Development of a control strategy for air handling units equipped with membrane-based enthalpy exchangers

With rising air tightness in buildings, the use of mechanical ventilation has become more relevant. In this context, energy recovery offers a significant contribution to the decarbonisation of building operations. Membrane-based enthalpy exchangers (MEEs) recovering sensible and latent heat can significantly reduce the energy demand for air conditioning. In moderate climates, the outdoor air provides sufficient humidity load in transitional periods. Hence, MEEs have to be bypassed to avoid high indoor air humidity. For this reason, an efficient control strategy for the operation of MEEs is needed to avoid energy waste or comfort violations. Typical control strategies in application use outdoor air temperature only. In this paper, we present a new control strategy for a MEE’s bypass. We test the control strategy with a dynamic simulation model and analyse the control strategy’s impact on the building’s energy demand and indoor air comfort conditions. Therefore, we compare different control strategies for the bypass over the MEE. For warm and humid climates (Miami), the results show that the newly developed control strategy can reduce the energy demand by 11 % compared to a simple outdoor air temperature control. For moderate climates (Cuxhaven, Germany), the energy-saving potential still is about 2 %.