Energy efficiency and economic performance of a low-temperature heating system combining double-layer pipe-embedded wall and ground source heat pump

Reducing heating energy consumption in buildings is a crucial step towards a low-carbon future. The energy efficiency of heat pump heating systems can be improved by reducing the water supply temperature of terminals. However, existing terminals are limited in using lower-temperature hot water and leaves potential for energy savings. Therefore, this study proposes a double-layer pipe-embedded wall heating system coupled to a ground source heat pump. The outer pipes use shallow geothermal energy to reduce envelope load, whereas the inner pipes use water produced by the heat pump to provide heating. Energy, economic, and carbon emission analysis models of the proposed system are developed. A residential heating case study is conducted in Harbin, Shenyang, Beijing, Zhengzhou, and Shanghai to investigate the performance of the proposed system. The results show that the proposed system achieves much lower-temperature heating than the reference floor heating system. The seasonal energy savings of the proposed system in the selected cities are 12%-18%, with a SCOP of 4.0-5.8. The dynamic payback period of the proposed system is 1.6-4.3 years and the CO2 emission intensity is reduced by 1.2-3.2 kg/m2. This study provides an insight into the application of double-layer pipe-embedded wall heating systems.