Collaborative Research: Designing Thermophotonic Materials for Passive Radiative Cooling

被动辐射冷却允许在不输入外部能量的情况下在环境条件下进行冷却。它包括一个与外层空间直接交换电磁热能的辐射热体，一个巨大而极冷的热沉。被动辐射冷却可以使制冷和气候控制更有效地运行，节省大量能源。然而，由于阳光的吸收，传统的辐射降温在白天不起作用。实现有效的被动辐射制冷的难点在于控制制冷系统中热辐射、光吸收和换热等相互竞争的机制的能量交换。该奖项支持基础研究，为能够满足严格的光学和热要求的热光材料的设计和加工提供知识。这些新的热光材料将通过优化设计的微观结构材料来实现，这些材料可以通过微米和纳米制造来定制，以产生所需的光学和热响应。有了这种材料，外层空间寒冷的黑暗可以被用作可再生的热力学资源，在地球上提供被动冷却。这项研究将包括对亚微米和纳米结构材料的光学反射、吸收和热传递行为的预测建模，以了解热光耦合的本质和材料性质的非线性。将创建一种基于拓扑优化的方法来系统地探索设计空间，并识别多种纳米结构材料的可行性。这种方法将考虑热光耦合、光谱选择性和可制造性限制。这将导致新的微米和纳米结构材料系统的发现，这些材料系统具有有效的材料特性，满足白天被动辐射冷却的严格热和光学要求。最终的设计将通过实验样机进行验证。如果成功，这项研究将产生颠覆性的热光材料系统，可以在白天导致低于环境温度的冷却，而不需要外部能量输入。

Passive radiative cooling allows for cooling below ambient conditions without the input of external energy. It involves a radiative thermal body directly exchanging electromagnetic thermal energy with outer space, an enormous and extremely cold heat sink. Passive radiative cooling can make refrigeration and climate control run more efficiently, saving significant amounts of energy. However, traditional radiative cooling does not work during the daytime because of the absorption of sunlight. The difficulty in realizing effective passive radiative cooling lies in controlling the energy exchange for the competing mechanisms of thermal radiation, optical absorption and heat transfer in the cooling system. This award supports fundamental research to provide the knowledge for the design and processing of thermophotonic materials that can meet the stringent optical and thermal requirements. These new thermophotonic materials will be realized through optimally designed, microscopically structured materials that can be tailored through micro- and nano-fabrication to produce the desired optical and thermal responses. With such material, the cold darkness of outer space can be leveraged as a renewable thermodynamic resource for providing passive cooling here on Earth. This research will involve predictive modeling of optical reflection and absorption and heat transfer behaviors of sub-micro- and nano-structured materials in order to understand the nature of thermophotonic coupling and the nonlinearity of material properties. A topology optimization-based method will be created to systematically explore the design space and to identify the viability of multiple nano-structured materials. This method will account for thermophotonic coupling, spectral selectivity, and manufacturability constraints. It will lead to the discovery of new micro- and nano-structured material systems that have effective material properties meeting the stringent thermal and optical requirements for passive radiative cooling during daytime. The resulting designs will be validated with experimental prototyping. If successful, this research will result in disruptive thermophotonic material systems that can lead to cooling below ambient temperature during the day without the need for external energy input.