O estudo do comportamento termodinâmico de polímeros, através da relação pressão-volume-temperatura (PvT), é essencial para analisar os processos físicos que ocorrem durante o seu processamento e para prever as propriedades finais dos produtos. Existem diversos estudos que comparam a precisão de várias equações de estado (EdE) na descrição do comportamento termodinâmico de polímeros. Segundo a literatura, as que usualmente apresentam os melhores resultados são as equações teóricas dos modelos de célula e de vazios, e as equações empíricas Tait e Hartmann- Haque (HH). Entretanto, não há trabalhos que avaliem a qualidade da estimação dos parâmetros e a sensibilidade da predição das propriedades termodinâmicas com relação aos parâmetros das equações. Além disso, há poucos estudos que contemplem a predição dos coeficientes de expansão térmica e de compressão. Com base nessas observações, o objetivo deste estudo foi apresentar uma análise mais detalhada das equações de estado Tait, HH, MCM (modelo de célula modificado) e SHT (teoria de vazios simplificada) na predição do comportamento PvT de polímeros, para os estados físicos fundido e sólido. As EdE foram analisadas com relação à: (i) qualidade na estimação dos parâmetros, (ii) sensibilidade das suas predições para cada um dos seus parâmetros, (iii) qualidade na predição do volume específico, e (iv) qualidade na predição do coeficiente de expansão térmica isobárica e da compressibilidade isotérmica. Os resultados apontaram que todas as equações de estado proporcionaram uma descrição satisfatória do comportamento PvT no estado fundido, com uma leve superioridade da EdE Tait. As EdE apresentaram baixos desvios padrão na estimação dos parâmetros, sensibilidade paramétrica adequada e predições plausíveis do volume específico, do coeficiente de expansão térmica e da compressibilidade isotérmica, com exceção da EdE Tait que apresentou uma predição do coeficiente de expansão térmica que não está de acordo com o esperado teoricamente. No estado sólido, a equação de estado Tait exibiu desempenho semelhante ao apresentado para o estado fundido na predição de dados PvT. A EdE HH apresentou resultados satisfatórios para os polímeros amorfos e dificuldade no ajuste da curva PvT de polímeros semicristalinos. / The study of the pressure-volume-temperature (PvT) behavior of polymers is essential to the analysis of the physical processes that occur during processing, and to predict the properties of the final products. In literature, there are several studies that compare the accuracy of various equations of state (EoS) in describing the PvT behavior of polymers, indicating that the best results are usually obtained with the theoretical equations of cell and hole models, and the Tait and Hartmann-Haque (HH) empirical equations. However, most of these studies do not provide information about the quality of the estimated parameters or the sensitivity of the prediction of thermodynamic properties to the parameters of the equations. Furthermore, there are few studies exploring the prediction of thermal expansion and compression coefficients. Based on these observations, the objective of this study is to deepen the analysis of Tait, HH, MCM (modified cell model) and SHT (simplified hole theory) equations of state in prediction the PvT behavior of polymers, for molten and solid states. In this sense, the EoS were analyzed with respect to: (i) quality in the estimation of its parameters, (ii) sensitivity of their predictions to each of its parameters, (iii) quality of the prediction of the specific volume, and (iv) quality in the prediction of isobaric thermal expansion coefficient and isothermal compressibility. The results showed that all equations of state provided an adequated description of the PvT behavior in the molten state, with light superiority of the Tait EoS. All equations presented low standard deviations in the estimation of parameters, adequate sensitivity of its parameters and plausible prediction of specific volume, thermal expansion, and isothermal compression coefficients, except Tait EoS that show a prediction of the dependence of the thermal expansion coefficient with the temperature that is not in agreement with the theoretical expectations. In the solid state, the Tait equation exhibited performance similar to the one obtained for the molten state. HH EoS showed a satisfactory result for amorphous polymers and a difficulty in fitting the PvT curve of semicrystalline polymers.

No description available.

La réduction des dimensions des transistors a augmenté la sensibilité des circuits numériques aux variations PVT et, plus récemment, aux effets de vieillissement, notamment BTI et HCI. De larges marges de sécurité sont donc nécessaires pour assurer un fonctionnement correct du circuit, ce qui entraîne une perte d'énergie importante. Les solutions actuelles pour améliorer l'efficacité énergétique sont principalement basées sur des solutions de type «Adaptive Voltage and Frequency Scaling (AVFS)». Cependant, ce type de solution ne peut anticiper les variations avant qu'elles ne se produisent. Cette approche doit donc être amélioré pour traiter les problèmes de fiabilité liés au vieillissement. Cette thèse propose une nouvelle méthodologie pour générer des modèles simplifiés pour estimer la fréquence maximale du circuit Fmax. Un premier modèle est créé pour estimer le délai de propagation du (des) chemin(s) critique(s) en fonction des variations PVT. Les effets BTI et HCI sont ensuite modélisés via une modification des paramètres du premier modèle. Construit à partir des modèles au niveau transistor, le modèle de vieillissement obtenu prend en compte tous les facteurs qui influent sur le vieillissement, à savoir, la topologie des circuits, l'application, la tension et la température. La méthodologie proposée est validée sur deux architectures en technologie 28nm FD-SOI. Les modèles peuvent être alimentés par des moniteurs de température et de tension, ce qui permet une évaluation précise de l'évolution de Fmax. Toutefois, ces moniteurs sont sensibles au vieillissement. Aussi, une méthode de recalibrage pour compenser les effets du vieillissement a été développée pour un moniteur numérique de température et de tension. Des exemples d'applications en ligne sont donnés. Les modèles sont également utilisés pour simuler des circuits complexes sous des variations de vieillissement, par exemple un circuit multi-cœur et un système AVFS. Cela permet d'évaluer différentes stratégies concernant la performance, l'énergie et la fiabilité. / The continuous scaling of transistor dimensions has increased the sensitivity of digital circuits to PVT variations and, more recently, to aging effects such as BTI and HCI. Large voltage guard bands, corresponding to worst-case operation, are thus necessary and leads to a considerable energy loss. Current solutions to increase energy efficiency are mainly based on Adaptive Voltage and Frequency Scaling (AVFS). However, as a reactive solution, it cannot anticipate the variation before it occurs. It has, thus, to be improved for handling long-term reliability issues. This thesis proposes a new methodology to generate simplified but nevertheless accurate models to estimate the circuit maximum operating frequency Fmax. A first model is created for the modelling of the propagation delay of the critical path(s) as a function of PVT variations. Both BTI/HCI effects are then modelled as a shift in the parameters of the first model. Built on the top of device-level models, it takes into account all factors that impact global aging, namely, circuit topology, workload, voltage and temperature variations. The proposed modelling approach is evaluated on two architectures implemented in 28nm FD-SOI technology. The models can be fed by temperature and voltage monitors. This allows an accurate assessment of the circuit Fmax evolution during its operation. However, these monitors are prone to aging. Therefore, an aging-aware recalibration method has been developed for a particular V T monitor. Examples of on-line applications are given. Finally, the models are used to simulate complex circuits under aging variations such a multi-core circuit and an AVFS system. This allows the evaluation of different strategies regarding performance, energy and reliability.

O objetivo deste trabalho é modelar a arquitetura de uma usina solar fotovoltaica arrefecida intitulada UFVa, utilizando um protótipo de verificação. A metodologia se baseia na medição, verificação e análise dos dados de temperatura e produção de energia elétrica dos strings de teste (arrefecido) e comparação (não arrefecido), estudo do comportamento da alimentação de água do sistema de arrefecimento e o impacto das condições climáticas na operação do protótipo de UFVa. Por meio das análises dos dados constatou-se que, para o período entre as 09h00min e as 17h30min, os módulos PV do string de teste sempre operam com temperaturas inferiores aos módulos PV do string de comparação. Durante o período de testes, no qual a temperatura dos módulos PV do string de comparação operou acima de 55,0°C, as temperaturas médias e máximas registradas nos módulos PV do string de teste foram inferiores a 37,0 °C, operando sempre abaixo da temperatura nominal de operação da célula (NOCT). A produção de energia elétrica no string de teste superou a do string de comparação em 3,0kWh/dia. Portanto, o sistema de arrefecimento reduz a temperatura de operação dos módulos PV, principalmente no período de máxima geração elétrica, que corresponde ao período das 11h00min às 15h00min, proporcionando ganhos médios de rendimento de 5,9% na produção de energia, 10,3% na potência e 5,4% no FC. / In this work we use a verification prototype to model the architecture of a solar photovoltaic power plant equipped with a cooling system. The power plant we model is called UFVa. The methodology is based on the measurement, verification, and data analysis of temperature, electricity generation, test strings (cooled) and comparison strings (not cooled), along with a study of the water feeding behavior of the cooling system, and the impact of climatic conditions in the UFVa prototype operation. By analyzing the data we observed that, for the period between 09:00am and 5:30pm, the PV modules of the test string operate at temperatures below those of the PV modules of the comparison string. During the tests, in which the temperature of the PV modules of the comparison string operated above 55.0°C, the average and the maximum temperatures recorded in the PV modules of the testing string lied below 37.0°C, operating below the NOCT. Regarding the generation of electricity, the test string generated 3.0 kWh/day more than the comparison string. Hence, the cooling system decreases the operating temperature of the PV modules, particularly during the maximum power generation period which is from 11am to 3pm. This leads to efficiency average gains of up to 5.9% in the generation of electricity, 10.3% in the power, and 5.3% in the PR and PF.

O objetivo deste trabalho é modelar a arquitetura de uma usina solar fotovoltaica arrefecida intitulada UFVa, utilizando um protótipo de verificação. A metodologia se baseia na medição, verificação e análise dos dados de temperatura e produção de energia elétrica dos strings de teste (arrefecido) e comparação (não arrefecido), estudo do comportamento da alimentação de água do sistema de arrefecimento e o impacto das condições climáticas na operação do protótipo de UFVa. Por meio das análises dos dados constatou-se que, para o período entre as 09h00min e as 17h30min, os módulos PV do string de teste sempre operam com temperaturas inferiores aos módulos PV do string de comparação. Durante o período de testes, no qual a temperatura dos módulos PV do string de comparação operou acima de 55,0°C, as temperaturas médias e máximas registradas nos módulos PV do string de teste foram inferiores a 37,0 °C, operando sempre abaixo da temperatura nominal de operação da célula (NOCT). A produção de energia elétrica no string de teste superou a do string de comparação em 3,0kWh/dia. Portanto, o sistema de arrefecimento reduz a temperatura de operação dos módulos PV, principalmente no período de máxima geração elétrica, que corresponde ao período das 11h00min às 15h00min, proporcionando ganhos médios de rendimento de 5,9% na produção de energia, 10,3% na potência e 5,4% no FC. / In this work we use a verification prototype to model the architecture of a solar photovoltaic power plant equipped with a cooling system. The power plant we model is called UFVa. The methodology is based on the measurement, verification, and data analysis of temperature, electricity generation, test strings (cooled) and comparison strings (not cooled), along with a study of the water feeding behavior of the cooling system, and the impact of climatic conditions in the UFVa prototype operation. By analyzing the data we observed that, for the period between 09:00am and 5:30pm, the PV modules of the test string operate at temperatures below those of the PV modules of the comparison string. During the tests, in which the temperature of the PV modules of the comparison string operated above 55.0°C, the average and the maximum temperatures recorded in the PV modules of the testing string lied below 37.0°C, operating below the NOCT. Regarding the generation of electricity, the test string generated 3.0 kWh/day more than the comparison string. Hence, the cooling system decreases the operating temperature of the PV modules, particularly during the maximum power generation period which is from 11am to 3pm. This leads to efficiency average gains of up to 5.9% in the generation of electricity, 10.3% in the power, and 5.3% in the PR and PF.

Im Rahmen der Arbeit wurde eine neuartige Variante der Hochtemperatur-Gasphasenepitaxie (HTVPE) für die Herstellung von GaN entwickelt, die eine hohe Flexibilität und bessere Kontrolle des Züchtungsprozesses ermöglicht. Für die Realisierung des Konzeptes wurde eine Züchtungsanlage für die HTVPE entworfen und aufgebaut. Des Weiteren wurde ein numerisches Modell des Wärme- und Stofftransports entwickelt und für die Untersuchungen der Transportphänomene im HTVPE-Reaktor sowie für die Weiterentwicklung des Züchtungsreaktors verwendet. Die systematischen Züchtungsexperimente zeigten eine gute Übereinstimmung mit den Simulationsergebnissen und lieferten ein besseres Verständnis der HTVPE und ihres Anwendungspotentials. Die versbesserte Prozesskontrolle ermöglichte die erstmalige Anwendung der Niedertemperatur-Nukleation für die heteroepitaktische Abscheidung von GaN auf Saphir mit der HTVPE. Weiterhin wurden Wachstumsraten über 80 µm/h erreicht und das Potential der HTVPE für die Herstellung von GaN-Volumenschichten demonstriert.

Orientador: Elaine Maria Cardoso / Resumo: O presente trabalho consistiu na análise teórica e experimental de um sistema híbrido PVT - fotovoltaico/térmico. Este consiste de um painel fotovoltaico (PV), com sistema de rastreamento, para aproveitar a radiação solar direta e difusa, e de um sistema d e resfriamento por convecção forçada acoplado, permitindo gerar eletricidade e calor em um único processo além de reduzir a temperatura de operação de um painel solar fotovoltaico comercial e, assim, melhorar sua eficiência energética. O módulo PV está instalado na região noroeste do estado de São Paulo. O conjunto experimental possui um sistema de rastreamento solar azimutal de eixo simples; a tensão e a corrente de saída do painel foram medidas para quantificar a potência produzida levando em consideração diferentes condições de operação. Todos os testes foram realizados in loco usando um painel fotovoltaico comercial, sempre levando em consideração as condições meteorológicas do dia. O rastreamento solar aumenta em 45,5% a energia gerada para um dia do mês de junho em relação a um sistema fixo. O painel fotovoltaico com a parte posterior isolada termicamente opera em condições 15 °C a 20 °C mais quente que um painel não isolado, o que implica em perdas energéticas da ordem de 7,6%. O trocador de calor tipo serpentina, com uso de água deionizada, não mostrou desempenho satisfatório ao resfriar o módulo fotovoltaico devido à significativa resistência térmica de contato com a face posterior do módulo. A análise teórica apre... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The present work consisted of a theoretical and experimental analysis of a hybrid PVT – photovoltaic/thermal system. This system consisted of a photovoltaic (PV) panel with a solar tracking system to take advantage of direct and diffuse solar radiation and a forced convection cooling system. This allows the generation of electricity and useful heat in a single process in addition to reducing the operating temperature of a commercial photovoltaic solar panel and thus improves its energy efficiency. The PV module is installed in the northwest region of the state of São Paulo. The experimental apparatus had a single axis, azimuth solar tracking system; the output voltage and current of the panel were measured to quantify the power produced taking into account different operating conditions. All tests were carried out in loco using a commercial photovoltaic panel, always taking into account the weather conditions of the day. Solar tracking increases the energy generated by one day of the month by 45.5% compared to a fixed system. The temperature of the module with a thermally insulated back sheet was 15° C to 20° C hotter than a non-insulated panel, which implies energy losses of the order of 7.6%. The serpentine type heat exchanger, using deionized water, did not show satisfactory performance when cooling the photovoltaic module due to the significant thermal resistance of contact with the rear face of the module. Theoretical analysis showed errors of less than 10% compared to t... (Complete abstract click electronic access below) / Mestre

Im Rahmen der Arbeit wurde eine neuartige Variante der Hochtemperatur-Gasphasenepitaxie (HTVPE) für die Herstellung von GaN entwickelt, die eine hohe Flexibilität und bessere Kontrolle des Züchtungsprozesses ermöglicht. Für die Realisierung des Konzeptes wurde eine Züchtungsanlage für die HTVPE entworfen und aufgebaut. Des Weiteren wurde ein numerisches Modell des Wärme- und Stofftransports entwickelt und für die Untersuchungen der Transportphänomene im HTVPE-Reaktor sowie für die Weiterentwicklung des Züchtungsreaktors verwendet. Die systematischen Züchtungsexperimente zeigten eine gute Übereinstimmung mit den Simulationsergebnissen und lieferten ein besseres Verständnis der HTVPE und ihres Anwendungspotentials. Die versbesserte Prozesskontrolle ermöglichte die erstmalige Anwendung der Niedertemperatur-Nukleation für die heteroepitaktische Abscheidung von GaN auf Saphir mit der HTVPE. Weiterhin wurden Wachstumsraten über 80 µm/h erreicht und das Potential der HTVPE für die Herstellung von GaN-Volumenschichten demonstriert.

A hybrid photovoltaic/thermal (PVT) collector enables simultaneous electricity and heat production from a single solar module. Integrating PVT collectors with a ground source heat pump (GSHP) improves the seasonal performance of the heating system and prevents from temperature degradation of the ground. However, the integration of PVT and GSHP requires more research, for example, to discover the optimal characteristics of a PVT collector for low operating temperatures and varying weather conditions. Thus, the thermal performance of two commercial unglazed flat-plate PVT collectors was experimentally characterized during low-temperature operation and under dynamic outdoor conditions, including various solar irradiance levels and working fluid flow rates as well as frost formation and condensation on the absorber surface. The thermal performance coefficients were obtained from a simplified version of the ISO 9806:2017 standard steady-state model for solar thermal collectors and used as performance indicators for the tested collectors and for comparison with other PVT collectors found in the literature. During nighttime operation, the PVT collector with a box-channel absorber and the one with a sheet-and-tube absorber have a similar thermal performance, shown as almost the same heat loss coefficients. The effect of flow rate on the heat output of the collectors appears to be negligible when there is no solar irradiance. During humid nights, the heat gains from frost formation and/or condensation on the absorber surface can double the nighttime heat production of the collectors when compared to a dry night with no frost formation or condensation. As the irradiance increases, the box-channel collector starts to outperform the sheet-and-tube collector due to a more effective cooling of the PV module by the box-channel absorber design, which is shown as a higher zero-loss efficiency. The flow rate dependence of the heat output is increased with an increasing irradiance, higher flow rates leading to higher heat outputs. According to the yearly simulations, both tested collectors provide a higher annual heat output under Stockholm weather conditions than the other box-channel and sheet-and-tube collectors available in the Solar Keymark database, when the annual mean fluid temperature is below 7 °C. However, the fin-tube collectors designed for low-temperature heat pump integration outperform the tested collectors on annual basis with mean fluid temperatures below 10 °C. / En solhybrid (PVT) möjliggör samtidig el- och värmeproduktion från en enda solpanel. Att integrera solhybrider med en bergvärmepump förbättrar värmesystemets säsongsprestanda, förhindrar temperatur-nedgång i marken och utgör ett lovande alternativ till luftvärmepumpar. Integrationen av sol-PVT och bergvärmepumpar kräver dock mer forskning, till exempel för att upptäcka de optimala egenskaperna hos en PVT-kollektor, när driftstemperaturerna är låga och väderförhållandena varierar. Därav karakteriserades experimentellt den termiska prestandan hos två kommersiella oglasade PVT-kollektorer under drift vid låg temperatur och under dynamiska utomhusförhållanden, inklusive olika solinstrålningsnivåer och flödes-hastigheter samt frostbildning och kondensation på värmeväxlarens yta. De termiska prestandakoefficienter erhölls från en förenklad version av ISO 9806:2017-standardmodellen för stationärt tillstånd för solfångare och användes som prestandaindikatorer för de testade kollektorerna och för jämförelse med andra PVT-kollektorer som finns i litteraturen. Vid nattdrift har den första PVT-kollektorn med en ”box-channel”-värmeväxlare och den andra kollektorn med en ”sheet-and-tube”-värmeväxlare en liknande termisk prestanda vilket visas av nästan samma värme-förlustkoefficienter. Effekten av massflödet på kollektorernas värmeeffekt verkar vara försumbar, när det finns ingen solinstrålning. Under fuktiga nätter kan värmevinsterna från frostbildning och/eller kondens på värmeväxlarens yta fördubbla kollektorernas värmeproduktion på nattetid jämfört med en torr natt utan frostbildning eller kondens. När instrålningen ökar, börjar ”box-channel”-kollektorn överträffa ”sheet-and-tube”-kollektorn på grund av en mer effektiv kylning av PV-modulen genom den ”box-channel”-värme-växlaren, vilket visas som en högre nollförlusteffektivitet. Värmeeffektens beroende av flödeshastigheten ökar med en ökande solinstrålning: högre flödeshastigheter leder till högre värmeeffekt. Enligt de årliga simuleringarna har de båda testade kollektorerna en högre årlig värmeproduktion under Stockholms väderförhållanden än de andra ”box-channel”- och ”sheet-and-tube”-PVT-kollektorerna, tillgängliga i Solar Keymark -databasen, när den årliga genomsnittliga kylvätsketemperaturen är under 7 °C. Kollektorerna med en ”fin-tube”-värmeväxlare, som är utformade för integration av lågtemperaturvärmepumpar, överträffar dock de testade kollektorerna på årsbasis med genomsnittliga kylvätsketemperaturer under 10 °C.

In order to contribute to reducing the CO2 emissions related to heating in housing buildings, PVT+GSHP systems appear to be interesting solutions and therefore need to be further investigated to optimise their design and increase their deployment on the field. This thesis focused on building PVT model, using the ISO9806:2017, to be integrated in a PVT+GSHP model and determining optimal PVT design parameters for this system. The most determining coefficient being the peak collector efficiency η0 it seems important to maximize it, which would mean a higher quality of solar energy collected by the collector.  The mentioned different coefficients need to be determined using labratory tests detailed in the ISO standard. The choice of the test conditions is important in order to increase the accuracy of the results, mainly when it comes to choosing the mass flow rate which should be clolse to the use conditions. If the PVT module is to be used with another mass flow rate, a correction factor would need to be applied to the coefficients to reflect the behaviour of the PVT in the use conditions.  Finding the optimal PVT array mass flolw rate is important as it enables greater energy saves. In the case presented in the thesis, a mass flow of about 60 l/(h.m²) seems to be the optimal value. A PVT oriented to the South would also guarantee higher saves. / För att bidra till att minska koldioxidutsläppen i samband med uppvärmning av bostadshus verkar PVT+GSHP-system vara intressanta lösningar och behöver därför undersökas ytterligare för att optimera deras utformning och öka deras användning på fältet. Denna avhandling fokuserade på att bygga en PVT-modell, med hjälp av ISO9806:2017, som ska integreras i en PVT+GSHP-modell och bestämma optimala PVT-designparametrar för detta system. Den mest avgörande koefficienten är den maximala solfångareffektiviteten η0 och det verkar viktigt att maximera den, vilket skulle innebära en större mängd solenergi som samlas in av solfångaren.  De olika koefficienterna måste bestämmas med hjälp av laboratorietester som beskrivs i ISO-standarden. Valet av testförhållanden är viktigt för att öka resultatens noggrannhet, främst när det gäller att välja massflödeshastigheten som bör ligga nära användningsförhållandena. Om PVT-modulen ska användas med ett annat massflöde måste en korrigeringsfaktor tillämpas på koefficienterna för att återspegla PVT-modulens beteende under användningsförhållandena.  Det är viktigt att hitta det optimala massflödet för PVT-modulen eftersom det möjliggör större energibesparingar. I det fall som presenteras i avhandlingen verkar ett massflöde på cirka 60 l/(h.m²) vara det optimala värdet. En PVT som är orienterad mot söder skulle också garantera högre besparingar.