Tunable thermal management based on solar heating and radiative cooling

Abstract Solar heating (SH) and radiative cooling (RC) have been regarded as promising clean techniques for thermal energy harvesting and temperature control. However, SH and RC are only a single function of heat collection and dissipation, which means the static device of SH and RC cannot meet the dynamic heat requirement of real-world applications, especially in the daytime. Here, a strategy of dynamic integration of SH and RC is proposed for tunable thermal management. A device (i.e., SH/RC device) that includes a silica cavity, ultrapure single-walled carbon nanotubes (SWCNTs) aqueous dispersion, solar reflective film, and deionized water is designed and fabricated. The outdoor experimental results show that the SH/RC device with SWCNTs media can effectively achieve heat collection with a maximum temperature of 78.9°C, while the SH/RC device with deionized water can achieve heat dissipation. Besides, the temperature modulation ability of the SH/RC device is tested to be 26.3°C and can be theoretically improved to be 60.3°C by improving the solar absorptivity (i.e., 0.9 for SH mode and 0.1 for RC mode) regulation ability of the device and improving its thermal emissivity (i.e., 0.9). Furthermore, annual analysis indicates that the cumulative time in which the SH/RC device temperature is in a comfortable region (i.e., 20°C-26°C) for humans is 60.9% and 30.3% higher than that of the device with individual SH and RC mode. In summary, this work provides alternative thinking for tunable thermal management based on the dynamic utilization of the hot sun and cold universe.