EAGER: Collaborative Research: Cold vapor generation beyond the input solar energy limit and its condensation using thermal radiation

近年来，由于有可能解决全球淡水供应的限制，人们对利用阳光进行无电蒸汽发电产生了极大的兴趣。然而，利用太阳能产生蒸汽的传统技术通常依赖于昂贵且笨重的光学浓缩系统来实现液体的大量加热，导致效率相对较低。该项目探索了一种利用太阳能产生室温以下蒸汽（“冷蒸汽”）的新方法，用于太阳能和热能管理应用。重要的是，该项目的跨学科性质为电气工程和材料科学课程开发、综合推广活动和下一代研究人员和教育工作者的学生培训提供了极好的教育机会。本项目考虑了一种新的太阳能蒸汽生成工艺，即蒸发温度低于室温。在这种情况下，系统不会通过传统的传导、对流和辐射损失通道损失能量。相反，环境为蒸汽的产生提供了额外的热能，导致总汽化率高于单独使用输入太阳能所能产生的上限。因此，总蒸汽产生率可以超过输入太阳能设定的上限。如何在常规光照下实现室温以下的冷蒸汽生成，是本课题主要研究的课题。此外，该项目还探索了使用辐射冷却技术在低于环境温度下的水分凝结。为了实现这些目标，本项目确定了两个主要目标：第一是探索不同太阳光照条件下冷太阳能蒸汽产生系统的基本特性。第二个目标是探索利用辐射冷却技术在寒冷环境中凝结水分的可能性。该研究将为探索和开发不同的水蒸发策略提供新的方向，这些策略可能在太阳能蒸馏技术，蒸发冷却和太阳能蒸发采矿应用，蒸发驱动发电机和最近报道的水蒸发诱导电力中得到应用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.