Thermal behavior of a combi-storage in a solar-ground source heat pump system for a single-family house

Abstract

Experimental investigations on thermal behavior of a combined solar and ground source heat pump (SGHP) system for a single-family house are presented. The SGHP system was installed at the Lyngby campus of Technical University of Denmark. Detailed experiments were carried out on the system in 2019 under real weather conditions covering domestic hot water (DHW) consumption and space heating (SH) demand. Depending on the contributions of the energy inputs to the combi-storage, five typical daily operation modes are classified. The focus of the investigations is on the dynamic thermal behaviors of the heat storage under different operating conditions. When the combi-storage was primarily heated by solar energy, the inlet stratifier in the storage performed well, ensuring thermal stratification and a good utilization of solar energy. Water temperature in the storage reached up to about 68℃ at the end of the solar heating process. When the combi-storage was primarily heated by the ground heat, the water temperature near the outlet for SH was kept at a temperature range from 26℃ to 31℃ in the heating process to ensure the outlet temperature level of SH, and the water temperature near the outlet for DHW was in the temperature range 47℃∼51℃ in DHW volume. When there was no heat input to the combi-storage, the pre-stored heat can meet the daily heating demand, and the number of days on this mode was up to 9.4% of the total experimental days. The paper gives valuable inputs for researchers and engineers who plan to integrate the combi-storage in a renewable heating system with solar collectors and ground source heat pumps.