Theoretical Analysis of Vacuum Flat-Plate Solar Collector with a Detail Model
Abstract
Flat-plate collectors are generally designed for applications with typical working temperatures between 40 °C and 60 °C, which is mostly the case for domestic hot water systems. The major effect on the performance of flat solar collector has heat loss through glazing. The reduction of front side heat loss and consequently increasing efficiency can be achieved by using vacuum glazing. The paper presents a theoretical analysis of flat-plate solar collectors with a vacuum glazing. Different configurations of the collector have been investigated by a detailed theoretical model based on combined external and internal energy balance of the absorber. Performance characteristics for vacuum flat-plate collector alternatives have been derived. Subsequently, annual energy gains have been evaluated for a selected variant and compared with state-of-art vacuum tube collectors. The results of modeling indicate, that in case of using advanced vacuum glazing with special low-emissivity coating (emissivity 0.20, solar transmittance 0.85), it is possible to achieve efficiency parameters similar to or even better than vacuum tube collectors.
Keywords
Flat-plate collector, Vacuum glazing, Detailed model