Ewa Wäckelgård

Solution-chemical derived nickel–alumina coatings for thermal solar absorbers

Abstract A promising novel solution-chemistry method to fabricate spectrally selective solar absorber coatings has been investigated. The selectively absorbing film consists of nickel nano-particles embedded in a dielectric matrix of alumina. Ejecting a precursor solution of nickel and aluminum onto an aluminum substrate using a spin-coating technique followed by a heat-treatment, generated the solar absorber samples. Smooth and homogeneous films with a nickel content of 0 to 80 vol.% were produced. The optimal coating had a nickel content of 65%, a thickness of 0.1xa0μm and a particle size of ∼10 nm. The absorbing layer attained a normal solar absorptance, αsol, of 0.83 and a normal thermal emittance, etherm, of 0.03. Adding an anti-reflection layer on top of the first absorbing layer further enhanced the performance of the absorber. The optimum anti-reflection coated sample reached a solar absorptance of 0.93 and a thermal emittance of 0.04.

The influence of climate and location on collector performance

The influence of annual climate variations on the performance of solar thermal collectors in the northern part of Europe has been investigated. The annual solar collector energy output has been calculated with the MINSUN simulation program using hourly, measured climatic data for the years 1983–98 for three cities situated in the south (Lund), central (Stockholm) and north (Lulea) of Sweden. A synthetic year created with the Meteonorm weather simulation program was also used in the simulations. Two solar thermal collectors were modelled: a flat plate solar collector and a tubular vacuum collector, both of commercial standard.