As the global community seeks to improve current energy technologies for a sustainable future, offshore PV systems show great potential to overcome the land use limitations of traditional PV systems. There is a complex interaction between different environmental forces at sea with the PV structure. Empirical studies on these environmental interactions can provide critical insights to optimize the design of offshore PV systems. This thesis has identified a gap in wind loading studies on offshore PV designs. The primary objective of this research is to develop a methodological approach for studying the wind-induced tilt variations in floating PV (FPV) systems, with the intent of informing future PV performance assessment frameworks. A numerical modelling approach using the CFD tool ANSYS Fluent is adopted as the base methodology. The first phase of the study employs single-phase wind tunnel models in 2D and 3D to study flow behaviour over the required geometry. The models are validated against literature and used as the basis to construct a multi-phase model to simulate wind flow over a floating body and how it moves in response to the water surface.

The model is used to perform sensitivity studies on wind speed, module orientation, module tilt, and floater height. The simulation results indicate that tilt variations induced by wind flow are minimal, under 5◦, for still water conditions. In addition, it also suggests an increase in wind velocity increases the non-linearity in the rotational response of the body, changes in the direction of rotation depending on the speed of the flow and tilt of the module, and a sharp increase in rotation with an increase in floater height. The highest rotational response of 4.07◦(anticlockwise) was observed for a design tilt of 24◦ and a wind speed of 40 m/s.

Based on the simulation results, a PV yield assessment is done, and it is found that the inclusion of tilt effects changes the yield by less than 0.5%. Given the high computational cost involved, a numerical approach for wind load evaluation is not justified in terms of yield variation. For future work, it is recommended to first conduct experimental studies to verify the effects of wind loading on different FPV system designs. This could be supplemented with numerical approaches in the future using high-performance computational resources.

The transition to renewable energy sources is essential to mitigate the impacts of climate change, with solar energy playing a pivotal role in this shift. Photovoltaic (PV) technology. However, the traditional single-junction cells are reaching their theoretical efficiency, which currently stands at 29.43%. Through the use of tandem solar cells, this efficiency limit can be surpassed. The tandem cell is being researched further to increase the power conversion efficiency (PCE). However, the conventional two-terminal (2T) and four-terminal (4T) tandem configurations face challenges related to current matching and optical losses, respectively.
This project addresses these challenges by focusing on the development and optimization of a three-terminal (3T) perovskite/silicon tandem module. The research aims to enhance the energy yield of 3T module under real-world conditions by developing a comprehensive 3T model within the Photovoltaic Material and Devices (PVMD) Toolbox, bridging the gap between cell-level and module-level optimization, which has been underexplored in existing studies.
The first step involved the development of the 3T model, which incorporates independent connections for each sub-cell and utilizes an interdigitated back contact (IBC) on the bottom cell as the third terminal. The 3T model is developed and simulated in MATLAB to be validated, showing close alignment of IV curves compared to the existing literature. The 3T model is then used to simulate a 72-cell module to be validated with a widely used electrical simulator called LTspice. The validation of the developed MATLAB 3T model against LTSpice simulations demonstrated a close match, with an RMSE result of 0.02% errors, confirming the model's accuracy in predicting the IV curves and energy yield for various operating conditions.
The second phase of the research involved detailed comparisons between the performances of 2T and 3T modules, each consisting of 72 cells, under both standard test conditions (STC) and real-world conditions in Delft as a sample. The simulations revealed that the 3T module provides less annual energy yield than 2T. However, the 3T module performs better than 2T at handling spectral irradiance variations and current mismatch situations under real-world conditions. At a certain hour, 3T outperforms 2T by yielding 220.75 W compared to 219.1 W. The loss analysis confirms that the 3T module produces less mismatch loss under real conditions than the 2T module. The simulations at four different locations also show that 3T has a certain number of times when 3T yields more energy than 2T. This shows the potential of 3T to outperform 2T by optimizing the perovskite bandgap energy and thickness.
The optimization of the 3T module focused on adjusting the perovskite layer's bandgap energy and thickness. The optimal bandgap energy is identified as 1.64 eV, and the ideal thickness is 600 nm for 2T, yielding 588.79 kWh. On the other hand, 3T has optimal perovskite bandgap energy and thickness of 1.82 eV and 600 nm, respectively, yielding lower energy of 583.24 kWh. Then, the modules are expanded into 144-cell modules, which results in 3T consistently yielding around 0.4% to 0.8% more energy at its optimum perovskite bandgap energy and thickness at 4 location samples compared to the 2T. For example, at Delft, the 3T yields more annual energy of 1172 kWh than 2T of 1167 kWh. This is due to the reduced end loss produced by 3T at a larger number of cells in the module. These results show that the 3T outperforms 2T at its respective optimum perovskite bandgap energy and thickness at every location sample and at a larger number of cell modules. Although the current 3T technology with IBC is still expensive, it is expected to become competitively priced in the future. These findings highlight the importance of ongoing optimization and development of 3T modules to fully unlock their potential in various environmental conditions.

The full potential of the Dutch residential solar sector is still untapped, as renters face barriers to the adoption of solar PV systems. These barriers are caused by the mismatch between the PV panel lifespan and the rental contract period of rental properties. This thesis studies the implementation of a product-as-a-service business model for the case of balcony PV systems. By virtue of its flexibility, the business model allows tenants to consider solar energy solutions, hence expanding the residential solar PV market. In addition, the business model applies strategies designed to enhance its circularity, which in turn contributes to enhancing the circularity of the Dutch PV sector. Numerous concepts were developed and evaluated to decide on the winning concept, which consists of a compact, modular PV system that can be easily installed on a wide range of balconies while preserving their aesthetics and offering an optional privacy feature. The business model proved to be profitable for both the company and the end-users, with an Internal Rate of Return (IRR) in the range of 6.1 and 7.6% and cost savings ranging between 12 and 17 €/year. From an environmental perspective, electricity generated under this business model was found to have an 80% lower carbon footprint than the electricity drawn from the grid. Ultimately, this research offers interested stakeholders a blueprint for a novel application of the product-as-a-service business model, that if put into practice can accelerate the adoption of solar PV solutions.

This thesis investigates whether an EEG headset can be used to distinguish motor imagery signals in real time for a Brain Computer Interface (BCI).The specific EEG headset used for this project is the gtec Unicorn Hybrid Black. The aim of this subgroup is to stream the data in real time, preprocess the data, and create a training dataset using recordings from subjects. The sample from the EEG headset is streamed to a laptop using a live data streaming framework called Labstreaminglayer. The data is then filtered using frequency filters and ICA to remove noise and artifacts. Finally, ERDS plots are used to check the signal quality of the recordings. Recordings of sufficient quality should have (de)synchronisation peaks after the prompt is displayed. Before the recordings are made, an experimental setup is set up. This includes prompts with four different movements that the subject is asked to imagine. The data is sent to a GUI to be visualized with various graphs. It is also sent to a machine learning model to classify the movements. It was concluded that the subsystem could successfully stream data from the cap, process the data, and verify the quality of the data. Using ERDS plots, it was verified that some, but not all, MI actions are distinguishable for one individual. However, further verification of other individuals is required to conclude whether this is a systematic problem or is due to the individual.

Passivating contacts in the front-rear contacted c-Si solar cells enhances the device performance by quenching the contact recombination and enabling sufficient carrier transport. Tunneling oxide passi- vating contact (TOPCon) which consists of an interfacial oxide and a poly-SiO𝑥 layer is one of the most promising contact techniques in passivating both surfaces of the silicon wafer. However, the full area poly-SiO𝑥 layer is absorptive when it is applied at the front side which has become an efficiency limiting factor. In this project, an advanced local poly-SiO𝑥 passivating contact architecture is proposed and presented. The local poly-SiO𝑥 passivating contacts, so-called “poly-SiO𝑥 finger”, is deposited through a hard mask at predefined locations which will be only placed underneath the metal contacts. The formation of poly-SiO𝑥 finger and its application in the solar cells are discussed.

First, a silicon wafer hard mask is fabricated by a lithography process followed by a KOH wet chemical etch-back process. Specified openings down to 38.7 𝜇m are established which isolate sections of the substrate for the poly-SiO𝑥 finger formation. P+ doped a-SiO𝑥 :H is deposited using PECVD with SiO𝑥 p+ diffused emitter commercial Cz wafers through the hard mask. By investigating the influence of deposition parameters during the PECVD, specifically the power and pressure, decent uniformity of the finger deposition is achieved. An optimized deposition condition of the doped a-SiO𝑥 :H is established for the poly-SiO𝑥 finger formation: an RF power source at 15 Watt, a chamber pressure of 1.5 mbar, and a substrate temperature of 180 °C. A narrow poly-SiO𝑥 finger with a width of 40.0 𝜇m has been demonstrated.

Second, the passivation properties of the symmetrical samples are examined by varying the poly-SiO𝑥 and Al2O3 thickness for the hole carrier selective contacts. A full area p+ TOPCon and Al2O3 symmetric samples were coated on the textured diffused p+ surface with an n-type c-Si substrate to investigate the process parameters on the passivation properties. The optimal 𝑖𝑉𝑜𝑐 of p+ TOPCon samples is 662 𝑚𝑉 and a corresponding 𝐽0 of 156 𝑓 𝐴 𝑐𝑚2 which is obtained with a poly-SiO𝑥 thickness of 50 nm when annealed at 850 °C. The optimal thickness for the Al2O3 passivation layer is achieved by depositing a 20 nm thick layer followed by FGA, with an 𝑖𝑉𝑜𝑐 of 692 𝑚𝑉 and a 𝐽0 of 22.4 𝑓 𝐴/𝑐𝑚2.

Finally, a process flowchart has been created to fabricate c-Si solar cells with the local p+ TOPCon on the front p+ diffused emitter and a full area n+ TOPCon on the rear side. A localized polished area is made by a poly-etch process for the alignment between the substrate and the pattern in the lithography mask. Using the ascertained parameters during the optimization, NAOS-SiO𝑥 combining with 50 nm-thick doped p+ a-SiO𝑥 :H fingers are applied on the p+ diffused surface and 100 nm-thick n+a-SiO𝑥 :H on the rear side. A annealing step is performed for the crystallization. A 20 nm-thick Al2O3 followed by a 75 nm SiN𝑥 layer are deposited on the front side and 100 nm SiN𝑥 layer is applied on the rear side. Lithography, wet chemical etch-back together with Al/Ag(front/rear) evaporation are utilized for solar cells metallization. The fabricated c-Si solar cells with poly-SiO𝑥 fingers has a champion efficiency with an efficiency of 7.91 %, with a 𝑖𝑉𝑜𝑐 of 562 𝑚𝑉, 𝑖𝑛𝑡 𝐽𝑠𝑐 of 34.7 𝑚𝐴 𝑐𝑚2 and fill factor of 40.5 %. The limited performance originates from the poor passivation in the poly-SiO𝑥 local contact area and severe 𝑖𝑉𝑜𝑐 drop after the metallization process. For further improvement, good performing c-Si solar cells by minimizing the recombination in the poly-SiO𝑥 local fingers contacts area and optimizing metallization steps are expected to be fabricated .

Several promising photovoltaic (PV) concepts are supported by transistors. Along with the growth of PV capacity in the urban environment, issues related to partial shading highlight the interest in more shade-tolerant PV systems. An example of technologies improving a PV module’s energy yield under partial shading is the submodule power optimizer, including a power converter that operates sub-module maximum power point tracking (MPPT). Alternately, reconfigurable PV modules enable dynamic reconfiguration of the solar cells’ interconnections to optimize the energy yield depending on the irradiance distribution. Both technologies make use of transistors as fundamental components. Integrating the latter into the solar cell wafer might be a solution for cost reduction and reliability improvement and thus support such concepts. Moreover, that kind of transistor integration can have applications in solar cell-embedded electronic and digital devices.

In this thesis, a lateral metal-oxide-semiconductor field-effect transistor (MOSFET) and an interdigitated back-contacted (IBC) solar cell are integrated into the same crystalline silicon (c-Si) wafer. A combined process flow is developed to manufacture both components with a minimum number of additional steps compared to single-component manufacturing processes. One criterion for this is a high similarity in the design of the device. Therefore, a tunneling oxide passivated contact (TOPCon) solar cell structure is used, involving polycrystalline silicon (poly-Si) at the device’s backside. Similarly, the MOSFET’s gate is made of a highly doped poy-Si film. Ion implantation is used as a common doping process.

Both solar cells and transistors that were manufactured with the combined process flow are first characterized separately. The highest efficiencies obtained for n-type and p-type solar cells are 20.29% and 20.66%, respectively. This is achieved thanks to multiple combined passivation approaches including TOPCon, wet poly-Si etching, a front-side hydrogenated amorphous silicon (a-Si:H) film, and hydrogenated silicon nitride on both sides of the device. Different MOSFET layouts are explored to make the device able to handle relatively large currents. It is found that introducing several drain-source pairs in parallel is more efficient than increasing the channel width to reduce the on-resistance. The on-resistance is further minimized with a gate length reduction and wet chemical poly-Si etching. As expected, the comparison of PMOS and NMOS (MOSFETs built on n-type and p-type wafers, respectively) shows better on-performance for the latter. A minimum on-resistance value of 1 Ω is then obtained. However, a higher leakage current consistently seems to come along with reduced on-resistance; i.e., higher on-performance is coupled with lower off-performance. Finally, experiments are performed combining both components. Under illumination, the MOSFET exhibits lower off-performance due to the photovoltaic effect. However, this effect does not affect the on-performance of the component. The monolithically connected components exhibit I-V characteristics that depend on the applied MOSFET’s gate potential. In the on-mode, the solar cell maintains more than 95% of the conversion efficiency compared to the efficiency measured with the same solar cell without the transistor. However, a non-zero current is obtained in the off-mode, exhibiting low transistor blocking capability. Nevertheless, the large difference in characteristics obtained between the on- and off-modes proves the feasibility of integrating a solar cell and a transistor on the same substrate with a minimum number of additional processing
steps.

Technological advances, cost reduction, depletion of fossil fuels, environmental concerns, and growing energy demand are expanding photovoltaic solar energy (PV) in more latitudes and locations. A simple and effective procedure to assess the PV potential of a particular region is to analyse its climatic conditions. In general, climatic studies use the K¨oppen-Geiger (KG) climate classification as a reference. However, KG is solely based on temperature and precipitation, resulting in an unsatisfactory scheme for analyses in the PV field, since the most important variable, solar irradiation, is not considered. Thus, in 2019 Ascencio-V´asquez et al. developed a new worldwide classification based on temperature, precipitation, and solar irradiation: the K¨oppen-Geiger-Photovoltaic (KGPV) climate classification. Even though KGPV is a good improvement, it just consists of a simplified version of the KG groups subdivided into four levels of irradiation: low, medium, high, and very high. Hence, the climate parameters are not considered in a combined manner in the sorting process.

In this project, a new worldwide climate classification directly applicable to PV has been developed. Machine Learning proved to be a convenient tool to achieve this objective. First, supervised learning served to identify and assess the climate variables more correlated to the specific energy yield. More specifically, a Linear Regression model was implemented. Subsequently, these variables were used to create the classification by applying k-means, a clustering algorithm. The classification was optimised following a comprehensive qualitative analysis, resulting in a scheme based on seven climate variables and 20 clusters. By contrast, KGPV considers five variables. Even though it contemplates 24 groups at first, half of them are neglected based on a land-surface ratio and population density criterion, resulting in a classification based on 12 clusters. Hence, the methodology proposed in this work enables identifying new relevant regions. Moreover, “Machine Learning driven PV-climate classification” presents a satisfactory correlation with the specific energy yield, except for very low values, where the correlation is minor.

Lastly, the relationship between climate and degradation rate was explored. The complexity and non-linear behaviour of degradation demand an alternative approach. Random Forests was proposed, but it showed poor performance. It is necessary to be able to predict non-linearities and, at the same time, keep a logical mathematical relation between the supervised and clustering algorithms. In this regard, Multivariate Adaptive Regression Spline (MARS) might be a promising option.

 A climate change mitigation strategy seen in the maritime sector is the electrification of berths through implementing shore power installations. The incorporation of grid-connected battery energy storage systems (BESS) into shore power installations, thereby creating hybrid installations, potentially accelerates the implementation of shore power. According to a gap in literature, this research evaluates the potential of various BESS to enhance the economic viability of shore power projects in the portal area in Rotterdam by prioritising consumer energy arbitrage and also trading on the day-ahead market, which is referred to as wholesale energy arbitrage.

This research consists of a techno-economic approach of assessing hybrid installations’ economic viability. First, a literature analysis provided insights in the most suitable BESS types for hybrid installations. Then, evaluation of various shore power projects in the port of Rotterdam resulted in the decision to focus on two impacting berths, namely on the Stena Line (SL) and the Cruise Port (CP) terminal. To assess the economic viability of hybrid installations, two models were designed, namely a BESS costs model and an energy management strategy algorithm. Eventually, the economic viability is evaluated by the net present value, the energy efficiency and effectiveness of the various hybrid installations.

This study reveals that none of the hybrid installations are economically feasible in the way they are examined. Nevertheless, it is indicated that lithium iron phosphate batteries are most suitable to enhance the economic viability of hybrid installations due to a high round-trip efficiency and low system costs. The energy demand of the SL terminal is smaller and more frequent compared to the CP terminal, thereby enhancing the potential of the BESS to cycle more often and to create more revenue. The research includes certain assumptions and uncertainties of which the individual impact on the outcome of the research is analysed. Also, potential scenarios ensuring economic viability are presented.

Silicon heterojunction (SHJ) solar cells are one of the most promising PV technologies nowadays due to high photoconversion efficiencies and low manufacturing costs. However, standard front/back-contacted (FBC) solar cells feature a front metal grid that brings shading to the front side of the devices, which limits the conversion efficiency of solar cells. One solution is to move metal contacts fully to the back by introducing interdigitated-back-contacted (IBC) architecture. In 2018, IBC-SHJ solar cells achieved a photoconversion efficiency of 26.7% holding a record for single-junction c-Si cells. However, the standard fabrication process of IBC solar cells comes with increased complexity and manufacturing costs. The focus of this research is on developing and optimizing a simple and industry-appealing fabrication process for high-efficiency IBC-SHJ solar cells.

The first part of the project investigates the simple processing of IBC-SHJ solar cells featuring tunneling recombination junction (TRJ). The first tunneling IBC devices are fabricated successfully. However, shunting is observed from the J-V curves of fabricated devices, which can be related to the internal shunting of tunneling IBC architecture and high lateral conductivity of p-type nc-Si:H-based blanket layer. Hence, alternative contact stacks are designed for application in the previously developed flowchart with the aim to minimize the lateral conductivity of the blanket layer and keep the fabrication process simple.

The proposed hole collection contact stack is firstly implemented in the front junction (FJ) FBC solar cells. The FJ FBC devices reach Voc of 704 mV and FF of 79.29% . Rear junction (RJ) FBC solar cells are fabricated featuring a novel electron collection contact stack that is developed within this thesis. Voc of 715 mV and FF of 82.24% are obtained in RJ devices. The results of RJ FBC solar cells with a newly developed contact stack show excellent results in terms of FF, making it a promising candidate for further application in IBC devices. The introduction of the optimized device design enabled the successful fabrication of IBC solar cells with the simple process developed for tunneling IBC devices while ensuring no shunting occurs. Fabricated devices represent a proof-of-concept of the novel configuration, providing a promising starting point for future development.

Carrier selective passivating contacts (CSPC) have proven to effectively curtail the recombination losses emerging at directly metallised contacts of crystalline Silicon (c-Si) solar cells. CSPCs enabled using an ultra-thin interfacial tunnel oxide layer (SiOx) capped by a doped polycrystalline Silicon (poly-Si) layer also referred to as Tunnel Oxide Passivating Contacts (TOPCon) have resulted in efficiencies as high as 25.8%. This thesis project addresses the development of oxygen alloyed poly-Si (poly-SiOx) in combination with an interfacial oxide layer grown by dry thermal oxidation. The limited transparency of poly-Si based contacts brought on by high free carrier absorption (FCA) can be mitigated by the use of poly-SiOx based passivating contacts owing to their wider bandgaps which induce stronger band bending.
To begin with, poly-SiOx CSPC were optimised by determining the optimum thermal budgets for tunnel oxide growth and hydrogenation scheme. Tunnel oxide layers grown at 675 ͦC 6 minutes demonstrated very good passivation for p-type polished and n-type textured CSPCs indicated by their implied Voc of 709 mV and 711 mV respectively. For the p-type textured CSPC identified as the primary limiting factor when deploying in c-Si solar cells, a tunnel oxide layer grown at 675 ͦC 3 minutes in conjunction with a two-step annealing scheme showed a crucial enhancement in passivation quality with a final implied Voc of 687 mV.
The single side textured front back contacted (FBC) solar cell fabricated using the optimised p-type polished and n-type textured poly-SiOx CSPC recorded a conversion efficiency of 20.94% on a 4 cm2 screen printed solar cell. The reported efficiency is the maximum that has been attained so far for the configuration that uses a thermally grown tunnel oxide layer with poly-SiOx CSPCs. Effective carrier transport and carrier collection was illustrated by a fill factor (FF) of 79.6%. A Jsc of 37.91 mA/cm2 was recorded for the same. A comparison with a single side textured FBC solar cell that employed a tunnel oxide layer grown by nitric acid oxidation of Silicon (NAOS) revealed a superiority in performance by the thermally grown tunnel oxide layer resulting in better passivation and carrier selectivity.
Lastly, the optimised n-type textured and p-type textured CSPCs were implemented on a double side textured FBC solar cell. The two-step annealing scheme that showed beneficial results for the p-type textured CSPC was implemented within the FBC solar cell, leading to an implied Voc of 698mV post hydrogenation. It is worth mentioning that this is the highest value achieved until now for this novel cell architecture. Implementation of screen printing resulted in a final conversion efficiency of 19.38% on a 4 cm2 solar cell with a FF and Jsc of 77.89% and 37.65 mA/cm2 respectively.

Given the merits of photovoltaic technology (PV), rooftop PV systems are becoming more prevalent in residential and commercial areas. As a result of the growing number of photovoltaic systems connected to low voltage (LV) distribution grids, a significant portion of power flow from photovoltaic arrays to the LV grid, As the PV penetration increases, this effect becomes more severe. This reversal of power flow (from the load side to the grid side) results in a voltage rise problem along the distribution feeder. Such an issue is more pronounced near the point of common coupling (PCC). Overvoltages are not desired as they can damage consumers’ electronic devices, burn the insulation and can trip protective equipment, causing sudden power outages. The principal objective of this study is to achieve 100% PV penetration in a low voltage distribution network while maintaining voltages within the grid constraints by employing numerous voltage control techniques. To conduct PV penetration studies, the European low-voltage distribution benchmark network developed by CIGRE is selected. PV systems of various configurations are designed and integrated into the CIGRE LV network. The results of the PV penetration analysis on the CIGRE network suggest that with the increase in the distance between the source and the load, the penetration level decreases drastically. The worst-case network model in which the penetration level is reduced to 65% is selected for employing voltage control strategies. Two main strategies have been used to improve PV penetration. In the first category of methods, the reactive power is controlled by the PV system so that voltages at the PCCs are within the grid voltage limits. Four different reactive power control methods are employed. The second category of methods are based on active power control, in which the voltages are controlled by batteries/electrolyzers by absorbing excess power generated by the PV system, avoiding reverse power flow into the grid. The results obtained reveal that all the techniques employed are successful at increasing PV penetration to 100% without violating grid voltage limits. However, it is concluded that, batteries/electrolyzer systems provide better value in terms of effectiveness in solving the voltage rise issue. They also offers lower losses, and multiple-use cases.

To further improve the light management and optical performance of solar cells, research into nano-textured interfaces has led to a need for a fast and accurate wave optics model. Currently, within the PVMD group at the TU Delft an optical solar cell simulation tool, GenPro4, is being developed to allow for the quick optimization and analysis of solar cell designs. However, the implemented wave optics model has limited accuracy and thus an alternative model is sought.

In this thesis, we researched several rigorous wave optics simulation methods such as: finite element method, finite difference time domain, transfer matrix method, and rigorous coupled wave analysis. Based on three decision criteria (speed, accuracy, and compatibility) the choice of implementing rigorous coupled wave analysis (RCWA) was made. Besides the standard RCWA formulations, a few improvements were made. S-matrices were used to increase
speed and memory efficiency of the program. Furthermore, calculation of the local E-field allowed for the determination of absorption per material in our cell. Lastly, an angular intensity distribution, known as scatter matrix, was produced as output to allow for the full integration with GenPro4.

We validated our new model by comparing results of a nano-textured GICS solar cell with previously conducted finite element method (FEM) simulations. Over a large wavelength range our model showed good agreement with the FEM data. However, slight inaccuracies were observed at longer wavelengths (>1000 nm) as simulation of the metal back reflector became infeasible. Highly absorbing materials, such as metals, potentially required several hundred Fourier modes to be modeled accurately. However, simulations with such a high number of Fourier modes is not feasible as the computer resources (RAM) and computational time
needed grow exponentially. Furthermore, for very small textures, RCWA converges with the GenPro4 flat model as is expected for sufficiently small textures.

Nevertheless, integration of RCWA with GenPro4 was achieved. To demonstrate the ability to quickly and easily simulate real work cell designs, a case study of a perovskite/silicon tandem cell was conducted. In the case study, a combination of 16 interface mythologies was simulated and compared. With the optimal combination showing a potential improvement of 2% over the reference cell.

The use of renewable energies has been growing in a considerable way in the world. Until 2017, 18% of European Union’s total installed power generation capacity was wind power capacity. The level of grid penetration of wind turbines has also increased significantly in the Netherlands. This high level of penetration of wind energy affects the behavior of the system during an event (such as a short circuit), which is not the same that with only conventional generation in the system. The level of detail in the dynamic network model of a transmission system becomes of great importance when a big amount of wind energy is connected to the electrical system. In the current dynamic model of the Netherlands transmission system, negative load is used to represent wind turbines, however, this could be no longer sufficient if more wind turbines are connected to the grid.
The purpose of this Master Thesis Project is the study and analysis of voltage response of wind turbines models based on the IEC 61400-27-1 standard and the WECCWind Plant DynamicModeling Guidelines, both of them currently implemented in several softwares.
This project proposes a modelling methodology for distributed wind turbines, using a single turbine representation and a combined model instead of a negative load directly connected to the grid.
PowerFactory and PSSE softwares are used for the modelling of wind turbines, allowing to compare the models based on the IEC standard and the models based on the WECC guidelines respectively.
For the simulations performed in these two softwares, parameters suitable for comparing both of them are proposed. Besides, an analysis on the differences between both models is provided.
The parameters proposed are used later on for the modelling of distributed wind turbines in the grid.
The methodology for the modelling of distributed wind turbines was proposed and analysed using a region in the Netherlands as case of study and the PSSE software (widely used by transmission system operators) with the generic parameters proposed in the previous analysis.
The proposed methodology and parameters show a more realistic behavior of the wind turbines compared to the use of a negative load. It also provides a grouping proposal depending on the types of distributed wind turbines connected to the grid. In some cases, when the wind energy connected to the system has low impact, the use of a detailed model instead of a negative load is not very representative. Therefore, this project proposes a calculation for the impact that wind energy has in each substation, making easier to decide what is the most suitable level of modelling detail.

Multi-junction solar cells with Si alloys have true potential for high conversion efficiency, because of the spectrum splitting capability. For optimal spectral utilization, a multi-junction silicon based device needs a silicon alloy with a bandgap between that of nc-Si (1.1 eV) and a-Si (1.8 eV). a-SiGe:H has a tunable bandgap between 1.4-1.6 eV by varying the GeH4 flow rate in the layer. An investigation of deposition parameters on PECVD processed a-SiGe:H films showed that variation of the GeH4/SiH4 flow rate is the most influential deposition parameter to achieve bandgap tuning. It influences the optical-, electrical- and material properties due to the fact that it directly changes the GeH4 flow rate in the material. Subsequently, a n-i-p substrate single junction a-SiGe:H solar cell is fabricated. This is the reversed p-i-n superstrate a-SiGe:H solar cell, fabricated by the PVMD group. It has a Voc of 508 mV, a FF of 0.39, a Jsc of 9.9 mA/cm2 and a final efficiency of 2.9%. Due to the low performance, manipulation techniques were introduced. The different proposed shapes consist of bandgap grading in the absorber through GeH4 flow rate profiling. A study on buffer type and thickness, different profiling schemes, grading widths and total absorber thickness strongly improved the device performance. The overall champion single junction a-SiGe:H solar cell has a 3.2 nm n/i i-a-Si buffer combined with a 5 nm n/i i-a-SiGe:H buffer, a V-shape GeH4 peak flow rate of 2.4 sccm, a 134 nm n/i grading width, a 36 nm i/p grading width and a total absorber thickness of 170 nm. This cell generates a Voc of 735 mV, a FF of 0.64, a Jsc of 13.23 mA/cm2 and a final efficiency of 6.18%. This is a relative increase of 113.8% in efficiency. The single junction solar cell fabrication is followed by demonstration of a two-junction device. The overall champion tandem solar cell consists of a 200 nm a-Si:H top cell and a 170 nm a-SiGe:H bottom cell with a V-shape GeH4 peak flow rate of 5.3 sccm. This champion tandem solar cell generates a Voc of 1395 mV, a FF of 0.69, a current limiting Jsc of 8.34 mA/cm2 and a final efficiency of 7.99%. Finally, research proved that the change in top and bottom cell thickness, the maximum GeH4 flow rate and the U- and V-shape profiles are interesting manipulation techniques in a multi-junction device due to their flexibility to increase the current limiting Jsc and improve current matching.

Photovoltaic (PV) system yield prediction models are an important topic in the field of PV solar energy. An accurate prediction model could not only be used for optimising the PV system design, but is also expected to realise the yield potential of innovative PV technologies. In the next generation of PV technologies, one of the most promising concepts is the tandem solar cells. In recent years, these cells have impressed the solar industry by their rapid growth of the maximum power conversion efficiency (PCE). Since tandem solar cells are still at the lab phase, their yield potential under realistic conditions are an interesting field of study as well. However, the existing yield prediction models are not yet available for these tandem cells. In order to fill this gap, a prediction model developed in the Photovoltaic Materials and Devices (PVMD) group of TU Delft, called the PVMD Toolbox, has been adapted to be compatible with the tandem solar cells. In this thesis project, the version 3 of the Toolbox was developed. First the PVMD Toolbox was improved. Except monofacial c-Si cells and bifacial c-Si cell, it is now also available for tandem cells. One of the most promising tandem concepts, the perovskite/c-Si tandem, was taken as a reference tandem configuration integrated in the Toolbox. The Toolbox was also modified to take the influence of solar spectra into consideration and analyses cell performances individually. Secondly, the accuracy of the Toolbox was validated. A new figure of merit called 'relative total deviation' is put forward in this report, which calculates the ratio between the sum of deviations that each simulation introduces, and the total measured energy yield. When the electrical parameters were taken from the own measurements, the relative total deviation of simulation results was only 8.6%. Finally, the Toolbox was applied to two case studies. In the first study, it was found that the annual energy yield (AEY) of perovskite tandems can be increased up to 0.4% by optimising perovskite thickness for a certain location. The second case study compared the AEY of the tandem module and conventional c-Si module. Perovskite tandem module showed a high AEY, around 36% higher than that of the c-Si module. However, perovskite tandem had a lower specific yield as they are more sensitive to the spectral variation

The transportation industry is causing 14% of the worldwide greenhouse gas emission. Therefore, the United Nation concluded with the Paris climate agreement to reduce and limit their emissions to keep the global average temperature increase below 2 degrees Celsius. Based on the agreement the European union introduced new regulations to limit the average fleet emission of car companies. In this push towards lowering emission the companies introduced their first generations of electric cars. To further improve the efficiency of the electric drive train new multilevel topologies were introduced. One of the topologies is called modular multilevel converter (MMC) introduced by R. Marquardt and A. Llesnicar in 2003. This new topology main advantage are its modularity and the option to use low voltage component. However, no company industrialized the MMC for drive train application. The reason therefore are the extensive control architecture, hardware and software wise. This thesis investigated possible ways to reduce the wiring and complexity by introducing a low level communication bus together with distributing the control to remove the centralized architecture. Therefore, the different possible low level communication bus were analysed and compared. The different bus protocols were compared based on speed and time to send the same amount of information to control a MMC. It was concluded that the serial peripheral interface bus (SPI) shows the highest capability for the proposed single phase 5 level converter set-up. Therefore, an experimental system was built to validate the performance. The system itself was designed with the goal to use low cost and low voltage component. The validation of the experimental set-up showed the stable operation of the system with an open loop control. Thereby it proofs the possibility to integrate and control the MMC with a low level communication bus. The results can be used as a baseline to further research on integrating theMMC and make it viable for drive train applications.

With the rapidly advancing technology in the field of concentrator photovoltaics for terrestrial applications, the aerospace industry is eager to innovate and incorporate this idea. Concentrated solar light offers a cheaper but more complex solution to extract more power without increasing the number of solar cells. For extraterrestrial applications generally the photovoltaic elements account for nearly half of the costs on solar array, this decreasing the number of solar cells significantly contributes to lowering the cost of electric power in space.

The solar array studied in this thesis provides a technologically innovative solution to reduce the cost of electrical energy for LEO satellites, in particular, to suit, for instance, the OneWeb satellite constellation mission at 1200 km altitude. Apart from being a structurally challenging design, another very important consideration is thermal feasibility. Concentrated solar light introduces hot spots of high temperatures, and heat dissipation at those locations is crucial. Hence, this thesis focuses on investigating the thermal performance of ConCur baseline design in orbit using thermal software ESATAN, and optimizing the design according to the thermal requirements, as well as performing electrical power calculations.

To broaden the knowledge regarding concentrator photovoltaics on Earth and in outer space, a literature study was first performed and the main findings are summarized in this document. Also, heat transfer in space is briefly explained as part of the methodology for modelling the solar panel in ESATAN, including a step-by-step guide. After modelling the panel it was put into the Low Earth Orbit simulated by ESATAN which provide outputs on temperature and absorbed flux results. The panel was optimized and it was found that the maximum cell temperature reaches +122 degrees C when nonoperational, and +70 degrees C when producing electrical energy. These and more results were post-processed and summarized and relevant conclusions were drawn. Knowing the panel temperature in orbit and slightly altering its dimensions, the amount of electrical power produced was calculated to match the required 300 W. Also a schematic of the hardware was made and the most probably cell layout designed. In addition, this report includes a brief cost estimation and comparison to the conventional solar panel of the same dimensions and that is capable of producing the same amount of power. It was estimated that the electrical power by ConCur would cost around 112 Euro/Watt which is 10 times less than conventional solar array. Finally, relevant recommendations are listed for further increasing the technology readiness level (TRL) of the concept.

Efficiency improvements of solar cells, growth in photovoltaic cells manufacturing, and declining prices of solar modules are just a few of the factors that have allowed solar power to break records (320 GW) in global cumulative installed capacity in 2016. In the energy systems of the future, solar energy will be the predominant energy source. However, the growth in solar power brings new technical challenges to overcome.
Power intermittency, grid flexibility, and surplus electricity are just a few of the challenges that must be addressed for the power systems of the future.
In the light of these challenges, this thesis provides new insights in the use of solar energy to produce hydrogen via a PEM electrolyzer. In order to achieve this goal, a hybrid power system model of hydrogen production using solar power was developed. The system consists of a PV array, a battery bank, a PEM electrolyzer, hydrogen tank, and a power control unit.
The results are structured in two parts. First, simulations of three configurations between the panel and the electrolyzer: (i) direct coupling, (ii) including an MPPT, and (iii) including a battery. Second, simulations of several component sizes of PV modules, battery bank, and electrolyzer stack. These simulations were analyzed for yearly irradiance data from Delft.
An analysis of energy yields, hydrogen production, system efficiency, and the impact on the electrolyzer lifetime, is performed for each of the configurations.
Additionally, Wawa, a lab-scale solar-to-hydrogen system has been designed, built and tested. Wawa provides a practical hands-on understanding the hydrogen production via PEM electrolysis using solar power.
Based on the simulation results, it is clear that the lifetime of the electrolyzer can be positively affected by including a battery as an energy buffer. An additional conclusion is that the shape of the irradiance curve plays an important role when sizing the components of the system.
Hopefully, this research will motivate students to address more research on how solar-to-hydrogen systems can help to develop the power systems of the future.

In the transition towards a renewable based energy supply, one of the main challenges is the intermittent nature of most renewable energy sources. In order to ensure a stable energy supply, different storage technologies attract a lot of research attention. For long term storage, using hydrogen as artificial fuel is a promising option. However, in order for hydrogen storage to be renewable, the hydrogen must be produced using renewable energy. A possible option is to use solar energy to drive the electrolysis of water. In this way, hydrogen is produced directly from sunlight by driving the redox reaction with a reversible potential of 1.23 V. However, due to overpotentials and possible losses a voltage of 1.6-2 V is needed form the used device to drive the reaction. Recently, a wafer based triple junction silicon solar cell was proposed to generate the voltage needed to drive the water splitting reaction. The cell uses an n-type crystalline silicon wafer as substrate, and has an a-Si/nc-Si/c-Si structure. Although this cell demonstrates the feasibility of this technology, the performance is not good enough yet to drive the water splitting reaction efficiently.
In this work, several ways to optimize the triple junction solar cell have been studied. First, optimising the tunnel recombination junctions improves the open circuit voltage of the device. For the tunnel recombination junction between the top a-Si and the middle nc-Si cell, this is done by using a combination of a thin n-SiOx layer and a thin n-a-Si layer. Apart from a small improvement in optical performance this configuration improves the conductivity of the junction and also slightly enhances charge separation and collection in both sub-cells. For the junction between the middle nc-Si and the bottom c-Si cell, the same result was achieved by increasing the doping in the n-layer. Subsequently, to improve current matching of the device, the nc-Si layer thickness can be increased to 3500 nm without sacrificing the electrical performance. In addition, optimizing the interface between the top p-nc-SiOx layer and the front transparent conductive oxide (TCO) also improves the electrical performance of the device. Moreover, it was found that using hydrogenated indium oxide as front TCO instead of indium doped tin oxide increases the current by decreasing the reflection in the wavelength region of the current limiting nc-Si middle cell by having reflection, and also increases the open circuit voltage of the device by 0.3 Volts. The final triple junction cell achieved an open circuit voltage of 1.93 V and a short circuit current density of 8.5 mA/cm2, with a fill factor of 0.65. With these improvements, it is estimated that a solar to hydrogen efficiency of 6.2 % can be reached by using an IrOx counter electrode.