As the world population is increasing and cities grow faster than before, food scarcity becomes a bigger issue. To depend less on import and decrease CO2 footprint, food should be produced nearby its consumers. A good solution for food production is a greenhouse which provides a steady high yield throughout the year. Some of the world's fastest growing cities are in Subtropical climates. Subtropical climates are characterized by high temperatures, abundance of sun and high humidity. Due to the high temperatures, cooling in greenhouses in subtropical climates is necessary, but evaporative cooling is not sufficient due to the high humidity. Outside air can be dehumidified by a liquid desiccant to cool the air further with an extra evaporative cooling step. After dehumidifying the air, the absorbed moisture from the air in the desiccant must be removed from the desiccant solution for re-use. This requires a lot of energy, which makes this cooling technique for greenhouses in subtropical climates not economically feasible. The proposed solution is to remove moisture from the desiccant by making use of the hot air that can be collected in the top of the greenhouse. The potential of this solution is assessed in this study. To predict the transfer of mass and heat between air and a calcium chloride solution as desiccant, a mathematical model of the process of mass and heat transfer over a structured cardboard pad is made. An experiment is conducted to validate the mass and heat transfer coefficients of the model. The model is used to evaluate the workings of the proposed system of regeneration. Results show that dehumidification can significantly lower the inlet temperature of the air in the greenhouse, provided that the inlet temperature of the desiccant is low. Regeneration of the desiccant solution with hot air is also possible, provided that the air in the greenhouse is significantly heated by the sun and pre-heating of the desiccant before regeneration is beneficial. The direct coupling of these two systems is not sufficient due to the big difference in temperature of the desiccant that is required at the inlet of the dehumidifier and regenerator. In future work attention should be paid to this temperature difference which is currently limiting the performance of the system. Then it's possible for the concentration of the desiccant to be brought back to the starting conditions for the dehumidifier.

The Beam Dump Facility (BDF) is a new fixed target facility proposed to be installed in the North Area of CERN. Currently in its design phase, the BDF is aimed at the Search for Hidden Particles (SHiP) experiment, which purpose is to investigate the origin of dark matter and other lightly interacting particles. The BDF target/dump sits at the core of the installation, and its aim is to fully absorb the high intensity Super Proton Synchrotron (SPS) beam and produce charmed mesons. The average beam power on target is 305 kw due to which very high thermo-mechanical loads will be generated on the target/dump configuration which can lead to mechanical failure of the target material. This calls for continuous cooling and heat removal from the target material, which requires the design and optimization of a very complex cooling system to ensure the target reliability during operation. Keeping in view the high velocities that are obtained in the channels of the cooling system of the target assembly, an extensive 3D turbulence modeling of the full scale cooling system is required in order to predict the target water cooling system behavior. A comparative conjugate heat transfer (CHT) study using a simplified 2D geometry of the BDF target for different mesh size was performed for identical y+ values to validate the pressure drop in the cooling channels and the temperature profile in the target blocks with the analytical calculations. Subsequently, a 3D model of the cooling channel was simulated for different Reynolds number and an extensive study was performed to check the behaviour of the flow in the log-law layer. In addition to that the friction factor was validated with the analytical results and with the available literature for various Reynolds number. Thereafter a full scale 3D steady and transient model was simulated using the information obtained from the previous studies. All these simulations were carried out in Ansys Fluent. The energy deposition in space on the target blocks was obtained via FLUKA MonteCarlo simulations. The variation of HTC in different channels and the fluid-solid interface temperature is found out to be in accordance with the analytical calculations. The pressure drop and the temperature rise from inlet to outlet of the cooling system is also in confirmation with the design parameters. Transient simulations were performed subsequently in order to study the impact of time and space varying energy deposition in the target blocks on the overall flow. With the given inlet velocity, the boiling at the surface of the target blocks is not expected to happen. As a final part of this study, in order to make the numerical model more robust, a mesh sensitivity analysis was done in order to optimize the mesh size, especially in the boundary layer region.

To answer the need for renewable fuels, Zero Emission Fuels is designing a microplant to create methanol from carbon dioxide and water from the ambient air using only renewable energy from solar panels. For this microplant, gaseous carbon dioxide must be compressed from 1 to 50 [bar] with the low mass flow of 336.7 [g/h]. This thesis examines the compression system which uses rolling piston compressors. This thesis also examines a solution to compress the carbon dioxide optimally. Because of the low mass flows, the compressors are very small and have relatively high friction and leakage losses. Meanwhile, due to the high pressure ratio of the system, the temperature increase due to compression also poses a problem for the lubrication of the system. Therefore, this thesis looks for solutions for these problems while trying to gain a better understanding of what exactly is happening inside the compressors. For the temperature regulation, different options for active cooling were assessed with a dimensionless analysis. Eventually, the concept of cooling through the compressor housing was chosen. Afterwards, a computational model was made to calculate the inner workings of the compressors and assess whether the concept of active cooling would still work. Then the computational model was verified by doing experimentation. After that, the results from the model and the experimentation were compared. The model was able to predict the mass flow and the outside heat transfer coefficient accurately. However, the model was still off from the experimental values by quite a margin. After assessing all the data, the system seemed to perform better as a 2-stage system then as a 3-stage system. However, due to the inaccuracies of the model and experimentation, a definite recommendation on the number of stages of the system cannot be formed.

In order to reach the goals of the Paris Agreement, global emissions must decrease at a high rate. Looking at the industrial sector, the largest share of energy is used for process heating, with fossil fuels as its primary source. A way to improve the energy efficiency and reduce the emissions of process heating is by the integration of heat pump technology. However, operational costs are still a limiting factor in the widespread uptake of this technology. A potential of industrial heat pumps that will have a positive effect on the operational costs, as well as its general applicability, is the possibility to operate the equipment in a flexible manner. At this point, the potential to respond with high temperature industrial heat pumps to heat demand, the electricity market or to grid congestion, is not yet unlocked. The focus in this study is on gaining more insight into the dynamic characteristics of industrial heat pump operation. The approach is based on the modeling of a 2 MW high temperature industrial heat pump in the Dymola simulation environment. Based on the system dynamics, a suitable control method is selected and the controller settings are optimized. With this control system in place, the dynamic limitations are studied. The limiting factor in the considered economizer based heat pump cycle is the ability of the control system to keep the superheat at the screw compressor injection port within acceptable limits during load level changes. The heat pump is found to be able to ramp up and down at a maximum rate of approximately 20%/min. This level of flexibility allows use of the heat pump for both heat demand and electricity price response, as well as for participation in grid load balancing pools. On a higher level, based on these results flexible heat pump operation can be considered possible.

This report presents the first simple and comprehensive method to effectively compare different infrastructure configurations for reservoirs that have been found suitable for long-term storage of carbon dioxide. Modelling the different transport phenomena along the chain, this study identified a fixed set of input parameters and used them to evaluate the differences between existing and new infrastructure. The report then explores how these differences affect the conditioning steps the CO2 must undergo before injection.The model was then applied to a a test case, the P18-2 natural gas reservoir 30km north-west of the Hague. The results for this test case show that an auxiliary pumping step is required for supercritical injection at the desired pressure. Subsequently, the results are used to develop a conceptual design for a module that can either be installed on a new platform or retrofitted to existing offshore production facilities, allowing them to be used for conditioning and injection of CO2. Last, the economic feasibility analysis demonstrates that reusing existing infrastructure can reduce the costs of transport and storage of CO2 by over 50%.

Firing industrial installations, like boilers, with a cogeneration gas turbine instead of a classic burner have several beneficial aspects. A cogeneration system allows for a more efficient utilization of energy and lowered emissions. What makes such a system especially interesting is that the revenue of the generated electrical power can outweigh the extra costs required to operate a gas turbine for producing a specific amount of thermal energy. The technical challenge, covered in this thesis, consists of improving a gas turbine for cogeneration applications relative to a classic burner. The solution can be found in reduction of the high stack losses, as these comprise the main disadvantage of firing a boiler with a gas turbine. This research focuses specifically on cogeneration with the PowerBurner, a gas turbine developed and manufactured by Innecs Power Systems, located in Ter Aar, the Netherlands. The goal of this study was to identify, analyze and conceptualize methods that reduce the stack losses of a PowerBurner used for the production of steam. Implementation of such methods should allow the PowerBurner to become a more attractive alternative for steam production compared to a conventional burner. Four concepts were identified which could improve operation of a cogeneration gas turbine: Steam injection, flue gas recirculation, supplementary firing and implementation of a boiler in the combustion chamber, the Velox boiler. A thermodynamic model of a gas turbine was created in Thermoflex. The model was based on the design point specification of the PowerBurner, from which it deviates less than 1% at any point in the process. Implementation of steam injection was able to induce the largest increase the electrical efficiency, from 10.5% to 20%, whereas flue gas recirculation resulted in the highest increase in total efficiency, from 85% to 95%. With supplementary firing and the Velox-type boiler, the thermal capacity and -efficiency could be increased the most, from 2 MW to 6.8 MW and from 74% to 90%, respectively. The profitability of each setup compared to making use of a conventional burner for an equal thermal output was determined. Supplementary firing allows for the most profitable operation. A qualitative cost analysis showed that supplementary-fired setup required the least capital expenditures. From a combination of the thermodynamic and economic characteristics, the supplementary-fired PowerBurner was chosen to be the best alternative for replacing a conventional burner for the production of steam. A conceptual design of a burner for such an application was created in ANSYS Fluent. The design was able to operate with fuel inputs of at least 0.485 MW up to 4.85 MW. 100% Combustion efficiency was achieved over the full range. Pressure losses over the burner are low at 1.6 mbar. Whether the current burner design results in a stable flame cannot be determined from the model. A NOX analysis in Fluent indicated that the emissions of NOx are over the Dutch regulation standards for gas turbines, but the accuracy of this result is not known. Therefore, future research is required to determine flame stability and pollutant emissions.

Restrictions on NOx emissions are increasingly stricter. In order to reduce the emissions of a gas turbine, manufacturers moved from diffusion-flames to lean premixed flames in their combustion process. However lean premixed flames are prone to (transverse) combustion instabilities. These instabilities consists of thermoacoustically driven pressure oscillations. In order to mitigate acoustic oscillations, dampers are implemented in a gas turbine combustion chamber. These dampers have proven to be effective, but they also consume cooling air, which has a negative impact on the efficiency of the gas turbine. Therefore in this thesis, a solution that potentially provide damping without consuming cooling air is investigated.

Water is the most dominant substance on the planet and has always been a synonym for life. On this planet, water has always been plentiful. Therefore, the conclusion of the United Nations in 2015 was even more shocking. The United Nations estimated that in 2030 a water gap would exist of 40%. The withdrawal of fresh water would be 40% larger than the amount that is replenished every year. We are living on borrowed time, and we need to close this gap. Since most water on the earth is saline, desalination could be a possible solution. Unfortunately, desalination is an energy-intensive process, and it will always be. There are different methods. However, energy consumption would always be rather large. Much of our energy is still created by fossil fuels in most areas in the world. Our increasing demand for fresh water can lead to a further large fossil footprint and therefore more climate change. Climate change negatively impacts our water supplies. A negative spiral could be the result. The world is consuming a large amount of energy. Unfortunately, this is not done efficiently. It is estimated that 72% of worldwide energy consumption is lost after conversion. Waste heat is an unwanted product as a result of this inefficient conversion. It is estimated that 63% of this waste heat has a temperature of 100 degrees Celcius or lower. A temperature that is not even sufficient to boil an egg, but it is energy nonetheless. If this energy could be harvested, the water gap could be closed by desalination without increasing the carbon footprint. However, how to do this? A solution could be found in Japan and your dry cleaner. In the seventies, when the oil crisis was at its peak, Japan had a problem. It has a high need for air conditioning which has a high need for energy. A device was created that could use waste heat to create cooling with silica gel. The general public knows silica gel as moist eaters that are included in your dry cleaning. By placing silica gel in a closed environment, liquid water could be evaporated. Evaporation needs energy, and this could create cooling. In early 2000, some folks in Singapore realised that this technology could also be used to desalinate. Adsorption Desalination was born. Adsorption desalination (also known as AD) is a boiling point elevation and vapour pressure lowering desalination technique. Silica gel has a high affinity to adsorb water vapour. Since this is done in a closed environment, the pressure is lowered till boiling. When an energy source is placed inside the liquid, an equilibrium can be found without lowering the pressure further. Once the silica gel is saturated, it is heated till a certain temperature that it starts to desorb the vapour again. This vapour is collected and condensed into a clean product. The mass transport takes place by a pressure difference. Since the evaporation takes place in vacuum conditions, it is around room temperature. Therefore it can have a low sensitivity for erosion. Since it is an evaporation technique, it also has a low sensitivity for fouling. On paper, it can be a desalination technology with low operational costs compared to others. In reality, a couple of barriers have to be conquered. One of the barriers is the characteristics of the core element of this technology, the silica gel. The reason that silica gel can adsorb water vapour so well is due to two main elements. First, it is an incompletely dehydrated polymeric structure of colloidal silica acids. Therefore it can create hydrogen bonds, polar bonds and weak electron bonds with other molecules. Water is a bipolar molecule, and therefore silica gel can adsorb water exceptionally well. It can create hydron bonds efficiently, and due to the bipolar nature of water, multiplayer on top of each other can be formed. The second element is the high specific surface of silica gel. It has many pores, and therefore a specific surface equal to human lungs can be formed. In the end, the best qualities can adsorb until 40% of their body weight. These two elements determine the maximum amount of vapour silica gel can adsorb. However, two parameters determine if silica gel can adsorb. These two parameters are the temperature and vapour pressure. If the temperature is high, the vapour pressure has also to be high to ensure adsorption and the other way around. The same account for the opposite effect. Therefore energy transfer is vital for smooth operation. Unfortunately, the thermal conductivity of silica gel is extremely low. Besides energy transfer to change the temperature of silica gel to go from adsorping to desorbing and reverse, much energy has to be transported during the adsorption and desorption phase. During adsorption, water vapour transforms from a gas phase to a semi-solid phase. In this phase, the energy level is lower. Since energy cannot be destroyed, this energy has to be removed. The same applies to the opposite. If the heat exchanger is not well designed, the adsorption and desorption phase are prolonged, and the daily water production diminished. Even if the whole set-up is well designed, there is still one element of silica gel that can also diminish the water production of the set-up: the degradation of silica gel. Multiple mechanisms can degrade silica gel, but the two most important are fragmentation and pore pollutions by metal ions. Fragmentation (the breaking up into smaller parts) occurs by the high thermal stress the silica gel endures and the pollutions by the feed. A part of the sorption ability is destroyed or temporarily inhibited. The use of acid water can remove the pollution, so maintenance on the silica gel is necessary. Replacing the silica gel by other sorbents like zeolite is possible. Unfortunately, it has a lower adsorption capacity which leads to a less compact device and is, therefore, more expensive. Another unfortunate fact is that zeolite desorbs at a higher temperature. When using zeolite, adsorption desalination can no longer use waste heat of low quality to desalinate. The last problem with using silica gel, but also other sorbents, are the instabilities with the sorption characteristics in vacuum conditions. The sorption characters depend as said before on the temperature and the vapour pressure. Inside vacuum conditions, a disturbance of the vapour pressure can negatively influence the sorption characteristics and can lead to desorption at the wrong moment. Since it is done in a closed environment, it can lead to condensation which lowers the vapour pressure further. A complete breakdown of performance can be the result. Disturbances can happen through air leakage, which is are a common problem in industries. There are some solutions, but in the end, the permanent one is a high-quality vacuum system and intensive maintenance. Even with these barriers, adsorption desalination is still an attractive technology due to its relationship with its own energy consumption pattern. The energy consumption is high but stable and barely sensitive to change in conditions like feed salinity and recovery. Its energy consumption stays around the 40 $kWh/m^3$ in most cases. Only a small part, around 1.38 $kWh/m^3$ or even less has to be mechanical energy. All others can come from waste heat. If the other operating costs are kept low, it is an exciting technology to use, especially for brine treatment since waste heat is an inexpensive energy source. Some researcher claim it is a free energy source, but that statement cannot be valid. To use waste heat, infrastructure is necessary to collect it and transport it. It is not the same as putting a plug in the wall. There is probably enough waste heat in the world to close the water gap. As an example, the Netherlands is the second biggest producers of waste heat in Europe and creates enough to produce probably more 850 $km^3$ potable water. Unfortunately, there are some uncertainties. Waste heat is only classified in three rough categories, low, medium or high. Low is everything below 100 degrees Celcius. It could be that most energy is trapped in waste heat with a temperature of 30 degrees. More validation is necessary since the future of adsorption desalination is intertwined with waste heat. Without waste heat, it cannot be an inexpensive desalination technique. Since it is still an experimental technology, not a lot of data is available to create a solid picture of the costs involved with adsorption desalination. Only two studies exist today, and both estimate that the cost for seawater desalination using adsorption desalination is between 50% and 70 % of the cost while using reverse osmosis. Only one study gives insight into the different sectors of cost. What is notable is that the other costs, replacement cost for parts and chemical cost for adsorption desalination are kept at zero. A strange conclusion since silica gel can degrade and replacement can be necessary, chemicals are necessary for the heating and cooling water AD uses. No conclusion can be made about the final costs of AD, but it the conclusion of these studies seems unlikely. For seawater desalination, the costs are probably in the same range as reverse osmosis. Furthermore, there is a strong case that AD can remove biological pollutants since it is an evaporation technique where temperatures are reached until 80 degrees Celcius. There are a few remarks and only solid empirical data can prove these claims. The original intent of this research was to research these claims. Unfortunately, the set-up was not functioning properly due to practical problems like air leakages. Even with this result, much knowledge was gained, and a few remarks and conclusions can be made. To conclude, adsorption desalination is a newly emerging technology with many interesting aspects. It can provide an alternative for standard desalination techniques while being sustainable. There are a few barriers to overcome, but it deserves attention. Further developments should be stimulated since the water should be close in an environmentally friendly matter. Adsorption desalination is a sustainable solution that should always be considered.

Environmental regulations are continuously raising the bar towards more advanced diesel engine designs ca- pable of minimizing the emissions of polluting substances. The recent IMO Tier III legislation, entered into force in 2016, is forcing the engine manufacturers to meet a NOx reduction of more than 70% from Tier II for all the ships sailing in designated NOx Emission Control Areas (NECA). Although these zones are, up to now, limited to the North American and U.S. Caribbean Sea NECAs, future regions, such as the North Sea and Baltic NECA in 2021 as well as stricter national and port regulations, are increasing the uncertainty regarding the possible compliance methods. The Selective Catalytic Reduction (SCR) represents a flexible, proven and commercially available technology capable of reducing more than 80% of the NOx in the exhaust gas. Its adoption started in the ’70s and was aimed at the reduction of stationary source emissions. From early 2000, it has been extended to the automotive industry in order to meet the Euro and EPA legislation for heavy duty and light diesel engines. Despite the evident disadvantages of the high installation cost and the considerable space requirements, the application of the SCR is subjected to a number of operating limits such as the narrow optimal temperature window and the slip of byproducts originated from the chemical reactions. These limitations can be even more severe when the diesel engine undergoes transient and dynamic operations. The main objective of this research is to gain insights into the behaviour of the SCR technology under steady-state and dynamic operations of the diesel engine. After an accurate literature review of the working principles, reaction kinetics and modeling approach, a first principle model of the SCR has been developed to fulfill the scope. A 1D single channel approach, discretized along the reactor length, has been adopted to sim- ulate the heat exchange and the chemical reactions occurring in the catalyst. To facilitate the integration of the designed model with an existing diesel engine model available in the Maritime and Transport Technology Department of the 3me faculty, the resistance and volume approach has been selected. After the verification of the SCR model, the integrated system "SCR+Engine" has been tested under steady-state conditions, to an- alyze the effect that the added back pressure has on the engine performance, and under dynamic conditions, to simulate "real" load case scenarios that the SCR might experience. The designed model, although limited from the chemical reaction point of view, is able to predict NOx reduction and ammonia slip under steady-state and transient operations. It can be further used in an early design phase to investigate the feasibility of the SCR inclusion in the drive trains of ships. Future studies are recommended to optimize the model, by taking into account the sulphur influence on the reduction efficiency and the catalyst aging, and to validate it with real experiments on marine SCR systems.

Large quantities of heat stored in geothermal aquifers can be of interest to satisfy above-ground heating demands. With the use of heatpipes, placed into the aquifers, heat may be passively extracted. Vertical two-phase thermosiphons are considered in this study. As a result of a local increase in the saturation temperature in liquid pools, heat can only be transferred in the falling liquid film. The aim of this work is to investigate film heat transfer and its limitations at varying boundary conditions in the evaporator of a vertical experimental setup. An initially homogenized film is studied in a separate film heating section, in which a specific distribution of controlled band heaters and temperature transmitters enables the sensing of local film heat removal behaviour in the heatpipe. With increasing degrees of wall superheating, the mean film heat removal rate has been found to increase. Locally, beyond some degree of superheating, the heat transfer rate stagnates with increasing Jakob numbers, possibly as a result of film dry-out. As a result of such local behaviour, the slope of the mean heat transfer rate curve decreases with increasing Jakob numbers. The onset of dry-out, characterized by an increase in the intermittency of the results, has been studied by varying the initial liquid flow rate to the heated section. Both the initial film flow rate and the degree of superheating have been found to be of significance for the onset of film dry-out. Film dry-out takes place at flow rates less than some critical flow rate. The local heat removal rate decreases significantly if the initial film flow rate is decreased beyond the critical flow rate. The critical flow rate has been found to increase with increasing rates of superheating. The significance of the saturation temperature on the film heat transfer rate has also been studied in this work. The film heat transfer rate has been found to decrease with decreasing saturation temperature, for all in this study considered degrees of superheating. The steepest decline in heat transfer rates with decreasing saturation temperature is found for the smallest degree of superheating in the analysis. At last, the possibility of film re-distribution following dry-out has been considered. Melamine foam homogenizer rings, inserted in the film flow path, have been found to decrease the degree of film thickness variation in initially inhomogeneous films to some extent. Homogenized films were found to be able to transfer a greater amount of heat than films that had not been re-distributed.

The vehicle industry is increasingly exploring emission-free mobility. Transforming the mobility sector to zero-emission vehicles that consume renewable and low carbon fuels is necessary to reduce the impacts on climate change. Hydrogen powered electric vehicles, or Fuel Cell Electric Vehicles (FCEVs), could make a significant contribution to reduce GHG-emissions and energy use in the transport sector. The current refuelling network for hydrogen vehicles is in its very early stages. The Cogeneration of Hydrogen, Heat and Power project (CH2P) aims to impact the sector with a more efficient solution for the growing hydrogen infrastructure. It does so by offering very efficient decentralized H2 refuelling stations. The goal of this project is to design a refuelling station that has the ability to refuel hydrogen vehicles and to charge electric vehicles. The onsite CH2P production system is based on SMR and SOFC technology. A thermodynamic model has been designed to size and optimize all the station components. This includes the compression, intercooling, storage, throttling, precooling and dispensing of hydrogen, and the storage and charging of power. Main messages to take away from this analysis are the following: CH2P as a decentralized production method is protable. For higher station utilization the NPV has the potential to increase further by 55 %. Cascade filling of vehicles reduces the total storage and energy demand, and greatly reduces the CAPEX of the station. The optimal configuration consisted only of 950 bar High Pressure Storages. By adding a battery to the station, the system can power five fast-chargers to charge BEVs. However, power production by CH2P is more expensive than grid power and the current electric system is not sufficient for coping with sudden power fluctuations.

The efficient and clean combustion of liquid fuels is a fundamental requirement in the design of future energy systems. Simulation plays a more and more important role in the design of such burners. In this work the spray combustion simulation approach introduced by Ma (2016) is improved, and validated against the CORIA Jet Spray Flame database (Verdier et al., 2017). The database presents droplet temperatures measured by global rainbow refractometry technique, which gives a unique insight in the flame structure. The two phase flow is treated with an Eulerian-Lagrangian approach. Flamelet Generated Manifold (FGM) is used to model the gas phase combustion. The RANS equations are solved using final volume method, with standard k − ε turbulence modelling. The turbulence-chemistry interaction is addressed with assumed probability density function method. The spray cloud is modelled with the Lagrangian transport of droplets including heat and mass transfer. Ma (2016) developed a solver based on the OpenFOAM 2.3.x libraries. His development is complemented in this work with a novel spray model. The improved spray modelling allows the treatment of droplet evaporation in the context of FGM without limiting the complexity of the chemical mechanism. This improvement is crucial for the modelling of complex fuels and the correct prediction of emissions. The modelling concept is rather light-weight considering the RANS approach. Despite the low computational expenses, most of the results agree fairly well with the measurement data. However the correct prediction of droplet temperature remains an an unresolved problem. Ma, L. (2016). Computational modelling of turbulent spray combustion. PhD Thesis, Delft University of Technology. Verdier, A., Santiago, J. M., Vandel, A., Saengkaew, S., Cabot, G., Grehan, G., and Renou, B. (2017). Experimental study of local flame structures and fuel droplet properties of a spray jet flame. Proceedings of the Combustion Institute , 36(2):2595-2602.

The global market for the wastewater treatment industry has been compelled to devise new concepts due to several factors. Currently, approximately 80% of untreated wastewater is discharged worldwide. The conventional technology for municipal solid waste treatment, which has been in use for over a century, is only partially effective in terms of effluent quality and energy balance. The highly flammable CH4 gas emitted from municipal solid waste landfills impacts the chemical composition of the atmosphere, potentially affecting the Earth. Thus, new concepts for wastewater treatment should address multiple social challenges related to energy and sanitation technologies. A well–implemented wastewater treatment system not only contributes to mankind wellbeing, which results in more effective population planning, but also ensures the optimal utilization of environmental resources.....@en

Mimetic discretization methods are emerging techniques designed to preserve, as much as possible, properties of the continuous differential equation. In this framework the geometric nature of physics plays a crucial role. Thus, it is necessary to use a new language to model physical problems, Differential Geometry. The calculus of differential forms reveals intrinsic structures that usually, are obscured by metric notions implicitly encoded in vector calculus. In the language of differential forms the unified treatment of scalar and non-scalar advection is simplified by the use of one operator: the Lie Derivative. Much attention has been devoted to the discretization of scalar advection problems in numerical analysis. Therefore, it would be expected that non-scalar advection is not common or relevant. This is not true. The so-called magnetic advection in electromagnetism or the advection of vorticity in fluid mechanics are examples of important non-scalar fields. Furthermore, it is widely known that the classical Galerkin formulation when applied to scalar convection may lead to spurious (non-physical) oscillations. The goal of this thesis is to derive a physically accurate discretization of the generalized advection problem. Thus, very small or even vanishing artificial diffusion should reflect the robustness of these methods. Also in this thesis, geometric structure-preserving semi-Lagrangian and Eulerian discrete schemes are derived.

Increased climate change over past decades has resulted in an increase in the average temperature (also called global warming) of Earth’s climate system. At the recent Paris climate conference (COP21) in 2015, 195 countries in the world have agreed upon a stringent plan to limit global warming below 2oC. This demands a significant reduction in the industrial emission of greenhouse gases, predominantly carbon dioxide (CO2). Existing fossil fuel (coal, natural gas) fired power plants account for the majority share in global carbon dioxide (CO2) and other harmful (SOx , NOx) emissions. Therefore clean, efficient and flexible power plant concepts need to be developed towards upgrading existing power plants and to meet the strict CO2 emission targets. Combined cycle power plants like the integrated gasification combined cycle, IGCC (coal based) and integrated reforming combined cycle, IRCC (natural gas based) can be utilized to produce electricity using fossil fuels at relatively high efficiencies compared to conventional single cycle plants. Possible approaches to make IGCC/IRCC power plants cleaner, efficient and more flexible include biomass utilization (renewable energy source), application of CO2 capture technologies, retrofitting with highly efficient fuel conversion technologies like solid oxide fuel cells (SOFCs) and energy/fuel storage. This dissertation primarily aims to provide design concepts and thermodynamic system analysis for large scale IGCC and IRCC power plants with a focus on achieving high electrical efficiencies, low CO2 emissions and high operational flexibility. SOFCs have been explored as an efficiency augmenting technology and metal hydride based hydrogen storage as a flexibility option. Furthermore, future development of safe and optimally operating hydrocarbon (like natural gas (methane)) fuelled SOFC units on the basis of system and numerical models, requires reliable experimental data and understanding in the underlying reaction kinetics. Thereupon, an extended experimental study has been carried out in this work on methane steam reforming (MSR) kinetics in single operating SOFCs.@en

A deeper understanding of physics is required when the complexity of events increases. A complex event consists of many detailed interacting processes. The complete picture asks for an understanding of each of the processes individually. Numerical computing in the maritime industry is becoming more relevant due to the increase in usability and relatively low costs compared to experiments. The numerical results allow for analysis at the required level of detail. The complexity of water-wave impacts on offshore structures necessitates innovative numerical approaches because conventional analytical techniques fall short of representing the non-linearity in these events....@en

Fossil fuels are currently the primary source for electrical power generation, which subsequently increases the rate of greenhouse gas (CO2, CH4) emission. It has been agreed at the Climate Change Conference 2015 in Paris (COP21) to reduce greenhouse gas emissions in order to limit the global temperature increase to less than 2°C compared to pre-industrial era temperature. The GHG (Greenhouse Gas) effect is mostly attributed to methane and carbon dioxide emissions into the atmosphere. In order to reduce the use of fossil fuels and their negative impact on the environment, renewable energy resources have been receiving much attention in recent years. Sanitation systems, centralized Wastewater Treatment Plants (WWTPs) and organic waste digesters give an ample opportunity for resource recovery to produce biogas that contains mainly methane and carbon dioxide. The low conversion efficiency of conventional energy conversion devices like internal combustion engines and turbines prevents biogas from reaching its full potential as over 50% of chemical energy is dissipated. Wastewater treatment is a developed technology from human health and environmental-friendliness points of view. However, from energy aspects, it is still an energy-intensive process step. Wastewaters might contain significant amounts of organic matter and nutrient (nitrogen and phosphorus) compounds. The chemical energy in domestic wastewater is approximately 3.8 kWh.m-3 based on theoretical Chemical Oxygen Demand (COD) of 1 kg m-3. At wastewater treatment plants (WWTPs), collecting and treating wastewater streams need a considerable amount of electricity (0.5 kWh m-3) to reach an acceptable quality of discharge requirements. In a conventional WWTP, nitrogen is removed through nitrification, and biodegradable organic matter is converted to methane in anaerobic digestion. The energy demand at WWTPs could be partially offset by an efficient recovery of nutrient and organic matter from the wastewater stream. Biogas production is an important technology widely applied in Europe. Biogas can be converted to energy through thermal conversion with combined heat and power (CHP) plants. However, the electrical efficiency of the system is limited to 25-30%. In parallel, nitrogen can be removed from wastewater and converted and stored in the form of an ammonia-water mixture from ammonium-rich streams after anaerobic digestion. Solid oxide fuel cell (SOFC) is an energy conversion device that directly converts chemical energy into electrical energy based on electrochemical reactions. SOFC can operate with different types of fuels, especially unconventional or renewable fuels. The efficiency of SOFC is higher compared to conventional combustionbased processes. Therefore, the sustainability of WWTPs can be improved first by a recovery of nutrient and organic material from the wastewater stream and then, replacing the inefficient combustion process with an efficient high-temperature electrochemical reaction in SOFC. Due to the modularity of SOFC, this can be used for a wide range of biogas production capacities at WWTPs. However, the development of SOFC is still facing many challenges, and a better understanding of the constraints is needed. This dissertation aims to provide design concepts and thermodynamic system analysis for the biogas-ammonia fuelled SOFC system at wastewater treatment plants with a focus on achieving a safe operating condition and high electrical efficiencies. Thereupon, extended experimental studies have been conducted in this work on biogas dry and combined reforming. Moreover, the influence of mixing ammonia-water to biogas in SOFC has been experimentally investigated. After indicating the safe operating condition of biogas-ammonia fuelled SOFC, system modelling studies have been carried out in order to design an efficient conceptual biogas-ammonia fuelled SOFC system at wastewater treatment plants. Additionally, a complete biogas SOFC pilot system consists of a gas cleaning unit and an external gas processing system has been designed. @en