An evaluation of different fuel cell hybrid electric vehicle (FCHEV) powertrain designs—such as fuel cell/supercapacitor (FC/SC), fuel cell/battery (FC/B), and a combination of supercapacitors and batteries (FC/SC/B)—and different control strategies by researchers in Belgium concluded that the FC/SC HEV has slightly higher fuel economy than the FC/B HEV and FC/B/SC HEV powertrains.
This, the researchers suggested in a paper presented at the recent EVS 27 conference in Barcelona, was due to the use of the efficient supercapacitors for the majority of the transient-power requirements (the SC can be charged or discharged at a high current, at which the battery cannot function). The fuel economy of the supercapacitor fuel cell hybrid, they noted, is higher despite the vehicle being heavier and more expensive.
They also pointed out that the combination of supercapacitors and batteries (FC/B/SC HEV) may provide a good solution for FCHEVs from the point of view of battery lifespan, component sizing and transient periods.
A stand-alone FC [fuel cell] system integrated into an automotive powertrain is not always sufficient to satisfy the load demands of a vehicle. Although FC systems exhibit good power capability during steady-state operation, the response of fuel cells during transient and instantaneous peak power demands is relatively poor. Consequently, the high cost and slow dynamics of the FC systems are the major challenges for the commercialization of fuel cell electric vehicles (FCEVs).
To overcome these challenges, the FC system should be hybridized with single or multiple energy storage systems (ESS) (such as battery and supercapacitor) to meet the total power demand of a hybrid electric vehicle (HEV) and to improve the efficiency.
… The main objective of this paper is to give an evaluation study of different FCHEV powertrains from the point of view of the fuel economy, cost and powertrain component sizing.—Hegazy et al.
In the study, they designed and simulated the different fuel cell hybrid powertrains using Matlab/Simulink; two standard driving cycles (NEDC and FTP75) were used to evaluate the fuel consumption.Further, two control strategies based on the knowledge of the fuel cell efficiency map were implemented to minimize the hydrogen consumption of the FCHEV powertrains.
These control strategies were (1) a control strategy based on the Efficiency Map (CSEM); and (2) and control strategy based on Particle Swarm Optimization (CSPSO). CSEM is applied to minimize the hydrogen consumption for each driving cycle. CSPO instantaneously distributes the power between the multiple sources with the aim to minimize the hydrogen consumption while maintaining the SoC of the ESS over the driving cycle.
|Comparison of the improvement in hydrogen fuel economy between the FCHEV powertrains over different driving cycles. Left: CSEM. Right: CSPSO. Click to enlarge.
Omar Hegazy, Joeri Van Mierlo, Philippe Lataire, Thierry Coosemans, Jelle Smenkens, Mohamed Abdel Monem, Noshin Omar, and Peter Van den Bossche (2013) “An Evaluation Study of Current and Future Fuel Cell Hybrid Electric Vehicles Powertrains.” (EVS27-8920681)