Development of a 30m² Heliostat with Hydraulic Drive

Reliable and cost-effective heliostats with high accuracy are a prerequisite for the successful market introduction of solar tower systems. The advantages of hydraulic drives are high positioning precision, no backlash, ability to go to stow position at electrical power loss and optional overload protection. Initial cost calculations indicated that a cost-competitive solution could be provided. The design of a heliostat with 30m² mirror area is described. The oil reservoir with pump, the valve bloc and the cylinders for the azimuth drive are located in the cross bar. The results of wind tunnel measurements with heliostat models of various aspect ratios led to an aspect ratio of 1.2. A wind fence was not assumed because in the rear part of usual heliostat fields it has no significant advantage as wind tunnel measurements showed. For the canting an automatic procedure will be applied at which the deflectometry method is used for the determination of the shape and orientation of the mirror facets. The first six prototypes will be erected at the Jülich solar tower site, Germany and one at the Plataforma Solar de Almeria, Spain. Extensive testing will be carried out to verify the design goals with respect to mechanical properties, optical performance, system functionality and power consumption. Based on the results a cost-benefit-based optimization of the construction and the drives will be carried out