Increasing the efficiency of a continuous thermally regenerative electrochemical cycle system with concentration-based control and parallel operation

This work investigated efficiency enhancement in a continuous Thermally Regenerative Electrochemical Cycle using concentration-based control and intermittent pumping. The system consists of two electrochemical cells operated at 20 °C and 60 °C, which produced a nominal voltage of 56.2 mV under continuous circulation. Long-term tests confirmed stable operation over 50 h. When the pump was switched off, the voltage decreased to 54 mV and 53 mV after which regeneration restored the nominal level within 3–6 min. These measured discharge and recovery characteristics enabled the implementation of a periodic pump-control strategy. Compared to continuous pumping, intermittent operation increased net electrical energy output by approximately 10% after 1 h and 30% after 3 h, while reducing pump energy consumption during 70–85% of the operating time. Diffusion-based analysis yielded a critical current density of 5.6 Am −2 , above the experimental load of 1.1 × 10 −2 Am −2 , confirming operation in the volumetric region. The measured reaction rate corresponds to a depletion time of roughly 2615 s (≈ 43 min) without pumping. Scaling calculations showed that at 3 A load the profitability limit is reached after 86 min, while at 10 A a reduced switching threshold of 50 mV is required to maintain positive net performance.