Numerical investigation of PCM-filled pin-fin microchannels for thermal management of HCPV cell

• The study to embed PCM in cavities with water flow in Pin-Fin microchannel. • The inclusion of PCM in pin-fin microchannels significantly reduces cell residual heat. • Latent heat dominates at low Re, convection at higher Re. • Multi-PCM cavities delay peak cell temperature rise. • Promising hybrid system for compact and efficient solar cooling. High-Concentration Photovoltaic (HCPV) systems offer high solar-to-electric efficiency but face severe thermal challenges under intense solar flux, requiring advanced cooling solutions. While microchannel cooling and PCM integration have been studied separately, the use of PCM-filled cavities within pin-fin structured microchannels remains largely unexplored. This study presents a numerical investigation of a novel hybrid cooling system that integrates PCM-filled cavities in the copper substrate and pin-fin microchannels, combined with water circulation, to improve HCPV thermal management. The cooling performance was evaluated using three PCMs (RT‑35, RT‑42, and Composite PCM (CPCM)), two cavity layouts (single vs. multi‑cavity with pin-fin mini-cavities), and two flow modes (continuous vs. delayed) over Reynolds numbers (Re = 50–200), and compared to a conventional solid pin-fin microchannel. Results show CPCM outperformed other PCMs by maintaining lower cell temperatures, particularly at moderate Reynolds numbers (Re = 100 and 150). At Re = 150, the CPCM-based system improved electrical efficiency by 1.4% and achieved up to 12% higher latent heat absorption. Power analysis comparison further confirmed that the multi-cavity CPCM with delayed flow produced the highest output power fraction (≈94–95%) with modest pumping penalties. Overall, the hybrid “latent-first, convection-second” approach using multi-cavity CPCM with delayed flow provides the most efficient and energy-effective thermal management for HCPV systems, improving electrical efficiency and supporting sustainable solar energy solutions.