Thermal energy storage (TES) in a concentrating solar power (CSP) plant allows for continuous operation even during times when solar radiation is not available, thus providing a reliable output to the grid. Energy can be stored either as sensible heat or latent heat, of which latent heat storage is advantageous due to its high volumetric energy density and the high Rankine cycle efficiency owing to the isothermal operation of latent thermal energy storage (LTES) system. Storing heat in the form of latent heat of fusion of a phase change material (PCM), in addition to sensible heat, significantly increases the energy density, thus potentially reducing the storage size and cost. However, a major technical barrier to the use of latent thermal energy of PCM is the high thermal resistance to energy transfer due to the intrinsically low thermal conductivity of PCMs, which is a particularly acute constraint during the energy discharge. Secondly, for integration of TES in CSP plants, it is imperative that the cyclic exergetic efficiency be high, among other requirements, to ensure that the energy extracted from the system is at the maximum possible temperature to achieve higher cycle conversion efficiency in the power block. The first objective is addressed through computational modeling and simulation to quantify the effectiveness of two different approaches to reduce the thermal resistance of PCM in a LTES, viz. (a) developing innovative, inexpensive and passive heat transfer devices that efficiently transfer large amount of energy between the PCM and heat transfer fluid (HTF) and (b) increase the heat transfer area of interaction between the HTF and PCM by incorporating the PCM mixture in small capsules using suitable encapsulation techniques.   The second portion of the research focuses on numerical modeling of large scale latent thermal storage systems integrated to a CSP plant with the aforementioned enhancement techniques and cascaded with more than one PCM to maximize the exergetic efficiency. Based on systematic parametric analysis on the various performance metrics of the two types of LTES, feasible operating regimes and design parameters are identified to meet the U.S. Department of Energy SunShot Initiative requirements including storage cost < $15/kWht and exergetic efficiency > 95%, for a minimum storage capacity of 14 h, in order to reduce subsidy-free levelized cost of electricity (LCE) of CSP plants from 21¢/kWh (2010 baseline) to 6¢/kWh, to be on par with the LCE associated with fossil fuel plants. / Ph. D.

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Increasing storage for energy is one of the most important challenges today to overcome in order to enable higher penetration of renewable energy in the existing energy systems. Thermal storage is one category of energy storage that has been successfully demonstrated in a number of engineering projects and is showing promising potential in the future. However, a technology cannot be widespread if it is not economically feasible and sustainable in the long run. Bottom up cost analysis can be used to assess economic viability of a technology. For newer technologies, the top-down cost calculation is not always possible due to the limited amount of data. The aim of this thesis is to investigate the best practices in performing bottom up cost calculation and to propose a methodology with the purpose of enabling it to be implemented over thermal energy storage bottom up economic evaluations. To achieve this, two proven applications, molten salt storage for concentrated solar power and ice thermal storage for building cooling, were examined as the basis of the bottom up state of the art calculation models. It was found that in the ice storage case, the models were often done in a hybrid bottom up-top down approach which limits a fully detailed cost analysis. Instead these are referred as case studies instead because of the few elements needed in their calculation. The constructed specialized models and case studies are then compared against other external sources to validate the proposed economic analysis procedure. The numerical results showed some discrepancies when compared to external resources. A compilation of a general bottom up cost model with detailed step by step model to perform a bottom up calculation for thermal storages is finally proposed in this work. / Att förbättra möjligheterna att lagra energi är en av dagens viktigaste utmaningar för att kunna öka andelen förnybar energi i vårt energisystem. Termisk energilagring eller värmelagring är en typ av energilagring som använts framgångsrikt i flera områden och visar hög potential i ett flertal ytterligare teknologier. En teknologi kan dock inte få en omfattande påverkan om den inte är ekonomiskt hållbar. En bottom-up kostnadsanalys kan användas för att uppskatta genomförbarheten för teknologin. För nya teknologier är en top-down kostnadsanalys inte alltid möjlig, vilket är beroende på den begränsade tillgången till data. Syftet med den här uppsatsen är att undersöka de vanligaste tillvägagångssätten i att utföra en bottom-up kostnadsanalys och föreslå en metodologi som har ändamålet att användas i bottom-up kostnadsanalyser för värmelagringstekniker. För att uppnå detta har två beprövade tekniker, smält saltlagring i koncentrerad solkraft och islagring för kylning av byggnader, undersökts som modeller för moderna bottom-up kostnadsanalyser. Efter undersökning fann man att i islagringsteknologi genomförs kostnadsanalysen vanligen i ett hybrid bottom up-top down upplägg, vilket begränsar möjligheten att rekonstruera en fullt detaljerad bottom-up kostnadsanalys. Dessa kommer istället att refereras som fallstudier eftersom endast ett fåtal objekt behövdes i en kostnadsberäkning. Specialiserade kostnadsmodeller som konstruerats och fallstudier jämförs med externa källor för att bekräfta den föreslagna analysproceduren för kostnadsberäkningar. Jämförelsen med externa källor visade viss spridning i numeriska resultat. En sammanställning av en generell bottom-up kostnadsmodell med detaljerad steg för steg-beskrivning för att genomföra en bottom-up kostnadsanalys är dessutom föreslagen i detta arbete.

月あるいは火星近傍における持続可能な宇宙空間利用のために、月面および火星表層を覆う複合酸化物から成るレゴリスを資源としたその場資源利用に関する技術の発展が不可欠である。本研究では、不揮発不燃性の溶融塩を反応媒体に用い、電気化学プロセシングにより、その場資源であるレゴリスに含まれる有用な元素の分離・回収・利用する技術を新たに提案した。また、溶融ハライド塩中での各種金属元素やイオン及びその酸化物等の物理化学特性を明らかにした。 / High temperature molten salt plays a key role in power generation systems such as solar cells, nuclear fission reactor, and nuclear fusion reactor on the moon and Mars. In this thesis, the physicochemical phenomena of metallic atoms, metallic ions, and its oxides in molten halides were investigated in order to obtain fundamental knowledges for electrochemical/materials science and to develop electrochemical processing in molten salt for in-situ resource utilization. The significant effects of melt structure, melt composition, and interfacial flow phenomena on the Si electrodeposition process was discussed. The corrosion behavior of major alloys and a unique steel in molten halides was also discussed. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University

In Hinblick auf den stetig steigenden Bedarf der chemischen Industrie an Grundstoffchemikalien und der teilweise unsicheren Versorgung mit Erdöl und Erdgas ist es notwendig alternative Rohstoffe und Verwertungspfade für die Bereitstellung von Basischemikalien zu finden. Ziel der vorliegenden Arbeit war die Untersuchung der Hydrogenolyse von Lignin in niedermolekulare Produkte unter Verwendung geeigneter Salzschmelzen. Es konnte gezeigt werden, dass Lignin in Zinkchlorid/Kaliumchloridschmelzen in niedermolekulare Produkte abgebaut werden kann. Hierbei erwiesen sich der Einsatz eines entsprechenden Eutektikums und einer Alternativschmelze mit niedrigem Schmelzpunkt als hilfreich. Durch den Einsatz verschiedener Apparaturen wurden Untersuchungen in statischer und dynamischer Atmosphäre durchgeführt. Es ergaben sich während der Untersuchung Abhängigkeiten der Hydrogenolyse von verschiedenen Reaktionsparametern. Optima der Umsetzung hinsichtlich der Reaktionsparameter Temperatur, Zeit und Ligninanteil in der Schmelze wurden herausgearbeitet. Die Ausbeute an gewünschten Flüssigprodukten wurde, im Untersuchungsbereich, an diesen Punkten maximiert. Gleichzeitig war die Rückstands- und Gasbildung eingeschränkt. Es konnten Erkenntnisse eines komplexen Systems der Abhängigkeiten der Ausbeuten an Reaktionsprodukten von den Parametern der Untersuchung gewonnen werden. Die Hydrogenolyse von Lignin führte zur Aromatisierung fester Residuen sowie zur Abreicherung von Sauerstofffunktionalitäten. Komplexe Reaktionsmechanismen bewirkten den Abbau von Methoxyl-, Carboxyl- und Hydroxylgruppen der Ligninstruktur. Carbeniumionmechanismen konnten als wichtige Reaktionen zur Spaltung von Ether Arylbindungen identifiziert werden. Die Freisetzung von Monomeren und die Polymerisation anderer Intermediäre sind durch Sekundärreaktionen denkbar. Die gebildeten Flüssigprodukte bestanden hauptsächlich aus Monoaromaten (v.a. Guajakole und Kresole) und wenigen Polyaromaten. Die Selektivität der Bildung einzelner Verbindungen war gering, d.h. die Flüssigprodukte sind eine heterogene Mischung mit geringen Konzentrationen der Einzelsubstanzen. Die Unterschiede in der Struktur der Ausgangslignine bildeten sich auch in der Zusammensetzung der Flüssigprodukte ab. / In view of the steadily increasing demand of the chemical industry to base chemicals and the partial uncertain supply of crude oil and gas, it is necessary to find alternative raw materials and conversion routes for the provision of basic chemicals. The aim of the present work was to investigate the hydrogenolysis of lignin in low molecular weight products using appropriate molten salt media. It could be demonstrated that lignin can be convert in low molecular weight products using zinc chloride/potassium chloride molten salt media. The use of an appropriate eutectic melt and of an alternative melt with low melting point proved helpful. By the use of different apparatus investigations in static and dynamic atmosphere could be carried out. During the investigation dependencies of the hydrogenolysis of various reaction parameters are submitted. Optima of the hydrogenolysis regarding to reaction temperature, time and lignin content at the melt could be identified. The yields were maximized at these points in the range of investigation. Concurrently formation of gases and residues were suppressed. Some evidence of a complex system of the dependencies of the yields of reaction products are obtained from the parameters of the investigation. Hydrogenolysis of lignin leads to aromatic solid residues and to a loss of oxygen containing structures. Structures containing methoxyl-, carboxyl- and hydroxyl groups are degraded by various complex reaction mechanisms. Mechanisms of the formation of carbonium ions were identified as important reactions of the cleavage of ether aryl bonds. Secondary reactions caused the liberation of monomers and polymerisation of some intermediaries. The resulting liquid products consist mainly of monoaromatics (guaiacols and cresols) and less of polyaromatics. The selectivity of the formation of single compounds was low, i.e. the liquid products constitute a heterogenous mixture with low concentrations of the single compounds. The structural differencies of the feedstock lignins also showed at the composition of the liquid products.

Molten Salt Fast Reactors (MSFRs) have prominent advantages such as fuel breeding, nuclear waste transmutation, and inherent safety. They are the only liquid-fueled nuclear reactors currently receiving significant attention as fourth-generation advanced nuclear systems. To address the challenges of short operational lifetimes and proliferation issues during online fuel processing, the breed-and-burn (B&amp;B) MSFR is among the most promising advanced reactor types. In this study, a large-volume B&amp;B MSFR model without online actinide element treatment was simulated and analyzed using the Monte Carlo simulation software SERPENT, considering different power levels and sizes of the inactive core. The results demonstrate that, under otherwise identical conditions, the operational lifetime and conversion ratio of MSFRs increase with decreasing power levels and increasing the size of the inactive core. These findings provide a foundation and theoretical basis for achieving B&amp;B MSFRs without online actinide element treatment. / Smält saltsnabbreaktorer (MSFRs) har framträdande fördelar såsom bränsleförädling, transmutation av kärnavfall och inneboende säkerhet. De är de enda flytande drivna kärnreaktorerna som för närvarande får betydande uppmärksamhet som fjärde generationens avancerade kärnkraftverk. För att möta utmaningarna med korta driftstider och spridningsproblem vid online bränslebearbetning är rask-och-bränning (B&amp;B) MSFR bland de mest lovande avancerade reaktortyperna. I denna studie simulerades och analyserades en storskalig B&amp;B MSFR-modell utan behandling av aktinidelement online med hjälp av Monte Carlo simuleringsprogramvaran SERPENT, med hänsyn till olika effektnivåer och storlekar på den inaktiva kärnan. Resultaten visar att livslängden och konverteringsförhållandet för MSFRs ökar under annars identiska förhållanden i takt med att effektnivåerna minskar och storleken på den inaktiva kärnan ökar. Dessa resultat ger en grund och teoretisk grund för att uppnå B&amp;B MSFRs utan behandling av aktinidelement online.

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No description available.

This work primarily centers on measuring the physical properties of molten salts. It's dedicated to outlining the methodology, enhancing measurement methods, and scrutinizing data to uncover insights regarding the interaction between molten salt and solid structures in the context of designing and generating electrical energy in molten salt reactors. The initial phase of this research involved collaborating with Brigham Young University's molecular dynamics simulation group to create an Archimedean density measurement device. This endeavor was primarily geared towards generating empirical data for the purpose of enhancing molecular dynamics simulation data. The tasks encompassed designing and validating the experimental setup, with a particular focus on measuring the densities of a novel salt composition--FMgNaK, a prospective nuclear fuel salt fuel/coolant. In the next chapter, we delve into the development, validation, and significant improvement of the rotational Couette viscosity measurement method at high temperatures. Originally designed for room temperature conditions, the methodology failed to account for the substantial temperature difference between the calibration fluids and the molten salts. Consequently, we introduce a theory aimed at correcting errors stemming from the thermal expansion of the solid container material during the transition from calibration to high temperature fluid measurement. As part of this comprehensive discussion, we also present the correction applied during the validation testing of the viscosity setup, with a specific focus on a nitrate salt known as solar salt. The final experiment development centered on the creation and validation of the Axisymmetric Drop-Shape Analysis (ADSA) method for use with molten salt. However, working with a specific nitrate salt, known as solar salt, posed challenges due to its propensity to wet all common high temperature substrates. This high degree of wetting posed hindrances to several physical properties measurements. Therefore, the primary objective of this work was to identify a non-wetting substrate to enhance the accuracy of ADSA and other measurement methods. Within this context, we present the results of surface tension and contact angle measurements, which were derived from the ADSA method, and the development of a non-wetting substrate for use with solar salt. In the final stage of this research, the ADSA method was applied to FLiBe, a critical fluoride salt in molten salt nuclear reactor design, and tellurium-bearing FLiBe to examine its interaction with boron nitride, a key solid porous material used in reactor vessel structures. Surface tension and contact angle measurements were conducted on various substrates, revealing the influence of oxygen on boron nitride wetting. Additionally, the study confirmed that tellurium, despite its chemical similarity to oxygen, did not significantly affect surface tension or contact angle, ruling out a substantial impact on boron nitride infiltration. The chapter also presents comprehensive data on the surface tension and densities of FLiBe, FLiNaK, and the chloride salt NaCl-KCl.

Neste trabalho tivemos como objetivo sintetizar e caracterizar os ortossilicatos de elementos alcalino-terrosos com destaque para o Sr2SiO4, uma matriz hospedeira para íons dopantes como o cádmio II e o európio III, resultando em materiais com propriedades luminescentes. Outro objetivo é reduzir a temperatura de síntese pelos métodos aqui empregados em relação aos métodos convencionais descritos na literatura. Tanto a matriz quanto os sistemas dopados foram caracterizados por meio da difratometria de raios x, análise de área superficial e tamanho de poros, microscopia eletrônica de varredura e de transmissão. Os métodos empregados neste trabalho foram basicamente o da metátese e o do sal fundido, sendo que o método da metátese foi conduzido por sol-gel (utilizando-se sílica comercial e TEOS) e por precipitação em atmosfera ambiente e em atmosfera de nitrogênio. Já no método do sal fundido utilizamos duas temperaturas de síntese, 600 e 750ºC. A 750ºC foi utilizada uma mistura equimolar de cloreto de sódio e cloreto de potássio juntamente com nitrato de estrôncio e sílica mesoestruturada na proporção molar de 2:1. A 600ºC foi utilizada somente a mistura de nitrato de estrôncio e sílica mesoestruturada também na proporção molar de 2:1. Nestas duas formas de se conduzir a síntese por sal fundido utilizamos nitrato de sódio (proporção molar de Na/Si = 0,1) a fim de se facilitar a quebra das pontes de oxigênio da sílica e verificar a influência desse reagente sobre o produto final. Já o Ca2SiO4 e o Ba2SiO4 foram sintetizados apenas a 600ºC bem como as dopagens do Sr2SiO4 (1% em mol). Os resultados mostram uma densificação do produto em relação à sílica e a obtenção de nanofibras de silicatos obtidos pelo método do sal fundido. Já no método da metátese obtivemos carbonato de estrôncio e outros tipos de silicatos. / In this work our objective was to synthesize and characterize orthosilicates of alkaline-earth elements with emphasis on Sr2SiO4. This is a silicate host matrix for doping with ions such as cadmium II and europium III, resulting in materials with luminescent properties. Another objective is to reduce the synthesis temperature using the methods employed here when compared to conventional methods described the literature. Both the matrix and the doped systems were well characterized by X-ray diffraction, surface area and pore size distribution, scanning and transmission electron microscopy. The methods employed in this study were basically the metathesis and the molten salt; the metathesis method was conducted by sol-gel (using a commercial silica and tetraethyl orthosilicate TEOS) and precipitation in air and nitrogen atmospheres. In the molten salt method, two synthesis temperatures were used: 600 and 750ºC. At 750°C an equimolar mixture of sodium chloride and potassium chloride with strontium nitrate was used in addition to mesostructured silica in the molar ratio of 2:1. At 600°C only a mixture of strontium nitrate and mesostructured silica was used, also in the molar ratio of 2:1. In these two pathways, sodium nitrate (molar ratio Na/Si = 0.1) was used in order to facilitate the breakup of the silica oxygen bridges and its influence on the final product was also studied. Furthermore, Ca2SiO4 and Ba2SiO4 were synthesized only at 600ºC and the doping of Sr2SiO4 (1 mol %) was also carried out only at 600°C. The results show a densification of the product compared to the silica precursor and the formation of silicate nanofibers by the molten salt method. In the metathesis method we obtained strontium carbonate and other types of silicates.