The objective of this study is to generate insights into the application of the reliability of a W2H system and its impact on the techno-economic performance. This involves examining the case of a single system to analyse on a micro-level the underlying conditions affecting performance, as well as exploring W2H farms to observe performance and the effects of changing conditions on a macro-level. To this end, MATLAB models have been utilised and developed to simulate various components of a system, such as wind turbines and electrolysers, focusing on aspects like hydrogen production and the number of breakdowns per year. The model creates insights into technical and economic parameters.

Shipping is, and will continue to be, the most important transportation method around the globe. A vital part of the logistic chain, it is also one of the main contributors to the worldwide CO2 emissions. Current propulsion technologies all rely on the same classic diesel driven technology, as diesel is widely available and has a high energy density. The goal of this research is to identify greener solutions to propel a vessel sailing for short distances. During a definition study, several fuels and energy converters were studied and benchmarked based on a use case. The results showed that (a combination of) the dual fuel internal combustion, using bio diesel and hydrogen, and the low temperature proton exchange membrane fuel cell, fuelled with hydrogen, is the most feasible setup for the use case. Such a combination in itself is not a new one, but in the literature only an all-electric setup is described. In the proposed solution an internal combustion engine is driving the propellor shaft directly, assisted by an electric motor powered by the fuel cell. Based on this outcome, the following research question was defined: How can an internal combustion dual fuel engine and/or LTPEM fuel cell be integrated to form a cost effective solution to propel a short sea ship running on hydrogen? First, nine designs were created, ranging from a conventional diesel engine setup as a reference case, to a fully electric design powered by fuel cells. All main components in these designs are analyzed regarding part load efficiencies. With these efficiencies, the fuel consumption at different loads are calculated. Based on a use case scenario the total fuel costs are calculated. The CAPEX and the OPEX of the designs are determined to calculate the total costs. As currently no other fuel can compete with diesel, the designs are compared based on the price per tons of CO2 emissions, as the shipping industry is expected to see a CO2 emission penalty in the near future. For each design, what the height of this penalty has to be to reach the breakeven point at the end of the use case was calculated. Based on the lowest CO2 price, an all-electric, fuel cell powered design was identified as the most promising option. Applying additional operational arguments such as redundancy and end user acceptance, it was decided together with Conoship to choose a combination of an internal combustion engine and a fuel cell. This configuration is worked out in detail to answer the sub questions, covering efficiency improvement and system integration, during which it became apparent that not all information is available to answer all these sub questions. The design needs further research in a multidisciplinary team. A simulation model would be helpful in this further research. A framework and a start to such a model was written together with a list of recommendations.

Methane pyrolysis is a technology that has the potential to greatly reduce the CO2 emissions of hydrogen production on a large scale. The process generates solid carbon instead of gaseous, thereby inhibiting emissions and has a relatively low process energy demand. A three-step approach was taken to investigate the feasibility of offshore methane pyrolysis for sustainable hydrogen production. Firstly, a model was developed to evaluate the potential for converting methane into hydrogen under various design scenarios. Secondly, the model was utilized as a tool to create an offshore design for the methane pyrolysis reactor, including necessary auxiliary equipment. Finally, a calculation of the levelized cost of hydrogen (LCOH) was conducted to compare it with conventional methane reforming technologies for hydrogen production. The ultimate results showed a higher LCOH of offshore methane pyrolysis compared to the reforming technologies, however, two main components were identified that have the potential to close this gap. First, the sales of the solid carbon by-product would reduce the LCOH of offshore hydrogen and second the introduction of a CO2 tax would increase the LCOH of reforming technologies where methane pyrolysis is not affected. Thus, it can be inferred that offshore methane pyrolysis can be cost-competitive under the appropriate conditions.

Increase in global energy demand has brought to a massive rise in greenhouse gases emissions. In particular, the continuously increasing atmospheric concentration of carbon dioxide is a major concern among the scientific community. This paved the way for an intense research of CO2 emissions mitigating technologies. Those ones including carbon capture, storage and utilisation are seen as part of the solution for this global problem. In this framework, Zero Emission Fuels (ZEF), a startup company located in Delft (The Netherlands) set the ambitious goal of developing a micro process plant producing methanol from ambient air and sunlight only. Part of the process involves direct capture of carbon dioxide from the atmosphere (direct air capture) with the use of a pure tetraethylenepentamine (TEPA) absorbent. ZEF sets itself aside from the rest of the industry developing an absorber which collects CO2 with no support structure by continuously flowing TEPA inside open channels. Previous research shows how this approach brings limitations connected to slowly diffusing CO2 molecules in the absorbent liquid film in proximity of the gas-liquid interface. In this framework, circulation of TEPA particles from the gas-liquid interface into the bulk of the flowing absorbent is seen as a viable solution to improve the process. This thesis focuses on investigating this hypothesis by inducing mixing on the liquid side. That is done by building two experimental setups investigating both passive and active mixing. Experimental results show that active mixing can be used to improve the rate of CO2 absorption, while passive mixing does not bring significant advantages. Results from the passive mixing experiments are further investigated by modelling the fluid dynamics of the process through a Direct Numerical Simulation of the particular Stokes’ flow in the engineered absorption channel. The process is characterised with the definition of a theoretical framework describing mass transfer in the liquid side. Following an analogy with ice formation on top of a frozen lake, this theory, also known as the ”Ice-Sheet” theory, shines some light on the way this diffusion limitations are happening at a molecular level. In particular, a highly viscous, heavily loaded layer of sorbent on the gas-liquid interface is believed to be the cause for observed CO2 diffusion limitations. This theory is backed-up by defining its mathematical equivalent in the form of a mass transfer model. Comparing the results of the model with experimental results, a very good agreement is observed. That is believed to add credibility to the proposed theory. Moreover, that is also found to be in line with the latest knowledge available in literature about CO2 absorption in TEPA films. Finally, the experimental results and the developed models are used to engineer a new iteration of ZEF’s absorber on a cost reduction basis.

Carbon sequestration involves the conversion of carbon dioxide gas into carbonates through reactions with magnesium or calcium bearing minerals, presenting a potential method to mitigate CO2 emissions and reduce their release into the atmosphere. This process can be classified into two categories: in-situ (subsurface) and ex-situ (surface). CO2 mineralization has demonstrated the ability to permanently store substantial quantities of CO2 without the need for extensive post-monitoring efforts, while also offering potential business model benefits for the generated end products. However, the field of mineralization still faces substantial technical and economic challenges, including high cost projections and slow carbonation kinetics, impeding further technological advancements in the field. Additionally, logistical challenges related to plant design and associated emissions contribute to the complexity of finding solutions to these problems. In this particular study, the investigation focused on ex-situ carbon dioxide sequestration primarily through direct aqueous mineral carbonation, incorporating a direct air capture element. This approach was chosen due to the flexibility provided by direct air capture in terms of CO2 supply and the desirable characteristics of direct aqueous carbonation. Various models were developed using Aspen Plus software and compared, leading to the selection of the direct aqueous carbonation system as the optimal choice for CO2 carbonation. Further enhancements were implemented in the system, including recycled streams and heat integration, to reduce overall energy consumption. Optimization steps were also undertaken to determine the appropriate sizing of key equipment that make up the majority of the system's overall costs and to improve system efficiency. An economic analysis was then performed, revealing that plant scales of 50 ktons/year yielded a positive Net Present Value (NPV), indicating profitability. Conversely, smaller-scale plants of 0.5 ktons/year and 5 ktons/year did not generate positive revenue, even with a high carbon credit price. This was followed by a sensitivity analysis that showcased the relevant parameters that holds significant effects on the economic performance of the system. Moreover, business model cases were also explored, and it was concluded that utilizing the end products in building materials and road construction could potentially generate additional revenue for the mineralization system beyond storage options. Overall, this investigation highlights the potential of ex-situ carbon sequestration through direct aqueous mineral carbonation, considering direct air capture, and emphasizes the importance of economic viability and revenue diversification in the successful implementation of mineralization systems to mitigate the effects of global warming.

Using the IEA Ammonia Roadmap aligned with the IMAGE electricity scenarios, an extensive database was produced allowing for prospective LCAs across three storylines from 2020 to 2050 (SSP2-Base, SSP2-RCP26, SSP2-RCP19). The scenarios correspond respectively to 3.9, 2.0, and 1.5°C of global warming in 2100 (vs. pre-industrial levels). Regionally, China produces the largest volume of ammonia as well as the ammonia with the largest climate change impact, due to the dominance of coal gasification technology. To meet 1.5°C of warming (the most sustainable scenario) a global decrease of fossil-based ammonia is needed. For many regions, electrolysis (yellow) ammonia becomes the technology with the lowest global warming potential by around 2045 in the RCP26 storyline and 2035 in RCP19. Until the regional electricity mixes are cleaner, steam reforming, steam reforming with carbon capture and storage, or methane pyrolysis offer lower emission options. However, electrolysis using on-site or designated renewable energy can create emission-free green ammonia, without waiting years for a cleaner regional grid. This means that electrolysis is the best choice for new plants if a producer is not making urea on-site (or has an alternative source of carbon dioxide if they are). Reduction in urea demand will be important for reducing reliance on steam reforming and coal gasification, and a swift uptake of electrolysis with designated renewables must be the focus. However, burden shifting associated with the dominance of renewable electricity systems and bioenergy carbon capture and storage in the RCP19 scenario must be taken into account.

In recent years, the energy transition has led to increasingly higher installed capacities of intermittent renewable energy sources. This has sparked the interest in power-to-fuel technology to store excess renewable energy in the chemical bonds of synthetic fuels. As a highly reactive, turn-key process, plasma-chemical conversion offers a promising approach to power-to-fuel technology. However, recent studies have shown limitations in either energy efficiency, conversion or flow rate. The novel Spinning Arc Plasma Reactor (SAPR) developed by J. van Kranendonk stabilises the plasma by mechanical rotation with the potential to contain a liquid film for in-situ product removal. The aim of this thesis is to characterise this reactor by studying the effect of rotational confinement on the reactor performance. To this end, the prototype initially built by J. van Kranendonk was further developed. A wealth of recent studies on the plasma-chemical conversion of CO2 as a step in the formation of synthetic fuels serves as a benchmark to compare reactor performance of the SAPR concept against. A series of experiments with argon were performed to establish the relationship between the system variables (pressure, power, flow rate and rotational speed) and the plasma parameters (electron temperature and electron density). Based on this knowledge, a series of experiments with CO2 were performed to establish the relationship between the reactor performance measured by the conversion and energy efficiency and the system variables: pressure, power and flow rate. The maximum conversion of about 30% to 55% was obtained at an energy efficiency of approximately 0.25% and the maximum energy efficiency of about 3% was achieved at a conversion of approximately 8.5% conversion. Similarly to other studies, improvements to either one came at the expense of the other. The performance of the SAPR proved comparable to dielectric barrier and other glow discharges but was outperformed by microwave and gliding arc discharges. Especially energy efficiency was inferior to these configurations. Further analysis of the discharge emission spectra suggested that CO2 dissociation mainly occurred through electron impact excitation. This explains the large difference in energy efficiency as microwave and gliding arc configurations are able to exploit more energy efficient dissociation channels. Nonetheless, this study was able to further develop the concept and has laid the ground work to explore the potential effect of a liquid film and in-situ product removal on the reactor performance.

The petrochemical industry accounts for approximately 20% of global industrial CO2 emissions. Ethylene manufacturing is one of the major components and has a high carbon footprint. This study explores the use of proton-conducting electrochemical cells (PCECs) for ethylene production - the WINNER process. This non-oxidative dehydrogenation (NODH) reaction is still thermochemical, but the hydrogen is electrochemically removed, enhancing the conversion of ethane. The electrochemically enhanced production of ethylene demonstrates substantial improvements over conventional steam cracking. It decreases Specific Energy Consumption (SEC) by approximately 20%, curtails thermal energy demand by 80% and enables operations at a lower temperature of 550°C. Some parameters are less favourable, but nonetheless, the reduction in SEC indicates a promising potential to decrease carbon emissions attributed to utility consumption. Economically, the WINNER process outperforms the steam cracking benchmark, with a nearly doubled margin, almost tripled Net Present Value (NPV), and a seven-times higher Internal Rate of Return (IRR). The Minimum Selling Price (MSP) of ethylene reduces by roughly 30% in the WINNER process. Additionally, the WINNER process produces pure, pressurized hydrogen as a high-value byproduct, adding to the economic viability of the process. A sensitivity analysis indicates that the most influential parameters are the prices of ethylene, ethane, and fuel gas. Under current U.S. grid conditions, the Product Carbon Footprints (PCFs) of the WINNER process and the steam cracking benchmark are approximately equal. An increased contribution from renewable energy sources would enable the WINNER process to lower the utility-based PCF of ethylene production. In conclusion, the WINNER process exhibits superior techno-economic performance and potential environmental advantages over the steam cracking benchmark, making it a promising alternative for sustainable ethylene production. Therefore, this work lays the groundwork for a sustainable and profitable transition in ethylene production, leveraging advances in electrochemistry.

Rising concentration of CO2 in the atmosphere has become a significant concern, paving the way for worldwide research on mitigation techniques like carbon capture and storage (CCS) and carbon capture and utilization (CCU). Zero Emission Fuel (ZEF), an aspiring startup based in the Netherlands, aims to develop a micro plant that produces methanol from just solar energy and air. Their process involves capturing CO2 and H2O directly from the air, splitting H2O to obtain H2 and producing methanol by reacting CO2 with H2. The focus of this research is on the absorption process of ZEF's direct air capture unit. Instead of capturing CO2 and H2O through a widely used batch direct air capture process, ZEF chooses to side with a novel continuous absorption and desorption process involving a flow of bulk polyamines without any conventional support structures. Polyethyleneimine (PEI-MW-600) and Tetraethylenepentamine (TEPA) are used as absorbents to achieve a target of capturing 825 grams of CO2 in 8 hours every day from a single direct air capture unit. Preliminary investigations show that the viscosity of PEI-600 is significantly higher than that of TEPA. An increase in CO2 concentration increases the viscosity of both polyamines significantly. In comparison, increasing H2O concentration leads to a maximum viscosity point in both polyamines and subsequent decrease in viscosity with a further increase in H2O concentration. Although, compared to CO2, H2O has a smaller effect on viscosity. Moreover, premixed samples of PEI-600 and TEPA with H2O show an increase in the CO2 absorption rate when pure CO2 is bubbled through the samples. In order to study and characterize the novel absorption process, an experimental setup facilitating a flow of absorbent is developed, and experiments are conducted following an experimental approach to calculate the mass transfer rates and average concentrations of CO2 and H2O. Fourier-transform infrared spectroscopy is used to estimate these concentrations. Experiments are performed on different initial concentrations of PEI and TEPA. TEPA is found to have a better absorption performance with an average CO2 absorption rate that is two times higher than PEI-600. Contrary to preliminary investigations done by bubbling CO2 into polyamines, absorbents with premixed water flowing down a channel were found to have lower CO2 absorption rates than pure polyamines. A multiple regression viscosity model, heat model, and a model of absorption column is developed using the data collected to estimate average viscosity, the heat of absorption of water, and characteristics of the absorption process. Diffusion of CO2 through the absorbent layers is found to be the primary limiting factor, while mass flow rates of absorbent and air are also found to influence the absorption process. Finally, a design of the absorption column is made to meet ZEF's requirement taking into account various performance characteristics studied during the thesis.

The dwindling of natural resources, mainly fossil fuels, and the alarming increase in the global average temperatures, are the biggest concerns of the engineering and scientific community of 21st century. Studies have found that known reserves of oil and natural gas will last another 50 years. Coal will last another 110 years, which points towards dire consequences. The experience will not be that of a car slowly running out of gas, but rather like driving off a cliff, since we innately depend on these resources. The realization of these concerns has lead to a rise in the investments all over the globe for Sustainability. The right questions are now being asked. How can we fulfill our demands without compromising the demands of our future generations? One of the keen areas of interest is the conversion of power into fuel. Synthesis of hydrocarbons from sequestrated carbon can produce carbon-neutral fuels that can replace some of the conventional fossil fuels. Methanol has been actively wiping the floor with the research community due to its simplicity of production and less toxic nature. While there are quite a lot of ways of producing methanol, very few of them are carbon neutral. Zero Emission Fuels B.V. has embarked on a venture to produce methanol by a totally carbon neutral process. They begin by capturing carbon dioxide and water from air and splitting the water into hydrogen and oxygen using solar power. Carbon dioxide and hydrogen are then combined in a reactor to form methanol, making a truly carbon-neutral process. They aim to make fuel consumption, a completely circular process while keeping it economic. An experimental characterization of ZEF’s methanol reactor under varying pressures and H2/CO2compositions was done. The new reactor design focuses on heating the feed gases before catalyst bed, more heat integration, reliable sensor data, and the ability to mix gases in desired compositions. Methanol yield, quality, energy efficiency, reactor inlet and outlet temperatures, power requirements were experimentally determined in a transient analysis. It was seen that the reactor produces 4.84 mmol/gcat /hr of methanol at 50 Bar and reactor wall temperature of 250◦C with H2 : CO2 = 3:1 mol% feed gas. The catalyst exhibited partial deactivation during night after shutdown. Contrary to expectation, the reactor produced more methanol at lower pressure. The production was reported at 5.96 mmol/gcat /hr at 35 Bar. Although, only 4.36 mmol/gcat /hr at 25 Bar. Moreover, the pressure reduction caused the natural circulation to slow down, and increase the inlet temperature from 208◦C at 50 Bar to 234◦C at 35 Bar, which is the reason for the observed increase in yield. It can be concluded that the reactor yield under these conditions is limited by kinetics and not thermodynamics. The reduced mass flow rate allowed the reactor to consume less power and show higher energy efficiency. It increased from 34.7% at 50 Bar to 43.2% at 35 Bar. The rate of pressure decline in the reactor was correlated with the methanol yield using gas law by accounting for non-ideality with the compressibility factor. The predicted yield was seen to be in good agreement with experimentally determined. The methanol yield of the reactor with variable feed gas composition was obtained for 50 Bar and 250◦C reactor wall temperature and seen to decrease on either side of the ideal composition. It was concluded that the yield becomes both stoichiometrically and kinetically limited. It is recommended that similar experiments be done at increasing temperatures and equilibrium yield be determined experimentally. Additionally, the reactor needs to be operated with varying compositions and higher reactor wall temperatures at constant pressure, to obtain the operating line for maximum production of reactor.

CO2 concentration in the atmosphere is increasing leading to global warming and thus, climate change. Moreover, current renewable technologies such as wind or solar energy only cover the electricity market. A big part of the global energy market is still based on fossil fuels and difficult to electrify. Hence, there is an urgent need to produce renewable liquid hydrocarbons to replace fossil fuels. Zero Emission Fuels (ZEF) is a start-up that aims to develop a small-scale chemical plant to convert carbon dioxide (CO2) and water (H2O) from the air into methanol (MeOH) using photovoltaic energy. In this work, the absorption of CO2 using bulk polyamines was characterized experimentally, as well as through numerical modelling. In addition to this, guidelines for the design of the absorber, part of the Direct Air Capture (DAC) unit of ZEF’s micro-plant, are given. The focus of the study is placed on the kinetics and loading of CO2. To be able to model the absorption process an experimental approach has been developed regarding the uptake of CO2 and H2O. Firstly, pure H2O absorption experiments were performed in a climate chamber in order to obtain the H2O loadings using polyamines for different H2O content in the air. Secondly, air capture experiments were performed at lab conditions in order to obtain both H2O and CO2 loadings for different process conditions. Thirdly, constants relevant for the modelling part (reaction rate constant and Henry constant) were obtained experimentally. An absorption model, developed in MATLAB, was used to estimate the diffusion coefficient of both H2O and CO2 using the experimental H2O and CO2 loadings. Two main conclusions are obtained from the absorption model of CO2: the absorption of CO2 on polyamines is diffusion-limited and the diffusion coefficient of CO2 is two orders of magnitude lower than the diffusion coefficient of H2O. Based on the fact that the CO2 absorption process is diffusion-limited the mixing patterns should be introduced in the design of the continuous absorber. However, due to the fact that viscosity could influence the flowing behaviour of polyamines, more research is needed.

The primary objective of this study was to address the lack of understanding of the commercial- scale implementation of novel CO2 based carbon nanomaterial (CNM) production and its comparison with status quo CNM production processes using unsustainable fossil resources. To accomplish this objective, first, a literature review was performed on the status quo commercial- scale CNM production, the lab-scale CO2 based processes and the CNM market. In regards to the status quo processes, the literature review yielded mainly chemical vapor deposition (CVD) processes of carbon nanotubes (CNTs) and graphene production. With respect to the lab scale CO2 based processes, the literature review involved categorising the identified processes into four different approaches based on their working principles - CO2 based CVD, molten salt based electrochemical CO2 reduction, liquid metal catalyst aided CO2 reduction and metal reductant enabled CO2 reduction. With regards to the CNM market, CNT materials were found to have the highest market share followed by that of graphene. Startup spinoffs working on the graphene and CNT production from CO2 were identified with origins to university-based research groups. Following such literature review, a framework was developed to select one process each from the status quo CVD processes and the novel CO2 based processes, which produced comparable CNM. This framework was applied to the processes obtained from the literature review, which led to the selection of a methane-based CVD process and a molten salt-based electrochemical CO2 reduction process for small-diameter multi-walled (MW) CNT production. The methane-based CVD process involved the use of Ni-Mo catalyst on MgO support and high-temperature operating condition of 975°C. The molten salt-based electrochemical CO2 reduction process involved the use of Ni and steel electrodes, pure molten Li2CO3 electrolyte and high-temperature operating condition of 750°C. These selected processes were designed and simulated in Aspen Plus at a commercial-scale production level of 5000 tonnes per operating year. The mass balance, energy balance, and equipment cost data obtained from the simulations were used to assess the technical, economic, and environmental performance of the ex-ante CO2 based production process and the status quo CVD production process. The technical performance assessment involved the estimation of resource intensity and energy efficiency indicators of the two processes, wherein the CVD process outperformed the electrochemical process in both indicators. The economic performance assessment involved the estimation of total capital investment, operational expenditure, net present value, and payback period. The CVD process performed better than the electrochemical process in all the indicators except total capital investment. Both processes indicated positive net present values and short payback periods, indicating the realisation of commercial scale plants of both processes to be profitable. The environmental performance assessment was carried out using the life cycle assessment methodology in the CMLCA software. The climate change impact indicators at scope 1 and 2 levels along with the net avoided impact from using CO2 were estimated using the CML 2001 impact assessment family. The electrochemical process was shown to perform considerably better than the CVD process in all the climate change impact indicators. Overall, the technical and economic performance of the CVD process was better than that of the electrochemical process. However, the environmental performance of the electrochemical process was shown to outperform that of the CVD process. The limitations associated with modeling decisions taken in the two processes and with the uncertainty associated with the lack of data were highlighted. Further, the relevance of this study was discussed with respect to the industrial symbiosis potential of using waste CO2 from industries leading to GHG emission reduction and subsequent deceleration of climate change impacts. Finally, future potential studies were highlighted that could build on the research and insights generated in this study. One of these studies involved a case study on the implementation of a commercial-scale electrochemical process for MWCNT production in Port of Rotterdam region. Another study involved a techno-economic and environmental assessment of atmospheric CO2 capture and conversion to carbon nanomaterials for applications that can potentially achieve net negative emissions.

Green hydrogen has a pivotal place in the energy transition, addressing carbon emissions in hard-to-abate sectors. As global hydrogen demand rises, decarbonizing green production becomes vital. This study explores the influence of design choices and local weather patterns on the Carbon Footprint (CF) and Levelised Cost of Hydrogen (LCOH) for green hydrogen production. An optimisation model is developed, simulating the production chain (cradle-to-gate) and optimising it for low CF and LCOH based on location-specific wind and solar data. Three locations (Duqm, Groningen, Dakhla) and three design choices (electrolyser, PV type and wind-solar ratio) are assessed. Results indicate that local weather patterns significantly affect system performance. Dakhla boasts low production costs due to consistent solar and wind energy. Groningen has a low CF but high LCOH due to ample offshore wind but inconsistent sun. Duqm has a low LCOH but high CF due to abundant sun but inconsistent wind. Design choices, particularly the solar-wind energy ratio, strongly impact both LCOH and CF. PV technology selection also matters, with CI(G)S performing well overall. Alkaline electrolysis is preferred over PEM. The research demonstrates that design choices can substantially influence the CF, resulting in serious CF reduction at prices comparable to blue hydrogen. Future research should include storage, transportation, and off-taker aspects and expand impact categories, including social and critical raw material depletion impact categories.