WALAILAK JOURNAL OF SCIENCE AND TECHNOLOGY

Volume 15, No. 11, Month NOVEMBER, Year 2018, Pages 793 - 802

Thermal efficiency of a new prototype of evacuated tube collector using sn-al2o3 as a selective solar absorber

Warisa WAMAE, Tawat SURIWONG, Thotsaphon THRERUJIRAPAPONG

Abstract Download PDF

Three tin pigmented aluminium oxide (Sn-Al2O3) films were prepared with different tin content using an anodization process, which is applied as a selective solar absorber in a new prototype of evacuated tube collector (ETC). The morphology and distribution of elements on the coatings were characterized using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray (EDX) analyzer. The spectrally selective properties, defined as the ratio of solar absorptance (αsol) to thermal emittance (εtherm) were examined. In order to investigate the thermal performance of ETC using Sn-Al2O3 on an Al fin as a solar receiver, thermal efficiency (η) of the ETC was collected under steady-state conditions, as prescribed by ISO 9806-1 standard. The results, of the Sn-Al2O3 coatings reached a darker black colour with an increase in the colouring time. The samples were composed of different contents of Sn in the Al2O3 layer. The solar selectivity (αsol/εtherm) significantly increased with the increases in Sn content. The maximum thermal efficiency (ηmax) of the ETC under the nearly constant heat loss coefficient (UL), was obviously increased with the increasing Sn content. Therefore, the Sn-Al2O3 with different Sn contents is a good candidate for selective solar absorbers in a new prototype of ETC.

Keywords

Evacuated tube collector, Selective solar absorber, Anodization, Absorptance, Thermal

---