Abstract
A promising alternative to fossil-fuelled vehicles are battery-powered vehicles and fuel cell (FC) vehicles. The major differences between fuel cell and battery-powered vehicles are the range and refuelling times of each vehicle type. With a hydrogen (Hed vehicles are the range and refuelling times of each vehicle type. With a hydrogen (H2) fuelling time of approx. 5 minutes it is possible to cover a distance of up to 800 km with a fuel cell vehicle. These properties make a fuel cell vehicle comparable to a fossil fuel powered vehicle. Furthermore, due to short fuelling times and long range capabilities, fuel cell vehicles are more suitable for long-distance, trucking and agriculture than battery-powered vehicles. The aim of current research is to increase the profitability of fuel cells by reducing costs and improving performance. To ensure a high performance of the fuel cell stack, more hydrogen is supplied to the stack than is needed for the reaction. Therefore, unused hydrogen is pumped back to the anode inlet of the FC-stack using a jet pump or a recirculation blower. In this study, the application of an electrochemical compressor or hydrogen pump (HP) for hydrogen recirculation is suggested. The hydrogen pump is an innovative H2 transport technology with the additional functions of compression and purification in the recirculation system. Hydrogen pumps are very efficient compared to mechanical compressors due to the almost isothermal conditions they operate under. Furthermore, due to the modular design, hydrogen compressors can utilize a minimal amount of space in vehicles.
Highlights
1.1 Short Description of the Necessity for RecirculationIn the operation of a fuel cell hydrogen is typically supplied in excess to prevent local hydrogen starvation on the membrane electrode assembly (MEA) and to increase the life of the fuel cell
1.2 Replacement of the Blower by a Hydrogen Pump This study proposes a new option for recirculating hydrogen in a fuel cell system in the form of an electrochemical compressor
Through the use of a hydrogen pump, the efficiency of the fuel cell (FC) system could be further improved by ~2,8 % and the tank to wheel efficiency could be improved by ~2 %
Summary
1.1 Short Description of the Necessity for RecirculationIn the operation of a fuel cell hydrogen is typically supplied in excess to prevent local hydrogen starvation on the membrane electrode assembly (MEA) and to increase the life of the fuel cell. With the use of a passive jet pump, an active recirculation blower, or a combination of both, the unused hydrogen is pumped back to the anode inlet and combined with fresh hydrogen from the tank (Fig.). Due to the diffusion and permeation through the membrane, a parasitic exchange of gases takes place (Fig.). Nitrogen permeation through the membrane is responsible for a concentration of inert gases on the anode side and prevents a uniform reaction from occurring. A less uniform reaction due to the presence of nitrogen inherently causes a decrease in FC performance. For this reason, the anode gas is released at regular intervals with a purge-valve to remove the nitrogen from the system (Fig.). Purging causes the loss of hydrogen, lowering the efficiency of the system
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