The order for the Great Yarmouth-based marine and engineering specialist follows an initial contract last September to build two initial daughter craft for customer North Star's renewables fleet.
The boats use a "game changing" hybrid-powered design developed by leading sustainable naval architect Chartwell Marine, in collaboration with North Star.
The aim was to produce high-performance vessels that combine diesel and electric outboard propulsion, a first for the offshore wind market.
North Star's first fleet purpose built for offshore wind operations and maintenance is being delivered to Dogger Bank Wind Farm partners Equinor, SSE Renewables and Eni Plenitude from February next year.
The four Alicat vessels will support operations with the safe transfer of maintenance technicians and equipment between North Star vessels and the Dogger Bank wind turbines.
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