Feedback control of a tower solar plant with an optical corner reflector

Abstract In a thermal solar power tower plant, a field of heliostats reflects the solar radiation onto a receiver placed at the top of a tower. The heliostats must be appropriately positioned according to the sun position; this is usually done in open loop by exploiting the ephemeris data. In this paper we propose a closed-loop control where feedback is achieved with a corner reflector. This optical component, positioned at the centre of the receiver, has the distinctive feature of reflecting an incident ray in the same direction. Hence, the heliostat is correctly positioned only when the reflected sun light ray, further reflected by the corner reflector, hits its centre. The occurrence of this can be tested with a camera located close to the heliostat, suitable oriented towards the corner reflector.