Heating Performance Analysis of an Integrated Solar-CO₂ Heat Pump System with Thermal Storage Tank

The integrated solar-CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> heat pump thermal storage water tank system substantially reduces heating energy consumption and dependence on fossil fuels by synergizing solar energy with CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> cycle technology. This promotes building decarbonization, enhances clean energy efficiency, and mitigates carbon emissions. In this study, the system's thermal performance was experimentally optimized to maximize heating capacity and utilization of solar/ambient energy. The experimental results demonstrated that when the daily solar irradiation increased from 5.13 to 21.15 MJ/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, the daily useful heat gain escalated by 263.92%, while the daily collector efficiency decreased by 10.42%. As the initial temperature of the thermal storage tank rose from 10.34°C to 29.88°C, the daily useful heat gain diminished by 19.52% with a 17.77% reduction in the daily collector efficiency, indicating that a lower initial tank temperature enhanced the daily collector efficiency. Compared with the electric heating system, the CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> heat pump achieved an energy saving rate more than 10 times higher under high-temperature setting conditions, with the best operating parameter for the heat pump being an initial pressure of 6 MPa. This study elucidated the effect of multi-energy collaboration on clean heating performance.