Air mass flow and pressure optimisation of a PEM fuel cell range extender system. (30th October 2020)

• Record Type: Journal Article
• Authors: Hoeflinger, Johannes; Hofmann, Peter
• Is Part Of: International journal of hydrogen energy. Volume 45:Number 53(2020)
• Page Start: 29246
• Page End: 29258
• Publication Date: 2020-10-30
• Subjects: Hydrogen PEM fuel cell -- Range extender -- Air supply system -- Fuel cell model -- Fuel cell operating parameter influences -- Fuel cell air compressor; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2020.07.176
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: In order to eliminate the local CO2 emissions from vehicles and to combat the associated climate change, the classic internal combustion engine can be replaced by an electric motor. The two most advantageous variants for the necessary electrical energy storage in the vehicle are currently the purely electrochemical storage in batteries and the chemical storage in hydrogen with subsequent conversion into electrical energy by means of a fuel cell stack. The two variants can also be combined in a battery electric vehicle with a fuel cell range extender, so that the vehicle can be refuelled either purely electrically or using hydrogen. The air compressor, a key component of a PEM fuel cell system, can be operated at different air excess and pressure ratios, which influence the stack as well as the system efficiency. To asses the steady state behaviour of a PEM fuel cell range extender system, a system test bench utilising a commercially available 30 kW stack (96 cells, 409 cm 2 cell area) was developed. The influences of the operating parameters (air excess ratio 1.3 to 1.7, stack temperature 20 °C–60 °C, air compressor pressure ratio up to 1.67, load point 122 mA/cm 2 to 978 mA/cm 2 ) on the fuel cell stack voltage level (constant ambient relative humidity of 45%) and the corresponding system efficiency were measured by utilising current, voltage, mass flow, temperature and pressure sensors. A fuel cell stack model was presented, which correlates closely with the experimental data (0.861% relative error). The air supply components were modelled utilising a surface fit. Subsequently, the system efficiency of the validated model was optimised by varying the air mass flow and air pressure. It is shown that higher air pressures and lower air excess ratios increase the system efficiency at high loads. The maximum achieved system efficiency is 55.21% at the lowest continuous load point and 43.74% at the highest continuous load point. Future work can utilise the test bench or the validated model for component design studies to further improve the system efficiency. Graphical abstract: Image 1 Highlights: At high loads, the system efficiency is higher at high air pressure and low mass flow. At low loads, the system efficiency is higher at low air pressure and high mass flow. Maximum system efficiency is 55.21% at the lowest continuous load point. Maximum system efficiency is 43.74% at the highest continuous load point.