WEB Improved power output of potassium carbonate mixed with deliquescent additives used for thermochemical heat storage.Wednesday (23.09.2020) 16:10 - 16:25 P: Processing and Synthesis 1 Part of:
During the last decade the market share of solar thermal energy generation has been steadily increasing. This is an encouraging trend given over 70% of domestic energy is consumed in form of heat. This development lead to comparable increase in research on thermal energy storage (TES). Thermochemical heat storage based on water vapour sorption by salt hydrates is one of the research topics.
The above mentioned TES is based on the movement of water molecules in and out of the crystal structure of the salt. The energy is stored by driving water out of the system with solar heat and released when the salt hydrates and reincorporates water molecules into its structure. There are several recommended TES materials, such as MgSO4, SrBr2 and K2CO3. Substantial work has been done on their cyclic stability and behaviour in a reactor through salt impregnation in a solid matrix. Contrarily, material’s power output remains somewhat neglected, likely due to the lack of understanding of the (de)hydration processes.
Recent studies indicate that for certain salts, such as K2CO3 , the hydration process could be mediated by a wetting layer formed on the surface of the salt. Further, the reaction speed is dependent on the mobility of this layer which in turn is dependent on the supersaturation ratio or water activity, as stated by classical nucleation theory. The supersaturation can be changed by varying temperature and/or water vapour pressure in the system. In our research we propose changing water activity of the wetting layer by incorporating foreign ions of deliquescent salts. We study impact of those ions on reaction kinetics as well as at the cyclic stability of the salt mixture. Through this study we aim at improving power output of the material and gaining more insight into processes governing phase transitions. Initial tests on K2CO3 mixed with deliquescent salts show enhanced reaction kinetics and promising cyclic stability.