This work investigates whether a power amplifier (PA) designed for a lower operating frequency (10GHz) can be effectively implemented using a process that has a 𝑓𝑚𝑎𝑥 of well above 100 GHz. Operating a process far below its maximum frequency offers potential benefits in gain and efficiency, but also presents challenges. Particularly for the stability of the amplifier, which becomes increasingly critical at high gain levels.

To investegate the potential for such an RF power amplifier, Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) are used. This is a technology that forms the current State-of-Art for microwave high-power high-efficiency MMICs. The circuit is fabricated using WIN Semiconductors NP12-01 GaN-on-SiC technology with 0.12 𝜇m gates. They offer a technology with one of the shortest gatelengths that are around in the industry.

First a Programme of Requirements was established, before starting the design and four Key Per-formance Indicators (power, efficiency, stability and size) were defined. A design process was followed that started with transistor measurements, after which an architectural design was made, followed by schematic implementation, electromagnetic (EM) modelling and final layout creation. Continuous refinement between schematic, EM and layout stages where necessary to avoid excessive simulation times. After design rule verification and stability checks, the circuit was submitted for fabrication, with MMIC samples received back approximately four months later, after which, an extensive characterization of MMICs was performed, through both small-signal as well as non-linear measurements.

All this work resulted in the following KPI’s:
• For the power, a peak power of over 38 dBm was realized under dedicated measurement conditions and over 35 dBm for nominal measurement conditions (20 V 𝑉𝐷𝑆) and a bandwidth of more than
2 GHz (-1 dB bandwidth) or 3 GHz (3-dB bandwidth) was obtained.
• For the PAE, 35% was nominally achieved over various bias points and frequencies.
• Unconditional stability was achieved.
• The size of the amplifier was 2x1.75 mm2, resulting in slightly below 2 W/mm.

While amplifiers with higher absolute power at X-band exist, the NP12 process is unlikely to surpass the state-of-the-art in this regard due to its limited maximum drain voltage, which constrains the achievable output power. However, the measured efficiency and gain are promising for a first design iteration. Notably, the implementation of the stability analysis for this power amplifier took a significant effort, but was proved highly effective as no instability was observed at all during the measurements. Two variations of the amplifier were implemented to investigate the possibility of reusing the source via-hole for two adjacent output stage transistors. This variation, with re-used via-holes, worked similar to the baseline design, but exhibited a lower PAE.

In conclusion, the expectation is strengthened that the advantages of a mm-wave process used at X-band frequencies can pay off in a modest increase of the efficiency and a significantly increased gain. Finally, the work resulted in one conference publication, and two tutorial documents for future students (an AWR student guide and MMIC mounting tutorial).

In this paper, a batch-based industrial load model is used to model the energy system of a hydrogen-based steel plant. It is formulated in Gorubi as a profit-maximizing Mixed Integer Linear Programming (MILP) problem. The addition of H2 units to the steel plant introduces new operational aspects in steel production. This requires energy efficiency constraints to optimizematerial usage, consideringwarm-up time for specific units, and exploring the impact of a fuel cell system with the plant. The existing industrial load model is modified and new constraints are added to obtain flexible behavior, where units have the choice to consume electricity as part of their normal operation or sell the electricity back to the market. 40 scenarios are generated to optimally manage the energy consumption of the plant. Sensitivity analysis reveals that a fuel cell has a low impact on profit in low price periods, hydrogen storage is essential to overcome losses for the assumed average price , and flexible operation achieves the highest profit when encountered with a peak price. After obtaining the energy consumption of the units, they are modeled as loads in Pandapower assuming the worst-case scenario. Then, a time-series load flow analysis is carried out to validate the rating of the main transformer for the radial network. Finally, the peak active and reactive power of the plant is modeled as a static load in a representative European high voltage grid, where load flow reveals that bus voltages and line loadings depend on the location of the plant in the system.

Floating Photovoltaic (PV) system is an emerging and rapidly developing solar PV application that utilizes water surfaces, such as reservoirs and lakes, as the installation grounds for the PV arrays and its balance of systems. In addition to becoming a solution to land scarcity issues of solar PV installation, floating PV systems also benefit from an improved thermal performance due to its proximity to water that results in a cooling effect for the PV modules. However, the extent of this cooling effect is not yet well-understood and established. Conventional thermal modelling tools and approaches, which are mostly validated for land-based PV systems, might not be directly applicable to floating PV systems without proper adaptation. This research aims to improve the accuracy of temperature and energy yield predictions for floating PV systems by evaluating and updating physics-based thermal models based on both analytical and computational methods. This study is driven by several research questions, which includes the analysis on how do existing thermal models perform in predicting floating PV module temperatures, how can Computational Fluid Dynamics (CFD) simulations be used to improve thermal models accuracy for floating PV applications, and how does the improvement in thermal model accuracy impact energy yield estimation in PV system energy yield simulation tools.

Chapter 2 conducts an evaluation of two analytical thermal modelling approaches for predicting floating PV module temperature, which are the Fuentes Model and the Resistive Thermal Model. Results show that while both models reasonably capture the PV module temperature trends, they tend to under-predict water-induced cooling effect that is present in floating PV environments, which results in a overestimation of PV module temperatures in general. Even though the Resistive Thermal Model results in a slightly higher accuracy compared to the Fuentes Model, a notable Root Mean Square Error (RMSE) is still observed with respect to measured values. This discrepancy highlights the need to improve the thermal dynamics representation, especially in capturing the effect of water proximity and the modified convective heat transfer interactions unique to floating PV systems. Chapter 3 implements CFD as a refinement tool for the analytical thermal modelling, with the goal of combining CFD's ability to capture detailed solid-fluid interactions and the computational cost effectiveness of the Resistive Thermal Model. The CFD-Updated Resistive Thermal Model is compared against measured data and shows a substantial RMSE reduction, with an RMSE of 0.72oC, significantly lower than the RMSE of the initial Resistive Thermal Model (1.70oC) and the Fuentes Model (2.30oC). Chapter 4 analyses how the improved thermal models affect energy yield prediction by using two simulation tools PVsyst and the PVMD Toolbox. The energy yield results show that the CFD-updated Resistive Thermal Model achieves the closest match to the measured specific energy yield, with an error of just 0.10%, compared to 1.75% and 1.27% error values for the Fuentes FD Model and the initial Resistive Thermal Model, respectively. These results clearly show that the increase in thermal model accuracy is directly related to a higher accuracy in energy yield simulation, where the energy yield simulation based on the improved thermal model results in a very close agreement with measured values. Chapter 5 focuses analysing how does practical installation scenario, specifically differing PV array row spacing, affect the thermal dynamics of floating PV systems. The results demonstrate that while close-proximity PV arrays with small row-spacing may offer higher power density per unit area, it comes at the cost of increased PV module temperatures and potentially reduced energy yield. On the contrary, large-proximity PV arrays with large row-spacing results in a lower overall PV module temperatures that potentially increase energy yield of the floating PV system.

In conclusion, this study demonstrates the important role of thermal modelling in improving floating PV performance prediction for floating PV systems. The integration of CFD-derived parameters into Resistive Thermal Model leads to significantly improved accuracy in temperature and energy yield predictions. However, the findings are based on limited real-world measurement data and a single floating PV archetype. A more extensive validation across more configurations and climates, as well as the development of generalized Nusselt number correlations for diverse floating PV archetypes are recommended for future works.

This master’s thesis investigates the feasibility of retrofilling existing L-SEP Gas Insulated Switchgear (GIS). This is motivated by the European F-Gas regulations phasing out the usage of Sulphur Hexafluoride (𝑆𝐹6) due to its large Global Warming Potential (GWP). Retrofilling the L-SEP GIS with a dielectrically weaker insulation gas is a two-pronged problem. One side is on a component level, where the physical required alterations are investigated to obtain a new withstand voltage based upon alternative insulation gas. The other side is a system based study, where the grid of Stedin is examined on what transient overvoltages can occur. The latter part is the focus of this thesis and is important as some locations might stress the L-SEP to its rated maximum withstand voltage, not allow for retrofill. The research methodology involves devolvement and investigation of the key transient origin applicable to the Stedin grid by usage of the ATP-EMTP software. An analysis of transient origins identified fault clearing as the highest priority for investigation. Key components (such as cables and transformers) were identified and represented using frequency dependent models such as the ULM and BCTRAN Grey box model. Both of which were tuned and validated using theory, measurement data and datasheets. A sensitivity analysis was then performed for differing fault locations and component parameters to identify the primary drivers of the maximum transient overvoltages. The results show that the magnitude of the overvoltages are governed by grid earthing configuration and total shunt capacitance on the source side of the breaker. Non effectively earthed systems consistently produce higher overvoltages due to a large pole clearing factor. Furthermore, larger parallel capacitance reduces circuit damping which increases the contribution of the oscillatory part to the overvoltage. The highest simulated transient overvoltage was simulated to be a phase to phase overvoltage. In the case of a non effectively earthed systems with very low damping, where the oscillations of different phases align in opposition. This study concludes that the worst case transient overvoltages remain well below the L-SEPs (rated at 72.5kV) rated lightning withstand voltage of 325kVp for 𝑆𝐹6. This implies that the possibility of retrofilling the GIS with weaker insulation gas (which lowers the withstand voltage) might be possible. In order for this to be confirmed, tests must be done on the altered GIS to find the new withstand voltage for the alternative gas. To improve the grid overvoltages remedial actions can be taken such as improving grid earthing and strategic installation of surge arresters.

Throughout the development of crystalline-silicon/perovskite tandem solar cells, the degradation rate of the perovskite top cells has become a limiting parameter. Currently, perovskite faces stability issues, mainly caused by corrosion and the light-soaking effect. This work investigates the degradation rate of the perovskite top cell, where a model is created to determine the parameters from the single diode model that change the IV-curve of a solar cell and lifetime energy yield simulations were performed to find the maximum tolerable degradation rate of perovskite in a tandem module to obtain a higher energy yield compared to a single-junction module Using experimental data from the King Abdullah University of Science and Technology (KAUST), where the external parameters from the measurements were provided, the changes over time in the ideality factor, saturation current, shunt resistance, and series resistance were estimated, using a numerical model. Linear trend lines through the fitting parameters over time were used and lifetime energy yield simulations were performed. For these simulations, a crystalline-silicon/perovskite tandem cell with an efficiency of 31.1% was compared to to a single-junction cell with an efficiency of 23.9%, where the single-junction cell’s optics are the same as the tandem cell’s bottom cell. To perform lifetime energy yield simulations, the PVMD toolbox is used.
Simulating the lifetime energy yield over 10 years, a perovskite degradation rate of 27.5%/year was found using the electrical parameters under STC, where the power output decreased from 4.95W to 0.24W per cell. Comparing 2T and 4T configurations, where the cell optics were kept the same, degradation rates of 21.2%/year and 9.5%/year were found for 2T and 4T, respectively. Looking at different geographical locations, degradation rates of 19%, 20%, 20.6% and 21.2% per year were found for Delft, Lagos, Lisbon and Shanghai, respectively. These differences were caused by current mismatch between the top and bottom cell, where the highest mismatch of 0.55 mA/cm2 was found in Shanghai.
To determine the maximum tolerable degradation rate of the perovskite top cell resulting in a higher lifetime energy yield for a tandem module compared to a single-junction module over 25 years, various degradation rates were analyzed. The perovskite degradation rate must be lower than 1.5%/year and 3.1%/year for 2T and 4T configurations, respectively, assuming no degradation in the silicon single-junction cell and the tandem cell’s bottom cell.

Renewable energy sources, such as thin-film silicon solar cells, show a lot of potential as the technology promises low production temperatures, low cost and low material usage. Other benefits are the flexible and very lightweight modules that can be fabricated, which enable a wide variety of applications. Other benefits include the low-temperature coefficient and low toxicity of the materials used to create thin-film silicon solar cells. The downside of using thin-film silicon modules is the relatively low power conversion efficiency inherent to the amorphous and nanocrystalline silicon. Another downside of amorphous silicon solar cells is their significant initial degradation, known as the Staebler-Wronski effect. This initial degradation will stabilize after time but does limit the ultimate conversion efficiency, especially for single-junction devices.
Hydrogenated amorphous silicon (a-Si:H) and nano-crystalline silicon (nc-Si:H) solar cells can be added in series to form a tandem device, thus increasing the efficiency of thin-film silicon solar cells. Although the current will be limited for 2-terminal tandem devices, a significant increase in open circuit voltage can be achieved resulting in higher efficiencies. To achieve highly efficient thin-film silicon solar cells a combination of good optical, electrical and material properties need to be combined. Extensive research has been done to achieve such high-efficiency devices focussed on the silicon deposition conditions, glass texturing for effective light scattering and light incoupling through anti-reflection coatings. Further research is focused on Transparent Conductive Oxides (TCO) improvements and the creation of triple or quadruple junctions.
Firstly, this thesis will focus on a literature study on amorphous silicon with a high-energy bandgap, deposition conditions in PECVD chambers and an i-SiOx buffer layer. A top cell of amorphous silicon with a high-energy bandgap can improve the conversion efficiency of a-Si:H/nc-Si:H solar cells by increasing its overall V oc. The amorphous silicon is processed at high pressure (3-9mbar) and high power densities (150-400mW /cm2) in a VHF-PECVD chamber at 40.68M Hz. To improve the poor blue response of these solar cells, a buffer layer of i-SiOx is explored as such a buffer layer has proven itself under normal deposition power densities (28mW /cm2) and pressure (0.7mbar).The i-SiOx did not prove to be effective in improving the blue response. A narrow range of deposition conditions around 5mbar and 25W is found to give high-bandgap energy solar cells with a good blue response.
Secondly, literature findings on a bilayer TCO configuration of IOH (Hydrogenated Indium Oxide) and i-ZnO (intrinsic Zinc-Oxide) to improve nc-Si:H single junction solar cells are provided. Prior studies on the use of a back reflector made out of different ZnO(Zinc-Oxides) are presented. Findings in literature on micro and nano-textured glass are presented and a comparison is made in an experiment to justify the use of a specific texture. Further experiments are carried out to measure the effect of implementing the bilayer TCO and an i-ZnO back reflector and an experiment on the performance and reproducibility of a-Si on MST (modulated surface textured) glass substrates is performed. ITO textured glass is chosen as the best performing substrate and a thick 1μ i-ZnO layer as part of a bilayer TCO is shown to be most effective at light scattering. The i-ZnO as part of a bilayer TCO can also significantly improve the spectral response of a-Si:H solar cell on MST textured glass. Furthermore, the i-ZnO as a back reflector is shown to be more effective when its thickness is increased.
Thirdly, a study is performed on the functioning of the a-Si:H/nc-Si:H tandem cells with respect to the thickness of the p-layer in the tunnel recombination junction (TRJ). An experiment is carried out to improve the reproducibility of a-Si:H/nc-Si:H solar cells by increasing the hickness of p-layer in the TRJ.
The conclusion is made that the glass texturing is more influential than the thickness of the p-layer in this experiment. Further investigation of the p-layer at the front interface of the device is done by an experiment on both MST and Asahi substrates. It is shown that thicker front players do not improve the reproducibility of tandem solar cells, but a trend of more parasitic absorption is seen. Finally, a study on micro and nano-textured glass for a-Si:H/nc-Si:H solar cells is shown. The chosen ITO substrate is finally chosen to demonstrate the progress of ongoing research on the performance of a-Si:H/nc-Si:H solar cells. The bilayer TCO vs a single layer TCO is used in combination with and without a SiNx ARC.
The electrical performance of the solar cells deposited in the final experiment is likely limited by poor IOH depositions and a large contribution of parasitic absorption is shown for the samples with the SiNx ARC. Either interaction of SiNx with the IOH or a poor IOH deposition are the most likely causes. Good 1-R curves are obtained for the solar cells on ITO textured glass substrates, especially the sample with the bilayer TCO and SiNx ARC.

This thesis explores the development of mobile charging systems, which could significantly ease the challenges associated with current electric vehicle charging methods. The purpose of this thesis is to develop an autonomous system to fulfil estimated charging demand on a typical day under different conditions to exemplify how mobile charging systems can address these issues.

The research is mainly motivated by the limitations of conventional charging poles, such as their scarcity, lengthy charging times, unregulated demand, and urban space conflicts as EV usage grows. Future EV statistics and charging station projections are presented underscoring how these challenges can be amplified shortly. As an alternative solution, mobile systems are introduced highlighting products, prototypes, and studies in the market and literature. Through stakeholder analysis, these systems are shown to benefit investors, consumers, and the public, supporting the grid, facilitating convenient charging.

The thesis incorporates a charging demand estimation algorithm to simulate the charging tasks on a typical day. This demand estimation is represented as private, public, and workspace charging load, sampled by considering the probability of energy demand and connection times. Next, the study integrates an iterative optimization process to simulate how effectively this demand can be addressed by a robot-like mobile charging system.

The system is simulated with different price scenarios, grid capacity values of 50 and 100 kW, varying the number of units between 3 and 5, and battery sizes between 70 and 400 kWh. As a result, it is demonstrated that mobile charging systems can effectively reduce peak demand by decoupling charging load from the grid while offering more convenient charging experience. The profitability is assessed through energy arbitrage, operational revenues, and energy costs, noting improvements with seasonal effects and higher grid capacity.

The results show that the switchable battery configuration can effectively minimise the required investment costs because of the smaller number of necessary carrier units mobilising the battery units. A switchable battery setup with 3x270 kWh batteries and 2 carriers is identified as cost-effective for public and workplace demand, with a potential increase to 340 kWh for higher returns despite 20% more investment. The sizing process is reiterated for another demand scenario consisting of a private charging load and 260 kWh capacity is highlighted as a cost-effective choice, while the profits can be improved with 310 kWh capacity.

The thesis further discusses the mobility necessities of the system and the performance requirements of the powertrain. To maintain grounding, the study simulates the parking service area of P1 at the TU Delft campus. A driving cycle is developed by taking site measurements and also considering safety concerns and standards. Consequently, energy consumption and maximum power requirement are calculated by also integrating a weight estimation methodology regarding the main components of the system.

Lastly, the thesis introduces different power converter topologies that can act as a bridge between the system and EVs. As a consequence of a comprehensive analysis of different converters and the findings reported in the literature, various topologies are suggested to be used in different cases.