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Maine Public

VolturnUS Floating Concrete Hull Technology

The UMaine-developed, patented 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. To date, the technology has 70 patents in the US and around the world. VolturnUS is ABS approved and is designed to be fabricated locally.

A 2020 report from the National Renewable Energy Laboratory determined the levelized cost of energy (LCOE)1 is < 6 cents/kWh using the VolturnUS technology at commercial scale.

The innovative VolturnUS design utilizes a concrete semisubmersible floating hull and a composite materials tower designed to reduce both capital and operation and maintenance costs, and to allow local manufacturing throughout the US and the World.

Aqua Ventus is leading a demonstration project called New England Aqua Ventus I, an 11 MW floating offshore wind demonstration project to develop a clean, renewable energy source off Maine’s shores. The objective is to demonstrate the technology at full scale, allowing floating farms to be built in oceans of the US and the world in the 2030s, bringing lower-cost, clean renewable energy to coastal population centers. This project will likely become the first commercial-scale floating wind project in the Americas.  Click here to learn more about this project.

Photo of VolturnUS 1:8 in Castine, Maine

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.

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.

  1. LCOE reflects the total cost of generating a unit of electricity.

Videos of VolturnUS Performance:

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 patented 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.

In June 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 VolturnUS successfully completed its 18 month deployment as planned, and was retrieved for post-deployment analysis by UMaine in November 2014.

VolturnUS 1:8 passing under Penobscot Narrows Bridge in Bucksport, ME in early June 2013.
VolturnUS 1:8 passing under Penobscot Narrows Bridge in Bucksport, ME in early June 2013.

The VolturnUS 1:8 behaved 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 Castine deployment validated design assumptions and performance, and have been used to further optimize UMaine’s VolturnUS system. The ultimate goal of this technology is to reduce the cost of offshore wind to compete favorably with other forms of electricity generation without subsidy.
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, the VolturnUS 1:8 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.  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 during deployment, the VolturnUS 1:8 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.

Early Research on Floating Offshore Wind Turbines

1:50 Scale Testing at Marin (2011)

In 2011, researchers at the University of Maine traveled to the Maritime Research Institute in the Netherlands (MARIN) to test three different 1:50 scale designs for floating offshore wind turbines (a tension-leg platform, a semi-submersible, and a spar design). During the 6 week testing program, the floating platforms were tested 16 hours a day and were being subjected to different wind and wave intensity levels that mimicked conditions in the Gulf of Maine in side-by-side comparison tests. Data collected during this test program informed the design of UMaine’s VolturnUS.

View a video on the test program:

Maine Offshore Wind Report

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, and issues for project development and permitting.