Interest in incorporating renewable energy systems into current infrastructure has surged as a result of the growing need for sustainable energy solutions in urban settings. This thesis investigates the optimization of a heating and cooling system designed for residential and commercial buildings, with a focus on Dutch climate conditions. The system consists of photovoltaic thermal (PVT) collectors, aquifer thermal energy storage (ATES), heat exchanger and heat pumps. By using these technologies, buildings will be able to satisfy energy demand sustainably without the need for fossil fuels.

Through dynamic simulations, the research aims to optimize the energy system's performance while taking into account a range of operational scenarios and parameter values. Critical components, including the ATES and PVT collectors, are modeled to evaluate their working and performance with heat pumps to provide heating and with heat exchanger for cooling.

The Photovoltaic Materials and Devices research group at TU Delft uses the PVMD Toolbox, a sophisticated modeling tool. Few models from the toolbox are utilised in developing an integrated model, which is later implemented in the toolbox. Later on, it is optimized to improve its effectiveness through dynamic sizing of collectors and aquifers, and implementation of operational modes, making overall the integrated system more robust and redundant. The performance of the integrated system is then studied for a base scenario with 10 PVT collectors and 27,000 m^3 aquifer volume for the current scenario. It showcases promising results. To assess its applicability, the system is analysed under various scenarios. The first scenario is a season-wise performance assessment, where it is showcased that PVT produce energy during summer months and the rest of the year there is a consistent performance by ATES. On comparing the performance of different insulation levels of the buildings, it is found that the future scenarios require half or one-fourth of the energy as compared to the current scenario and the system performs better for them in terms of power consumption by heat pumps. The system's performance under different flow rates of water from PVT and ST is assessed. It is found that at a higher flow rate, a higher amount of energy is generated by both of the collectors, while ST shows better performance than PVT.

For the case when the system provides underfloor heating, it shows that the heat pumps require almost 25% of the energy required for radiator heating. The integrated system is then compared to that of conventional energy systems, demonstrating similar costs but almost no environmental impact and better energy efficiency.

The research findings present a compelling argument for the implementation of such energy systems in urban environments, as they indicate the possibility of substantial energy savings and a decrease in carbon emissions. The report also offers suggestions for future work, such as the application of advanced software, location feasibility studies, and various ATES to precisely model and scale such systems in various real-world circumstances.

This thesis contributes significant insights into the subject of renewable energy systems and lays the groundwork for further study and development of sustainable heat networks by offering a thorough analysis of an innovative method of sustainable energy management.

This research investigates the performance of a novel building-integrated photovoltaic (BIPV) window solution equipped with bifacial photovoltaic (bPV) cells and reflective Venetian blinds through a PV modelling approach. By modelling this PV window solution in BIGEYE, the study aims to evaluate how different types of blinds and tilt angles can help to boost the overall performance of the bPV window and to quantify the potential energy gains under varying weather conditions. First, the optical model was validated against experimental data to ensure it could accurately simulate the irradiance received at the front side of the window plane. The optical properties of the Venetian blinds were also defined to quantify the irradiance gain at the rear side of the bPV window. Then, the electrical model was also validated to make sure the model could accurately simulate the electrical behavior of the bPV window demonstrators in real operational conditions. The validated models were then used to test the effect of using different blind configurations in the bPV window’s performance.

In this way, three different types of Venetian blinds were tested: S157 (grey colored), S102 (white colored) and V95 (silver colored). The analysis revealed that, when deployed at a tilt angle of 60°, these types of blinds can help to boost the irradiance gain at the rear side of the bPV window by up to 16%, 20% and 25%, respectively, on a fully sunny day. The study also demonstrated that blinds positioned at 60° consistently achieved the greatest absolute boost in temperature-corrected performance ratio (TCPR) of the bPV window over a typical meteorological year (TMY) in Eindhoven, The Netherlands. In this way, the V95 blind type at a tilt angle of 60° demonstrated to be the optimal blind configuration for boosting the performance of this bPV window. Furthermore, an in-depth analysis was conducted to examine the influence of additional factors on the performance of this bPV window, such as the angle of incidence (AOI) between the sun and the blinds' surface normal, which showed to have an inverse correlation with the bPV window’s TCPR, highlighting that the performance of the window tends to decrease as this AOI increases.
Furthermore, the study quantified the Yearly Specific Yield (YSY) boost achievable with the optimal blind configuration, finding that a maximum boost of 19% can be attained on a TMY in Eindhoven, 18% in Stockholm, and 17% in Valencia. The difference in performance across locations is attributed to variations in meteorological and geographical factors, such as diffuse fraction and AOI. Overall, the findings provide valuable insights into how different blind configurations can enhance the performance of this bPV window and contribute to enhance the energy performance of high-rise residential towers and office buildings.

Many functional photovoltaic (PV) modules are decommissioned prematurely, often due to the financially motivated repowering of PV systems. This study assesses under which circumstances there is an environmental incentive to reuse these modules as opposed to recycling and replacing them with new, more efficient modules. A life cycle assessment was conducted, covering the end-of-life treatment, manufacturing, transport and use phase of decommissioned and new modules. The decommissioned modules had an efficiency of 14.7% in 2011, the new modules have an efficiency of 19.79%. The analysis covers two different reuse scenarios (local and export) and two different replacement scenarios, based on the quality of the recycling and the manufacturing country of the new modules.

The impacts are quantified in three categories: global warming potential, eco-cost of resource scarcity and total eco-cost. The findings indicate that, because of rapid technological advancements, the recycling and replacement of 10-year old decommissioned modules generally yield greater environmental benefits than local reuse: the net benefit in terms of global warming is greater after only 5 years. In addition, the calculations show that reusing decommissioned modules in a new PV system is only the preferred strategy from a global warming perspective if the modules are less than 5 years old, if that system is intended to have a (financial) lifetime of 10 years or longer.
However, reuse in a selected European Union member state can provide greater benefits in the global warming potential and total eco-cost impact categories than recycling and replacement. The advantage of export is driven by higher annual irradiation as well as a higher emissions intensity of the electricity mix.

These results contrast the conventional belief that reuse is always environmentally preferable to recycling. Based on this research it can be argued that in most cases of premature decommissioning, there is no strong environmental incentive to reuse the modules, provided that new PV modules are widely available or that the materials go directly to the production of new modules. The annual efficiency increase of PV technology was identified as a key parameter for this outcome.

With the integration of solar panels in urban areas, where shading is a common issue, it is desired to realize more shade-resilient designs. A DC-DC boost converter is an electronic device that can be used for maximum power point tracking (MPPT). When implementing MPPT at sub-module level, the shade resilience of the module can be increased. This thesis aims to investigate the feasibility of implementing planar inductors into c-Si solar cells using the numerical simulation software COMSOL Multiphysics®. Through simulations, the inductance and resistance values for various planar coil geometries were obtained. Subsequently, the feasibility of using these coils in a sub-module DC-DC boost converter was investigated. For this study, a specific case was assumed where a Gen 2 Cell - 160 mm c-Si cell is used with a DC-DC boost converter with a duty cycle of 0.5 and a current ripple of 20%. Given the parameters from these devices, the minimum required inductance of 1.20 μH for a frequency of 200 kHz and 2.40 μH for a frequency of 100 kHz were obtained. The series resistances that can be added to the solar cell while still maintaining high efficiency, range from 1.0 mΩ to 4.8 mΩ, for a 1% to a 5% power loss, respectively. This is all for single-cell power conversion. Two different approaches have been examined; the screen-printed coil(s) approach and the screen printing thickness exceeding coil(s) approach. The former studies coils that do not exceed the maximum thickness achievable with screen printing. As such, these coils could be simpler to implement into a solar cell production line than coils with a higher thickness. In this research, for thicknesses below 300 μm a best-case scenario is studied where the skin effect is neglected. The latter studies a larger range of thicknesses, not taking any specific production method into account, but the skin and proximity effect is taken into account. The screen-printed approach is limited to a thickness range of 10 μm to 200 μm, thus simulated by the 2D model. For the air-core single-cell inductors for DC-DC boost converter applications, the inductance and resistance values were either below the 1.20 μH threshold or above the 4.8 mΩ threshold, respectively. These thresholds change depending on the number of series-connected cells. The inductance of a planar inductor can be boosted up to 200% when adding a magnetic material in a sandwich structure, however, this will also increase the costs of the application. In a boosted-inductance case, the 3-turn coil with a thickness of 200 μm, and a 5% power loss is the only configuration that is feasible for a 200 kHz DC-DC boost converter application, with an inductance of 1.569 μH and a resistance of 3.45 mΩ. By increasing the number of coils per cell, the power dissipation in the coils can be reduced. Using this approach, six feasible topologies can be created. One of those is the nine parallel-connected 8-turn coils with a thickness of 200 μm, reaching an inductance of 1.210 μH and a resistance of 3.186 mΩ, allowing for a 200 kHz DC-DC boost converter application without any magnetic inductance increase. All six options are feasible for integration on a single cell using screen printing, however, the actual resistances will be higher due to the skin and proximity effect, and single-cell integration will be too expensive for industrial applications. When studying thicknesses above the screen printing limit, only the 4-turn coil with a thickness of 300 μm, a magnetically increased inductance of 2.718 μH, and a resistance of 4.01 mΩ, is feasible for the 100 and 200 kHz frequencies. This case however does neglect the skin effect. For the 3D model and thicknesses above 400 μm, the skin effect significantly impacts the resistance. When series connecting multiple cells to a single coil, the only feasible option is the eight-cell connected 8-turn coil for a thickness of 200 μm and 300 μm, both reaching a magnetically increased inductance of 10.431 μH and resistance of 23.33 mΩ and 15.56 mΩ, respectively.

Lightweight PV modules offer a solution to the constructional weight limitations of rooftops. PV modules made by Solarge are considered as one the lightweight PV module solutions. The aim of this thesis project is to analyse and compare the thermal- and electrical behaviour of the polymer modules with glass modules. Also, the thermal- and electrical behaviour of polymer modules with a white backsheet are compared with polymer module containing a black backsheet. First, an experimental setup was designed and installed. The PV modules selected for the installation were polymer and glass PV modules both containing half-cut cells. The white- and black backsheet polymer modules contained full PV cells. All PV modules had a pre-installation check with separate electroluminescence and indoor I-V measurements to determine the performance values under standard test condtions.
The first thermal- and electrical behaviour comparison was performed for the polymer- and glass modules over the period of 1 June till 30 September. It was found that increasing wind speed affects the cell temperature of glass modules most compared to the polymer modules. On the other hand, the level of irradiance affects most the cell temperatures of the polymer modules. Overall, it was found that the solar weighted average cell temperature was higher for the polymer modules, 39.1 - 39.3∘𝐶, compared to the glass modules, 36.9 - 37.2∘𝐶. Regarding the electrical behaviour, it was found that the mean energy yield of the polymer modules was 4.69% lower compared to the mean energy yield of the glass modules. Also the the glass modules had a higher daily performance ratio, 91.5 - 92.2%, compared to the polymer modules, 87.5 - 87.7%. Part of the difference in energy yield and performance ratio origins in the higher cell temperature for the polymer modules. However, a normalised current difference was found as well, that root in optical losses.
The second thermal- and electrical behaviour comparison was performed for the white backsheet and
black backsheet polymer modules over the period of 1 June till 30 September. It was found that
increasing wind speed affects the cell temperature of black backsheet polymer modules most compared to the white backsheet polymer modules. On the other hand, the level of irradiance affects the cell temperatures of the white backsheet- and black backsheet polymer modules with a comparable heating slope. Overall, it was found that the solar weighted average cell temperature was comparable with 8.3 - 38.7∘𝐶 for the white backsheet polymer modules and 38.1 - 38.7∘𝐶 for the black backsheet polymer modules. Regarding the electrical behaviour, it was found that the mean energy yield of the white backsheet polymer modules was 1.54% higher compared to the mean energy yield of the black backsheet polymer modules. Also, the white backsheet polymer modules had a higher daily PR, 87.7 - 89.1%, compared to the black backsheet polymer modules, 86.8 - 87.8%. The small difference in performance was not directly found in the normalised current and voltage. Measurement uncertainties are therefore seen as a possible root for this difference.

PV systems in urban environments frequently get shaded by nearby objects, which greatly reduces their yield. A potential solution for such situations is the use of reconfigurable PV modules. They are a type of modules which can reconfigure themselves under varying illumination conditions to ensure optimum yield at all times. The individual PV cells of the module are grouped into reconfigurable units/ cell blocks which can be interconnected in various ways to form a variety of unique configurations. The modules have an inbuilt algorithm which is responsible for controlling the reconfiguration process. There are various kinds of reconfiguration algorithms found in literature, each working with varying input parameters and operating principles. One such algorithm is the short circuit current sensing (SCCS) algorithm developed by the PVMD research group at TU Delft. The algorithm is meant for series-parallel
connected reconfigurable modules and uses each cell block’s short circuit current as input. It is a synchronous reconfiguration algorithm, which means it runs at regular time intervals and not when there is actually a change in the module’s irradiance conditions. Therefore, the aim of this thesis was to develop a robust reconfiguration algorithm with a shade detection mechanism. Consequently, numerous versions of a reconfiguration algorithm with shade detection mechanism were defined and tested using a simulation framework for modelling reconfigurable PV modules. It was observed that the reconfiguration algorithm that performed the best in terms of yield, reconfiguration count and accuracy was the one referred to as the ”CC4AP+IR algorithm”. The algorithm uses the module’s and a single cell block’s operating current and voltage as inputs for shade detection. It was observed that the algorithm reconfigured a fraction of the time that the SCCS algorithm reconfigured and had a DC yield comparable to the SCCS algorithm. The new algorithm was also tested using real-life data to validate its performance. This experiment indicated that if the module were to be run using the new reconfiguration algorithm instead of the SCCS algorithm, it would have run only 6% of the time that the SCCS algorithm ran, but have a comparable DC yield. The significantly lower reconfiguration count is relevant because in practice, the PV modules are connected to power converters which will not be able to tolerate the high fluctuations in output owing to frequent reconfigurations.

For the continued growth of PV capacity, it will be necessary to store vast amounts of energy to overcome seasonal differences in energy generation. To this end, the conversion of electricity to liquid or gas fuels could play an important role in the future energy system. There are numerous ways to create fuels from solar energy, the possibilities range from completely monolithically integrated photoelectrochemical (PEC) devices to configurations where the PV is completely decoupled from the electrochemical reaction. This thesis is part of the DISCO project, where the aim is to create multi-junction PV cells that can generate a high voltage and integrate these into PEC devices. The aim of this thesis project is to optimize the photovoltaic performance of a triple-junction device based on crystalline silicon (c-Si), nanocrystalline silicon (nc-Si:H) and amorphous silicon (a-Si:H).

The bottom junction of this triple-junction device is a wafer-based silicon heterojunction (SHJ) cell. The used wafer should have a smooth surface texture, since previous research has shown that growing a nc-Si:H absorber layer on the regular random pyramid surface texture results in the formation of cracks. To this end, three different proposed smooth surface textures were compared amongst each other. These surface textures were a smooth pyramid surface texture, a hexagonal surface texture created with photolithography, and a texture of crater like surface features obtained by etching a sacrificial layer. It was found that from these three textures, the best performing SHJ cells could be made from wafers with a smooth pyramid surface texture. With respect to the other surface textures, the smooth pyramid surface texturing approach leads to the smallest fraction of exposed <100> crystal orientations, which are more challenging to passivate. The performance of the SHJ cell is extremely sensitive to the passivation quality of the intrinsic amorphous silicon layers on both side of the wafer. By optimizing this passivation layer and the doped layers, SHJ bottom cell efficiencies of over 18% were achieved.

The middle junction of this triple-junction device is based on a nc-Si:H absorber layer. By varying the crystallinity of this i-nc-Si:H absorber layer, it was found that optimal photovoltaic performance is achieved for a crystalline volume fraction between 50% and 65%. Furthermore, the thickness of this absorber layer can be varied to improve the current matching between the different subcells in the triple-junction device. To this end, the effect of a varying absorber layer thickness on the single-junction PV performance was investigated. It was found that the absorber layer thickness is a trade-off between on the one hand Voc and FF, and on the other hand Jsc. For example, doubling the absorber layer thickness from 2.5 µm to 5.0 µm results in a Jsc increase from 18.2 mA/cm² to 20.8 mA/cm², whereas the Voc and the FF respectively decrease from 506 mV and 0.65 to 481 mV and 0.59.
Once the bottom and middle junctions were optimized, different material combinations in the tunnel recombination junctions of the multi-junction device were investigated. It was found that p-nc-SiO_x and n-nc-SiO_x with appropriate doping levels and contact layers were the best performing materials in both tunnel recombination junctions. When the Voc of the tandem cells was compared to the sum of the single-junction cells, the optimized tunnel recombination junctions resulted in a Voc loss of 7 mV in the top tandem (nc-Si:H/a-Si:H), and 51 mV in the bottom tandem (SHJ/nc-Si:H).
By making use of all the performed optimizations described above, a triple-junction device based on c-Si/nc-Si:H/a-Si:H was processed. The final device had a PV efficiency of 13.63%, with a FF of 0.755, a Voc of 1982 mV and a Jsc of 9.11 mA/cm². To the best of our knowledge, this is a world-record efficiency for this type of solar cell configuration. If it is managed in future research to match the current over the different subcells more evenly, this device has the potential to achieve a current density over 12 mA/cm².

Within the photovoltaic industry, a lot of research is done in order to minimize losses which are created during the conversion of solar light to electrical energy. In a crystalline silicon solar cell light has to pass through several layers before it enters the silicon wafer where the electron-hole pairs are generated. As one can imagine, if more light reaches the active layer, more electron-hole pairs can be generated. It is highly desired that only one layer, the active layer, is absorbing photons of the solar spectrum. The active layers at the sunny side of the silicon wafer should be highly transparent for solar light. In addition to being transparent, these layers should be conductive to extract the generated charge carriers to the metal contacts. Current layers applied at the sunny side are not optimally transparent, so it is still possible to increase the efficiencies in the crystalline silicon solar cells. In this study, doped silicon oxide layers have been explored as a potential more transparent layer for passivation of both the silicon surface and the metal contacts. Two routes for the fabrication of doped silicon oxide layers were investigated: post-oxidation of doped polycrystalline silicon layers and post-doping of in-situ grown silicon oxide layers. To characterize this new type of material, several different measurement techniques have been applied to improve our understanding of Low-Pressure Chemical Vapor Deposition deposited silicon oxide passivating contact layers. It was found that the structure and composition of the layers is very different for these different routes. However, very good and stable surface passivation (minority carrier lifetime of >3ms) can be achieved with both types of silicon oxide layers. Also, sheet resistance measurements have indicated that phosphorus doping in silicon oxides is possible. For better insight into the electrical properties of these layers, further testing in electronic test structures is advised.