화학공학소재연구정보센터
Solar Energy Materials and Solar Cells, Vol.157, 777-782, 2016
Accelerated ageing tests of carbon nanotube spectrally selective solar absorbers
A novel tandem type of spectrally selective solar absorber using a homogeneous multi-walled carbon nanotube (MWCNT) coating as absorbing layer has been fabricated. The MWCNT absorber was prepared by facile and efficient electrophoretic deposition and exhibited good spectral selectivity. To assess the durability of the MWCNT absorber, condensation and thermal stability accelerated ageing tests were performed according to the international standard ISO 22975-3: absorber surface durability. The primary results revealed that the MWCNT absorber had a great thermal stability but was not resistant to condensation since the porous MWCNT coating permits water migration through the pores down to the aluminum substrate which as a result oxidizes, confirmed by the analysis of Energy Dispersive Spectroscopy. Therefore, different types of thin films such as dense silica, silica-titania were deposited on top of MWCNT absorbers as protective layer to prevent the penetration of condensed water. Although all MWCNT absorbers coated with protective layer had little or no gain in spectral selectivity compared to those without protective layer, accelerated ageing tests indicated that the long-term durability was significantly improved. In thermal stability test, all protective layer coated MWCNT absorbers showed similar performance to the uncoated samples and had a negligible or even negative performance criterion (PC) value after 600 h testing. In condensation test, the obtained PC values were 0.002, 0.013 and 0.014 for silica, 70/30 and 50/50 silica-titania film coated MWCNT absorbers respectively. All the PC values were less than 0.015 after 600 h of accelerated ageing tests, which confirmed that the absorbers were qualified according to ISO 22975-3. (C) 2016 Elsevier B.V. All rights reserved.