heliostat

A heliostat is an optical device that uses a mirror to reflect and redirect sunlight toward a fixed target. The mirror, which is typically flat or lightly curved, is mounted on a two-axis gimbal or tracking system that follows the sun’s apparent motion across the sky. A control system adjusts the mirror angles so that the reflected beam remains directed at a predetermined receiver or target, often with feedback from sensors to maintain alignment.

In solar power generation, many heliostats form a field that concentrates sunlight onto a central receiver located on a tower or elevated structure. The receiver absorbs the concentrated light and converts it to heat, which is then used to produce steam and drive a turbine to generate electricity. Heliostat fields are designed to maximize optical efficiency while minimizing shading, blocking, and heat losses.

Other uses include solar furnaces, daylighting and solar lighting systems for buildings, and laboratory or research installations requiring a controllable sunbeam. Key design considerations include mirror reflectivity and durability, tracking accuracy, mechanical reliability, and the performance of the control software and actuators.

History and terminology: the name heliostat derives from helios (sun) and statis (standing or fixed). The concept emerged in early solar experiments and was refined over the 20th century; modern, large-scale heliostat fields became prominent with advances in solar thermal technology in the latter part of the century.