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SEMINAR: Control of light and heat for new energy applications
April 22, 2019 @ 10:00 am - 11:00 am
Light carries energy and heat, and plays a key role in many energy conversion processes. The strong interaction between light and matter in nanostructures provides new ways for tailoring thermal radiation, and represents important opportunities for novel energy applications and advanced thermal control. In this seminar I will present two sets of studies integrating experiment and theory. Firstly, I will discuss how near-field radiative heat transfer enables novel energy conversion and active refrigeration. I will show an experiment achieving a 40-fold enhancement of thermophotovoltaic conversion rates, by maintaining a nanoscale gap between a thermal emitter and a photovoltaic cell. This lays the foundation for high performance waste heat recovery. I will then show an observation of active refrigeration through control of the chemical potential of photons. This points to a fundamentally new, promising way for solid state refrigeration by combining nanoscale photonics and optoelectronics.
In the second part, I will discuss how to turn the cold space to a thermodynamic resource for passive cooling and energy efficiency. I will introduce our first demonstration of passive radiative cooling to below the ambient air temperature under direct sunlight. Then I will approach the limit of such cooling, achieving 42 ˚C below the ambient temperature, pointing to new applications such as food preservation in remote areas. I will show results of lowering the temperature of a solar absorber by 13 ˚C while maintaining the sunlight absorption, pointing to significant efficiency improvement for solar cells. Finally, I will give an overview of my future research directions.
Dr. Linxiao Zhu is currently a postdoctoral research fellow with Prof. Pramod Reddy and Prof. Edgar Meyhofer in Department of Mechanical Engineering at the University of Michigan, working on the experiments of near-field based energy conversion and refrigeration. Dr. Zhu received B.S. in Physics (2010) at the University of Science and Technology of China, and Ph.D. in Applied Physics (2016) at Stanford University. His doctoral research is on controlling electromagnetic heat transfer using photonic structures, supervised by Prof. Shanhui Fan. .