Improving the thermal efficiency of a solar water heater by using PCM with copper powder (Cu), silicon carbide (SiC), and boron nitride (BN) nano particles

• PCM enhanced with Cu, SiC, and BN nanoparticles improved thermal efficiency. • Solar fraction rose from 35% to 75% with nanoparticle-infused PCM. • Heat loss coefficient reduced from 22.5 to 14.3 W/m²·K with Cu-PCM. • Tank outlet temperature increased by optimizing collector height and loop separation. • System efficiency improved from 47.6% (no PCM) to 52% (with nanoparticle PCM). Solar water heaters as a renewable energy solutions technology are being increasingly requested globally and are a critical technology route towards achieving Sustainable Development Goal 7 (SDG 7) of ensuring access to affordable, reliable, sustainable, and modern energy for all. This research investigates the enhancement of solar water heater performance through the integration of phase change materials (PCMs) with three distinct nanoparticles: copper powder (Cu), silicon carbide (SiC), and boron nitride (BN). Results of statistical analysis showed that heat transfer rates enhanced by up to 71.9%, relative to conventional PCM, were achieved with Cu nanoparticles as a result of varying thermal conductivity enhancement compared to the rest of the nanoparticles. Thermal conductivities of silicon carbide (SiC) nanoparticles in the 82–100 W/m·K range led to a 25% composite material thermal conductivity increase. The system's heat retention performance was improved by up to 60 percent, largely due to the thermal stability of boron nitride (BN) nanoparticles. The incorporation of these nanoparticle enhanced PCMs yielded large gains in system efficiency. With optimized configurations, the solar fraction was increased to 75%, from 35%, and the heat loss coefficient was reduced to 14.3 W/m²·K from 22.5 W/m²·K. These improvements are in line with targets under SDG 7, by increasing energy efficiency and growing the share of renewable energy in the global energy mix. The system validated the Energy Efficiency by SDG 7 initiative to double the rate of energy efficiency improvements by 2030 with overall efficiency improvement 47.6% without PCM, to 52.0% with nanoparticle-enhanced PCM.