Analysis of temperature behavior and prediction model for underground permeable blocks rainwater tank source heat pump system through long-term operation

Permeable blocks rainwater tank (RW tank) source heat pump system (RWHP system) can contribute to the development of an eco-friendly energy system. Therefore, this study evaluated the temperature behavior of the RW tank through the testbed operation performance analysis of RWHP system. Additionally, in order to develop a model that predicts the temperature of the RW tank, four models (Bagging, Boosting, Long short-term memory, Gated recurrent unit) were reviewed based on measured testbed data. As a result, it was confirmed that the temperature of the RW tank is affected by factors such as ambient temperature, heat pump outlet fluid temperature, the heat exchange amount of the heat pump, RW tank water level, and system operating mode. Among the four predictive models that predict the temperature of the RW tank using these variables as input values, the bagging model showed the highest predictive performance. The bagging model showed very good predictive performance, with a MAE of 0.38 degrees C, an R2 of 0.9940 in training and a MAE of 1.06 degrees C, R2 of 0.9672 in testing. This study demonstrated the feasibility of predicting RW tank temperatures using real-time field data. The proposed RW tank temperature prediction model is expected to be incorporated into energy simulation tools such as TRNSYS or LCEM, contributing to performance prediction and improvement studies of RWHP systems. This approach allows for the quantitative assessment of the development value of RWHP systems and will be used to review optimal design strategies and operating manuals for RWHP systems.