Located in waters ranging from 100m to 130m in depth off the east coast of Shetland in Scotland, the Stoura Offshore Wind Farm is currently in the early stages of development.

Developer ESB, Ireland’s leading energy company, is exploring a range of options to identify the optimal solutions for the Stoura Offshore Wind Farm. Whilst this will be a floating windfarm, an initial challenge set by the ESB team was to first look at fixed foundation options for the substation. Assessing the feasibility of a fixed foundation for the offshore substation at the proposed depths is a novel approach on an offshore wind project – requiring a mix of core know-how and innovative thinking to derive viable technical solutions.

Arup was appointed to provide early-stage advisory services, exploring different foundation options for the offshore wind substation. Leveraging our offshore engineering experience in challenging site conditions and deep-water locations, our structural, mechanical and electrical engineers identified four potential options for the substation.

The design of the substation, which houses critical electrical components and collects and exports power, is crucial for the efficient and reliable operation of the wind farm. When developing the design options, Arup’s engineers provided an exhaustive concept screening, including thorough analysis of the substation’s potential location, construction and decommissioning factors, safe access for maintenance crews and the ability to withstand extreme weather conditions. 

Working together with ESB, our engineers and specialists considered all these factors to shortlist recommended foundation design options, ensuring that overall project needs are incorporated from the beginning of the design process.

Screening foundation options for the offshore substation

Arup’s team of structural, mechanical and electrical engineers worked with ESB to develop preferred foundation types for the offshore substation. Following ESB’s initial request, the team reviewed the viable options for a fixed offshore substation foundation. We developed a scoring system and weighted criteria to evaluate the foundation options, which were agreed in a workshop with ESB.

Following an assessment of the existing foundation technologies and consideration of key technical risks, including supply chain, installation, maintenance and decommissioning, we selected four potential options:

  • Jacket (drilled and grouted piles)
  • Gravity base steel jacket (‘pad’ footings)
  • Concrete gravity base
  • Arup Concept Elevator (ACE) platform

Our engineers examined other offshore substation designs and recent pre-FEED (Front End Engineering Design) studies to provide preliminary sizing estimates, a project execution strategy and cost assessments.

Illustration of four offshore substation designs

Arup advised ESB on four potential options for the offshore substation design

This feasibility study has uncovered multiple design options for the offshore substation. Arup’s analysis and recommendations will be instrumental to ESB as we seek to develop the Stoura Offshore Wind Farm and harness the vast wind resources of the North Sea.

Cian Desmond

Stoura Project Director, ESB