Illustration showing what Hywind Tampen will look like when floating offshore wind is installed. Copyright: Equinor
Illustration showing what Hywind Tampen will look like when floating offshore wind is installed. Copyright: Equinor
Illustration showing what Hywind Tampen will look like when floating offshore wind is installed. Copyright: Equinor
Illustration showing what Hywind Tampen will look like when floating offshore wind is installed. Copyright: Equinor

Using offshore wind to cut oil and gas emissions

By John Olav Tande

The North Sea is known in Europe for oil and gas activity, fishery, transport and during the last decades, increasingly, offshore wind. To meet their climate targets, Norway and Europe need more renewable CO₂-free power generation, energy efficiency measures and CCS. We need it all, and we need it fast. We are in the middle of an energy revolution.

Offshore wind will be a big part of this revolution. It is an energy source that is abundantly available and can be installed and operated while respecting nature. At FME NorthWind, we carry out R&I to make this a reality, and we do this together with partners in Europe, and with international partners from all over the world.

The North Sea is in many ways the birthplace of offshore wind development. This is where large offshore wind farms are already in operation, and more are in the works. In Europe, by 2050, according to the European Commission goals, one third of the electricity consumption will be supplied by offshore wind. This will make offshore wind the backbone of the European energy supply.

Illustration showing floating wind turbines at sea.

Offshore wind is a giga opportunity.

To make this a reality, not only must we develop offshore wind farms as is done today, but we must also develop an offshore transmission grid to transport the energy to the consumers, and we need solutions that ensure a reliable and safe supply to the consumers even when the wind is not blowing. Hydrogen, energy storage and other flexibility solutions together with wind farm control solutions are key to achieve this goal.

In Europe, about 25 GW of offshore wind capacity is installed currently. Globally, this figure is at about 35 GW. Less than 1 % of this is floating wind. Meanwhile, 80 % of the global wind potential is at water depths deeper than 60 metres, so the development of floating wind is essential to realise this huge potential.

Bottom-fixed wind can currently be developed for about 50 EUR/MWh, whereas floating wind costs about 100 EUR/MWh. There is no reason that floating wind should be more expensive. In my opinion, floating can be developed to be cost-competitive with bottom-fixed. This can be achieved through deployment, research and innovation. Our goal is that together with industry, new floating wind farms will be developed at a cost of 50 EUR/MWh by 2030, assuming a suitable location.

This is important. Offshore wind is essential to reach climate goals, secure affordable energy supply and enhance a competitive industry.

Offshore wind is a big industry opportunity. In Europe alone, investments in offshore wind towards 2050 will be in the range of 1000 billion EUR to give 450 GW of installed capacity, supplying about one third of the European electricity demand.

Today, large offshore wind farms are being developed in the North Sea. 25 GW are already in operation, and more are in construction, but we need to speed up the pace.

In the map shown below, I have marked two new Norwegian fields that are now open for development: Sørlige Nordsjøen 2 (SNII) and Utsira Nord (UN). They are slated for development og 1.5 GW bottom-fixed and 1.5 GW floating wind, respectively, and will supply about 10 % of the Norwegian electricity consumption when they start operations. Dogger Bank, in the UK, is currently the world’s largest wind farm in development. It has a total capacity of 3.6 GW and will be connected to shore in the UK with two HVDC lines.

Map of the North Sea showing the two Norwegian fields that are open for development of offshore wind, as well as the Dogger Bank fields, in the UK.

In the map, you can also see a lot of oil and gas platforms. Most of these are operated with gas turbines on the platforms, and they emit CO2 amounting to about 25 % of the Norwegian emissions (which total approx. 50 Mton/year). For Norway to reach its climate targets, it is vital to cut these emissions.

This can be done by offshore wind, and I will argue that it constitutes a great opportunity to accelerate the development of floating wind. This is because the oil and gas platforms are for the most part in relatively deep waters, suitable for floating wind. Floating wind farms can be built near the platforms to supply the energy needed, thereby reducing the use of gas turbines and cutting CO2 emissions. There are three options, illustrated in the figure below.

Offshore wind to cut emissions from the NCS: Option 1 - Isolated system with offshore wind and gas turbines (Fuel savings: < 40%); Option 2 - Isolated system with offshore wind, energy storage and gas turbines (Fuel savings: < 80%); Option 3 - Offshore wind and power exchange to shore (Fuel savings: 100%).

The first (leftmost in the figure above) is to use offshore wind connected to the oil and gas platforms and operated in parallel with the gas turbines. That is what will be done at Hywind Tampen, which is being built as we speak and will be ready for operation by end of this year. It will be an 88 MW wind farm that will save about 200 000 tons of CO2 per year. Had the wind farm been larger, it could have saved a bit more, but as long as the gas turbines need to be in operation to balance the generation against the demand, it is difficult to save much more than 40 %.

If we add energy storage such as batteries, pumped subsea storage or hydrogen (the option in the middle, in the figure above) additional savings can be achieved. The energy storage would need to be quite large to cope with possible long periods of calm conditions, so again, savings are limited, maybe up to 80 %, depending on system design.

A better option, to achieve 100 % savings of CO2 emissions, is to connect the platforms to the grid (this is the rightmost one on the figure above). Then the offshore wind supply will be balanced with the connection to shore, and the system can be operated without the gas turbines. If or when the oil and gas activity comes to an end, the offshore wind farms can continue to supply clean energy to the grid.

I suggest three steps for a green transition:

  • Reduce CO2 emissions from oil and gas activity through use of offshore wind and connection to shore, and possibly other solutions
  • Natural gas can be converted to blue hydrogen with CCS
  • Offshore wind can continue to supply clean energy even after the oil and gas activity has stopped

The North Sea constitutes an ideal springboard for the green transition. Deployment, research and innovation is essential for success. It is urgent! CO2 emissions must reach zero before 2050. And we need to achieve all this in a sustainable way, which means:

  • Recognising that nature has its own value
  • Engaging the public
  • Employing knowledge-based development

This article is based on a presentation given on 29 March at the NTNU Energy Transition Conference (fast forward the video to 4:17:00 to see the presentation). You can read more about the North Sea as a springboard for the green transition in the document of the same title, presented last year at the UN Climate Summit COP26.