Thermochemical heat storage (TCHS) system aims to improve the efficiency of vehicles powered by an internal combustion engine, therefore reducing exhaust gas emissions and fuel consumption. On one hand, the engine coolant at engine operating temperature represents heat source, on the other hand it represents heat sink during engine cold start. During engine warm up phase, the released heat from thermochemical heat storage system helps to reach engine operating temperature faster. Thereby high power release of thermochemical system is desirable. In this master thesis, the existing thermochemical heat storage system based on solid gas sorption process, with working pair lithium bromide (LiBr) and methanol (CH3OH), was optimised. A sorbate distribution system, which connects a cartridge (absorber) with a sorbate reservoir, was developed. Performance of the thermochemical heat storage system was investigated according to different pipe diameter and pipe length of the sorbate distribution system. Further, performance of the thermochemical heat storage system was examined according to different ambient temperatures maintained in climate chamber at -10C, 0C, 10C, 20C and 30C. The performance trend was clarified considering the phenomena occurring in the reactive bed, such as heat and mass transfer. Cyclic durability of the developed cartridge was investigated in successively conducted charging-discharging phases. A performance change depending on time was determined. In addition to durability tests, the effect of non-condensable gases on the cartridge performance was clarified. Finally, the reversibility of heat storage process under possible engine conditions was examined. Charging-discharging phases were conducted and charging completeness depending on charging temperatures was investigated.