Scalable Nernst Thermoelectric Power using a Coiled Galfenol Wire

TL;DR

This paper demonstrates a scalable Nernst thermoelectric generator using a coiled Galfenol wire around a hot cylinder, achieving a giant Nernst coefficient and potential for waste heat recovery on non-flat surfaces.

Contribution

It introduces a novel coil geometry with Galfenol wire to generate Nernst voltage from radial temperature gradients, showing scalable power generation capabilities.

Findings

Nernst voltage scales linearly with wire length.

Giant Nernst coefficient of -2.6 μV/KT at room temperature.

Feasibility of transverse thermoelectric generator for non-flat heat sources.

Abstract

The Nernst thermopower usually is considered far too weak in most metals for waste heat recovery. However, its transverse orientation gives it an advantage over the Seebeck effect on non-flat surfaces. Here, we experimentally demonstrate the scalable generation of a Nernst voltage in an air-cooled metal wire coiled around a hot cylinder. In this geometry, a radial temperature gradient generates an azimuthal electric field in the coil. A Galfenol (Fe$_{0.85}$Ga$_{0.15}$) wire is wrapped around a cartridge heater, and the voltage drop across the wire is measured as a function of axial magnetic field. As expected, the Nernst voltage scales linearly with the length of the wire. Based on heat conduction and fluid dynamic equations, finite-element method is used to calculate the temperature gradient across the Galfenol wire and determine the Nernst coefficient. A giant Nernst coefficient of -2.6 ${\mu}$V/KT at room temperature is estimated, in agreement with measurements on bulk Galfenol. We expect that the giant Nernst effect in Galfenol arises from its magnetostriction, presumably through enhanced magnon-phonon coupling. Our results demonstrate the feasibility of a transverse thermoelectric generator capable of scalable output power from non-flat heat sources.