Thermodynamic study of a LiBr–H2O absorption process for solar heat storage with crystallisation of the solution

Abstract

A heat storage process by absorption is studied in this paper. It is devoted to solar domestic systems. Energy and exergy studies are performed on the ideal cycle, and prove the contribution of the solutions crystallisation to the system storage density, with an improvement of 22%. A prototype has been built and tested in conditions compatible with domestic solar thermal collectors. The process has been proved successful for heat storage. The heat charging was more efficient than the discharging phase, with respective heat transferred in the range of 1 to 2 kW and 300 to 500 W, in typical solar domestic conditions. Crystallisation has been observed, and will increase the storage density but discrepancies were found between the ideal solution and the global prototype crystallisation behaviour, possibly due to some impurities presence and a slow dissolution kinetic.

Enhancing the heat storage density of silica–alumina by addition of hygroscopic salts (CaCl2, Ba(OH)2, and LiNO3)

“…Thermal energy can be stored in four ways [7,8]: as sensible [9][10][11], latent [12][13][14][15][16][17], chemical [18][19][20], and sorption heat [21][22][23][24]. It has to be emphasized that the choice of a heat storage method will depend on the thermo-physical properties of the material used.…”

Mathematical model of absorption and hybrid heat pump

“…6. Li-Br solubility in water as a function of the temperature according to various studies [99]. the following graphs.…”

High-Performance Cascade Sorption Thermal Storage Battery for Long-Term Applications in Cold Regions

“…The operating conditions play a significant role in determining the selection of working pairs, driving units, efficiency, and applications of the STB. For instance, the discharging temperature for floor heating is about 30 °C, space heating is in the range 45–60 °C, and domestic hot water in buildings is between 55 and 65 °C. − Furthermore, to meet the rising demand for various temperature levels required by terminal devices, it is suggested that a temperature lift in the range of 60–80 °C is needed, especially for unfavorable ambient working conditions. , Such a temperature lift usually requires a flexible and advanced sorption battery. For water-based working pairs, a double-stage STB is evaluated to reduce the charging temperature requirements from 150 to 95 °C with NaOH/H 2 O.…”