As wind energy becomes increasingly important to European energy supply, more and more interconnections need to be built between offshore windfarms and onshore grids. A meshed offshore transmission grid connecting offshore windfarms to land could provide significant financial, technical and environmental benefits to the European electricity market, it is claimed, and with this in mind, a four-year European research programme got underway earlier this year that will result in the development of an offshore grid development plan for 2020 and beyond, including the regulatory and financial framework – and the technology – that will be required.
The organisations behind the research project note that, in order to unlock the full potential of Europe’s offshore resources, network infrastructure is urgently required linking offshore windfarms and onshore grids in different countries. High voltage direct current (HVDC) technology is envisaged, but the deployment of meshed HVDC offshore grids is hindered by the high cost of converter technology, the lack of experience with protection systems and fault clearance components and as yet immature international regulations and financial instruments. The project will, it is hoped, overcome these barriers by development and demonstration of new technology, a regulatory and financial framework and an offshore grid deployment plan for 2020 and beyond.
Some commercial HVDC projects have already implemented point-to-point connections and point-to-point and multi-terminal deep offshore grids, but meshed offshore grids linking several offshore windfarms with onshore grids in different countries and with other available generation resources are urgently required to provide additional flexibility, efficiency, security and market access to offshore wind resources.
However, the development of just this kind of highly flexible, fault-tolerant grid has been delayed by a number of barriers, not least the lack of agreement among operators and manufacturers on architectures, control structures and interfaces to ensure interoperability and multi-vendor compatibility of equipment, a lack of market rules and revenue streams allowing the build-up of a suitable financial package (combining innovation actions with European debt instruments and financing coming from other sources, national, regional or local), permitting and environmental compatibility, and operation and management of these grids from legal, technical and market points of view.
If successful, it is hoped that the project will accelerate the deployment of meshed HVDC offshore grids, with particular emphasis on Northern Seas partner countries, before 2020; ensure that the technology will be ready for deployment in other regions in Europe for all transnational corridors defined in the trans-European energy infrastructure regulation or be compatible (plug-and-play) with other upcoming technologies (such as ocean energy, solar energy and geothermal energy as soon as these technologies are ready for similar capacities); ensure plug-and-play compatibility of all relevant equipment of the key suppliers; and prepare for other priority infrastructure projects identified under the trans-European energy infrastructure regulation.
The seven-year research project – PROgress on Meshed HVDC Offshore Transmission Networks or PROMOTioN – has secured €39 million in funding from the EU and aims to develop three key technologies:
- a low cost offshore diode rectifier
- a multi-supplier HVDC grid protection system
- new types of HVDC circuit breakers.
Alongside the technical work, a regulatory and financial framework will be developed for the co-ordinated planning, construction and operation of integrated offshore infrastructures, including an offshore grid deployment plan or ‘roadmap’ for the future offshore grid system in Europe.
The Dutch transmission system operator (TSO) TenneT will carry out the PROMOTioN research programme in collaboration with 35 leading players in the field of HVDC transmission grids, ranging from TSOs and universities to multinational corporations. A series of stakeholder workshops and events will be organised during the project phase to discuss the various technological and regulatory approaches. Currently, PROMOTioN is the largest energy project in the EU’s Horizon 2020 research programme.
Currently, the high cost of converter technology and a lack of experience with protection systems and fault clearance components hamper the deployment of meshed HVDC offshore grids. In addition, the deployment is hindered by limitations inherent to existing European regulations for the purpose of developing cross-border offshore infrastructures, national legal and regulatory barriers and financing issues.
Low cost diode rectifiers for offshore converters are seen as one of the keys to the future development and implementation of meshed DC grids. The concept is ground breaking in as much as it challenges the need for complex, bulky and expensive converters, reducing significantly investment and maintenance cost and increasing availability.
As highlighted above, the second key technology is an HVDC grid protection system that will be developed and demonstrated utilising multi-vendor methods in a full-scale multi-terminal test environment. This multi-vendor approach will, it is anticipated, allow DC grid protection to become a ‘plug-and-play’-type solution. The third technology pathway will, for the first time, demonstrate the performance of existing HVDC circuit breaker prototypes to provide confidence and demonstrate technology readiness.
Marie Donelly, director of renewables, research and innovation, energy efficiency at DG ENER, said, “There is great potential in the Northern Seas to deliver significant quantities of clean energy, helping us both to decarbonise our economy and to increase the security of our energy supply. Northern Seas offers unique opportunities for co-operation and to deliver cost reduction to the offshore energy systems. We think that an offshore grid in the North Sea could become a flagship project for regional co-operation as foreseen by the Energy Union.”
Elisabeth Harstad, CEO DNV GL – Energy, said that combining new HVDC technology with existing systems could be instrumental in bringing large-scale renewables into the grid and ensure that a future-proof grid is affordable, reliable and sustainable.”