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

• Applicant: Professor Dr.-Ing. Stephan Kabelac
• Subject Area: Technical Thermodynamics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449554201

This is an application for the continuation of a project which aims for the experimental characterization and modelling of an electrochemical thermocell. The thermocell under consideration is analogous to a polymer electrolyte membrane (PEM) fuel cell, in which humidified hydrogen of different temperature is supplied to both electrodes. The hydrogen ions migrate from the anode to the cathode due to a temperature-related difference in its chemical potential, thereby contributing a (small) electrical output. In contrast to the already well-developed thermoelectric generators based on semiconductors, this thermoelectric cell is suitable for waste heat utilization at low temperatures (<100 °C) and moderate temperature differences of around 50 K. Due to the strongly coupled transport mechanisms in the electrolyte, the model developed is based on a non-equilibrium approach from the field of thermodynamics of irreversible processes (TiP). The phenomenological coefficients required for this model approach were measured in the current project phase with the help of an experimental setup in a broad field of parameters, so that the new model is already able to largely reproduce the Nernst-cell voltage, for example as a function of a gradient of the chemical potential of water. The remaining deviations are probably due to insufficient model depth in the calculation of the chemical potential of water in the electrolyte, so that there is a need for improvement here. In addition, further measurements are to be carried out on the characteristic field of the electrochemical thermocell with a closed circuit under load. The simulation model will be used to identify optimization potential, for example with regard to gas composition, membrane properties and catalyst assignment. This basic research-oriented project is to be concluded with the design of a prototype.

• DFG Programme: Research Grants