Abstract
This paper presents an innovative turbocharged proton-exchange membrane fuel cell system (TC-PEMFC) fuelled by hydrogen. Their high efficiency and absence of pollutant emissions allowed interest in hydrogen-powered PEMFCs to grow constantly over the past few decades. Nowadays, both industry and academia consider PEMFCs as one of the most promising solutions to replace conventional fossil fuel plants and achieve decarbonization of the energy and transportation sectors.
The system proposed in this study further improves the performance of standalone PEMFCs (generally within the 60–40% range), using the pressurization of the fuel cells. Two separate stacks are operated in parallel and integrated with a turbocharger, which pressurizes the cathode air flows. Before being discharged into the ambient, the PEMFC outlet flow expands in the turbine, providing part of the mechanical power absorbed by the compressor and increasing the net power output of the plant. The remaining part is supplied by an electrical motor connected to the shaft of the turbocharger.
To guarantee the proper operation of the PEMFCs in terms of mass flows, pressures, temperatures, chemical compositions and humidity, the layout incorporates many auxiliary components. They include a polymeric membrane cross-flow humidifier on the cathode side, a gas-to-gas heat exchanger on the air loop, a side channel blower on the anode recirculation and a liquid cooling system for the stacks.
A dedicated control system was designed to keep all the operative parameters of the plant on the proper values. A proportional-integral-derivative controller and a set of look-up tables regulate the opening of fuel and bypass valves, as well as the rotational speed of turbocharger, cooling fluid pump and blower.
To fully understand the potential of this innovative solution, Rolls-Royce Solutions and Thermochemical Power Group (University of Genoa) developed a simulation model using GT-Power, a commercial software by Gamma Technologies Inc. The complete layout of the system was recreated within GT-Power relying on its extensive library of components. This is the first time a turbocharged PEMFC system was modelized including all the main balance of plant components and implementing the full control logics.
The model was used to simulate the TC-PEMFC system under different conditions, to monitor its operative parameters, and to compare its performance with a standalone PEMFC. The promising results obtained during this analysis confirm the potential of the turbocharged layout and open the way for even more sophisticated simulation studies and experimental activities.
