The built environment is among the highest energy consuming sectors worldwide. However, buildings have large surface areas that can be used to improve the building energy performance. One example is by integration of photovoltaic systems in roofs and facades, which can reduce the carbon footprint of the built environment. An emerging field that could lead to energy savings involves the glazing. Switchable or smart windows allow for a variable transparency which affects the amount of incoming daylight and solar heat. Manually controlled smart windows however, require electricity to function and could thus be powered by solar energy to function autonomously. Smart windows have been shown to improve the building energy performance by reducing heating, cooling and lighting loads and can also be used to optimize the visual and thermal comfort conditions of occupants. In this thesis project the energy performance of three types of switchable glazing has been compared to different window technologies including electricity generating photovoltaic windows. Additionally, the hourly and yearly electricity requirements of each smart window and the corresponding minimal photovoltaic system requirements have been determined.

The advancement of innovative PV technologies has led to an all-time high integration of the same in the urban environment. Furthermore, development of decentralized power systems complements this rise as it supports in-situ power consumption. Due to space availability constraints in urban environments and a need for appealing aesthetics, tailored PV modules is gaining importance. However, it is desirable to achieve maximum power out of these tailored PV modules to ensure efficiency in space usage.
Literature suggests that one of the most apt performance metric for estimating the goodness of design for PV modules is the CTM ratio. However, various challenges incurred upon implementing the present CTM analysis algorithms on tailored PV modules suggests the need for development of a different approach to estimate the same. The presented work strives towards the development of a tool for the prediction of various performance metrics, including the CTM ratio, of both standard and tailored PV modules to aid its user to make educated design choices to develop optimum modules.
The methodology used for development of the tool encompasses various steps which occur in a pre-programmed flow. Firstly, a developed script automatically creates the module structure based on user inputs. Hereafter, ray tracing is implemented and its results furnishes optical performance of the module. Furthermore, an electrical loss calculation model is developed, using differential element method, which when coupled with the optical performance data enables the estimation of the CTM ratio and other performance metrics. The tool is programmed in Matlab to ensure easy integration of the same with the PVMD toolbox for future research on module designs.
Firstly, an attempt is made to optimize the parameters of the mini-module for maximizing its performance. For a white backsheet test mini-module, optimization through the usage of the tool, leads to a 5.52 % gain from the worst case design. This gain is realized by achieving an optimal tuning between the cell-cell and cell-edge spacing. Moreover, when compared, the white backsheet module’s power production capacity outperforms the black backsheet module by around 13.93 %. Additionally, effect of busbars on the performance of the module is investigated.
Furthermore, the tool is able to derive novel empirical formulas which, for different module architectures, predict the effect of cell top metallization on the cell photocurrent density in an encapsulated environment.
Secondly, efficacy of the tool is demonstrated for a comparative study between a 60 cell module and its corresponding 120 half-cut cell module. The tool suggests the half-cut cell module to have a 2.91 % gain in CTM ratio as compared to its full cell counterpart.
Thirdly, the tool demonstrates modelling and simulation of glass-glass modules and achieve optimization. The tool also recommends an increase of the dimension size for the test module to 20×20 cm2 to achieve the exemplary target transmission of 14 %.
Lastly, the tool efficacy is demonstrated for a triangular PV module. This module with a white backsheet is found to outperform its black backsheet counterpart by 9 % in CTM ratio.

The residential and service sectors are responsible for the 39% of the total energy consumption. 80% of this energy is used for heating purposes. Achieving nearly zero energy buildings is a major goal for the near future. The design of an integrated electrical and thermal system can substantially help to reach such objective. The façade is the biggest area of a building and could be utilised to convert incident solar energy to electrical and thermal energy. In previous work (2019), the combination of building integrated PV modules with solar chimney on a façade was investigated to study its energetic performance. One of the main findings was that using the thermal energy from the photovoltaic modules on the air inside the cavity of the chimney is not possible due to its low quality of heat. It was concluded that the utilization of heat could be better by using auxiliary systems, like photovoltaic thermal systems for water heating. The aim of this work is to create a computational model to calculate the thermal and electrical performance of PV thermal (PV/T) modules combined with a solar chimney. Two new designs for better heat utilization where considered and compared. The first design is for the PV modules to be installed at the front of the solar chimney with fins (Fins design) and the second design is to couple the PV modules installed on the wall inside the solar chimney with water pipe system (Water pipe design). These designs are also compared with the same configurations but without the thermal systems (No fins & No water pipes designs). In addition, two new strategies are introduced to improve the performance of the model. The first strategy is the optimization of the solar chimney openings with respect of time for the highest power generation. The second strategy is the variation of the water mass flow with respect to time for highest water-thermal energy and optimum cooling of the PV cells. The model was developed in MATLAB and it is based on 2D finite difference transient implicit method. To reduce the computational time, the density of the nodes varies in respect of temperature gradient. In addition, secondary models were created to increase the accuracy and sensibility of the model such as water tank and water pump models. The models were studied for a building in Delft, Netherlands, and the scale of the chosen system is 10m2. It is concluded that Water pipes design provides the overall best energetic performance mainly because of the high water-thermal energy with yearly energy efficiency of 64.3%. However, the best electrical performance is observed from the Fins design and the best air-thermal performance from the No water pipes design.

Building energy consumption is one of the highest of any sector. Building integrated Photovoltaics (BIPV) have the potential to eventually contribute to 50%-70% of the total energy demand. However, one of the main barriers that hinder the acceptance of solar energy systems as an integrated part in the buildings’ envelope is the limited aesthetics. The common black and blue panels with visible cells usually cause incompatibility with the outer appearance of architectural structures. Consequently, the combination of BIPV technology with colored PV modules will provide solutions to architects and stakeholders who are often skeptical on embed PV systems in buildings attributable to their appearance. To overcome this barrier, different techniques have been developed to provide color to photovoltaic modules. One of the most promising technologies are optical filters. These devices selectively reflect light via interference effects, thus providing the possibility of changing the color appearance of a module. Light reflection, however, reduces the current generated by the solar cells, but also, reduces thermalization losses that negatively impact the cell performance by increasing its operational temperature. In this thesis, a spectrally resolved thermal model in MATLAB has been developed to fully assess what is the real impact of different optic filters under real operational conditions in terms of temperature, efficiency and energy yield. The model considers the angular dependence of optic filter’s on PV modules on both appearance and performance for installations on a façade, roof and free mounted PV (BAPV). In addition, the optimum optic filter thicknesses for ten main colors has been determined based on maximum energy yield.
The model has been validated for three consecutive days and the simulated results for colored modules and module without optic filter were proved to be very close to the corresponding measured values; deviation of 1.5 degrees of simulation models have been obtained during the temperature peak of the modules. The simulation results show that the performance of the optic filters changes depending on the location, installation layout and the incident irradiance. More specifically, temperature drop of 9 degrees has been observed on roof installations from colored modules compared to the corresponding standard module. In addition, the implementation of air gap between the module and the roof has been verified to decrease up to 20 degrees the working temperature and significantly increase the overall energy yield for both colored and standard modules. Nevertheless, in terms of yearly energy yield (kWh/m2), from the tested colors the relative decrease with respect to the standard module was found approximately 16% observed from the most lossy colors.

As the world is trying to rely less on fossil fuels for electrical energy. To do this, the alternatives should be as efficient and durable as possible. The alternative that has been growing the fastest in recent years is solar energy. Apart from it’s growth in the market share, the efficiency of photovoltaic (PV) cells has also steadily grown. Recently, this trend has started to stagnate, since most avenues of efficiency improvement have been exhausted. However, the possibilities of thermal management (i.e. cooling) of PV cells are relatively unexplored. An increase in cell temperature causes a decrease in efficiency, in other words, less sunlight is converted into electrical energy. Moreover, high operating temperatures cause damage in solar cells, reducing their lifetime by months (or even years). One promising technology that can keep cell temperatures low is the Phase Change Material (PCM) based heat sink. A PCM takes a lot of energy to melt and during phase change it remains at a stable temperature. PV + PCM systems have shown to be able to increase cell efficiency by up to 8%. In order to get a better grip on the workings and the potential of PCMs as a heat sink for PV cells, this work presents an implicit, transient, spectrally resolved, MATLABbased model that can simulate module temperature and phase change within the PCM. The model uses SMARTS in combination with irradiance data to create spectral irradiance data. Using this spectral data together with GenPro4 provides the amount of energy absorbed by each layer of the PV cell. The PV part of the model is validated for a summer week in the Netherlands, with a Mean Absolute Error (MAE) of 1.83 and a Mean Bias Error (MBE) of 0.56. For a winter week in January the MAE was 1.76 and the MBE 1.44. When simulating only a PV module (so no PV + PCM system), the model can simulate 45 hours of data per hour, with one minute time step. When validating the PV + PCM model for the same weeks, the MAE was 2.96 and the MBE 1.91 for the summer week and a MAE of 1.37 and MBE of 1.15 for the winter week. When simulating a PV + PCM system the simulation time drops to 18 hours of simulated data per hour, due to a larger mesh and the requirement of several iterations in the PCM model. With this model a wide range of PV + PCM systems (e.g. with different thicknesses and melting temperatures) can be simulated for any location, provided that there is access to the following weather data: temperature, wind speed and irradiance.

While there are many factors influencing the efficiency of photovoltaic (PV) cells one of the most important ones is temperature. Module temperatures can get significantly higher than the ambient temperature, increases of up to 30°C have been reported in literature. An increase in temperature has an adverse effect on the module’s efficiency, literature has reported a drop of 0.40−0.65%/°C. Therefore, it is not uncommon that during warmsunny days PVmodules operate at a much lower efficiency than advertised by the manufacturer. Different methods of thermal management can be applied. In this research, the effect of phase change materials (PCM) to passively lower the operating temperature of PV panels was studied. During the phase change of a material heat is absorbed as latent heat instead of sensible heat, this does not cause the temperature of the material to increase. Using this process a PCM can keep a relatively stable temperature until it has completely changed its phase. This can be utilised by placing PCM behind a PV module, so that the heat generated in the panel can be absorbed by the PCM while remaining at a stable temperature. The scope of this research was to performmeasurements with a PV-PCMsystem under real weather conditions. Additionaly, a thermalmodel was build using ComsolMultiphysics, to make predictions for the optimal PCM parameters. This thermalmodel was validated with the results from the measurements. Measurements for a free rack situation showed surprisingly a slight increase in temperature of the PVPCM module compared to a reference PV module. Most likely due to convective cooling caused by the wind. And indeed, after installing insulation material at the back of the modules to emulate building integrated photovoltaics (BIPV) a significant decrease was found. For a two week period of measuring a −6.69°C temperature reduction was found, with a peak difference of −21.7°C. This resulted in an energy yield increase of 2.8% compared to the reference panel over this period. From this work, it can be concluded that PCM thermal management is not advisable for free standing modules due to the large influence of convective cooling caused by the wind. However, this method of thermal management can have significant benefits in BIPV situations where convection is not relevant.

As solar energy finds its way into unexpected applications such as buildings or objects, the traditional rectangle-shaped module becomes inadequate. Although traditional modules have been optimized to deliver a large amount of power, they cannot be fitted easily into a façade or a wearable. This is why, new methods for integrating solar power into buildings and products have to be found. These methods should be attractive to designers and architects and must also allow solar energy to reach common people.
The fabrication of mini-modules can help with this task as they can be fabricated with the already mature technology of crystalline silicon solar cells. They can be made lightweight and in different figures.
This work aims to investigate ways to facilitate the fabrication of modules for use in Building Integrated Photovoltaics or Product Integrating Photovoltaics by means of studying the impact of cutting solar cells into different figures and sizes. To prove the suitability of tools of full-sized modules into mini modules, a Cell-To-Module analysis is performed.
The results show that crystalline silicon can be effectively used for making modules in reduced sizes tackling the full integration of solar cells into objects.

Global energy demand is on the rise. According to the International Energy Agency (IEA), in 2018, the building sector alone constituted 28 % of all energy-related CO2 emissions. In an effort to reduce the carbon footprint of the building sector, the European Union has decreed that every new building from 2021 must be a nearly zero energy building where the low energy for such buildings must come from renewable sources. While this policy works well for new buildings, there needs to be also a solution developed for existing buildings or monumental buildings to be able to easily harness renewable energy, without the need for any major and costly renovation. The concept of a flexible cloth-based solar curtain as a plug and play solution for existing buildings has been explored in the current research, with particular focus on a bifacial (two-sided) design, to assess the significance of the indoor reflected daylight and artificial lights on the rear side power output of such a semi-transparent solar curtain. An optical model representing a basic semi-transparent curtain comprising 70 % cloth of roughly 62 % transparency (based on availability), and 30 % of bifacial solar photovoltaic (PV) minimodules, is prepared as a base case. To validate the optical model, it is replicated on a smaller scale and tested using an identical experimental setup in a controlled environment using a solar simulator. Four cases are prepared for this: the curtain in an empty white-walled room, the curtain in the same room but with some furniture, the curtain in a shorter room with a white rear wall and the curtain in a shorter room with a black rear wall. An analysis of simulation and experimental results shows near likeness between the two with an error margin of 3.3 % for the base case to 10.6 % for the black rear wall case. Slight non uniformity of optical property inputs used in the simulation model and an overestimation of experimentally measured power due to a relatively lower irradiance seen by the reference cell are attributed to this difference. After successful validation of the optical layout, the model is made to scale in simulations to forma PV curtain module of 538.44 Wp DC installed capacity. Using a north-east facing room as reference, an annual simulation is found to give a total DC energy yield of 188.45 kWh or 323 kWh/kWp with a bifacial gain of 8.64 %. 10 hours daily of artificial lighting inside the office is seen to increase the annual DC energy yield by 1.33 %. With an assumption that the curtain remains closed throughout sunshine hours (since it allows diffuse light to enter through its porous cloth), the power output of the curtain is seen to meet modest DC annual load profiles of 57.76 kWh in an office room for 95 % of the year with a 145 Wh lithium ion battery bank and of 48.86 kWh in a residential room for 92%of the year, but with a much higher 290 Wh battery capacity, due to a greater mismatch between generation and demand. A sensitivity analysis for room orientation shows that for a more optimal azimuth of 202.5° (180° being south), the same curtain gives 82%more annual DC yield compared to its current orientation, but at a much lower bifacial gain of 7.8 %. When analyzed for performance in different locations across the world, the curtain intuitively gives the best yield for locations in the southern hemisphere due to its orientation towards the north east. Bifacial gain is nevertheless, most significant for temperate locations where low average annual insolation makes the gain due to bifacial more significant. In cases where the room depth is reduced by half, yield is seen to improve by 2.1 %. Halving the amount of PV in the curtain, improves the bifacial gain by nearly 0.6 % but reduces the annual yield by 49 %. Conversely, doubling the PV in the curtain, results in a dip in bifacial gain by about 3.6 %, but an increase in annual DC power by 87 %. Although this is attractive, such a case must be treated with caution since the likelihood of leaving this curtain (that is now more opaque than semi-transparent) open during sunshine hours is higher. This can result in a lower power output than the base case as well as worse aesthetics. Finally, it is concluded that a bifacial curtain is a beneficial for ‘solarizing’ existing buildings with minimal renovation. The bifacial aspect is best exploited for rooms with sub-optimal azimuths. Nevertheless, to make the most of the PV curtain, it is advised that itmust be placed in shorter rooms with large windows and ideally facing the most optimal direction.

Whilst research in solar cell materials lead to higher efficiencies every year, new difficulties arise with every breakthrough to get an even higher efficiency. Therefore, every component of a PV system should be examined, as well as how their behaviour under operation affects performance to improve the overall PV yield. In particular the temperature of a module can have a negative impact on the power output. The drop in power output is a consequence of a negative thermal coefficient that results in a decrease of open circuit voltage with increasing temperature. For silicon solar cells, efficiency drops of 0.4-0.65%/°C have been reported in literature. Moreover, daily repetition of temperature cycles can cause mechanical degradation, thereby decreasing the lifetime of PV modules. In this thesis, phase change materials (PCM) have been studied as a method to passively reduce the operating temperature of PV modules. This is based on the ability of materials to stay at a relatively stable temperature during a phase change. By placing a PCM at the back of a PV module, the temperature difference between the module and the melting PCM causes a thermal gradient, resulting in conduction of heat away from the
module. In order to find the optimal properties of a PCM, a thermal model was first developed in COMSOL Multiphysics and benchmarked with field measurements from literature. Simulations for Rotterdam, the Netherlands, revealed that an optimized PCM could increase the yearly electrical yield by 1.23% for a rack-mounted module, or 3.52% for a roof-mounted module. Furthermore, measurements were performed with commercially available PCMs under a Large Area Solar Simulator (LASS). These were able to reduce the average module temperature by 30-36°C, albeit under heavy infrared radiation coming from the simulator.

Building Integrated Photovoltaics (BIPV) has the potential to play a major role in the ongoing transition towards nearly zero energy buildings. However, the BIPV market is still a niche market, representing only 1% of the global PV share. One of the main barriers that hinder the deployment of BIPV is the lack of aesthetic flexibility. Architects and designers are often reluctant to embed PV systems in buildings due to their unsuitable color.
In this thesis, the use of interference filters (IFs) as color coating solution for PV modules is proposed. IFs are optical devices designed to selectively reflect a narrow portion of the visible solar spectrum while transmitting the remaining part. The structural coloration provided by the filter is highly dependent on the angle of incidence of the light. This angular dependence could be an issue for BIPV applications, since color homogeneity is often an important requirement. The objective of this work is to model, fabricate and assess the opto-electrical performance of colored crystalline silicon (c-Si) PV modules based on interference filters, with the final goal of increasing the aesthetics of this technology.
First, the angular resilience challenge is addressed. Simulation results show that texturing the glass surface significantly improves the color stability, thanks to diffuse reflection of light. Very high angular resilience up to 80º can be achieved with a double-side texture profile made of hemispherical grooves. Secondly, five interference filters deposited on different glass substrates are used to fabricate 10 x 10 cm² c-Si colored mini-modules. The optical characterization of the demonstrators
allows to partially validate the optical model and confirm the good angular resilience of the textured surfaces. Finally, the electrical performance of the mini-modules is evaluated. I-V measurements show that IFs only affect the short-circuit current of the mini-modules due to optical losses. Depending on the color and the topology of the surface, absolute efficiency losses range from 0,95% to 4,6%.