Utilizing shallow geothermal energy to develop an energy efficient HVAC system

Traditionally, shallow geothermal energy is utilized by a ground source heat pump. In fact, the temperature of shallow geothermal energy is typically quite suitable for the cooling/heating of building envelopes and fresh air. To utilize shallow geothermal energy more efficiently, an integrated system is proposed that combines pipe-embedded walls, pipe-embedded windows, and fresh air pre-handling system with the conventional ground source heat pump system. This proposal is based on the temperature comparison among indoor air, envelopes, fresh air and undisturbed soil. A simulation model of the integrated system is developed on the platform of TRNSYS. The free-running temperature and energy consumption of the integrated system applied in an office building in Beijing are investigated. The results show that the free-running temperature of the integrated system is always below 28 degrees C throughout the year, and the non-air conditioning period is extended by 34% compared with the conventional GSHP system. Moreover, the integrated system can greatly reduce the peak load, and the heat pump system capacity can be reduced by as much as 30%. The annual cumulated load for the building is reduced by approximately 43%. Consequently, the energy saving rate is approximately 29% compared with that of the conventional GSHP system. The emission reduction of CO2 is more than 7 kg per square meter. Therefore, the integrated system can fully utilize shallow geothermal energy to build an energy efficient HVAC system. (C) 2019 Elsevier Ltd. All rights reserved.