Performance study of spectral-splitting concentrated photovoltaic/thermal systems integrating spiral-finned tubes and graphene-enhanced phase change materials

Spectrally beam splitting concentrated photovoltaic/thermal (SBS-CPV/T) systems incorporating advanced cooling with finned-spiral serpentine coils embedded in phase change materials (PCMs) offer a promising strategy for maximizing solar spectrum utilization. This paper numerically presents a performance analysis of five SBS-CPV/T systems using various spiral coil configurations: smooth tube (ST), solid annular fin (SAF), perforated annular fin (PAF), solid longitudinal fin (SLF), and perforated longitudinal fin (PLF) serpentines, evaluated at different concentration ratios. The effect of adding spheroidal graphene nanoplatelets to the PCM at 1–3 vol% is then investigated for the optimal configuration. Finally, all spiral coil configurations with 3 vol% of graphene nanoplatelets are compared using various performance metrics. The SBS-CPV/T system with PLF exhibits the best overall performance across all concentration ratios. As this parameter increases from 5 to 20, the merit function decreases by 38.19 % (ST), 46.7 % (SAF), 46.9 % (PAF), 47.18 % (SLF), and 47.6 % (PLF). At concentration ratio of 20, adding 3 vol% of graphene nanoplatelets to the best design boosts the merit function, electrical efficiency, overall thermal efficiency, total primary efficiency, and overall exergy efficiency by 22.2 %, 9.3 %, 57 %, 30.9 %, and 12.3 %, respectively, while reducing cell temperature by 17 °C compared to the pure PCM.