Development of pomegranate-type CaCl2@C composites via a scalable one-pot pyrolysis strategy for solar-driven thermochemical heat storage

Scalable Production of EP/CaCl2@C Multistage Core–Shell Sorbent for Solar-Driven Sorption Heat Storage Application

“…There were three components in the composite sorbent: carbon material, CaCl 2 , and EP. Carbon materials will burn out at high temperature in air, 43 while CaCl 2 and EP had thermal stability. Therefore, the weight loss was caused by carbon combustion when the composite sorbent was heated in air.…”

“…57,63 The carbon in the core−shell sorbent was formed from the carbonization of coal tar, which was inactive for water sorption so that the water uptake was lower with the increasing content of carbon in the composite sorbent. 43 The water uptake at equilibrium increased from 0.59 g-H 2 O/g-sorbent (EP/Ca@C-1) to 1.22 g-H 2 O/g-sorbent (EP/Ca@C-0.25) with the decreasing carbon content. The carbon-coated sorbent possessed a better structural stability, as shown in Figure S2.…”

“…In order to test the desorption performance of the sorbent under sunlight, the sample was subjected to water vapor sorption for 4 h (20 °C, RH 80%) before being placed on the photothermal experimental setup system (Figure S3), which referred to the previous method. 43 Figure 8a and b shows the temperature rise curve and desorption performance of the sample under 1 kW/ m 2 , respectively. As can be seen, the temperature of the sample was significantly increased, nearly doubling after coating the carbon shell due to the high efficiency in photothermal conversion of the carbon materials.…”

“…For the thermochemical heat storage material, Da et al 55 added the Mn and Fe elements in the form of metal oxides to the calcium-based sorbent, which not only promoted solar absorption but also enhanced the cycling stability. In our previous studies, 43 a carbon-coated CaCl 2 composite sorbent synthesized by tar impregnation and carbonization can be used for direct solar-driven sorption thermal energy storage. The carbon shell not only realized photothermal conversion for in situ heat storage but also prevented solution leakage and improved the structural stability of the sorbent, without affecting the mass transfer in the processes of sorption and desorption.…”

“…However, there is still a problem that salt solution may overflow from the pores when the volume of the solution exceeds the pore volume of the matrixes. Another strategy is to encapsulate the salt hydrates in the shell material such as ethylcellulose, MOFs, SiO 2 , and carbon materials. , The synthetic methods, such as spray drying, wet mixing, and carbon precursor coating followed by carbonation, are utilized to produce the core–shell composite sorbent. It should be noted that the shell thickness should be controlled in this method.…”