Sener Heliostat Design and Testing

During the past years, SENER has been working in the development of a new heliostat concept focused on Central Receiver Systems (CRS) applications. Main efforts have been conducted in order to optimize heliostat mechanism which approximately represents half the heliostat cost- as well as metallic structure and facet design. A detailed optimization study has been performed with the help of SENSOL a new software developed by SENER for solar projects analysis- in order to optimize heliostat requirements. Heliostat cost for mass production has also been optimized in collaboration with heliostat prototype manufacturers, taking into consideration man power and material requirements for heliostat construction. Starting from medium area heliostat (96.3 m2 of net area), a large area heliostat has been designed (115.6 m2 of net area). Both designs use the same actuation mechanism, despite the higher wind loads affecting large area design. The load capacity of the driving mechanism has been increased by means of an intelligent control strategy (SENER patent) implemented in the local heliostat control system: when highest winds occur, local control moves slightly the internal gears of the mechanism to its highest strength configuration in order to withstand wind load. SENER large area heliostat testing at CIEMAT-PSA facilities started in May 2005. Both tracking and optical performance capabilities have been tested during these months. Results obtained match the expected values. Second testing campaign was performed during October 2005, in order to fully validate SENER heliostat design for field operation. (Author)