and combined electricity and hydrogen transmission. Also, four locations were assessed by the consortium, to test location specific conditions on hub design. The desktop studies found that a technically feasible solution could be designed for each of the physical conditions encountered at the four locations.
Concept paper 4: The benefits
The modular Hub-and-Spoke concept has substantial societal benefits and thus the potential to incentivize all involved stakeholders
The modular Hub-and-Spoke concept, as a building block in a step-by-step and international coordinated roll-out, has multiple benefits over a national and incremental approach. First of all, cost savings can be made. The Hub-and-Spoke concept taps into infrastructure synergies by merging offshore wind farm transmission assets and interconnector assets. Independent wind farm connections are usually only utilised up to a capacity factor of approximately 50% due to the capacity factor of offshore wind farms. Interconnectors are can be utilised to a larger degree. By combining these asset types, the utilisation of individual connections could increase significantly to 65%.
In addition, a hub-based wind farm transmission concept can reduce costs compared to radial platform connections. This is due to benefits of scale by using e.g. island-based foundations and reduced operational expenses. The following figure gives an overview of the cost reduction potential for the Hub-and-Spoke concept as found in different assessments.
Benefits for society
The Hub-and-Spoke concept offers multiple benefits for society. Increased offshore wind deployment and interconnection levels between North Sea countries result in reduced electricity prices and emissions through improved system integration of renewables. A cost benefit analysis conducted by the consortium found that connecting 12-24 GW of offshore wind capacity in the North Sea – through an all-electric Hub-and-Spoke concept – would increase social welfare by approximately €1.0-1.7 billion per year for the whole of Europe by the year 2040, compared to radially connecting these offshore wind farms (without interconnections). In addition, the increased interconnection levels reduce the amount of required dispatchable (fossil) power, resulting in a reduction of CO2 emissions of approximately 4% for the power sector the whole of Europe by 2040, for a 24 GW hub.
Concept paper 5: requirement to develop
Ensure industry can progress
In order to proceed with the Hub-and-Spoke concept, changes are needed in policies, regulatory framework and energy market design. The Hub-and-Spoke concept with combined wind farm connection and interconnection functionality – and likely with P2X conversion – is shifting the paradigm for energy infrastructure development. It requires a reconsideration of policies, regulatory framework and market design to ensure stable market conditions, and enable anticipatory investments
and timely development of supply chains and innovation. Also, practical standardisation issues such as DC voltage levels require alignment. The current limitations of the regulatory framework for Hub-and-Spoke type of projects are related to:
- Time horizon – typically 10 years for binding grid planning processes, while large infrastructure projects require at least 10 years to develop and construct, will show benefits only in decades after and require anticipatory investment to bring value.
- Cost benefit analysis framework to assess the value of these projects are not (yet) equipped to handle hybrid assets or strongly sector-coupled projects.
- Assessment is largely project based, with only assessing value of isolated projects on a system.
It is conceivable to develop a first Hub-and-Spoke project within the current regulatory framework and market design, but reconsideration is required to properly incentivise stakeholders in the long term. Focus should be on reshaping the regulatory framework and market design such that it properly incentivises all involved stakeholders in the longer term throughout the energy transition. This process could result in voluntary agreements between stakeholders, or memoranda of understanding, but most likely intergovernmental agreements are required to conclude on these decisions for a first Hub-and-Spoke project. The consortium has engaged with more than 10 leading and influential OWF developers to get feedback. The industry finds that taking a regional approach to planning new offshore wind assets across the North Sea would have considerable benefits, including to the North Sea Wind Power Hub concept.
 P2X includes power-to-gas (mainly H2 as well as methane) and other options (such as fuels, feedstock, food, oxygen, residual heat, etc.)
Concept paper 6: requirements to build
Post-2030 planning is needed now
Preparing for an internationally coordinated roll-out in a robust stepwise approach requires clarity on spatial development areas for energy infrastructure beyond 2030, regardless of the technical options selected. It is important to get timely directions from policy makers on spatial planning given the significant lead times for these types of infrastructure and further increasing offshore wind energy deployment rates foreseen after 2030.
For a first Hub-and-Spoke project to be operational in the early 2030s, a formal project decision is needed in the early 2020s, implying specific national post 2030 renewable targets (incl. offshore wind) by 2020. This would allow for national onshore and offshore grid planning to be finalised by 2021. This timeline highlights the need for early action to allow for a development and realisation of the project.
The available offshore area in the southern part of the North Sea would allow for a total offshore wind capacity of only 50-90 GW (including the already operational and planned areas up to 2030), depending on the wind farm capacity density. Therefore, an exclusion strategy of offshore areas will likely not allow for a full deployment of any conceivable future energy system. Multi-use of offshore areas and using a long-term perspective must be seriously considered to unlock the cost reduction potential of an internationally coordinated approach, and ensure sufficient area is available.
Multi-use in the North Sea can impact many stakeholders and will have different impacts on the costs of the offshore wind roll-out. A study sought to identify a first order cost impact of multi-use in offshore areas that currently have a specific use such as nature or fishery. The study identified areas which could be added to the offshore wind roll-out based on their total cost level (incl. costs for multi-use) to ensure sufficient offshore wind deployment. Next to environmental and techno-economic studies, the consortium has specifically engaged with NGOs to consider their input on the Hub-and-Spoke concept. To address the feedback from NGOs the consortium has introduced an additional “investigative location” to its techno-economic analysis of main drivers for the design of a Hub-and-Spoke project. Structured and focused discussions are needed between policy makers, grid operators, market parties and NGOs to define technology specific renewable targets, spatial planning and grid planning for the North Sea countries post 2030.