4-fold enhancement in energy scavenging from fluctuating thermal resources using a temperature-doubler circuit

Summary Oscillating thermal resources are ubiquitous thanks to the diurnal cycle and are also found in nonsolar settings. Yet in isolation, oscillating thermal resources cannot normally generate electricity because standard heat engines require two thermal terminals, a source and a sink, and hence the engine’s second terminal is typically connected to some nearby constant-temperature reservoir. As an alternative, here we introduce the “temperature doubler” thermal circuit, based on two thermal diodes and two thermal capacitances. Modeling reveals how the electrical power output depends on the thermal diodes and masses. Benchtop experiments match the modeling well with no free parameters. Experiments further show that the temperature doubler generates four times more electricity than a conventional approach using a static heat sink, with a theoretical limit of an 8-fold enhancement for perfect thermal diodes and large thermal masses. This study shows how high-performance nonlinear thermal elements enable new approaches to more effective thermal-to-electrical energy conversion.