Adaptive Phase Change Microcapsules for Efficient Sustainable Cooling
Shuqi Zhang, Guohao Xia, Qian Zhu, Zhao Wang, Geli Feng, Yawen Gong, Yu Zhang, Lei Zhang, Yinan Zhang, Tong Wang
Abstract
Passive radiative cooling has recently gained significant attention as a highly promising technology that offers a zero-energy and electricity-free solution to tackle the pressing issue of global warming. Nevertheless, research efforts have predominantly focused on enhancing daytime and hot-day radiative cooling efficacy, often neglecting the potential downsides associated with excessive cooling and the consequent increased heating expenses during cold nights and winter days. Herein, we demonstrate a micro-nanostructured engineered composite film that synergistically integrates room-temperature adaptive silica-shell/oil-core phase change microcapsules (S-PCMs) with commercially available cellulose fibers. The resultant composite film exhibits a solar reflectance of 0.92 and a mid-infrared emissivity of 0.96, achieving a remarkable average daytime subambient cooling of 7.5 °C under direct sunlight in hot conditions. Encouragingly, upon reaching the phase transition temperature, the heat previously absorbed and stored by S-PCMs is released, resulting in a temperature elevation of the composite film with an average temperature differential of merely 3.0 °C compared to surrounding air. The exceptional latent heat storage capability of our S-PCMs/cellulose composite film mitigates the radiative overcooling effect and substantially diminishes the heating demand, particularly across a diverse array of environmental conditions.