In conventional compressor technology, high pressure ratios are often achieved by multiple, successive compression stages. This is done to avoid high temperatures due to the adiabatic nature of most compression processes which deteriorates the working of oil lubrication. The aim of this work is to reduce a conventional four-stage system to only two stages as this may improve the size and expenses of the system. This goal combined with a long desired lifetime, makes that a compressor is developed that operates based on gas bearing technology.

The design is focused on two main subjects. Firstly, the load capacity of the gas bearings is significantly lower than oil lubricated bearings due to the reduced viscosity. To avoid mechanical contact and wear of the components this has been thoroughly analysed using finite element methods. The oscillating nature of the loads in the system enhances the squeeze effect from the Reynolds equation. Secondly, the sealing function of gas bearings opposing internal leakage is evaluated carefully to obtain a desired efficiency. Based on these simulations, the mechanical design of the compressor is optimized to improve the manufacturing of the compressor components.

This study provides suggestions to decrease hot utility use and impact on the environment of a skim milk powder (SMP) processing plant. These suggestions are based on the integration of waste streams with processes in the production of SMP. To identify appropriate waste and process streams, process integration has proven to be a successful method. This concept addresses the issue of waste heat of a process by pointing out to the importance of the relation between unit-processes. In this study, the integration of waste streams is accomplished by heat exchangers, heat pumps and a zeolite wheel. The general assumption underlying this research, is that recovering heat from unused waste streams decreases hot utility use. Multiple methodologies were used in this study. To accomplish process integration, the pinch analysis forms an essential tool. This analysis was used to identify potential heat recovery schemes in the SMP plant. Furthermore, to fully understand these schemes, a thermal, environmental and economical analysis was done. These analyses were based on mass and energy balances, (in)direct CO2 emissions and investment and operational costs. Several conclusion can be drawn from the pinch analysis. First, the pinch temperature is 50◦C. This represents the dividing line between processes which require heating and cooling. Second, the heating and cooling demand is known. The SMP production process requires 6.8 MW of external heating and 1.7 MW of external cooling. Third, the amount of recoverable heat is equal to 5.3 MW. Fourth, appropriate heat sink and sources are identified. The heat sources, i.e. waste streams, are the spray dryer exhaust and the the condensate streams from two evaporators. The supply temperatures of the exhaust and the condensate streams are respectively 77, 65 and 55◦C. The appropriate heat sinks are the spray dryer air inlet and the evaporator product inlet streams. The target temperature of the spray dryer inlet and evaporator inlet streams are respectively 190, 75 and 70◦C. Seven heat recovery setups are proposed. In terms of saved energy, the spray dryer exhaust has the most potential for heat recovery. The zeolite wheel is the best performing heat recovery technology in the spray dryer process, with a recovery of 3.5 MW. Furthermore, a heat exchanger-heat pump combination and a stand-alone heat exchanger recover respectively 1.8 and 1.6 MW. In contrast, the evaporation process has less potential for heat recovery. The best performing configuration is a heat pump, recovering 1.4 MW from the evaporator condensate. The environmental performance is strongly related with the amount of energy saved. This is because the most decisive parameter in the environmental analysis is the carbon intensity of natural gas and electricity. The best performing configurations in terms of saved CO2 emissions are the zeolite wheel (3806 ton/yr), the heat exchanger-heat pump combination (1934 ton/yr) and the stand-alone heat exchanger (1593 ton/yr) in the spray dryer process. In the evaporation section, the heat pump saves 1485 ton CO2 per year. The total annual costs are derived from the equivalent annual costs of the asset, carbon savings and utility savings/costs. The best performing configuration is the heat pump in the evaporation process. This technology has an annual return of 145 ke per year. Other configurations with a high return are the stand-alone heat exchanger (143 ke/yr), the heat exchanger-heat pump combination (128 ke/yr) and the zeolite wheel (123 ke/yr).

The maritime sector is important for the facilitation and growth of global trade. Currently, about 90% of the goods are transported by ships and as a result, the number of ships has risen, increasing the emissions related to shipping. Pollution caused by exhaust gas, especially the sulphur oxide emission, from marine diesel engines has become a global concern in recent years. Therefore, the International Maritime Organisation limited marine fuel sulphur content in both Emission Control Areas to 0.1%w/w since 2015 and globally to 0.5%w/w since January 1st , 2020. It is anticipated, that the newly implemented IMO regulations will help to mitigate negative impact of ship emissions on public health and the environment in the coastal areas. The wet scrubber system is a reliable technology for flue gas desulphurisation in marine applications and can achieve a sulphur dioxide removal efficiency of 98%. The operating costs are low, however the capital cost for installation are high and a scrubber system requires space for installation while maintaining ship’s stability. Wet scrubber systems operating in a closed loop and using caustic soda may operate without discharge to the sea and thus are allowed to operate in ports. The use of caustic soda also makes it possible to use the scrubber in areas with low seawater alkalinity. However, scrubber systems generally operate at 100%, even when the engine operates at lowload. This results in an increase of the fuel consumption and carbon dioxide emissions. Themain objectives of this research are to examine the influence of water evaporation on the sulphur dioxide removal efficiency and the (response of the scrubber) effect of dynamic loads on the scrubber efficiency. A dynamic model of a closed loop wet scrubber operating with fresh water and caustic soda also known as sodium hydroxide was created and verified. The scrubber model consists of three resistance elements, namely the venturi scrubber, the tower scrubber with a packed bed and the demister and two volume elements (lower and upper) to connect the resistance elements. The absorption of SO2 is mainly taking place in the packed bed and the two phase flow of exhaust gas and scrubbing liquid was modelled in this section. The Nerst film theory was used and extended to a two film theory in which the exhaust gas and scrubbing liquid phases come into contact through an interface and exchange both heat and mass. The gas flow in the packed bed could be modelled with a combination of resistance and volume elements as this phase is compressible. The liquid flow and liquid film thickness in the packed bed were modelled based on the conservation of mass and the liquid holdup theory developed by Billet and Schultes. A feedback control system controls the scrubbing liquid flow based on the sulphur dioxide to carbon dioxide ratio. The system includes a time constant to account for the inertia of the scrubber’s pump and pipe system. The verified model was integrated with engine data and used to run several static and dynamic simulations. The inclusion of evaporation in the packed bed leads to an increase of the scrubber efficiency in all engine loads. The extra vapour added dilutes the gas phase and reduces the mass fraction of sulphur dioxide. When evaporation is included in the analysis, the sulphur dioxide to carbon dioxide ratio leaving the scrubber is 1.88, equal to a fuel sulphur content of 0.043% on a mass base (from 3.5% in the fuel) for 100% engine load. When evaporation is not included in the analysis the previous values are 2.3 and 0.053% respectively. To increase the precision concerning the amount of water that evaporates, a higher discretisation of the packed bed is required. High engine load fluctuations and/or high input frequencies lead to overshoots and higher liquid supply, in order to keep the scrubber system efficient. In the transition from 25% MCR to 100% MCR the liquid supply exceeds the nominal value of 94 kilogram per second by by 5.3 kilogram per second (or by 5.6%). In the transition between 75%MCR to 100%MCR, for the frequency of 50 seconds the liquid supply is equal to 92.9 kilogramper second. Increasing the input frequency 5 times results in an increase of the liquid supply to 96.1 kilogram per second. The sulphur dioxide to carbon dioxide ratio leaving the scrubber was always below the ECA sulphur limit and was fluctuating around the set point, but most of the time below it. A combination of feed forward and feedback and/or a more advanced control may result in a more stable control of the scrubber, but this has to be investigated. The model functions, but more research is required for the venturi and the demister models, but also for the packed bed model. In the venturi a three phase flow is required and in the demister an analytical and dimensional analysis is required. Also, the packed bed model needs to be further developed to include the condensation effect and a more precise approach for the liquid phase. Further research can be done on the integration of the model with a diesel engine and SCR model. Also, seawater can be examined as a scrubbing liquid as this may reduce the operational costs of the scrubber. Finally, because space requirements of the scrubber are high, a structured packed bed could be an alternative to the dumped and reduce the space occupied by the wet scrubber.

In an effort to replace fossil fuels by more sustainable solutions, the demand for green hydrogen hasgrown significantly over the last few years. This has raised the interest in electrolysis and has boostedits development. Water electrolysis produces hydrogen and oxygen from water using direct current,nowadays often with an electrochemical efficiency of around 80%. Although much effort has beenmade to reach such high efficiencies little research has been done on the excess heat produced byelectrolysis. This thesis intends to cover this topic, mainly focussing on Proton Exchange Membrane(PEM) electrolysis. All of the inefficiencies of the electrolyser translate into heat and it is the objective ofthis research to investigate how much of this heat can be extracted and contained for use in a separateapplication. Furthermore, in the second part of this thesis, the available applications are studied in anoffshore and onshore production scenario to better understand potential of this heat.In order to accurately simulate the thermal behaviour of a stack of PEM cells an electrochemical andthermal model was created representing the average largescalePEM electrolyser of today. Furthermorea basic integrated cooling system was designed in order to assess how much heat can be extractedfrom the stack and at what temperature. The system consists of separate channels for coolingwater inside the bipolar plates that separate the individual cells. It was found that well over 90% ofthe heat produced by the stack can be extracted in the form of cooling water at a few degrees (<3표퐶)below stack temperature without impeding the performance of the stack. The largest contributor to heatbeing lost, was found to be the production of water vapour on the anode side of the cells which can bereduced significantly by operating with an elevated pressure in the anode chamber (5 bar).In the onshore case study it was found that an electrolyser is very well suited to be connected to adistrict heating network. The low temperature heat serves well for applications such as space heatingand/or water heating. In an offshore scenario the excess heat can serve to aid in thermal desalinationhowever it proved to be more difficult to find an adequate application for the full amount of producedheat.In conclusion, the models presented in this thesis have shown very satisfactory results in terms potentialof excess heat. It has proved to be a very interesting field of study and more indepthresearchas well as broader studies on possible heat applications can be conducted to fully understand thepotential of excess heat from electrolysis.

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.

The main objective of the thesis is to analyze the potential for improving the aerodynamic efficiency of Siemens SGT5-2000E turbine section by optimizing the blade shapes. An adjoint-based shape optimization is implemented at the mid-span of the axial turbine. The optimization is performed, for the stator and the rotor individually, to reduce the entropy generation (objective function) with mass flow rate as the constraint.

The design optimization methodology is implemented using SU2, an open-source computational fluid dynamics (CFD) tool coupled with the adjoint-based optimization technique. The SU2 optimizer algorithm begins by computing the objective function of the existing design by using the flow solver. The flow simulation is performed by solving the RANS equations and SST turbulence model. The discrete adjoint solver utilizes the objective function and constraints to evaluate the gradients of the objective function with respect to the design variables. Each of the design variables is altered to improve the shape and the gradients are used to find an optimal search direction. The algorithm is structured to iterate until an optimal shape is determined.


The optimization methodology is implemented for the existing stator to reduce the entropy generation and an optimal shape is determined. Then, the rotor is optimized with the outlet conditions of the optimized stator as the inlet conditions. The optimized stator and rotor resulted in a significant decrease in entropy generation of about 16% and 24% respectively. Finally, with the optimized blades the stage simulation is performed which resulted in 1.4% increase in the total-to-total efficiency compared to the baseline stage.

In the quest for renewable energy for tropical islands, Ocean Thermal Energy Conversion (OTEC) has revealed itself as one of the most promising technologies. OTEC stands or falls with the performance of the condenser. Plate Heat Exchangers (PHEs) have proven their selves as effective heat transfer
equipment for low enthalpy cycles such as OTEC. Nowadays, the design of PHEs mostly relies on models based on experimental data. This is deemed time-consuming and non-generic. Enormous successes in the application of Computational Fluid Dynamics to single-phase flows have raised the
interest to use CFD as a predictive and generic tool for the design of PHEs. Moreover, CFD yields a picture of the complete flow field, enabling the designer to better understand the fundamental flow structures that are relevant for the heat transfer and pressure drop performance of the PHE.
First, a comprehensive review of literature on condensation models is presented. Thereafter, the practicality of the phase change models in terms of real computation time needed is investigated. It is concluded that the stability issues associated with the vapor-liquid interface poses the biggest problem.
That is, for the simple Nusselt condensation problem, an extremely long computation time is needed for reasonable accuracy. Finally, the ability of the phase change models to cope with wave evolution,
flow circulation and flow separation is investigated. The multiphase model is found to properly predict the flow field. However, the heat and mass transfer predicted by the condensation models is estimated poorly.
In the end, until the stability issues of the current phase change models are solved, or a significant improvement in computational performance is made, the application of CFD to the design of condensation PHEs is questionable. Yet, using CFD only to find trends in heat transfer and pressure drop in PHEs might prove to be fruitful.

The heat pipe assisted annealing project is a project in which Tata Steel, TU Delft and Drever International work together to develop a continuous annealing line with heat pipes. In an annealing line cold rolled steel is heated to 973 K and cooled down again to change the properties of the steel. In the heat pipe assisted annealing project the cooling line is thermally connected to the heating line via heat pipes. A heat pipe is a closed cylinder which is partly filled with a liquid. Heat pipes are very effective heat transfer devices, due to evaporation of the liquid at one side of the heat pipe and condensation of the vapour at the other side of the heat pipe. Due to rotation and a head, liquid will return to the evaporator side of the heat pipe. Applying heat pipes in a continuous annealing line could lead to energy savings up to 70%.
The TU Delft rotating heat pipe setup is in development for testing the performance of organic working fluids in heat pipes and validation of models, for the temperature range from 423 K to 723 K. The goal of this thesis is described as: finishing the development of the TU Delft rotating heat pipe setup and use this test setup to validate the developed model. This goal was divided into several objectives.
An investigation was made of what has to be done before the commissioning of the setup. It was discovered that the heat input calculation is overestimated, because insulation is not taken into account. Therefore, a new calculation was made. It is concluded that in the worst case scenario 1155 W of heat input is needed. Also, the available band heaters could not be used, therefore IR heating with quartz lamps has been considered. A calculation was made to confirm if they will provide enough power to meet the requirements of the setup. It is concluded that six quartz lamps with an effective heating length of 165 mm will provide enough power. In the fill ratio calculation, it is learned that non-annular flow is beneficial for the heat transfer compared to annular flow. Also, it was decided to fill the heat pipe with 35 grams of Dowtherm A as a start. With this amount of fluid, it is possible to operate the heat in both flow patterns over the whole temperature range. Last, it is concluded that bearing cooling is needed.
Another objective was to select the required data acquisition hardware and program the required software for control and data acquisition. A compactRIO from National Instruments is selected together with several modules. This configuration is able to process all the signals and has extra capacity to handle more signals in the future. A LabVIEW program was designed to control the Delft setup. This program meets all the requirements. It has been tested with dummy signals and during a leakage test with the actual heat pipe.
A model which represents the actual Delft rotating heat pipe setup has been made. The same inputs as in the Delft setup can be adjusted. This model has been developed as a network model. These types of models are often used because of their reasonably accurate and practically simple way to model transient heat pipe analysis. This model was validated with two different papers. In the first paper, an experiment is performed with a stainless steel ammonia heat pipe, which operates in non-annular flow. The data of this paper is only useful for steady state. At the steady state part, the maximum deviation is 0.96 K. In the second paper, a copper-water heat pipe is used. This heat pipe is not rotating, but has a wick. This means its behaviour is similar to a rotating heat pipe with annular flow. The data of this paper is very precise and shown in tabular form at three different points at 4 time stamps. The root-mean-square error between the experiment and the model at all data points is 0.36 K.
The commissioning of the heat pipe is in progress now. When all the safety procedures are checked, the experiments can be conducted.

Pyrolysis oil (BPO), derived from biomass via the fast pyrolysis process is a potential substitute for petroleum fuels. Due to its distinct physical and chemical properties (highly oxygenated, chemically reactive), the possible range of stable and clean operation in combustion devices is smaller than for petroleum fuel and to enable use of pyrolysis oil in a wider range of applications more insight in pyrolysis heating an evaporation behaviour is required. A surrogate oil of 6 discrete components (water, acetic acid, hydroxypropanone, phenol, eugenol and levoglucosan) is formulated to represent certain aspects of the real pyrolysis oil for computational means. A liquid phase thermal polymerization reaction is formulated to investigate the eect this reaction on the evaporation process. In this reaction, levoglucosan undergoes a dimerization reaction to form a solid dimer. For the evaporation, the Rapid Mixing Model (RMM) is applied, which (mainly) assumes innitely fast liquid phase thermal conductivity. The RMM is adapted for the multicomponent case and the evaporation process is numerically solved for a single stagnant droplet with initial diameter of 100 m in still air (T1 = 800K, p1 = 1 atm). Results of both the model without and with polymerization reaction show continuous variations of the mass fractions of individual components and (pure species) thermophysical properties. At the early stage of evaporation most of the vapor contains the lighter components, i.e. water, acetic and hydroxypropanone. At the end of the vaporization process, only levoglucosan is left in the drop. Furthermore, the results show that the multicomponent fuel does not match the d2 law; there is a high evaporation rate during early evaporation process, while a slower evaporation rate is observed in the further process. Validation with literature experimental data of a real BPO shows a disagreement in trend between model and experiment, with experiment showing a more rapid decrease of diameter over time. However, a better agreement with an experiment on a two-component fuel is observed. To improve the qualitative and quantitative predictions of evaporation rate, a model including gradients inside the droplet and representing the eects of internal bubbling would be required. The model including the polymerization reaction predicts that the eect of the proposed reaction of levoglucosan is very small, with only 0.4% lower evaporated mass of levoglucosan.

Based on the Paris Accord, various governments have agreed to a long- term goal of keeping the increase in global average temperature to well below 2°C above pre-industrial levels; The Netherlands has committed to reduce its CO2 emissions with 80% by 2050; in this plan, the Dutch government has set an ambitious target for the industry to reduce their emissions by 70 million tonnes of CO2 annually. In The Netherlands, the steel industry contributes to nearly 7% of the total greenhouse gas emissions inventory. To meet the Dutch Government target, Tata Steel IJmuiden is exploring various options to reduce its CO2 emissions. One of the options being considered is CO2 Capture, whereby the CO2 could be captured from the Works Arising Gases (WAGs). Currently, the use of chemical absorption is the most mature technology to capture CO2 from any gas. This study has evaluated the performance, equipment sizing and cost of capturing CO2 using MEA or MDEA/Pz solvents. The performance of the chemical absorption process capturing 90% of the CO2 from a mixture of Blast Furnace Gas and Basic Oxygen Furnace Gas has been evaluated. The process was modeled in ASPEN Plus® . For cases using MEA as solvent, the conventional configuration were evaluated. It could be concluded that the optimal lean loading is around 0.19 mol/mol resulting to a specific reboiler duty of around 3.95 MJ/kg CO2 captured. Different advanced process flow configurations were also assessed. The results showed that the use of intercoolers in combination with a flash split-flow or LVC could result in a reduction of the specific reboiler duty. For cases using of MDEA and Pz as solvent, the conventional configuration operating with 1 and 10 bara absorber pressure were modeled. Resulting to a specific reboiler duty of 3.56 and 2.70 MJ/kg CO2 for 1 and 10 bara operating pressure, respectively. Furthermore, different advanced configurations were also assessed. This consisted of the incorporation of intercoolers and 1-stage or 2-stage configurations. With intercooling, the specific reboiler duty could be lowered down to 2.85 and 2.43 MJ/kg CO2 for operating pressure at 1 bara and 10 bara, On the other hand, based on the UCARSOL 1-stage configurations operating at 10 bara, the specific reboiler duty could be reduced down to 2.34 MJ/kg CO2. A reduction in specific reboiler duty for the 2-stage configuration could be significantly lowered. Preliminary economic evaluations were undertaken in this study to obtain the specific CO2 capture cost – based on CAPEX and OPEX estimates using 8% discount rate and an economic lifetime of 25 years. For the MEA cases evaluated, the costs of CO2 captured are in the range of 52.7 to 65.8 €/tonne CO2; the lowest cost is achieved with the LVC configuration in combination with intercooling. On the other hand, the results for the MDEA/Pz cases indicated that the costs of CO2 captured are in the range of 54.1 to 67.3 €/tonne CO2; the lowest cost is given in the configuration with intercooling operating at 1 bara.

Increasing concerns about the effects of freeing large quantities of greenhouse gases into the atmosphere have sparked interest in organic Rankine cycle for renewable power systems. Single-stage radial inflow turbines appear as suitable expansion devices for this type of application. However, supersonic conditions can be reached in the stator of these devices, causing non-ideal fluid-dynamic behavior. This makes it necessary to explore unconventional architectures, for which only a limited number of design methods have been proposed.
In this context, the principal activity of this study was to formulate guidelines, and thereby reduce the preliminary design space, of supersonic radial stator vanes. This was done by first identifying the relevant loss mechanism and design parameters through an examination of the available literature. This led to the formulation of a research hypothesis, which was studied by means of two-dimensional, steady computational fluid dynamic simulations.
To this end, a parametric study was devised, in which any design parameter can be varied to study its effect on the blade performance. This is done analyzing the trends resulting from the post-processing of simulation generated data. The data production is based on a workflow consisting of finding a condition-specific convergent-divergent nozzle, which is used to build a mean-line radial vane, for which a mesh grid is generated and utilized by a previously validated numerical solver to perform the simulations. The complete process was overseen by a semi-automated design chain constructed to manage and execute the necessary steps.
It was assumed that profile losses would be the most influential loss characteristic, given that two-dimensional flow is predominant in mean-line geometries. According to the literature, both its major components, viscous dissipation and mixing losses should have an impact on the stator’s efficiency. Likewise, the degree of expansion along the embedded nozzle present between adjacent blades, was identified as the main design specifications to be analyzed. A trade-off between the contribution of the main loss mechanisms based on the variation of this parameter was predicted to exist.
Applying the generalized research method on a candidate test case resulted in the generation of data from almost 500 different simulations. This led to several findings, including that it is not possible to vary the nozzle design Mach number without causing simultaneous changes to other relevant geometrical features, such as the throat width. This rendered invalid some of the initial assumptions used to set up the experiments.
Similarly, this finding was expected to be the reason behind large differences between the calculated and imposed pressure ratio on the boundary conditions, as well as large variations in the mass flow of each set of blades. Additional simulations were required to analyze these deviations, based on varying other relevant parameters, including the imposed pressure ratio and outflow boundary location. The results seem to suggest that, due to the supersonic nature of the flow, an additional geometrical constraint influences the expansion process.
Performance analyzes were then possible by adapting the definition of valid designs to blade configurations matching or exceeding the imposed pressure ratio. Based on these results, the relevance of the post-expansion ratio (defined as the ratio between the pressure level at the nozzle exit and the stator outflow) became apparent. This was also the case when this ratio was manipulated by changing the imposed back pressure on the system. Moreover, when quantified with respect to this parameter, the flow deviation showed a linear behavior and the losses exhibited a plateau of higher performance.
Finally, this project provides a foundation for this line of research, both in a theoretical and practical sense. Future studies should focus on validating claims made regarding the supersonic expansion process and extending the data to determine the generality of the found performance trends. Only then will it be possible to conclusively establish the dependence between design parameters and performance for this unconventional type of blade.

Carbon dioxide emission into the earth’s atmosphere by maritime activities are a concern for the people within and outside the industry. This is because of the environmental impacts that are caused by these greenhouse gas emissions which changes the very chemistry of this planet. These impacts can be mitigated by reducing the CO2 emissions which can be achieved by several design and/or operational means. Waste heat recovery (WHR) technology is one such means that is capable of reducing emissions. This is achieved by improving the overall fuel efficiency of marine engines which reduces the fuel consumption of the vessel. This improvement is realised by harnessing the heat energy that is expelled by the engine through waste heat sources such as exhaust gas, etc.
 Organic Rankine cycle (ORC) is one of many WHR technologies that is capable of harnessing that waste heat energy from the fuel which cannot be utilised by the engine operation alone. ORC as a WHR system (WHRS) is widely implemented in land based applications due to its fluid choice flexibility, plant simplicity and net efficiency. However, it is rather new to the maritime industry because WHRS on-board ships are predominantly based on steam Rankine cycle or turbo-compounding. These systems have their own advantages but ORC-WHRS may outweigh them in certain applications on-board ships. This is especially for electrical power generation from low and medium temperature waste heat sources. However, ORC in marine application encounters challenges unlike seen in land based applications. These challenges are caused by the physical & geometrical constraints, operational profile of the vessel or uncertainties caused at sea.
 In this thesis, the implementation of ORC-WHRS to marine engines for exhaust gas is investigated and studied to understand how such an application can be beneficial. Unlike steam Rankine cycle, an ORC system has flexibility in choosing an organic fluid that is suitable based on the application. This flexibility in fluid choices are confronted by the above mentioned maritime related challenges. Hence, a screening methodology is devised in this thesis that finds a suitable fluid based on the waste heat source profile and selection parameters. These selection parameters are necessary to filter out functioning organic fluids that can be limited due to the mentioned challenges. In this thesis, the power density of the ORC plant is the selection parameter used.As mentioned earlier, the ORC-WHRS may often be subjected to off-design conditions due to the operational profile of the vessel or by uncertainties at sea. Hence, off-design performance is analysed to study the ORC system when designed at several discrete engine load points. These analysis are carried out in plant models modified from an existing steam based dynamic model and developed into a simple-ORC and a recuperative-ORC dynamic plant models. Sensitivity analysis of these models are also performed to understand uncertainties in the model output corresponding to uncertainties in model input parameter. This analysis is followed by analysis of the dynamic behaviour of the ORC plant model to varying load step functions and step duration for plants designed at discrete engine load points.
 This thesis can be extended, not only to study how ORC can be used to meet future regulations on CO2 emissions, but also on operability limitations imposed on ships. The fluid screening approach used here can also be modified based on parameters, such as toxicity, flammability, cost, specific power etc. This can present a realistic approach to an end product that can be safely and economically operated on board.

New technologies are being developed to produce electricity cleaner and more efficient. A promising technology among these is the solid oxide fuel cell (SOFC). It electrochemically converts chemical energy into electricity. This process is highly efficient and several types of fuel are suitable. Furthermore, the SOFC operates at a high temperature, thus producing high quality excess heat which can be converted into electricity in a thermodynamic power cycle to increase the efficiency. Commonly this is done by a directly coupled gas turbine (GT).
The supercritical carbon dioxide (sCO2) Brayton cycle has recently received attention for its potential as a next generation power cycle. It combines the advantages of the steam Rankine cycle and air Brayton cycle. So far, two heat sources are mainly considered for this cycle: Nuclear and concentrated solar power (CSP).

The aim of this study is to investigate the potential of integrating a SOFC with a sCOs Brayton cycle. A thermodynamic model of the SOFC- sCOኼ Brayton cycle hybrid system (SSHS) is developed to explore and analyze different concepts that effect the integration of both systems. Methane is converted to syngas in an indirect internal reforming (IIR) setup. The steam required for this process is either fed by a heat recovery steam generator (HRSG) or supplied by recirculating
anodic exhaust gas. Both options are considered. Recirculating the exhaust of the cathode is another options that is explored and analyzed. Two sCO2 cycle setups are analyzed in combination with the SOFC system: A simple recuperative
cycle and a recompression cycle.
Different setups of the SSHS are compared on efficiency, complexity of the system and size of the exchangers. For comparison, a directly coupled solid oxide fuel cell (SOFC)- GT hybrid system is considered as well.

It is found that the recompression cycle in combination with SOFC system is more efficient than the simple recuperative cycle but significantly increases the complexity of the heat exchanger network, recirculating cathodic air decreases the size of the heat exchangers and increases the efficiency and supplying steam through a HRSG decreases the efficiency. Compared to a directly coupled SOFC-GT system the SSHS is a significantly more complex system. However, it does not require a pressurized SOFC since the sCO2 Brayton cycle is indirectly coupled
to the SOFC. The most efficient setup of the SSHS, combining the recompression cycle with cathode recirculation, has a higher LHV efficiency than the directly coupled SOFC- GT hybrid system, 66.58% over 62.38%. This setup of the SSHS is rather complex though. Other setups of the SSHS show efficiencies similar to that of the directly coupled SOFC- GT hybrid system.
A promising result, but the practical feasibility of the SSHS is something that should be carefullyconsidered in future research and practice.

Renewable energy is continuously increasing its penetration in the energy supply network around the world. Due to the intermittent nature of renewable energy sources like solar and wind, storage of excess energy during its availability is vital. Energy storage, especially on the large scale, has recently received a lot of attention from the scientific world and ammonia has been identified as a
promising energy storage medium suitable for this application. Factors like high energy density, potential to have minimal carbon footprint and ready existence of suitable infrastructure for handling and transport especially make it an attractive choice. Moreover, ammonia is a bulk feedstock in the chemical and fertiliser industry making it a valuable commodity.
A generic model has been developed in MATLAB to assess the economic feasibility of producing ammonia from varying availability of electric power. The model estimates the optimum plant capacity at which levelised production cost is minimum thereby resulting in minimum energy storage cost. Steel industries like Tata Steel produce electric power to satisfy the plant’s operational
demand using by-product gases (termed as work arising gases) evolved during the steel making process. An intermittent availability of surplus electric power has been reported at Tata Steel, IJmuiden.
The economic feasibility of utilising ammonia to store the surplus available electric power using the developed MATLAB model has been assessed in this study. It has been found that the variable cost due to electric power consumption, the fixed cost of the system and capital cost of the electrolyser
significantly influence the production cost of ammonia. The minimum levelised production cost estimated in this study is €997/ton which is almost three times the current market price of ammonia. The system shows potential to produce ammonia at a competitive price when sufficient electric power is continuously available at an electricity price of €10/MWh or lower. Utilising part of the hydrogen produced from the work arising gases in the ammonia production process helps to lower the levelised production cost to around €913/ton. Availability of sufficient hydrogen simplifies the system and it may be possible to produce ammonia at a competitive price when hydrogen price is lower than €1.26/kg.
The power to ammonia process shows an efficiency of around 50%. Using gas turbines to produce electricity from ammonia are expected to result in roundtrip efficiencies of around 15%-25%. Research and pilot plants have shown good potential of using ammonia as a fuel in combustion engines and commercial applications are expected to be realised in the near future.