An Open-Source Dual-Channel RTD Thermal Control Platform for Research-Scale PEM Water Electrolysis Balance-of-Plant Integration

Abstract

Inter-laboratory variation in proton exchange membrane water electrolysis (PEMWE) test bench balance-of-plant systems has contributed to significant disparity in published single-cell polarisation performance data, limiting experimental reproducibility and comparison between laboratories. Harmonisation efforts identify precise low-contamination thermal control of process fluid and cell hardware as a benchmarking requirement. This paper presents the Thermal Stability Regulatory Control Tool (TSRCT-PCB-01), an open-source dual-channel MAX31865-based resistance temperature detector (RTD) thermal control platform for PEMWE research, with independent dual-loop sensing and actuation, data logging, and configurable overtemperature shutdown logic. Single-step open-loop characterisation of an isolated endplate, without process fluid flow or an operating electrolysis cell, is used to model a lag-dominant first-order-plus-dead-time plant (R2=0.9996; RMSE=0.247 °C; MAE=0.198 °C; τp/θ≈136), informing analytical gain derivation and subsequent experimental comparison of Skogestad SIMC PI and iSIMC PID tunings. Across all analysed post-settling intervals, absolute mean indicated offsets were below 0.004 °C and standard deviations were below 0.030 °C. Measured peak-to-peak spans ranged from 0.0687 °C to 0.3429 °C. Compatibility with fluorinated ethylene propylene (FEP) sensor encapsulation supports an all-fluoropolymer wetted path. TSRCT-PCB-01 is the sensing, control, and actuation module of the broader TSRCT-600 high-purity inline thermal control system. Hardware, firmware, and tuning tools are openly available through GitHub and archived in Zenodo to support reproducible electrochemical testing.

The authors' abstract, as published at the source. Energies, 2026 · DOI ↗