Comparative analysis of cascade and single heat pumps for cooling and hot water supply performance: Experiments and building simulation

This study presents a comparative analysis of cascade and single heat pump systems for simultaneous cooling and domestic hot water supply, aimed at supporting building electrification and carbon neutrality goals. The novelty of this work lies in its integrated experimental and simulation-based evaluation of cascade heat pump performance, addressing a gap in existing studies that typically analyze either mode separately. A field test was conducted in a real building environment using two configurations: a cascade heat pump system managing both cooling and hot water functions, and two separate single heat pumps. Performance metrics such as cooling energy efficiency ratio and hot water coefficient of performance were measured and compared under identical boundary conditions. In addition, a transient simulation study was carried out using transient simulation tool for representative summer days in office and residential buildings, assessing primary energy consumption and carbon emissions based on experimental data. The cascade system achieved up to 15.3% improvement in energy efficiency ratio, 23.7% reduction in primary energy use for office buildings, and up to 24% reduction in CO2 emissions. These findings demonstrate the practical applicability of cascade heat pumps in energy-saving retrofit projects, especially for space-constrained buildings, and provide empirical and simulation-based evidence supporting their integration into sustainable building strategies.