Hall Effect Focus Control System for Vacuum-Membrane Solar Dish Facets

This study investigates the development and implementation of a novel Hall effect focus control system for sensing and maintaining membrane displacement of vacuum-membrane solar dish facets for small-scale concentrating solar power (CSP) systems. Such a CSP system comprises of 46 individual elliptical vacuum-membrane solar-dish facets, each with a variable focal length dependent on the membrane depth. Previous research identified membrane movement as a significant challenge affecting system performance throughout an operating day, due to changing environmental conditions (especially ambient temperature). In response, a cost-effective and low power consumption focus control system utilizing a Hall effect depth sensing method was developed in the current work and mounted to a single facet. Outdoor experimentation on a single facet demonstrated that the control system successfully reduced membrane displacement within an acceptable 0.069 mm/°C accuracy, which is within the required limit of ±2 mm movement for a minimum 90% intercept factor at the solar receiver. Furthermore, by incorporating temperature effects on the Hall effect linear displacement sensor's magnet, a higher accuracy of 0.036 mm/°C was obtained throughout an operating day. These advancements hold promise for enhancing the efficiency and performance of small-scale CSP systems.