In recent years, significant interest has developed in using sunlight for electricity-free vapor generation due to its potential to address limitations in fresh water availability around the globe. However, conventional techniques for generating vapor from solar energy typically rely on costly and cumbersome optical concentration systems to enable bulk heating of a liquid, resulting in relatively low efficiencies. This project explores a new way to use solar energy to generate vapor below room temperature ("cold vapor") for solar and thermal energy management applications. Importantly, the interdisciplinary nature of this project provides an excellent educational opportunity for Electrical Engineering and Materials Science curriculum development, integrated outreach activities and student training of the next generation researchers and educators.
This project considers a new process of solar vapor generation, i.e., when the evaporation temperature is lower than the room temperature. In this case, the system does not lose energy through conventional conduction, convection and radiation loss channels. Instead, the environment provides additional thermal energy for vapor generation, resulting in a total vaporization rate higher than the upper limit that can be produced using the input solar energy alone. Therefore, the total vapor generation rate can surpass the upper limit set by the input solar energy. This is the major research aim to be studied in this project: i.e. how to realize cold vapor generation below room temperature under regular sun illumination. Additionally, this project also explores moisture condensation at temperatures below ambient using radiative cooling technologies. In pursuit of these goals, this project identifies two major objectives: the first is to explore the fundamental properties of a cold solar-vapor generation system under different solar illumination conditions. The second objective is to explore the possibility of moisture condensation in a cold environment using radiative cooling technologies. The proposed research will offer a novel direction to explore and develop different water evaporation strategies, which may have applications in solar still technology, evaporative cooling and solar evaporated mining applications, evaporation-driven generators and recently reported water-evaporation-induced electricity.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
