Η συνεχής αύξηση της ενεργειακής κατανάλωσης, η μη ορθολογική χρήση της ενέργειας, η διαρκής εξάρτηση από ορυκτές ενεργειακές πηγές, έχουν δημιουργήσει έντονα περιβαλλοντικά, οικονομικά, πολιτικά και κοινωνικά προβλήματα τις τελευταίες δεκαετίες σε παγκόσμιο, ευρωπαϊκό, εθνικό, αλλά και ατομικό επίπεδο. Το ευρύ φάσμα αυτών των προβλημάτων αποτέλεσε πολλές φορές την αφορμή προβληματισμού της διεθνούς κοινότητας σχετικά με το πρότυπο ανάπτυξης που ακολουθείται και τη χάραξη πολιτικής που θα μπορεί να εξυπηρετεί με επάρκεια και δικαιοσύνη τις σημερινές και μελλοντικές ανάγκες του ανθρώπου. Η ανάγκη για ενεργειακή αυτάρκεια και απεξάρτηση των κρατών από εισαγόμενα καύσιμα, ιδίως από χώρες με ασταθείς πολιτικές και κοινωνικές καταστάσεις, καθώς και η ανάγκη για αποκεντρωμένη ανάπτυξη και τόνωση της τοπικής απασχόλησης ενισχύει την αντίληψη για αλλαγή και κυρίως βελτίωση του σημερινού παγκόσμιου ενεργειακού σκηνικού. Η Κύπρος ακολουθώντας τις οδηγίες και τους κανονισμούς της Ευρωπαϊκής Ένωσης έχει κάνει την τελευταία δεκαετία σημαντικά βήματα στην αξιοποίηση των ΑΠΕ τα οποία όμως δεν μπορούν σε καμιά περίπτωση να θεωρηθούν επαρκή, δεδομένων των σημερινών ενεργειακών αναγκών. Πολλά δημόσια κτίρια του νησιού καταναλώνουν υπέρογκα ποσά ηλεκτρικής ενέργειας που επιβαρύνουν οικονομικά το κράτος. Ένα από αυτά είναι και το Γενικό Νοσοκομείο Λεμεσού. Το τεράστιο μέγεθος του κτιρίου αλλά και η αδιάκοπη λειτουργία των ιατρικών μηχανημάτων οδηγούν σε ένα τεράστιο φορτίο το οποίο πρέπει να ικανοποιείται καθημερινώς. Σε αυτό το πλαίσιο, αντικείμενο της παρούσας εργασίας είναι η κατάθεση μιας ολοκληρωμένης πρότασης για την εγκατάσταση ΑΠΕ στο Γενικό Νοσοκομείο Λεμεσού. Για το σκοπό αυτό μελετάμε τρείς διαφορετικές περιπτώσεις. Η πρώτη αφορά ένα Φ/Β σύστημα διασυνδεδεμένο με το δίκτυο. Η δεύτερη ένα υβριδικό σύστημα διασυνδεμένο στο δίκτυο ενώ στη τελευταία περίπτωση εξετάζεται η ενεργειακή αυτονομία του κτιρίου. Πολλές είναι εκείνες οι προσπάθειες και έρευνες που έχουν καταβληθεί στον τομέα της ενεργειακής αυτονομίας περιοχών αλλά και κτιρίων με μεγάλη ή μικρότερη επιτυχία, δίνοντας, όμως, πάντα το στίγμα των σημερινών επιταγών που επιβάλλονται από την ανάγκη της κοινωνίας για “καθαρότερες” ενεργειακές μορφές, μικρότερη εξάρτηση από εισαγόμενες πηγές ενέργειας και συστήματα ηλεκτροπαραγωγής με περισσότερη αξιοπιστία. Ο σχεδιασμός και η βελτιστοποίηση αυτών των συστημάτων, τα οποία μπορούν και συνδυάζουν περισσότερες από μία μορφές ενέργειας, είναι το στοίχημα των σημερινών επιστημονικών και τεχνολογικών ερευνών. Σήμερα, ο βέλτιστος συνδυασμός των αυτόνομων υβριδικών ενεργειακών συστημάτων μπορεί να επιτευχθεί μέσω πιθανοτικών, επαναληπτικών, γραφικών ή πολυκριτηριακών τεχνικών, ενώ μέσω της αξιοποίησης των οικονομικών δεικτών (Καθαρή Παρούσα Αξία, Εσωτερικός Βαθμός Απόδοσης, Ανάλυση Κύκλου Ζωής κλπ) επιτυγχάνεται η οικονομοτεχνική αξιολόγηση των συστημάτων αυτών. Τα τελευταία χρόνια, δεν είναι λίγα τα λογισμικά που έχουν αναπτυχθεί προκειμένου να βοηθούν στο σχεδιασμό, στην τεχνική και οικονομική αξιολόγηση, ή και ακόμα στην αριστοποίησή των ενεργειακών επενδύσεων. Λογισμικά, όπως το EnergyPLAN, το energyPRO, το H2RES, το TRNSYS16, το RETScreen, το PV*SOL και το HOMER, χρησιμοποιούνται ως εργαλεία σχεδιασμού, τεχνικοοικονομικής και περιβαλλοντικής αξιολόγησης ενεργειακών συστημάτων, τα οποία συνδυάζουν μία ή και περισσότερες μορφές ενέργειας και βρίσκονται συνδεδεμένα ή μη στο κεντρικό δίκτυο. Στην περίπτωση της πρότασης της εν λόγω εργασίας χρησιμοποιήθηκαν τα λογισμικά HOMER και PV*SOL. Με το πρώτο εργαλείο ο χρήστης έχει τη δυνατότητα να συνδυάσει πηγές ενέργειας, όπως οι Α/Γ, τα Φ/Β, τα υδροηλεκτρικά, οι κυψέλες υδρογόνου, οι ντιζελογεννήτριες, με μέγεθος που αυτός επιθυμεί, και έπειτα από πλήθος προσομοιώσεων να επιλέξει το σύστημα με τα καλύτερα για αυτόν τεχνικά, οικονομικά και περιβαλλοντικά χαρακτηριστικά. Από την άλλη, το PV*SOL αποτελεί ένα εργαλείο με το οποίο ο χρήστης μπορεί να σχεδιάσει πλήρως ένα Φ/Β σύστημα συμπεριλαμβανομένου και του κτιρίου ή της περιοχής εγκατάστασης λαμβάνοντας υπόψη κύριους παράγοντες, όπως η σκίαση, που επηρεάζουν την απόδοση του συστήματος. Βέβαια, η ανάλυση ευαισθησίας σε παραμέτρους των συστημάτων, όπως τα αρχικά κόστη, το ύψος δανεισμού, το επιτόκιο δανεισμού, η περίοδος χρέους και άλλα, μπορούν να διαμορφώσουν πλήθος συσχετισμών που να επιτρέπουν την οικονομική βιωσιμότητα συστημάτων ηλεκτρικής παραγωγής, τα οποία με μια πρώτη ανάγνωση μοιάζουν μη εφικτά και οικονομικά μη συμφέροντα. Χαρακτηριστικό παράδειγμα της συγκεκριμένης διαπίστωσης, που απορρέει από την ανάλυση ευαισθησίας, είναι πως το ύψος των οικονομικών κινήτρων, όπως οι επιδοτήσεις και τα χαμηλότοκα δάνεια, μπορούν να δώσουν ώθηση στην ανάπτυξη συστημάτων παραγωγής ηλεκτρισμού από ΑΠΕ, ακόμα και με αποκλειστική χρήση αυτών. Όλα τα παραπάνω αναλύονται διεξοδικά σε όλη την έκταση της παρούσας εργασίας, αναλύοντας το πρόβλημα τεχνοοικονομικής μελέτης για εγκατάσταση ΑΠΕ στο Γενικό Νοσοκομείο Λεμεσού. Συγκεκριμένα, το Κεφάλαιο 1 αποτελεί μια αναφορά στο σημερινό ενεργειακό πρόβλημα, πως αυτό έχει προσεγγισθεί σε παγκόσμιο, ευρωπαϊκό και εθνικό επίπεδο και τις προσπάθειες που γίνονται προκειμένου να αντιμετωπισθεί με αποτελεσματικότητα. Αναφορά γίνεται ταυτόχρονα και στην ενεργειακή κατάσταση στην οποία βρίσκεται η Κύπρος. Το Κεφάλαιο 2 περιγράφει πως οι πολιτικές που ακολουθούνται σήμερα συνάδουν με τις Οδηγίες και τους Κανονισμούς της Ευρωπαϊκής Ένωσης για ανατροπή του σύγχρονου ενεργειακού σκηνικού. Ο κύριος σχολιασμός πραγματοποιείται επί των πολιτικών που σχετίζονται με την προώθηση των Ανανεώσιμων Πηγών Ενέργειας και πως αυτές μπορούν σήμερα να εγγυηθούν την ενεργειακή αυτονομία, την ασφάλεια στον ενεργειακό εφοδιασμό και την προστασία του περιβάλλοντος. Στο Κεφάλαιο 3 αναφέρονται οι βασικές τεχνολογίες και τα χαρακτηριστικά των ΑΠΕ που συμμετέχουν στη δημιουργία των υβριδικών συστημάτων παραγωγής ενέργειας που προτείνονται για το Νοσοκομείο Λεμεσού. Συγκεκριμένα, περιγράφονται τα δομικά χαρακτηριστικά των Φ/Β συστημάτων, των ανεμογεννητριών, των αντιστροφέων αλλά και ντιζελογεννητριών, ενώ πραγματοποιείται μια πρώτη προσέγγιση στην παγκόσμια και κυπριακή ενεργειακή αγορά. Το Κεφάλαιο 4 αποτελεί το σημείο στο οποίο περιγράφεται αναλυτικά η περιοχή μελέτης, οι κλιματολογικές της συνθήκες, ενώ παράλληλα, γίνεται και μια εισαγωγή στα συστήματα που είναι διασυνδεδεμένα με το δίκτυο και τις συνθήκες που πρέπει να πληρούν. Στη συνέχεια γίνεται αναφορά της νεοεισαχθείς για τα κυπριακά δρόμενα μεθόδου, της τεχνολογίας Συμψηφισμού Μετρήσεων (Net-Metering). Τέλος γίνεται αναφορά για τα αυτόνομα υβριδικά συστήματα και τις χρήσεις τους. Στο Κεφάλαιο 5 πραγματοποιείται η τεχνοοικονομική μελέτη εγκατάστασης Φ/Β συστήματος στην οροφή του Νοσοκομείου. Συγκεκριμένα σε πρώτη φάση παρουσιάζονται λεπτομερώς τα βήματα για μια ολοκληρωμένη μελέτη. Στη συνέχεια προβάλλονται τα αποτελέσματα της εξομοίωσης που αφορούν τα κύρια χαρακτηριστικά του συστήματος, όπως η ονομαστική ισχύς, το Καθαρό Παρόν Κόστος, η απόδοση κλπ. Επεκτείνοντας την αρχική μελέτη, στο Κεφάλαιο 6 γίνεται η εξομοίωση ενός υβριδικού συστήματος διασυνδεδεμένου στο δίκτυο, στο οποίο εκτός από Φ/Β πλαίσια έχουμε συμπεριλάβει και Α/Γ. Σε δεύτερη φάση μελετάμε ένα σύστημα αυτοπαραγωγής. Για τις δύο αυτές μελέτες χρησιμοποιήθηκε το λογισμικό HOMER. Τέλος στο Κεφάλαιο 7, συμπυκνώνονται όλα τα συμπεράσματα και οι παρατηρήσεις των τεχνοοικονομικών και περιβαλλοντικών αξιολογήσεων των συστημάτων παραγωγής ηλεκτρισμού, ενώ παράλληλα γίνεται μια σύγκριση σχετικά με τη πιο συμφέρουσα πρόταση με κριτήριο τη μικρότερη αρχική επένδυση με το μεγαλύτερο δυνατό κέρδος. Έχοντας πάντα ως πρωταρχικό στόχο τα κριτήρια αυτά καταλήγουμε στο συμπέρασμα ότι η ιδανικότερη λύση είναι η περίπτωση του διασυνδεδεμένου υβριδικού συστήματος, η οποία αποφέρει το μεγαλύτερο κέρδος, μειώνοντας παράλληλα τις εκπομπές ρύπων, αφού χρησιμοποιεί αποκλειστικά ανανεώσιμες πηγές. Στη συνέχεια παρατίθενται κάποιες προτάσεις για περαιτέρω έρευνα και σε άλλα κτίρια, οι οποίες μπορούν να βοηθήσουν στην ανατροπή του σημερινού ενεργειακού προβλήματος του νησιού. / The continuous increase in energy consumption, the irrational use of energy, the continuous dependence on fossil energy sources, have generated intense environmental, economic, political and social problems in recent decades at global, European, national, and individual level. The wide range of these problems has often given rise reflection of the international community about the development model followed and policy that can serve with competence and fairness of current and future human needs. The need for energy self-sufficiency and independence of states from imported fuels, particularly from countries with unstable political and social situations, the need for decentralized development and boost local employment reinforces the perception of change and especially improving the current global energy scene. Cyprus, following the guidelines and European Union regulations, has made important steps in the development of renewable sources the last decade, but which may in no case be considered sufficient, given the current energy needs. Many public buildings on the island consume huge amounts of electricity that cost the state. One of them is the Limassol General Hospital. The sheer size of the building and the uninterrupted operation of medical equipment lead to a huge load which must be met daily. In this context, the subject of this thesis is the submission of a complete proposal for installing RES in Limassol General Hospital. For this purpose we study three different cases. The first concerns a PV system connected to the grid. The second a hybrid system interconnected to the grid while in the last case the energy autonomy of the building is considered. Many are those efforts and research have been made in the field of energy autonomy areas and buildings, some with large success and some with less, giving, however, always the mark of current requirements imposed by society's need for "cleaner" forms of energy, less dependence on imported energy sources and power systems with more reliability. The design and optimization of these systems, which can combine more than one form of energy, is the bet of the current scientific and technological research. Today, the optimal combination of autonomous hybrid energy systems can be achieved through probabilistic, repetitive, graphics or multicriteria techniques, and through the use of financial indicators (NPV, IRR, LCA etc.) achieve the financial and evaluation systems thereof. In recent years, there are few software have been developed to assist in the design, technical and economic evaluation, or even in the optimization of energy investments. Software like EnergyPLAN, the energyPRO, the H2RES, the TRNSYS16, the RETScreen, the PV*SOL and HOMER, used as planning tools, logistical and environmental evaluation of energy systems, which combine one or more forms of energy and are connected or not in the grid. In the case of the proposal of this thesis the software HOMER and PV*SOL were used. In the first software, the user is able to combine energy sources, such as WT, the PV, hydroelectric, hydrogen cells, the diesel generators, size he desires, and then a plurality of simulations to select the system the best for this technical, economic and environmental characteristics. On the other hand, PV*SOL is a tool with which the user can fully design a PV system, including the building or installation area taking into account key factors, such as shading, affecting system performance. Of course, the sensitivity analysis on parameters of systems, including initial costs, the loan amount, the interest rate, the debt term and others, can form correlations that allow the economic viability of the electrical power system, which at first they look not practicably and economically profitable. A typical example of this verification, resulting from the sensitivity analysis, is that the level of financial incentives, such as grants and soft loans, may give impetus to the development of electricity production from RES systems, even with exclusive use. All the above discussed thoroughly throughout this work, analyzing a techno-economic study for installing RES in Limassol General Hospital. Specifically, Chapter 1 is a reference to the current energy problem that has approximated at global, European and national levels and what efforts are made to address effectively. Reference is made simultaneously in the energy situation of the Cyprus. Chapter 2 describes how the policies pursued today are in line with the Directives and EU Regulations for the overthrow of modern energy scene. The main commentary is based on the policies related to the promotion of renewable energy and how they can now guarantee energy independence, the security of energy supply and environmental protection. Chapter 3 sets out the key technologies and characteristics of RES involved in the installation of hybrid power systems proposed for Limassol Hospital. Specifically, the structural characteristics of PV panels, WT, inverters and diesel generators are described, while making a first approach to the global and Cypriot energy market. In Chapter 4 details of the study area and the climatic conditions are pointed out, while an introduction to the systems which are interconnected through the network and the conditions that must prerequisite, is made. Followed by a reference of the newly introduced, for Cyprus standards, method of Net-Metering. Finally reference to the autonomous hybrid systems and their uses, is made. In Chapter 5 the techno-economic study of PV system installation on the roof of the hospital is carried out. Initially the steps for a comprehensive study are detailed. Then the results of the simulation on the main features of the system, such as rated power, the Net Present Cost, performance etc are viewed. Extending the initial study, in Chapter 6, in addition to PV panels we included WT, leading to a hybrid system connected to the grid. In the second phase a self-fed system is proposed. For these studies we used the HOMER software. Finally, in Chapter 7, all the conclusions and observations of the techno-economic and environmental assessments of power generation systems are concentrated, while the most advantageous proposal in terms of lower initial investment with the greatest possible profit is searched. Having as primary objective that criteria we conclude that the ideal solution is the case of interconnected hybrid system, which offers the most profit while reducing emissions, since it uses only renewable sources. Some proposals for further research and other buildings, which can help to reverse the current energy problem on the island, are suggested.

The use of full wave electromagnetic modeling and simulation tools allows for accurate performance predictions of unique RF structures that exhibit multi-dimensional scales. Full wave simulation tools need to cover the broad range of frequency including RF and terahertz bands that is focused as RF technology is developed. In this dissertation, three structures with multi-dimensional scales and different operating frequency ranges are modeled and simulated. The first structure involves nanostructured solar cells. The silicon solar cell design is interesting research to cover terahertz frequency range in terms of the economic and environmental aspects. Two unique solar cell surfaces, nanowire and branched nanowire are modeled and simulated. The surface of nanowire is modeled with two full wave simulators and the results are well-matched to the reference results. This dissertation compares and contrasts the simulators and their suitability for extensive simulation studies. Nanostructured Si cells have large and small dimensional scales and the material characteristics of Si change rapidly over the solar spectrum. The second structure is a reconfigurable four element antenna array antenna operating at 60 GHz for wireless communications between computing cores in high performance computing systems. The array is reconfigurable, provides improved transmission gain between cores, and can be used to create a more failure resilient computing system. The on-chip antenna array involves modeling the design of a specially designed ground plane that acts as an artificial magnetic conductor. The work involves modeling antennas in a complex computing environment. The third structure is a unique collar integrated zig-zag antenna that operates at 154.5 MHz for use as a ground link in a GPS based location system for wildlife tracking. In this problem, an intricate antenna is modeled in the proximity of an animal. Besides placing a low frequency antenna in a constricted area (the collar), the antenna performance near the large animal body must also be considered. Each of these applications requires special modeling details to take into account the various dimensional scales of the structures and interaction with complex media. An analysis of the challenges and limits of each specific problem will be presented.

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

<p>An explosion in the growth of organic materials used for optoelectronic devices is linked to the promise that they have demonstrated in several ways: workable carrier mobilities, ease of processing, design flexibility to tailor their optical and electrical characteristics, structural flexibility, and fabrication scalability. However, challenges remain before they are ready for prime time. Deposition of these materials into ordered thin films requires that they be cast from solutions of organic solvents. Drawbacks of solution-casting include the difficulty of producing layered films without utilizing orthogonal solvents (or even with orthogonal solvents), the difficulty in controlling domain sizes in films of mixed materials, and the lack of parameter options used to control the final properties of thin films. Emulsion-based, resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a thin film deposition technique that is demonstrated to provide solutions to these problems.</p><p>This work presents fundamental research into the RIR-MAPLE process. An investigation of the molecular weight of deposited materials demonstrates that emulsion-based RIR-MAPLE is capable of depositing polymers with their native molecular weights intact, unlike other laser deposition techniques. The ability to deposit multilayer films with clearly defined interfaces is also demonstrated by cross-sectional transmission electron microscopy imaging of a layered polymer/quantum dot nanocomposite film. In addition, trade-offs related to the presence of surfactant in the target, required to stabilize the emulsion, are articulated and investigated by x-ray diffraction, electrical, optical, and surface characterization techniques. These studies show that, generally speaking, the structural, optical and electrical properties are not significantly affected by the affected by the presence of surfactant, provided that the concentration within the target is sufficiently low. Importantly, the in-plane mobility of RIR-MAPLE devices, determined by organic field effect transistor (OFET) characterization, rivals that of spin-cast devices produced under similar conditions. </p><p>This work also presents results of emulsion-based RIR-MAPLE deposition applied to optical coatings (gradient-refractive index antireflection coating based on porous, multilayer films) and optoelectronic devices (organic photovoltaics based on the polymer, P3HT, and small molecule, PC61BM, bulk heterojunction system). The optical coating demonstrates that RIR-MAPLE is capable of producing nanoscale domain sizes in mixed polymer blends that allow a film to function as an effective medium relevant to devices in the visible spectrum. Moreover, bulk heterojunction organic photovoltaic (OPV) devices that require nanoscale domains to function effectively are achieved by co-deposition of P3HT and PC61BM, achieving a power conversion efficiency of 1.0%, which is a record for MAPLE-deposited devices. </p><p>Results of these studies illuminate unique capabilities of the RIR-MAPLE process. Multilayer films are readily fabricated to create true bilayer OPV structures. Additionally, true gradient thin films are created by varying the ratio of two materials, including two-polymer films and a film consisting of a polymer and a small molecule, over the course of a single deposition.</p> / Dissertation

Inorganic materials have dominated electronic applications such as photovoltaic cells, thin film transistors (TFTs) and light emitting diodes (LEDs). However developments in the field of organic electronics over the past three decades have enabled the use of organic materials in these devices. While significant improvements have been made to improve their electronic properties there are several road blocks towards commercial application. One of the significant obstacles is the poor charge carrier mobility associated with organic semiconductors processed by well established printing methods. The goal of my research project is to improve the charge carrier mobility of solution cast films of acene semiconductors by partial halogenation and heteroatom substitution. Spin coated films of triisopropylsilylethynylated difluoropentacene exhibited higher hole mobility compared to TIPS pentacene due to contact induced nucleation of pentacene on perfluorobenzenethiol treated gold electrodes. The success of this project allowed me to further investigate the effect of degree of fluorination on the electronic properties of pentacene. A series of trialkylsilylethynylated tetrafluoro and octafluoropentacenes were synthesized and their performances in thin film transistors and solar cells were explored. Solar cells made from these materials using poly(3-hexylthiophene) as donor exhibited poor open circuit voltages (Voc) resulting in low power conversion efficiency (PCE). Better device performances were achieved using pentacenes having single halogen substituent. In order to improve the charge carrier mobility in TFTs soluble trialkylsilylethynylated hexacenes were explored. However these molecules exhibited a greater tendency to photo-dimerize in solution and solid state. Partial halogenation was used as a tool to improve the solution stability of reactive hexacene. The improved solution stability of partially halogenated hexacenes allowed me to successfully extend this approach to heptacene and nonacene. Finally a series of new trialkylsilylethynylated anthradiselenophenes were synthesized to improve molecular ordering in the solid state by increasing non-bonding Se – Se interaction. However single crystal x-ray diffraction studies revealed no such interaction between the acene chromophore resulting in poor device performance.

Among technologies capable to produce electricity locally without contributing to GHG releases, building integrated PV systems (BIPV) could be major contributor. However, when exposed to intense solar radiation, the temperature of PV modules increase significantly, leading to a reduction in efficiency so that only about 14% of the incident radiation is converted into electrical energy. The high temperature also decrease the life of the modules, thereby making passive cooling of the PV components through natural convection a desirable and cost-effective means of overcoming both difficulties. An experimental investigation of heat transfer and fluid flow characteristics of natural convection of air in vertical and inclined open-ended heated channels is therefore undertaken so as provide reliable information for the design of BIPV. Two experimental set ups were developed and used during the present investigations; one located at the CETHIL laboratory in Lyon, the F-device and the other located at the University of New South Wales in Sydney, the R-device. Both channels consisted of two wide parallel plates each of which could be subjected to controlled uniform or non-uniform heat fluxes. The investigation has been conducted by analyzing the mean wall temperatures, measured by thermocouples and mean velocity profiles and turbulent quantity distributions of the flow, measured with a PIV system. Flow patterns close to the heated faces were also investigated. The study is particularly focused on the transition region from laminar to turbulent flow. Three different heating geometric arrangements are examined in the modified Rayleigh number range from 3.86 x 105 to 6.22 x 106. The first is a vertical channel with one wall uniformly heated while the other was unheated, the second was a vertical channel in which both walls were non-uniformly heated and the third is an inclined channel uniformly heated from above. In the vertical configurations the width-to-height channel aspect ratio was fixed at 1:15 and in the inclined ones at 1:16. It is shown that the flow is very sensitivity to disturbances emanating from the ambient conditions. Moreover, the propagation of vortical structures and unsteadiness in the flow channel which are necessary to enhance heat transfer, occurred downstream of the mid-channel section at Ra* = 3.5 x 106 for uniformly and asymmetrically heated channels inclined between 60° and 90° to the horizontal. Indeed, these unsteady flow phenomena appears upstream the location of the inflexion point observed in the temperature excess distribution of the heated wall. In the case of non-uniform heating on both sides of the channel, a stronger 'disruption mechanism' exists, which leads to enhanced mixing and increased Reynolds stresses over most of the width of the channel. Empirical correlations of average Nusselt number as a function of modified Rayleigh number were obtained for each configuration.

This doctorate thesis focuses on investigating the parameter space involved in numerically modeling the bandgap engineering of a GaInP/InGaAs/Ge lattice matched multi-junction solar cell (MJSC) using InAs/InGaAs quantum dots (QDs) in the middle sub-cell. The simulation environment – TCAD Sentaurus – solves the semiconductor equations using finite element and finite difference methods throughout well-defined meshes in the device to simulate the optoelectronic behavior first for single junction solar cells and subsequently for MJSCs with and without quantum dots under concentrated illumination of up to 1000 suns’ equivalent intensity. The MJSC device models include appropriate quantum tunneling effects arising in the tunnel junctions which serve as transparent sub-cell interconnects. These tunneling models are calibrated to measurements of AlGaAs/GaAs and AlGaAs/AlGaAs tunnel junctions reaching tunneling peak current densities above 1000 A/cm^2. Self-assembled InAs/GaAs quantum dots (QDs) are treated as an effective medium through a description of appropriate generation and recombination processes. The former includes analytical expressions for the absorption coefficient that amalgamates the contributions from the quantum dot, the InAs wetting layer (WL) and the bulk states. The latter includes radiative and non-radiative lifetimes with carrier capture and escape considerations from the confinement potentials of the QDs. The simulated external quantum efficiency was calibrated to a commercial device from Cyrium Technologies Inc., and required 130 layers of the QD effective medium to match the contribution from the QD ground state. The current – voltage simulations under standard testing conditions (1 kW/cm^2, T=298 K) demonstrated an efficiency of 29.1%, an absolute drop of 1.5% over a control structure. Although a 5% relative increase in photocurrent was observed, a 5% relative drop in open circuit voltage and an absolute drop of 3.4% in fill factor resulted from integrating lower bandgap nanostructures with shorter minority carrier lifetimes. However, these results are considered a worst case scenario since maximum capture and minimum escape rates are assumed for the effective medium model. Decreasing the band offsets demonstrated an absolute boost in efficiency of 0.5% over a control structure, thus outlining the potential benefits of using nanostructures in bandgap engineering MJSCs.

Technological improvements along with falling prices on photovoltaic (PV) panels and electric vehicles (EVs) suggest that they might become more common in the future. The introduction of distributed PV power production and EV charging has a considerable impact on the power system, in particular at the end-user in the electricity grid. In this PhD thesis PV power production, household electricity use and EV charging are investigated on different system levels. The methodologies used in this thesis are interdisciplinary but the main contributions are mathematical modeling, simulations and data analysis of these three components and their interactions. Models for estimating PV power production, household electricity use, EV charging and their combination are developed using data and stochastic modeling with Markov chains and probability distributions. Additionally, data on PV power production and EV charging from eight solar charging stations is analyzed. Results show that the clear-sky index for PV power production applications can be modeled via a bimodal Normal probability distribution, that household electricity use can be modeled via either Weibull or Log-normal probability distributions and that EV charging can be modeled by Bernoulli probability distributions. Complete models of PV power production, household electricity use and EV home-charging are developed with both Markov chain and probability distribution modeling. It is also shown that EV home-charging can be modeled as an extension to the Widén Markov chain model for generating synthetic household electricity use patterns. Analysis of measurements from solar charging stations show a wide variety of EV charging patterns. Additionally an alternative approach to modeling the clear-sky index is introduced and shown to give a generalized Ångström equation relating solar irradiation to the duration of bright sunshine. Analysis of the total power consumption/production patterns of PV power production, household electricity use and EV home-charging at the end-user in the grid highlights the dependency between the components, which quantifies the mismatch issue of distributed intermittent power production and consumption. At an aggregate level of households the level of mismatch is shown to be lower.

A long-term goal within the field of organic electronics has been to developflexible and functional devices, which can be processed and patterned withlow-cost and energy-efficient solution-based methods. This thesis presents anumber of functional paths towards the attainment of this goal via thedevelopment and demonstration of novel fabrication and patterningmethods involving the important organic-semiconductor family termedfullerenes.Fullerenes are soccer-shaped small molecules, with two often-employedexamples being the symmetric C60 molecule and its more soluble derivative[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We show that PCBM canbe photochemically transformed into a dimeric state in a bi-excited reactionprocess, and that the exposed material features a significantly reducedsolubility in common solvents as well as an effectively retained electronmobility. This attractive combination of material properties allows for adirect and resist-free lithographic patterning of electronic PCBM films downto a smallest feature size of 1 µm, using a simple and scalable two-stepprocess constituting light exposure and solution development. In a furtherdevelopment, it was shown that the two-step method was useful also in thearea-selective transformation of fullerene/conjugated-polymer blend films,as demonstrated through the realization of a functional complementary logiccircuit comprising a 5-stage ring oscillator.In another project, we have synthesized highly flexible, single-crystal C60nanorods with a solution-based self-assembly process termed liquid-liquidinterfacial precipitation. The 1-dimensional nanorods can be deposited fromtheir synthesis solution and employed as the active material in field-effecttransistor devices. Here, it was revealed that the as-fabricated nanorods canfeature an impressive electron mobility of 1.0 cm2 V-1 s-1, which is on par withthe performance of a work horse in the transistor field, viz. vacuumdeposited amorphous Si. We further demonstrated that the processability ofthe nanorods can be improved by a tuned light-exposure treatment, duringwhich the nanorod shell is polymerized while the high-mobility interior bulkis left intact. This has the desired consequence that stabile nanoroddispersions can be prepared in a wide range of solvents, and we anticipatethat functional electronic devices based on solution-processable nanorodscan be realized in a near future.

The objective of the proposed research is to establish the technology for material growth by molecular beam epitaxy (MBE) and fabrication of indium gallium nitride/gallium nitride (InxGa1-xN/GaN) heterojunction solar cells. InxGa1-xN solar cell have the potential to span 90% of the solar spectrum, however there has been no success with high indium (In) incorporation and only limited success with low In incorporation InxGa1-xN. Therefore, this present work focuses on 15 - 30% In incorporation leading to a bandgap value of 2.3 - 2.8 eV. This work will exploit the revision of the indium nitride (InN) bandgap value of 0.68 eV, which expands the range of the optical emission of nitride-based devices from ultraviolet to near infrared regions, by developing transparent InxGa1-xN solar cells outside the visible spectrum. Photovoltaic devices with a bandgap greater than 2.0 eV are attractive because over half the available power in the solar spectrum is above the photon energy of 2.0 eV. The ability of InxGa1-xN materials to optimally span the solar spectrum offers a tantalizing solution for high-efficiency photovoltaics. Using the metal modulated epitaxy (MME) technique in a new, ultra-clean refurbished MBE system, an innovative growth regime is established where In and Ga phase separation is diminished by increasing the growth rate for InxGa1-xN. The MME technique modulates the metal shutters with a fixed duty cycle while maintaining a constant nitrogen flux and proves effective for improving crystal quality and p-type doping. We demonstrate the ability to repeatedly grow high hole concentration Mg-doped GaN films using the MME technique. The highest hole concentration obtained is equal to 4.26 e19 cm-3, resistivity of 0.5 Ω-cm, and mobility of 0.28 cm2/V-s. We have achieved hole concentrations significantly higher than recorded in the literature, proving that our growth parameters and the MME technique is feasible, repeatable, and beneficial. The high hole concentration p-GaN is used as the emitter in our InxGa1-xN solar cell devices.