Evaluation of Composite Structural Materials for Heliostat Cost Reduction

Abstract

Structures manufactured from steel comprise up to 40% of a concentrating solar thermal power (CSP) heliostat's cost. Composite structures represent a potential opportunity to reduce this cost. A reference heliostat structural model has been created with a reflector area of 25 m2. The design, constructed of low-carbon steel, provides baseline deflection and stiffness under a 21 m/s operating wind speed. Established roster of suitable metal alternative materials is considered including glass, basalt, and carbon fiber-reinforced polymer (GFRP, BFRP, and CFRP, respectively). Three heliostat components are investigated: the pylon, torque tube, and the purlin–strut assembly. Composite material properties are substituted for those of steel, and the beams are re-sized to match the original steel components’ deflection under given wind loads. Weight and cost changes resulting from this resizing are evaluated. It is found that GFRP and BFRP represent a 3 ×–6 × cost premium for the same operating deflection characteristics as steel across all three investigated component classes; with weight reduction only achieved for the purlin–strut assembly. While CFRP components can achieve approximately 25–75% weight savings depending on the application, this comes with a 9 ×–14 × cost increase over the steel baseline for tube-type structures and roughly 5 × cost increase when replacing c-channel structures. This work does not rule out the possibility of cost savings when the heliostat design and kinematics take advantage of composites' specific properties.