Heliostat tailored to Brazil

Kurzfassung

For Brazil it is important to realize a high local production share because of high import tax rates. The rim drive concept offers an alternative for expensive heliostat drive solutions with slew and linear drives from abroad. By (locally produced) rims the demands on the drives regarding strength and precision are reduced to a very low value and low cost drives can be used. Sandwich facets (which are usually foreseen for rim drive heliostats) are not available from Brazilian manufacturers and are replaced by a frame work steel structure with 4mm glass mirrors. The mirrors are bended only about one axis to avoid too high stress of the mirrors when low focal lengths (e.g. 30m) have to be realized. For an 8.1m² heliostat the mirror panel was divided into six stripes of 2.5m x 0.54m. The stripes have to be canted to reach a sufficiently small focal spot. An accordant heliostat was designed and built. High stiffness was reached and sufficient durability of the mirror facets against wind loads. For 8m² heliostats the framework design should be simplified but for 16m² heliostats (or bigger) it seems to be appropriate.