Integrated near-field thermo-photovoltaics for on-demand heat recycling

TL;DR

This paper introduces a reconfigurable near-field thermo-photovoltaic platform that uses nano-electromechanical systems to enhance heat-to-electricity conversion by precisely controlling the gap between a hot emitter and a germanium photodetector, achieving significant power increases.

Contribution

It presents a scalable, integrated NEMS-based platform for controlled near-field heat transfer and energy recycling, enabling tunable and high-efficiency thermo-photovoltaic energy generation.

Findings

Over an order of magnitude increase in power generation at small gaps.

Demonstration of a tunable gap from 500 nm to 100 nm.

Low power consumption of the NEMS switch.

Abstract

The energy transferred via thermal radiation between two surfaces separated by nanometers distances (near-field) can be much larger than the blackbody limit. However, realizing a reconfigurable platform that utilizes this energy exchange mechanism to generate electricity in industrial and space applications on-demand, remains a challenge. The challenge lies in designing a platform that can separate two surfaces by a small and tunable gap while simultaneously maintaining a large temperature differential. Here, we present a fully integrated, reconfigurable and scalable platform operating in near-field regime that performs controlled heat extraction and energy recycling. Our platform relies on an integrated nano-electromechanical system (NEMS) that enables precise positioning of a large area thermal emitter within nanometers distances from a room-temperature germanium photodetector to form a thermo-photovoltaic (TPV) cell. We show over an order of magnitude higher power generation $\mathrm{P_{gen} \sim 1.25 \, \mu W \cdot cm^{-2}}$ from our TPV cell by tuning the gap between a hot emitter ($\mathrm{T_E \sim 880 \, K}$) and the cold photodetector ($\mathrm{T_D \sim 300 \, K}$) from $\mathrm{\sim 500 \, nm}$ to $\mathrm{\sim 100 \, nm}$. The significant enhancement in $\mathrm{P_{gen}}$ at such small distances is a clear indication of near-field heat transfer effect. Our electrostatically controlled NEMS switch consumes negligible tuning power ($\mathrm{P_{gen}/P_{NEMS} \sim 10^4}$) and relies on conventional silicon-based process technologies.