Offshore projects designed to use renewable energy to produce hydrogen from seawater are moving forward with the North Sea set to lead the charge in research and development.

The ground-breaking technology could enable offshore oil and gas infrastructure to use energy derived from hydrogen, which when used to generate electricity emits only water vapour as a waste product, allowing operators to drastically reduce carbon dioxide emissions related to production.

Researchers are also looking at possible ways the hydrogen produced offshore could be stored and made available to other users such as hydrogen-fuelled vessel operators.

Two North Sea projects announced recently are preparing pilots to prove up the nascent technology.

UK-based oilfield services giant TechnipFMC is collaborating with Norwegian partners on a project known as Deep Purple that includes an innovative hydrogen subsea storage system and a topside hydrogen production unit.

In a separate project, operator Neptune Energy is working with research organisations on a pilot that will supply an offshore platform with power generated by hydrogen produced from seawater.

Both projects will use renewable electricity — in the Deep Purple project, from offshore wind farms — to provide the energy needed to separate hydrogen from oxygen in seawater, and fuel cells to convert the hydrogen back to electricity.

On demand

The Deep Purple project’s subsea storage system will make the produced hydrogen available to generate electricity on demand when the wind is not blowing.

The basic technologies involved are established, but Deep Purple will be the first to test subsea hydrogen storage, says project manager Marit Mork of TechnipFMC, who has a background in subsea processing and flow assurance.

“This is based on existing technologies — both the storage system and fuel cells are already commercialised onshore,” Mork says.

The main technology challenge involved, Mork notes, is to control and optimise the wind power relative to hydrogen production and re-electrification to create an integrated system. The project’s main objective is to deliver a stable power supply to oil and gas installations, she says, but the Deep Purple team is looking at a concept that could make hydrogen available to the maritime sector in Norway as hydrogen-fuelled vessels become more prevalent in the country.

“This sector would need hydrogen and we are using our subsea competency to store and distribute it on the seabed,” Mork says. Seabed hydrogen storage has several benefits, not least the safety aspect of getting large volumes of the flammable gas away from busy ports, where space to set up safety zones may be limited.

It also could address intermittence issues in wind power generation, providing hydrogen fuel when winds are quiet and a place to send hydrogen production when high winds threaten to overwhelm the power grid by producing too much electricity — a problem that now often requires turbine operators to take wind farms offline.

The Deep Purple scheme is a collaboration between TechnipFMC, Norway-based research organisation Sintef, and the industry alliances Energy Valley and Hub for Ocean.

The idea came out of a June 2016 workshop hosted by the Research Council of Norway to solicit “new ideas for the ocean space” from various industry participants, Mork says.

“The idea of subsea storage for hydrogen came up on a Post-it Note,” she recalls.

The Deep Purple team took first prize and the Research Council funding, with an equal contribution from TechnipFMC, got the project under way.

Screening

The first phase entailed a feasibility study and screening of the main technology elements.

The current phase, for which the team received additional Research Council funding, includes a concept study as well as a degree of technology qualification and business development.

The partners hope to wrap up this second phase in early 2020 and move towards a “medium-size, maybe 100-kilowatt type of pilot, not completely offshore”, Mork says, with an eye to full-scale deployment by the middle of the decade.

“Keeping the speed up, we think we can offer this to the offshore environment in 2025,” she says.

The system will be modular, meaning it can be scaled up or down as energy needs require.

The team initially is targeting projects in water depths of 100 to 300 metres, which would include much of the Norwegian continental shelf.

A pilot will address some of the maintenance challenges related to movement, saltwater environment and humidity.

“We have to ensure that we are able to install and operate electrolysers and fuel cells offshore,” Mork says.

“As with other subsea technologies, there are qualifications to be made on the materials side,” she adds, including situations involving the re-use of existing infrastructure.

Mork says the typical platform would require 50 to 60 megawatts of wind power.

“But it highly depends on your ambition to reduce CO₂ emissions,” she notes. “We are not targeting 100% renewables — that would require too much energy storage and wind power. We think it is more realistic to set targets to 70% to 80% CO₂ reduction, which is still a lot, and to have a moderate system.”

The name was inspired by the colour that corresponds with the emissions spectrum of the hydrogen atom that has a wavelength of 410 nanometres, Mork explains.

“We were thinking about how to expand on that for a name” she says, adding that “we were inspired by the rock band Deep Purple”.

Scaling up

While talk of producing hydrogen from seawater has been circulating for years, greater offshore wind capacity and advances in electrolysis and fuel cell technology have encouraged a handful of companies to enter the segment.

“We are not alone in looking at offshore hydrogen production,” Mork says.

However, the subsea storage element could lend itself to additional maritime applications.

“With Deep Purple, we are just storing it locally and regenerating back to power,” she says. “But we can see that the same system could be used to tap hydrogen for other purposes.”

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