The research that is presented in this thesis can be divided into two major parts. The first part concerns longitudinally pumped, bulk Er-Yb lasers. In these lasers, the main limitation is the thermal shortcomings of the phosphate glass host material. From the laser experiments and the spectroscopic measurements on crystalline host materials, as well as an investigation to bring further light to the physical background of the involved dynamics, the thesis presents some novel results that contribute to the search for a crystalline replacement. The second part concerns novel laser concepts applied to Yb-doped double tungstate lasers. Different crystal orientations are investigated, such as an athermal orientation for reduced thermal lensing and a conical refraction orientation for complete polarization tuning. Furthermore, the introduction of volume Bragg gratings in the cavity enables wide spectral tuning ranges and extremely low quantum defects. Regarding the first part, the main results are the achievement of 15 % slope efficiency in a monolithic, continuous-wave Yb:GdCOB laser and the achievement of Q-switching of the same laser. The Q-switched pulse durations were around 5-6 ns and the Q-switched slope efficiency was 11.6 %. For both lasers, a maximum output power of 90 mW was obtained, which is close to ordinary glass lasers under similar conditions. A spectroscopic investigation into the Er,Yb-codoped double tungstates was also performed and the results have enabled mathematical modeling of the fluorescence dynamics in these materials. Finally, the temperature dependence of the dynamics in Er,Yb:YAG was studied and the results have given some insight into the physical background of the mechanisms involved. Regarding the second part, different end-pumped Yb:KReW laser cavities were constructed to demonstrate the different concepts. With a laser crystal cut for propagation along the athermal direction at 17º angle clockwise from the dielectric direction Nm, the thermal lens could be reduced by 50 %. In these experiments the maximum output power was 4 W at 60 % slope efficiency. In another cavity incorporating a volume Bragg grating in a retroreflector set-up, the wavelength could be continuously tuned between 997 - 1050 nm. The spectral bandwidth was 10 GHz and the peak output power was 3 W. The same output power could also be obtained at 1063 nm with the grating positioned as an output coupler instead. If, on the other hand, the grating was positioned as an input coupler, 3.6 W output power at 998 nm was obtained at a quantum defect of only 1.6 %. Furthermore, using a crystal oriented for propagation along an optic axis, internal conical refraction could be used to establish arbitrary control of the polarization direction as well as the extinction ratio. Even unpolarized light could be enforced despite the highly anisotropic medium. With this configuration, the maximum output power was 8.6 W at 60 % slope efficiency which equals the performance of a reference crystal with standard orientation. The completely novel concepts of laser tuning with Bragg grating retroreflectors, of low quantum defect through Bragg grating input couplers and of polarization tuning by internal conical refraction can all easily be applied to several other laser materials as well. / QC 20100713

Η παρούσα έρευνα πραγματοποιήθηκε στο Εργαστήριο Ρευστομηχανικής και Εφαρμογών Αυτής του Τμήματος Μηχανολόγων και Αεροναυπηγών Μηχανικών του Πανεπιστημίου Πατρών και χρηματοδοτήθηκε από το πρόγραμμα «Ηράκλειτος ΙΙ» στα πλαίσια του Επιχειρησιακού Προγράμματος Εκπαίδευση και Δια Βίου Μάθησης, Επένδυση στη κοινωνία της γνώσης. Ο έλεγχος του θερμικού φορτίου στη λειτουργία διαφόρων μηχανολογικών ή ηλεκτρολογικών συστημάτων από συστήματα ψύξης, γίνεται όλο και πιο αναγκαίος στη σημερινή εποχή. Τα συστήματα ψύξης κατηγοριοποιούνται σε ενεργά, που μεταφέρουν ενέργεια υπό μορφή αισθητής θερμότητας μέσω ενός υγρού και σε παθητικά συστήματα ψύξης που χρησιμοποιούν τη λανθάνουσα θερμότητα εξάτμισης του ρευστού λειτουργίας που κυκλοφορεί στην εγκατάσταση, εξαιτίας των τριχοειδών δυνάμεων που αναπτύσσονται από την ύπαρξη πορώδους υλικού. Τα παθητικά συστήματα ψύξης προτιμώνται έναντι των ενεργών, καθώς έχουν τη δυνατότητα να απάγουν περισσότερη θερμότητα, παρουσιάζουν πιο αξιόπιστη λειτουργία, εξαιτίας της έλλειψης κινητών μερών και τέλος, εμφανίζουν μεγαλύτερη διάρκεια ζωής. Μία διάταξη που προσφέρει δυνατότητες ελέγχου του θερμικού φορτίου είναι το κύκλωμα τριχοειδούς αντλίας, Capillary Pump Loop (CPL), που αποτέλεσε και το αντικείμενο μελέτης στην παρούσα διδακτορική διατριβή. Αξιοποιεί τις τριχοειδείς δυνάμεις που αναπτύσσονται στη διεπιφάνεια υγρής-αέριας φάσης του ρευστού λειτουργίας στο πορώδες υλικό που περικλείει ο εξατμιστής στο εσωτερικό του, καθώς και τη λανθάνουσα θερμότητα εξάτμισης και συμπύκνωσης του ρευστού. Με τον τρόπο αυτό, επιτυγχάνει την κυκλοφορία του ρευστού λειτουργίας στην εγκατάσταση, χωρίς την παρουσία μηχανικής αντλίας, και τη μεταφορά των απαιτούμενων θερμικών φορτίων σε μεγάλες αποστάσεις. Ένα κύκλωμα τριχοειδούς αντλίας αποτελείται από έναν εξατμιστή, ένα συμπυκνωτή, τις γραμμές υγρού και ατμού καθώς και ένα ρεζερβουάρ. Από τη μέχρι τώρα έρευνα είχαν μελετηθεί πειραματικά αρκετά μοντέλα CPL, δίνοντας ιδιαίτερη έμφαση στη διαδικασία εκκίνησης της διάταξης καθώς και στις συνθήκες μόνιμης λειτουργίας. Σε όλα αυτά τα μοντέλα το θερμικό φορτίο επιβάλλονταν μέσω ηλεκτρικών αντιστάσεων. Στην παρούσα διερεύνηση η διάταξη ενσωμάτωσε τη δυνατότητα η προσφερόμενη θερμότητα να παρέχεται και από την ηλιακή ακτινοβολία αναπτύσσοντας έναν εργαστηριακό ηλιακό προσομοιωτή. Προκειμένου να βελτιώσουμε τη συγκέντρωση της ακτινοβολίας και να επιτύχουμε υψηλότερη θερμοκρασία στον εξατμιστή του CPL χρησιμοποιήθηκε παραβολικό κάτοπτρο σε συνδυασμό με συγκεντρωτικό συλλέκτη. Η πειραματική εγκατάσταση που σχεδιάσθηκε και κατασκευάστηκε είχε ως στόχο τη μελέτη της συμπεριφοράς του CPL σε θερμικά φορτία υπό μεταβλητές συνθήκες πλήρωσης της εγκατάστασης, ενώ εξετάστηκε και η συμπεριφορά της τριχοειδούς αντλίας όταν ο εξατμιστής βρίσκονταν υπό κλίση ως προς το επίπεδο, και έγινε σύγκριση των πειραματικών αποτελεσμάτων που προέκυψαν με τα αντίστοιχα για λειτουργία σε οριζόντιο επίπεδο. Η παραμετροποίηση της πειραματικής διερεύνησης του CPL αφορούσε τέσσερις τιμές θερμοκρασίας εισόδου του ρευστού, 15, 25, 35 και 45 οC, τρεις τιμές πίεσης πλήρωσης του κυκλώματος, 0,05, 0,15 και 0,25 bar, και, τέλος, τρεις γωνίες κλίσης, 8ο, 16ο και 23ο. Η διάρκεια των πειραμάτων ήταν αρχικά δέκα ώρες, ώστε να προσομοιώνει τη λειτουργία της εγκατάστασης σε διάστημα ηλιοφάνειας κατά τη διάρκεια της καλοκαιρινής περιόδου, αλλά και εικοσιτέσσερις, ώστε να αποτυπωθεί η απρόσκοπτη διατήρηση της κατάστασης σταθερής λειτουργίας του κυκλώματος. Στο δεύτερο μέρος της διατριβής παρουσιάζονται τα υπολογιστικά μοντέλα δύο και τριών διαστάσεων, 2Δ και 3Δ, όπως σχεδιάστηκαν στο λογισμικό GAMBIT της Fluent Inc., βάση των διαστάσεων του εξατμιστή της πειραματικής εγκατάστασης. Τα αποτελέσματα της διερεύνησης που πραγματοποιήθηκε αφορούσαν το νερό, την ακετόνη, την αμμωνία σαν ρευστά λειτουργίας, τόσο στο επίπεδο όσο και υπό γωνίες κλίσης, παραμετροποιώντας τόσο το θερμαινόμενο μήκος πορώδους επί του συνολικού μήκους του πορώδους του εξατμιστή, όσο και τη θερμοκρασία κορεσμού. Τα δεδομένα για όλα τα ρευστά συγκεντρώθηκαν σε συγκριτικά διαγράμματα, ώστε να εξαχθούν συμπεράσματα για τα περιθώρια αξιοποίησης αυτών, είτε υπάρχει κλίση είτε όχι. Επιπλέον, τεκμηριώθηκε η επιλογή του νερού σαν καταλληλότερο ρευστό λειτουργίας κάτω από δεδομένες συνθήκες. Στο τρίτο μέρος παρουσιάζεται ο αριθμητικός κώδικας που δημιουργήθηκε για τη μοντελοποίηση ολόκληρης της εγκατάστασης του CPL και παραθέτουμε συγκριτικά διαγράμματα, για τις ίδιες συνθήκες λειτουργίας, με τα πειραματικά, τα αριθμητικά και τα υπολογιστικά αποτελέσματα. Στο τελευταίο μέρος έχουμε σχεδιάσει κυκλώματα, αξιοποιώντας την τριχοειδή αντλία, για τη ψύξη/θέρμανση των χώρων μιας κατοικίας για ολόκληρο το έτος. Μια πρόταση που βασίζεται στην αξιοποίηση της ηλιακής ενέργειας και ανταποκρίνεται στην επιτακτική ανάγκη για εκμετάλλευση των ανανεώσιμων πηγών ενέργειας και τη μείωση της χρήσης ηλεκτρικής ενέργειας, εξοικονομώντας χρήματα και προστατεύοντας το περιβάλλον / Present research was conducted in Fluid Mechanics Laboratory of the Mechanical Engineering and Aeronautics Department, University of Patras, and was financed by the operational programme «Herakleitos II», Education and Lifelong Learning Investing in knowledge society. Modern demands in controlling heating load of the cooling systems of mechanical or electrical components are increasing. Cooling systems are divided in active and passive systems. In active systems energy is transported due to sensual heat. While in passive systems due to working fluid latent heat of evaporation because of capillary forces developed in the porous wick inside the evaporator. Passive systems are preferred compared to active systems because they can transfer larger amount of heat, are more reliable, since there are no moving parts, and, finally, lifetime period is longer. The Capillary Pumped Loop (CPL) is a device proper for thermal management control, and was investigated in the present PhD study. The CPL operating principle is based on capillary action, developed in the liquid-vapor phase interface of the working liquid in the porous wick inside the evaporator, and working fluid evaporation and condensation latent heat. The result is that the working fluid is displaced inside the loop without any mechanical pump and heat load is transported in large distances. CPL main components are an evaporator, a condenser, a liquid line, a vapor line and a reservoir. Research regarding the CPL experimental models so far concentrated in the evaporator start-up and steady working state conditions. For all those cases heat load was applied through electric resistances. In the present study heat load was alternatively applied through solar radiation using a solar simulator, designed for this purpose. In order to achieve higher temperature in the evaporator external wall and increase solar radiation exploited, a parabolic mirror was used in combination with a solar collector. The experimental installation was designed in such a way to study the behavior of a CPL when heat load was imposed under different loop charging pressures and for several evaporator inclination angles. Experimental results where compared to the results acquired for evaporator operating at zero inclination angle. The initial values of the working fluid temperature were 15, 25, 35 and 45 oC, of the charging pressure 0,05, 0,15, 0,25 bar and of the inclination angle 8, 16 and 23o. The duration of the experiments was initially ten hours, in order to simulate CPL operating during a typical summer day, and then increased to twenty four hours to investigate continuous operation during all day. In the second section of this study two and three dimensions, 2D and 3D, computational models are presented designed in Gambit, Fluent Inc., based on the exact dimensions of the experimental ones. Computational results were derived for water, acetone and ammonia, as working fluid, for zero inclination and the three values of angles mentioned above. Models were customized for different porous wick heated length and working liquid of different saturation temperature. Comparative figures for all working fluids are presented whether evaporator was under inclination angle or not. Moreover, those comparative figures reviled that water was more suitable as working fluid under steady operating state. In the third section the numerical model simulating the overall CPL function is presented and comparative figures between experimental, computational and numerical results are given, for the same operating conditions. In the last section a potential solar CPL heating/cooling system for domestic use is presented. This potential system could meet the demands for using renewable energy sources in order to reduce electrical energy consumption, save money and protect the environment at the same time.

Thèse (M.Sc.T.) -- Université du Québec à Chicoutimi, 2006. / La p. de t. porte en outre: Mémoire présenté à l'Université du Québec à Chicoutimi comme exigence partielle de la maîtrise en science[s] de la terre. CaQCU Bibliogr.: f. 120-125. Document électronique également accessible en format PDF. CaQCU

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Mathematical modeling and simulations of a submerged renewable storage system integrated to a wind farm, chosen based on the geographical and wind conditions at the Baltic Sea, gives insight on the feasibility of the submerged renewable storage and an approximation of the payback period and profits that could be generated. Genetic Algorithms were used to obtain the optimal number of spheres for a certain depth, based on 2 objective functions I.e. Minimum Life Cycle Cost (LCC) and maximum reduction in wind curtailment. The new arrangement concept shows that the Initial Capital Cost (ICC) could be decreased by 25% to 60% depending upon the number of sphere employed. Based on the inputs considered in the study, the results prove that the submerged renewable storage system would be feasible, and the profits ranging from 15 Million Euro to 29 Million Euro can be achieved at the chosen location, towards the Swedish side of the Baltic sea. Although, in a real life scenario it is assumed that only up to half of the profits obtained in the results would be achievable. The results also show that, the Pump/Turbine with a high turbine efficiency and lower pump efficiency, generated better profits, compared to a Pump/Turbine running with a higher pump efficiency and lower turbine efficiency. An attempt to increase the round-trip efficiency by adding a multi stage submersible pump, resulted in additional ICC and LCC, which saw a decrease in profits.

O interesse mundial e os investimentos em fontes renováveis de energia têm aumentado consideravelmente nos últimos anos. Estas tecnologias têm a vantagem de aproveitar os recursos disponíveis localmente, reduzindo a dependência de fontes externas. Entretanto, um dos principais problemas associados a muitas das tecnologias de energias renováveis é sua imprevisibilidade ou intermitência. O armazenamento de energia é a técnica mais utilizada para moderar estas intermitências. Para aproveitamento em grande escala, os reservatórios hidrelétricos (de usinas hidrelétricas convencionais com reservatório e usinas hidrelétricas reversíveis) representam a tecnologia mais madura e amplamente aproveitada para armazenamento de energia elétrica na forma de energia potencial no volume de água. Isto faz destes uma opção importante a ser incluída no projeto de um sistema autônomo híbrido de geração de energia. Segundo diferentes autores consultados, o software HOMER (Hybrid Optimization Model for Electric Renewables) é a ferramenta mais amplamente utilizada em pesquisas relacionadas à simulação e configuração ótima deste tipo de sistemas. Esta tese apresenta um conjunto de procedimentos para determinar, em nível de pré-viabilidade, a configuração ótima (em termos do custo presente líquido) e o conjunto de arranjos viáveis de um sistema autônomo de geração de energia incluindo fontes renováveis intermitentes e reservatórios hidrelétricos. O software HOMER é aplicado na simulação e avaliação dos sistemas híbridos dos estudos de caso hipotéticos do presente trabalho, utilizados para validar os métodos propostos. Estes exemplos foram criados a partir de dados reais relacionados ao Estado de Rio Grande do Sul. Os procedimentos descritos são aplicáveis a qualquer região do mundo onde exista um local com potencial para reservatórios hidrelétricos, assim como dados de disponibilidade e custos relacionados a fontes renováveis intermitentes. Além de determinar a configuração ótima e o conjunto de arranjos viáveis, os resultados obtidos indicam que os procedimentos descritos podem ajudar na definição da melhor utilização de um local com potencial hidrelétrico. Igualmente, permitem estimar a quantidade de eletricidade excedente que poderia ser recuperada através de usinas reversíveis. Os resultados mostram que configuração ótima depende de muitos fatores, tais como restrições hidrológicas, a carga a ser atendida e o custo de geração de cada fonte. / Global interest and investments in renewable energy sources has increased considerably in recent years. These technologies have the advantage of using locally available resources, reducing dependence on external energy sources. However, most renewable energy technologies suffer from an intermittent characteristic due to the diurnal and seasonal patterns of the natural resources needed for power generation. Energy Storage is the most used technique to buffer this intermittency. For large-scale applications, hydropower reservoirs (of conventional and pumped storage plants) are the most mature and the most widely employed technology for electricity storage in the form of potential energy. For this reason, a hydropower reservoir is a suitable option to consider including in an autonomous hybrid power system. According to many authors, the HOMER model (Hybrid Optimization Model for Electric Renewables) is the most widely used tool in research studies related to simulation and optimal design of this type of systems. This thesis presents some procedures to define, as a pre-feasibility assessment, the optimal configuration (in terms of Net Present Cost) and set of feasible designs of an autonomous hybrid power system that includes intermittent renewable energy sources and hydropower reservoirs. The HOMER software is used for simulating and evaluating the hybrid power systems of the hypothetical case studies, used to validate the proposed methods. These examples were created based on real data related to the State of Rio Grande do Sul, Brazil. The procedures described can be adapted to any other region of the world where exists a site suitable for the construction of hydropower reservoirs, along with available data regarding intermittent renewable sources and generation costs. Besides defining the optimal configuration and the set of feasible designs, the results indicate that the procedures explained could help in the definition of the best use of a site with hydropower potential. Likewise, these methods can also be used to estimate how much excess electricity can be recovered by means of pumped storage hydropower. The results show that the optimal system design depends on many factors such as hydrological constraints, average load to serve and energy cost of each source.

[pt] Configurações novas e tradicionais de sistemas de refrigeração comerciais foram comparadas considerando sua operação com fluidos refrigerantes alternativos. Primeiramente, desenvolveram-se modelos termodinâmicos para o ciclo transcrítico de dois estágios com refrigerante CO2 (CO2 booster) e para o sistema indireto com CO2 bifásico operando como fluido secundário (pumped CO2). Tais tecnologias foram, em seguida, comparadas com o ciclo de expansão direta (DX) por meio do COP e do consumo anual de energia. Nessa análise, R404A, CO2, e misturas não-azeotrópicas de baixo GWP foram utilizados como fluidos refrigerantes. Em segundo lugar, desenvolveu-se modelo de parâmetros concentrados para simular a operação em regime permanente do sistema de expansão direta com múltiplos compressores e evaporadores. O método multizona foi utilizado na modelagem dos trocadores de calor tubo-e-aleta, com a consideração de diferentes tipos de aletas e superfícies internas para os tubos. Resultados da simulação foram comparados com dados experimentais e, em seguida, calculou-se o impacto ambiental do sistema operando com diferentes refrigerantes de baixo GWP, por meio da metodologia LCCP. / [en] Comparison of new and conventional commercial refrigeration systems, operating with typical and alternative refrigerants, was performed. First, thermodynamic models for the pumped CO2 and the CO2 booster cycles were developed. The COP and the annual energy consumption of these novel designs were compared to those of the traditional direct expansion system in different geographic locations, to take into account year-round climate data. Refrigerant R404A, CO2 and new low-GWP non-azeotropic blends were considered as working uids in this analysis. Second, a component-based lumped parameter model to simulate the steady-state operation of a multicompressor multi-evaporator direct expansion system was developed. The modeling effort considered a multizone approach for the tube-and-fin heat exchangers, as well as addressing enhanced internal surfaces and different fin patterns. Predicted results were compared with experimental data, and a life cycle climate performance (LCCP) analysis was performed to compare the environmental impact of new low-GWP refrigerants.

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O interesse mundial e os investimentos em fontes renováveis de energia têm aumentado consideravelmente nos últimos anos. Estas tecnologias têm a vantagem de aproveitar os recursos disponíveis localmente, reduzindo a dependência de fontes externas. Entretanto, um dos principais problemas associados a muitas das tecnologias de energias renováveis é sua imprevisibilidade ou intermitência. O armazenamento de energia é a técnica mais utilizada para moderar estas intermitências. Para aproveitamento em grande escala, os reservatórios hidrelétricos (de usinas hidrelétricas convencionais com reservatório e usinas hidrelétricas reversíveis) representam a tecnologia mais madura e amplamente aproveitada para armazenamento de energia elétrica na forma de energia potencial no volume de água. Isto faz destes uma opção importante a ser incluída no projeto de um sistema autônomo híbrido de geração de energia. Segundo diferentes autores consultados, o software HOMER (Hybrid Optimization Model for Electric Renewables) é a ferramenta mais amplamente utilizada em pesquisas relacionadas à simulação e configuração ótima deste tipo de sistemas. Esta tese apresenta um conjunto de procedimentos para determinar, em nível de pré-viabilidade, a configuração ótima (em termos do custo presente líquido) e o conjunto de arranjos viáveis de um sistema autônomo de geração de energia incluindo fontes renováveis intermitentes e reservatórios hidrelétricos. O software HOMER é aplicado na simulação e avaliação dos sistemas híbridos dos estudos de caso hipotéticos do presente trabalho, utilizados para validar os métodos propostos. Estes exemplos foram criados a partir de dados reais relacionados ao Estado de Rio Grande do Sul. Os procedimentos descritos são aplicáveis a qualquer região do mundo onde exista um local com potencial para reservatórios hidrelétricos, assim como dados de disponibilidade e custos relacionados a fontes renováveis intermitentes. Além de determinar a configuração ótima e o conjunto de arranjos viáveis, os resultados obtidos indicam que os procedimentos descritos podem ajudar na definição da melhor utilização de um local com potencial hidrelétrico. Igualmente, permitem estimar a quantidade de eletricidade excedente que poderia ser recuperada através de usinas reversíveis. Os resultados mostram que configuração ótima depende de muitos fatores, tais como restrições hidrológicas, a carga a ser atendida e o custo de geração de cada fonte. / Global interest and investments in renewable energy sources has increased considerably in recent years. These technologies have the advantage of using locally available resources, reducing dependence on external energy sources. However, most renewable energy technologies suffer from an intermittent characteristic due to the diurnal and seasonal patterns of the natural resources needed for power generation. Energy Storage is the most used technique to buffer this intermittency. For large-scale applications, hydropower reservoirs (of conventional and pumped storage plants) are the most mature and the most widely employed technology for electricity storage in the form of potential energy. For this reason, a hydropower reservoir is a suitable option to consider including in an autonomous hybrid power system. According to many authors, the HOMER model (Hybrid Optimization Model for Electric Renewables) is the most widely used tool in research studies related to simulation and optimal design of this type of systems. This thesis presents some procedures to define, as a pre-feasibility assessment, the optimal configuration (in terms of Net Present Cost) and set of feasible designs of an autonomous hybrid power system that includes intermittent renewable energy sources and hydropower reservoirs. The HOMER software is used for simulating and evaluating the hybrid power systems of the hypothetical case studies, used to validate the proposed methods. These examples were created based on real data related to the State of Rio Grande do Sul, Brazil. The procedures described can be adapted to any other region of the world where exists a site suitable for the construction of hydropower reservoirs, along with available data regarding intermittent renewable sources and generation costs. Besides defining the optimal configuration and the set of feasible designs, the results indicate that the procedures explained could help in the definition of the best use of a site with hydropower potential. Likewise, these methods can also be used to estimate how much excess electricity can be recovered by means of pumped storage hydropower. The results show that the optimal system design depends on many factors such as hydrological constraints, average load to serve and energy cost of each source.

O interesse mundial e os investimentos em fontes renováveis de energia têm aumentado consideravelmente nos últimos anos. Estas tecnologias têm a vantagem de aproveitar os recursos disponíveis localmente, reduzindo a dependência de fontes externas. Entretanto, um dos principais problemas associados a muitas das tecnologias de energias renováveis é sua imprevisibilidade ou intermitência. O armazenamento de energia é a técnica mais utilizada para moderar estas intermitências. Para aproveitamento em grande escala, os reservatórios hidrelétricos (de usinas hidrelétricas convencionais com reservatório e usinas hidrelétricas reversíveis) representam a tecnologia mais madura e amplamente aproveitada para armazenamento de energia elétrica na forma de energia potencial no volume de água. Isto faz destes uma opção importante a ser incluída no projeto de um sistema autônomo híbrido de geração de energia. Segundo diferentes autores consultados, o software HOMER (Hybrid Optimization Model for Electric Renewables) é a ferramenta mais amplamente utilizada em pesquisas relacionadas à simulação e configuração ótima deste tipo de sistemas. Esta tese apresenta um conjunto de procedimentos para determinar, em nível de pré-viabilidade, a configuração ótima (em termos do custo presente líquido) e o conjunto de arranjos viáveis de um sistema autônomo de geração de energia incluindo fontes renováveis intermitentes e reservatórios hidrelétricos. O software HOMER é aplicado na simulação e avaliação dos sistemas híbridos dos estudos de caso hipotéticos do presente trabalho, utilizados para validar os métodos propostos. Estes exemplos foram criados a partir de dados reais relacionados ao Estado de Rio Grande do Sul. Os procedimentos descritos são aplicáveis a qualquer região do mundo onde exista um local com potencial para reservatórios hidrelétricos, assim como dados de disponibilidade e custos relacionados a fontes renováveis intermitentes. Além de determinar a configuração ótima e o conjunto de arranjos viáveis, os resultados obtidos indicam que os procedimentos descritos podem ajudar na definição da melhor utilização de um local com potencial hidrelétrico. Igualmente, permitem estimar a quantidade de eletricidade excedente que poderia ser recuperada através de usinas reversíveis. Os resultados mostram que configuração ótima depende de muitos fatores, tais como restrições hidrológicas, a carga a ser atendida e o custo de geração de cada fonte. / Global interest and investments in renewable energy sources has increased considerably in recent years. These technologies have the advantage of using locally available resources, reducing dependence on external energy sources. However, most renewable energy technologies suffer from an intermittent characteristic due to the diurnal and seasonal patterns of the natural resources needed for power generation. Energy Storage is the most used technique to buffer this intermittency. For large-scale applications, hydropower reservoirs (of conventional and pumped storage plants) are the most mature and the most widely employed technology for electricity storage in the form of potential energy. For this reason, a hydropower reservoir is a suitable option to consider including in an autonomous hybrid power system. According to many authors, the HOMER model (Hybrid Optimization Model for Electric Renewables) is the most widely used tool in research studies related to simulation and optimal design of this type of systems. This thesis presents some procedures to define, as a pre-feasibility assessment, the optimal configuration (in terms of Net Present Cost) and set of feasible designs of an autonomous hybrid power system that includes intermittent renewable energy sources and hydropower reservoirs. The HOMER software is used for simulating and evaluating the hybrid power systems of the hypothetical case studies, used to validate the proposed methods. These examples were created based on real data related to the State of Rio Grande do Sul, Brazil. The procedures described can be adapted to any other region of the world where exists a site suitable for the construction of hydropower reservoirs, along with available data regarding intermittent renewable sources and generation costs. Besides defining the optimal configuration and the set of feasible designs, the results indicate that the procedures explained could help in the definition of the best use of a site with hydropower potential. Likewise, these methods can also be used to estimate how much excess electricity can be recovered by means of pumped storage hydropower. The results show that the optimal system design depends on many factors such as hydrological constraints, average load to serve and energy cost of each source.