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With increasing demands on lowering carbon emissions, fuel cell hybrid electric vehicles (FCHEV) have been seen as an alternative to the fossil-fuel driven trucks of today. These would have less emissions and strive to have the same range as any diesel driven transport vehicle. A lot of effort and resources have been put into fuel cell research for incorporation in new powertrains. There are however many different fuel cell types, so the aim of the thesis was to explore two different fuel cell types for use in a FCHEV model.The thesis sets up a model consisting of various subsystems of a high temperature proton exchange membrane fuel cell (HT-PEMFC). Components for the power electronics and a cooling system are also incorporated. The system was then combined with a vehicle model, where a power split between the fuel cell and battery was investigated. The performance of the HT-PEMFC was compared to a low temperature proton exchange membrane fuel cell (LT-PEMFC) on three levels with increasing complexity. These were on a single cell level, stack level and on a vehicle level.The results showed that the HT-PEMFC had worse performance than the LT-PEMFC on both a cell and vehicle level. The power output of an HT-PEMFC was lower for all current densities, meaning more cells were needed in order for the HT-PEMFC to have the same power output as an LT-PEMFC. It did however have a better cooling ability and was a simpler system, which therefore does warrant further investigation on its future use in transport applications. If heat recuperation was investigated further, the HT-PEMFC performance would have been increased to a higher degree than the LT-PEMFC.

The CO2 emissions from road vehicles must be reduced in order to avoid a 1.5 ◦C global warming. To reduce tailpipe emissions, a strong trend is to electrify powertrains to shift away from the use of fossil fuel. Among alternatives, the fuel cellhybrid electric vehicle (FCHEV) is seen as a promising configuration. With the high energy density of hydrogen propulsion systems, it is regarded viable for heavy-dutylong cycle hauling. The aim of this thesis is thus to explore optimal control of energy and thermal management systems of FCHEVs. With the intention of increasing knowledge of how to control FCHEVs for a driving mission, this thesis models an FCHEV powertrain for optimal control purposes. The developed model is used in conjunction with dynamic programming to find the hydrogen optimal control strategies of the energy and thermal management systems. Finally, a sensitivity analysis is performed, investigating how the fuel cell characteristics influence the control strategies. The results propose a feasible complete powertrain model for optimal control purposes and provides insight on how to optimally control the powertrain for various scenarios, minimizing hydrogen consumption. It is concluded that for demanding missions, the fuel cell should consistently provide the main power output and together with the battery handle power transients. For less demanding missions, the fuel cell should be controlled with an on/off strategy, switching between being atidle and working in its most efficient region. It is also concluded that integrated energy and thermal strategies for the fuel cell during a driving mission can increase fuel efficiency, with the optimal thermal strategy being dependent on the fuel cell’s characteristics.