Hollow spherical SiO2 micro-container encapsulation of LiCl for high-performance simultaneous heat reallocation and seawater desalination

Abstract

Energy & fresh water have both become scarce resources in the modern era of human society. Sorption-based technology is environmentally friendly and energy-efficient and can be driven by low-grade energy to transfer energy and produce fresh water. Here, we report a solid sorbent fabricated by encapsulating a hygroscopic salt, lithium chloride (LiCl), inside micro-sized hollow-structured SiO₂. This composite sorbent (LiCl@HS) exhibits 6 times faster water vapor sorption kinetics than pure LiCl and a water vapor sorption capacity of 1.7 kg kg⁻¹ at a relative humidity (RH) of 50%, which is the highest ever reported for any solid sorbent in the literature. The low regeneration temperature (<80 °C) and good cycling stability ensure the feasibility of the composite sorbent for use in practical applications. The thermodynamic calculations reveal that the sorbent is able to continuously supply 20 °C temperature lift with a maximum coefficient of performance (COP) for cooling of 0.97 and COP for heating of 1.89 while simultaneously producing 9.05 kg potable water per kilogram sorbent daily using seawater as the source water and solar energy as the sole energy source. A homemade system is developed and its practical performance in providing seasonally switchable heating and cooling along with clean water production from source water with an impaired quality is successfully verified, indicating its great potential.