Energy pile-based ground source heat pump system with seasonal solar energy storage

Decarbonization of the building sector represents a huge potential to reduce greenhouse gas emissions. An energy pile-based ground source heat pump system coupled with seasonal solar energy storage was proposed and tailored for high-rise residential buildings to satisfy their heating/cooling demands. An optimal design procedure was developed for the coupled system accounting for the constraints of limiting the temperature changes of the energy pile and avoiding the cold build-up in the ground. The system performance under different ground conditions and heating-dominated climatic conditions across China was evaluated numerically. The results showed that within a typical year of operation the system evolved through three stages, the initial stage of rapid heat injection into the ground, the following developed stage with slower or no heat injection, and the final stage of heat extraction for space heating. The system could well meet the heating demands of buildings in the cold zone with the solar collector efficiency ranging from about 40% to 58%. For cases in the severely cold zone, favourable ground conditions were critical for the system to cover the heating demands. In addition, integrating domestic hot water preheating into the system could improve its performance, especially for cases in unfavourable ground conditions.