cfaed Seminar Series

Guiding, amplification, and control of electrical and thermal currents are of critical importance
to efficiently manage the energy resources present in nature. In electricity, this has been done
with diodes and transistors, which have allowed the development of almost all modern
electronics, while the conception of the thermal diode/transistor has recently emerged. These
fundamental thermal devices are based on the dielectric-metal transition of phase change
materials (PCMs) and were reported to provide fine control on heat currents, however up to
date, not so much attention has been put neither on the intrinsic thermal hysteresis of PCMs
nor on temperature control, which are considered in the present work.
The objective of this talk is to theoretically demonstrate that a thermal transistor with a PCM
base can be used as a thermal device for heating and cooling. This is done by exploiting the
effect of the PCM thermal hysteresis on the heat fluxes that the base exchanges with the
collector and emitter of the transistor. Based on the principle of energy conservation, we show
that these heat fluxes and the base temperature undergo significant jumps under a small
modification of the heat flux applied to the base. When the collector and emitter of the
transistor operate at 350 K and 300 K, respectively, a temperature jump of +18 K (-5 K) and a
coefficient of performance of 58% (32%) are obtained during the heating (cooling) of a VO2
base excited with 208 Wm-2 (63 Wm-2). This sizeable thermal effect is dominated by the photon
heat current and could provide an alternative and/or complement to the present refrigeration
and heating technologies involved in freezers, microwave ovens, and radiators used at home.