Energy, environmental and economic performance evaluation of energy pile system under different climate conditions

Energy pile is an innovative geothermal heat exchanger (GHE) in ground source heat pump (GSHP) system, which integrates GHE pipe into concrete pile, and therefore, provides a green solution for indoor air conditioning with fossil fuel consumption substituted by geothermal energy. In the study, we propose a sustainability analysis framework for energy pile system to holistically evaluate the energy-saving potential as well as economic and environmental benefits of energy pile system by integrating the whole building energy modeling software OpenStudio V2.8.0 and energy pile design software GLHEPro V5.0, fully considering components of the energy pile, heat pump, and building. A comparison study is conducted based on a U.S. DOE benchmark high-rise apartment with baseline heating, ventilation, and air conditioning (HVAC) system, district heating and cooling system, and energy pile system across seven climate zones in China. The results reveal the energy-saving benefits of an energy pile system are highly dependent on climate zones, ranging from 19% to 45%, which correspond to 21-40% utility cost-saving, and 25-36% CO2 emission reduction. Among the seven climate zones in China, the severe cold zones I, VI, and VII benefit the most by applying energy pile systems, while the mild zone V benefits the least in all energy, environmental and economic aspects. The cold zone II and hot-summer cold-winter region III are most favorable to apply energy pile systems because no performance degradation is predicted over years. The hot-summer and warm-winter zone IV is also suitable for energy pile systems, but the payback period is reasonably longer.

Automated summary

Energy pile system is an innovative geothermal heat exchanger that provides a green solution for indoor air conditioning. Its energy-saving benefits and economic and environmental advantages vary across different climate zones.