Influence of the water tank size and air source heat pump size on the energy saving potential of the energy storage heating system

Abstract

“Clean heating” has become a national strategy for energy conservation and carbon reduction in China. The energy storage heating system with air source heat pump and water tank has been proven to be energy saving in the previous studies. However, how to determine the sizes of the water storage tank and the air source heat pump based on the building heating load profile has not been investigated comprehensively. In this paper, the model of the energy storage heating system is established on the TRNSYS platform and validated by long-term monitored data. The influence of the water storage tank size and the air source heat pump size on the energy saving potential of the energy storage heating system is investigated comprehensively. The results show that even a small water tank, i.e., 0.06 m3 ~ 0.5 m3, can reduce the start-stop loss of the air source heat pump effectively. When the water tank volume increases to 0.5 m3 and 1 m3, the start-stop loss is reduced from 12.5 % to 0.8 % and 0.2 %, respectively. When the water tank volume increases from 1 m3 to 4m3, the average operating temperature difference of the air source heat pump between the energy storage heating system and the baseline heating system increases from 0.7 to 3.3 °C, and the corresponding energy saving rates caused by the operating temperature difference is approximately 1.0 % ~ 6.3 %. When the ASHP size varies from 80 % to 100 % of the design heating load of the building, the energy saving rates change within 1 %. The ASHP size can be reduced to a certain extent to reduce the investment of the energy storage heating system.