Design and cost of the first commercial stretched-membrane heliostat

ABSTRACT:
A complete design of a 50 m2 stretched-membrane heliostat was developed specifically for the early stages of manufacturing. The design included mirror-module refinements, drive selection, pylon and foundation design, and detailing and tracking control design. The mirror module and rear

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structure are highly similar to the Mark II prototype erected at Sandia National Laboratories, Albuquerque, in 1989. The pylon and foundation consist of a single pipe set in a cast-in-place pier as successfully developed at Sandia. The unique tracking control uses only commercially available industrial control components. Also, all real-time communication requirements have been eliminated to assure against the most common source of malfunctions in previous central receiver fields. Control commands are calculated internally to the local controller using a polynomial approximation curve fitted to actual sun position and adjusted for individual heliostat requirements. Direct material costs, in 1990 dollars, were obtained for several different production volumes from material and component manufacturers and subassembly subcontractors. Manufacturing costs for a low-volume production company are projected to be competitive with glass/metal heliostats.

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