Performance investigation of a new designed vacuum flat plate solar water collector: A comparative theoretical study

Abstract

This paper presents a new design of vacuum flat plate solar collector (VFPSC). This inspired design is based on a combination of two conventional systems; the flat plate solar collector (FPSC) and the evacuated tube solar collector (ETSC). The new configuration, which is characterised by a curved evacuated cover and rear Rockwool insulation is compared with FPSC and ETSC. Collectors’ performance is predicted through a theoretical approach that includes heat transfer and energy balance equations, where thermo-physical and geometrical properties of each collector are considered. The developed computational program is validated against experimental results carried out on FPSC. The optimal number of tubes is identified to perform a comparative study under the best efficiency point for different values of absorber emissivity including collectors’ cost. The new VFPSC proves that the combination of front vacuum insulation and back opaque thermal insulation can result in significant heat loss reduction, and thus performance enhancement for the whole emissivity range. As a result, the proposed VFPSC provides more thermal efficiency than FPSC and ETSC by 7.13% and 28.32%, respectively, for an emissivity of 0.95, while for an emissivity of 0.05, it reaches ratios of 22.77% compared to FPSC and almost the same ETSC efficiency levels, with a much lower cost. Moreover, it shows lower heat loss factor compared to other similar VFPSCs. Overall, VFPSC offers a promising solution that has the required ability for producing hot water with a low cost and may take place as heating device in buildings and industrial sectors.