This thesis describes a concentrating solar power using a Stirling engine. The problems encountered during construction and operation. I focus mainly on problems derating dusting and icing. The second part of this work is the experimental design of the stand with long-term measurement of dusting depending on the reflectivity of mirrors and their degradation under various conditions. First measurement is stated and estimation of long-term results.

No description available.

Parabolrinnen-Kraftwerke sind zurzeit die am häufigsten zum Einsatz kommende und wirtschaftlichste Technologie solarthermisch konzentrierender Systeme (Concentrated Solar Power – CSP) und gehören zu den linienfokussierenden Systemen [1]. In Spanien stellen die solarthermischen Parabolrinnen-Kraftwerke Andasol 1–3 mit einer Kollektorfläche von ca. 150 Millionen m² bereits 150 MW zur Verfügung, mit denen ca. 200.000 Einwohner jährlich mit Strom versorgt werden können [2]–[4]. Das Solarfeld besteht aus ca. 150 m langen, in Reihe angeordneten Kollektoren, die aus einzelnen Parabolrinnen-Kollektormodulen zusammengefasst und im Tagesverlauf der Sonne nachgeführt werden. Die Lagerung erfolgt an den Modulrändern im Schwerpunkt des Kollektormoduls, der mit der Rotationsachse zusammenfällt. Bisher werden die Kollektoren überwiegend als filigranes Stahlfachwerk mit über die Aperturweite parabelförmig, uniaxial gekrümmten und punktuell gestützten Spiegelelementen ausgeführt. Bei der Assemblierung der Stahlfachwerke und der Spiegelelemente ist schon im Bauzustand durchgehend eine hohe Präzision gefordert, um eine maximale Solarstrahlenkonzentration der einfallenden direkten solaren Strahlung auf ein in der Fokallinie befindliches Absorberrohr sicherzustellen [5]. In diesem wird ein Wärmeträgermedium, zumeist Thermoöl, auf eine Prozesstemperatur von ca. 400 °C erhitzt. In einem nachgeschalteten konventionellen Kraftwerksblock wird mittels Dampfturbine Elektrizität erzeugt. Das bisher kommerziell meist genutzte Kollektormodul ist der EuroTrough mit einer Aperturweite von ca. 5,80 m und einer Modullänge von 12 m [6], [7] (Bild 1), welches als Benchmark für die erste Förderphase des Projekts diente. Zur Verbesserung der Wirtschaftlichkeit zielen bisherige Entwicklungen auf eine Vergrößerung der Spiegelfläche zur Steigerung des Wirkungsgrades über einen erhöhten geometrischen Konzentrationsgrad, definiert als das Verhältnis von Reflektor- zu Absorptionsfläche, ab. Module wie der UltimateTrough und der SpaceTube erreichen dies durch die Vergrößerung der Aperturweite auf 7,5 m bzw. 8 m [8], [9]. Ein alternatives Strukturkonzept aus stahlfaserverstärkten Betonfertigteilen der Schweizer Firma Airlight mit einer Aperturweite von 9,7 m besteht aus durch Luftdruck in parabolische Form gebrachten Spiegelfolien als Reflektorsystem und wurde bisher in einem Pilot-Kraftwerk in Ait-Baha, Marokko, umgesetzt [10]. Wesentliche Arbeiten der zweiten Förderphase sind daher – dem Trend zu größerer Apertur folgend – an der visionären Entwicklung von Parabolschalen mit Öffnungsweiten von bis zu 10 m ausgerichtet. [Aus: Einleitung] / Parabolic trough power plants are currently the most frequently used and most economical technology of solar thermal systems (Concentrated Solar Power – CSP) and belong to the linear focus collector types [1]. In Spain, the solar thermal parabolic trough power plants Andasol 1–3 with a collector area of approx. 150 million m² already provide 150 MW, which means that approx. 200,000 inhabitants can be annually supplied with electricity [2]–[4]. The solar field consists of approx. 150 m long collectors arranged in rows, which are combined from individual parabolic trough collector modules and track the sun during the course of the day. The bearings are located at the edges of the module in the centre of gravity of the collector module, which corresponds to the axis of rotation. Up to now, the collectors have mainly been designed as a steel framework with parabolic, uniaxially curved and pointwise supported mirror elements. During the assembly of the steel framework and the mirror elements, high precision is required throughout the manufacturing in order to ensure a maximum solar radiation concentration of the incident direct solar radiation on an absorber tube located in the focal line [5]. A heat transfer medium, usually thermal oil, is heated to a process temperature of approx. 400 °C in the absorber tube. Electricity is generated in a downstream conventional power plant unit by means of a steam turbine. The most commercially used collector module is the EuroTrough with an aperture width of approx. 5.80 m and a module length of 12 m [6], [7] (Fig. 1), which served as a benchmark for the first funding phase of the project. In order to improve economic efficiency, previous developments have aimed to increase the size of the mirror surface in order to increase efficiency by a higher geometric degree of concentration, defined as the ratio of reflector surface to absorption surface. Modules like the UltimateTrough and the SpaceTube achieve this by increasing the aperture width to 7.5 m or 8 m, respectively, [8], [9]. An alternative structural concept consisting of prefabricated steel fibre-reinforced concrete elements from the Swiss company Airlight with an aperture width of 9.7 m consists of parabolic mirror foils as a reflector brought into parabolic shape by air pressure and has already been implemented in a pilot power plant in Ait-Baha, Morocco [10]. Therefore, in line with the trend towards a larger aperture, major work in the second funding phase aims at the visionary development of parabolic shells with aperture widths of up to 10 m. [Off: Introduction]

Hybrid solar-Brayton systems utilize both solar thermal energy and supplementary renewable fuels to provide controllable and dispatchable power output, which renders them a promising way to meet the growing energy demand and reduce the carbon footprints. However, existing testing facilities for key components in such hybrid systems often fail to accomplish the testing requirements, hence impeding the improvement of the renewable energy share and the overall efficiency. A novel testing facility is urgently needed in order to thoroughly stimulate and analyze the component characteristics. This research work focuses on the development of a gas turbine simulator as an innovative testing facility for hot, pressurized components in hybrid solar-Brayton systems. The dual-flow choked nozzle based flow control has been proposed, explained, and analyzed in comparison to the single-flow layout. The basic idea of gas turbine simulator has been experimentally implemented and validated on a prototype, verifying its functionality. By incorporating a PLC-based control system, an automated gas turbine simulator has been designed and modified based on the prototype. Its performance with regard to stabilizing boundaries and tracking trajectories has been evaluated by experiments. Based on the experimental results, the gas turbine simulator prototype has proven its ability to establish controllable boundary conditions and migrate operating points for the impinging receiver. Through manual adjustments, excellent quasi-steady state performance has been obtained, with the precision for pressure control reaching ±0.005 bar at ambient temperature and ±0.015 bar at high temperature of 797.1-931.5 °C. The manual operation time has been identified at 23.1 s for establishing the receiver boundaries, and at 70 s for changing operating points. With the help of the proposed control strategy, the automated gas turbine simulator has eliminated the need for manual adjustments, and demonstrated the ability to maintain the safe and convergent operation for the receiver. The performance in boundary condition stabilization has been satisfactory, with enhanced steady-state accuracy comparing to the prototype by virtue of the PID controller. The transient-state fluctuations in pressure control have been effectively restrained within an acceptable region with deviations of ±0.018 bar to ±0.076 bar from the desired 2.400 bar operating pressure. The capability of tracking linear and nonlinear trajectories has also been testified, with the precision level between ±0.023 bar and ±0.037 bar. Finally, in view of the good stability, high precision, and rapid response manifested in the experimental studies, the gas turbine simulator has validated its ability to imitate the steady and transient characteristics of gas turbines on the boundaries of the test section. It also grants the possibilities to conduct control variable studies and wide-range transition studies. The gas turbine simulator is a suitable testing facility for the key components in hybrid solar-Brayton systems. / Hybrid solenergi-Brayton-system använder både solvärmeenergi och kompletterande förnybara bränslen för att ge kontrollerbar och sändbar effekt, vilket gör dem till ett lovande sätt att möta den växande energiefterfrågan och minska koldioxidavtrycken. Men befintliga testanläggningar för nyckelkomponenter i sådana hybridsystem misslyckas ofta med att uppfylla testkraven, vilket hindrar förbättringen av andelen förnybar energi och den totala effektiviteten. En ny testanläggning behövs omgående för att grundligt stimulera och analysera komponentens egenskaper. Detta forskningsarbete fokuserar på utvecklingen av en gasturbinsimulator som en innovativ testanläggning för varma, trycksatta komponenter i hybridsolar-Brayton-system. Den dubbelströms strypta munstycksbaserade flödeskontrollen har föreslagits, förklarats och analyserats i jämförelse med enkelflödeslayouten. Den grundläggande idén med gasturbinsimulator har experimentellt implementerats och validerats på en prototyp, vilket verifierar dess funktionalitet. Genom att införliva ett PLC-baserat styrsystem har en automatiserad gasturbinsimulator designats och modifierats utifrån prototypen. Dess prestanda med avseende på stabilisering av gränser och spårning av banor har utvärderats genom experiment. Baserat på de experimentella resultaten har prototypen av gasturbinsimulatorn bevisat sin förmåga att upprätta kontrollerbara gränsförhållanden och migrera arbetspunkter för den träffande mottagaren. Genom manuella justeringar har man erhållit utmärkt prestanda i nästan konstant tillstånd, med precisionen för tryckkontroll som når ±0,005 bar vid omgivningstemperatur och ±0,015 bar vid hög temperatur på 797,1-931,5 °C. Den manuella drifttiden har identifierats till 23,1 s för att fastställa mottagargränserna och till 70 s för att byta arbetspunkter. Med hjälp av den föreslagna styrstrategin har den automatiserade gasturbinsimulatorn eliminerat behovet av manuella justeringar och visat förmågan att upprätthålla en säker och konvergent drift för mottagaren. Prestandan vid gränstillståndsstabilisering har varit tillfredsställande, med förbättrad steady-state noggrannhet jämfört med prototypen tack vare PID-regulatorn. De transienta tillståndsfluktuationerna i tryckregleringen har effektivt begränsats inom ett acceptabelt område med avvikelser på ±0,018 bar till ±0,076 bar från det önskade 2,400 bar arbetstrycket. Förmågan att spåra linjära och olinjära banor har också vittnats, med precisionsnivån mellan ±0,023 bar och ±0,037 bar. Slutligen, med tanke på den goda stabiliteten, höga precisionen och snabba responsen som manifesteras i de experimentella studierna, har gasturbinsimulatorn validerat sin förmåga att imitera de stabila och transienta egenskaperna hos gasturbiner på gränserna för testsektionen. Det ger också möjlighet att genomföra kontrollvariabelstudier och omfattande övergångsstudier. Gasturbinsimulatorn är en lämplig testanläggning för nyckelkomponenterna i hybridsolar-Brayton-system.

The objective of this thesis was to investigate the potential for introducing a concentrating solar thermal (CST) central receiver plant system based on flexible heliostats - HelioPods - to provide high-temperature process heat in industrial applications. A CST plant system was designed in MATLAB, optically simulated for three design days in the ray-tracing software Tonatiuh and further analyzed in MATLAB by interpolating the results for each hour of the year. A case study was made on introducing a CST plant system based on HelioPods in a South African manganese sinter plant. The study included an investigation of the profitability of up- and downsizing the heliostat field annually with fluctuating heat demand. A circular heliostat field was modelled for the chosen location. The final field had a radius of 53 meters with the receiver located 60% from the field centre. The storage size was 16 demand hours and 17 plants were required. The results showed that 88% of the annual heat demand could be covered by solar heat in the design year. The marketing approach used for the following years was that the heat demand covered by solar heat should never be below the share at the first year, despite the predicted fluctuations in demand. Thus, a minimum solar share of 88% was used as a strategy for annual up- and downsizing of the fields throughout the investigated period of 25 years. That resulted in a field radius differing between 52 and 55 meters. The payback period of the final system was 4.35 years, the NPV was 54.33 MUSD over a period of 25 years and the LCOH was 35.39 USD/MWht. However, it was found that the profitability of the system was sensitive to the different scenarios for predicted future diesel prices, this since the pricing of the solar heat was set to 90% of the diesel price. The results in this thesis show that a CST plant system based on HelioPods is a suitable solution to supply high-temperature process heat to industrial applications. It also shows that the HelioPods can unlock potential for flexibility with changing production patterns in the industry of implementation. The results from the study can be used also for other industries with similar temperature range and heat demand. Thus, it could be argued that the implementation of a HelioPod based CST plant system also can be suitable for other industries located in high-DNI areas with dependency on conventional fuels and steady production throughout the whole day. / Syftet med denna uppsats var att undersöka potentialen för implementering av koncentrerad termisk solvärme (CST) från ett soltorn med ett heliostatfält baserat på flexibla heliostater - HelioPods – för att generera högtempererad processvärme för industriell tillämpning. Ett CST-system designades i MATLAB, simulerades för tre designdagar i det optiska ray-tracingprogrammet Tonatiuh och analyserades sedan åter i MATLAB genom att interpolera de genererade resultaten för årets alla timmar. En fallstudie av ett CST-system baserat på HelioPods i ett sydafrikanskt sinterverk för mangan genomfördes därefter. Studien innehöll en undersökning av lönsamheten av årlig ökning och minskning av heliostatfältet vid fluktuerande värmebehov. Ett cirkulärt heliostatfält modellerades för den valda platsen. Det slutgiltiga fältet hade en radie om 53 meter med mottagaren placerad 60% från fältets mittpunkt. Storleken på lagringsfaciliteten var 16 timmar av full tillförsel och antalet verk uppgick till 17. Resultaten visade att 88% av det årliga värmebehovet kunde förses med solvärme under designåret. Marknadsstrategin för de resterande åren var att den procentuella andelen solvärme aldrig skulle vara lägre än under designåret, oberoende av fluktuationer i värmebehovet på grund av ändrad produktion. Således sattes 88% solvärme som ett minimikrav och utgjorde strategin för den årliga ökningen och minskningen av fältet för den undersökta perioden av 25 år. Det resulterade i en fältradie mellan 52 och 55 meter. Återbetalningstiden för det slutgiltiga fältet var 4.35 år, nuvärdesberäkningen av det framtida kassaflödet var 54.22 miljoner USD över en 25-årsperiod och produktionskostnaden för värme (LCOH) var 35.39 USD/MWht. Dock var systemets lönsamhet känslig för de olika prognoser av framtida dieselpriser som undersöktes, detta eftersom priset för solvärme sattes till 90% av dieselpriset. Resultaten i denna uppsats visar att ett CST-system baserat på HelioPods är en lämplig lösning för att generera högtempererad processvärme för industriell tillämpning. De visar även att HelioPods kan öka potentialen för flexibilitet vid förändringar i produktionsmönstret i vederbörande industri. Resultaten kan även användas i andra industrier med likartade temperaturer och värmebehov. Hävdas kan således att implementation av ett CST-system kan vara lämpligt även för andra industrier belägna i områden med högt DNI som är beroende på konventionella energikällor och har jämn produktion dygnet runt.

Seres humanos com danos nos corpos mamilares exibem prejuízos no funcionamento da memória episódica. O presente estudo investigou a possível participação do núcleo mamilar medial (MM), estrutura densamente inervada por fibras imunorreativas ao hormônio concentrador de melanina (MCH) potencialmente envolvida no comportamento alimentar, em processos de evocação de memórias sobre locais em que alimento foi previamente encontrado, em ratos. Investigou-se ainda seu envolvimento na memória espacial motivada aversivamente, por meio do labirinto aquático de Morris, e em processos de ansiedade, por meio do labirinto em cruz elevado. Descreve-se uma tarefa comportamental envolvendo busca alimentar orientada por memória espacial em ratos, funcionalmente análoga ao teste de aprendizagem de pares associados, utilizado para avaliar memória episódica em seres humanos. Ratos treinados a escavar numa arena para obter alimento foram expostos ao pareamento de um determinado sabor, e.g., amendoim, com um local da arena e, numa segunda tentativa, ao pareamento de um outro sabor, e.g., avelã, com um local diferente da mesma arena. Antes de uma terceira tentativa, ainda na caixa de espera, os animais receberam uma amostra de amendoim ou avelã. Então, inseridos na arena para uma terceira tentativa, deveriam procurar e escavar por alimento enterrado no local sinalizado pela amostra. As associações sabor-local, a seqüência das associações, os locais do pareamento e a amostra oferecida antes da terceira tentativa, variaram quase aleatoriamente a cada dia. O treinamento dos animais para a aquisição da tarefa foi prolongado. O número de visitas e o tempo de permanência no local da arena sinalizado pela amostra foram significativamente maiores em relação aos parâmetros correspondentes ao local pareado com alimento mas não sinalizado pela amostra, quando o intervalo de tempo entre a 2ª e 3ª tentativas foi 60 ou 120 minutos; Testes de Avaliação sem oferta de alimento na arena na 3ª tentativa, permitiram excluir a hipótese de que os animais desempenharam essa tarefa com base em estímulos olfativos, levando à conclusão que o fizeram com base na memória das associações sabor-local. Ratos com danos seletivos do MM, induzidos pela aplicação tópica, micro-iontoforética, de N-Metil-D-Aspartato (NMDA), testados na tarefa de pares associados sabor-local, não exibiram prejuízo de desempenho em relação aos animais controle. Análises adicionais revelaram que houve uma redução da busca por alimento em ambos os grupos (lesado e controle) nos testes pós-operatórios, em relação ao seu próprio desempenho nos testes pré-operatórios; porém, essa redução foi mais acentuada em relação ao local sinalizado pela amostra, particularmente nos animais do grupo lesado. Estes resultados, embora não conclusivos, podem representar indícios em favor da idéia de que o MM estaria envolvido numa circuitaria relacionada à memória espacial voltada à busca alimentar. Mais estudos seriam necessários para avaliar essa possibilidade. Além disso, esses animais não exibiram qualquer prejuízo no teste de memória de referência espacial no labirinto aquático de Morris e no paradigma do teste e re-teste no labirinto em cruz elevado, sugerindo que esse tipo de lesão não leva a deficiência no funcionamento da memória espacial motivada por estimulação aversiva, na memória aversiva por espaços abertos ou nos mecanismos responsáveis pela ansiedade. / Human beings with damage to the mammillary bodies exhibit episodic memory disruption. This study investigated the potential participation of the medial mammillary nucleus (MM), a structure that receives a high density of melaninconcentrating hormone immunoreactive fibers (MCH) potentially involved in food intake, in processes of retrieval of memory about places where food was previously found, in rats. In addition, we investigated the possible involvement of this brain structure in both aversively motivated spatial memory, using the Morris´ water maze, and in anxiety, using the elevated plus maze. A behavioral task involving search for food guided by spatial memory, in rats, functionally analogous to the paired-associate learning task used for studying episodic memory in humans, was described. Rats trained to dig for food in an arena were exposed both to the pairing of a taste, peanut, with a specific place in the arena and, in a second trial, to the pairing of another taste, hazelnut, with another place in the arena. Immediately before a third trial, while still in the waiting box, the animals received a sample of either peanut or hazelnut. Then, they were inserted into the arena for a third trial and could search and dig for food buried in the place previously associated with the sample. The taste-place associations, sequence of associations, pairing places and sample offered before the third trial, were all varied quasi-randomly every day. The animals took extensive training to learn this task. It was found that the number of visits and the time spent in the place indicated by the sample were significantly greater as compared to the corresponding parameters of the place previously associated with a taste but not indicated by the sample, when the time interval between the second and the third trials was both 60 and 120 min; probe tests with no food in the arena in the third trial allowed to exclude the hypothesis that the rats were performing the task relying on olfactory cues, leading to the conclusion that the animals performed the task relying on the memory for the associations tastefood. Rats with selective damage to the MM, induced by topic, microiontophoretic, injections of N-Methyl-D-Aspartate (NMDA), tested in the taste-place pairedassociate learning task, did not exhibit any disruption of performance relative to the controls. Additional analyses revealed that both MM and control subjects exhibited a reduction of food search during the post-operatory tests as compared to their own performance in pre-operatory tests; however, this reduction was stronger towards the place indicated by the sample, particularly for the animals subjected to MM damage. Even though not conclusive, these results may suggest that the MM might be involved in search for food guided by spatial memory. More studies would be required to evaluate this possibility. Further, these rats did not exhibit any disruption of performance in the reference memory test in the water maze and in the test/re-test elevated plus maze, suggesting that this type of damage does not disrupt aversively motivated spatial memory, open-space aversive memory and anxiety.

Seres humanos com danos nos corpos mamilares exibem prejuízos no funcionamento da memória episódica. O presente estudo investigou a possível participação do núcleo mamilar medial (MM), estrutura densamente inervada por fibras imunorreativas ao hormônio concentrador de melanina (MCH) potencialmente envolvida no comportamento alimentar, em processos de evocação de memórias sobre locais em que alimento foi previamente encontrado, em ratos. Investigou-se ainda seu envolvimento na memória espacial motivada aversivamente, por meio do labirinto aquático de Morris, e em processos de ansiedade, por meio do labirinto em cruz elevado. Descreve-se uma tarefa comportamental envolvendo busca alimentar orientada por memória espacial em ratos, funcionalmente análoga ao teste de aprendizagem de pares associados, utilizado para avaliar memória episódica em seres humanos. Ratos treinados a escavar numa arena para obter alimento foram expostos ao pareamento de um determinado sabor, e.g., amendoim, com um local da arena e, numa segunda tentativa, ao pareamento de um outro sabor, e.g., avelã, com um local diferente da mesma arena. Antes de uma terceira tentativa, ainda na caixa de espera, os animais receberam uma amostra de amendoim ou avelã. Então, inseridos na arena para uma terceira tentativa, deveriam procurar e escavar por alimento enterrado no local sinalizado pela amostra. As associações sabor-local, a seqüência das associações, os locais do pareamento e a amostra oferecida antes da terceira tentativa, variaram quase aleatoriamente a cada dia. O treinamento dos animais para a aquisição da tarefa foi prolongado. O número de visitas e o tempo de permanência no local da arena sinalizado pela amostra foram significativamente maiores em relação aos parâmetros correspondentes ao local pareado com alimento mas não sinalizado pela amostra, quando o intervalo de tempo entre a 2ª e 3ª tentativas foi 60 ou 120 minutos; Testes de Avaliação sem oferta de alimento na arena na 3ª tentativa, permitiram excluir a hipótese de que os animais desempenharam essa tarefa com base em estímulos olfativos, levando à conclusão que o fizeram com base na memória das associações sabor-local. Ratos com danos seletivos do MM, induzidos pela aplicação tópica, micro-iontoforética, de N-Metil-D-Aspartato (NMDA), testados na tarefa de pares associados sabor-local, não exibiram prejuízo de desempenho em relação aos animais controle. Análises adicionais revelaram que houve uma redução da busca por alimento em ambos os grupos (lesado e controle) nos testes pós-operatórios, em relação ao seu próprio desempenho nos testes pré-operatórios; porém, essa redução foi mais acentuada em relação ao local sinalizado pela amostra, particularmente nos animais do grupo lesado. Estes resultados, embora não conclusivos, podem representar indícios em favor da idéia de que o MM estaria envolvido numa circuitaria relacionada à memória espacial voltada à busca alimentar. Mais estudos seriam necessários para avaliar essa possibilidade. Além disso, esses animais não exibiram qualquer prejuízo no teste de memória de referência espacial no labirinto aquático de Morris e no paradigma do teste e re-teste no labirinto em cruz elevado, sugerindo que esse tipo de lesão não leva a deficiência no funcionamento da memória espacial motivada por estimulação aversiva, na memória aversiva por espaços abertos ou nos mecanismos responsáveis pela ansiedade. / Human beings with damage to the mammillary bodies exhibit episodic memory disruption. This study investigated the potential participation of the medial mammillary nucleus (MM), a structure that receives a high density of melaninconcentrating hormone immunoreactive fibers (MCH) potentially involved in food intake, in processes of retrieval of memory about places where food was previously found, in rats. In addition, we investigated the possible involvement of this brain structure in both aversively motivated spatial memory, using the Morris´ water maze, and in anxiety, using the elevated plus maze. A behavioral task involving search for food guided by spatial memory, in rats, functionally analogous to the paired-associate learning task used for studying episodic memory in humans, was described. Rats trained to dig for food in an arena were exposed both to the pairing of a taste, peanut, with a specific place in the arena and, in a second trial, to the pairing of another taste, hazelnut, with another place in the arena. Immediately before a third trial, while still in the waiting box, the animals received a sample of either peanut or hazelnut. Then, they were inserted into the arena for a third trial and could search and dig for food buried in the place previously associated with the sample. The taste-place associations, sequence of associations, pairing places and sample offered before the third trial, were all varied quasi-randomly every day. The animals took extensive training to learn this task. It was found that the number of visits and the time spent in the place indicated by the sample were significantly greater as compared to the corresponding parameters of the place previously associated with a taste but not indicated by the sample, when the time interval between the second and the third trials was both 60 and 120 min; probe tests with no food in the arena in the third trial allowed to exclude the hypothesis that the rats were performing the task relying on olfactory cues, leading to the conclusion that the animals performed the task relying on the memory for the associations tastefood. Rats with selective damage to the MM, induced by topic, microiontophoretic, injections of N-Methyl-D-Aspartate (NMDA), tested in the taste-place pairedassociate learning task, did not exhibit any disruption of performance relative to the controls. Additional analyses revealed that both MM and control subjects exhibited a reduction of food search during the post-operatory tests as compared to their own performance in pre-operatory tests; however, this reduction was stronger towards the place indicated by the sample, particularly for the animals subjected to MM damage. Even though not conclusive, these results may suggest that the MM might be involved in search for food guided by spatial memory. More studies would be required to evaluate this possibility. Further, these rats did not exhibit any disruption of performance in the reference memory test in the water maze and in the test/re-test elevated plus maze, suggesting that this type of damage does not disrupt aversively motivated spatial memory, open-space aversive memory and anxiety.

Οι ανανεώσιμες πηγές ενέργειας (ΑΠΕ), όπως η ηλιακή ενέργεια, μπορούν να προσφέρουν εναλλακτικούς τρόπους παραγωγής ενέργειας. Κάθε μορφή ΑΠΕ έχει τις δικές της ιδιομορφίες και μπορούν να εφαρμοστούν είτε σε μεγάλες εγκαταστάσεις παραγωγής ηλεκτρικής και θερμικής ενέργειας είτε σε μικρότερες μονάδες όπως στα κτίρια. Ενδιαφέρον παρουσιάζει η συνδυασμένη αξιοποίηση των παραπάνω ενεργειακών πηγών, ιδίως για την κάλυψη των ηλεκτρικών και θερμικών αναγκών των κτιρίων.Αντικείμενο αυτής της διπλωματικής εργασίας είναι η μελέτη συγκεντρωτικών συστημάτων χαμηλής συγκέντρωσης και των παραγόντων που επηρεάζουν την λειτουργία τους, με την χρήση τριών γεωμετρικών συγκεντρωτικών μέσων, τα οποία είναι: το σύστημα V-Trough, το σύστημα Fresnel γραμμικής εστίας και το κυλινδροπαραβολικό σύστημα γραμμικής εστίας, με χρήση συμβατικών φωτοβολταϊκών για την παραγωγή ηλεκτρικής ισχύος. Όμως, από το την προσπίπτουσα ηλιακή ακτινοβολία που συγκεντρώνεται στον απορροφητή, ένα μέρος μετατρέπεται σε ηλεκτρική ενέργεια, ενώ το υπόλοιπο μεταδίδεται στο περιβάλλον με την μορφή θερμότητας. Έτσι, περαιτέρω μελέτη έγινε με βάση την δημιουργία υβριδικού συγκεντρωτικού φωτοβολταϊκού/θερμικού συστήματος, ταυτόχρονης παραγωγής ηλεκτρικής και θερμικής ενέργειας χρησιμοποιώντας την βέλτιστη γεωμετρία, το οποίο θα μπορούσε να δώσει ικανοποιητικά ποσά θερμικής ενέργειας, χωρίς να ζημιώνεται η ηλεκτρική και το αντίστροφο, κάτι που θα καθιστούσε τα συστήματα αυτά ενεργειακώς και οικονομικώς πιο ανταγωνιστικά.Τα πειραματικά αποτελέσματα περιλαμβάνουν διαγράμματα ηλεκτρικών αποδοτικοτήτων των πειραματικών συστημάτων καθώς και των μεγεθών Pmax, Vpmax, Voc, Ιpmax, Ιsc, συναρτήσει της θερμοκρασίας λειτουργίας Tpv, κάτω από σταθερή ακτινοβολία G, θερμικών αποδόσεων, προφίλ κατανομών συγκεντρωτικής ακτινοβολίας καθώς και χαρακτηριστικές καμπύλες I-V για καθένα απ αυτά. / The renewable energy sources (RES) like solar energy, can offer an alternative solution to power production. Each form of RES, has its own specifications and they can be applied in big installations of electric and thermal energy production or in smaller units as the buildings. This thesis investigates the performance of three different types of solar concentrating systems, which are: the V-Trough system, the linear Fresnel system and the Parabolic Trough system, with usage of common photovoltaics, instead of concentrating photovoltaics, for the electricity production.However, only a small part of the incoming solar radiation it is changed by an absorber into electric energy, while the rest is transmitted to the environment with the form of heat. Thus, further study has been done with base of the creation of a hybrid concentrating photovoltaic/thermal system, with simultaneous production of electric and thermal energy using the most optimal geometry. This could give satisfactory sums of thermal energy, without affecting the production of electric energy and vice versa, something that would render this systems economically more competitively.The experimental results include diagrams with the electric performance of the experimental systems as well as values of Pmax, Vpmax, Voc, Ipmax, Isc, associated with the operating temperature Tpv, under constant radiation G, thermal output, distribution profiles of the concentrating radiation as well as characteristic curves I-V for each one of them.

L'énergie solaire est connue pour sa nature intermittente par rapport aux ressources d’énergie fossile. Cette observation souligne la nécessité d'utilisation d’un système de stockage d'énergie thermique. Le système de stockage thermocline est considéré comme un système de stockage rentable. La présente thèse vise à étudier le potentiel des roches basaltiques et siliceuses comme des candidates matériaux de stockage pour les centrales solaires concentrées. Les études expérimentales des propriétés thermo-physiques et thermomécaniques de ces roches à des températures allant jusqu'à 1000°C montrent que ces roches offrent de bonnes propriétés thermiques par rapport aux matériaux classiques de stockage. L'analyse du système de stockage thermocline sur un lit de roches à air direct est réalisée par une approche numérique. En outre, cette recherche vise également à évaluer l’impact environnementale de ce type de système de stockage en effectuant une analyse comparative de son cycle de vie. Enfin, une étude complémentaire réalisée dans le but de produire une carte d'indice de pertinence a permis d’identifier les zones les plus appropriées pour la construction des centrales solaires en Egypte. L'originalité de cette approche alternative pour le stockage d'énergie thermique est qu’elle combine la performance et la disponibilité des matériaux de stockage tout en réduisant leurs impacts environnementaux et financiers. / Compare to fossil fuel energy resources, solar energy is known for its intermittent nature. This observation highlights the need for the use of a thermal energy storage system. The thermocline storage system is considered as a cost-effective storage system. This thesis aims to study the potential of basalt and silex rocks as candidate storage materials for concentrated solar power plants. Experimental studies of the thermo-physical and thermo-mechanical properties of these rocks at temperatures up to 1000°C show that these rocks offer good thermal properties compared with conventional storage materials. The analysis of the thermocline storage system of air rock-packed bed is carried out using a numerical approach. This research also aims to assess the environmental impact of this type of storage system by conducting a comparative analysis of its life cycle. Finally, a complementary study carried out with the aim of producing a relevance index map made it possible to identify the most suitable areas for the construction of solar power plants in Egypt. The originality of this alternative approach for thermal energy storage is that it combines the performance and availability of storage materials while reducing their environmental and financial impacts.

Concentrating Solar Power (CSP) is one of the most promising renewable energybased electricity generation technologies to deal with the increasing demand of power consumption and environmental sustainability. With the aim of achieving the 2020 SunShot cost target for CSP of 60 USD/MWh, the United States Department of Energy presented, in May 2018, the Gen3 CSP initiative. In particular, the CSP Gen3 Liquid-Phase Pathway proposes to design a CSP system adopting liquid sodium as Heat Transfer Fluid (HTF) in the receiver, advanced high-temperature molten chloride salt as storage fluid and supercritical CO2 (sCO2) Brayton cycle as power cycle. Within this framework, the aim of this master thesis was to design the sodium-chloride salt Heat Exchanger (HX) by developing both a heat exchanger model and a sodiumsalt-sCO2 system model. To pursue these purposes, a completely new Modelica-based HX model was developed and added to the SolarTherm library. Furthermore, as an extension of earlier models, the sodium-salt-sCO2 CSP system (NaSaltsCO2System) was implemented in SolarTherm, by incorporating the HX model and linking it with other new and existing component models. As for the HX, a general model was developed for shell and tube heat exchangers, based on the TEMA guidelines, with the possibility of being customized in terms of media adopted, constraints, boundary conditions, and correlations. The model performs an optimization in order to select the internal geometry configuration that optimizes a user-defined objective-function. By employing the implemented HX model in the NaSaltsCO2System, the sodium-salt heat exchanger was designed aiming at minimizing the Levelized Cost of Electricity (LCOE), providing a complete geometry description, and an estimation of the performances and costs. The resulting NaSaltsCO2System model was found to be robust and able to perform annual simulations that allowed to estimate the energy performances of the CSP plant, as well as the LCOE. Considering the sodium-salt-sCO2 CSP system characterized by a receiver capacity of 543 MWth, 12 hours of Thermal Energy Storage (TES), and a 100 MWe power block, the LCOE resulted equal to 72.66 USD/MWh. The sodium-salt HX design that minimizes the LCOE resulted in a single-shell/single tube pass configuration, with vertical alignment, characterized by an overall height of 15 m, and a shell diameter of 1.8 m. It represents the 3.2% of the total capital cost of the plant. An interesting system-level optimization was then carried out on the combined receiver-heat exchanger block. It regarded the variation of the Log Mean Temperature Difference (LMTD) of the HX and highlighted the possibility to drop the LCOE down to 68.54 USD/MWh. The techno-economic investigations and the sensitivity analysis showed the flexibility and robustness of the HX model, as well as the importance of the NaSaltsCO2System. The latter lays the groundwork to explore potential improvements of this new generation of CSP systems, which can play a fundamental role in the future global energy mix. / Termisk solkraft (CSP) är en av de mest lovande elproduktionsteknologierna baserade på förnybar energi. Den kan bidra till hanteringen av den ökande efterfrågan på energi och miljömässig hållbarhet. I syfte att uppnå 2020 SunShot-kostnadsmålet för CSP på 60 USD/MWh presenterade USA:s energidepartement Gen3 CSPinitiativet. I synnerhet föreslår CSP Gen Liquid-Phase Pathway att utforma ett CSPsystem som använder flytande natrium som värmeöverföringsvätska i mottagaren, smält kloridsalt med hög temperatur som lagringsvätska, samt superkritisk CO2 (sCO2) Brayton-cykel som kraftcykel. Syftet för detta examensarbete var att utforma natriumkloridsaltets primära värmeväxlare genom att utveckla både en värmeväxlarmodell (HX) modell och en natriumsalt-sCO2-systemmodell. För att fullfölja dessa syften utvecklades HX-modellen först, sedan implementerades natriumsalt-sCO2 CSP-systemet NaSaltsCO2System. Båda verktygen utvecklades med hjälp av Modelica som programmeringsspråk. De finns nu tillgängliga i det öppna SolarTherm-biblioteket. När det gäller HX utvecklades en allmän modell för skal- och rörvärmeväxlare med möjligheten att anpassas när det gäller antagna medium, begränsningar, gränsvillkor och korrelationer. Dessutom utförde modellen en optimering för att välja den interna geometri-konfigurationen som optimerar en användardefinierad objektiv-funktion. Genom att använda den implementerade HX-modellen i NaSaltsCO2System designades natriumsalt-värmeväxlaren, vilket gav en fullständig konfiguration-beskrivning och en uppskattning av prestanda och kostnader. Den utvecklade NaSaltsCO2System-modellen visade sig vara robust och kapabel till att utföra simuleringar på årsbasis. Detta gjorde det möjligt att uppskatta CSP-anläggningens energiprestanda samt LCOE. Det utvecklade natriumsalt-sCO2 CSP-systemet som känneteckna des av en mottagarkapacitet på 543 MWth, 12 timmars TES och ett 100 MWe power block, resulterade i en LCOE på 72.66 USD/MWh. Natrium-salt HX-konstruktionen som minimerade LCOE resulterade i en enskalig/enkel rörpassningskonfiguration, med vertikal inriktning, kännetecknad av en total höjd av 15 m och en skaldiameter på 1.8 m. Det motsvarade 3.2% av anläggningens totala kapitalkostnad. Den mest intressanta systemoptimeringen genomfördes på det kombinerade blocket bestående av mottagare och värmeväxlare. Den behandlade variationen av HX:s LMTD och framhöll möjligheten att sänka LCOE till 68.54 USD/MWh. De teknisk-ekonomiska undersökningarna och känslighetsanalysen visade flexibiliteten och robustheten i HX-modellen, liksom vikten av NaSaltsCO2Systemet. Den senare lägger grunden för att utforska potentiella förbättringar av denna nya generation av CSP-system, som kan spela en grundläggande roll i den framtida globala energimixen.