Photo of VolturnUS 1:8 in Castine, Maine
VolturnUS 1:8 was the first grid-connected offshore wind turbine in the Americas.

The UMaine-developed, patent-pending, VolturnUS floating concrete hull technology can support wind turbines in water depths of 45 meters or more, and has the potential to significantly reduce the cost of offshore wind.

The VolturnUS technology is the culmination of more than a decade of collaborative research and development conducted by the University of Maine-led DeepCwind Consortium.

  • VolturnUS 1:8, deployed in 2013, is a 65 foot tall floating turbine prototype; 1:8th the scale of a 6 megawatt (MW), 425-foot rotor diameter design. It was designed and built at UMaine, assembled at Cianbro’s facility in Brewer, ME, and towed 30 miles from Brewer to Castine, ME by Maine Maritime Academy. This was the first grid-connected offshore wind turbine in the Americas.
  • The UMaine-led New England Aqua Ventus I project won top tier status in May 2016 from the US Department of Energy (DOE) Advanced Technology Demonstration Program for Offshore Wind. This means that the Aqua Ventus project is now automatically eligible for an additional $39.9 Million in construction funding from the DOE. This major development represents the strongest possible endorsement of the transformational VolturnUS concrete hull technology by the DOE. With this new funding, the Aqua Ventus project will likely become the first commercial scale floating wind project in the Americas.
  • New England Aqua Ventus I is a two × 6 MW turbine = 12 MW floating offshore wind pilot project 14 miles off Maine’s coast, developed by Maine Aqua Ventus, GP, LLC.  The objective of the pilot is to demonstrate the technology at full scale, allowing floating farms to be built out-of-sight across the US and the world in the 2020s, bringing lower-cost, clean renewable energy to coastal population centers.
  • In 2011, UMaine published the Maine Offshore Wind Report. Funded by more than $1 million from the U.S. Department of Energy, the report examines economics and policy, electrical grid integration, wind and wave, bathymetric, soil, and environmental research.  It also includes summaries of assembly and construction sites, critical issues for project development and permitting, and an analysis of the implications of the Jones Act.

Videos of VolturnUS  Performance:

VolturnUS 1:8 – Tow Across Penobscot Bay, November 2014

VolturnUS 1:8 November 2013 Extreme Event Performance

VolturnUS 1:8 December 2013 Extreme Event Performance


VolturnUS 1:8

VolturnUS 1:8 is a 65-foot-tall floating wind turbine prototype that is 1:8th the geometric scale of a 6-megawatt (MW), approximately 450-foot rotor diameter design. The patent-pending VolturnUS 1:8, was designed and built at UMaine, assembled at Cianbro’s facility in Brewer, successfully towed nearly 30 miles from Brewer by a Maine Maritime Academy tugboat, and anchored for testing off the coast of Castine, Maine in 90 ft of water. On June 13, 2013, the turbine was energized and began delivering electricity through an undersea cable to the Central Maine Power electricity grid, making VolturnUS 1:8 the first grid-connected offshore wind turbine in the Americas.

The innovative VolturnUS design utilizes a concrete semisubmersible floating hull and a composite materials tower designed to reduce both capital and Operation & Maintenance costs, and to allow local manufacturing throughout the US and the World.  The VolturnUS technology is the culmination of more than seven years of collaborative research and development conducted by the University of Maine-led DeepCwind Consortium.  The DeepCwind Consortium is a unique public-private research partnership funded by the Department of Energy, the National Science Foundation-Partners for InnovationMaine Technology Institute, the State of Maine, and the University of Maine, and includes more than 30 industry partners such as Cianbro and Maine Maritime Academy.

The VolturnUS 1:8 behaves as a floating laboratory with over 50 sensors onboard measuring wind, waves, current, temperature, accelerations, strains, turbine performance and mooring line loads.   Data acquired during the past year’s deployment off Castine validated design assumptions and performance, and have been used to further optimize UMaine’s VolturnUS system. The program goal when the technology is scaled up is to reduce the cost of offshore wind to compete favorably with other forms of electricity generation.

Photo of VolturnUS during a major storm event.
VolturnUS 1:8 was subjected to scaled extreme 50 year design conditions on November 1st, 2013.

As anticipated for a 1:8 scale unit, over the past year, the VolturnUS 1:8 has experienced numerous storm events representative of design environmental conditions prescribed by the American Bureau of Shipping (ABS) Guide for Building and Classing Floating Offshore Wind Turbines, 2013.  For example, Table 1 shows measured data from an event experienced on March 1, 2014 between 1-2 pm, and compares that to a 50-year  ABS Design Load Case (DLC), called DLC 1.6.  Also shown in Table 1 is the predicted behavior from a coupled aeroelastic/hydrodynamic simulation of the full-scale VolturnUS 10-miles offshore Maine subjected to the specified American Bureau of Shipping (ABS) DLC 1.6 conditions. Please note the proximity of the measured March 1 event data and the VolturnUS 1:8 response to the ABS DLC 1.6 50-year prescribed condition.    During this major storm event on March 1, the maximum-recorded wave height and peak period were within 1% and 7 %, respectively of the ABS DLC 1.6 prescribed scaled conditions.  The resulting max nacelle acceleration and max heel angle, were within 14-16% of what a 6 MW VolturnUS system would experience under DLC 1.6, 10-miles offshore.

During the deployment, the prototype performed as expected in both operation and ABS extreme Design Load Cases (DLC) as follows:

  • Over 110 operational load cases similar to ABS DLC 1,2,
  • Over 18 extreme load cases equivalent to ABS DLC 1.6 and 6.1, representing 50-year Return Period Events
  • One event equivalent to the ABS survival load case, representing a 500-year Return Period Event.

Based on observations over the past year, the 1:8 VolturnUS exhibited responses in line with coupled model design predictions and provides confidence moving forward with design and construction of a full-scale floating offshore wind turbine utilizing the VolturnUS platform technology.

In all 119 events described above, the VolturnUS floating platform performed markedly well.  It exhibited accelerations very close to the predicted results, less than 0.17g for the whole year under all operational, 50-year scaled, and 500-year scaled return period events.