Integration of a heat exchanger on the supply air with the ground-source heat pump in a passive house – case study

A ground-source heat pump (GSHP) system designed to cooperate with a low temperature heating system and hot water production was installed in a new passive house nearby the city of Poznan (Poland). The paper describes an integration of the GSHP system with a heat exchanger on the supply airflow in order to recover the waste heat from outside (fresh) ventilation air and store it in the ground during summer, as well as to heat the supply air in winter what prevents the recuperator from freezing. Analytical calculations to evaluate the energy, economy and environmental benefits of supplying the low heat reservoir with heat from fresh air were made. Chilled supply air compensates the heat gains from building and is exhausted, simultaneously overcoming a part of the cooling loads by using mechanical ventilation system. Heat taken in the heat exchanger by the glycol mixture is used in the evaporator of the heat pump, which produces hot water with increased energy efficiency – increased coefficient of performance (COP). After that glycol mixture is supplied to the ground. In the case of stagnation of the heat pump, glycol mixture exiting the heat exchanger is directed to the ground, where part of the delivered waste heat is stored. The results of calculation experiment indicated that heat recovered from the supply ventilation air during summer is increasing the Seasonal Performance Factor (SPF) of the heating system in winter, consequently significant energy savings can be achieved, what is a part of the idea of the Sustainable Development. Based on the simulations it has also been demonstrated that the proposed technical solution has a high application potential for micro and macro scale installations using GSHP.