Simultaneous Passive Cooling and Humidity Control via the Fiber-Encapsulated Gel Structure.

Radiative cooling is a promising technology that offers benefits such as reducing cooling energy demand, mitigating climate change impacts, and contributing to sustainable development. However, previous radiative cooling technologies are unable to manage humidity, which is crucial and energy-intensive in many applications. Therefore, it is necessary to extend the capabilities of radiative coolers to include humidity control. Here, we demonstrate a fiber-encapsulated gel structure (FEGS) to realize simultaneous radiative cooling and humidity control. By employing a phase equilibrium-based strategy, the FEGS can control relative humidity to any value between 30 and 80%. The changes in temperature, thermal conductivity, and water content during the regeneration process of FEGS were studied. Field tests demonstrated that the FEGS can achieve 5 °C subambient temperature reduction under direct sunlight while maintaining the relative humidity at a controlled level of 58 ± 3% for a continuous period of 3 days. This work can potentially pave the way for the comanagement of temperature and humidity in a passive, low-cost, and scalable way.