Measuring the thermal conductivity of membrane and porous transport layer in proton and anion exchange membrane water electrolyzers for temperature distribution modeling

Robert Bock,Håvard Karoliussen,Frode Seland,Bruno G Pollet,Magnus Skinlo Thomassen,Steven Holdcroft,Odne S Burheim

doi:10.1016/j.ijhydene.2019.01.013

Abstract

Water electrolyzers that use a membrane electrolyte between the electrodes are a promising technology towards mass production of renewable hydrogen. High power setups produce a lot of heat which has to be transported through the cell, making heat management essential. Knowing thermal conductivity values of the employed materials is crucial when modeling the temperature distribution inside an electrolyzer. The thermal conductivity was measured for different titanium-based porous transport layers (PTL) and a partially methylated Hexamethyl-p-Terphenyl Polybenzimidazolium (HMT-PMBI-Cl- membrane. The four titanium-based sintered transport layers materials have thermal conductivities between 1.0 and 2.5 ± 0.2 WK−1m−1 at 10 bar compaction pressure. The HMT-PMBI-Cl- membrane has a thermal conductivity of 0.19 ± 0.04 WK−1m−1 at 0% relative humidity at 10 bar compaction pressure and 0.21 ± 0.03 WK−1m−1 at 100% relative humidity (λ=12 water molecules per ion exchange site at room temperature) at 10 bar compaction pressure. Combining the determined thermal conductivity values with data from the literature, 2D thermal models of a proton exchange membrane water electrolyzer (PEMWE) and an anion exchange membrane water electrolyzer (AEMWE) were built to evaluate the temperature distribution in the through-plane direction. A temperature difference of 7–17 K was shown to arise between the center of the membrane electrode assembly and bipolar plates for the PEMWE and more than 18 K for the AEMWE.

Highlights

The possible success of the hydrogen economy is very dependent on viable and affordable technologies that enable mass production of hydrogen on the basis of renewable energies [1]
The results show that the difference in membrane thermal conductivity due to humidifaction does not have a significant influence on the temperature distribution
Thermal conductivity values for some key components were measured and reported for different compaction pressures and humidities. These were used in a 2D heat distribution model to analyze the temperature distribution through the membrane electrode assembly (MEA) in a PEM and an anion exchange membrane (AEM) water electrolyzer

Summary

Introduction

The possible success of the hydrogen economy is very dependent on viable and affordable technologies that enable mass production of hydrogen on the basis of renewable energies [1]. With the growing availability of renewable energy in many countries the chances for electrolytic hydrogen won from these sources increases. It can pose as an energy storage medium and an energy carrier, helping to balance the intermittency of renewable energy sources and to deliver this renewable energy where it might otherwise not be available [3]. The electrolytic process can be reversed to produce current, heat and water when demands peak and surplus electricity is needed. This conversion of chemical energy into electrical energy goes by means of a fuel cell. For some applications such a device that works both as a fuel cell and an electrolyzer is desirable as it can function as a local energy buffer and help to stabilize power demands

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Conclusion