Global energy demand has seen a significant increase over the past 70 years, accelerating greenhouse gas emissions by placing excessive pressure on existing non-renewable energy sources. As wind and solar power are projected to account for a significant share of future electricity production, their intermittent nature introduces a major challenge to grid stability. Green hydrogen offers a promising solution as it can be produced during periods of excess electricity supply and combusted in land-based gas turbines during high electricity demand, thereby stabilizing any oscillations. Combustion of hydrogen is, however, not problem-free. The main challenge is its high flame speed, which can lead to flashback, an undesirable upstream flame propagation that can cause damage to the combustor hardware. Because conventional land-based gas burners are not designed for pure hydrogen combustion, new burner designs must be developed and tested. An example of such a burner is the FlameSheet™ burner, whose geometrical simplification, called a 2-D trapped-vortex burner, is investigated in the present experimental study.

The structure of this study can be divided into two parts. The first part investigates the flashback behavior of the 2-D trapped-vortex burner for a range of equivalence ratios, hydrogen volume fractions, and unburned mixture temperatures. The results show increased flashback propensity with all three parameters, although the Reynolds number at flashback seems to be invariant with the last. The second part examines temperature profiles within the 2-D trapped-vortex burner, with a particular emphasis on their dependence on the Reynolds numbers, unburned mixture temperatures, and adiabatic flame temperatures. The thermocouple measurements reveal that the temperature profiles shift toward lower values with increasing Reynolds numbers and higher values with increasing adiabatic flame temperatures. To complement these findings, a one-dimensional heat transfer model is developed, which not only predicts the vertical temperature profiles in the remaining components but also identifies convection and conduction through the liner as the dominant and limiting heat transfer mechanisms.

To comply with the Paris Agreement, the Dutch government has launched an energy transition process, with the goal of replacing coal and natural gas-based electricity with renewable sources. The intermittent nature of renewable electricity necessitates the installation of an energy storage system to balance supply and demand. Hydrogen is a potential energy storage and transport medium. However, its production is currently more expensive than natural gas, and storage and transport are energy-intensive due to its low density. Because the infrastructure necessary for the hydrogen supply chain necessitates significant capital investments, a techno-economic analysis of various techniques of hydrogen production, compression, storage, and transport is required.
The aim of this thesis was to evaluate the levelized costs of hydrogen at various phases of supply chain, from hydrogen production to utilization. In order to accomplish this task, a literature review was conducted to identify the most promising methods in hydrogen production, compression, storage and transport followed by developing mathematical models of various technologies. According to the literature review, water electrolysis using electrolyzers such as alkaline, polymer electrolyte membrane (PEM), and solid oxide was shown to be techno-economically feasible. The literature review also revealed that centrifugal and diaphragm compression, pipeline transmission, and salt cavern storage were all techno-economically feasible technologies. These technologies’ steady-state mathematical models were built for scaling and techno-economic analysis. In the end, learning curves were applied for electrolyzers to predict the cost reductions in future.
According to the results of mathematical modeling, hydrogen production contributes the most to total levelized costs of supply chain followed by overall compression costs. Moreover, capital costs of electrolyzer stack and electricity costs significantly influence the levelized costs of hydrogen production. For 1 MW electrolyzer capacity and average capital and operating costs of electrolyzer stack, alkaline electrolysis is currently the most cost-effective technique of producing hydrogen with levelized cost of hydrogen (LCOH) calculated to be 3.69 €/ kg, followed by solid oxide electrolysis (4.55 €/kg).However, the use of learning curves indicates that by 2050, solid oxide electrolysis may be the most cost-effective technique of producing hydrogen with projected levelized cost of 1.72 €/kg. The pipeline compression costs were found to be around 0.065 €/ kg whereas diaphragm compression costs were found to be in the range of 0.55 to 1.2 €/ kg depending on the outlet pressure. While hydrogen storage and transportation require substantial capital investment, their overall impact on levelized costs was found to be minimal compared to production and compression expenses, with storage costs averaging around 0.8 €/kg and transportation costs at approximately 0.0007 €/kg per kilometer. The same mathematical model was used to analyze two hydrogen utilization scenarios: fuel for fuel cell vehicles and feed for industry. Both pessimistic and optimistic cases were examined by varying cost-influencing parameters to predict the possible range of total levelized costs for the supply chain. The results showed that hydrogen as a fuel for fuel cell vehicles will stay more expensive than hydrogen as a feed for industry.

In order to reduce greenhouse gas (GHG) emissions, fleets of medium- and heavy-duty vehicles are transitioning from conventional fossil fuels to fully electric drivetrains. To utilize these medium- and heavy-duty electric vehicles (MHDEVs) without significantly disrupting their operations, Megawatt Charging Systems (MCS) are being developed, which enable charging rates up to 4.5 MW. However, these charging rates are associated with substantial heat generation in the vehicle’s battery pack. To regulate the battery temperature and maximize battery lifetime, performance, and safety, the development of a battery thermal management system (BTMS) for this application is crucial.

The study provides a methodology that adopted a system engineering approach for the design of a BTMS for the application of MHDEVs which utilize MCS. The study defined the requirements for the BTMS which include the optimal temperature range for battery cells and determined the battery heat generation rate when using MCS. Furthermore, the study investigated the magnitude of temperature gradients in battery cells as a result of MCS.
Subsequently, two assessment stages have been proposed to assess BTMS strategies, which include forced air BTMS, immersion cooling BTMS, cooling plates with coolant BTMS, and cooling plates with refrigerant BTMS. This assessment resulted in design requirements for heat transfer areas and mass flow rates to maintain the battery cells below 35 ℃. Moreover, the concepts of utilizing cooling plates with refrigerant in a vapor-compression refrigeration system and storing charging session heat by thermal energy storage (TES) have been developed. This included the dimensioning of a condenser and compressor for the vapor-compression refrigeration cycle and included the dimensioning of the required mass and volume of TES medium for the TES system. The study found that these two BTMS strategies are the most favorable. Thermal energy storage with hydrated salt as phase change material (PCM) appeared as the most effective and feasible option subsequent to conducting comparisons with immersion coolant and paraffin PCM. However, a BTMS with a vapor compression refrigeration system might be needed when the BTMS is used for both driving and charging. Analysis of refrigerants R717, R134a, and R1234yf, indicated that R717 is the most effective in this BTMS with a COP of 3.52 and a lower required mass flow rate and compressor power consumption, however, is associated with several safety considerations that must be addressed when selecting R717 over other refrigerants. Lastly, the study utilized a MATLAB Simulink model to identify the effects of dynamic phenomena that occur during operation of the BTMS and the study determined the impact of BTMS weight on MHDEV driving range.

Recommendations for future research are given related to the need for increased fidelity of heat generation prediction and BTMS models. Furthermore, future research should be conducted on combining the BTMS with other thermal management systems in the vehicle to maximize overall effectiveness.