Aberdeen-based North Star Renewables is following up its debut $376m wind farm ship order with another deal for 'daughter craft' to transfer crew.

The two multi-million dollar units will be confirmed in September at a UK shipyard.

Delivery will be in 2022 and 2023 for operation at Dogger Bank Wind Farm off the UK.

Designed by UK company Chartwell Marine, North Star said they will be the world's first hybrid vessels of this kind.

The ships will support North Star's new service operation vessels (SOVs), ordered for £270m ($376m) at Vard's Vung Tao yard in Vietnam, backed by 10-year charters to Equinor.

They can also work with mother ship crew transfer vessels, moving workers to turbines.

They will offer increased operability at wave heights of up to 1.7 metres, 33% higher than anything else currently available, North Star and Chartwell claim.

Emergency services

The daughter craft will also provide emergency safety and rescue cover, something North Star already specialises in with its fleet of 63 offshore vessels.

The new ships have been developed over the last two years.

Andrew Duncan, renewables director at North Star, said: "The UK has the world’s largest offshore wind market backed by an experienced and innovative supply chain.

"We are committed to providing local content opportunities where possible, through direct and indirect employment, partnerships and supply chain — our annual spend is tens of millions of pounds."

Chartwell managing director Andy Page said the design builds on experience gained from its low-emission research and development project funded by the Carbon Trust’s Offshore Wind Accelerator.

"Above all, we aim to furnish the sector with vessel designs that are safe, cost-effective, and sustainable in equal measure — making the most of advances in propulsion technology, but also preserving the key ingredients that constitute effective performance for offshore wind developers and operators," he said.

Dogger Bank is currently under construction by joint venture partners SSE Renewables, Equinor and Eni, and, when completed, it will be the world's largest offshore wind farm.