Experimental demonstration of high-temperature (>1000 °C) heat extraction from a moving-bed oxidation reactor for thermochemical energy storage

• Published in: Applied energy 2023-11, Vol.349 (C), p.121625, Article 121625
• Main Authors: Hayes, Michael, Korba, David, Schimmels, Philipp, Klausner, James, Petrasch, Jörg, AuYeung, Nick, Li, Like, Randhir, Kelvin
• Format: Article
• Language: English
• Subjects: Energy efficiency; Heat extraction; Oxidation reactor; Round-trip efficiency; Thermochemical energy storage
• ISSN: 0306-2619
• DOI: 10.1016/j.apenergy.2023.121625

Previously developed reduction-oxidation (redox) thermochemical energy storage technologies must store their products at high temperatures, complicating handling and transportation. This work describes a countercurrent, tubular, moving bed oxidation reactor at laboratory scale that produces high grade heat and allows solids to enter and exit the system at ambient temperatures. The particles implemented in the system consist of a novel magnesium‑manganese-oxide material well-suited for thermochemical energy storage. Output heat is obtained via a separate extraction gas flow, which exits from the middle portion of the main reactor tube. With this design, reactor temperatures in excess of 1000 °C and extraction temperatures above 950 °C were achieved. Deviation between the two measurements is a result of extraction thermocouple placement and losses in the reactor extraction arm; improvements to these parameters would bring the extraction temperature closer to the bed temperature. The reactor produces enough energy via oxidation to sustain both heat extraction and continued chemical reaction. During one representative steady state experiment at a particle flow rate of 1.5 g/s, an average of 447 W was extracted from the reactor out of an estimated 1083 W of released chemical energy for a duration of 70 min. Among the four experiments, the maximum bench-scale oxidation reactor energy efficiency of 36.2% and corresponding round-trip efficiency of 13.7% considering both redox reactors were demonstrated. Characteristics of an ideal system are considered and future improvements are proposed. •A novel tubular moving-bed oxidation reactor design was described.•Reaction temperatures >1000 °C and extraction temperatures >950 °C were achieved.•The reactor can sustain both heat extraction and continued chemical reaction.•Oxidation reactor efficiencies between 24% and 36% were obtained.•Round-trip efficiencies with both redox reactors were calculated.