To combat climate change, industries across the board must transition to renewable practices and reduce their reliance on fossil-derived resources. The beer brewing industry, in particular, faces a significant challenge as it depends heavily on food-grade CO₂, which is typically produced through the combustion of fossil fuels. However, biogenic CO₂ is generated naturally during the fermentation step of the brewing process, presenting a renewable alternative source. Whilst large-scale breweries have successfully adopted systems to capture and upgrade this biogenic CO₂ to food-grade standards, these technologies remain economically unfeasible for smaller craft breweries that typically produce fewer than 10,000 hectoliters of beer annually. As a result, many craft brewers continue to rely on CO₂ suppliers who source their product from fossil fuels, maintaining their dependence on non-renewable resources. Furthermore, they stay dependent on the CO₂ market, in which CO₂ might become a more expensive resource.
This thesis focuses on the design and economic evaluation of a novel, cost-effective fermentation gas purification system specifically for small-scale craft breweries. The process includes identifying the necessary separation steps based on the composition of fermentation gas, determined through a literature review, alongside an analysis of regulatory requirements defining the food-grade CO₂ standard. Suitable technologies are selected based on their operational ranges and effectiveness for the required separations. These technologies are then ordered and designed in the appropriate sequence. The design process yields critical outputs such as equipment sizing, operational conditions, and energy requirements. These parameters serve as inputs for an economic analysis, which estimates the capital and operational expenditures of the system. This analysis is subsequently used to assess the economic viability and overall cost-effectiveness of the proposed solution.
The results contribute to bridging the technological gap, offering small-scale breweries a sustainable pathway to independently produce food-grade CO₂, reducing their reliance on external suppliers and associated emissions. By adopting this system, the craft beer industry can take a significant step toward achieving carbon neutrality.

The severe rise in global surface temperature and its associated damages to the ecosystem are primarily attributed to anthropogenic carbon dioxide emissions. The present CO2 levels in the air today and the continuing emissions necessitate even the most ambitious development scenarios to rely on net negative CO2 emissions to limit the global temperature rise to 1.5 °C until the year 2100. Direct Air Capture (DAC) refers to the direct extraction of carbon dioxide from the ambient air and addresses the need for net negative emissions. As the technology is still in its infancy, understanding and modeling the occurring processes is crucial.
This thesis addresses the challenges in modeling adsorption and desorption processes in solid-sorbent Direct Air Capture, focusing on the complexities introduced by the porous structures of sorbent materials and the effects of humidity. Current models fail to incorporate the full spectrum of mass transfer processes, or do not consider the significant effects of humidity on the process. To bridge this gap, a detailed mass transfer and reaction kinetics model at the particle scale was developed, aiming to provide a more accurate framework for predicting the performance of amine-functionalized sorbents in DAC applications. The model was developed on a particle scale, and subsequently included in contactor models of a packed-bed and a monolith. The study considered all relevant transport mechanisms, finding that pore diffusion and reaction kinetics are critical in governing sorbent uptake dynamics. The contactor model effectively compares the performance of packed-bed and monolith reactors, highlighting a tradeoff between productivity and energy efficiency, with significant potentials for energy savings offered by the monolith.

The world is witnessing unprecedented climate changes, which have worsened over the past couple of years. Despite significant progress in renewable energy, achieving a reduction of global warming remains challenging. Renewable energy sources like solar, wind, and hydroelectric technologies offer promising solutions, but challenges persist due to their intermittency and geographical dependency. Green hydrogen, generated through electrolysis using renewable energy, has come up as a solution for storing electric energy and providing a constant energy supply.

Alkaline water electrolysis has emerged as one of the most promising electrolysis methods due to its large-scale operation, long durability and low costs. This does not come without challenges, one of them being leakage currents, which reduces the efficiency of the electrolyser. Leakage currents occur when not all current is used for hydrogen production, but some of it leaks into, for example, the produced hydrogen stream. To reduce these leakage currents, more research into the origins is needed. The first step is modelling the electrolysis while considering as much as possible of the physics happening inside the system. Current models of alkaline water electrolysers are either modelled using only mathematical equations or neglect the operating parameters, which makes the results highly variable per system. Other models do use analytical methods with experimental results, but these models only comprise one electrolysis cell rather than a full stack.

This work consists of developing two three-dimensional models, validating them using experiments, and using them to predict the effect of changes in geometry. The first model was made using COMSOL Multiphysics software and used to research the water electrolysis stack, which comprised one or eight cells using electrochemical relations and physical data. It was found that a model could be made that fitted the experiments within the error margin of the experiments (<2.5%). It lacked flexibility but overall showed good results for an electrolyser stack of one or eight cells. The second model was made using an equivalent electrical circuit (EEC) of the electrolyser in Python via the PySpice module. A steady-state model, including the leakage currents, could be developed by calculating all system resistances, namely the cell, inlet/outlet, and manifold resistances. This model overestimated the performance of the electrolyser by 10-15% for low current densities and 2-4% for high current densities. Nevertheless, it was highly adaptable for different scenarios, making it valuable for research into optimising the electrolysis stack. Both models were used to predict the effect of changes in geometry; the effect of the length of the inlets, and the number of cells. This showed that the EEC model was better suited for this research.

In recent times, soft matter has gained significant interest among researchers in the fields of biomechanics and biomedicine, especially in areas like soft robotics and biopolymers, due to its remarkable ability to undergo substantial deformations. Soft robotics often requires materials that can flexibly adapt to or mimic the movements of living organisms, requiring properties of flexibility and easy deformability. Biopolymers, naturally occurring in the human body, such as within brain tissue or blood clots, have gained attention due to their tendency to exhibit extensive deformation even under minimal loads. Consequently, there has been a growing emphasis on investigating stress-strain responses associated with these materials in recent years. This research particularly centers on a specific deformation phenomenon known as the Poynting effect.

The Poynting effect is related to the transverse stress or strain response when subjected to simple shear, revealing that the application of simple shear strain does not solely result in simple shear stress. This intriguing phenomenon captures our attention, primarily because it challenges intuitive expectations.

Within the scope of this thesis, we employ two distinct deformation gradient tensors to analyze stress-strain responses under two separate boundary conditions: constant gap and constant normal stress boundary conditions. We also introduce a methodology for predicting the sign of the Poynting effect under conditions of small yet finite strain. Finally, we validate our analysis through simulation experiments.

We have modified Meng's original network-theory-based model, which is rooted in an energy density function derived from the force-extension relationship of a single chain. Our objective was to create a model with nearly incompressible properties in order to investigate the impact of compressibility. To determine the direction of the Poynting effect, we directly computed the stress and strain responses of a cube under shear forces. Later, we developed a method for predicting the direction of the Poynting effect without the need for precise stress and strain calculations. Our results demonstrate the successfulness of this prediction method.

The simulation outcomes reveal a closer alignment of the four-variable tensor, suggesting that our chosen boundary conditions more closely resemble those used in numerical solutions. Additionally, it is worth noting that the specific geometries we employed in our study, namely the cylinder and cube, did not have a discernible influence on determining the direction of the Poynting effect, especially within the context of the selected model and material parameters.

Boron-based two-dimensional materials showcase promise in variety of fields like hydrogen storage, fabrication of electronic devices and catalytic applications. These materials have garnered interest owing to their unique properties such as high electron mobility, high gravimetric capacity for hydrogen especially after metal decoration, thermal conductivity and tensile strength amongst others. However, for sustained operations of the devices involving these materials, their chemical stability against oxygen is of paramount importance. Especially in the applications involving exposure of the material to air. Abundance of oxygen in the air and its high reactivity increases the likelihood of oxidation of the material. In this work, chemical stability of hydrogen passivated 2D Boron structures; Borophane and 2D Boron Hydride against oxygen were analysed. First-principles calculations reveal that Borophane and 2D Boron Hydride have a less negative binding energy thus indicating that the oxygen binds less strongly to compared to Borophene which does not possess surface passivation by hydrogen. Experimental studies in the literature involving synthesis of 2D Boron Hydride reported presence of vacancies. The effect of vacancy site towards the reaction with oxygen was therefore analysed to maintain consistency with the synthesized materials. The simulations were performed on Borophane and 2D Boron Hydride by introducing a Boron vacancy in the system. The DFT simulation of defect containing Borophane revealed that oxygen binds less strongly in the physisorbed state and more strongly in the chemisorbed state, relative to the values obtained for Borophane without any defects. In case of 2D Boron Hydride it was observed that the vacancies provide a stable site for oxygen, for both physisorbed and chemisorbed state. From these simulations we can conclude that presence of vacancies in Boron based 2D materials generally leads to a stable site for oxygen.

Climate change is one of the top global issues that the United Nations has identified that can adversely impact people all around the globe. Moving towards a hydrogen economy can reduce greenhouse emissions produced from burning fossil fuels which is one of the biggest contributors to global warming and climate change. Hydrogen fuel has a high gravimetric density and being a clean fuel it has the potential to become a sustainable energy source for the growing market. However, its low volumetric density makes it a difficult fuel to store, thus making storage technologies in the hydrogen supply chain an important part. The current storage technologies, however, are impeded by shortcomings such as low hydrogen densities, extreme pressure and temperature operating conditions and inefficiencies during the storage process. Combining existing hydrogen storage technologies such as compressed hydrogen gas and metal hydrides with 2D materials comes across as an excellent option as they can complement each other in their functioning. In this regard, borophene is considered a viable material for hydrogen storage due to its lightweight, good thermal, mechanical and electrical properties. Most of the studies performed so far on hydrogen storage in borophene were on hydrogen physisorption via weak van der Waals forces. In this thesis work, the chemisorption of hydrogen on borophene via strong covalent bonds is studied. This is because borophene with chemisorbed hydrogen is more energetically stable than with physisorbed hydrogen. Also, chemisorbed hydrogen on borophene performs better than physisorbed hydrogen in terms of safety and long-term storage. Hydrogen chemisorption on pristine, defective (i.e. with single and double vacancies) and metal decorated borophene are studied in this work, using density functional theory (DFT) and nudged elastic band (NEB) calculations to compute quantities such as enthalpy and activation energy barriers of chemisorption. Using Bader charge analysis and partial density of states analysis, it was observed that the addition of charge on the hydrogen bond weakens the bond, expediting the chemisorption reaction. The charge transfer from borophene to the chemisorbed H atoms was found to stabilize the final chemisorbed state. In the case of metal decorations, there is an additional steric factor that influences the activation barrier height for chemisorption. In general, metal decorations performed better than pristine and defective borophene systems in terms of the desorption barrier height, among which double decorated K atoms on borophene substrate had the best performance, improving the barrier height by 20% compared to the corresponding value for the pristine system.

As a result of the Paris Agreement, energy technologies require to shift from fossil fuel based to carbon neutral. In 2015, the maritime sector was responsible for 2.6 % of the global CO2 emissions. The combination of the solid oxide fuel cell fueled by sustainable synthesized ammonia is seen as a potential solution to
reduce emissions. Ammonia is considered as a balanced solution in terms of ease of storage, volumetric energy density and cost of production. The solid oxide fuel cell is generally regarded to be a promising technology owing to its high eciency and combined heat and power usage. This MSc thesis investigates the technical viability of a sustainable SOFC propulsion system fueled by ammonia. Technical viability is expressed in equipment weight and volume, whereas sustainability is determined by efficiency and emissions. The solid oxide propulsion system is subjected to a case study: A diesel engine powered vessel from the Watertaxi Rotterdam company with an assumed shaft power of 25 kW. A model was compiled to determine the efficiency, weight and volume of the solid oxide fuel cell system. The model covers activation losses, ohmic losses and diffusion losses within the solid oxide fuel cell stack. With the model, a sensitivity study with a selected set of system parameters was performed to gain insight in the solid oxide fuel cell system. The selected system parameters are: Number of cells in the stack, single-pass fuel utilization, cathode off-gas recirculation rate and anode off-gas recirculation rate. The final solid oxide fuel cell system has a signicantly higher efficiency based on the higher heating value than the diesel engine system: 46.0 % versus 35.0 % respectively. Also, no carbon dioxide is emitted, leading to a reduction of 56.9 ton per year. Furthermore, nitrogen oxide emissions are considered to be negligible compared to the diesel engine system. However, the weight and volume of the solid oxide fuel cell system are signicantly larger: 1199 kg versus 278 kg and 1175 L versus 432 L respectively. Mainly caused by the battery module, required for compensating for temporarily imbalances between power demand and power supply. As a result, it is concluded that the solid oxide fuel cell system is unpractical for the small inland vessel selected for the case study. Larger sized vessels have more potential for the application, because large sized vessel sail more continuously, reducing the battery capacity requirement, may allow for more tolerance regarding heavy and bulky equipment and have more benefit of the higher efficiency due to a lower refuel frequency.