Energy saving control and operation strategy analysis of thermal coupling system of fuel cell and metal hydride tank

Abstract

The thermal coupling system (TCS), where the heat generated by proton exchange membrane fuel cell (PEMFC) is transferred to the metal hydride (MH) tank, has been investigated extensively and proved beneficial to system compactness as well as capital cost. However, there is a lack of attention to the regulation of hydrogen desorption to increase the efficiency of hydrogen-to-power/heat (ηh−p), especially when the TCS is used in a distributed energy system (DES) combining power and heat. In this study, an energy saving control strategy for a TCS applied in DES is proposed to increase the ηh−p on the premise of the satisfaction of cosine-form hydrogen demand. The threshold temperature is introduced to characterize the maximum of ηh−p, and a prediction framework of threshold temperature for arbitrary signal is proposed based on its functional relationship with five operation parameters and Fourier decomposition method (FDM). The operation strategy of two-tank TCS is also discussed. The results indicate that up to 7.26 × 103 kJ more heat could be utilized by energy saving control strategy compared with the reference case. The relative error of predicted threshold temperature within 0.14% is obtained for a square wave and aperiodic signal, verifying the generalization capability of the proposed framework. Besides, the operation strategy that the rated hydrogen demand is supplied by both MH tanks, is suggested in a two-tank TCS to increase the hydrogen utilization and extend the supply duration.