Design and analysis of a hybrid space heating system based on HT-PEM fuel cell and an air source heat pump with a novel heat recovery strategy

This work analyzes the performance of a system integrating high temperature proton exchange membrane fuel cell (HT-PEMFC) and air source heat pump (ASHP) technologies for residential space heating. The main goal is to improve energy conversion efficiency for a residential building in the Canadian climate, in which methane is normally used to feed traditional systems (e.g., boilers and/or furnaces), due to its considerable local availability. On the other hand, ASHP technology is characterized by high efficiency, but normally fails to perform well in cold climates, due to the reduction of the coefficient of performance (COP) and ice formation on the evaporator. Due to the higher attention paid to low temperature PEMFC system (LT-PEMFCS) till now, it is here investigated if significant improvements can be obtained with a higher temperature PEMFCS, by thus fully exploiting the higher quantity and better quality of recoverable waste heat compared to LT-PEMFCSs, particularly aiming at mitigating the afore-mentioned low-temperature related issues. A mathematical model for the system components is proposed to perform parametric analyses aimed at assessing the variation of efficiency as a function of both environmental and load conditions. The results show that the ASHP COP increases by more than 77% when the HT-PEMFCS works at its nominal (5.3 kW) power and/or inlet air has a high relative humidity (RH), i.e., close to 100%. The proposed HT-PEMFC system configuration was able to reach a total COP higher than 1.5, leading to a reduction of the needed primary energy needed and a consequent reduction of the operating costs by up to 60% compared to boilers.