Effect of Aspect Ratio of Heliostat on Cost of Energy from Solar Power Tower Plants

摘要

The solar power tower plant consists of thousands of heliostats, and heliostat field cost contributes nearly 40–50% of the totalplant cost. This makes the cost of heliostat an important parameter while designing solar power tower plant, and it variesconsiderably with its size and wind loads. Furthermore, the size and aspect ratio of heliostat have a significant influence on thewind loads impacting its load-bearing components. While the importance of optimum size of reflector area has been studiedby several researchers, its aspect ratio (width/height) has not been examined in detail. In this view, the main objective of thisstudy is to identify the appropriate aspect ratio of a heliostat’s reflector area. An analysis of heliostat cost using its reflectorarea and the aspect ratio as variable parameters illustrates that heliostat cost per unit area can be minimized by distributingcosts into various categories having different cost dependencies on area as well as aspect ratio. Using the component-wisecost break-up of 148 m~2 Advanced Thermal Systems’ heliostat as a reference, optimum area and aspect ratio of heliostatare determined parametrically. Further, a hypothetical power tower plant with 50 MW capacity and 6 h of thermal energystorage is simulated with heliostat fields comprising heliostats built with various aspect ratios and corresponding optimumreflector area. The results indicate that it is not only more economical to build heliostats with aspect ratio of around 2, butalso such heliostat fields deliver higher optical efficiency on an annualized basis.