Opinions on glycerol-based deep eutectic solvent nanofluids for energy transportation

Working fluids, working as a medium for energy transportation, play an important role in both thermal energy transportation and thermal management. Traditional heat transfer media, such as water, organic solvents, and mineral oils, have been unable to meet the increasing efficiency demand for heat transfer (Zhang et al., 2021; Esfe et al., 2022; Kursus et al., 2022; Younes et al., 2022). Generally speaking, the thermal conductivity of a nanoparticle is usually higher than that of a liquid; out of this consideration, Eastman et al. (2001) improve the heat-transfer performance of the fluid by adding nanoparticles to the base liquid and named nanofluids for the first time. Nanofluids have been widely used in many fields due to their good thermal properties; many researchers study the application prospects of nanofluids in the field of solar heat collection by simulating the working state of nanofluids in the process of heat transfer (Wang et al., 2022) so as to improve the heat collection efficiency of the collector and the stability and durability of the overall system (Figure 1A). A deep eutectic solvent (DES) is generally a eutectic mixture prepared by two or three components through the interaction between hydrogen bonds and has a wide application prospect (Walvekar et al., 2021). The raw materials are cheap, the preparation process is simple, and the thermophysical properties are excellent. At the same time, the liquid range of DES is a key concern, and the wide liquid range can meet the working requirements of working fluids under various climatic conditions.