Connecting the dots

While decommissioning is often seen as a challenge, to the Dutch it is also an opportunity. Elaine Maslin reports.

The North Sea Wind Power Hub concept. Images from TenneT.

The Dutch don’t have the largest patch of the North Sea by a long shot. They do however have 160 platforms, mostly small and in shallow waters, and, despite being late to embrace offshore wind, a fast-growing fleet of offshore wind farms.

These could be seen as colliding worlds, one – offshore gas production – on the wane and the other – offshore wind – set to grow. However, a number of Dutch activities are looking to see how these two industries could support each other, and indeed usher in other technologies, creating interconnected gas and power production systems alongside carbon capture and storage (CCS).

Nexstep, National Platform for Reuse & Decommissioning, was launched during the Offshore Energy Exhibition & Conference in Amsterdam. The body, led by state-firm Energie Beheer Nederland (EBN), and industry body NOGEPA, sees “an opportunity to reuse existing elements to complement renewable investments before their eventual safe and efficient decommissioning.”

There’s also the North Sea Wind Power Hub, a concept developed by grid operator TenneT, which would see an artificial island built in the North Sea in 2030-50. This would act as a hub to connect far offshore wind farms in the Dogger Bank area of the North Sea, close to where the maritime borders of the Netherlands, Germany, Denmark, and the UK meet. TenneT proposed the concept in 2016, and this year signed a trilateral agreement between its Dutch and Germany business units, alongside Denmark’s Energinet.dk and most recently Dutch gas network firm Gasunie.

The hub, comprising “Power Link Islands,” with interconnector cables to countries in the North Sea, would support up to 100GW of wind farms, and hydrogen production for large scale transport, power buffering/storage.

Meanwhile, there’s the North Sea Energy Challenge (NSEC), a group comprising the Dutch Wind Energy Association (NWEA), the Nature and Environment Foundation, VNO-NCW, NOGEPA, Dutch research organization TNO and TenneT. NSEC is looking at joint research into possibilities for electrification of production platforms, joint innovation for system integration, power2gas, energy storage, etc.

All options should be considered, suggests Rene Peters, director of gas technology at Dutch research organization TNO Energy. This includes the potential to reduce emissions from existing platforms by electrifying them, developing gas to power, or power to hydrogen, and introducing CCS.

“Intensive use of the North Sea leaves little space,” Peters says. “Five percent of gas produced is used for power generation to compress gas to send it to shore. There are increasing CO2 and NOX [emissions] constraints. We also have to transport GWs of wind electricity onshore. How can we balance, store and transport it all economically? And is there a role for hydrogen?”

The Netherlands is targeting building out some 4.5GW of offshore wind power over the next 10 years (the largest turbines are currently rated at up to 8MW a piece). Meanwhile, an estimated US$13.90 billion (€12 billion) will need to be spent to decommission Dutch hydrocarbon platforms and pipelines as they come to the end of their lives in the Dutch North Sea.

“One of the challenges passed to us is determining the value of reusing this infrastructure to the benefit of a future energy system,” Peters says.

In the short-term (up to 2023), Peters suggests electrifying platforms, to reduce emissions. This could use power from nearby wind farms. While doing this for all Dutch platforms might not be feasible, the 10 largest consumers of power could be targeted. “This would cut CO2 by a mega-tonne a year,” Peters says. “There would also be less maintenance needs,” he adds.

_{The North Sea Wind Power Hub concept.}  

“It is clear the oil and gas sector has to reduce emissions. It means current use of gas to produce electricity on platforms is not useful anymore. Electrifying them is probably the best option.” There’s already one platform powered with electricity from shore in the Netherlands and more in Norway, which has had a policy of power from shore in place for a number of years.

Mid-term (2023-2030) could see offshore power-to-gas (hydrogen), for “peak shaving,” i.e. making use of/storing the excess power when it’s windy, and gas-to-wire, for power balancing (producing power from gas when it’s not windy), with local CCS, as well as CO2 storage from other sources.

With increasing power coming from wind, how to balance the system will be important, Peters says. While this isn’t such an issue – wind farm operators currently enjoy fixed prices for their power – when they are exposed to market prices, there will be a need to look at how to balance out power production with the likes of energy conversion or storage.

“The need for storage and balance will be huge,” Peters says. “For me, storage offshore with batteries is a no go.” Peters suggests that a significant scale pilot should be set up to demonstrate offshore power to gas conversion, as well as balancing and storage options and maybe also feeding hydrogen into the grid. “We need to show this can operate remotely or with minimum maintenance costs.”

Currently, hydrogen is produced using a steam process, and natural gas, but electrolyzer type hydrogen producers have been developed. These cost more and haven’t been used offshore yet, he says.

“When you are further offshore, molecules are cheaper to transport than electrons,” Peters says. “Hydrogen is a way to store power as well. There is a conversion loss, but, industries in Rotterdam and Groningen use hydrogen a lot already, from gas in these cases.” Power to hydrogen technology has been scaling up and its foot-print getting smaller. It could be deployed on out-of-service platforms or could be used as part of TenneT’s energy island concept, Peters says. On site gas-to-power (gas-to-wire), could also be considered, he says.

Power-to-gas could also alleviate the possible “domino effect” of key pipeline infrastructure being decommissioned, which would otherwise leave fields stranded.

Longer term, existing infrastructure could be reused to house offshore wind substations, synthetic natural gas could be produced and the existing gas grid used to transport it and or hydrogen. Ultimately, the whole grid, with each element, will need to play a role in energy storage, transport and distribution, where each part can offset the other, he says.

TNO plans to test the impact of transporting hydrogen in existing natural gas pipelines, there being the potential for hydrogen stress cracking. Transporting the product at a lower pressure could reduce this issue, Peters says, adding that the biggest concern isn’t the pipelines, but the flanges, compressors and valves up and downstream of the pipelines.

The idea behind the North Sea Wind Power Hub is to create a large connection point for thousands of future offshore wind turbines. TenneT envisions that a total capacity of possibly 70-100GW could be connected to one or more so-called Power Link Islands. Having these hubs would reduce the cost of having many power export cables to shore. Instead power would be distributed from the hub via DC connections to all countries bordering the North Sea: the Netherlands, Denmark, Germany, the UK, Norway and Belgium, with the transmission cables simultaneously acting as interconnectors between these countries, enabling them to trade electricity. TenneT says, subject to a final investment decision, a Power Link Island could be developed by about 2035.