Effects of the different water tank location on the performance of CO₂ heat pump with thermal energy storage for space heating

The widespread adoption of air source heat pumps (ASHP) in energy-saving building projects can be attributed to their mature technology, high efficiency, and environmentally friendly characteristics. However, the impact of various locations of water storage tanks on the performance of ASHP utilizing CO₂ as the working fluid for space heating is rarely reported in in existing literature. Therefore, this study aims to investigate the heating characteristics of three CO₂ ASHP systems with varying water tank locations using TRNSYS software. The heating performance of these systems are evaluated based on key parameters such as coefficient of performance (COP), energy consumption, economic viability, and emissions including CO₂, SO₂ and dust etc. The findings reveal that system A exhibits the highest annual average COP at 2.87, followed by system C at 2.61 and system B at 2.46. Furthermore, in terms of total cost over the entire heating period, system A demonstrates a significant advantage with a value of 3334.2 CNY which is 56.9 % lower than system B and 24 % lower than system C respectively.