Solar Net Collective Flux and Conversion Efficiency of the Nickel-Pigmented Aluminium Oxide Selective Absorber Prepared by Alternate and Reverse Periodic Technique in Different Prototype Volumes

Different constructed prototypes of different volumes were used to test different nickel- pigmented aluminium oxide selective absorber samples for photo thermal conversion. Different types of solar net collective flux (average, accumulative, maximum, minimum) were calculated. We found that there is a good linear mathematical relationship between the solar net collective fluxes with the prototype volume in the range 500 – 8000 ± 1 cm3. Comparison between aluminium alloy, copper sheet, and the nickel-pigmented aluminium oxide selective absorber for net collective flux with nickel content and prototype volume were done. The highest net collective flux is for the sample of nickel content 60μg/cm2 where: during a day, the accumulative net collective flux is 5586±1 W/m2; while the average net collective flux is 372.4±0.1 W/m2 in prototype of volume 500±1 cm3. The lowest net collective flux is for the sample of nickel content 92μg/cm2, where: during a day, the accumulative net collective flux is 4393±1 W/m2; the average net collective flux is 292.9±0.1 W/m2 in prototype of volume 8000±1 cm3 .The percent conversion efficiency and absorption of merit are constants for all samples in all prototypes. The maximum average percent conversion efficiency is for sample of nickel content 60μg/cm2 which lies in the range (72.0-74.0±0.1) %. However the least average percent conversion efficiency is for the sample of nickel content 92μg/cm2 which lies in the range of (61.0-69.0±0.1) %. The best mathematical relations between the net collective flux and prototype volume were calculated. The correlation coefficients squared for all calculations are 0.91 on average.