Enhancement of solar PV/T systems through cellulose nanocrystal -based cooling

• The study demonstrates that cellulose nanocrystal (CNC) nanofluids substantially improve cooling efficiency in photovoltaic-thermal (PV/T) systems. • The optimal coolant flow rate of 0.9 L/min enhances electrical power output by up to 15.4 % and thermal energy recovery to 401 W. • CNC nanofluid reduces PV module surface temperature by 26 %, ensuring stable operation and prolonged lifespan. • The eco-friendly, biodegradable CNC-based coolant supports sustainable solar energy technologies aligned with global SDG objectives. The integration of efficient cooling strategies in photovoltaic-thermal (PV/T) systems is essential for improving energy conversion efficiency and operational stability. This study investigates the use of cellulose nanocrystal (CNC) nanofluids, prepared in a (40:60) ethylene glycol-water (EGW) base, as a sustainable and high-performance cooling medium. Both theoretical modeling and experimental analysis were conducted to assess electrical and thermal performance under varying coolant flow rates, ranging from 0.1 to 1.3 L/min. Results demonstrate that CNC nanofluids significantly reduce PV surface temperature and enhance system efficiency. The optimum performance was achieved at a flow rate of 0.9 L/min, resulting in notable improvements in electrical output and thermal dissipation. Maximum thermal energy reached 448 W, while electrical power output increased from 32 W (at 200 W/m²) to 155 W (at 1000 W/m²). Additionally, CNC nanofluids offer excellent thermal conductivity, stability, and eco-friendly characteristics. This research contributes to the advancement of green energy technologies and supports Sustainable Development Goals (SDGs) by promoting efficient, cost-effective, and environmentally sustainable solar energy solutions. The work's graphical abstracts are shown in Figure 1.