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1
Turban, David. "Electronic structure modelling of singlet fission in organic photovoltaics." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271889.
Full textAbstract:
Singlet fission is a multiple-exciton-generation process found in organic materials that could help to enhance the efficiency of future photovoltaic devices, by overcoming the Shockley-Queisser limit. In spite of considerable experimental and theoretical attention, different aspects of the process are still not fully understood. The main reason for this is that singlet fission is characterised by a complex interplay of electronic states, vibrational modes and electrostatic screening effects. In this thesis we employ \emph{ab initio} electronic structure techniques to study the excitations involved in fission in molecular crystals and dimers, using the well-studied pentacene molecule as a reference system. Linear-scaling density functional theory (LS-DFT) is used to model the influence of the crystal environment on charge-transfer (CT) configurations in the pentacene molecular crystal. We derive a general dipole correction scheme that allows us to eliminate finite-size effects from the calculations. We find that CT energies are significantly lowered by the response of the crystal environment, bringing them close to the energies of local excitations. This result lends support to the idea that the photoexcited precursor state to fission has significant CT character, and emphasises the role played by CT configurations in fission in the crystal. Furthermore, we use DFT to parametrise a linear vibronic coupling Hamiltonian of a covalent dimer of pentacene, forming the basis for many-body quantum dynamics calculations of the interplay between electronic and vibrational degrees of freedom. This reveals an interesting role for symmetry in fission in such dimers. Due to their high symmetry, couplings that could enable fission are precluded at the ground-state geometry. However, dynamic symmetry breaking by vibrational modes opens up an efficient pathway for fission, via an avoided crossing mediated by virtual CT configurations. Finally, we explore the influence of different side-groups and solvent environments on fission in pentacene dimers. To this end, we employ DFT with both implicit and explicit solvent models, combined with large-scale calculations to achieve sufficient sampling of solvent-solute configurations.
2
Cole, Ian R. "Modelling CPV." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18050.
Full textAbstract:
A methodology for the simulation of CPV systems is presented in four distinct sections: input, optics, uncertainty and electrical output. In the input section, existing methods of describing the solar irradiation that is incident at the primary optical element of a CPV system are discussed, the inadequacies of the existing methods are explored and conditions of validity for their use drawn. An improved and spectrally extended model for a variable, spatially resolved solar image is arrived at. The model is used to analyse losses at the primary concentration device stage under varying solar profiles and air masses. A contextual analysis of an example Seattle based CPV system operating with constant solar tracking errors of 0.3-0.4° show a corresponding loss in isolation available to the optical system of 5-20%, respectively. In the optics section, an optical ray trace model is developed specifically for this work. The optical ray trace model is capable of the spectrally resolved ray tracing of all insolation input models discussed above. Plano-convex and Fresnel lenses are designed, investigated and compared using each of the insolation models described in the input section. Common CPV component material samples for the plano-convex and Fresnel lenses are analysed for their spectrally resolved optical properties. The computational expense of high resolution spatial and spectral modelling is addressed by means of a spectrally weighted banding method. The optical properties parameter spectral weighting method can be applied to any arbitrary spectral band. The bands used herein correspond to the active ranges of a typical triple-junction solar cell. Each band shows a different spectral dependency. Banded beam irradiation proportions are shown to change by as much as 10% in absolute terms within the air mass range of 1 to 3. Significant variations in spectrally banded illumination profiles are found with the extended light source insolation model. These banded variations are mostly unaccounted for with the use of approximated insolation models, further compounding the argument for extended light source Sun models in CPV system simulations. In the uncertainty section, the limitations of the manufacturing process are explored. Manufacturing tolerance errors from manufacturer datasheets are presented. These production uncertainties are used in the design of an erroneous plano-convex lens which is then analysed with the optical modelled presented in the optics section and compared to the ideal design specification. A 15% variation in maximum intensity value is found alongside a linear shift in the focal crossover point of approximately 0.2mm, although the optical efficiency of the lens remains the same. Framing manufacture errors are investigated for a square Fresnel lens system resulting in a linear shift of the focal centre of approximately 0.85mm. A process for the calculation of wind loading force on a CPV array is also presented. The process uses real 2 second resolution wind data and highlights the chaotic nature of loading force. A maximum force of 1.4kN was found on an example day for a 3m by 3m by 0.1m cuboid (i.e. CPV array); corresponding to a wind speed of approximately 13m/s, which is well within the typical operating range of a CPV tracking system. In the electrical output section, a spatially resolved solar cell model is identified and used for the investigation of solar cell performance under the inhomogeneous cell illumination profiles produced in the uncertainty section. Significant differences in the maximum power point of the cell IVs are found for the ideal and erroneous system illumination profiles. Approximately, a 15% variation is found in the plano-convex lens example, with a relative difference of 4% attributable to illumination profile distortion, and a 6% variation in the module framing component example. These results further highlight the need for the consideration of production uncertainties in CPV system simulation.
3
Wu, Xiaofeng. "Fast spatially-resolved electrical modelling and quantitative characterisation of photovoltaic devices." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18018.
Full textAbstract:
An efficient and flexible modelling and simulation toolset for solving spatially-resolved models of photovoltaic (PV) devices is developed, and its application towards a quantitative description of localised electrical behaviour is given. A method for the extraction of local electrical device parameters is developed as a complementary approach to the conventional characterisation techniques based on lumped models to meet the emerging demands of quantitative spatially-resolved characterisation in the PV community. It allows better understanding of the effects of inhomogeneities on performance of PV devices. The simulation tool is named PV-Oriented Nodal Analysis (PVONA). This is achieved by integrating a specifically designed sparse data structure and a graphics processing unit (GPU)-based parallel conjugate gradient algorithm into a PV-oriented numerical solver. It allows more efficient high-resolution spatially-resolved modelling and simulations of PV devices than conventional approaches based on SPICE (Simulation Program with Integrated Circuit Emphasis) tools in terms of computation time and memory usage. In tests, mega-sub-cell level test cases failed in the latest LTSpice version (v4.22) and a PSpice version (v16.6) on desktop PCs with mainstream hardware due to a memory shortage. PVONA efficiently managed to solve the models. Moreover, it required up to only 5% of the time comparing the two SPICE counterparts. This allows the investigation of inhomogeneities and fault mechanisms in PV devices with high resolution on common computing platforms. The PVONA-based spatially-resolved modelling and simulation is used in various purposes. As an example, it is utilised to evaluate the impacts of nonuniform illumination profiles in a concentrator PV unit. A joint optical and electrical modelling framework is presented. Simulation results suggest that uncertainties introduced during the manufacturing and assembly of the optical components can significantly affect the performance of the system in terms of local voltage and current distribution and global current-voltage characteristics. Significant series resistance and shunt resistance effects are found to be caused by non-uniformity irradiance profiles and design parameters of PV cells. The potential of utilising PVONA as a quality assessment tool for system design is discussed. To achieve quantitative characterisation, the PVONA toolset is then used for developing a 2-D iterative method for the extraction of local electrical parameters of spatially-resolved models of thin-film devices. The method employs PVONA to implement 2-D fitting to reproduce the lateral variations in electroluminescence (EL) images, and to match the dark current-voltage characteristic simultaneously to compensate the calibration factor in EL characterisations. It managed to separate the lateral resistance from the overall series resistance effects. The method is verified by simulations. Experimental results show that pixellation of EL images can be achieved. Effects of local shunts are accurately reproduced by a fitting algorithm. The outcomes of this thesis provide valuable tools that can be used as a complementary means of performance evaluation of PV devices. After proper optimisation, these tools can be used to assist various analysis tasks during the whole lifecycle of PV products.
4
Milshyn, Vladyslav. "Modelling the Effect of Photovoltaics and Battery Storage on Electricity Demand : Implications for Tariff Structures." Thesis, Uppsala universitet, Industriell teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301407.
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This project examines the implications of the photovoltaic power generation as well as the battery storage systems on the distribution network tariff structures. Different types of existing distribution tariffs were applied to the residential households’ demand patterns. Several scenarios of demand profiles were theoretically investigated. First scenario included households’ consumption under current situation without on-site power production and any storage, second scenario concerned penetration of average size of solar panel installations and the last demand profile with maximum possible size of photovoltaic panels complemented with battery storage use. The distribution tariffs included in the comparison are: power based tariff and two energy based tariffs, one with flat-rate and another with time-of-use structure. Distribution tariffs were normalized with the aim to research the implications of the on-site production and storage use. Normalization factors were used when comparing financial bills from the households under above mentioned scenarios. Energy distribution tariffs have higher potential for households to save on their energy bill with the introduction of the on-site solar power utilization. On the other hand power tariff provides higher incentive for the implementation of the demand response strategies in the households.
5
Widén, Joakim. "System Studies and Simulations of Distributed Photovoltaics in Sweden." Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132907.
Full textAbstract:
Grid-connected photovoltaic (PV) capacity is increasing worldwide, mainly due to extensive subsidy schemes for renewable electricity generation. A majority of newly installed systems are distributed small-scale systems located in distribution grids, often at residential customers. Recent developments suggest that such distributed PV generation (PV-DG) could gain more interest in Sweden in the near future. With prospects of decreasing system prices, an extensive integration does not seem impossible. In this PhD thesis the opportunities for utilisation of on-site PV generation and the consequences of a widespread introduction are studied. The specific aims are to improve modelling of residential electricity demand to provide a basis for simulations, to study load matching and grid interaction of on-site PV and to add to the understanding of power system impacts. Time-use data (TUD) provided a realistic basis for residential load modelling. Both a deterministic and a stochastic approach for generating different types of end-use profiles were developed. The models are capable of realistically reproducing important electric load properties such as diurnal and seasonal variations, short time-scale fluctuations and random load coincidence. The load matching capability of residential on-site PV was found to be low by default but possible to improve to some extent by different measures. Net metering reduces the economic effects of the mismatch and has a decisive impact on the production value and on the system sizes that are reasonable to install for a small-scale producer. Impacts of large-scale PV-DG on low-voltage (LV) grids and on the national power system were studied. Power flow studies showed that voltage rise in LV grids is not a limiting factor for integration of PV-DG. Variability and correlations with large-scale wind power were determined using a scenario for large-scale building-mounted PV. Profound impacts on the power system were found only for the most extreme scenarios.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 711
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Shepero, Mahmoud. "Modelling the Penetration Effect of Photovoltaics and Electric Vehicles on Electricity Demand and Its Implications on Tariff Structures." Thesis, Uppsala universitet, Industriell teknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-295426.
Full textAbstract:
The shift towards more renewable energy sources is imminent, this shift is accelerated by the technological advancement and the rise of environmental awareness. However, this shift causes major operational problems to the current grid that is optimised for unidirectional power flow. Besides the operational problems, there are problems related to the optimal tariff scheme. In this thesis a study on the effect of the adoption of photovoltaic solar panels and the electric vehicles on the households' electricity demand profile is presented. The change on the demand profile is going to affect the current tariffs, this effect is also explored in this thesis. In this thesis real life data on household electricity use and photovoltaic power production was used. For electric vehicle charging simulated data was used. Besides that, a demand response scheme for electric vehicle is proposed in order to estimate the savings potential of this demand response on the electricity bill. The results show that the change in the demand profile is not merely a change in the total energy consumption, but it is a change in the power peaks as well. The peaks change significantly in condominiums and rental apartments, in this households' type it increases by around 80%, while in detached and row houses little change is noticed on the peaks, yet they still increase by around 10%. The demand response shows around 1- 12% savings in the distribution bill depending on the household, however it showed more incentives for condominiums and rental apartments. The current distribution tariffs perform asymmetrically with the various households. However, one tariff ensures 11.7 MSEK financial revenue for the distribution system operator, this is higher than the other tariffs' revenue by more than 28.5%. The new prospective situation requires totally different tariffs that ensure a balance between firstly a reasonable revenue for the distribution system operator and secondly incentives for consumers to self produce electricity as well as to reduce their peaks.
7
Gabr, Ahmed. "Modelling and Characterization of Down-Conversion and Down-Shifting Processes for Photovoltaic Applications." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35048.
Full textAbstract:
Down-conversion (DC) and down-shifting (DS) layers are optical layers mounted on the top surface of a solar cell that can potentially increase the solar cell efficiency. The effect of DC and DS layers to enhance the performance of single-junction solar cells has been studied by means of simulation and experimental work. In this thesis a model is developed to study the effects of DC and DS layers by modifying the incident spectrum. The effect of the layers on ideal cells as well as commercial grade silicon and CIGS solar cells that are modeled in a device simulator is examined.
Silicon nanocrystals (Si-nC) embedded in a silicon dioxide matrix to act as a DS layer were fabricated and characterized at McMaster University as part of this project. The measured optical properties as well as the photoluminescence measurements are used as input parameters to the optical model. The enhancement due to the Si-nC when coupled to silicon and CIGS solar cells is explored. Beside the DC and DS effects, there is also disturbance to the surface reflections due to the addition of a new layer to the top surface and is referred to as antireflection coating (ARC) effect. For the simulated silicon solar cell under the standard AM1.5G spectrum (1000W/m2), a maximum increase in Jsc of 8.4% is achieved for a perfect DS layer as compared to a reference cell, where 7.2% is due to ARC effect and only 1.2% is due to DS effect. On the other hand, there is an increase in Jsc of 19.5% for the CIGS solar cell when coupled to a perfect DS layer. The DS effect is dominant with 18%, while the ARC effect contributes only 1.5% to the total Jsc enhancement.
Accurately characterizing DS layers coupled to solar cell requires knowledge of optical properties of the complete structure. Internal quantum efficiency is an important tool for characterizing DS systems, nevertheless, it is rarely reported. In addition, the ARC effect is not experimentally decoupled from the DS effect. In this work, a straightforward method for calculating the active layer contribution that minimizes error by subtracting optically-modeled electrode absorption from experimentally measured total absorption.
8
au, A. carr@aip org, and Anna Judith Carr. "A Detailed Performance Comparison of PV Modules of Different Technologies and the Implications for PV System Design Methods." Murdoch University, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20050830.94641.
Full textAbstract:
In designing any power generation system that incorporates photovoltaics (PV) there is a basic requirement to accurately estimate the output from the proposed PV array under operating conditions. PV modules are given a power rating at standard test conditions(STC) of 1000Wm-2, AM1.5 and a module temperature of 25 °C, but these conditions do not represent what is typically experienced under outdoor operation.
It is well known that different PV technologies have different seasonal patterns of behaviour. These differences are due to the variations in spectral response, the different temperature coefficients of voltage and current and, in the case of amorphous silicon (a-Si) modules, the extra effect of photo-degradation and thermal annealing.
In this study a novel method has been used to obtain highly accurate energy output data
from six different PV modules representing five different technologies:
Single crystal silicon (c-Si).
Poly-crystalline silicon (p-Si) (2 modules).
Triple junction amorphous silicon (3j, a-Si).
Copper indium diselenide (CIS).
Laser grooved buried contact (LGBC, c-Si) crystalline silicon.
This data set includes all the associated meteorological parameters and back-of-module temperatures.
The monitoring system allows the simultaneous measurement of six different modules under long-term outdoor operation, which in turn allows a direct comparison of the performance of the modules.
Each of the modules has been deployed for at least one year, which provides useful information about the seasonal behaviour of each technology.
This data set ultimately provides system designers and consumers with valuable information on the expected output of these different module types in climates like that of Perth, Western Australia.
The second part of the study uses the output data collected to assess and compare output predictions made by some currently available photovoltaic performance prediction tools or methods. These range from a generalised approach, as used in the Australian Standards, to the commercially available software packages that employ radiation, thermal and PV models of varying complexities. The results of these evaluations provide very valuable information, to PV consumers, about how complex PV output prediction tools need to be to give acceptable results.
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Patrick, Christopher Edward. "Photoemission spectra of nanostructured solar cell interfaces from first principles." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:fa2333ea-7016-4d6f-8d55-aee4178482a6.
Full textAbstract:
Photovoltaic (PV) technologies could provide abundant, clean and secure energy through the conversion of sunlight into electricity, but currently are too expensive to compete with conventional sources of power. Novel PV devices incorporating nanostructured materials, such as the dye-sensitized solar cell (DSC), have been identified as viable, low-cost alternatives to traditional solar cell designs. In spite of technological progress in the field over the last twenty years, the underlying physics governing DSC operation is still not well understood. In this thesis, first-principles (i.e. parameter-free) calculations are performed with the aim of connecting experimentally-measured photoemission data to the underlying atomistic and electronic structure of interfaces found in DSCs. The principal system under study is the interface between anatase titanium dioxide (TiO2) and the "N3" dye molecule, one of the most widely-investigated device designs in DSC research. Atomistic models of the interface are determined within density-functional theory. Core-level spectra of these interface models are then calculated using a ∆SCF approach. Comparison of the calculations to published experimental data finds that intermolecular interactions have a significant effect on the spectra. Next, the electronic structure of bulk TiO2 and of isolated N3 molecules is calculated using the GW approximation and ∆SCF method respectively. For the former, it is shown that including Hubbard U corrections in the initial Hamiltonian reduces the GW gap by 0.4 eV. These calculations are then used to determine the valence photoemission spectrum of the full interface. By including image-charge effects, thermal broadening and configurational disorder, quantitative agreement with experimentally-measured spectra is demonstrated. In addition to the N3/TiO2 system, calculations of the core-level spectra of the interfaces between TiO2 and H2O and bi-isonicotinic acid are also presented. The thesis concludes with a study of the X2Y3/TiO2 interfaces (X=Sb, Bi; Y=S, Se) found in recently-developed semiconductor-sensitized solar cells.
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Urquhart, Andrew J. "Accuracy of low voltage electricity distribution network modelling." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21799.
Full textAbstract:
The connection of high penetrations of new low carbon technologies such as PV and electric vehicles onto the distribution network is expected to cause power quality problems and the thermal capacity of feeder cables may be exceeded. Replacement of existing infrastructure is costly and so feeder cables are likely to be operated close to their hosting capacity. Network operators therefore require accurate simulation models so that new connection requests are not unnecessarily constrained. This work has reviewed recent studies and found a wide range of assumptions and approximations that are used in network models. A number of these have been investigated further, focussing on methods to specify the impedances of the cable, the impacts of harmonics, the time resolution used to model demand and generation, and assumptions regarding the connectivity of the neutral and ground conductors. The calculation of cable impedances is key to the accuracy of network models but only limited data is available from design standards or manufacturers. Several techniques have been compared in this work to provide guidance on the level of detail that should be included in the impedance model. Network modelling results with accurate impedances are shown to differ from those using published data. The demand data time resolution has been shown to affect estimates of copper losses in network cables. Using analytical methods and simulations, the relationship between errors in the loss estimates and the time resolution has been demonstrated and a method proposed such that the accuracy of loss estimates can be improved. For networks with grounded neutral conductors, accurate modelling requires the resistance of grounding electrodes to be taken into account. Existing methods either make approximations to the equivalent circuit or suffer from convergence problems. A new method has been proposed which resolves these difficulties and allows realistic scenarios with both grounded and ungrounded nodes to be modelled. In addition to the development of models, the voltages and currents in a section of LV feeder cable have been measured. The results provide a validation of the impedance calculations and also highlight practical difficulties associated with comparing simulation models with real measurement results.
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Elfving, Gustav, and Emil Jansson. "Modelling extensive solar power production in urban and rural areas." Thesis, Uppsala universitet, Fasta tillståndets fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325004.
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Renewable energy sources, in form of solar power, is a growing source of energy. Not only at an industry level but also at a commercial level. Grid-connected, building-applied solar power has increased rapidly and as the implementation of solar energy grows, so does the importance of being able to evaluate locations that are of interest of installations with respect to its potential production and its impact on the electrical grid. In this thesis the energy production for different future scenarios is modelled for BAPV (Building Applied Photovoltaics) in Uppsala and Herrljunga. This is done by using calculation and simulation programs called MATLAB and ArcGIS. The results regarding Uppsala, are used in a report by BEESG (Built Environment Energy Systems Group) at Uppsala University to the Swedish energy agency. The grid impact of installing extensive solar power as concentrated and dispersed in Herrljunga are simulated and evaluated. Both authors has during the process been equally involved in all parts of the thesis in order to get a thorough understanding of the project as a whole. This due to the fact that the different parts of the thesis were dependent of each other (the second part could not be finished until the first were completed etc).
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Nygren, Anton, and Elin Sundström. "Modelling bifacial photovoltaic systems : Evaluating the albedo impact on bifacial PV systems based on case studies in Denver, USA and Västerås, Sweden." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-55111.
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This study aims to develop a simulation and optimisation tool for bifacial photovoltaic (PV) modules based on the open-source code OptiCE and evaluate dynamic and static albedo impact on a bifacial PV system. Further, a review of the market price development of bifacial PVs' and an optimisation to maximise energy output was conducted. Two case studies with bifacial PV modules, a single-axis tracker in Denver, USA, and a vertical and a tilted system installed at a farm outside Västerås, Sweden, were analysed in this study. The results showed that an hourly dynamic albedo value could provide more accurate simulation results of the rear side irradiance for the bifacial single-axis tracker than a static albedo value. The developed model showed an R2 accuracy of 93% and 91% for the front and rear sides, respectively, when simulated with an hourly albedo value for the bifacial single-axis tracker system. The optimisation was based on weather data from 2020. The results showed that the tilted reference system could increase its energy output by 8.5% by adjusting its tilt from 30° to 54° and its azimuth angle from 0 to -39°. In contrast, the vertical system would increase its energy output by 2.1% by rotating the azimuth angle from -90° to -66°. Conclusions that could be drawn are that bifacial PV price has closed in on the high-performance monofacial PV price the last five years and may continue to decrease in the coming years. Further, it was concluded that detailed dynamic albedo values lead to more accurate simulations of the ground-reflected irradiance. The availability of measured albedo data at the location is essential when the ground-reflected irradiance stands for a significant share of the irradiance. It was determined that during 2020 the optimal configurations of a vertical and tilted bifacial PV system in Västerås would save 11 300 SEK by consuming self-produced electricity and earn 11 600 SEK from selling the surplus of electricity for the farm outside Västerås.
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Barton, John P. "A probabilistic method of modelling energy storage in electricity systems with intermittent renewable energy." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/9727.
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A novel probabilistic method has been developed for modelling the operation of energy storage in electricity systems with significant amounts of wind and solar powered generation. This method is based on a spectral analysis of the variations of wind speed and solar irradiance together with profiles of electrical demand. The method has been embodied in two Matlab computer programs: Wind power only: This program models wind power on any time scale from seconds to years, with limited modelling of demand profiles. This program is only capable of modelling stand-alone systems, or systems in which the electrical demand is replaced by a weak grid connection with limited export capacity. 24-hours: This program models wind power, solar PV power and electrical demand, including seasonal and diurnal effects of each. However, this program only models store cycle times (variations within a time scale) of 24 hours. This program is capable of modelling local electrical demand at the same time as a grid connection with import or export capacity and a backup generator. Each of these programs has been validated by comparing its results with those from a time step program, making four Matlab programs in total. All four programs calculate the power flows to and from the store, satisfied demand, unsatisfied demand and curtailed power. The programs also predict the fractions of time that the store spends full, empty, filling or emptying. The results obtained are promising. Probabilistic program results agree well with time step results over a wide range of input data and time scales. The probabilistic method needs further refinement, but can be used to perform initial modelling and feasibility studies for renewable energy systems. The probabilistic method has the advantage that the required input data is less, and the computer run time is reduced, compared to the time step method.
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Tatsiankou, Viktar. "Instrumentation Development for Site-Specific Prediction of Spectral Effects on Concentrated Photovoltaic System Performance." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31222.
Full textAbstract:
The description of a novel device to measure the spectral direct normal irradiance is presented. The solar spectral irradiance meter (SSIM) was designed at the University of Ottawa
as a cost-effective alternative to a prohibitively expensive field spectroradiometer (FSR). The latter measures highly-varying and location-dependent solar spectrum, which is essential for accurate characterization of a concentrating photovoltaic system’s performance. The SSIM measures solar spectral irradiance in several narrow wavelength bands with a combination of photodiodes with integrated interference filters. This device performs spectral measurements at a fraction of the cost of a FSR, but additional post-processing is required to deduce the
solar spectrum. The model was developed to take the SSIM’s inputs and reconstruct the
solar spectrum in 280–4000 nm range. It resolves major atmospheric processes, such as air mass changes, Rayleigh scattering, aerosol extinction, ozone and water vapour absorptions.
The SSIM was installed at the University of Ottawa’s CPV testing facility in September,
2013. The device gathered six months of data from October, 2013 to March, 2014.
The mean difference between the SSIM and the Eppley pyrheliometer was within ±1.5%
for cloudless periods in October, 2013. However, interference filter degradation and condensation negatively affected the performance of the SSIM. Future design changes will improve the longterm reliability of the next generation SSIMs.
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Noori, Keian. "Energy-level alignment at organic and hybrid organic-inorganic photovoltaic interfaces." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d1b2a4e9-a5d6-4843-b172-6d83dea8a6cb.
Full textAbstract:
Organic and hybrid organic-inorganic photovoltaic (PV) devices have the potential to provide low-cost, large scale renewable energy. Despite the tremendous progress that has been made in this field, device efficiencies remain low. This low efficiency can be partly attributed to the low open-circuit voltages (Voc) generated by organic and hybrid organic-inorganic PV devices. The Voc is critically determined by the energy-level alignment at the interface between the materials forming the device. In this thesis we use first-principles methods to explore the energy-level alignment at the interfaces between the conjugated polymer poly(3-hexylthiophene) (P3HT) and three electron acceptors, zinc oxide (ZnO), gallium arsenide (GaAs) and graphene. We find that Voc reported in the literature for ZnO/P3HT devices is significantly lower than the theoretical maximum and that the interfacial electrostatic dipole plays an important role in the physics underlying the charge transfer at the heterojunction. We note significant charge transfer from the polymer to the semiconductor at GaAs/P3HT interfaces, and use this result to help interpret experimental data. Our findings support the conclusion that charge transferred from P3HT to GaAs nanowires can passivate the surface defect states of the latter and, as a result, account for the observed decrease in photoluminescence lifetimes. Finally, we explore the energy-level alignment at the graphene/P3HT interface and find that Voc reported for experimental devices is in line with the theoretical maximum. The effect of functionalised graphene is also examined, leading to the suggestion that functionalisation might have important consequences for device optimisation.
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Sahli, Mehdi. "Simulation and modelling of thermal and mechanical behaviour of silicon photovoltaic panels under nominal and real-time conditions." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAD036.
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Le travail présenté dans cette thèse porte sur le développement d’un modèle multi-physique numérique, destiné à étudier le comportement optique, électrique et thermique d’un module photovoltaïque. Le comportement optique a été évalué en utilisant des chaines de Markov. Le comportement électrique est obtenu pour les panneaux en Silicium à l’aide d’une méthode d’optimisation numérique. Le comportement thermique est développé en 1D sur l’épaisseur du module, et le modèle multi-physique a été faiblement couplé sous MATLAB. Le comportement sous des conditions nominales d’opération a été validé en utilisant les données déclarées par les constructeurs. Ce modèle a été utilisé pour effectuer une étude paramétrique sur l’effet des irradiances solaires en régime permanent. Le modèle a été validé pour des conditions d’utilisations réelles en comparant avec des mesures expérimentales de température et de puissance électrique. Une étude thermomécanique en 2D sous ABAQUS/CAE et se basant sur le modèle multi-physique a été effectué en conditions nominales d’opération, ainsi qu’en cycle de fatigue selon la norme 61215 pour prédire les contraintes qui sont imposées sur le panneau dans les deux cas mentionnés précédemmentThe work presented in this thesis deals with the development of a numerical multi-physics model, designed to study the optical, electrical and thermal behaviour of a photovoltaic module. The optical behaviour was evaluated using stochastic modelling based on Markov chains, whereas the electrical behaviour was drawn specifically for Silicon based photovoltaic panels using numerical optimization methods. The thermal behaviour was developed in 1D over the thickness of the module, and the multi-physics module was weakly coupled in MATLAB. The behaviour of commercial panels under nominal operation conditions was validated using data declared by the manufacturers. This model was used to perform a parametric study on the effect of solar irradiances in steady state. It was also validated for real use conditions by comparing it to experimental temperature and electrical power output. A thermomechanical study in 2D in ABAQUS/CAE based in the multi-physics model was carried out in nominal operating conditions, as well as in fatigue thermal cycling according to the IEC 61215 Standard to predict the stresses that are imposed on the panel
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Manshaei, Leila. "Modelling of Photovoltaic power plantsin SIMPOW." Thesis, KTH, Elektriska energisystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121150.
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This master thesis project represents an improved model of a grid connected three phase, singlestage PV system implemented in SIMPOW program. The proposal model consists of a PVgenerator employing a PWM converter in order to interface the AC network. The main objectiveof the project is to introduce the main components of the represented model as well as therequired controller schemes. In order to achieve the accurate performance of the PV system withrespect to the integration grid, both AC and DC side network are equipped with controllerfacilities, optimizing the system operation. The control facilities, implemented on the DC side,are mainly focusing on regulation of the output DC voltage of the generator depending on therequirements of the system. The newly proposal MPPT model represents an improvedoptimization strategy for the DC voltage extraction corresponding to various environmentalconditions. The AC side controllers are designed considering the PV system dynamiccontribution on the grid as well as its participation in reactive power provision to the network. Tostudy the accuracy of the dynamic operation of the system, several case studies have beenperformed on AC and DC side. The results of those studies have been discussed considering theirsimulation diagrams.
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Schweizer, Christian. "Modelling photovoltaic systems in urban environments." Thesis, De Montfort University, 2000. http://hdl.handle.net/2086/4822.
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Arnaud, Marc-Alexandre Dimitri. "Modélisation multi-échelle de polymères conjugués pour le photovoltaïque organique : confrontation expérience / théorie." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3053/document.
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Ce travail de recherche prédictive, couplé à des synthèses expérimentales, a pour but d'anticiper la bonne adéquation entre un nouveau polymère donneur de type P3HT et un composé accepteur innovant à base de graphène. Cette étude a notamment porté sur i) la bande d'absorption du polymère donneur « low band gap », ii) sa robustesse face à la dégradation (cristallinité, résistance à l'oxydation), iii) la modulation des propriétés électroniques d'un dérivé de graphène (accepteur) en adéquation avec le donneur. Les résultats montrent que les polythiophènes ayant un substituant éther OR permettent l'amélioration de la conjugaison, de la rigidité, de la cristallinité et de la photostabilité tout en étant électroniquement compatible avec l'hexabenzocoronène fonctionnalisé (acide caorboxylique). De plus, ce nouvel accepteur sera pleinement compatible avec une électrode de graphite grâce à sa prédisposition à l'empilement colonnaireThis predictive research work, combined with an experimental study, aims at anticipate the behavior of a new donor :acceptor pair constituted by a P3HT-type of polymer and an innovative graphene-based acceptor material (HBC). This study is particularly interested in i) the absorption band of the donor (a « low band gap » polymer) and ii) its resistance towards degradation (cristallinity, oxidation stability), and finally iii) the modulation of the electronic properties of the acceptor, in keeping with those of the donor. Results show that polythiophenes grafted with an –OR group improve both conjugation, rigidity, cristallinity and photostability, in addition to their great electronic compatibility with functionalized HBCs. Besides, this new acceptor material will be fully compatible with a graphite electrode, thanks to its columnar structuration
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Vadon, Mathieu. "Extraction de bore par oxydation du silicium liquide pour applications photovoltaïques." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI067/document.
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L'extraction du bore du silicium liquide est une étape d'une chaîne de procédés de purification de silicium de qualité suffisante pour les applications photovoltaïques. Cette thèse étudie en priorité le procédé dit "gaz froid" qui consiste en l'injection d'un mélange de gaz Ar-H2-H2O sur du silicium liquide chauffé électromagnétiquement. Une deuxième méthode similaire ("procédé plasma") où on injecte un plasma thermique issu d'un mélange Ar-H2-O2 a également été étudiée. Un modèle est nécessaire afin d'optimiser le procédé pour économiser de l'énergie.Les trois objectifs du modèle sont la prédiction du flux de silicium issu de la surface (vitesse d'oxydation), du flux de bore issu de la surface (pour avoir la vitesse de purification), et du seuil de passivation. Le seuil de passivation est la limite de concentration d'oxydant au-delà de laquelleil apparait une couche de silice passivante qui empêche la purification. Afin de minimiser la consommation d'énergie en accélérant le procédé, on cherche à injecter une concentration d'oxydant juste en dessous du seuil de passivation.De précédentes études ont montré que le facteur limitant pour les flux de bore et de silicium est le transport d'oxydant dans la phase gaz. Ainsi, nous avons fait un modèle monodimensionnel réactif-diffusif à l'équilibre thermodynamique de la couche limite gazeuse. Selon ce modèle, l'effet de la formation d'aérosols de silice est de diviser par deux le flux d'oxydant vers la surface, ce qui sert aux simulations CFD. Cet effet des aérosols de silice sur les flux d'oxydant peut aussi se retrouver si on enlève l'hypothèse d'équilibre thermodynamique des aérosols de silice avec la phase gaz, ce qui est confirmé par des simulations CFD et des expériences.Pour ce qui concerne l'estimation de la vitesse de purification, les données les plus réalistes concernant l'enthalpie de formation de HBO(g) et le coefficient d'activité du bore dans le silicium liquide ont été sélectionnées. Nous obtenons une bonne prédiction de la vitesse de purification à différentes températures et concentrations d'oxydant, y compris pour le cas plasma que nous avons étudié, en utilisant ces données thermodynamiques et en supposant que les produits de réaction de surface SiO(g) et HBO(g) diffusent de manière similaire. Ces coefficients de transfert identiques pour HBO(g) et SiO(g) peuvent s'expliquer par une précipitation simultanée et commune de HBO(g) et SiO(g), selon des mécanismes de germination et croissance restant à déterminer.Un dispositif expérimental de lévitation électromagnétique de silicium sous un jet oxydant a été monté. La mesure et le contrôle de température d'une bille de silicium ont été mis en oeuvre ce qui permettra la mesure sans contaminations de données thermodynamiques concernant les impuretés .Le seuil de passivation mesuré sur quelques expériences disponibles peut être prédit par notre modèle d'oxydation (associé au facteur deux représentant les aérosols de silice), si on l'associe à un critère proposé dans la littérature, qui couple la fraction du flux d'oxydant arrivant à la surface à une loi d'équilibre entre SiO(g), Si(l) et SiO2(s/l). Nous montrons dans cette thèse que la couche passivante n'est compatible avec des aérosols de silice que si ces aérosols ne sont pas en équilibre avec la phase gaz. La cinétique de formation des aérosols de silice doit donc être étudiée plus en détailsBoron extraction from liquid silicon is a step within a new chain of processes aimed to purify silicon that meets purity requirements specific to photovoltaic applications. This thesis focuses mostly on cold gas processes that involve the injection of a mixture of Ar-H2-H2O gases onto electromagnetically stirred liquid silicon. A second similar method ("plasma processes") that involves the injection of thermal plasma made from an Ar-H2-H2O mixture has also been studied. A model is needed to minimize energy consumption by optimizing the process.We want to be able to predict the flow of silicon from the reactive surface (oxidation speed), the flow of boron from the surface (to have the purification speed) and the passivation threshold. For a given setting, the passivation threshold is the limit oxydant partial pressure at injection beyond which a passivating silica layer appears on the surface of the liquid silicon, which interrupts the purification. In order to minimize the energy consumption, and for that matter , in order to speed up the process, we want to inject oxydant in a quantity just below the passivation threshold.Previous studies have shown that the limiting factor for the oxidation and purification speed is the transport of oxidant in the gas phase. That's why we have made a 1D reactive-diffusive model at thermodynamical equilibrium of the gaseous boundary layer. According to this model the effect of the formation of silica aerosols is to divide by two the flow of oxydant towards the surface, which is useful for the simplification of CFD simulations. This effect of the formation of silica aerosols on oxidant flows can also be found without the hypothesis of thermodynamical equilibrium of silica aerosols with the gas phase, as confirmed by simulations and experiments.Regarding the estimation of the purification speed, we have selected the most realistic values of the enthalpy of formation of HBO(g) and of the activity coefficient of boron in liquid silicon.We could get good estimates of the purification speed at different temperatures and levels of oxidant concentrations at injection, by using the selected thermodynamical values and by supposing that the surface reaction products HBO(g) and SiO(g) diffuse similarly. A reason for this similar diffusion of SiO(g) and HBO(g) might be a common and simultaneous precipitation , due to specific dynamics of nucleation and growth that need to be investigated further. Those results for cold gas processed could also be obtained for a plasma experiment.However for the plasma experiment, silica aerosols can be formed only in a very thin layer near the surface and this result needs confirmation from other experiments.Temperature measurement and control for electromagnetically levitating liquid silicon under a flow of oxidant were achieved. With more time, quantitative results could be achieved to measure thermodynamical data on impurities without contaminations.Regarding the prediction of the passivation threshold, we justified a thermodynamical equilibrium at surface of SiO(g) with Si(l) and SiO2(s/l) at passivation threshold with the spreading of silica particles over the liquid silicon surface with the stirring. We show that the passivation layer is compatible with silica aerosols only if those aerosols are not in equilibrium with the gas phase. Therefore the kinetics of formation of silica aerosols should be studied further. A previous empirical formula on the prediction of the passivation threshold for experiments where H2O is the oxidant has been confirmed using our CFD model. A passivation experiment has shown the absence of impact of silica aerosols on oxidant transport when the oxidant is O2
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Gow, John A. "Modelling, simulation and control of photovoltaic converter systems." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/6871.
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The thesis follows the development of an advanced solar photovoltaic power conversion system from first principles. It is divided into five parts. The first section shows the development of a circuit-based simulation model of a photovoltaic (PV) cell within the 'SABER' simulator environment. Although simulation models for photovoltaic cells are available these are usually application specific, mathematically intensive and not suited to the development of power electronics. The model derived within the thesis is a circuit-based model that makes use of a series of current/voltage data sets taken from an actual cell in order to define the relationships between the cell double-exponential model parameters and the environmental parameters of temperature and irradiance. Resulting expressions define a 'black box' model, and the power electronics designer may simply specify values of temperature and irradiance to the model, and the simulated electrical connections to the cell provide the appropriate I/V characteristic. The second section deals with the development of a simulation model of an advanced PVaware DC-DC converter system. This differs from the conventional in that by using an embedded maximum power tracking system within a conventional linear feedback control arrangement it addresses the problem of loads which may not require the level of power available at the maximum power point, but is also able to drive loads which consistently require a maximum power feed such as a grid-coupled inverter. The third section details a low-power implementation of the above system in hardware. This shows the viability of the new, fast embedded maximum power tracking system and also the advantages of the system in terms of speed and response time over conventional systems. The fourth section builds upon the simulation model developed in the second section by adding an inverter allowing AC loads (including a utility) to be driven. The complete system is simulated and a set of results obtained showing that the system is a usable one. The final section describes the construction and analysis of a complete system in hardware (c. 500W) and identifies the suitability of the system to appropriate applications.
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Wang, Yimin. "Modelling physical location based factors of photovoltaic viability." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6367/.
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The aim of this thesis is to model physical location based factors of photovoltaic (PV) viability, including geographical location, dominated climate factors, urban terrain shading and PV panel technologies. We analyze ground measurements from thirteen UK Met Office British weather stations, and ten further weather stations in the US operated by National Solar Radiation Data Base for evidence of climatic effects on annual and seasonal solar radiation over the last 40 years. The impact of the North Atlantic Oscillation on winter solar radiation in the British Isles is explored. We evaluate the accuracies of four solar radiation models - the PVGIS model, UKCP09 model, Liu and Jordan model and Page model - against ground measurements from these thirteen UK Met Office British weather stations. A three-dimensional (3D) SOlar RAdiation Model (SORAM) is presented for evaluating the potential direct and diffuse solar radiation aggregated at a point location in an urban area. By using ray-tracing algorithm, SORAM is capable of taking into account terrain shading. We also present a mobile application that has the same aim as SORAM. However, instead of using a 3D city map, the embedded shading detection algorithm is based on image processing. An analytical model of externally-coated, rectangular and cylindrical luminescent solar concentrators (LSCs) have been developed. These LSCs are able to estimate the residual intensity as a function of wavelength, concentration of luminescent dye and device dimension.
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Bisconti, Raffaella. "Optical modelling and optimisation of Spheral Solar'T'M Cells." Thesis, Northumbria University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245206.
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Adkins, Deborah Anne. "Experimental and numerical modelling of mid-concentration photovoltaic concentrator systems." Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594866.
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For photovoltaics to achieve wide-scale implementation it is essential that their cost is reduced while maintaining or exceeding the present level of solar to electrical conversion performance. Concentrating solar energy onto a photovoltaic cell allows a reduction in the output electricity cost, if the cost of the concentrator is less than that of the displaced photovoltaic materials. Photovoltaic cell efficiency is shown to decrease with increasing temperature, causing the photovoltaic cells to exhibit both short-term (efficiency loss) and long term (irreversible damage) degradation due to excessive temperatures. Hence the analysis of thermal management is an important issue in photovoltaic power generating systems for both one-sun (lx) and concentrated applications. This thesis presents an experimental and numerical study of solar cell temperature in a midconcentration silicon photovoltaic concentrator (CPV), with a geometric concentration ratio of 42X. Experimental and computational fluid dynamic (CFO) modelling of heat transfer in six designs of CPV device is carried out. A detailed experimental study was designed and carried out in order to investigate the temperature and initial boundary conditions of the two initial CPV prototypes, with a without passive cooling arrangements, operating under standard test conditions (STC) in conjunction with the effect of environmental variables, namely the irradiance incident on the plane-of-array of the CPV module, the local wind speed and the ambient temperature on the operating temperatures of the CPV prototypes. The operating temperature is shown to depend strongly on the irradiance, less so on the wind speed and is found to be insensitive to short term fluctuations in ambient temperature. Temperature profiles of the CPV prototypes were measured experimentally with thermocouples placed both internally and externally along the enclosure and walls aJong the length of each CPV module. To investigate the performance of the CPV devices under a fixed set of repeatable environmental conditions, a solar simulator was designed and built to facilitate indoor testing at a range of illumination levels (0 to 1000W 1m2) and environmental conditions. Reviewing the results it was found that the spectrum and uniformity of irradiance source incident the plane of a single module (1 x 0.lm) is of great importance. The solar simulator was also found to artificially increase the module operating temperature, with greater temperatures recorded during indoor testing. Wind speed and direction measurements were taken in order to establish the module convective heat transfer coefficient (CHTC) which was determined to relatively insensitive to wind direction and to be a power law function of the mean wind speed. In the second phase of the work, three dimensional numerical studies of the photovoltaic concentrator prototypes were developed using ANSYS Fluent Computational Fluid Dynamic (CFD) software to solve the mass, momentum and energy transfer governing equations. The simulations provided thermal and dynamic maps of the fluid flow and the heat transfer between the cell and the passive cooling systems. The results show that a maximum of seven radial fins (CPV design 3) of 27mm height, 3.3mm thickness with a 4 degree taper can be effectively used to reduce the solar cell temperature, from 97.8"C with no cooling fins to 67.7"C with seven fins, measured at nominal operating cell temperature (NOCT) conditions. In addition. to validate the model. experimental measurements of temperature and flow characteristics are compared with experimental data. Numerical results of the CPV operating temperature are shown to have a strong correlation with experimental data with a maximum 0.3% deviation from experimental data for prototype one and a maximum 1.5% deviation from experimental data for prototype two. Simulation models are shown to be important design tools for predicting a photovoltaic concentrator's experimental and real world performance. Informed design decision making and optimisation is a significant goal of this work.
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Aseeri, Ahmed. "Modelling and simulation of fuel cell/photovoltaic hybrid power system." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/8280.
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Due to an ever increasing demand for power consumption and a rising public awareness of the impact on the environment, renewable energy based on Hybrid Power Systems (HPS) (e.g. fuel cell, wind or solar) to supply electricity has attracted a growing research interest. Photovoltaic (PV) power generation systems are among the most promising renewable energy technology solutions. Fuel Cell (FC), on the other hand, is emission-free and quieter than hydrocarbon fuel-powered engines. It saves fuel and is cleaner for the environment. Such systems can generate electricity from clean sources to power loads located in inaccessible or remote areas.
The aim of this thesis is to investigate the potential for utilising an FC/PV hybrid power system to provide power for a water pump, which supply an elevated water tank (6,500 litres/day consumption) to a small community located in a remote area. The HPS consists of a photovoltaic solar panel, a 1.2 KW Nexa Proton Exchange Membrane Fuel Cell (PEMFC), a Lead acid battery bank, a bidirectional DC/DC converter, one directional DC/DC converter and a water pump. The thesis will commence with a literature review, giving an overview of energy demand and future trend, describing the different HPS configurations and giving some examples of similar projects carried out by other researchers and organisations. A system component description is also covered. The thesis will then move on to describing the HPS simulation model development using Matlab/Simulink simulation environment, concluding with the test cases used to validate the model based on the 1.2 KW Nexa PEMFC and PV panels.
In the case study, the system utilizes photovoltaic (PV) as the primary power generator, PEMFC as the secondary back-up power generator and a battery bank (to store any excess power) as power storage device. The advantage of the proposed system is that, in addition to being environmentally friendly, it also has lower maintenance costs, noise and carbon footprint. Two main scenarios were explored to validate the hybrid system performance, at two different geographical and environmental conditions.
The first case is based in Saudi Arabia, where it is hot and sunny for most of the year. This scenario permits higher utilization of the power generated from the PV cells and reduces the dependence on power produced by the fuel cell. The second case scenario is based in the UK, where it is cold and cloudy for most of the year. The Sunlight here is at minimum, leading to higher dependence on the fuel cells for the system operation.
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Black, Jonathan Paul. "Mathematical modelling of electronic contact mechanisms in silicon photovoltaic cells." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:ff671215-5f05-4ef0-a876-3f474a8450c9.
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In screen-printed silicon-crystalline solar cells, the contact resistance of a thin interfacial glass layer between the silicon and the silver electrode plays a limiting role for electron transport. The motivation of this project is to gain increased understanding of the transport mechanisms of the electrons across this layer, which can be exploited to provide higher performance crystalline silicon solar cells. Our methodology throughout is to formulate and analyse mathematical models for the electron transport, based on the drift diffusion equations. In the first chapter we outline the problem and provide a summary of relevant theory. In Chapter 2 we formulate a one-dimensional model for electron transport across the glass layer, that we solve both numerically and by employing asymptotic techniques. Chapter 3 extends the model presented in Chapter 2 to two dimensions. To solve the two-dimensional model numerically we devise and validate a new spectral method. The short circuiting of current through thinner regions of the glass layer enables us to find limiting asymptotic expressions for the average current density for two different canonical glass layer profiles. In Chapter 4 we include quantum mechanical effects into the one-dimensional model outlined in Chapter 2 and find that they have a negligible effect on the contact resistance of the glass layer. We model the boundary effects present at the silicon emitter-glass interface in Chapter 5. Finally, in Chapter 6 we summarise our key results, suggest possible future work, and outline the implications of our work to crystalline silicon solar cell manufacturers.
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Czekala, Piotr. "Modelling of molecules on surfaces and thin-film photovoltaic absorbers." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/16755/.
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In this thesis a range of phenomena related to molecular adsorption on silicon surfaces is investigated. The majority of the studies are performed in response to experimental results, where, using newly developed methods within the framework of density functional theory, we aim to elucidate some of the underlying physics as well as test the performance of the chosen methodology. The studies cover a range of subjects such as molecularly mediated pinning of surface geometry, single molecular adsorptions, molecule migration via exited states and finally an analysis of coverage dependent adsorption phenomena, where interactions between molecules are mediated by the surface or enacted via dipole interactions. The main molecules of our simulations were water, ethylene, acetylene, and benzene, as well as halogenated hydrocarbons. We studied processes at two different surfaces, the Si(111)-7 x 7 surface, and the Si(100)-c(4 x 2) surface. Finally we simulated and characterized one type of grain boundary observed experimentally for a set of photovoltaic absorbers (CuInSe_{2}) and kesterite and stannite(Cu_{2}ZnSnSe_{4} or Cu_{2}ZnSnS_{4}) in order to resolve the open question of how these grain boundaries influence efficiencies of the photovoltaic device.
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Syres, Karen Louise. "Molecular adsorption on TiO2 surfaces : modelling potential biomedical and photovoltaic devices." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/molecular-adsorption-on-tio2-surfaces-modelling-potential-biomedical-and-photovoltaic-devices(14c1f1a6-7650-43e2-b8cc-9c9e102f6923).html.
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This thesis describes molecular adsorption on single crystal anatase (101) and rutile (110) TiO2 surfaces and TiO2 nanoparticles using photoemission and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. DFT calculations were carried out in order to complement the experimental data. The adsorption of dopamine and pyrocatechol on single crystal TiO2 surfaces was investigated with photoemission and NEXAFS and indicates the molecules adsorb in a bidentate mode following deprotonation of the hydroxyl groups. NEXAFS analysis of pyrocatechol adsorption on the rutile (110) and anatase (101) TiO2 surfaces shows the plane of the aromatic ring to be oriented at 23˚±8˚ and 27˚±6˚ from the surface normal, respectively. Dopamine adsorbed on the anatase TiO2 (101) surface was found to adsorb with the plane of the ring approximately normal to the surface. Adsorption of pyrocatechol and dopamine on anatase TiO2 (101) gave rise to a feature below the main pi* peak, not observed when pyrocatechol was adsorbed on rutile TiO2 (110). This feature was replicated in DFT calculations of both dopamine and pyrocatechol adsorbed on an anatase TiO2 cluster, but was not present in calculations of the free molecules. The new states are found to be located on the TiO2 surface, which may allow direct charge-transfer from the molecule to the surface. Simulated NEXAFS spectra from the cluster showed good agreement with the experimental data in the pi* region for the molecule-anatase TiO2 (101) system. The rutile experimental data showed good agreement with calculations of the free molecule in terms of the pi* peak separation. Charge-transfer studies of pyrocatechol adsorbed on the rutile TiO2 (110) surface indicate that charge-transfer could be occurring from the LUMO, LUMO+1 and LUMO+2 in the pyrocatechol molecule. The charge transfer time for this system was found to be < 9.0 ± 2.0 fs. XPS results for functionalised TiO2 nanoparticles show that dopamine (DA) molecules adsorb intact and bond through both oxygen atoms. The attachment of PEG (polyethylene glycol) and Pluronic was investigated. PEGme-DA (terminated with methyl) and DA-PEG-DA showed attachment to the nanoparticles occurs through one end of the chain. DA-Pluronic-DA may attach through both DA molecules but this could not be proved conclusively. Adsorption of malonic acid on rutile TiO2 (110) showed that the molecule degraded under the synchrotron beam and formed acetate and/or formate. It was found that dipping this surface into a ruthenium di-2,2'-bipyridyl-4,4'-dicarboxylic acid diisocyanate-dye solution in air appeared to displace the adsorbed species, replacing them with the dye.
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Zarmai, Musa Tanko. "Modelling of solder interconnection's performance in photovoltaic modules for reliability prediction." Thesis, University of Wolverhampton, 2016. http://hdl.handle.net/2436/617782.
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Standard crystalline silicon photovoltaic (PV) modules are designed to continuously convert solar energy into electricity for 25 years. However, the continual generation of electricity by the PV modules throughout their designed service life has been a concern. The key challenge has been the untimely fatigue failure of solder interconnections of solar cells in the modules due to accelerated thermo-mechanical degradation. The goal of this research is to provide adequate information for proper design of solar cell solder joint against fatigue failure through the study of cyclic thermo-mechanical stresses and strains in the joint. This is carried-out through finite element analysis (FEA) using ANSYS software to develop the solar cell assembly geometric models followed by simulations. Appropriate material constitutive model for solder alloy is employed to predict number of cycles to failure of solder joint, hence predicting its fatigue life. The results obtained from this study indicate that intermetallic compound thickness (TIMC); solder joint thickness (TSJ) and width (WSJ) have significant impacts on fatigue life of solder joint. The impacts of TIMC and TSJ are such that as the thicknesses increases solder joint fatigue life decreases. Conversely, as solder joint width (WSJ) increases, fatigue life increases. Furthermore, optimization of the joint is carried-out towards thermo-mechanical reliability improvement. Analysis of results shows the design with optimal parameter setting to be: TIMC -2.5μm, TSJ -20μm and WSJ -1000μm. In addition, the optimized model has 16,264 cycles to failure which is 18.82% more than the expected 13,688 cycles to failure of a PV module designed to last for 25 years.
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Sokolov, Michael. "Small-signal modelling of maximum power point tracking for photovoltaic systems." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39348.
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In grid connected photovoltaic (PV) generation systems, inverters are used to convert the generated DC voltage to an AC voltage. An additional dc-dc converter is usually connected between the PV source and the inverter for Maximum Power Point Tracking (MPPT). An iterative MPPT algorithm searches for the optimum operating point of PV cells to maximise the output power under various atmospheric conditions. It is desirable to be able to represent the dynamics of the changing PV power yield within stability studies of the AC network. Unfortunately MPPT algorithms tend to be nonlinear and/or time-varying and cannot be easily combined with linear models of other system elements. In this work a new MPPT technique is developed in order to enable linear analysis of the PV system over reasonable time scales. The new MPPT method is based on interpolation and an emulated-load control technique. Numerical analysis and simulations are employed to develop and refine the MPPT. The small-signal modelling of the MPPT technique exploits the fact that the emulated-load control technique can be linearised and that short periods of interpolation can be neglected. A small-signal PV system model for variable irradiation conditions was developed. The PV system includes a PV module, a dc-dc boost converter, the proposed controller and a variety of possible loads. The new model was verified by component-level time-domain simulations. Be cause measured signals in PV systems contain noise, it is important to assess the impact of that noise on the MPPT and design an algorithm that operates effectively in pr esence of noise. For performance assessment of the new MPPT techniques, the efficiencies of various MPPT techniques in presence of noise were compared. This comparison showed superiority of the interpolation MPPT and led to conclusions about effective use of existing MPPT methods. The new MPPT method was also experimentally tested.
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Ebrahim, Mila. "Performance Evaluation of a Photovoltaic/Thermal (PVT) Collector with Numerical Modelling." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302122.
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In Photovoltaic/Thermal (PVT) technology, both PV and solar thermal technology are integrated in the same module for simultaneous electricity and heat production. Research has shown that there are multiple benefits from integrating PVT collectors with a ground source heat pump (GSHP) system, since it allows for seasonal storage of thermal energy over the year. Furthermore, it leads to reduced operating temperatures for the PVT collectors which can increase efficiency and lifetime. The aim of this study is to present the electric and thermal performance of a PVT collector developed by Solhybrid i Småland AB, for different environmental and fluid inlet conditions that can occur when PVT collectors are connected to a GSHP system. Furthermore, the performance of this PVT design is evaluated with ASHRAE (Standard 93-2003), to allow for comparison with other PVT collector designs, with values on the overall heat loss coefficient (UL) and heat removal factor (FR). The modelling tool used for the study is the software COMSOL Multiphysics, which uses the finite element method to solve the partial differential equations in heat transfer and fluid flow problems. Based on the performance curves, the thermal and electrical efficiency of the collector is approximately 48.0-53.4% and 19.0-19.2% respectively at a reduced temperature of zero and irradiance levels of 800-1000 W/m2 for the mass flow rate of 0.026 kg/sm2 which was determined as most suitable to increase thermal performance. Furthermore, these results resulted in a heat removal factor (FR) and overall heat loss coefficient (UL) of 0.56-0.62 and 53.4-53.5 W/m2 K respectively. The results on the performance of the PVT collector in different weather conditions shows that the inlet water temperature can significantly affect operating time and the amount of thermal energy that can be extracted during the year, especially if the collector operates in a colder climate like Sweden. To assess the accuracy of the created model, future work includes experimental testing of the studied PVT collector.En panel med kombinerad teknik av både solceller och termisk solfångare (PVT) kan producera både elektricitet och värme samtidigt. Forskning har visat att det kan finnas flera fördelar med att integrera PVT-paneler med ett bergvärmesystem, eftersom det mjliggör lagring av termisk energi över året. Dessutom leder ett sådant system till lägre drifttemperaturer som kan öka PVT-panelens effektivitet och livslängd. Syftet med studien är att presentera den elektriska och termiska prestandan av en PVT-panel utvecklat av Solhybrid i Småland AB för olika driftförhållanden som kan uppstå på grund av olika väderförhållanden och inlopps-temperaturer när panelerna är kopplade till ett bergvärmesystem. Vidare utvärderas prestandan för denna panel med ASHRAEmetoden (standard 93-2003), för att möjliggöra jämförelse med andra PVT-paneler. Modelleringsverktyget som använts i studien är mjukvaran COMSOL Multiphysics, som använder finita elementmetoden för att lösa partiella differentialekvationer i värmeöverförings-och flödesproblem. Baserat på prestandakurvorna som presenteras i resultatet, är den termiska och elektriska verkningsgraden approximativt 48.0-53.4% respektive 19.0-19.2% för en reducerad temperatur med värdet noll, en solstrålning mellan 800-1000 W/m2, för en massflödeshastighet på 0.026 kg/sm2 som beslutades som den mest lämpliga för att öka den termiska prestandan. Resultaten resulterade i en värmeavledningsfaktor (FR) och total värmeförlustkoefficient (UL) på 0.56-0.62 respektive 53.4-53.5 W/m2 K. Resultaten på PVT-panelens prestanda under olika väderförhållanden visar att vattnets inloppstemperatur kan påverka drifttiden och mängden termisk energi som kan extraheras under året avsevärt, speciellt i nordiskt klimat. För att bedöma korrektheten i resultaten och den skapade modellen rekommenderas experimentell testning av den studerade PVT-panelen.
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Brivio, Federico. "Atomistic modelling of perovskite solar cells." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.698992.
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This thesis focuses on the study of hybrid perovskites properties for the purposes of photovoltaic applications. During the almost four years PhD project that has lead to this thesis the record photovoltaic efficiency for this technology has in- creased from 10.9% to 22.1%. Such a significant pace of development can be com- pared with few other materials. It is for this reason that hybrid perovsites have at- tracted impressive research efforts. We approached the study of such unique ma- terials using computational ab-initio techniques, and in particular Density Func- tional Theory. We considered different materials, but most of the attention was concentrated on MAPI (CH 3 NH 3 PbI 3 ). The results are divided in three chapters, each exploring a different material prop- erty. The first chapter reports the electronic structure of the material bulk, sur- faces, and other electronic-related properties such as the rotation barrier for the organic component and the Berry phase polarization. The second chapter focuses on the vibrational properties primary employing the harmonic approximation but also extends to the quasi-harmonic approximation. The outcome of these calculations permitted us to calculate theoretical IR and Ra- man spectra which are in good agreement with different experimental measure- ments. The quasi-harmonic approximation was used to calculate temperature dependent properties, such as the Grüneisen parameter, the thermal dependence of heat capacity and the thermal volumetric expansion. The third and last chapter reviews the thermodynamic properties of binary halide compounds. The cobination of ab-initio calculations with the generalised quasi- chemical approximation has allowed to study the stability of mixed composition perovskites. The results certified a set of stable structures that could stand at the base of observed phenomena of photo-degradation of hybrid perovskite based devices. All three chapters have been written to understand the chemical and physical behaviour of hybrid perovskites and to extended and contribute to the under- standing of experimental work.
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Lam, King-hang. "Techniques for dynamic modelling of BIPV in supporting system design and BEMS." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558460.
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Quintana, Samer. "Building integrated photovoltaic (BIPV) modelling for a demo site in Ludvika based on building information modelling (BIM) platform." Thesis, Högskolan Dalarna, Energiteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:du-29078.
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This thesis aims to design and simulate a building integrated photovoltaic (BIPV) system for three demo buildings in Ludvika, Sweden, which is part of the Energy- Matching’s project under the European H2020 research scheme. A literature review was firstly conducted in the area of energy scenarios, engineering tools, methodologies and the workflows in design and building energy modelling. Then, this thesis developed the three-dimensional (3D) building models of the demo site, based on the Revit – a building information modelling (BIM) tool. Next, the PVSITES tool was considered as the main approach to simulate and optimize the BIPV system. Results on the energy output of the dedicated BIPV system, as well as financial costs, were finally obtained. It was found that the optimal location for the BIPV system was on the three buildings south and east faced roofs, with a total area of approximately 800 meters squared (m2) and a yearly irradiance potential between 1020 kilowatts hours per meter squared (kWh/m2) and 925 kWh/m2 respectively. The simulation showed that this BIPV system of 615 m2 with a power of 36 kilowatts-peak (kWp) could yield a maximum of 29,000 kilowatts hours per year (kWh), a 5% of the total yearly energy demand of the building and over the summer, this percentage increases considerably. With the estimated standards costs, the BIPV system have a 12 years payback period and 61% investment ratio over a 20 years period, concluding that a BIPV system on the Ludvika demo building is a feasible project, in terms of energy potential and as well as economically. This thesis also concludes that performing the BIPV simulation on the BIM platform is both reliable and flexible, and also has the potential to be reused, refined and scaled up.
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Martin, C. M. "Modelling the Effect of the Interface Morphology in Organic-Inorganic Photovoltaic Devices." Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504434.
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Braun, Felix Maximilian. "Modelling of light-trapping structures and their application in organic photovoltaic devices." Thesis, University College London (University of London), 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437362.
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Chiodetti, Matthieu. "Bifacial PV plants: performance model development and optimization of their configuration." Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-172516.
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Bifacial solar modules can absorb and convert solar irradiance to current on both their front side and back side. Several elements affects the bifacial yield, especially the ground albedo around the system or the installation configuration. In this document, investigations carried out at EDF R&D facilities regarding the use of bifacial modules in large scale PV farm are presented. Tests on the outdoor facilities were conducted to validate and improve a bifacial stand model developed under a Dymola/Modelica environement. Furthermore, a global optimization method was implemented to determine the optimal configuration of a large bifacial plant with modules facing south. Investigations showed the importance of a new albedo model to accurately evaluate the irradiance received on the rear side. The new model shows a relative error on the rear irradiance under 5% when compared with experimental data. Techno-economical optimization of a bifacial plant was conducted at different locations and for different ground albedo. The results shows that the gain on the specific production can vary between 7.2 and 14.2% for a bifacial plant when compared with a monofacial plant. Bifacial plants are expected to become more profitable than monofacial plants in some of the cases tested when their module cost will reach 68 c€/Wp.
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Fialho, Luís André Pereira. "Photovoltaic generation with energy storage integrated into the electric grid: modelling, simulation and experimentation." Doctoral thesis, Universidade de Évora, 2019. http://hdl.handle.net/10174/25361.
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Esta tese apresenta o trabalho e resultados da investigação desenvolvida sobre conversão fotovoltaica com armazenamento de energia integrado em rede elétrica. Começa por apresentar a modelação, simulação e validação da conversão fotovoltaica e inversores com injeção para a rede. Descreve também seguidamente o processo de conceção, construção, comissionamento e desenvolvimento experimental das infraestruturas hoje existentes na Cátedra Energias Renováveis da Universidade de Évora, no que diz respeito às duas microgrids desenvolvidas no âmbito do projeto europeu PVCROPS. Estas microgrids são compostas, de forma geral, por um elemento de produção fotovoltaica, um elemento de armazenamento de energia, uma ligação à rede e um sistema de controlo e datalogging. Relativamente ao armazenamento de energia, esta tese aborda e caracteriza ainda as duas tecnologias instaladas: a bateria de iões de lítio e a bateria de fluxo redox de vanádio. Estas microgrids servem assim para implementação e validação de uma estratégia de gestão de energia tendo como objetivo a maximização do autoconsumo, cujos conteúdos são apresentados no capítulo 4. Depois das conclusões, no último capítulo, apontam-se ainda as linhas de investigação futuras de maior potencial, na sequência do trabalho desenvolvido e apresentado nesta tese; Photovoltaic generation with energy storage integrated into the electric grid: Modelling, simulation and experimentation
Abstract:
This thesis presents the work and results of the research developed on photovoltaic conversion with energy storage integrated into the electric grid. It begins by presenting the modeling, simulation and validation of the photovoltaic conversion and inverters with injection into the electric grid. It also describes the process of design, construction, commissioning and experimental development of the existing infrastructures in the Renewable Energies Chair of the University of Évora, with respect to the two microgrids developed under the European project PVCROPS. These microgrids are generally composed by a photovoltaic production element, an energy storage element, a grid connection and a control and datalogging system. Regarding energy storage, this thesis also discusses and characterizes the two installed technologies: the lithium-ion battery and the redox-flow vanadium battery. These microgrids thus serve to implement and validate an energy management strategy with the objective of maximizing self-consumption, the contents of which are presented in Chapter 4. Following the conclusions, in the last chapter are pointed the future research lines of greater potential, following the work developed and presented in this thesis.
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Vanden, Eynde Nicholas. "Modelling of a stand alone photovoltaic system with dedicated hybrid battery energy storage system." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/11932.
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Includes abstract.Includes bibliographical references.
The purpose of this thesis project was to model and simulate a stand-alone photovoltaic (PV) plant that utilized the maximum power point tracking (MPPT) technique and included a hybrid battery energy storage system (BESS). The model consisted of five main components namely; the photovoltaic module, maximum power point tracking technique, hybrid battery energy storage system, controller and load.
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Lam, King-hang, and 林勁恆. "Techniques for dynamic modelling of BIPV in supporting system design and BEMS." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558460.
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Boreland, Matt School of Electrical Engineering UNSW. "Laser Crystallisation of Silicon for Photovoltaic Applications using Copper Vapour Lasers." Awarded by:University of New South Wales. School of Electrical Engineering, 1999. http://handle.unsw.edu.au/1959.4/17190.
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Thin film silicon on low temperature glass substrates is currently seen as the best path toreduce the $/W cost of photovoltaic (PV) modules. However, producing thin film polysilicon, on glass, is an ongoing research challenge. Laser crystallisation of a-Si is one of the possible methods. Typically excimer (XMR) lasers are used for laser crystallisation. This thesis introduces the copper vapour laser (CVL) as a viable alternative for thin film photovoltaic applications. The CVL, like the XMR, is a high powered, pulsed laser. However, the CVL has higher pulse rates (4-20kHz), better beam quality and a visible wavelength output (578 & 511nm). Preliminary experiments, using 600K-heated silicon-on-quartz samples, confirmed that CVL crystallisation can produce area weighted average grain size of 0.1-0.15??m, which is comparable to results reported for XMR??? s. Importantly, the CVL results used thicker films (1??m), which is more applicable to thin photovoltaic devices that need 1-10??m of silicon to be viable. The CVL??? s longer wavelength and therefore longer penetration depth (1/alpha) are proffered as the main reason for this result. Extensive laser-thermal modelling highlighted further opportunities specific to CVL crystallisation. Through-the-glass doublesided irradiation was shown in simulations to reduce thermal gradients, which would enhance crystal growth. The simulations also produced deeper melts at lower surface temperatures, reducing the thermal stress on the sample. Subsequent experiments, using silicon-on-glass, confirmed the benefit of through-the-glass doublesided irradiation by maintaining grain sizes without the usual need for substrate heating. Furthermore, Raman analysis showed that doublesided crystallisation achieved full depth crystallisation, unlike single side irradiation which produced partial crystallisation. A new mode of crystallisation, stepwise crystallisation, was also postulated whereby a series of CVL pulses could be used to incrementally increase the crystallisation depth into the silicon. Simulations confirmed the theoretical basis of the concept, with HeNe Raman spectroscopy and analysis of surface grain sizes providing indirect experimental support. The CVL??? s ability to crystallise thicker films more directly applicable to photovoltaic devices secures its viability as an alternative laser for photovoltaic applications. The through-the-glass doublesided irradiation and the stepwise crystallisation provide additional potential for increased process flexibility over XMR???s.
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Lammert, Gustav [Verfasser]. "Modelling, Control and Stability Analysis of Photovoltaic Systems in Power System Dynamic Studies / Gustav Lammert." Kassel : Kassel University Press, 2019. http://d-nb.info/1196034125/34.
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Hofmann, Martin [Verfasser]. "Analysis and improvement of irradiance modelling algorithms for the simulation of photovoltaic systems / Martin Hofmann." Hannover : Gottfried Wilhelm Leibniz Universität, 2019. http://d-nb.info/1196809119/34.
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Vika, Håvard Breisnes. "Modelling of Photovoltaic Modules with Battery Energy Storage in Simulink/Matlab : With in-situ measurement comparisons." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26128.
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The use of renewable energy sources is increasing and will play an important role in the future power systems. The unpredictable and fluctuating nature of solar power leads to a need for energy storage as the prevalence increases.A five parameter model of PV modules has been implemented in Simulink/Matlab. The parameters of the model are determined by an approximation method using data sheet values. Inputs to the model include light intensity and ambient temperature. The outputs are any measurements of interests as well as power, cell temperature and voltage. Effects of varying the model parameters are demonstrated. A maximum power point tracking algorithm is used to keep the voltage at the maximum power point at all times.A battery model based on discharge curve fitting is implemented. The model is based on a fundamental battery cell which can be modified to construct many different module configurations. Power smoothing algorithms which average the input over a set time, are used to provide a power reference to the battery system.The PV model power output is compared to in-situ measurements by giving the model inputs of measured irradiance profile and ambient temperature. Measurements of two different days, one with little variation in irradiance and one with a lot of variation, are used to shed light on different effects. The difference between the output of the simulation and the measured values is very small, in the range of a few percent, especially when there is little variation in irradiance. Large peaks in difference are probably caused by the maximum power point tracking not being able to follow rapidly changing conditions.The approximation used in the modelling of cell temperature deviates significantly from the measured cell temperature. This is confirmed as one of the largest causes of deviance by running simulations with actual measured cell temperature.Power smoothing efficiency is demonstrated with different battery module sizes. Changing the power smoothing algorithm parameters to suit the battery capacity is shown to be effective in providing as good smoothing as possible within battery constraints.
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Zacharopoulos, Aggelos. "Optical design modelling and experimental characterisation of line-axis concentrators for solar photovoltaic and thermal applications." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342344.
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Clemente, Andres. "Design and modelling of a photovoltaic driven fan solar air heater for drying woodchip in Scotland." Thesis, Edinburgh Napier University, 2011. http://researchrepository.napier.ac.uk/Output/4417.
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In the wood fuel supply chain, the water contained in the product determines one aspect of the quality of the wood. It is necessary to reduce the moisture content (MC) of the wood in order to reduce transport and storing costs and also to increase the heating value of the wood. In this thesis a solar thermal application has been developed to dry woodchips using exclusively solar energy. The novel solar woodchip dryer comprises a small woodchip dryer and a solar air thermal system (SATS) to increase the temperature of the drying air. The particularity of this woodchip dryer is that the input air flow is governed by a photovoltaic driven fan. Based on the experimental results obtained, the woodchip dryer and the SATS thermal performance were modelled and a simulation tool for predicting the dried woodchip production during a period of time has been developed. Two small capacity dryers, a thin and a thick layer dryer, have been designed and built to dry woodchip based on the flow capacity of the SATS. The drying performances are studied for both configurations comparing the drying times, drying rates and efficiencies at different test conditions. The drying curves obtained from each test are modelled as a function of key parameters, temperature and velocity employing the Page model equation. Based on the experimental results, a drying model has been successfully developed to predict the MC when the woodchip dryer operates within a range of drying conditions. A quantitative and qualitative analysis of the SATS thermal performance has been conducted employing various solar air collector configurations under Scottish weather conditions. The pneumatic characteristics of the solar dryer including the dryer are determining for the analysis of the system performance. Because of the PV driven fan electrical characteristics, the SATS presents a unique operation regime in which air flow depends exclusively on solar radiation. Thus the SATS thermal performance has been successfully modelled as a function of irradiance. The study necessarily includes the effect of environmental factors such as wind and cloudiness in the transient regime. The potential of using a solar woodchip dryer has been assessed based on the results obtained from modelling the dryer and the SATS together. The feasibility and employability of using the solar dryer for drying woodchips is discussed considering the productivity, the energy savings, costs and integration.
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Adeleke, Adedayo Kelvin. "Web-based GIS modelling of building-integrated solar photovoltaic system for the City of Cape Town." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29181.
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Population increase in African cities have made it hard to reduce their ecological footprint and attain self-sustainability. This made the United Nations to put forward the seventeen sustainable development goals. Three of these goals centre on provision of clean energy and reduction of reliance on fossil fuels. It is therefore important for cities in Africa to chart a path of attaining sustainability. Consequently, the city of Cape Town is leading the drive for a greener city and self-sustainability in energy. Solar energy, which is regarded as a clean and renewable source of energy, makes it possible to generate electricity by using photovoltaics technology. However, the problem of creating awareness as to the potentials of building-integrated solar photovoltaic system persists. The study is aimed at using remote sensing and Geographic Information Systems (GIS) techniques in creating awareness about the potentials of building rooftops for solar photovoltaics installations in an urban setting. In achieving this, Light Detection and Ranging (LiDAR) data and aerial imagery are sourced from City of Cape Town municipality to serve as the primary data input. Four phases of analysis are involved: (1) extraction of whole building roof outline and its roof planes, using the integration of LiDAR-derived products and aerial imagery, in order to determine the surface area of the roof planes. This is achieved by developing a unique two-in-one, object-based classification rulesets; (2) estimating and validating the global solar radiation incidence on each roof plane, using a LiDAR-derived elevation model in a python script utilizing the GRASS script library; (3) evaluating the solar photovoltaic potential of each roof plane, using inputs from two previous phases to create a solar photovoltaic potential database; and (4) deploying the solution online to create awareness, by utilizing JavaScript and Hypertext Mark-up Language (HTML) to implement a map mashup, which incorporates tile map and table services. This results in a web-based solution, which can be queried to retrieve information about the solar photovoltaic potential of a building roof. From the results generated and the system developed, it becomes possible to remotely and sufficiently evaluate buildings in the city for solar photovoltaic potentials, designs and installations. Thereby reducing reliance on the fossil fuel generated electricity and improving the self-sustainability of the city.
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Chong, Benjamin Vui Ping. "Modelling and controlling of integrated photovoltaic-module and converter systems for partial shading operation using artificial intelligence." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/11321/.
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The thesis has three main themes: analysis and optimal design of Cuk DC-DC converters; integration of Cuk DC-DC converters with photovoltaic (PV) modules to improve operation during partial shading; and an artificial intelligence model for the PV module, permitting an accurate maximum power point (MPP) tracking in the integrated system. The major contribution of the thesis is the control of an integrated photovoltaic module and DC-DC converter configuration for obtaining maximum power generation under non-uniform solar illumination. In place of bypass diodes, the proposed scheme embeds bidirectional Cuk DC-DC converters within the serially connected PV modules. A novel control scheme for the converters has been developed to adjust their duty ratios, enabling all the PV modules to operate at the MPPs corresponding to individual lighting conditions. A detailed analysis of a step-down Cuk converter has been carried out leading to four transfer functions of the converter in two modes, namely variable input - constant output voltage, and variable output - constant input voltage. The response to switch duty ratio variation is shown to exhibit a non-minimum phase feature. A novel scheme for selecting the circuit components is developed using the criteria of suppressing input current and output voltage ripple percentages at a steady state, and minimising the time integral of squared transient response errors. The designed converter has been tested in simulation and in practice, and has been shown to exhibit improved responses in both operating modes. A Neuro-Fuzzy network has been applied in modelling the characteristics of a PV module. Particle-Swarm-Optimisation (PSO) has been employed for the first time as the training algorithm, with which the tuning speed has been improved. The resulting model has optimum compactness and interpretability and can predict the MPPs of individual PV modules in real time. Experimental data have confirmed its improved accuracy. The tuned Neuro-Fuzzy model has been applied to a practical PV power generation system for MPP control. The results have shown an average error of 1.35% compared with the maximum extractable power of the panel used. The errors obtained, on average, are also about four times less than those using the genetic-algorithm-based model proposed in a previous research. All the techniques have been incorporated in a complete simulation system consisting of three PV panels, one boost and two bidirectional Cuk DC-DC converters. This has been compared under the same weather conditions as the conventional approach using bypass diodes. The results have shown that the new system can generate 32% more power.
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Mehranfar, Shayan. "Finite Element Modelling and On-Site Measurements for Roof Mounted Photovoltaic Solar Panels under High Wind Load." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31748.
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The application of dynamic wind load on photovoltaic (PV) solar systems mounted on
flat roofs influenced their structural behavior significantly. It is implied that when the PV solar system is exposed to extreme weather characteristics such as low temperatures, these might influence the load distribution along each layer of the solar panel, which is composed by multiple layers of different materials. Therefore, the high record of weather characteristics as one scenario in addition to the field experiment were designed to describe parametric structural behavior of PV solar system help to increase the precision of study. According to the mentioned procedures different parameters of weather characteristics measured with instrumentation at the site of PV panel installation at the University of Ottawa
where the low temperature equal to -24.3° C and wind speed of 11.8 recorded. The
mechanical and thermal properties of full-scale specimen and load application that computed based on weather record for every two minutes of January and February from northern side of specimen, introduced to FEM software SAP 2000. Moreover, the support structure and connection used to assemble real specimen considered in modeling with respect to average temperature equal to -7° C that caused to simulate 36 different cases to compare with simultaneous experiment designed to measured strain within same period. The second investigation involved instrumenting a full-scale PV solar panel specimen with 13 half-bridge strain gauges on both surfaces of the PV solar panel, which were used to measure strain values in longitudinal and transversal directions of solar panel and also on the
top and bottom edges of the same panel. According to an equivalent uniform Young’s modulus numerically determined for the five layers of the PV solar panel, and with respect to the Hook’s law, the stresses were found to be equal to 50 Mpa for strain gauges at the mid area of PV solar panel,. This value was used to calibrate boundary conditions of the FE model namely the Fix-Equal and the Pin-Equal conditions along the edges of the solar panel and along the mounting frame.
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Malm, Ulf. "Modelling and Degradation Characteristics of Thin-film CIGS Solar Cells." Doctoral thesis, Uppsala University, Solid State Electronics, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9291.
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Thin-film solar cells based around the absorber material CuIn1-xGaxSe2 (CIGS) are studied with respect to their stability characteristics, and different ways of modelling device operation are investigated. Two ways of modelling spatial inhomogeneities are detailed, one fully numerical and one hybrid model. In the numerical model, thin-film solar cells with randomized parameter variations are simulated showing how the voltage decreases with increasing material inhomogeneities.
With the hybrid model, an analytical model for the p-n junction action is used as a boundary condition to a numerical model of the steady state electrical conduction in the front contact layers. This also allows for input of inhomogeneous material parameters, but on a macroscopic scale. The simpler approach, compared to the numerical model, enables simulations of complete cells. Effects of material inhomogeneities, shunt defects and grid geometry are simulated.
The stability of CIGS solar cells with varying absorber thickness, varying buffer layer material and CIGS from two different deposition systems are subjected to damp heat treatment. During this accelerated ageing test the cells are monitored using characterization methods including J-V, QE, C-V and J(V)T. The degradation studies show that the typical VOC decrease experienced by CIGS cells subjected to damp heat is most likely an effect in the bulk of the absorber material.
When cells encapsulated with EVA are subjected to the same damp heat treatment, the effect on the voltage is considerably reduced. In this situation the EVA is saturated with moisture, representing a worst case scenario for a module in operation. Consequently, real-life modules will not suffer extensively from the VOC degradation effect, common in unprotected CIGS devices.