Thermally driven MnCl2NH4Cl resorption cycle for seasonal thermal management of urban buildings

Abstract

The frequency of extreme weather conditions caused by global greenhouse gas emissions has led to a significant increase in energy consumption for refrigeration and heating supply in urban buildings. However, conventional sensible and latent heat storage technologies hold low thermal energy storage density and short-term energy storage capabilities. Additionally, electrically driven compression refrigeration with non-negligible global warming potential (GWP) is unsuited to high ambient temperatures in summer. We propose an advanced strategy, adopting the MnCl₂NH₄Cl resorption cycle to achieve efficient desorption refrigeration of NH₄Cl and resorption heating supply of MnCl₂ under seasonal conditions. Experimental results have demonstrated that our proof-of-concept system can output 70 °C heat with a thermal energy storage density of 166.2 kJ·kg⁻¹, providing continuous heating for 30.5 min under the winter ambient temperature of 10 °C. Moreover, COP_ref remained at 0.589 for continuous indoor refrigeration lasting 58.5 min under summer ambient and refrigeration temperatures of around 30 °C and 2 °C, respectively. This exceptional adaptability to ambient temperatures enables efficient adjustment of urban building comfort. Our work presents a promising zero-carbon pathway for replacing conventional fossil fuels employed in the thermal management of urban buildings with solar energy.