Numerical study on energy efficiency and economy of a pipe-embedded glass envelope directly utilizing ground-source water for heating in diverse climates

Heat dissipation through glass envelopes accounts for a large proportion of building heating loads in winter. Limiting heat transfer through windows is critical, especially considering the rapid development of glass buildings. A pipe-embedded glass envelope that arranges pipes in the shading device of a double window system is combined with a ground-source heat exchanger (GSHE) for heating in this study. The heat transfer process and energy efficiency of the presented system are simulated in consideration of diverse climatic regions. The results show that the water even much cooler than the room temperature is adequate for auxiliary heating by this system. Water at 12 °C can reduce 30% of the heat flux when the outdoor temperature is 0 °C. In addition, the coefficient of the performance of the piping system exceeds a value of 10 because water temperatures are low. The energy saving rates of the system when applied to Beijing, Shanghai, Guangzhou are 16.8%, 20.2%, and 55.9% during the heating season. In the meantime, capacity of the traditional heating system can be reduced as peak heating loads have been decreased, e.g., a reduction of 40.7% in Shanghai. And the payback period is acceptable in these cities. However, in severely cold regions such as Harbin, the energy efficiency is low because the soil temperature is too low. Overall, the studied heating system is very promising as an energy saving method for glass buildings.