Durability of thermochemical heat storage demonstrated through long-term repetitive CaCl2/H2O reversible reactions

Abstract

Thermochemical heat storage is a promising technology for improving thermal energy efficiency. In this study, CaCl2 and H2O were selected as the reactant and working medium, respectively, assuming the utilization of low-grade waste heat. To investigate the durability of the CaCl2/H2O reaction, 1000 repetitive operations were conducted at the same 110 °C charging and discharging temperatures. During the long-term repetitions, a decrease in the average volumetric power density was observed. The peak value in repetitions 901–1000 was 11% lower than the peak value in the initial 50 repetitions. This trend was mainly caused by a decrease in the heat transfer rate; it was observed after the repetitive experiments that reactant particles had moved out of the heat exchanger. Although a decreasing trend in the power density was observed, a peak value of Q = 320 kW/m3 and a conversion ratio of approximately 0.7 were observed in repetitions 901–1000. In addition, approximately 90% of the stored heat was released in all 1000 repetitions. Thus, using long-term repetitions (1000), this study confirmed the durability of the CaCl2/H2O reaction for thermochemical heat storage.

Chemical Heat Storage Using an SiC Honeycomb Packed with CaCl<sub>2</sub> Powder

“…However, during heat storage, the outlet temperature of the heat exchange fluid was lower than the inlet temperature. To compare the SiC honeycomb-and aluminum corrugated fin-type reactors [6]. The heat output and conversion ratio is shown in Figure 4.…”

“…The CaCl 2 /H 2 O reaction system was adopted, which involves a reversible chemical endothermic or exothermic reaction, as follows. The material used in this system is environmentally sustainable, commonly used, readily available, nontoxic, and chemically stable [6], and the working temperature is below 200˚C. Moreover, the CaCl 2 /H 2 O reaction system has already been studied for chemical heat storage, and the potential use of both sides of the reversible CaCl 2 /H 2 O reaction has been demonstrated in previous studies [6].…”

Possibility of Calcium Oxide from Natural Limestone Including Impurities for Chemical Heat Pump

“…For chemical heat storage materials, CaCl 2 and H 2 O were selected as the reactant and working medium, assuming the utilization of low-grade waste heat [6]. Li et al investigated the hydration and dehydration reaction of lithium hydroxide (LiOH) for low temperature heat sources [7].…”

Experimental Evaluation of the Heat Output/Input and Coefficient of Performance Characteristics of a Chemical Heat Pump in the Periodic Operation of CaCl<sub>2</sub> Hydration

“…Among these technologies, the chemical heat pump (CHP), driven by reversible chemical reactions, is a promising technology for contributing to the need to utilize thermal energy. Studies have suggested a number of natural high-affinity refrigerant and reactant pairs, including H 2 O [9], NH 3 [10], and CO 2 [11] for refrigerants and solid oxides and metal halides for reactants. To date, CHPs have been investigated in a number of cycle modes, namely heat storage, heat upgrading, and chiller heat modes.…”