Preparation and thermal analysis of MWCNT-enhanced optimal ultra-high concentration Eicosane PCM nanoemulsions for net zero energy buildings

• Energy storage performance of MWCNT assisted Eicosane PCM nanoemulsions was investigated. • MWCNT Eicosane PCM nanoemulsions were manufactured at different concentrations of eiocsane and MWCNT nanoparticles. • Melting and freezing latent heat of MWCNT Eiocsane PCM nanoemulsions shifted with increasing PCM concentration. • 0.2 wt% MWCNT and 50 wt% Eicosane PCM nanoemulsion exhibited lowest degree of supercooling. This study presents the development and detailed thermal evaluation of ultra-high-concentration eicosane phase change material (PCM) nanoemulsions enhanced with multi-walled carbon nanotubes (MWCNTs), aiming to advance thermal energy storage (TES) performance in net zero energy building (NZEB) applications. Nanoemulsions were prepared with varying eicosane concentrations (10–50 wt%) and MWCNT concentrations (0–0.2 wt%). DSC results revealed that the LHF increased substantially with higher eicosane content, reaching 138.5 J/g at 50 wt% eicosane with 0.2 wt% MWCNT, compared to 116.1 J/g without MWCNT, while pure eicosane exhibited an LHF of 251.3 J/g. Notably, the addition of MWCNTs led to a dramatic reduction in the T sc , decreasing from 13.5 °C in emulsions without MWCNTs to as low as 0.4 °C at 0.2 wt% MWCNT, marking a ∼ 97 % improvement. Dynamic light scattering (DLS) analysis showed that droplet size increased from 588.2 nm at 0 wt% MWCNT to 767 nm at 0.2 wt% MWCNT for the 50 wt% eicosane system while maintaining excellent dispersion stability, as indicated by zeta potential values between − 70.76 and − 62 mV. Viscosity measurements demonstrated that at 50 wt% eicosane, viscosity rose from 20 mPas (without MWCNT) to 142 mPas at 0.2 wt% MWCNT, reflecting the formation of a stable nanoparticle network that supports structural integrity without hindering pumpability.