Offshore Wind Front-End Engineering Design (FEED) Study

  • Client:
    Energy Technologies Institute (ETI)
  • Completion Date:
    March 2015
  • Key Collaborators:
    DSM Dyneema
  • Project Type:
    Technology Development
  • Service Categories:
    Naval Architecture
    Marine Engineering
    Ocean Engineering
  • Challenge:
    Install a cost-competitive, 492-foot (150-meter) diameter wind turbine in deep water


In 2012, Glosten was selected by the Energy Technologies Institute to design a floating offshore wind platform system demonstrator. The goals of the project were to accelerate the market introduction of floating foundations for deep water offshore wind farms and to break down technical barriers for deployment. The result was a front-end engineering level design of the PelaStar floating foundation supporting an existing full-scale 6 MW offshore wind turbine.

The viability of offshore floating wind is based on demonstrating the lowest cost of energy of all conventional low-carbon power sources. This is possible by reaching better wind resources with larger, more powerful, and more efficient turbines but requires incorporating lower cost foundations and reducing balance-of-plant costs. These costs are controlled by providing a floating foundation with minimal structural weight that maximizes turbine availability by minimizing turbine wear due to platform motion. The system must also minimize maintenance costs by avoiding expensive interventions with large service vessels.



Glosten completed a FEED-level design of the PelaStar™ tension-leg platform to support an Alstom (now GE) 6 MW Haliade 150 turbine. The Glosten-Alstom team worked closely to model the coupled motion response of the platform and turbine. Teams of top-tier subcontractors were contracted to develop plans for hull construction, anchor installation, tendon manufacture, site installation and operations, and maintenance. A full cost-of-energy study was also prepared that applied the detailed demonstrator project cost data to predict the future cost of energy of floating wind farms over a wide range of UK offshore sites.

The final design was delivered in February of 2014, and results show that UK offshore wind energy costs could fall to below £85/MWh by the mid-2020s, with further reductions possible as this technology matures. The PelaStar™ 6 MW demonstrator has been designed for installation in the Celtic Sea off Cornwall. The designed structure reaches 590 feet (180 meters) from blade tip to waterline and will operate continuously in the harsh conditions of the North Atlantic. Rock anchor systems, tendons and connectors, hull fabrication and transport, assembly, installation, and operations have all been designed and planned, and costs have been estimated for the construction phase.

The study has shown the potential for targeted innovation to reduce the cost of offshore wind energy. This project has shown that, by 2030, offshore wind could be delivering energy at costs similar to the lowest cost forms of low carbon generation. This project has already validated our earlier research into offshore wind which showed that that access to high wind areas which are reasonably close to shore will result in very competitive energy costs.

– Andrew Scott, ETI Program Manager

In The Press.