Floating offshore wind turbines far out in the North Sea will convert seawater to ‘green’ hydrogen that will be pumped ashore and used to heat millions of homes, under an ambitious plan just awarded UK government funding.

Deployment of a 4GW floating wind farm in the early 2030s at an estimated cost of £12bn ($14.8bn) could be the first step in the eventual replacement of natural gas by hydrogen in the UK energy system, claimed Kevin Kinsella, director of the Dolphyn project for consultancy ERM.

ERM – which is working on Dolphyn with the Tractebel unit of French energy giant Engie and offshore specialist ODE – plans to integrate hydrogen production technology into a 10MW floating wind turbine platform, enabling each unit to import seawater, convert it to hydrogen and export the gas via a pipeline.

If you had 30 of those in the North Sea you could replace the natural gas requirement for the whole country.

Deployment of hundreds of the floating platforms would be able to tap into the excellent wind resources far out in the North Sea, way beyond the depths accessible to fixed-bottom foundations, Kinsella told Recharge, estimating that a 4GW floating wind farm could produce enough hydrogen to heat 1.5 million homes.

“If you had 30 of those in the North Sea you could totally replace the natural gas requirement for the whole country, and be totally self-sufficient with hydrogen,” said Kinsella.

ERM in August received £427,000 under a UK government support plan for promising hydrogen technologies. That will be used to develop a prototype unit for deployment off Scotland using a 2MW turbine from MHI Vestas and the WindFloat platform, designed by floating wind specialist Principle Power and already successfully tested off Portugal, Kinsella added.

It plans to have the 2MW prototype ready for a final investment decision by 2021, at which point ERM hopes a major energy player – “an Engie or a BP or a Total” – will back the project to take it forward to deployment by 2023, with a full-scale 10MW version in the water in 2026.

The Dolphyn team is integrating into the floating turbine platform the systems needed for water intake, desalination and conversion of water to hydrogen via proton exchange membrane (PEM) technology.

The gas will then be exported under pressure via a flexible riser, before joining the output of other turbines to be pumped to shore via a trunkline. Kinsella said the project team is talking to a “major oil company” about repurposing an existing pipeline for hydrogen export.

The floating wind-to-hydrogen turbines would be completely independent of the power grid – a major contributor to cost reduction Kinsella, said. “Once you get a long way offshore it’s the electrical infrastructure that dominates the costs.” They will be equipped with an on-board energy storage unit to make them self-sufficient, with the ability to restart the turbine from a standstill.

Generating ‘green hydrogen’ – completely produced via renewables – competitively at scale is one of the big challenges before it can assume a key role in the energy transition. Pilot green hydrogen projects currently operate at five to ten-times the cost of ‘grey’ hydrogen, which is produced using fossil fuels but is by far the cheapest existing option.

However, research group BloombergNEF recently projected an 80% fall in the cost of green hydrogen by 2030, opening the way for its widespread use as a carbon-free fuel.

ERM’s projections suggest a full-scale floating wind farm deployed in 2032 – by which time 15MW turbines may be used – could produce hydrogen at £1.15/kg ($1.41/kg). “This is comparable with the projected wholesale UK price of natural gas,” Kinsella claimed.

Decarbonising heat and transport, as well as power supplies, are major challenges facing the UK as it seeks to become emissions 'net-zero' by 2050.

A 2018 report from the UK Committee on Climate Change said hydrogen could largely replace natural gas for heating into the 2030s, but questioned whether renewable generation could compete on cost with hydrogen produced using gas itself then subjected to carbon capture and storage.