An experimental energy performance investigation and economic analysis on a cascade heat pump for high-temperature water in cold region

The need of high-temperature water produced by air source heat pump (ASHP) at cold environment (−20 °C) is of more importance, such as ‘heating by electricity instead of coal (HEIC)’ heating system retrofit in northern China. Thus, a cascade ASHP for high-temperature water (such as 75 °C) at low ambient temperature (−20 °C) is developed. To exam its feasibility and study its energy performance under various hot water temperature, an experiment is carried out within hot water supply temperature from 55 to 75 °C and at ambient temperature as low as −21 °C. The results show that the cascade heat pump has excellent energy efficient at low ambient temperature and high water-supply temperature and proves the thermodynamic feasibility of the unit to supply high-temperature water for residential heating and industry use. In addition, cascade ASHP and other clean hot water technologies are compared from an economic and environmental perspective. The total economic cost of the cascade heat pump is the lowest, while the carbon dioxide cascade heat pumps is higher than gas boiler. In general, the studied heat pump reveals good energy, economic performance and acceptable environmental performance, proving its feasibility.