A review of thermally regenerative electrochemical systems for power generation and refrigeration applications

Highlights: • The fundamental of the thermally regenerative electrochemical cycle is presented. • Potentials of thermally regenerative electrochemical systems are discussed. • Both theoretical and experimental studies are discussed. • Practical suggestions on the application of TREC are provided for future work. Nowadays, waste heat recovery and refrigeration are leading energy challenges. For the generation of additional power and refrigeration purposes, many systems were used. Among these systems, a modern electrochemical cycle based on the temperature dependence of the electrodes called thermally regenerative electrochemical cycle (TREC) was considered widely for converting heat to electricity and refrigeration. These systems have a high-temperature coefficient, which is an advantage over thermoelectric systems, high efficiency, low weight and volume, silent operation, sustainably generating power, no moving parts such as compressors, non-use of vulnerable refrigerants for environmental and clean technology, and ability to couple to various energy technologies to increase the energy efficiency of these systems. Also, an enormous amount of low-grade heat exists around us in energy technologies, such as photovoltaic technology, solar/geothermal heat, the waste heat of fuel cells, industry section and conversion and recovery of this low-grade heat is crucial. Therefore, reviewing the current state-of-the-art research and the progress on the thermally regenerative electrochemical systems for power generation and refrigeration focusing on the new material and design mechanism is essential. First, the principle of power generation cycle, TREC, and the refrigeration cycle, thermally regenerative electrochemical refrigeration (TRER), were utterly discussed for a better understanding of the cycles. Furthermore, the continuous system for these cycles was introduced for continuous power generation and refrigeration. Forasmuch as theoretical studies form the basis of experimental works, the power generation and refrigeration applications of these cycles were divided into theoretical and experimental studies. A literature review revealed that theoretical studies on both the TREC and TRER cycles are comprehensive, paving the way for experimental studies. In experimental studies, useful studies have been performed on power generation by this cycle and its continuous form system. However, despite the high potential of refrigeration cycle, very few studies have been done in this regard. Finally, some recommendations for future studies were made.