Manufacturers’ Proposed Innovations

VIRGINIA OFFSHORE WIND COST REDUCTION 

THROUGH INNOVATION STUDY (VOWCRIS)

B. Maples • National Renewable Energy Laboratory • Golden, Colorado

J. Campbell, D. Arora • Alstom • Richmond, Virginia

Introduction

Anticipated Impacts

Foundation and Installation Costs

•Project work has a special focus on three areas of 

innovation:

- Turbine: using a larger turbine with a more robust 

drive train that captures specific benefits of a 

permanent magnet direct-drive (PMDD) generator

- Support Structure (Foundation): reducing foundation 

and substructure costs by evaluating three 

alternatives to a standard jacket configuration.

- Assembly, Transport, & Installation: exploring cost 

reductions afforded by installation systems that avoid 

multiple offshore lifts.

Pure Torque Direct Drive Drivetrain

According to Alstom:

• Two solid bearings transmit main bending loads 

safely to the tower (red arrows) while an elastic 

coupling ensures the generator rotor receives only 

pure torque (green arrows).

• The permanent magnet direct drive (PMDD) 

generator eliminates the failure prone gearbox, 

leading towards increased reliability and greater 

generation efficiencies.

• The design is equipped with three identical full 

power converters to ensure uninterrupted 

production. 

• An optimized ratio of turbine rotor swept area to 

generator rated capacity coupled with the 

advanced drivetrain yields up to 40% more 

electricity generation per kilogram of material used 

than today’s offshore turbines. 

•Initial analysis shows that all three of the 

foundation designs investigated may achieve 

20% to 25% cost reductions with respect to a 

standard jacket and turbine installation. 

•Though direct drive turbines may present 

increased challenges to manufacturers, many 

OEM’s believe owners assume less risk in the 

operation phase of a wind plant. 

•Final analysis results will be available soon 

after the conclusion of the study (2014). 

•With estimates of turbine, foundation, and installation 

costs for offshore wind plants upwards of two thirds 

of total project investment cost, there is an increasing 

focus on identifying opportunities to reduce these 

costs. 

•The VOWCRIS project is an integrated systems 

approach to the feasibility-level design, performance, 

and cost-of-energy estimate for a notional 600-

megawatt offshore wind project using site 

characteristics that apply to the Wind Energy Areas 

of Virginia, Maryland and North Carolina.

Inward Battered Guide Structure (IBGS)

According to Keystone Engineering:

• The IBGS design minimizes the amount of steel and welds needed for 

fabrication, significantly lowering costs with respect to a standard jacket.

• By pre-installing the lead piles and fitting more foundations per installation 

vessel, total foundation installation time is greatly reduced. 

• The design has been installed for oil and gas as well as met mast applications 

with one platform surviving a direct hit from hurricane Katrina.

Suction Caisson Tripod (SCT)

According to Moffatt & Nichol:

• The SCT design requires no pile driving which eliminates the need for 

additional expensive offshore operations as well as substantially reducing 

environmental impacts. 

• The relatively wide tripod structure makes it possible to use a system of 

floating pontoons/barges arranged so that the tripod foundation and turbine 

can be towed to site without the use of expensive offshore lift vessels.

Mobile Self Installing Platform (MSIP)

According to Offshore Wind Power Systems of Texas:

• The MSIP avoids the use of expensive offshore lift vessels for the 

foundation and turbine installation due to its ability to float-out and self 

install with the turbine pre-erected. 

• The caisson design requires no pile driving or sea floor prep and can 

accommodate uneven sea floors without change in design.

• The modular design, adapted from technology with 60 years of offshore 

experience, allows for high density shipping from around the globe, 

Source: Offshore Wind Power Systems of Texas reducing transportation and fabrication costs.

Source: Keystone Engineering Inc.

Source: Moffatt & Nichol

Source: Alstom

Source: Alstom

Representative Drivetrain Tradeoff

2013 Offshore WINDPOWER •  Providence, Rhode Island •  October 22 – 23, 2013

NREL/PO‐6A20‐60464

NREL is a national laboratory of the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

The information contained in this poster is subject to a government license.