Exergy Analysis as an Assessment Tool of Heat Recovery of Dwelling Ventilation Systems

This paper presents steady-state energy and exergy analyses for dwelling ventilation with and without air-to-air heat recovery, and discusses the relative influence of heat and electricity on the exergy demand by ventilation airflows. Energy and exergy analysis results for De Bilt, NL, are presented in terms of heat and electricity use, on an instantaneous and a daily basis. The amount of electricity input to fans and the heat recovery unit (HRU) is much more significant in terms of exergy than of energy, due to the higher exergy value of electricity. From an exergy viewpoint, it could make sense to use the HRU only when environmental air temperature is low enough to compensate the additional need for electricity. When the air temperature is not too low, electricity input could be decreased by letting ventilation air bypass the HRU or by operating the HRU at low ventilation airflow rate, depending on outdoor temperatures and indoor ccupancy conditions