Controlled Static Environment Tests on Vacuum-Membrane Solar-Dish Facets for a Low-Cost Vacuum Control System
Abstract
Small-scale vacuum-membrane facets for multi-faceted concentrated solar power (CSP) systems are investigated in this work. These facets are constructed from polymer-based reflective membranes adhered to the rim of cost-effective elliptical television antennas. Focal lengths on each facet can be varied by adjusting membrane depth. Previous studies have indicated that the membrane depth changes due to varying ambient conditions which affects the optical performance of the concentrator. The current work first focused on identifying the main cause of membrane movement using a controlled-environment experimental setup. Secondly, the work focused on how membrane movement could be reduced by utilizing a low-cost focus control system in outdoor experiments. The controlled-environment experimental setup underscored the significant influence of ambient temperature alterations on membrane movement compared to ambient pressure alterations. The outdoor experiment demonstrated substantial membrane movement; however, results showed that a low-cost constant differential pressure focus control system consisting of two 12 V diaphragm air pumps, two BMP280 barometric pressure sensors, and a microcontroller could reduce this movement to being within the targeted minimum limit of ±2 mm. It was found that periodic adjustments may be required to maintain long-term stability.
Keywords
Vacuum-membrane, Csp, Concentrator, Low-cost, Focus control system