Dissertationen zum Thema „Solar sales“

Los fluidos de transferencia de calor, y en particular los nanofluidos, se pueden considerar un elemento esencial en diversos sectores industriales y su rendimiento es clave para una adecuada aplicación en tecnologías que van desde la gestión térmica y la refrigeración, a la generación de energía solar térmica y eléctrica mediante el uso de intercambiadores de calor. Estas industrias necesitan fluidos de transferencia de calor con un rango de temperatura del líquido más amplio y mejores prestaciones en la transferencia de calor que los fluidos convencionales. Todos los fluidos parecen beneficiarse de la dispersión de nanopartículas sólidas, tanto aquellos usados en aplicaciones de baja temperatura y temperatura ambiente, como aquellos que funden a más alta temperatura (p. ej. sales fundidas). La dispersión de nanopartículas conduce a la obtención de nanofluidos que con frecuencia presentan mejores conductividades térmicas y/o calores específicos en comparación con los fluidos base. Sin embargo hay algunas excepciones. En la bibliografía podemos encontrar resultados contradictorios acerca de la mejora de las propiedades térmicas en nanofluidos, lo cual hace que sea necesario un estudio de estos materiales en mayor profundidad. Por otra parte, la naturaleza líquida de estos materiales plantea un verdadero desafío, tanto desde el punto de vista experimental como en relación al marco conceptual. El trabajo que se presenta en esta tesis ha abordado dos retos diferentes relacionados con los fluidos de transferencia de calor y los nanofluidos. En primer lugar, se llevó a cabo un estudio riguroso y sistemático de las propiedades térmicas, morfológicas, reológicas, de estabilidad, acústicas y vibracionales de nanofluidos de grafeno en disolventes orgánicos. Observamos un gran aumento de la conductividad térmica de hasta un 48% y un aumento del 18% en la capacidad calorífica de los nanofluidos de grafeno en N,N-dimetilacetamida (DMAc). También se observó una mejora significativa en los nanofluidos de grafeno en N,N-dimetilformamida (DMF) del orden del 25% y 12% para la conductividad térmica y la capacidad calorífica, respectivamente. El desplazamiento de varias bandas del espectro Raman de DMF y DMAc hacia altas frecuencias (máx. ~ 4 cm-1) al aumentar la concentración de grafeno, sugirió que éste tiene la capacidad de afectar a las moléculas de disolvente a larga distancia, en términos de energía vibracional. En paralelo, las simulaciones numéricas basadas en la teoría funcional de la densidad (DFT) y dinámica molecular (MD) mostraron una orientación paralela de DMF hacia el grafeno, favoreciendo la interacción π-π y contribuyendo a la modificación de los espectros de Raman. Además, se observó un orden local de las moléculas de DMF alrededor del grafeno, lo que sugiere que tanto este tipo especial de interacción como el orden local inducido pueden contribuir a la mejora de las propiedades térmicas del fluido. También se realizaron estudios similares en nanofluidos de grafeno disperso en 1-metil-2-pirrolidona, sin embargo, no se observó ninguna modificación de la conductividad térmica o de los espectros de Raman. Todas estas observaciones juntas sugieren que existe una correlación entre la modificación de los espectros vibracionales y el aumento de la conductividad térmica de los nanofluidos. En vista de los resultados, se discutieron y descartaron algunos de los mecanismos propuestos para explicar la mejora de la conductividad térmica en nanofluidos. La segunda línea de investigación se centró en el desarrollo y caracterización de nuevas formulaciones de sales fundidas con baja temperatura de fusión y alta estabilidad térmica. Con este propósito, se sintetizaron dos nuevas formulaciones de seis componentes basadas en nitratos con una temperatura de fusión de 60-75 °C y una estabilidad térmica de aprox. 500 °C. Por otro lado, la complejidad de las muestras llevó a establecer una serie de métodos experimentales que se proponen para la detección del punto de fusión de estos materiales como una alternativa a la calorimetría convencional, estas técnicas son: espectroscopia Raman, técnica 3ω y transmisión óptica.
Heat transfer fluids and nanofluids constitute an important element in the industry and their performance is key to the successful application in technologies that go from heat management and cooling to heat exchangers in thermal-solar energy and electricity generation. These industries demand heat transfer fluids with a wider liquid temperature range and better thermal performance than the conventional fluids. From low-temperature fluids to high-temperature molten salts, these fluids seem to benefit from the dispersion of solid nanoparticles, leading to nanofluids which frequently feature improved thermal conductivities and/or specific heats as compared with the bare fluids. However, there are some exceptions. Contradictory reports make it necessary to study these materials in greater depth than has been usual. Yet, the liquid nature of these materials poses a real challenge, both from the experimental point of view and from the conceptual framework. The work reported in this thesis has tackled two different challenges related to heat transfer fluids and nanofluids. In the first place, a careful and systematic study of thermal, morphological, rheological, stability, acoustic and vibrational properties of graphene-based nanofluids was carried out. We observed a huge increase of up to 48% in thermal conductivity and 18% in heat capacity of graphene-N,N-dimethylacetamide (DMAc) nanofluids. A significant enhancement was also observed in graphene-N,N-dimethylformamide (DMF) nanofluids of approximately 25% and 12% for thermal conductivity and heat capacity, respectively. The blue shift of several Raman bands (max. ~ 4 cm-1) with increasing graphene concentration in DMF and DMAc nanofluids suggested that graphene has the ability to affect solvent molecules at long-range, in terms of vibrational energy. In parallel, numerical simulations based on density functional theory (DFT) and molecular dynamics (MD) showed a parallel orientation of DMF towards graphene, favoring π–π stacking and contributing to the modification of the Raman spectra. Furthermore, a local order of DMF molecules around graphene was observed suggesting that both this special kind of interaction and the induced local order may contribute to the enhancement of the thermal properties of the fluid. Similar studies were also performed in graphene-N-methyl-2-pyrrolidinone nanofluids, however, no modification of the thermal conductivity or the Raman spectra was observed. All these observations together suggest that there is a correlation between the modification of the vibrational spectra and the increase in the thermal conductivity of the nanofluids. In light of these results, the mechanisms suggested in the literature to explain the enhancement of thermal conductivity in nanofluids were discussed and some of them were discarded. The second line of research focused on the development and characterization of novel molten salts formulations with low-melting temperature and high thermal stability. In this regard, two novel formulations of six components based on nitrates with a melting temperature of 60-75 °C and a thermal stability up to ~ 500 °C were synthesized. Moreover, the complexity of the samples led to establish a series of experimental methods which are proposed for the melting temperature detection of these materials as an alternative to conventional calorimetry. These methods are Raman spectroscopy, three-omega technique, and optical transmission.

Ingeniera Civil Electricista
La presente memoria tiene por objetivo principal optimizar el despacho de una central solar térmica, que tiene como sistema de almacenamiento tanques de sales fundidas, y que además considera el funcionamiento de una caldera auxiliar para recalentar el fluido circulante en el campo solar. Para cumplir con el objetivo se evaluaron los principales factores influyentes, se realizó un análisis del comportamiento de los costos marginales de las dos subestaciones cercanas a la posible ubicación de la planta, estimando el funcionamiento mensual de la planta para diferentes formas de operación. En este contexto, se implementó un mapa de comportamiento de la central, para estudiar el funcionamiento en un rango variado de escenarios, para así obtener una estadística de las horas en las que el almacenamiento estaba activo, y cuando era la caldera auxiliar la que tenía el peso de la generación. Asimismo fue posible discernir las combinaciones de salida de turbina y porcentaje de combustible fósil que lograban una mejor eficiencia del bloque de potencia. El mapa de comportamiento también identificó los escenarios en los que el fluido térmico alcanza su mayor temperatura y se tenía una cantidad más alta de pérdidas térmicas, además de identificar en qué meses se generaba el mayor gasto en combustible fósil. Una vez terminado el mapa de comportamiento, se diseñaron dos conjuntos de estrategias, una plana a lo largo del día, con una salida de turbina al 100% y otra que permite una fluctuación de generación entre un 80% y un 110%. Cada conjunto está definido por diferentes escenarios, en algunos de los cuales se daba preferencia al almacenamiento y en otros a la caldera auxiliar. Los resultados de las estrategias diseñadas se valorizaron, obteniendo los ingresos por generación y los costos por concepto de combustible fósil para la caldera auxiliar. Además se determinaron las alternativas que presentaban una mejor eficiencia a lo largo del año. Se determinó que el escenario que contemplaba una generación diferenciada a lo largo del día, pese a tener durante gran parte del año un margen de ingreso similar a la producción plana, era una mejor opción dado que el gasto en combustible era menor y, por lo tanto, implica una menor contaminación por emisiones de dióxido de carbono. Finalmente se presenta un resumen del comportamiento de la central, con los datos de generación bruta y neta anual, el consumo de agua, las horas de generación y la eficiencia promedio de la planta.

El protagonisme creixent de la tecnologia solar termoelèctrica entre el ventall de les energies renovables es centra en la seva capacitat d’adaptar la seva producció a la demanda energètica exigida. La gestionabilitat d’aquest tipus de centrals s’ha aconseguit amb la integració de sistemes d’emmagatzematge tèrmic en les mateixes. La major part dels sistemes d’emmagatzematge tèrmic, ja sigui els que s’utilitzen a nivell comercial com aquells que es troben en fase de desenvolupament proposen l’ús de sals inorgàniques foses com a medi d’emmagatzematge. Aquestes sals presenten l’inconvenient de la seva alta corrosivitat a altes temperatures. Per un costat, s’han analitzat els fenòmens de corrosió associats a les sals solars utilitzades a la planta pilot TES-PS10 mitjançant la instal·lació de racks de testimonis de corrosió als tancs de sals. A més, al finalitzar l’operació de la instal·lació pilot s’ha dut a terme un estudi post-mortem dels seus. Finalment, amb l’objectiu d’abaratir el cost de l’inventari de sals, s’ha analitzat a nivell de laboratori la corrosivitat de diferents mescles de nitrats de baixa puresa. El segon bloc de la tesi es centra en els sistemes d’emmagatzematge tèrmic en calor latent. Concretament, s’analitza la corrosió associada a la mescla peritèctica 46% LiOH-54% KOH proposta com a material de canvi de fase en un mòdul d’evaporació d’instal·lacions termoelèctriques de generació directa de vapor. D’aquesta forma, s’han dut a terme una sèrie d’assajos a nivell de laboratori amb l’objectiu d’avaluar el comportament envers la corrosió de diferents materials en contacte amb aquests hidròxids.
El creciente protagonismo de la tecnología solar se centra en su capacidad para adaptar su producción a la demanda energética exigida. La gestionabilidad de este tipo de centrales se ha conseguido mediante la integración de sistemas de almacenamiento térmico en sales fundidas. El uso de sales fundidas en sistemas de almacenamiento térmico presenta el hándicap de su corrosividad a alta temperatura. El primer bloque de la Tesis analiza los fenómenos de corrosión asociados a las sales solares en la planta piloto TES-PS10 mediante la instalación de racks de corrosión en los tanques de sales. Además, se ha llevado a cabo un estudio post-mortem de componentes de la instalación. Finalmente, se ha analizado a nivel de laboratorio la corrosividad de distintas mezclas de nitrato de baja pureza. El segundo bloque de la tesis se centra en los sistemas de almacenamiento en calor latente. En concreto, se analiza la corrosión asociada a la mezcla peritéctica 46% LiOH-54% KOH propuesta como material de cambio de fase en el módulo de evaporación en plantas de generación directa de vapor. De este modo, se han llevado a cabo ensayos de corrosión a nivel de laboratorio para evaluar el comportamiento a corrosión de distintos materiales en contacto con los hidróxidos.
The growing of concentrated solar power (CSP) within the different renewable energies is due to its ability to adapt the production to the required energy demand. The dispatchability of this type of plants has been achieved through the integration of molten salts thermal storage systems (TES). Molten salts have a handicap associated to their corrosiveness at high temperature. First block of this Thesis analyzes the corrosion phenomena associated with solar salts used in TES-PS10 pilot plant by installing corrosion racks in the salt tanks. Moreover, a postmortem study of different components was performed after facility shut down. Finally, in order to reduce the cost of the salt inventory in TES systems, the corrosivity of different low purity nitrates mixtures has been analyzed at laboratory scale. The second block of the Thesis focuses on latent heat storage systems. Specifically, it has been analyzed the corrosion associated with the proposed 46% LiOH-54% KOH peritectic mixture as a phase change material in the evaporation module of direct steam generation (DSG) CSP plants. Thus, corrosion tests have been performed at laboratory level to evaluate the corrosion performance of several materials in contact with such hydroxides.

Aquesta tesi contribueix en el camp de l’emmagatzematge d’energia tèrmica (TES) per aplicacions de fred solar i centrals termosolars. Concretament, en la validació i optimització de la tecnologia TES a través de l’experimentació a escala de planta pilot. La present tesi s’ha dividit en dues parts. Una, on s’estudien dues tècniques de millora de la transferència de calor en sistemes d’emmagatzematge per calor latent per aplicacions de fred solar. I una altra, on s’estudia la viabilitat d’un intercanviador de plaques per operar en un sistema d’emmagatzematge de doble tanc per centrals termosolars de cilindre parabòlic. Així com la influència de les estratègies d’operació i del fluid caloportador en el procés de transferència de calor en el mateix intercanviador. Els diferents estudis d’aquesta tesi han estat realitzats mitjançant la planta pilot de la Universitat de Lleida construïda l’any 2008 amb la col·laboració d’Abengoa.
Esta tesis contribuye en el campo del almacenamiento de energía térmica (TES) para aplicaciones de frío solar y centrales termosolares. Concretamente, en la validación y optimización de la tecnología TES a través de la experimentación a escala de planta piloto. La presente tesis está dividida en dos partes. Una, donde se estudian dos técnicas de mejora de la transferencia de calor en sistemas de almacenamiento por calor latente para aplicaciones de frío solar. Y otra, donde se demuestra la viabilidad de un intercambiador de placas para operar en un sistema de almacenamiento de doble tanque para centrales termosolares de cilindro parabólico. Así como la influencia de las estrategias de operación y del fluido caloportador en el proceso de transferencia de calor en el mismo intercanviador. Los diferentes estudios de esta tesis se han realizado mediante la planta piloto de la Universidad de Lleida construida en 2008 con la colaboración de Abengoa.
This thesis has contributed to the thermal energy storage (TES) field applied in solar cooling and concentrated solar power plants. Specifically, it is focused on validation and optimization of TES technology through the experimentation at pilot plant scale. This thesis is divided in two parts. A first part, where two heat transfer enhancement techniques in latent heat storage systems for solar cooling applications have been studied. And a second part, where the feasibility of plate heat exchanger to operate in a two-tank molten salts TES system for parabolic trough solar plant has been demonstrated. Moreover the influence of operational strategies and heat transfer fluid in heat transfer process of the same heat exchanger has been studied. The different studies included in this thesis has been performed through the pilot plant of University of Lleida built in 2008 in collaboration with Abengoa.

In this thesis, the compatibility of some structural alloys with the most recent high-temperature candidates as storage media (molten salts) to be used in thermal energy storage (TES) for the next generation of concentrating solar power (CSP) plants is investigated. This study endeavours to investigate the thermal and corrosive impacts of molten salts on commercial alloys by developing methods to measure and track the material degradation in contact with the corrosive medium. The role of material microstructure on corrosion and/or oxidation behaviour is studied and discussed in detail.

Parabolic trough power plants have been the most commercially implemented solar thermal electricity plants in the world. As such, several studies have been carried out over the last years in order to improve the efficiency/reduce the costs of this type of plants. From here it came the possibility of using the salts, that are currently used in this type of plants as storage fluid only, as heat transfer fluid (HTF). Its use as HTF seems to be a viable solution, however its implementation requires careful analysis. The project that gave rise to this dissertation aims to study this feasibility. During this work, the advantages and disadvantages of the salts in relation to the thermal oils (HTF currently used in this type of installations) will be presented and demonstrated, and SAM simulations will be performed to analyse the performance of a platform with the different fluids. Finally, the changes caused in the LCOE as well as in the power block design and efficiency will be determined; Resumo: VANTAGENS E DESVANTAGENS DOS SAIS FUNDIDOS DE BAIXO PONTO DE FUSÃO NUM SISTEMA DE FOCO LINEAR As centrais lineares de coletores cilíndrico-parabólicos são atualmente a tecnologia de geração solar termoelétrica mais utilizada em todo o mundo. Como tal, vários estudos têm vindo a ser realizados ao longo dos últimos anos com o intuito de melhorar a eficiência/reduzir os custos deste tipo de plantas. Daqui surgiu a possibilidade de utilizar os sais fundidos, já utilizados neste tipo de plantas apenas como fluido de armazenamento, também como fluido de transferência de calor (HTF). A sua utilização como HTF parece ser uma solução viável, no entanto a sua implementação requer uma análise cuidada. O projeto que deu origem a esta dissertação tem como objetivo estudar essa viabilidade. Ao longo deste trabalho serão apresentadas e demonstradas as vantagens e desvantagens dos sais em relação aos óleos térmicos (HTF utilizado atualmente neste tipo de instalações), realizadas simulações em SAM para analisar a performance de uma plataforma com os distintos fluidos e por fim determinadas as alterações provocadas no LCOE assim como no desempenho e eficiência do bloco de potência.

Thesis: S.B., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2015.
"June 2015." Cataloged from PDF version of thesis.
Includes bibliographical references (page 29).
Renewable energies can reduce the dependence on fossil fuels. Solar thermal systems designed to use molten salts to directly absorb the solar heat are promising due to (1) potentially higher efficiency in capture of sunlight and (2) use of the salt to simultaneously capture sunlight and store heat in the salt. The optical properties of the molten salts are crucial for the design of such thermal systems because they determine the depth of the salt required to absorb sunlight and allow modeling of the performance of such systems. Molten salts are also being developed as coolants for high temperature reactors. Optical properties are also required to determine the radiative heat transfer of the coolant. The objectives of this thesis were to build a better system to measure these properties and measure the optical properties of the proposed salt for a direct absorption concentrated solar thermal system. The attenuation coefficient of light in a binary nitrate salt mixture (KNO 3-NaNO3 40-60 wt%) was measured over the wavelength range 833-2500 nm and the temperature range 300-400°C. This salt is the leading candidate for the first generation of a proposed concentrated solar power on demand (CSPonD) concept [3]. The relevant data was obtained using a FTIR spectrometer and an experimental apparatus designed for semitransparent liquids. The apparatus was validated using the published data for the attenuation of light in deionized water. The attenuation coefficients of the binary nitrate salt mixture for the lower wavelengths matched the data obtained by Passerini [1]. For the longer wavelengths, the attenuation coefficient peaked around 2.5 Pm as predicted by Drotning [2]. Since certain metallic components of solar and nuclear systems are exposed to the molten salt, it is important to characterize the behavior of their reflectivity in the presence of the molten salt. The reflectivity of 304L stainless steel was measured for the wavelength range 600-5000 nm at incident angles of light 10°, 40°, and 70° after an 8-day molten salt immersion test. The reflectivity was measured to be less than 10% for the solar spectrum.
by Shapagat Berdibek.
S.B.

Solar-thermal energy systems that involve the deposition of radiation in absorbing high temperature molten salts to harness the entire solar spectrum and achieve high efficiencies and low Levelised Cost Of Energy (LCOE) are of considerable interest for power generation. From a design stand point, to achieve a competitive solar power generation devices, it is imperative to have an accurate knowledge of the inherent physical processes of such a fluid system. Thus under high temperature conditions, detailed understanding of the heat transfer and fluid flow characteristics in an irradiated fluid is considered. The work investigates the spectral dependent heat transfer and fluid dynamics in a thermal storage concept which uniquely combines a volumetric receiver and a single tank thermal store. The Thermal Energy Storage (TES) is protypical of a small scale concept concentrated solar plant. Advances in computing power, has seen Computational Fluid Dynamics(CFD) consolidated as a powerful tool employed by researchers and engineers to simulate real world behaviour and complex phenomena to a certain degree of accuracy with low effort in time, personnel and resources. This thesis is focused on the development of a realistic numerical model capable of predicting the local volumetric absorption of solar radiation in a fluid layer which provides an improved understanding of the hydrodynamic and thermal conditions in an enclosed fluid layer. Computational Fluid Dynamics is used to simulate the transient heat transfer and fluid flow determined by a combined influence of volumetric absorption and natural convection in a high temperature fluid filled enclosure. The enclosure is studied for the specific case in which a high temperature salt is first heated by direct volumetric absorption of the incident solar radiation and secondly by natural convection from a absorber plate located at the bottom of the enclosure whose sole purpose is to absorb all non-absorbed radiation reaching the lower surface. The current models considers the depth dependence absorption of solar radiation based on (i) a solar weighted absorption coe cient (assumed constant over all wavelengths) and (ii) spectral absorption coe cient characterised by wavelength band based on a standard solar spectrum reference. A commercially available CFD Package based on Finite Element Method (FEM), COMSOL Multiphysics is used to discretise and solve the Navier Stokes and energy equation under transients heating conditions for a non Boussinesq condition by accounting for the temperature variable properties of molten salts. A time-dependent and Backward Differentiation Formula (BDF) solver using implicit time-stepping methods is combined with refined mesh to solve the non-linear PDE. Validity of the numerical tool has been conducted, by comparing results from published results found in literature with corresponding numerical results. The mesh element optimum sizes and time steps used conform to those obtained in validation models. Simulations have been conducted for a daily charging period of three hours as used in conjunction with a solar system. The effects of bottom absorber plate, flux Rayleigh number, aspect ratio, variable Air Mass and inclination angle have also been investigated. Numerical results are presented in terms of surface plots, temperature contours, and velocity contours and streamlines which show the thermal field distribution and flow structures, for volumetric absorption of thermal radiation coupled with natural convection. Performance criteria are based on quantification of the level of thermal stratification using the MIX number, the dimensionless exergy and capture efficiency. Three dimensionality effects were studied by considering three dimensional simulation for the same problem. The results show that the present method and models are capable of capturing the main features of the flow and the overall performance of these turbulence models in terms of predicting time-averaged quantities. Results obtained indicate a nonlinear temperature profile consisting of two distinct layers: a surface layer and a bottom layer. The numerical results reveal natural convection in the cavity follows an initial stage, a transitional stage and a quasi-steady stage. Results indicate that volumetric absorption of solar radiation, when coupled to natural convection has a direct influence on the thermal field through the disparities in absorption and emission phenomena. The isotherms and streamlines show that the natural convective heat transfer and flow are quite different from those obtained in differentially heat enclosures. Thus the heat transfer mechanism destroys a symmetry of the system that relates clockwise and counter clockwise flows. Temperature and flow field are found to be greatly influenced by the aspect ratio (H/D) of the store and the flux Rayleigh number. It is found that the predicted heat transfer from the lower surface in the cavity is increased when the simulation is extended from two to three dimensional. Results obtained indicated that increasing the aspect ratio, Air Mass and inclination angle all result in increasing levels of thermal stratification. Natural convection from the lower absorber surface is found to increase with increasing flux Rayleigh number.

A humid subtropical climate is characterized by a predominant partly cloudy sky, which increases the intensity of solar radiation, and makes shade an essential requeriment. Thus, the indoor daylighting environment may depend more on reflected light than on direct light. Planning the shape of the surfaces is an important means of making full use of the reflected sunlight. In this regard, shading devices can be designed that just obstruct the view of the sky enough to provide shade, by reflecting the sunlight for the environment, and reducing this loss. The aim of this doctoral research is to study the performance of shading devices in classrooms with regard to their luminous power when capturing reflected sunlight in Maceió, so as to determine the potential use of sunlight in these elements. Three variables of these devices were defined for this: the number of pieces, specularity and reflectance of the surfaces devices. The resulting models from the combination of these variables were analyzed to calculate the reflected sunlight efficiency, rate employed in this research. The software used for the computational simulations of these models was TropLux. Statistical analyses were conducted to determine which variables had the greatest impact on the reflected sunlight efficiency and to relate the rate to the daylighting performance through indicators of availability, distribution and the maintenance of illuminance inside the environment: these included the annual average illuminance and uniformity rate, and spatial daylight autonomy. The results showed that the reflectance of the devices is the variable that has the most positive influence on the reflected sunlight efficiency, and is able to increase the rate by up to 142%. The annual average illuminance and the spatial daylight autonomy were positively related to the efficiency and the defined parameterization also led to an increase of their values. With regard to the distribution of illuminances, the variations of the analyzed parameters resulted in a reduction of the uniformity rate in most of the cases studied. The increase in specularity and specular reflectance in the models facing east reduced the rate by up to 34% and 41%, respectively. Increasing the number of components in the system devices installed in lateral openings, only provides a valid solution for the increase of the illumination when these elements have a high reflectance, especially specular. This represents a more efficient strategy in the case of the north facade. Among the analyzed models, in the systems with the largest number of components, and where the surface finishing process provides specular reflection, there is a greater use of sunlight in the reflected form. The use of light colors, such as white, beige and yellow, also benefit the use of sunlight, especially if they are used in materials with specular reflection. In contrast, the high reflectances resulted in a reduction of the uniformity of illumination in the environment. From the results of the studies carried out into reflected sunlight efficiency, it can be stated that it is possible to increase the use of sunlight through the variation of certain shading devices and, hence, to bring benefits by making daylighting available in the environment.
O clima quente e úmido caracteriza-se pelo predomínio do céu parcialmente nublado, o que torna intensa a radiação solar, impondo a necessidade de sombreamento. Assim, a iluminação natural no interior do ambiente pode depender mais da luz refletida do que da luz natural direta. Planejar a forma das superfícies é um importante recurso para o aproveitamento da luz solar refletida. Neste sentido, dispositivos de sombreamento podem ser projetados para obstruir a visão do céu apenas o necessário para o sombreamento, refletindo a luz solar para o ambiente e minimizando essa perda. O objetivo geral desta pesquisa de doutorado é estudar o desempenho de dispositivos de sombreamento em salas de aula com relação à eficiência luminosa na captação da luz solar refletida, em Maceió, a fim de que seja identificado o potencial de aproveitamento da luz solar desses elementos. Para isso foram definidas três variáveis desses dispositivos: número de peças, especularidade e refletância das superfícies dos brises. Os modelos resultantes da combinação dessas variáveis foram analisados quanto à eficiência da luz solar refletida, índice proposto nesta pesquisa. O programa utilizado para as simulações computacionais desses modelos foi o TropLux. Análises estatísticas foram desenvolvidas a fim de identificar as variáveis de maior impacto para a eficiência da luz solar refletida e relacionar o índice ao desempenho da iluminação, através de indicadores de disponibilidade, distribuição e manutenção da iluminância no ambiente: iluminância média anual, uniformidade média anual e autonomia de luz natural espacial. Os resultados mostraram que a refletância dos dispositivos é a variável que mais influencia positivamente a eficiência da luz solar refletida, chegando a incrementar em até 142% o índice. A iluminância média anual e a autonomia de luz natural espacial foram relacionados positivamente à eficiência e a parametrização definida também contribuiu para a ampliação dos seus valores. Quanto à distribuição de iluminâncias, a variação dos parâmetros analisados resultou em redução do índice de uniformidade, na maioria dos casos estudados. O aumento da especularidade e da refletância especular em modelos voltados para Leste reduziram o índice em 34% e 41%, respectivamente. Aumentar o número de peças em sistemas de dispositivos inseridos em aberturas laterais apenas corresponde a uma solução válida para o incremento da iluminação quando tais elementos possuem alta refletância, sobretudo especular. Tal medida representa uma estratégia mais eficiente no caso da fachada Norte. Entre os modelos analisados, os sistemas com maior número de peças, cujo acabamento das superfícies proporciona reflexão especular, são capazes de promover maior aproveitamento da luz solar na forma refletida. O uso de cores claras, como branco, creme e amarelo, também favorece o aproveitamento da luz solar, sobretudo se forem empregadas em materiais com reflexão especular. Por outro lado, altas refletâncias resultaram em redução da uniformidade da iluminação no ambiente. A partir dos resultados dos estudos de eficiência da luz solar refletida desenvolvidos, pode-se afirmar que é possível ampliar o aproveitamento da luz solar através da variação de determinadas características de dispositivos de sombreamento e, consequentemente, trazer benefícios para a disponibilidade de iluminação no ambiente.

One of the most relevant problems to solve at a planetary scale is the access to an affordable clean source of energy as CO2 equivalent emissions should be reduced significantly. Some authors aim for a zero emissions target for 2050. Renewable energies will play a leading role in this energy transition, and solar energy with storage is a promising technology exploring a renewable and worldwide available resource. Within the present thesis component development like a new thermal storage thermocline tank design or having latent heat storage capability are technological developments that have been pursued and analyzed on a system perspective basis, focusing on reducing the LCOE value of a commercial STE plant using TRNSYS software. Material research with molten salts mixtures and cement based materials has been performed at lab scale. A fully validation should occur through a 13 partners pan-European H2020 project called NEWSOL which has been developed supported on the laboratory data obtained. Moreover, incorporation of local available material, “modern slag” from an old mine of Alentejo region, was also studied. The material could be used as an aggregate incorporated into calcium aluminate cement (CAC) or as filler. This would help to solve a local environmental complex problem related to soil, air and water pollution due to heavy metals and mining activity in Mina de São Domingos, Southeast of Portugal. The integration of these results underlies a broad energy transition model, a proposal is presented in this thesis, with the aim to foster development towards a sustainable usage of resources and promote clean technologies especially in the energy sector. This model can be locally adapted depending on the pattern of existing industries. The goal is to achieve a smooth transition into a clean tech energy society in line with the target of achieving zero emissions for 2050; Optimização Energética de uma Central de Concentração Solar com Armazenamento de Energia Resumo: Um dos problemas mais relevantes a resolver a uma escala planetária é o acesso, com um custo moderado, a fontes limpas de energia considerando que as emissões equivalentes de CO2 derão ser reduzidas drasticamente. Alguns autores ambicionam mesmo um objetivo de zero emissões em 2050. As energias renováveis irão desempenhar um papel preponderante nesta transição energética, sendo que a energia solar com armazenamento é uma tecnologia promissora que aproveita um recurso renovável e disponível em boa parte do Planeta. Na presente tese foi realizado o desenvolvimento de componentes nomeadamente o design que um novo tanque do tipo termocline, ou de novos elementos recorrendo ao calor latente, desenvolvimentos tecnológicos que foram analizados de uma perspectiva de sistema, dando o enfoque na redução do custo nivelado da electricidade (LCOE) para uma planta Termosolar usando o software TRNSYS. Foi também realizada investigação em laboratório ao nível dos materiais com várias misturas de sais fundidos inclusivé em contacto directo com materiais de base cimenticia. Uma validação completa deverá ocorrer no projeto NEWSOL do programa H2020 que reúne um consórcio de 13 parceiros europeus e que foi preparado e submetido tendo por base os resultados laboratoriais obtidos. Adicionalmente, incorporação de material disponível (escória de minério) de uma mina abandonada da região do Alentejo foi outro dos aspectos estudados. Verificou-se que este material poderá ser utilizado como agregado num ligante do tipo cimento de aluminato de cálcio (CAC) ou como “filler”. Este re-aproveitamento resolveria um problema ambiental complexo derivado do elevado conteúdo de metais pesados resultantes da actividade de mineração e que actualamente provocam poluição do solo, água e ar na área da Mina de São Domingos, Sudeste de Portugal. Estes progressos deverão ser integrados num modelo de transição energética mais amplo. Na presente tese, uma proposta concreta é apresentada, com o objectivo de incentivar o desenvolvimento na direção de uma utilização sustentável dos recursos e a promoção de tecnologias limpas nomeadamente no sector da energia. Este modelo poderá ser adaptado localmente dependendo do padrão de indústrias existente. O objectivo é atingir uma transição suave para uma sociedade de energias limpas em linha com o objectivo de atingir zero emissões de CO2 equivalente em 2050.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This work addresses topics such as shading devices, shading and daylighting. It aims at verifying the efficiency of shading devices found classroom buildings at UFPB's campus I, with respect to shading and daylighting. The results of the research focus in the diagnosis of the solutions in the case study, by using three dimensional models (3D) and computer simulation. The digital models were constructed from data collected in field surveys. The computer programs used were the Solar Tool, Ecotect and Daysim. In parallel, we investigated a set of hypothetical situations, considering all the solutions found in the survey, in order to identify the performance of the solutions in other orientation facade. The evaluation of the models was made from performance measures such as the percentage of shading, percentage of sky visibility and useful daylight illuminances (UDI). From the results, we observed that: a) south-oriented façades with unprotected openings allow for environments with higher levels and better distribution of natural lighting; b) a large part of the orientation facade analyzed, except in the northwest and east, more than 50% of the samples obtained a good performance of daylighting; c) the percentage of shading is not enough to say whether an element of sunscreen is effective or not, which can generate misleading conclusions when used alone; d) the correlation of the performance of daylighting and performance of shading with the percentage of sky visibility, showed that for every orientation facade there is an optimal ratio between the percentage of shading and the percentage of sky visibility, and for the facade analyzed, the values of these measures are generally around 88.7% of shading of the opening and 8.1% of sky visibility.
Este trabalho aborda temas como elementos de proteção solar, sombreamento e iluminação natural. Tem como objetivo a verificação da eficiência de proteções solares encontradas em edificações de salas de aula no campus I da UFPB, no que diz respeito ao sombreamento e à iluminação natural. Os resultados da investigação centram-se no diagnóstico das soluções encontradas no estudo de caso, através da utilização de modelos tridimensionais (3D) e simulação computacional. Os modelos digitais foram construídos a partir de dados coletados em levantamento de campo. Os programas computacionais utilizados foram o Solar Tool, Daysim e o Ecotect. Em paralelo, foi investigado um conjunto de situações hipotéticas, considerando todas as soluções encontradas no levantamento, com objetivo de identificar o desempenho das soluções em outras orientações. A avaliação dos modelos foi feita a partir de medidas de desempenho como o percentual de sombreamento, percentual de visibilidade do céu e do useful daylight illuminances (UDI). Com os resultados obtidos foi possível observar que: a) fachadas com aberturas sem proteção orientadas para o Sul geram ambientes com melhores níveis e distribuição da iluminação natural; b) em grande parte das orientações analisadas, exceto na Noroeste e Leste, mais de 50% da amostra obteve um bom desempenho da iluminação natural; c) o percentual de sombreamento não é suficiente para afirmar se um sombreamento é eficaz ou não, podendo gerar conclusões equivocadas quando utilizado isoladamente; d) a correlação da performance da iluminação natural e do desempenho do sombreamento com o percentual de visibilidade do céu, mostrou que para cada orientação existe uma relação ideal do percentual de sombreamento com o percentual de visibilidade do céu, sendo que para as orientações analisadas os valores destas medidas se encontraram, em geral, próximo de 88,7% de sombreamento da abertura e 8,1% de visibilidade do céu.

Sous l'impulsion de l'Union européenne et de l'ouverture des marchés, le droit de l'énergie a considérablement évolué ces dix dernières années. Les textes en matière d'énergie solaire photovoltaïque se sont amplifiés depuis la loi « Pope » jusqu'aux lois « Grenelle I » et « Grenelle II », et récemment avec la loi n° 2015-992 du 17 août 2015 relative à la transition énergétique pour la croissance verte, suivies de nombreux décrets pour leur application et une jurisprudence de plus en plus abondante en la matière. Il en résulte un ensemble considérable de textes évolutifs et complexes dont l'accès reste difficile à appréhender et à appliquer. Cette instabilité des règles régissant la matière – certes inévitable au regard des nécessaires changements requis par toute innovation – est source d'insécurité juridique et s'avère extrêmement déstabilisante pour les acteurs du secteur en quête de visibilité. En outre, l'installation d'une centrale de production d'électricité photovoltaïque au sein de son habitation, est à la fois un projet d'investissement et une opération de construction immobilière, qui exige des garanties tant sur le plan financier qu'au niveau de la construction (sûretés et assurances) pour permettre de mieux maîtriser les risques et rassurer les parties au projet. Néanmoins, les nombreux freins contractuels, administratifs et financiers ralentissent le développement du photovoltaïque et se heurtent aux ambitions de promouvoir cette « électricité verte » sur l'ensemble du territoire et notamment parvenir à l'autonomie énergétique de l'île de La Réunion. Ainsi, cette étude présente et analyse le droit de l'énergie photovoltaïque, visant notamment le particulier à La Réunion, sous ses différents angles (fiscal, financier, contractuel, administratif, urbanistique, des responsabilités) – à jour des textes les plus récents – et en explicite les modalités d'application à la lumière des multiples textes réglementaires, législatifs, guides professionnels et de la jurisprudence, que ce soit celle des tribunaux ou des autorités de régulation
Facing a weakening photovoltaic market and a sector already bedeviled recently by a huge increase of legal texts, private investors decrease. This thesis tackles legal framework concerning photovoltaic energy in Reunion Island. This will include the analysis of fiscal incentives such as investment grants and tax preferences, as well as more general environmental policy instruments (feed-in-tariffs and renewable subsidies and grants). Moreover, this will include the analysis of contracts such as loan agreement, sale contract, lease agreement and connection/Commissioning contracts, as well as more environmental aspect. At last, risks, insurances, liability comprising legal proceedings and guarantees will be studied in this thesis

The intensifying environmental problems demand nations to take immediate action. The industry sector alone accounts for 54 % of the global energy demand (year 2012) and the most common way for industries to get heat for its production, is still today by fossil-fuel boilers. One promising renewable energy source, which has great potential in replacing fossil-fuel boilers, is solar thermal energy. In order to meet all climate goals, the Paris agreement for example, renewable energy resources like solar thermal energy will become crucial. Absolicon Solar AB is a Swedish manufacturing company, whose main product is the solar collector T160. The T160 is a heat water producing collector, which is suitable for integrating in industrial heat water processes for temperatures up to 160 °C. One of the challenges the company faces, is to find suitable markets and customers to sell its product to. Two promising markets that Absolicon want to explore and eventually enter are the Food and Beverage market in Spain, and the District Heating market in Denmark. This study aims to give Absolicon a better understanding of these two markets of interest, in order for Absolicon to enter and direct the right value proposition of its product to the right customers. Thus two qualitative market researches were conducted, one for each market. Based on the results of the market researches, two business strategies were proposed respectively. Finally, a comparative study is carried out and relative conclusions are drawn.

Tesis (Doctora en Ciencias Químicas) - - Universidad Nacional de Córdoba. Facultad de Ciencias Químicas, 2018
La presente tesis aborda el estudio de las propiedades fisicoquímicas y fotoelectroquímicas de membranas de nanotubos de TiO2 modificadas con puntos cuánticos o “quantum dots” (Qdots) de CdSe para su potencial empleo como fotoánodos para celdas solares sensibilizadas con Qdots o “Quantum Dot Sensitized Solar Cells” (QDSSC). Este trabajo también está abocado a la búsqueda de diferentes estrategias para mejorar la eficiencia de conversión de energía solar en energía eléctrica de dichas superficies fotoactivas. La primera parte de la tesis consta de la introducción y la presentación de los objetivos. El primer capítulo es una introducción de los conceptos básicos acerca de la energía solar y dispositivos fotovoltaicos. Se exponen los hechos que justifican el estudio y desarrollo en torno al aprovechamiento de este tipo de energía y se presenta el contexto general de los dispositivos fotolvoltaicos, en la actualidad y particularmente en la Argentina. En el capítulo 2 se introducen conceptos fundamentales de las celdas solares sensibilizadas con Qdots. Se explican las partes constituyentes de las celdas solares, su modo de operación y el mecanismo cinético en la generación de la fotocorriente. Se enumeran y explican brevemente las diferentes técnicas de caracterización morfológica y funcional de este tipo de celdas solares. En el capítulo 3 se menciona el objetivo principal de la tesis y se enumeran los objetivos específicos para llevar a cabo la presente investigación. En la segunda parte de la tesis se presentan los resultados logrados. Se aborda la síntesis y caracterización de arreglos nanotubulares de TiO2 obtenidos por anodización electroquímica del titanio en el capítulo 4 y de Qdots de CdSe y CuInS2 por las metodologías de inyección en caliente y termólisis en el capítulo 5. En el capítulo 6 se presentan los estudios llevados a cabo acerca del proceso de sensibilización óptica a través de la modificación superficial de los nanotubos de TiO2 por la adsorción directa de Qdots de CdSe, en la búsqueda de las mejores condiciones para lograr un grado de cubrimiento óptimo. Se exponen también los resultados de la caracterización de la respuesta fotoelectroquímica de las membranas de nanotubos modificadas con Qdots, empleadas como fotoánodos. En el capítulo 7 se analizan los cambios causados por el tratamiento térmico en las propiedades eléctricas y fisicoquímicas de los fotoánodos y se exponen las condiciones óptimas de tratamiento térmico encontradas para lograr aumentos en la fotocorriente generada. El capítulo 8 está abocado en los detalles de la construcción de celdas solares sensibilizadas con Qdots. Se exponen los resultados obtenidos relacionados con la caracterización de las celdas armadas, empleando los fotoánodos obtenidos y estudiados en los capítulos previos y se discute sobre los aspectos a mejorar en cuanto a la construcción de estas celdas. El capítulo 9 aborda la temática de generación de Hidrógeno por la ruptura fotoelectroquímica del agua y los resultados obtenidos empleando como fotoánodo la membrana de nanotubos de TiO2. Finalmente se presentan las principales proyecciones en vistas de continuar con dicho trabajo en el futuro. La tercera parte de la tesis aborda las conclusiones principales de la tesis y las proyecciones a futuro, en el capítulo 10.
2020-12-31
Torresan, María Fernanda. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina.
Iglesias, Rodrigo Alejandro. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de FísicoQuímica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Físico Química de Córdoba; Argentina.
Mariscal, Marcelo M. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Teórica y Computacional. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Fisicoquímica de Córdoba; Argentina.
Granados, Alejandro Manuel. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Fisicoquímica de Córdoba; Argentina.
Pérez, Manuel Alejo. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Fisicoquímica de Córdoba; Argentina.
Chesta, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Tecnologías Energéticas y materiales avanzados; Argentina.

碩士
國立中央大學
化學研究所
98
With increasing renewable energy demands, dye-sensitized solar cells (DSSCs) are being explored extensively for photovoltaic applications because of their versatility and low cost of manufacture. In these cells the sensitizer is one of the key components, harvesting the solar radiation and converting it to electric current. To date, the only ruthenium sensitizers for DSSC applications that have been described in the literature are those bearing bipyridine or polypyridine ligands. But ruthenium metal is not full in the earth，therefore enhances the cost of manufacture. We design the new class of organic dye with different metal like Co, Ni, Cu, Zn, Pd, Pt were used complex with compound as sensitizer. We hope the kind of Metal salen-ligand complexes could get good performance in DSSCs.

Estágio realizado na Fundació CTM Centre Tecnològic, e orientado por Jose Luis Romeral Martínez
Tese de Mestrado Integrado. Engenharia do Ambiente. Faculdade de Engenharia. Universidade do Porto. 2012

Estágio realizado na Fundació CTM Centre Tecnològic, e orientado por Jose Luis Romeral Martínez
Tese de Mestrado Integrado. Engenharia do Ambiente. Faculdade de Engenharia. Universidade do Porto. 2012

碩士
國立臺北科技大學
有機高分子研究所
101
Dye Sensitized Solar Cells (DSSCs) have attracted tremendous interest due to the possibilities of low cost, simple fabrication steps, and flexibility. TheTiO2 thin film photoanode is one of the important components affecting the performance of DSSCs. In this thesis, the modification of TiO2 nanopastes employing a series of ammonium salts such as ammonium carbonate, ammonium bicarbonate, tetraethyl ammonium bicarbonate, ammonium acetate, and ammonium hexaflurophosphate were performed. The influences of various ammonium salts on the TiO2 nanopastes as well as their application in DSSCs were studied. It was found that the utilization of ammonium carbonate shows the enhanced DSSC performance compared to those without modification. The concentration of addition of ammonium carbonate was varied as 0, 3, 5, 7 and 9 wt %, in which, the 7 wt % ammonium carbonate based TiO2 photoelectrode achieved the optimal overall photoconversion efficiency of~8%.

碩士
國立臺北科技大學
有機高分子研究所
101
TiO2 nanocubes were synthesized by hydrolysis of titanium tetra-isopropoxide as Ti precursors, followed by hydrothermal treatment under the basic condition. Various kinds of TiO2 colloids were prepared by adding ammonium salts with different alkyl chains such as ammonium hydroxide, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, and tetrabutyl ammonium hydroxide before hydrothermal crystallization. The crystal phase, shape, and morphology of TiO2 nanocubes were studied by XRD, TEM, and SEM analysis. It was found that the TiO2 nanocubes were pure anatase and tended to assemble with well-ordered and close-packed domains. Both alkyl length and hydrothermal duration influence the TiO2 nanocube formation efficiency. The ammonium salts with longer alkyl chain could form TiO2 nanocubes in shorter hydrothermal time and vice versa. The above TiO2 nanocubes were applied as photoanode materials in dye-sensitized solar cells. A systematic comparison between alkyl chain length and the photo-conversion efficiency of DSSCs fabricated by various TiO2 nanocubes were discussed in this work.

Solar energy is increasingly considered as one of the most favourable alternative sources of energy to conventional fossil fuels to mitigate carbon emissions. Despite the advantages, the intermittent availability of the solar resource causes a gap between demand and supply, and solar power plants cannot meet energy demands at night without energy storage. Concentrating Solar Power (CSP) plants have the distinctive feature that thermal energy storage (TES) is relatively easy to integrate to support energy demand in the absence of solar radiation for several hours. Thus, development of energy efficient and cost-effective thermal storage systems is vital for the CSP industry. The selection of a particular thermal storage media requires understanding of thermo-physical properties, operating limitations, and chemical compatibility. This thesis focusses on the development of novel high-temperature TES media for next generation concentrating solar power plants. At present, the Levelised Cost of Electricity (LCOE) for CSP plants is higher than for conventional fossil fuel power plants. It is essential that efficiency improvements and cost reductions are made, to achieve cost-effective clean electricity through CSP. A key focus for next-generation CSP plants in to enable high-efficiency power cycles (such as the supercritical CO2 Brayton cycle, >700ºC), requiring a higher maximum temperature compared to the state-of-the-art. An increase in temperature in the power block impacts design decisions for most components (including the solar field, solar receiver design, and containment materials) and choice of the heat transfer fluid and TES media. Nitrate salts used in state-of-the-art CSP plants cannot be used above 600°C, and possible alternative salts include carbonates, chlorides, fluorides, and hydroxides. Of these, based on extensive critical review of different alternatives, chloride salts are of particular interest due to their natural abundance, and hence low cost. A novel ternary eutectic salt mixture for high-temperature sensible thermal energy storage (HTSTES), composed of sodium chloride, potassium chloride and magnesium chloride (NaKMg–Cl) is developed and its thermo-physical properties are tested and compared with other potential binary and ternary mixtures. Based on the analysis, NaKMg–Cl has an acceptable melting point (387°C), reasonable heat capacity (1.18 J g-1 K-1), high thermal stability (>700°C) and low storage media cost (4.95 USD/kWh). These combined traits of NaKMg–Cl make it a potential thermal storage solution for HTSTES. One of the desirable characteristics of HTSTES media is low melting point, to avoid freezing the pipes and other parasitic losses. In further attempts to identify a ‘sweet spot’ between the melting temperature of the mixture and storage media cost, multiple quaternary chloride mixtures (NaKMgZn–Cl) are developed by adding different proportions of ZnCl2 (10% to 90%) to the existing ternary NaKMg–Cl salt. The results show a significant reduction in melting temperature is possible, but with a steep increase in the storage media cost. The last part of the thesis explores the system level techno-economic analysis for three salt candidates (the ternary NaKMg–Cl and two of the quaternary NaKMgZn–Cl salts) identified for HTSTES application. LCOE calculations are made using the default System Advisor Model (SAM) power tower model, with cost and performance inputs based on 2020 SunShot CSP targets. The exception is the thermal energy storage system, for which costs are calculated separately and depend on the thermo-physical properties and cost of the salt media. For the salts identified, a trend of increasing LCOE with decreasing melting point is identified. The standout is the ternary NaKMg–Cl eutectic, which has the lowest LCOE of the salt candidates. However, there may be certain applications where even lower melting point is required, and in these cases, this work serves as a guide to the likely LCOE penalty for selection of a more expensive storage medium with more favourable melting point.

碩士
國立清華大學
化學工程學系
98
In this thesis, quaternary ammonium salt-based ionic liquids are used to serve as a low-volatility solvent for electrolytes in dye-sensitized solar cells (DSSCs). There are three main advantages for the use of volatile organic solvents for electrolytes, including fast diffusion rates, high ionic conductivities, and low viscosities. However, because of the high volatility of the electrolyte solvent, the cell performance decreases when the solvent vapor leaks. In this thesis, a series of quaternary ammonium salts-based ionic liquids are prepared from heating mixtures of quaternary ammonium salts and hydrogen bond donors. This series of liquids has the advantages of cost-effectiveness, easy preparation, low volatility, and excellent ionic conductivity when used as the solvents for electrolytes in DSSCs. A new quaternary ammonium salts (Acetylcholine iodide, ACI) is developed in this thesis. When used in DSSCs, constructed from P25 powders and D149 dye (a metal-free iodoline dye), the electrolyte gives a Jsc of 8.57 (mA/cm2), a Voc of 0.645 (V), a fill factor of 0.61, and an efficiency of 3.36%, which is 78% of that achieved by using the AN based electrolyte (efficiency of 4.3%) under the same measurement condition.

博士
國立臺北科技大學
有機高分子研究所
105
Dye-sensitized solar cells (DSSCs) represent a cheap and clean technology that harnesses solar energy efficiently and have been intensively studied. One of the key components in DSSCs is the inorganic TiO2 materials because of their great potential in a wide variety of applications and promising capability in photoelectrochemical solar cells. The aim of this thesis focuses on the development of various morphological TiO2 materials with the motivation to further enhance power conversion efficiency of DSSCs. Firstly, various TiO2 structures such as rice-, star-, and flower-shaped microstructures were successfully synthesized using tetramethylammonium hydroxide (TMAH) as ammonium salt by a surfactant assisted hydrothermal method. The effects of the versatile preparation parameters including the amount of titania precursor and surfactant, the addition of ethanol/water, and the hydrothermal process temperature and time on the TiO2 morphology were investigated. Rice-shaped TiO2 was comprised of anatase and brookite mixture crystal phases with an average length of 1.10m and width of 0.41 m. Star-shaped TiO2 with around 3.60 m diameter and flower-shaped TiO2 with a length of 3.75 m and width of 2.75 m showed crystal structures of anatase, rutile, and brookite ternary phases in the XRD analysis. Based on the DSSC device studies, these three types of morphologies are suitable as scattering layers because the star-, rice-, and flower-shaped TiO2 photoanodes based devices showed an 14, 10, and 3.2% efficiency improvement, respectively, over the device (a-TiO2) without scattering layer. Among them, the DSSC comprised of a photoanode coated with star-shaped (a-TiO2/ star-TiO2) microstructures yielded the highest photo-electric conversion efficiency of 9.56%. Both the strong light scattering ability and high dye adsorption of the prepared scattering layered TiO2were found to enhance the light harvesting efficiencies of the DSSCs. In addition, the effect of ammonium salts surfactant such as tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammomium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH) on the TiO2 morphology were further investigated. The results showed that the surfactants with different alkyl chain length of tetraalkylammonium cations (TAN+) had a great influence on the morphology, particle size, and crystalline phase of TiO2 particles. Under the same experimental conditions, the surfactants of TMAH, TEAH, TPAH, and TBAH resulted in the star-, flower-, rod-, and scree-shaped TiO2 particles (TM-, TE-, TP-, and TB-TiO2), respectively. The particle sizes were decreased in the range from 3.6 m to 220 nm while increasing the alkyl chain length of the surfactants. All the TiO2 powders showed an anatase phase besides the TiO2 prepared from TMAH surfactant. The photovoltaic investigations of DSSC based on these TiO2 samples as the scattering layers indicated that the TB-TiO2 cell exhibited excellent power conversion efficiency of 9.88%, which was higher than that of a device which fabricated without a scattering layer (8.83%). Among these scattering layers, TB-TiO2 has the optimum particle size (220 nm) with the highest surface area leading to the largest dye adsorption value and an excellent efficiency. In order to further increase the dye adsorption of the photoanodes, the scattering layer was prepared by mixing the large (TB-TiO2) and small sized (a-TiO2) particles as composites with different weight ratios, leading to the highest efficiency of 10.53% at TB-/ a -TiO2 (2:3). Further, TiO2 nanocubes were synthesized via hydrolysis condensation of TTIP in aqueous media, followed by hydrothermal treatment with different alkyl chain length such as NH4OH, TMAH, TEAH, and TBAH as assisted surfactants. The crystalline phase, shape, and morphology of TiO2 nanocubes were studied by XRD, TEM, and SEM analysis. These TiO2 nanocubes were pure anatase phase and tended to assemble with well-ordered and close-packed domains. Both alkyl chain length of ammonium salts surfactant and hydrothermal duration affected the TiO2 nanocube formation process. The ammonium salts surfactant with longer alkyl chain formed TiO2 nanocubes in shorter hydrothermal time and offered the smallest particle size. The above TiO2 nanocubes were applied as photoanode materials in N719 anchored DSSCs and one of the cells exhibited the best power conversion efficiency (7.85%).

碩士
國立交通大學
照明與能源光電研究所
105
In this research, three quaternary ammonium salts containing different counterions, including tetrabutylammonium bromide (TBABr), tetrabutylammonium tetrafluoroborate (TBABF4), and tetrabutylammonium hexafluorophosphate (TBAPF6), were incorporated into [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) as electron transporting layer (ETL). These salts-doped PCBM films revealed higher electron mobility and Fermi levels compared with the un-doped one. Better charge transfer at the interface between perovskite and salts-doped PCBM was also obtained from PL quenching experiments. Inverted perovskite solar cells with the configuration of ITO/PEDOT:PSS/CH3NH3PbI3/PCBM+salts/Ag were fabricated, and the JSC and FF of devices were significantly enhanced using salts-doped PCBM as ETL. The best device based on TBABF4-doped PCBM delivered a power conversion efficiency (PCE) up to 13.41%, which was superior to the one with undoped PCBM layer (PCE = 8.77%).

碩士
國立臺北科技大學
有機高分子研究所
100
(a)The New Saccharin Salts Used in the Catalytic Acylation Reaction and Recycling We had successfully synthesized and purified the salt made of DMAP and saccharin. It’s surprising to discover that DMAP-salt and the other salts have the similar structure, and they can used in the catalytic esterification reaction of the alcohol. Conversion yield percentage and reaction time compared with the literature data, the overall efficiency of the reaction about 30 times. However, the reaction without adding solvents and bases can be carried out at room temperature. This discovery is based on the crystallization for series of saccharin and saccharin’s compounds. In the thesis, we improve the disadvantages of catalysts recycling. The non-polar solvents can soluble the acylation product, but catalyst can’t. We use catalyst insoluble characteristics through the centrifuge can easily recycle catalysts. Furthermore, the recycle-easy catalysts are based on concept of modern green technology. (b)High Efficient Bis(fluoro-ponytailed) Bipyridine Ruthenium complexes containing Tetrabutylammonium for Dye-Sensitized Solar Cells We used particular by designed bis(fluoro-ponytailed) bipyridine binding with rethenium. After purification of crude dye by column chromatography, the product was analyzed and spectroscopically characterized by multi-nuclei NMR (1H, 19F and 13C), FTIR and FAB. We synthesis of the CT series of dyes containing different tetrabutylammonium numbers had H1TBA3 and H3TBA1 two types. Dye molecules with different tetrabutylammonium numbers of photoelectric conversion efficiency. UV-vis, CV and other instruments measured results compared with the N719. We study the different tetrabutylammonium numbers of the dye in the optical, electrochemical and photoelectric conversion efficiency.