Wind turbine blades continue to be the target of technological improvements by the use of better designs, materials, manufacturing, analysis and testing. As the size of turbines has grown over the past decade, designers have restrained the associated growth in blade weight to less than would have been possible through simple scaling-up of past approaches. These past improvements are briefly summarized. Manufacturing trends and design drivers are presented, as are the ways these design drivers have changed. Issues related to blade material choices are described, first for the currently dominant glass fibre technology and then for the potential use of carbon fibres. Some possible directions for future blade design options are presented, namely new planforms, aerofoils and aeroelastic tailoring. The significant improvement in sophistication of stress analysis and full-scale blade testing are also discussed.

. The primary objectives of the Blade-Scaling Study are to assess the scaling of current materials and manufacturing technologies for blades of 40 to 60 meters in length, and to develop scaling curves of estimated cost and mass for rotor blades in that size range. ApproachWe investigated the scaling of current materials and manufacturing technologies for wind turbine blades of 40 to 60 meters in length. Direct design calculations were used to construct a computational blade-scaling model, which was then used to calculate structural properties for a wide range of aerodynamic designs and rotor sizes. Industry manufacturing experience was used to develop cost estimates based on blade mass, surface area, and the duration of the assumed production run. The structural design model was also used to perform a series of parametric analyses. The results quantify the mass and cost savings possible for specific modifications to the baseline blade design, demonstrate the aerodynamic and structural trade-offs involved, and identify the constraints and practical limits to each modification. Conclusions and ResultsThe scaling-model results were compared with mass data for current commercial blades. For a given blade design, the scaling model indicates that blade mass and costs scale as a near-cubic of rotor diameter. In contrast, commercial blade designs have maintained a scaling exponent closer to 2.4 for lengths ranging between 20 and 40 meters. Results from the scaling study indicate that:• To realize this lower scaling exponent on cost and mass has required significant evolution of the aerodynamic and structural designs.• Commercial blades at the upper end of the current size range are already pushing the limits of what can be achieved using conventional manufacturing methods and materials.• For even larger blades, avoiding a near-cubic mass increase will require basic changes in:− Materials, such as carbon or glass/carbon hybrids. − Manufacturing processes that can yield better mean properties and/or reduced property scatter through improvements in fiber alignment, compaction, and void reduction. The extent to which such improvements would result in lower blade masses may be constrained by blade stiffness requirements. − Load-mitigating rotor designs.For the scaling results presented in this report, the basic material and manufacturing process remained unchanged. As such, a reduction in mass will correspond to a reduction of production iii blade costs in the same proportion. However, this will not hold true for mass savings realized through changes in materials, process, and rotor design. In evaluating each such change, the implications on both mass and cost must be considered.As part of the cost analysis, it was shown that the "learning curve" required to achieve a mature production process has a meaningful effect on blade costs for the range of rotor sizes considered. A production rate of 200 megawatts (MW) per year implies 800 blades at 750 kilowatts (kW), but only 120 blades at 5 MW. Therefore, the cost penalty for ini...

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As part of the U.S. Department of Energy's Wind Partnerships for Advanced Component Technologies (WindPACT) program, Global Energy Concepts, LLC is performing a Blade System Design Study (BSDS) concerning innovations in materials, processes and structural configurations for application to wind turbine blades in the multi-megawatt range. The BSDS Volume I project report addresses issues and constraints identified to scaling conventional blade designs to the megawatt size range, and evaluated candidate materials, manufacturing and design innovations for overcoming and improving large blade economics. The current report (Volume II), presents additional discussion of materials and manufacturing issues for large blades, including a summary of current trends in commercial blade manufacturing. Specifications are then developed to guide the preliminary design of MW-scale blades. Using preliminary design calculations for a 3.0 MW blade, parametric analyses are performed to quantify the potential benefits in stiffness and decreased gravity loading by replacement of a baseline fiberglass spar with carbon-fiberglass hybrid material. Complete preliminary designs are then presented for 3.0 MW and 5.0 MW blades that incorporate fiberglass-to-carbon transitions at mid-span. Based on analysis of these designs, technical issues are identified and discussed. Finally, recommendations are made for composites testing under Part I1 of the BSDS, and the initial planned test matrix for that program is presented.3

Sandia is a rnuitiprcgram laboratory operated by Sandi Corporation.h k h e e d tdartin Campany. for the United States hpartmant of q n e r g y under Contract DE-AC04-WAL85OM);""~ Approved tor public release; firmer dissemination unlimited. Issued by b d i a AbstractThe objectives of this work were to develop conceptual structural designs for an adaptive (bend-twist coupled) blade, to evaluate candidate design concepts, to identify constraints and/or concerns for manufacturing, load paths, and stress concentrations, to develop estimates of structural performance and costs, and to select a single configuration as showing the greatest potential for success in manufacturing, strength and durability.This report summarizes the work performed on this project, including the approach taken, configurations and materials considered, and the computational methodology used. The work presented includes: 0Candidate fiber orientations and fabric architectures for adaptive blade manufacture are identified and assessed on the basis of estimated static strength, stiffness, and fabrication costs. 0A parametric study is performed for potential blade structural arrangements. Each configuration is evaluated on the basis of estimated manufacturing cost and magnitude of bend-twist coupling achieved. Based on the parametric study results, a single configuration is selected for hrther evaluation. A complete blade model is developed and assessed on the basis of estimated manufacturing cost and bend-twist behavior under steady loading.