Modeling and Experimental Investigation of a Thermocell Based on a Polymer-membrane With Two Hydrogen Electrodes

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The aim of this project application is the experimental and theoretical investigation of a thermoelectrochemical generator, a so called thermocell. The thermocell considered here is constructed similar to a polymer electrolyte fuel cell, in which the anode is cooled to low (ambient) temperatures and the cathode is heated. At both electrodes moistened hydrogen (different temperatures) is provided for heating and cooling. This hydrogen is not consumed in total, but protons migrate from the anode to the cathode. In preliminary investigations, the basic functionality of this PEM thermocell could be proven to function as a thermoelectric generator. The specific features of this thermocell are, contrary to the well-known semiconductor type thermoelectric generator, a low operating temperature (<100°C) and moderate driving temperature differences (≃50K).When modeling this electrochemical energy converter, strongly coupled transport mechanisms must be considered, especially in the electrolyte. The proposed model is a non-equilibrium approach based on the thermodynamics of irreversible processes (TiP), with which coupled transport processes can be described systematically. The phenomenological coefficients required for this model approach are to be measured by means of the experimental setup. The setup will also be used to measure the current-voltage characteristics of the thermocell as a function of the temperature difference between anode and cathode and as a function of moisture of the hydrogen. With the help of the validated model, the overall potential of this energy conversion device can be estimated, and a first prototype with a closed hydrogen cycle could be designed for follow-up projects.