With higher frequencies now being used in RFID systems, antennas are becoming much smaller resulting in more space on tags that can be used for innovative array designs to harvest more wireless energy. This master's thesis outlines and details a new methodology for designing and simulating the staggered pattern charge collector, a technique to improve harvesting wireless energy. Staggered pattern charge collectors enable RFID tag's to produce a higher DC voltage from a charge pump circuit by creatively using multiple arrays to increase the antenna power conversion gain without limiting the half power beamwidth. This thesis discusses the basics of patch antennas and charge pumps as well as an optimization technique for the staggered pattern array by maximizing integrated power conversion gain (IPCG). An example of a staggered pattern charge collector is fully specified from design through simulation, in preparation for fabrication. This methodology allows for the staggered pattern charge collectors to be designed, simulated, and fabricated quickly and effectively.

Η ηλιακή ενέργεια αποτελεί μια από τις κύριες Ανανεώσιμες Πηγές Ενέργειας (ΑΠΕ). Μπορεί να αξιοποιηθεί είτε μετατρεπόμενη σε ηλεκτρισμό είτε σε θερμότητα. Για τη μετατροπή της σε ηλεκτρισμό η κύρια τεχνολογία που χρησιμοποιείται είναι η τεχνολογία των φωτοβολταϊκών. Αντίστοιχα, για την μετατροπή της σε θερμότητα χρησιμοποιούνται ευρέως οι τεχνολογίες των επίπεδων θερμικών ηλιακών συλλεκτών και των θερμικών συλλεκτών σωλήνων κενού. Βασικό ζητούμενο και στις δύο περιπτώσεις αποτελεί η μεγιστοποίηση της αποδοτικότητας τους. Μια από τις μεθόδους που μπορεί να χρησιμοποιηθεί για την αύξηση της αποδοτικότητας μιας ηλιακής συσκευής είναι η χρήση ενισχυτικών ανακλαστήρων. Επίσης, στις συνήθεις τεχνολογίες φωτοβολταϊκών που εφαρμόζονται σήμερα, η μείωση της θερμοκρασίας λειτουργίας τους βελτιώνει την απόδοση τους. Η διπλωματική ερευνητική εργασία που ακολουθεί περιλαμβάνει τη συγκριτική μελέτη φωτοβολταϊκών διατάξεων, επίπεδων θερμικών συλλεκτών και συλλεκτών σωλήνων κενού. Μελετήθηκαν συστήματα φωτοβολταϊκών με τη χρήση διαφόρων μεθόδων ψύξης, ενεργητικών και παθητικών. Επίσης μελετήθηκε η αύξηση της αποδιδόμενης ηλεκτρικής ενέργειας των φωτοβολταϊκών με χρήση ενισχυτικών ανακλαστήρων (ημικατοπτρικός ανακλαστήρας, ανακλαστήρας αλουμινίου (ματ), λευκός ανακλαστήρας). Υλοποιήθηκαν συνδυαστικά συστήματα με ταυτόχρονη ψύξη και χρήση ενισχυτικού ανακλαστήρα και μελετήθηκε η συμπεριφορά τους. Ακόμα, μελετήθηκε η αύξηση της αποδιδόμενης θερμικής ενέργειας επίπεδου ηλιακού θερμικού συλλέκτη με προσθήκη ενισχυτικών ανακλαστήρων (καθρέπτης, ανακλαστήρας αλουμινίου και λευκός ανακλαστήρας). Τέλος, κατασκευάστηκε διάταξη θερμικού συλλέκτη σωλήνα κενού με επίπεδη ανακλαστική επιφάνεια. Πραγματοποιήθηκαν πειράματα με την προσθήκη ενισχυτικών ανακλαστήρων (ημικατοπτρικός ανακλαστήρας, ανακλαστήρας αλουμινίου και λευκός ανακλαστήρας) και μελετήθηκε η αύξηση της θερμικής απόδοσης του συλλέκτη. Με βάση τα αποτελέσματα των πειραμάτων, εξάγονται αντίστοιχα συμπεράσματα και παρατίθενται προτάσεις σχετικά με τις διατάξεις αυτές. / Solar energy is one of the main Renewable Energy Sources (RES). It can be utilized by being transformed into electricity or heat. The main technology used to transform solar energy into electricity is photovoltaics. Respectively, flat plate solar thermal collectors and evacuated tube solar thermal collectors are the technologies mostly used to transform solar energy into usable heat. One of the main concerns on both cases, is the maximization of their performance. The use of booster reflectors is one of the methods that can be implemented in order to increase the performance of a solar device. Also, a method to increase the performance of the main photovoltaic technologies used at the moment, is to cool them. The following diploma – research thesis includes the comparative study of photovoltaic systems, flat plate solar thermal collectors and evacuated tube solar thermal collectors. Photovoltaic systems with the use of various cooling methods, active and passive, were studied. The increase of the photovoltaic electrical output using booster reflectors (semi specular, aluminum reflector and white reflector) was also studied. Combined systems were implemented, with simultaneous cooling and usage of booster reflector, and their behavior was observed. In addition, the increase of the thermal output of a flat plate collector by using booster reflectors (mirror, aluminum reflector and white reflector) was studied. Finally, an evacuated tube solar thermal collector system with an embedded reflective surface was implemented. Experiments were carried out with the addition of booster reflectors (semi specular, aluminum reflector and white reflector) and the increase of the collector’s thermal output was measured. Based on the experimental results, conclusions and suggestions are made about these systems.

Baigiamajame magistro darbe nagrinėjamos decentralizuoto (paskirstytojo) generavimo ir atsinaujinančių energijos išteklių panaudojimo sprendimai, aprūpinant pastatą įvairia energija – šiluma, vėsa, karštu vandeniu, elektra. Energija aprūpinama panaudojant tokius įrenginius – kogeneratorių, kompresorinę ir absorbcinę šaldymo mašinas, saulės kolektorius, dujinį katilą. Apibūdinami pasirinkti įrenginiai, jų veikimo principai, savybės, atskleidžiami jų privalumai ir trūkumai. Parengiamos trys alternatyvių variantų principinės energijos sistemų schemos, suformuotos iš minėtų įrenginių derinių. Pristatomi šių alternatyvių įvairios eneregijos gaminimo variantų galios ir energijos kiekių rodikliai. Parenkamas optimalus naujų technologijų derinys. Alternatyvių variantų ekonominis pagrįstumas įvertinamas, parenkant optimalų energijos generatorių derinį atsižvelgiant į jų bendrą atsiperkamumą. Apibendrinus teorines žinias ir gautus skaičiavimo rezultatus, pateikiamos baigiamojo darbo išvados ir pasiūlymai. Darbą sudaro 6 dalys: įvadas, teorin�� dalis, analizinė dalis, ekonominė dalis, išvados ir pasiūlymai, literatūros sąrašas. Darbo apimtis – 61 psl. teksto be priedų, 34 iliustr., 11 lent., 46 literatūros šaltiniai. Atskirai pridedami darbo priedai. / Solutions of decentralized (distributed) production and application of renewable energy sources in the case of different energy - like heating, cooling, hot water, electricity - supply for a building were analyzed in the final master thesis work. Energy supply sources are cogenerator, compressor and absorption cooling machines, solar collectors, gas boiler. Selected devices, their principles of work, characteristics, their advantages and disadvantages were described. Three schemes of principal energy system alternative were described, using combinations of devices mentioned above. Power and energy amount indexes of different energy generating alternatives were specified. The optimal combinations of new technologies were selected. After the optimal combination of energy generating system was done, economical validity of alternatives were estimated taking into account their total payback time. After theory and received results were summarized, the conclusions and suggestions were presented in the end of the final master work. Work consists of 6 parts: introduction, theory, analysis part, economical part, conclusions and suggestions, literature source. Size of Work: 61 pages of text excluding the appendixes, 34 pictures, 11 tables, 46 literature sources. Appendixes of the work are attached separately.

Au 20e siècle en France et en Allemagne, l’art moderne prend son essor. Certains, comme Francastel, qualifient cet art de destruction d’un espace plastique classique. Cette destruction devient un vecteur de création chez plusieurs artistes qui, suite aux deux grandes guerres, remettent en question leur état « civilisé » et se tournent vers le « primitif » pour offrir une autre voie, loin de tout processus civilisateur. Cette admiration pour les peuples primitifs ainsi que pour les productions artistiques d’enfants, d’amateurs et de « fous » est visible chez plusieurs collectionneurs d’art. En constituant des collections d’art marginal, ces derniers défendaient une idéologie qui propose une autre forme de culture en remplacement d’une civilisation dépassée. Grâce à leurs collections, la libre expression se positionna contre le rationalisme occidental. On compte, parmi ces collectionneurs, le psychiatre Hans Prinzhorn, le marchand d’art Wilhelm Udhe et les artistes André Breton, Jean Dubuffet et Arnulf Rainer. Chacun d’eux a eu un impact sur la construction du récit de l’art moderne et de l’art contemporain. Leurs collections ont chacune sa spécificité et offrent des vocabulaires différents pour parler de productions artistiques marginales, c’est-à-dire se développant « hors culture ». C’est par l’analyse des terminologies employées par les collectionneurs, principalement la dénomination d’art pathologique, que nous tracerons un portrait de la construction historique de l’art marginal en lien avec l’art moderne / Modern art began its rise at the beginning of the twentieth century in both France and Germany. Somme art theorists like Francastel, propose an identifying characteristic of modern art is the deconstruction of the classic plastic space. During the two World Wars, many artists used this deconstructive process, thus reinvigorating art with ‘‘primitive’’ styles which challenged the ‘‘civilized’’ art of the day. This fascination with the ‘‘primitive’’, including art from children, amateurs, and the ‘‘mentally ill’’, is apparent in many art collections of the time. By collecting these forms of art, the collectors were supporting this new ideology in opposition to occidental rationalism. The psychiatrist Hans Prinzhorn, along with the art sellers Wilhelm Udhe and the artists Andre Breton, Jean Dubuffet and Arnulf Rainer, are a few of the notable collectors. They each influenced the progress of Modern Art; the impact of which is now evident in contemporary art. The individuality of their unique collections offers different interpretations of the marginalized ‘‘outsider art’’. By analyzing the terminologies employed by these collectors, particularly in regards to ‘‘pathological art’’, we may outline a portrait of the development of ‘‘outsider art’’ as it progressed along side modern art.

For this thesis the animal bones collected from the archaeological excavations at the ancient site of Burgaz have been analyzed for the study of animal exploitation, human diet, social differentiation and the environment of Burgaz and Dat&ccedil / a during the Classical Period. Comparison of the results with evidence from other sites to determine the extent to which there might have been local trends in animal husbandry. Because this kind of a research is not common among archaeologists specialising in the classical period the methodology and each process of the laboratory work has been set out. Burgaz/Dat&ccedil / a is a coastal settlement but sea products do not have an important place in the human diet of the Dat&ccedil / a Burgaz inhabitants. After analysis of the Burgaz bones it was determined that domestic cattle, sheep/goat, pig, horse, donkey and dog were present alongside wild goat, wild pig, fallow deer, red deer, roe deer, badger and birds as well as fish and shellfish from the sea. More than half of the bones that were identified, 220 of 430, come from floor filling levels beneath floors. It was understood that these bones were in filling materials that were brought from dump site(s). Among these bones were some worked cattle bones which have close parallels with Roman period finds at Sagalassos. Because of most of identified bones come from filling levels beneath floors it was not possible to reach definite conclusions about social hierarchy at ancient Burgaz. Sheep/goat and cattle were kept for their secondary products, such as milk, wool and power. They were slaughtered in their old age by experienced people and played an important place in diet of the Burgaz inhabitants. Pigs, on the other hand, were slaughtered when young. From the wild species found in the Classical and Hellenistic Periods it can be said that the Dat&ccedil / a environment was diverse enough to accommodate a range of wild animals whose habitat indicates the existence of forested areas (with large leafed and coniferous trees) as well as of meadows and grasslands.

This thesis presents and demonstrates procedures to model and optimize the collector field of a parabolic trough solar thermal power plant. The collector field of such a plant is universally organized into parallel loops of solar collectors. Heat transfer fluid returning from the energy conversion plant is heated to a moderately high temperature in the field. Typically fluid enters a collector loop around 270 °C and leaves at 380 °C. The fluid is then returned to the plant to generate steam. In the first part of this thesis, the collector field and the energy conversion system of a typical parabolic trough solar thermal power plant are modeled. The model is compared with actual performance data and is enhanced and verified as necessary. Originally, the collectors in the plants under consideration were provided with evacuated tube receivers of the highest feasible efficiency without much regard for cost effectiveness. In practice, these receivers have failed at an unexpected rate and need replacement. It is unlikely that a very expensive evacuated tube receiver is now the most cost effective for every location in a collector loop. In particular, a receiver optimized for 270 °C operation may not be optimal at 380 °C. For example, a relatively inexpensive receiver with a flat black absorber and no vacuum may be more cost effective in the lower temperature segments of a loop. In the second part of this thesis, a procedure for the optimum deployment of collectors is developed and demonstrated. The results of this research should be directly applicable to the refurbishment and upgrading of several of the largest solar energy plants in the world.

Domestic solar hot water units, if properly designed, are capable of providing all hot water needs in an environmentally friendly and cost-effective way. Despite 50 years of development, commercial technology has not yet achieved substantial market penetration compared to mainstream electric and gas options. Therefore, alternate designs are warranted if they can offer similar or greater performance for a comparable cost to conventional units. This study proved that such alternatives are possible by designing and testing two novel solar hot water systems (SHWS). The first system used compound parabolic collector (CPC) panels to concentrate solar energy and produce steam. The steam moved from a rooftop downward into a heat exchange pipe within a ground level water tank, heating the water, condensing and falling into a receptacle. The operation was entirely passive, since the condensate was pulled up due to the partial vacuum that occurred after system cooling. Efficiencies of up to 40% were obtained. The second system used an air heater panel. Air was circulated in open and closed loop configuration (air recycling) by means of a fan/blower motor and was forced across a compact heat exchanger coupled to a water tank. This produced a natural thermosiphon flow heating the water. Air recycling mode provided higher system efficiencies: 34% vs. 27%. The concurrent development of an analytical model that reasonably predicted heat transfer dynamics of these systems allowed 1) performance optimisation for specific input/starting operating conditions and 2) virtual design improvements. The merit of this model lay in its acceptable accuracy in spite of its simplicity. By optimising for operating conditions and parameter design, both systems are capable of providing over 30 MJ of useful domestic hot water on clear days, which equates roughly to an increase of 35°C in a 200 L water tank. This will satisfy, on average, daily hot water requirements for a 4-person household, particularly in low-latitude regions (eg. Queensland). Preliminary costing for these systems puts them on par with conventional units, with the passive, remotely coupled, low maintenance, CPC SHWS comparable to higher end models. The air heater SHWS, by contrast, was much more economical and easier to build and handle, but at the trade-off cost of 1) the need for an active system, 2) increased maintenance and running costs and 3) the requirement for a temperature control mechanism that would protect the panel body by dumping hot air trapped inside if stagnation were to occur.

Zugl.: Oldenburg, Universiẗat, Diss., 2007.

A promising and novel solar concentrator design has been thoroughly investigated and optimised. A prototype concentrator based on this novel geometry was validated using ray tracing techniques. This ray tracing demonstrated the comparative performance of this novel concentrator in regards to equivalent parabolic dishes. The effect of mirror surface normal errors on performance was established using Monte-Carlo based ray tracing code, which agreed well with the optical performance of this prototype which was determined experimentally. A need for low-cost solar cookers to replace bio-mass worldwide was identified, and the concentrator design was then developed as a low-cost solar oven. Despite existing in some number, no current design is able to achieve high performance at low-cost. An industrial partner, Dytecna, was initially involved in the process of this development of the system as a solar cooker. In support of a field trial for the solar cooker developed with Dytecna, a detailed thermal model of the oven was developed. A low-cost lightmeter was constructed and calibrated in order to measure the direct normal irradiance during the field trial in Italy. Laboratory work provided baseline results for the heating of various thermal masses in the oven. The Italian field trials provided a wealth of feedback into the design of the system and many valuable results. The solar cooker was able to bring 0.75L of water to the boil in 33 minutes with an average heat throughput of 203W. Important benchmark results and practical experience of several competing receiver materials was obtained; further lab testing provided more accurate measurements of the receivers' performances. The experiences of the Italian field trial were fed back into the design of a subsequent prototype, intended for a much larger field trial in Tanzania. Improvements in the hotplate, receiver material, and the oven were all incorporated into the design. Additionally, the structure of the solar cooker was redesigned to incorporate a low-cost wooden construction. Supporting work was conducted for the month long trial in which 8 solar cookers would be distributed to families in Tanzania. The field trial in Tanzania provided a wealth of user feedback into the design. At the same time the new solar cooker exceeded previously established performances in Italy. The new design was able to provide an average of 246W of heat to 1kg of water, which was brought to boiling point in 25 minutes. This represents a heating efficiency of 66% compared to the incident solar flux on the hotplate. In response to findings during the Tanzanian trials, further laboratory work was conducted into establishing the reflectivities of low-cost candidate mirror materials. Throughout all phases of the project the design of the solar cooker was refined and improved with the goal of a solar cooker design that could reach price-point, performance, and usability standards which would ensure market success.

Répondre aux besoins énergétiques croissants de nos sociétés et limiter leur impact sur l’environnement est un enjeu actuel majeur. De nouvelles technologies alternatives comptent tirer profit de sources d’énergie négligées. Le potentiel énergétique des eaux usées peut être exploité par de nouvelles technologies telles que les piles à combustible microbiennes (PACM). Ces piles, pouvant produire de l’énergie électrique à partir d’eaux usées, montrent une diminution de leur rendement énergétique lorsque leur taille augmente, ce qui ne permet pas encore leur application industrielle. Ces travaux de thèse visent à identifier certains verrous de ce changement d’échelle et à proposer de nouvelles directions pour leur optimisation. Une première partie s’est intéressée à l’influence des collecteurs de courant anodiques sur les performances électriques et sur le développement du biofilm électro-actif. Nous avons émis l’hypothèse qu’à grande échelle, les collecteurs de courant peuvent être un élément limitant à la production d’électricité. Pour vérifier cette hypothèse, quatre PACM avec une anode de 490 cm² connectée de différentes manières ont été étudiées. L’augmentation du nombre de collecteurs a permis une hausse de la puissance produite par les PACM. La disposition des collecteurs affecte la répartition du potentiel sur la surface d’anode et peut engendrer dans certains cas, des gradients de potentiel qui influencent la structure microbiologique du biofilm, en particulier Geobacter. Par ailleurs, des mesures d’impédance ont montré que multiplier les collecteurs augmente la capacité de double couche de l’anode et engendre un courant capacitif dont l’importance pour les performances de fonctionnement en cycles de charge/décharge est non négligeable. La suite du travail s’est attachée à prendre en compte différents aspects physiques, notamment l’aspect hydrodynamique, afin de modéliser leur fonctionnement. Pour cela, trois PACM de volumes différents ont été mises en œuvre et testées à différents débits. Les données de configuration, d’opération et de performances de ces piles ont permis de construire des modèles statistiques de régression linéaire multiple prédisant la valeur de puissance maximale. Ces deux modèles ont montré que la puissance maximale produite était principalement corrélée à la vitesse de l’électrolyte circulant dans la pile et à la contrainte de cisaillement appliquée à l’anode par le mouvement du fluide. Ces deux parties ont également montré que l’abondance dans le biofilm de Geobacter, une bactérie électro-active très répandue dans les PACM, n’était pas corrélée avec la puissance maximale. Tout en étant très abondante, son seul nombre n’explique donc pas entièrement les performances électriques d’une PACM. / Facing increasing energy needs and limiting their impact on the environment are current and major issues for society. Renewable energy development is needed and new alternative technologies could benefit from exploiting neglected energy sources, such as microbial fuel cells (MFC), for energy production. MFCs can be operated with wastewater and produce a reasonable quantity of energy at the small laboratory-scale. Unfortunately, when their size is increased, their efficiency dramatically decreases, which prevents their industrial use. This thesis aims at identifying some obstacles to scale-up of MFC and proposing new directions for its optimization. The first part of the study was focused on the influence of anodic current collectors on electrical performance and on electroactive biofilm development. Our hypothesis was that they could be a limiting factor for electricity production at large scales. To test this hypothesis, four MFCs were operated with a 490 cm² anode connected to the external circuit in a different ways. Increasing the number of collectors improved the power. Collector’s layout influenced electrical potential on the anode surface and created an electrical potential gradient on the anode and this gradient shaped the microbiological structure of the biofilm. This effect especially concerns Geobacter, whose clade G. metallireducens is favored at strongly negative potentials. In addition, impedance measurements showed that multiplying collectors increased the double layer capacitance and, thus, generated a capacitive current that was important for MFC functioning in cycles of charge/discharge and that would improve its performance. Then, MFCs were considered as bioreactors and their different aspects, notably hydrodynamics, were taken into account to model their power output. Three MFCs of different volumes were operated under continuous-flow conditions and tested at four different flow rates. Configuration, operation and performance data were used to build two multiple linear regression statistical models: the first with variables selection through LASSO, the second with dimensionless numbers created with the Vaschy-Buckingham theorem. These two data-driven models showed that the maximal power was mostly correlated to electrolyte transfer rates inside MFC chamber and to shear stress at the anode generated by fluid movement. These two major experimental projects also showed that the abundance of Geobacter, an electroactive bacteria, inside the biofilm was widespread in MFCs, but it was not correlated to maximal power. Despite its large abundance, its quantity alone does not entirely explain the performance of a MFC. In order to succeed at MFC scale-up, fundamental research on electroactive biofilms, process engineering and modeling need to be associated and generalized as empirical results and their explanation.