Thermal performance investigation of energy storage based U-pipe evacuated tube solar collector: An experimental study

Abstract

In this study thermal performance comparison of a custom made U-Pipe evacuated tube solar collector (ETC) vs commercially available heat pipe ETC (HPETC) was investigated experimentally. The performance comparison was performed over several days with and without thermal storage media. Results from testing without thermal storage media showed U-Pipe ETC achieved higher peak water temperatures than that of HPETC, maximum of 31 °C, resulting in 13% efficiency enhancement of U-Pipe ETC compared with HPETC. Results from testing with storage materials showed peak temperatures for fin and water tank of the U-Pipe ETC as 47 °C and 38.7 °C, respectively, whereas heat pipe showed values of 60 °C and 36.7 °C for max fin and water temperatures, respectively. Further performance enhancement to the U-Pipe ETC system was investigated through integration of phase change material (PCM)72 with added 1wt% multi-walled carbon nanotubes (MWCNT) nanoparticles. Peak temperatures recorded for this experiment were 63.9 °C and 43.3 °C for the U-Pipe fin and water tank, respectively. The results from this study show that the U-Pipe setup was able to achieve higher water temperatures than that of the HPETC setup. Incorporation of nano-PCM allowed for slower heat release in the water, extending useful duration of latent heat storage capability.