Tailored compliance for adaptive solar energy heliostats with experimental validation

The shape of sun-tracking heliostat mirrors in the central receiver systems (CRS) should ideally be off-axis paraboloids that adapt as a function of day of the year, time of the day and mirrors' locations in the mirror field. Such heliostats are costly to fabricate and control. Here proposed a heliostat design and control concept that can approximately adaptive paraboloids relatively simply and at a low cost. Bending forces are applied to a flat compliant mirror plate with a specific stiffness profile over the plate to form an approximate paraboloid. The results show the concept design is substantially superior to flat plate mirror heliostats and those with bending forces but with uniform-stiffness profiles. It is shown that a control concept that only considers a mirror's field location, and not the daily or seasonal changes, provides effective performance. An experimental prototype demonstrates the concept.