Cold thermal energy storage (CTES) for LNG energy systems

La demanda global en refrigeració en aplicacions residencials, comercials i industrials representa avui en dia una porció considerable de l’energia final consumida i del CO₂ emès. Tot i així, algunes fonts de fred d’alt grau, com el fred que s’allibera durant el procés de regasificació del gas natural liquat (GNL), és enviat a l’atmosfera sense treure’n cap profit. Aquesta tesi doctoral està enfocada en l’estudi i desenvolupament de tecnologies d’emmagatzemament de fred (CTES, per les sigles en anglès) aplicades a la regasificació de GNL. A través d’una exhaustiva revisió de la literatura publicada fins al moment en aquest camp, s’ha identificat una manca de comprensió en el procés de disseny i construcció d’unitats per CTES, així com tècniques adequades per millorar el coeficient de transferència de calor i d’algun tipus d’eina d’anàlisi quantitatiu respecte a la possible contribució dels sistemes CTES en estacions regasificadores de GNL. En conseqüència, aquesta tesi consta de 3 parts principals: 1) desenvolupament d’un metode comprensiu de disseny de sistemes CTES; 2) aplicació d’aquest mètode de disseny a un sistema de regasificació de GNL; 3) desenvolupament d’una tècnica de millora del coeficient de transferència de calor en sistemes CTES. Mitjançant la integració de mètodes multi-criteri de millora del material i amb una eficient optimització de la geometria del prototip, el nou mètode de disseny ha demostrat ser ràpid i fiable pel disseny preliminar de sistemes CTES basats en el concepte d’intercanviador de carcassa i tubs. Aquest mètode ha permès dissenyar un sistema integrat basat en un cicle orgànic de Rankine (ORC) que extreu la calor d’una font geotèrmica d’una explotació petroliera abandonada, i el fred d’una estació-satèl·lit de GNL. Un cop equipat amb el sistema CTES, l'ORC incrementa la seva eficiència en més d’un 30% i la capacitat de producció en un 25%. Per a la millora del coeficient de transferència de calor s’ha dissenyat un sistema que utilitza làmines de grafit. Per a mesurar la conductivitat efectiva del sistema s’ha desenvolupat un mètode ràpid i precís, basat en optimització numèrica, experimental i Bayesiana, els resultats del qual han demostrat que les làmines de grafit incrementen la conductivitat tèrmica efectiva en un 20% i redueixen l’efecte del subcooling.La demanda global en refrigeración en aplicaciones residenciales, comerciales y industriales representa hoy en dia una parte considerable de la energía final consumida y de las emisiones de CO2. Aún así, algunas fuentes de frío de alto grado, como el frío que se libera durante la regasificación del gas natural licuado (GNL), es enviado a la atmósfera sin ser usado. Esta tesis doctoral está enfocada en el estudio y desarrollo de tecnologías de almacenamiento de frio (CTES, por sus siglas en ingles) aplicadas a la regasificación del GNL. A través de una exhaustiva revisión de la literatura publicada hasta el momento, se ha identificado una falta de comprensión en el proceso de diseño y construcción de unidades para CTES, asi como técnicas adecuadas para mejorar el coeficiente de transferencia de calor, y de algún tipo de herramienta de análisis cuantitativo respecto a la posible contribución de los sistemas CTES en estaciones regasificadoras de GNL. En consecuencia, esta tesis consta de 3 partes: 1) desarrollo de un método comprensivo de diseño de sistemas CTES; 2) aplicación de este método de diseño a un sistema de regasificación de GNL; 3) desarrollo de una técnica de mejora del coeficiente de transferencia de calor en sistemas CTES. A través de la integración de métodos multi-criterio de mejora del material, y mediante una eficiente optimización de la geometría del prototipo, este nuevo método ha demostrado ser rápido y fiable en el diseño preliminar de sistemas CTES basados en el concepto de intercambiador de carcasa y tubos. Este método ha permitido diseñar un sistema integrado basado en un ciclo orgánico de Rankine (ORC) que extrae el calor de una fuente geotérmica de una explotación petrolera abandonada, y el frío de una estación satélite de GNL. Una vez equipado con el sistema CTES, el ORC incrementa su eficiencia en más de un 30% y en un 25% la capacidad de producción. Para la mejora del coeficiente de transferencia de calor se ha diseñado un sistema que utiliza láminas de grafito. Para la medida de la conductividad térmica efectiva del sistema se ha desarrollado un método rápido y preciso, basado en optimización numérica, experimental y Bayesiana, los resultados de la cual han demostrado que las laminas de grafito incrementan la conductividad térmica efectiva en un 20% mientras reducen el efecto del subcooling.The global demand for cold energy for residential, commercial, and industrial applications accounts for a considerable portion of final energy consumption and carbon emissions. However, some high-grade cold energy sources, such as the cold energy released during the regasification process of liquefied natural gas (LNG), are generally wasted. This thesis focuses on developing cold thermal energy storage (CTES) technologies for LNG energy systems. Through a comprehensive literature review, we identified the lack of comprehensively designed and built CTES units for LNG cold energy utilization, proper heat transfer enhancement techniques, and quantitative analysis of the contribution of CTES in LNG energy systems. Therefore, this thesis mainly contains three parts: 1) the development of a comprehensive CTES design method, 2) application of the design method in the designing of an LNG energy system, and 3) development of a heat transfer enhancement technique for CTES units. These investigations make use of experimental, numerical, and optimization methodologies. By integrating multi-criteria material assessment with efficient geometry optimization, the design method was shown to be fast and reliable for the preliminary design of latent heat shell-and-tube CTES units. Using the design method, we designed an integrated organic Rankine cycle (ORC) system that uses the low-grade geothermal energy from an abandoned exploitation well and the waste cold energy from a satellite LNG station. When equipped with the CTES, the ORC efficiency and net power production rose by more than 30% and 25%, respectively. A graphite sheet-based macrofiller was designed to enhance the heat transfer. To measure its effective thermal conductivity (keff), a numerical, experimental, and Bayesian optimization-based method was developed. The method was proved to be fast and accurate, and the macrofiller design increased the keff by around 20% and suppressed subcooling

Influence of friction variability on isolation performance of a rolling-damper isolation system

Previously, many isolation systems with friction action are designed ignoring the variability of friction coefficient. By taking a rolling-damper isolation system as the study object, this paper analyzed the effects of non-uniform distribution of rolling friction coefficient on its isolation performance through a compiled computer program. The results show that the errors associated with the maximum structural relative displacement, acceleration and residual displacement due to ignoring the friction variability are sequentially growing, and this rule is weakened by the damper. Under the condition of large friction variability and little damper action, the calculation of the maximum structural relative displacement and acceleration should consider the friction variability. When the structural residual displacement is concerned, the variability of rolling friction coefficient should be fully considered regardless of friction variability degree

Mitogen-activated protein kinase and method of use to enhance biotic and abiotic stress tolerance in plants

The present invention relates to the mitogen-activated protein kinase called MAPK5. The rice MAPK5 gene, its protein and kinase activity were induced by abscisic acid, pathogen infection, wounding, drought, salt and cold temperature. However, suppression of MAPK5 expression and kinase activity in dsRNAi transgenic plants resulted in constitutive expression of pathogenesis-related genes such as PR-1 and PR-10 but enhanced resistance to fungal and bacterial pathogens. In contrast, overexpressed transgenic lines exhibited elevated MAPK5 kinase activity and increased tolerance to drought, salt and cold stresses. This invention also provides methods for increasing tolerance to abiotic and biotic stress in plant using MAPK5

Moving Risk of Crowds in the Entrance Confluence Area in the Presence of Channelizing Facilities

In recent years, the measures to interfere the crowds movement with physical facilities (such as channelizing, separation railing) have become more and more common, but how they affect the crowd movement and what moving risks exist in the entrance confluence area have not been fully revealed. Therefore, this paper analyzes the moving risk of the crowds before the bottleneck entrance area, in the presence of the channelizing barriers by controllable laboratory experiments. The visual color cloud charts of the local density, speed and confusion degree of moving directions within the entrance confluence area are analyzed in the presence of different gaps (1.05m and 0.7m) channelizing barriers, to further quantify the motion risk of the crowds. The study finds that the narrower gaps of the channelizing railings, the larger area of high-risk zones, and they have clear ‘lane formation’ effect in shaping the risk zones. The both ends of the channelizing barriers are higher moving risk zones for multi-entry sides conditions, but the area before the middle channels also needs to be closely concerned when the participants entering from two opposite entering sides. The study will provide theoretical basis for evaluating the safety of the setting conditions of the channelizing barriers and conducting scientific crowd management decisions

Influence of friction variability on isolation performance of a rolling-damper isolation system

Previously, many isolation systems with friction action are designed ignoring the variability of friction coefficient. By taking a rolling-damper isolation system as the study object, this paper analyzed the effects of non-uniform distribution of rolling friction coefficient on its isolation performance through a compiled computer program. The results show that the errors associated with the maximum structural relative displacement, acceleration and residual displacement due to ignoring the friction variability are sequentially growing, and this rule is weakened by the damper. Under the condition of large friction variability and little damper action, the calculation of the maximum structural relative displacement and acceleration should consider the friction variability. When the structural residual displacement is concerned, the variability of rolling friction coefficient should be fully considered regardless of friction variability degree

In-plane ferroelectric tunnel junctions based on 2D α-In\u3csub\u3e2\u3c/sub\u3eSe\u3csub\u3e3\u3c/sub\u3e/ semiconductor heterostructures

Ferroelectric tunnel junctions (FTJs) have great potential for application in high-density non-volatile memories. Recently, α-In2Se3 was found to exhibit robust in-plane and out-of-plane ferroelectric polarizations at a monolayer thickness, which is ideal to serve as a ferroelectric component in miniaturized electronic devices. In this work, we design two-dimensional van der Waals heterostructures composed of an α-In2Se3 ferroelectric and a hexagonal IV–VI semiconductor and propose an in-plane FTJ based on these heterostructures. Our first-principles calculations show that the electronic band structure of the designed heterostructures can be switched between insulating and metallic states by ferroelectric polarization. We demonstrate that the in-plane FTJ exhibits two distinct transport regimes, tunneling and metallic, for OFF and ON states, respectively, leading to a giant tunneling electroresistance effect with the OFF/ON resistance ratio exceeding 1 × 104. Our results provide a promising approach for the highdensity ferroelectric memory based on the 2D ferroelectric/semiconductor heterostructures

Shell-and-tube latent heat thermal energy storage design methodology with material selection, storage performance evaluation, and cost minimization

Shell-and-tube latent heat thermal energy storage units employ phase change materials to store and release heat at a nearly constant temperature, deliver high effectiveness of heat transfer, as well as high charging/discharging power. Even though many studies have investigated the material formulation, heat transfer through simulation, and experimental studies, there is limited research dedicated to the storage unit design methodology. This study proposes a comprehensive methodology that includes the material assessment with multi-attribute decision-making and multi-objective decision-making tools, epsilon-NTU method, and cost minimization using Genetic Algorithm. The methodology is validated by a series of experimental results, and implemented in the optimization of a storage unit for solar absorption chiller application. A unit cost of as low as USD 8396 per unit is reported with a power of 1.42 kW. The methodology proves to be an efficient, reliable, and systematic tool to fulfill the preliminary design of shell-and-tube LHTES before the computational fluid dynamics or detailed experimental studies are engaged.This research was funded by SJ-NTU Corporate Lab. This research was partially funded by the Ministerio de Ciencia Innovación y Universidades de España (RTI2018-093849-B-C31—MCIU/AEI/FEDER, UE), and the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI) (RED2018- 102431-T). This work is partially supported by ICREA under the ICREA Academia programme

Economic freedom, inclusive growth, and financial development : a heterogeneous panel analysis of developing countries

The effective and efficient management of financial systems and resources fosters a socioeconomic climate conducive to technological and innovative advancement, thereby fostering long-term economic growth. The study used panel data from 72 countries classified as less financially developed between 2009 and 2017 to examine the role of economic freedom and inclusive growth in financial development. For the long-run estimations, we utilised the linear dynamic panel GMM-IV estimator, panel corrected standard errors (PCSE) linear regression method, and contemporaneous correlation estimator, a generalised least squares method. Our analyses indicate that economic liberty, inclusive growth, and capital stock significantly contribute to financial development in a positive manner. Moreover, inclusive growth contributes positively to overall financial development by enhancing economic freedom. Regardless of exogenous and endogenous shocks, we found that the tax burden and investment freedom are negative drivers of financial development as measured by the overall financial development index. In contrast, protection of property rights, government spending, monetary freedom, and financial freedom are positive and significant drivers of economic growth