Design, optimization and optical performance study of tripod heliostat for solar power tower plant

Abstract

Heliostats account for about 50% of the capital cost of power towers. In conventional heliostats with vertical pedestals and azimuth-elevation drives, the support structure contributes 40–50% of this cost due to heavy cantilever arms required by the large spanning structures. Additional costs are imposed by costly, difficult to maintain drive mechanisms. Here we show that a tripod heliostat can substantially address these shortcomings. We have presented the protocol and results of systematic structural analysis of heliostats with aperture areas of 62 and 100 m2. We have included effects of shape on load reaction and structure cost. An in-house ray-tracing software is incorporated to estimate the performance penalties due to deformation under gravity and wind loads. The analysis shows that the additional energy collection by a less-stiff, larger heliostat more than offsets the spillage due to the greater deformation of the same.We have demonstrated that the economics of power towers are strongly governed by the structural cost of the heliostats rather than by their optical performance. We have brought down the cost of a tripod heliostat to $ 72/m2 which is less than half that of the conventional systems and meets the target set by the US National Academy of Engineering.