Studies on the performance characteristics and operating strategies of a thermal storage heat pump system

Abstract

Recently, electricity demand is increasing compared to electric power supply. In particular, the trend is rapidly increasing due to the increase in demand for heating and cooling in summer and winter. Various policies have been published to solve this disparity in supply and demand, but technological methods must be introduced for fundamental solutions. In this study, a new heat pump system is proposed to solve the imbalance between power supply and demand and analyzed the performance. The suggested heat pump system uses a heat storage tank so that heat can be stored at the same time as heating operation, and the power demand is reduced by the energy stored. In order to demonstrate the effectiveness of such a system, analytical or experimental studies are required and it is necessary to derive optimal operating conditions. In this study, the performance change of the system according to time variation was investigated by transient modeling before the experiment. The time duration for thermal storage process and performance of heat storage system were changed according to refrigerant mass flow rate branched by the heat storage tank. Therefore, to analyze the optimal operating condition, the performance analysis was conducted according to the ratio of distributed mass flow rate. Also, the performance characteristics of the system are verified by comparing with the performance of conventional heat pump system. In addition to numerical analysis, the experimental study of the thermal storage system was conducted. Experimental study of thermal storage heat pump has confirmed the performance reduction in the heat storage operation process and the performance improvement in thermal discharge operation process. The overall performance is reduced, but it can be meaningful that it derives the transfer effect of the power load. In the operating condition in which the frost is occurred, it is possible to delay the target time of the defrosting process when using the thermal storage. As a result of this study, it can be expected that the thermal storage heat pump system could reduce the maximum power load and transfer the power load. Although comprehensive performance was decreased compared to conventional heating system, this study was meaningful in that it had additional advantages.