Design and prototyping of a heliostat structure using advanced high strength steel

• Heliostat structures can be made from advanced high strength steel (AHSS) • Automotive design approaches can improve stiffness and strength with downgauging. • A prototype AHSS heliostat was fabricated with mirror support structure mass of 6.1 kg/m 2. Heliostat structures typically use galvanized mild steel to meet precise optomechanical requirements and survive environmental loads. The structure can comprise a high specific mass per mirror area, accounting for a meaningful portion of the heliostat cost. Advanced high strength steel (AHSS) used as structural elements can improve optical performance, reduce mass, and reduce costs. These include boron steels which have been widely adopted by the automotive industry when formability, high performance, lightweighting, and low cost are utmost design requirements. Herein, the design considerations for implementing AHSS in heliostats are presented, including approaches for section optimization to maximize stiffness while avoiding thin wall buckling modes. A mid-sized heliostat is modeled with uniform loads showing 19% less tip deflection and 31% lower specific mass than the reference steel design. To show viability, AlSi coated 22MnB5 AHSS is used to fabricate a downgauged radial truss and mirror support structure with a specific mass of 6.1 kg/m 2 . This AHSS grade, originally designed for hot stamping, is continuously hot-dip coated on both sides. The coating is metallurgically bonded to the steel substrate upon high temperature heat treatment in air without a protective atmosphere, creating adherent intermetallic Al-Si-Fe interlayers which provide atmospheric corrosion resistance. The 5.6 m 2 AHSS prototype heliostat was tested under proof-of-concept external loads with measured stresses and resulting deflections within design limits. Additionally, AHSS heliostats for CSP and process heat applications can leverage automotive advanced material processing and continuous heat treatment for on-site fabrication to reduce material and transportation costs.