Theses

Predictive energy management has gained interest in automotive research, primarily aimed at optimising power delivery between energy sources, since the introduction of hybrid electric powertrains. As battery electric vehicles and fuel cell hybrid electric vehicles emerge as leading alternatives to internal combustion engines both introduce distinct thermal challenges that have spurred interest in predictive thermal management. However, few studies have explored integrated strategies that jointly optimise propulsion and thermal energy within a unified framework. This thesis investigates integrated predictive thermal and energy management through two case studies focused on fuel cell hybrid electric vehicle and battery electric vehicle applications. A Dynamic Programming framework is used to determine globally optimal control strategies in offline simulations, then adapted to shorter prediction horizons to assess suitability for online application.

The first case study extends the classic hybrid power split problem by applying predictive control to a hydrogen fuel cell bus model in MATLAB, incorporating battery state of charge and fuel cell temperature as system states. The Dynamic Programming controller aims to minimise hydrogen consumption while avoiding thermal violations of +80°C through a multi-objective cost function, achieving an average reduction of 0.25kg/100km in fuel use and 3.57% increase in efficiency over the rules-based benchmark. The second case study applies the framework to an electric vehicle holistic thermal management system model provided by AVL GmbH. Thermal energy is distributed across the cabin, battery, and motor using multi-mode control. The Dynamic Programming controller selects optimal thermal modes and heater power across varying conditions, achieving an average 2.6% efficiency gain and a 15.2km increase in range. However, cost balancing proved challenging, leading to a 1.04°C average reduction in cabin temperature. Applying Dynamic Programming with shorter prediction horizons produced mixed results for both studies, sometimes under-performing compared to the rules-based benchmarks, while introducing irregularities as it attempts to optimise with less foresight.

This research explores the feasibility and limitations of applying Dynamic Programming for integrated predictive thermal and energy management where prior studies have only addressed propulsion and thermal energy separately. The results highlight the practical challenges of implementing thermal models for predictive control and the challenge of balancing trade-offs between efficiency and thermal performance. None the less, the learning gained supports a foundation for future work toward real-time, holistic vehicle control..

Heat exchangers are essential thermal management systems across many industries, from aerospace to high-power electronics. The ambition to decarbonise these industries requires efficient and economically-feasible heat exchanger solutions. Preliminary studies on medium-capacity fuel cell–powered passenger aircraft suggest that heat exchanger designs would require width and height in the order of 1 m (Kozulovic, 2020;Frey et al., 2025), and thus amount to a significant proportion of the aircraft’s frontal area. It is therefore essential, for this and other related industries, that the next generation of compact heat exchangers can deliver the required heat rejection rates —which will necessitate large, intricate heat exchange cores — without incurring unfeasible penalties on fluid pressure drop. This is particularly challenging for gas-to-liquid heat exchangers because the gas-side is not as effective at transferring heat, so large flow rates are often required, leading to significant frictional losses (Kays and London,1998).

Additive manufacturing consists of a range of technologies with great potential to deliver novel and high-performing solutions to problems in a range of engineering disciplines, from structural to biomechanical to thermal. Combined with novel periodic lattice structures derived from the fields of crystallography and topology, promising heat exchanger geometries have been proposed in the scientific literature. In the past decade, these geometries have become increasingly appealing for two key reasons. Firstly, these structures can be readily manipulated using implicit modelling design tools, for which academic and commercial solutions have become widely available. Secondly, their cellular nature makes them easy to manufacture and implement into geometrically-complex design spaces.

Despite the excitement, much remains to be learned regarding the suitability of these geometries for gas-to-liquid heat exchange applications, on which this research focuses. For instance, there is a large amount of lattices based on Triply Periodic Minimal Surfaces available, each with distinct thermal and frictional performance characteristics. The same is true for strut-based lattice geometries. Furthermore, each of these structures can be functionally-manipulated, altering their performance characteristics. As such, engineers and researchers in this field are currently seeking to identify which geometries, topological features and manufacturing methodologies can help deliver the required levels of performance.

The aim of this thesis was to investigate the potential of and provide aerothermal (thermal and frictional) performance for heat exchanger designs based on periodic lattices. The objectives to meet this aim were multifaceted. Firstly, a novel meshing algorithm for minimal surfaces is presented which enables conversion to the standard CAD software format (BRep) early in the design workflow, offering a more traditional approach to CAD — among other benefits — as compared to other available options. Secondly, novel experimental techniques for internal pressure and temperature measurements in lattice structures are described and demonstrated, providing new insight into the flow and heat transfer mechanics within these lattices. Thirdly, experimental data are presented for a range of samples, including different lattice types (Gyroid and Diamond and strut-based lattices), different geometric properties (porosity and hydraulic diameter), different surface roughnesses, and different materials. The results, provided in dimensionless form, add to the limited data available in the literature, especially for this flow regime. Furthermore, recommendations for expediting experimental and simulation-based campaigns are made based on the findings. Much of this research was enabled by an experimental facility designed and commissioned as a part of this project.

The motivation for this project is to support the urgent global climate challenge of preventing a global mean surface temperature (GMST) increase of more than 1.5 °C compared to the preindustrial average (1850–1900). As a carbon-free energy carrier at the point of use, hydrogen (H2) is a promising fuel to decarbonise road freight, shipping, and aviation. However, about 95 % of H2 is currently produced from fossil fuels, which results in significant carbon emissions even when carbon capture is implemented. Previous life cycle assessments (LCAs) of H2 have limited their scope to a subset of production technologies and/or environmental impacts (often global warming potential and acidification potential only). This project aims to fill this gap by producing an LCA of promising H2 supply pathways from raw materials to refilling stations with broad coverage of environmental areas, and scenarios that account for variations in grid electricity mix and the latest and projected technological developments in the H2 field.

Scenarios were developed using information from governmental, industrial, and scientific literature, supplemented by expert elicitation interviews. Sensitivity analysis explored ranges of technological improvements by the years 2035 and 2050. The results show that when the impacts of fuel consumption are included, H2 would have 2.8 to 4.8 times lower global warming potential than conventional fossil-based fuels. However, supplying large quantities of H2 to large transport vehicles would contribute significantly to freshwater ecotoxicity and ozone formation. Sensitivity analysis shows that the following would significantly lower the environmental impacts of H2 supply: 1) electricity powered mostly by renewable energy sources, with minimal use of fossil fuels; 2) a well-developed H2 pipeline infrastructure; 3) a high CO2 capture rate where H2 is produced from methane or bio-methane; 4) minimising the carbon footprint of producing steel, concrete, and solar panels; 5) reducing the environmental impacts of mining for minerals, especially copper and nickel; 6) increasing the circularity of critical materials; and 7) reducing the environmental impacts of processing wastes.

Recommendations are made for future studies, whose findings will be significantly strengthened if issues of commercial sensitivity can be overcome and more primary data can be sourced regarding the manufacture and performance of H2 production plants and critical components of their supply chains.