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Boundary Pushers: The offshore meshed grid challenge

In this installation of the Boundary Pushers series we speak to industry experts about offshore grid challenges.

A European vision for a North Seas offshore meshed grid was launched back in 2010, planning for future large volumes of offshore wind generated electricity to be transmitted safely, reliably and at low cost to shore. Combining the offshore wind project links with maritime interconnectors for cross-border electricity transmission increases cable use and makes economic and environmental sense.

But a meshed grid challenge is multifaceted and progress is slow.

Firstly, interconnectors on their own can be very lucrative but only when there aren‘t too many.  The 1GW BritNed interconnector earned profit in 2016 of €111 million on revenue of €222 million, a profit margin of 50%.

But each new interconnector will chip away at such profits because, albeit regulated, the business case is currently built on electricity price differences between the connected markets: the more interconnectors that are built, the smaller the price difference between the markets connected, and the worse the business case. Without political incentives, interconnector companies may resist building more.

Secondly, why complicate a business already performing well by making interconnectors multiple-purpose?

Seven new interconnector links from the UK are planned to be installed by 2022 but all are point-to-point transmission links, according to UK regulator Ofgem. Only one, the 1400MW "FAB Link" UK-France project, may eventually be connected to an offshore tidal energy project.

Such multiple-purpose "leads to more involved technical arrangements on interconnector use and brings regulatory complications that need to be solved," noted Benedikt Unger, interconnector expert at Pöyry Management Consulting.

"The additional challenges often appear to outweigh the potential gains, and coordination between interconnector owners and offshore project developers could be difficult," he said.

Connecting an offshore project to an interconnector "is still unknown territory – there is little evidence and experience on the regulatory or the technical side. Regulators and organisations in many countries are still working on how to share assets of an interconnector with offshore wind farms," said Unger.

"Several key issues need to be overcome, from support structures for offshore generation to transmission connection regimes," he continued.

Transmission connection hitches have dogged the pilot Kriegers Flak combined grid solution where Danish and German offshore wind sites are connected to create a maritime interconnector.  

Most of the €150 million project grant from the European Energy Programme for Recovery (EEPR) is spent on a "back-to back" AC/DC/AC converter to synchronise eastern Danish electricity with the German system. Without the grant, the business case of the project would not be positive, according to Danish transmission system operator Energinet.

A second pilot project has received European support. Cobracable, under construction between the Netherlands and Denmark -- which on its own has a positive business case -- has been awarded €86.5 million in EEPR funds "relating to the possibility to connect new offshore wind farms to the cable as a first step towards a meshed North Sea offshore grid".

But  "there are no ongoing or approved plans for connecting a project to the Cobracable yet," according to Dutch TSO Tennet, which is partnering with Energinet.

"When a development requests to connect to the Cobracable a review will be conducted to see whether a connection to shore or on the Cobracable is most beneficial on a socio-economic level," Tennet said.

"The EEPR grant is a recovery grant provided in the economic crisis period to ensure progress and continuation of the project and Cobra is technically ready to connect a windfarm. But many regulatory and legal items need to be solved between the involved countries. To this end, several studies are running under the Cobracable project," said Tennet.

Integration

With a look towards the future, smarter grid infrastructure and cooperation is essential. MHI Vestas CEO Jens Tommerup, said offshore wind projects "have to be much more integrated into the grid, and having integration of bigger energy markets where you have more wind will make this much easier.’’

As large scale deployment of offshore wind will be needed to help Europe meet its Paris climate commitments, the meshed grid concept could gain traction.

Some 180GW of offshore wind will be needed in the North Sea region by 2045 compared with some 10GW now, with another 50GW spread across the Baltic, Irish Seas and Atlantic Ocean, according to Michiel Müller, grid expert at consultants Ecofys, a Navigant company.

Also by 2045, there will likely be 50-80GW of interconnector capacity across the North Sea compared with 3-4GW now.  Some of these links will have a hybrid function by also transporting some of the 180GW of offshore wind, he predicts.

Coordinated expansion of transmission links into a meshed North Sea grid -- supported by mechanisms that secure anticipatory investments, and with some of the interconnector capacity having hybrid use  -- would contribute to cost reduction and efficiency, Müller said.

"This is an international challenge that no country can solve only by itself, so cross-border cooperation and international alignment are crucial," he said.

Müller expects the transition to a new, more internationally coordinated roll-out of offshore wind, "to ideally start from about 2023, the point from which the pipeline of offshore wind projects and committed national targets are currently uncertain."

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In this nine-part series, Windpower Monthly and MHI Vestas explore how the industry is driving down the cost of offshore wind energy through competition, collaboration and innovation.


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