Goal 3: To improve the blade manufacturing process so that quality variations and cost are minimized.
The resin transfer molding process has demonstrated the capability of producing quality fan blades up to 40 feet in diameter. Prototype studies to make GRP blades by this process should be undertaken. The study must include trade-off studies of manufacturing cost and quality versus losses in aerodynamic efficiency to enhance producibility.
The pultrusion process has a demonstrated capability to produce low-cost GRP blades but with a relatively inefficient constant cross section. Aeroelastic tailoring may partially compensate for the lack of twist and tapered planform compared to usual wind turbine blade geometries. A feasibility study should be conducted.
The introduction of new manufacturing processes must be accompanied by fatigue testing of full-size blades. Only in this way can the design details and the material quality be validated for the manufacturing process. Baseline studies on blades produced by current practice are needed.
Goal 4: To reduce the cost of blades enough so that periodic replacement becomes cost-effective.
Because fatigue crack propagation is slow in GRP composites, and is believed to be readily visible on annual tower-top inspections, the strategy described by goal 4 may be feasible. This would eliminate the need for extensive and expensive high-cycle fatigue testing. Eliminating the uncertainties in accounting for long-life service in design calculations would result in considerable weight savings. A detailed feasibility study with a realistic cost model should be undertaken if the manufacturing studies show promise of significant reduction in blade life-cycle cost.