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Offshore Wind: Sandia Large Rotor Development


Sandia National Laboratories Wind Energy Technologies Department, creates and evaluates innovative large blade concepts for horizontal axis wind turbines to promote designs that are more efficient aerodynamically, structurally, and economically. Recent work has focused on the development of a 100-meter blade for a 13.2 MW horizontal axis wind turbine, a blade which is significantly longer than the largest commercial blades that existed at the beginning of this project (approximately 60 meters long).

Initial All-Glass 100-m Blade Studies: SNL100-00
The initial study focused on development, documentation, and dissemination of the Sandia 100-m All-glass Baseline Wind Turbine Blade, termed “SNL100-00”, which employs conventional architecture and fiberglass-only composite materials. A detailed composite layup and geometry are available through the links below, along with the associated 13.2 MW Turbine Design Models.

Analyses of the baseline model for design loads from international standards demonstrated acceptance of the design with respect to strength, fatigue, deflection, and buckling. Challenges and opportunities for large blade research are summarized below in the referenced reports and linked documents.

In future work, these 100-meter blade models will provide a starting point for consideration of blade innovations with potential performance improvement, weight reduction, and cost improvements. A design scorecard is provided below for use by researchers to compare the effect of innovations on the principal design drivers which include weight, fatigue life, buckling, tip deflection, maximum strains, and aeroelastic stability (flutter margin). The 13.2 MW turbine models also provide a starting point for turbine and turbine control studies.

100-m Carbon Blade Design Studies: SNL100-01
An updated 100-m blade reference model has been developed, termed as SNL100-01. The new design is a modification to the baseline SNL100-00 design with the same external geometry; however, a carbon spar cap was introduced into the design. The weight of the SNL100-01 design is about 74,000 kg, which is a 35% reduction in weight from the baseline all-glass blade. A series of carbon spar cap designs were analyzed and documented with SNL100-01 as the final design model. In addition to the new spar cap, additional associated modifications were made including reduction in spar and TE reinforcement width, movement of the two principal spar caps, and thinning of the root. Although efforts were made to reduce weight, further opportunities exist to reduce the weight of SNL100-01 because no systematic efforts to optimize the design were performed.

Challenges and Opportunities

Initial Observations
A 100-m blade using conventional geometry and all-glass materials is possible. All design requirements are satisfied including maximum strains, tip-tower clearance, buckling resistance, and fatigue life. However, the blade weight for the initial SNL100-00 design was very high (and not cost-effective). The SNL100-01 carbon blade provides one example of weight reduction. However, additional future work can address these concerns while improving performance and reducing cost.

Current and Future Work: Potential Research Directions
Significant opportunity exists to reduce weight and cost through innovations and structural optimization. Innovations such as the use of carbon fiber, very thick airfoils such as flatback airfoils, bend-twist coupling, geometric sweep, pre-bending, and unique architecture, anti-buckling devices, structured core, and active control could be considered. Many of these innovations have been demonstrated in prior Sandia blade development programs, which are documented in Sandia Wind Energy Publications.

Other considerations for future work and potential research in large rotor technology are outlined in the SNL100-00 design report provided below.

Sandia Blade and Turbine Design Models: Reports and Model Files

Model Request Form (172KB DOC)
Design Scorecard (182KB DOC)

Blade Models: Detailed Design Information

(Blade Key: SNL[length(m)]-[version])
Blade Designation Blade Report Brief Description Design Scorecard Model Files Mini-report
“SNL100-00″ SAND2011-3779(1.22MB PDF) Sandia 100m All-glass Baseline Blade SNL100-00 Design Scorecard (327KB PDF) SNL100-00 Model Files Description Report
(447KB PDF)
“SNL100-01″ —– Sandia 100m Blade with Carbon Spar SNL100-01 Design Scorecard (332KB PDF) SNL100-01 Model Files Description Report
(1.25MB PDF)
“SNL100-02″ —– SNL100-00 with design modification series #2 —– Future Release

Turbine Models

(Turbine Key: SNL[rating(MW)]-[blade version]-[siting/foundation type])
Turbine Designation Brief Description Model Files Mini-report
SNL13.2MW-00-Land 13.2MW land-based turbine model with SNL100-00 Blades SNL13.2MW-00-Land Model Files Description Report (321KB PDF)
SNL13.2MW-01-Land 13.2MW land-based turbine with SNL100-01 Blades Refer to “SNL13.2MW-00-Land Turbine Model”
SNL13.2MW-02-Land —– —–


SNL 100-00 Baseline All-glass Blade References:
Griffith, D.T. and Ashwill, T.D., “The Sandia 100-meter All-glass Baseline Wind Turbine Blade: SNL100-00,” Sandia National Laboratories Technical Report, SAND2011-3779, June 2011
(1.22MB PDF)

Griffith, D.T. and Ashwill, T.D., and Resor, B.R., “Large Offshore Rotor Development: Design and Analysis of the Sandia 100-meter Wind Turbine Blade,” 53rd AIAA Structures, Structural Dynamics, and Materials Conference, Honolulu, HI, April 23-26, 2012, AIAA2012-1499 (1.21MB PDF).

SNL100-01 Carbon Design Studies:
Griffith, D.T., “The SNL100-01 Blade: Carbon Design Studies for the Sandia 100-meter Blade,” Sandia National Laboratories Technical Report, SAND2013-1178, February 2013 (1.25MB PDF).

Griffith, D.T., Resor, B.R., Ashwill, T.D., “Challenges and Opportunities in Large Offshore Rotor Development: Sandia 100-meter Blade Research,” AWEA WINDPOWER 2012 Conference and Exhibition, Scientific Track Paper, Atlanta, GA, USA, June 3-6, 2012 (560KB PDF).

Griffith, D.T., “Large Rotor Development: Sandia 100-meter Blade Research,” Invited Presentation, Wind Turbine Blade Manufacturer 2012 Conference, November 27-29, 2012, Dusseldorf, Germany
(1.71MB PDF)

Documentation for All Blade and Turbine Model Files:
“Sandia Large Rotor Design Scorecard,” Sandia National Laboratories Technical Report, SAND2011-9113P, December 2011 (182KB PDF).

See above for links to all blade and turbine model documentation including Design Scorecards for all blade models.

Corson, D., Griffith, D.T., et al, “Investigating Aeroelastic Performance of Multi-MegaWatt Wind Turbine Rotors Using CFD,” AIAA Structures, 53rd Structural Dynamics and Materials Conference, Honolulu, HI, April 23-26, 2012, AIAA2012-1827 (1.46MB PDF).


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