| A Concrete Semi-Submersible Floating Wind Platform Produced with Proven Industrialized Concrete Construction Methods


The Volturnus Hull design was
inspired and built like an upside-down bridge.


The University of Maine’s patented VolturnUS is a transformational floating concrete hull technology to harness offshore wind energy with the potential to significantly reduce the cost of offshore wind. VolturnUS can support wind turbines in water depths of 45 meters or more.


  • $40m Investment from the Department of Energy for technology demonstration
  • $100m Investment from Diamond Offshore Wind, a subsidiary of the Mitsubishi Corporation, and RWE Renewables
  • State of Maine – Gulf of Maine Research Array
    The Governor’s Energy Office submitted an application to BOEM to lease a 15.2 square-mile site in the Gulf of Maine for the nation’s first floating offshore wind research site in federal waters.


Concrete construction gives benefits over steel

  • Industrialized pre-cast bridge construction techniques that can be made anywhere in the world using locally sourced material and labor
  • Lower cost per ton; lower overall Levelized Cost of Energy (LCOE)
  • Higher corrosion resistance than steel; lower Operation and Maintenance (O&M) costs and longer design life
  • Heavier than an equivalent steel system; low center of gravity and high center of buoyancy yield excellent wave motion resistance

Optimized & Simple Design

  • No complex features like active ballast systems, heave plates, or hanging masses
  • Rectangular bottom beam sections are easier to construct and add more wave motion resistance than cylindrical sections

Mobility & Ease of Deployment

  • Low tow-out draft allows for deployment in shallow water harbors around the globe. VolturnUS can be disconnected and returned to port for maintenance or turbine upgrades

VolturnUS Technology Development Timeline

The VolturnUS concrete floating wind turbine foundation is the culmination of more than a decade of research and development led by UMaine & the U.S. Department of Energy.

2011 – 1:50 Scale Testing

  • Tested 1 TLP, 1 spar, 1 semi-submersible
  • Conditions mimicked Gulf of Maine conditions
  • Largest public data set for floating offshore wind

2013-2014 – 1:8 Scale VolturnUS Testing

  • 1st grid-connected offshore turbine in the Americas
  • Scaled 6-MW design
  • 50 onboard sensors
  • 18-month deployment
    – Over 40 extreme events, including 500-year events
    – Less than 0.17g of acceleration in all cases
    – Validated numerical tools

2015 – Alfond W2 Ocean Engineering Lab Opens

  • $13.8 M offshore model testing facility at UMaine with a wind machine over a wave basin capable of producing scaled wind and wave conditions that represent some of the worst storms possible on Earth.
  • Allows rapid innovation of floating offshore wind technology

2016 – US Department of Energy Offshore Wind Advanced Technology Demonstration Program

  • Top tier status from the US Department of Energy (DOE) Advanced Technology Demonstration Program for offshore wind
  • Pilot project Aqua Ventus I to support up to 12MW turbine
  • More than $50 Million invested

2017 – VolurnUS FEED Meets ABS Requirements

  • 100% FEED approval obtained from the American Bureau of Shipping

2020 – Global Investment

  •  Diamond Offshore Wind, a subsidiary of the Mitsubishi Corp., and RWE Renewables, the second largest company in offshore wind globally invest $100m into the demonstration and will lead the construction, deployment and operations of the turbine.
  • New England Aqua Ventus LLC forms.

2024 – New England Aqua Ventus I Launch

  • Full-scale demonstration of 11MW VolturnUS to be deployed at the state-designated research site
  • Expected to be the first industrial-scale floating wind installation in the US

2030s – Commercial Offshore Wind Farms

  • Build on experience from Aqua Ventus I for commercial-scale projects using VolturnUS technology
  • Further design improvement and testing through investment from industrial and government sponsors

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