Atomic Scale Control of Thermal Radiation for Passive Cooling of Buildings
Stanford Energy Research Consortium (SERC)
Background
The most important thermodynamic resources, the hotness of the sun, and the coldness of the universe, are accessible to humankind through thermal radiation management. The ability to control the fundamental properties of thermal radiation can provide new opportunities to exploit these resources to provide cooling in buildings. This project addresses the fundamental science underpinning the control of thermal radiation which could be vitally important in supporting global efforts to developing energy systems with no greenhouse gas emissions.
Figure 1: Key principles of thermal radiation management to achieve passive cooling (a) Major thermodynamic resources around the earth. (b)To achieve daytime radiative cooling, one needs to engineer a structure that achieves broad-band reflection of sunlight and strong thermal emission in the transparency window of the atmosphere. (c) A multi-layer structure deposited on a silicon wafer that functions as a day-time radiative cooler. Four layers of a nanoscale thickness are illustrated on the left panel. The dark and light regions correspond to HfO2 and SiO2 respectively.
Project Goals
In this project, the researchers aim to develop much more efficient thermal radiation management techniques that can assist in the passive cooling of buildings. The team will use 2-dimensional materials that have unique and tunable optical properties to achieve adjustable radiative cooling and optimize cooling performance. They will establish spectral, angular, and dynamic control at reduced weight and cost. The scientific insights on the fundamentals of light interacting with thin films and interfaces gained will be highly valuable. If successful, this work has the potential to significantly reduce the amount of electrical power that is currently used for air conditioning.
Approach
The researchers will focus on design of high-performance radiative coolers through computational optimization. Building on recent work that demonstrated dynamic control over the thermal emission from a nanometallic metamaterial device, the team will explore two avenues to achieve dynamic, self-adaptive radiative cooling systems. In one approach they will utilize structures where the light absorption properties of the 2D materials can be tuned with an applied bias between the 2D and the metallic substrate. In another approach, they will build a device that will enable cooling when the temperature of the environment is above a critical temperature and disable cooling when it is below. Phase change materials, such as vanadium dioxide (VO2) present a promising approach to construct a self-adaptive radiative cooler. These materials provide a valuable capability that is currently not available from 2D materials and can enable effective thermal management in very thin layers.
Team Members
Mark Brongersma
Mark Brongersma is a Professor in the Department of Materials Science and Engineering at Stanford University. The research in the Brongersma group is directed towards the development and physical analysis of new materials and nanostructures that find use in optoelectronic devices. His lab has been particularly active in the fields of metal-based optics (for which he coined the name Plasmonics in 1999), semiconductor nanophotonics, and 2-dimensional quantum materials (9 manuscripts in Science Magazine, 31 in Nature Sub-journals since 2010), and a highly cited researcher according to Clarivate Analytics). The first two fields of science are focused on manipulating light at the nanoscale using optically resonant nanostructures and well below the wavelength of visible light. The third field has aimed to identify and harness the unique physical properties of essentially 2-dimensional materials.
Shanhui Fan
Shanhui Fan is the Joseph and Hon Mai Goodman Professor in the School of Engineering at Stanford University, where he is a professor of Electrical Engineering. His research interests are in fundamental studies of nanophotonic structures, especially photonic crystals and meta-materials, and applications of these structures in energy and information technology applications. He has published over 600 refereed journal articles, given more than 300 plenary/keynote/invited talks, and holds over 70 granted U. S. patents. He pioneered the concept of daytime radiative cooling and provided the first theoretical proposal and the first experimental demonstration of daytime radiative cooling.
Other Team Members
Qitong Li, Postdoctoral Scholar, Materials Science and Engineering, Brongersma Group
Sid Assawaworrarit, Postdoctoal Scholar, Electrical Engineering, Fan Group