Dissertations / Theses: 'Variable-Temperature Thermal Energy Storage'

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Oliver, David Elliot. "Phase-change materials for thermal energy storage." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/17910.

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There is a current requirement for technologies that store heat for both domestic and industrial applications. Phase-change materials (PCMs) represent an important class of materials that offer potential for heat storage. Heat-storage systems are required to undergo multiple melt/freeze cycles without any change in melting-crystallisation point and heat output. Salt hydrates are attractive candidates on account of their high energy densities, but there are issues associated with potential crystallisation of lower-hydrates, long-term stability, and reliable nucleation. An extensive review of the PCMs in the literature, combined with an evaluation of commercially available PCMs led to the conclusion that many of the reported PCMs, lack at least one of the key requirements required for use as a heat-storage medium. The focus of this research was therefore to identify and characterise new PCM compositions with tailored properties. New PCM compositions based of sodium acetate trihydrate were developed, which showed improved properties through the use of selective polymers that retard the nucleation of undesirable anhydrous sodium acetate. Furthermore, the mechanism of nucleation of sodium acetate trihydrate by heterogeneous additives has been investigated using variable-temperature powder X-ray diffraction. This study showed that when anhydrous Na2HPO4 was introduced to molten sodium acetate trihydrate at 58°C the hydrogenphosphate salt is present as the dihydrate. On heating to temperatures in the range 75-90°C the dihydrate was observed to dehydrate to form anhydrous Na₂HPO4. This result explains the prior observation that the nucleator is deactivated on heating. The depression of melting point of sodium acetate trihydrate caused by the addition of lithium acetate dihydrate has also been investigated using differential scanning calorimetry and powder X-ray diffraction. It has been possible to tune the melting point of sodium acetate trihydrate thereby modifying its thermal properties. Studies of the nucleation of sodium thiosulfate pentahydrate, a potential PCM, led to the structural characterisation of six new hydrates using single crystal Xray diffraction. All of these hydrates can exist in samples with the pentahydrate composition at temperatures ranging from 20°C to 45°C. These hydrates are: α-Na₂S₂O₃·2H₂O, which formed during the melting of α-Na₂S₂O₃·5H₂O; two new pentahydrates, β-Na₂S₂O₃·5H₂O and γ-Na₂S₂O₃·5H₂O; Na₂S₂O₃·1.33 H₂O, β-Na₂S₂O₃·2H₂O and Na₂S₂O₃·3.67 H₂O, which formed during the melting of β- Na₂S₂O₃·5H₂O. Furthermore, new PCMs in the 75-90°C range were identified. The commercial impact and route to market of several of the PCMs are discussed in the final chapter.

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Hinke, Themba D. "Hot thermal storage in a variable power, renewable energy system." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/42645.

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Approved for public release; distribution is unlimited
This thesis outlines the design of a renewable energy heat generation system with thermal storage for DOD facilities. The DOD is seeking to implement an increased percentage of renewable energy systems at its facilities in order to improve energy security and reduce energy costs. The intermittent nature of renewable energy generation, however, presents a major challenge to full implementation. This shortfall can be overcome by targeted facility-scale energy storage that allows for increased use of renewable-only systems. Since a large percentage of the electric energy used in both residential and commercial facilities is for space and water heating, thermal storage is a viable solution. Presented in this thesis is a method for designing, analyzing, and sizing a facility-scale thermal storage system. The results demonstrate thermal storage is a more cost-effective option when compared to alternatives like battery storage. In addition to being cheaper, thermal storage systems are safer, more reliable, and have a longer life cycle.

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Boonyobhas, Rex A. "Control strategy: wind energy powered variable chiller with thermal ice storage." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44525.

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This study commissioned a variable speed chiller system powered by renewable energy with ice thermal storage. A control strategy was also developed that matched the chiller load to any available renewable power. These solutions will allow the Department of Defense to move away from the traditional, electrical-focused, energy storage methods such as batteries to targeted solutions for large energy uses, specifically cooling. This research required developing a SOFtware program to extract data from a micro-grid. In order to effectively use intermittent renewable power, the researcher created a control algorithm for operating the variable speed chiller, and used a monitoring system to match the load to the power production. The data demonstrated that wind energy at the Turbopropulsion Laboratory was intermittent and decreased from summer to fall. The study also created a model to simulate a three-blade vertical-axis wind turbine and compared the results to similar published data. The ANSYS CFX simulation results showed that the NACA0018 blade profile best matched the published result, and was thus selected for additional turbulence modeling. At speeds less than or equal to 10 m/s, the best turbulence for modeling the turbine was the shear stress transport model; at speeds greater than 10 m/s, standard k-epsilon provided the closer correlation.

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Gilpin, Matthew R. "High temperature latent heat thermal energy storage to augment solar thermal propulsion for microsatellites." Thesis, University of Southern California, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10160163.

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Solar thermal propulsion (STP) offers an unique combination of thrust and efficiency, providing greater total ΔV capability than chemical propulsion systems without the order of magnitude increase in total mission duration associated with electric propulsion. Despite an over 50 year development history, no STP spacecraft has flown to-date as both perceived and actual complexity have overshadowed the potential performance benefit in relation to conventional technologies. The trend in solar thermal research over the past two decades has been towards simplification and miniaturization to overcome this complexity barrier in an effort finally mount an in-flight test.

A review of micro-propulsion technologies recently conducted by the Air Force Research Laboratory (AFRL) has identified solar thermal propulsion as a promising configuration for microsatellite missions requiring a substantial Δ V and recommended further study. A STP system provides performance which cannot be matched by conventional propulsion technologies in the context of the proposed microsatellite ''inspector" requiring rapid delivery of greater than 1500 m/s ΔV. With this mission profile as the target, the development of an effective STP architecture goes beyond incremental improvements and enables a new class of microsatellite missions.

Here, it is proposed that a bi-modal solar thermal propulsion system on a microsatellite platform can provide a greater than 50% increase in Δ V vs. chemical systems while maintaining delivery times measured in days. The realization of a microsatellite scale bi-modal STP system requires the integration of multiple new technologies, and with the exception of high performance thermal energy storage, the long history of STP development has provided "ready" solutions.

For the target bi-modal STP microsatellite, sensible heat thermal energy storage is insufficient and the development of high temperature latent heat thermal energy storage is an enabling technology for the platform. The use of silicon and boron as high temperature latent heat thermal energy storage materials has been in the background of solar thermal research for decades without a substantial investigation. This is despite a broad agreement in the literature about the performance benefits obtainable from a latent heat mechanisms which provides a high energy storage density and quasi-isothermal heat release at high temperature.

In this work, an experimental approach was taken to uncover the practical concerns associated specifically with applying silicon as an energy storage material. A new solar furnace was built and characterized enabling the creation of molten silicon in the laboratory. These tests have demonstrated the basic feasibility of a molten silicon based thermal energy storage system and have highlighted asymmetric heat transfer as well as silicon expansion damage to be the primary engineering concerns for the technology. For cylindrical geometries, it has been shown that reduced fill factors can prevent damage to graphite walled silicon containers at the expense of decreased energy storage density.

Concurrent with experimental testing, a cooling model was written using the "enthalpy method" to calculate the phase change process and predict test section performance. Despite a simplistic phase change model, and experimentally demonstrated complexities of the freezing process, results coincided with experimental data. It is thus possible to capture essential system behaviors of a latent heat thermal energy storage system even with low fidelity freezing kinetics modeling allowing the use of standard tools to obtain reasonable results.

Finally, a technological road map is provided listing extant technological concerns and potential solutions. Improvements in container design and an increased understanding of convective coupling efficiency will ultimately enable both high temperature latent heat thermal energy storage and a new class of high performance bi-modal solar thermal spacecraft.

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Nath, Rupa. "Encapsulation of High Temperature Phase Change Materials for Thermal Energy Storage." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4180.

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Thermal energy storage is a major contributor to bridge the gap between energy demand (consumption) and energy production (supply) by concentrating solar power. The utilization of high latent heat storage capability of phase change materials is one of the keys to an efficient way to store thermal energy. However, some of the limitations of the existing technology are the high volumetric expansion and low thermal conductivity of phase change materials (PCMs), low energy density, low operation temperatures and high cost. The present work deals with encapsulated PCM system, which operates at temperatures above 500°C and takes advantage of the heat transfer modes at such high temperatures to overcome the aforementioned limitations of PCMs. Encapsulation with sodium silicate coating on preformed PCM pellets were investigated. A low cost, high temperature metal, carbon steel has been used as a capsule for PCMs with a melting point above 500° C. Sodium silicate and high temperature paints were used for oxidation protection of steel at high temperatures. The emissivity of the coatings to enhance heat transfer was investigated.

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Agyenim, Francis Boateng. "The development of medium temperature thermal energy storage for cooling applications." Thesis, University of Ulster, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436852.

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Wickramaratne, Chatura. "Experimental Study of High-Temperature Range Latent Heat Thermal Energy Storage." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7451.

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Among all thermal energy storage (TES) systems, latent heat thermal energy storage (LHTES) attracts high interest due to its high energy density and high exergetic efficiency. Due to the high enthalpy of fusion and low cost, inorganic salts are becoming popular as phase change materials and are used as the storage media in LHTES systems. The main drawbacks for the inorganic salts are their low thermal conductivity and high reactivity above 500°C. Therefore, designing a cost-effective containment at these conditions with longevity is a challenge. Macro-encapsulation of the PCM is one way to solve both the PCM containment issue as well as the low thermal conductivity problem. However, finding a practically viable encapsulation technique is a challenge especially for temperatures above 500°C. In the present study, encapsulation techniques were investigated for two temperature ranges; 500°C – 600°C and 600°C above. Metallic encapsulation was adopted for the 500°C – 600°C temperature. Commercially available, low-cost carbon-steel tubes were used, and the encapsulation shape was cylindrical. A 200µm coating of Ni was applied to strengthen the corrosion resistance. For temperatures above 600°C, a novel approach involving the use of ceramic materials was investigated for encapsulating chloride based PCMs. Low-cost ceramics with excellent thermal and chemical stability under molten-salt conditions were identified as the encapsulants. The influence of sintering temperature on the reactivity of feldspar, ball clay, kaolin and the mixture thereof with molten sodium chloride was investigated. The results were used to develop an optimum ceramic capsule fabrication procedure, using a green ceramic body followed by sintering at 1190°C. An innovative sealing process of in-situ layered eutectic formation was introduced. Sealing was performed at a temperature above the eutectic melting point of the salt mixture but below the individual melting points of each salt. The fabricated capsule survived more than 500 thermal cycles without showing degradation in its thermo-physical properties. Alumina (99%) based capsule containing NaCl-KCl was tested successfully for 1000 thermal cycles with a PCM weight loss of less than 5%. A lab-scale setup was designed and constructed to test an industry scalable LHTES system suitable for supplementing heat to a steam-powered cycle. Metallic cylindrical capsules were used with a eutectic of sodium sulfate (Na2SO4) and potassium chloride (KCl), which melts at 515°C, as the PCM for energy storage. This system was modeled and validated with experimental measurements. The calculated ratio of exergy to energy efficiency was around 89% (for 380-535°C). Flow irregularities were found due to a bend in the flow channel. Therefore, flow conditioners were investigated. A modified system with the flow conditioners and radiation shields showed 98% exergy to energy efficiency ratio (for 495-535°C). The overall efficiency of the system, however, was found to be low due to the heat losses from the storage tank. Finally, a novel design of a TES system using spherical capsules is proposed with additional enhancement gained from the experimental work on the lab-scale LHTES system. The innovation of this design lies in the manufacturing process to forms multiple spherical capsules using sheet metals. The adoptability of this technique for higher or lower temperature LHTES applications depends on the properties of the selected sheet metal. Any formable sheet metal can be used depending on the compatibility with PCM and HTF.

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Bhardwaj, Abhinav. "Metallic Encapsulation for High Temperature (>500 °C) Thermal Energy Storage Applications." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5843.

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Deployment of high temperature (>500 °C) thermal energy storage in solar power plants will make solar power more cost competitive and pave the way towards a sustainable future. In this research, a unique metallic encapsulation has been presented for thermal energy storage at high temperatures, capable of operation in aerobic conditions. This goal was achieved by employing low cost materials like carbon steel. The research work presents the unique encapsulation procedure adopted, as well as various coatings evaluated and optimized for corrosion protection. Experimental testing favored the use of 150 μm of nickel on carbon steel for corrosion protection in these conditions. These metallic encapsulations survived several thermal cycles at temperatures from 580 °C to 680 °C with one encapsulation surviving for 1700 thermal cycles.

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Augood, P. C. "Low-Temperature Thermal-Energy Storage and Transmission Systems Employing Hydrophilic Polymeric Materials." Thesis, Cranfield University, 1997. http://hdl.handle.net/1826/4517.

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The wide fluctuations that occur in the aggregate electrical demand of a generating utility are punitive with respect to total system efficiency. Demand side management techniques have been applied to reduce such fluctuations including the conversion of electrical energy to thermal energy during periods of low demand for use during peak demand periods. For thermal processes requiring energy above ambient temperature it is feasible to use sensible heat due to the existence of stable storage mediums and efficient methods of heating at the high temperatures required. However where energy is required below ambient temperatures, efficiency of cooling limits the use of sensible heat, hence latent heat storage has been adopted. Conventional cold storage systems use ice banks to store cooling energy at 0°C in order to capture the high latent heat of fusion of water. The rate of discharge for such stores is limited by thermal resistance in the store and the thermal capacity of secondary coolants (such as glycol solutions). This investigated the use of hydrophilic materials to overcome the limitations of current cold-storage technology. Such materials have the capacity to absorb and retain up to 95% by mass of water (or other aqueous solutions) regardless of how the materials is subdivided. Furthermore the thermal properties of the polymers in their hydrated state resemble those of the free hydration fluid, including any phase transitions. By supporting the hydrated materials in a non-freeing, non-aqueous fluid the resultant mixture provides a medium for cold storage that can be pumped and used at the point of load, and is not limited by the thermal resistance of an encapsulating material. Three aspects concerning the utilisation of hydrophilic materials for thermal engineering applications have been investigated; (i) the physical properties of the materials in their hydrated state, (ii) methods of fluidising material in a high density store, and (iii) the heat transfer properties of hydrophilic based slurries while undergoing phase transition. Material tests have shown that currently available hydrophilic materials have thermo- physical properties that depend principally upon the hydrating fluid, regardless of particle size, and are stable over long periods (>3years). Suitable hydration fluids can lower the temperature of the phase transition thus extending their potential as storage mediums beyond those of ice-based technologies. Novel materials, of very high water content (95%) have been produced and investigated. These appear to be very suitable for thermal storage because they increase the maximum achievable energy densities of a fluidised storage system and potentially reduce cost. A number of thermal storage devices to utilise hydrophilic based slurries have been designed and evaluated. The resultant devices has been shown to provide a means of taking hydrophilic materials to, and from, a packed bed and feeding them at a controlled rate into a fluid stream. The thermal charge/discharge rates of such a device are limited only by the choice of external heat exchange systems. An experimental apparatus has been designed to investigate the effects of phase change particles on the heat transfer properties of flowing mixtures. The results have shown that (i) at temperatures above the phase transition temperature the presence of the particles causes an increase in the measured heat transfer coefficient for concentrations above 10% by volume, (ii) there is a significant interaction of particles at the heat transfer surface, and (iii) that under high flow rate conditions, with phase change occurring, heat transfer coefficients are considerably enhanced (ie 80%) above those of the support fluid when used alone or with non-active particles. Further work is recommended to extend this study to produce an engineering prototype storage system for trial evaluation.

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Myska, Martin. "Possibilities with Stirling Engine and High Temperature Thermal Energy Storage in Multi-Energy Carrier System : An analysis of key factors influencing techno-economic perspective of Stirling engine and high-temperature thermal energy storage." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-53407.

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Small and medium-scale companies are trying to minimise their carbon footprint and improve their cash flow, renewable installations are increasing all over the Europe and are expected to do so in following years. However, their dependency on the weather cause pressure on matching the production with demand. An option how to challenge this problem is by using energy storage. The aim of this project is to determine techno-economic benefits of Stirling engine and high temperature thermal energy storage for installation in energy user system and identify key factors that affect the operation of such system. In order to determine these factors simulations in Matlab were conducted. The Matlab linear programming tool Optisolve using dual-simplex algorithm was used. The sensitivity analysis was conducted to test the energy system behaviour. Economic evaluation was done calculating discounted savings. From the results, it can be seen the significant benefit of SE-HT-TES installation is the increased self-consumption of the electricity from PV installation. While the self-consumption in cases when there was no energy storage implemented was around 67 % and in one case as low as 50 % with the SE-HT-TES the value has increased up to 100 %. Energy cost savings are 4.7 % of the cost for the original data set and go up to 6.2 % when simulation with load shift was executed. Simulations have also shown that energy customer with predictable energy demand pattern can achieve higher savings with the very same system. It was also confirmed that for users whose private renewable production does not match load potential savings are 30 % higher compared to the system where energy load peak is matching the PV production peak. Simulations also shown that the customers located in areas with higher electricity price volatility can benefit from such system greatly.

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Pitié, Frédéric. "High temperature thermal energy storage : encapsulated phase change material particles : determination of thermal and mechanical properties." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/57108/.

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Hesselbrandt, Max. "Performance Evaluation of a High Temperature Borehole Thermal Energy Storage Under Influence of Groundwater Flow." Thesis, KTH, Energiteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-293686.

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Recent years have seen a growing interest in large-scale high-temperature borehole thermal energy storage (HT-BTES) as a means to store industrial waste heat and solar energy between the seasons. A profound understanding and characterization of the thermal and hydraulic processes involved in such systems is required for the optimal design as well as for environmental assessments of the storage. In this work, the importance of groundwater flow effects on the thermal performance of HT-BTES has been studied. The current research status on groundwater flow and transport modeling techniques applied in the field of shallow geothermal energy as well as in other geosciences disciplines has been reviewed. A finite element heat conduction model of an existing HT-BTES located in dry heterogeneous soil has been developed and validated against operational and monitoring data. The heat conduction model provided a basis by which to compare the behaviour and performance of the storage under influence of ground waterflow. Numerical experiments were conducted considering both pure heat conduction as well as different scenarios accounting for groundwater flow. A performance evaluation study based on key performance indicators in terms of energy and exergy efficiencies has been carried out to quantify the impact of groundwater flow on the amount and quality of the heat being stored and exchanged. The analysis shows that the presence of groundwater flow is in general detrimental to the energy and exergy performance of the HT-BTES. The results indicate, however, that small groundwater flow rates also can have a slight positive effect on seasonal energy and exergy efficiencies as compared to case of pure conduction. Further studies are though needed where a wider range of time scales, BHE designs, operation conditions and subsurface conditions are adressed. From the inherent uncertainties associated with subsurface flow and transport processes it follows that general guidelines on how and under what conditions groundwater flow may have impact on BTES design and performance are difficult to provide. The characteristics of these processes in porous, and particularly fractured, media are often very site-specific and scale dependent, making it a challenging task to select and use an appropriate modeling approach that can capture all relevant features of the problem. To face this challenge, various modeling approaches, typically based on deterministic and stochastic continuum or discrete fracture network concepts, have been developed within the field of subsurface flow and transport modeling. To widen the modeling framework typically employed in shallow geothermal energy applications, their applicability also in the context of BTES modeling could be explored.
Intresset för säsongslagring av industriell överskottsvärme och solenergi genom högtemperaturborrhålslager(HT-BTES) har på senare år ökat. För att möjliggöra en optimal design av dessa system, samt för att bedöma deras inverkan på omgivande miljö, krävs djupgående förståelse och karaktärisering av de kopplade termiska och hydrauliska processer som påverkar lagret. I detta arbete har grundvattenflödets inverkan på högtemperaturlagers termiska prestanda behandlats. Nuvarande kunskapsläge inom modellering av grundvattenflödes- och transportprocesser i porösa och sprickiga medier har granskats, liksom dess användning inom geoenergi och andra geovetenskapliga områden. En värmeledningsmodell av ett befintligt HT-BTES i torr, heterogen jord har utvecklats genom finita elementmetoden och validerats mot mätdata. Värmeledningsmodellen tillämpades som referens för jämförelse med utökade modeller i vilka inverkan av grundvattenströmning beaktats genom koppladehydro-termiska beräkningar. En utvärdering av lagrets prestanda med avseende på nyckelindikatorer i formav energi- och exergiverkningsgrad har utförts för att kvantifiera inverkan av grundvattenflödet på mängden och kvaliteten av den värme som överförs och lagras genom borrhålslagret. Resultaten visar att förekomstenav grundvattenströmningar genom lagret generellt har en negativ inverkan på dess energi- ochexergiverkningsgrad. Däremot finns det i resultaten indikationer om att låga grundvattenflöden även kan bidra till en svagt positiv effekt jämfört med fallet med ren värmeledning. Vidare och mer omfattande studier bör dock utföras där längre tidsskalor samt en större uppsättning lagerdimensioner, driftscenarion, och markförhållanden beaktas. Till följd av att det kring strömnings- och transportprocesser i mark alltid råder inneboende osäkerheter är det svårt att upprätta generella riktlinjer kring hur och under vilka omständigheter ett grundvattenflöde kan ha inverkan på ett borrhålslagers design och prestanda. Typiskt för dessa processer i porösa och i synnerhet sprickiga medier är att de är mycket platsspecifika och skalberoende, vilket medför utmaningar vid valet av ett lämpligt modellkoncept för att beskriva dem med erfoderlig precision. Detta har lett till att ett stort antal modelleringskoncept har utvecklats och prövats för detta ändamål, vilka främst baseras på antaganden om deterministiska eller stokastiska kontinuum och diskreta spricknätverk. Tillämpbarheten av dessa modellkoncept även för modellering av HT-BTES bör undersökas och utvärderas för att möjliggöra analys av borrhålslager under inverkan av komplexa strömningsförhållanden.

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Rossi, Espagnet Alberto. "Techno-Economic Assessment of Thermal Energy Storage integration into Low Temperature District Heating Networks." Thesis, KTH, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191485.

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Thermal energy storage (TES) systems are technologies with the potential to enhance the efficiency and the flexibility of the coming 4th generation low temperature district heating (LTDH). Their integration would enable the creation of smarter, more efficient networks, benefiting both the utilities and the end consumers. This study aims at developing a comparative assessment of TES systems, both latent and sensible heat based. First, a techno-economic analysis of several TES systems is conducted to evaluate their suitability to be integrated into LTDH. Then, potential scenarios of TES integration are proposed and analysed in a case study of an active LTDH network. This is complemented with a review of current DH legislation focused on the Swedish case, with the aim of taking into consideration the present situation, and changes that may support some technologies over others. The results of the analysis show that sensible heat storage is still preferred to latent heat when coupled with LTDH: the cost per kWh stored is still 15% higher, at least, for latent heat in systems below 5MWh of storage size; though, they require just half of the volume. However, it is expected that the cost of latent heat storage systems will decline in the future, making them more competitive. From a system perspective, the introduction of TES systems into the network results in an increase in flexibility leading to lower heat production costs by load shifting. It is achieved by running the production units with lower marginal heat production costs for longer periods and with higher efficiency, and thus reducing the operating hours of the other more expensive operating units during peak load conditions. In the case study, savings in the magnitude of 0.5k EUR/year are achieved through this operational strategy, with an investment cost of 2k EUR to purchase a water tank. These results may also be extended to the case when heat generation is replaced by renewable, intermittent energy sources; thus increasing profits, reducing fuel consumption, and consequently emissions. This study represents a step forward in the development of a more efficient DH system through the integration of TES, which will play a crucial role in future smart energy system.
Thermal energy storage (TES) eller Termisk energilagring är en teknologi med potentialen att öka effektivitet och flexibilitet i den kommande fjärde generationens fjärrvärme (LTDH). Studien har som mål att kartlägga en komparativ uppskattning av TES systemen, baserad både på latent och sensibel värme. Resultaten visar att lagring av sensibel värme är att föredra före latent värme när den kopplas med LTDH: pris per lagrade kWh kvarstår som 15% högre än för latent värme i system under 5 MWh av lagringsutrymme; dock fordrar de endast hälften av volymen. Utifrån systemperspektiv innebär introduktionen av TES system i nätverket en ökning av flexibilitet vilket leder till reducerade värmeproduktionskostnaderna i mindre belastning. I fallstudien nås en sparnivå av femhundra euro per år genom denna operativa strategi, med en investering av 2000 euro för inköp av vattentank. Resultaten kan också vidgas till en situation där värmeproduktionen ersätts av förnybara, intermittenta energikällor; till detta medföljer högre vinster, lägre bruk av bränsle vilket skulle innebära lägre utsläpp. Studien kan ses som ett steg framåt mot skapandet av en mer effektiv DH system genom integrationen av TES, vilket kommer att spela en betydande roll i framtida smarta energisystem.

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Bruce, Robert Alasdair Wilson. "Impacts of variable renewable generation on thermal power plant operating regimes." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20387.

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The integration of variable renewable energy sources (VRE) is likely to cause fundamental and structural changes to the operation of future power systems. In the United Kingdom (UK), large amounts of price-insensitive and variable-output wind generation is expected to be deployed to contribute towards renewable energy and carbon dioxide (CO2) emission targets. Wind generation, with near-zero marginal costs, limited predictability, and a limited ability to provide upward dispatch, displaces price-setting thermal power plants, with higher marginal costs, changing flexibility and reserve requirements. New-build, commercial-scale, and low-carbon generation capacity, such as CO2 capture and storage (CCS) and nuclear, may impact power system flexibility and ramping capabilities. Low-carbon generation portfolios with price-sensitive thermal power plants and energy storage are therefore likely to be required to manage increased levels of variability and uncertainty at operational timescales. This work builds on a high-resolution wind reanalysis dataset of UK wind sites. The locations of existing and proposed wind farms are used to produce plausible and internally consistent wind deployment scenarios that represent the spatial distribution of future UK wind capacity. Temporally consistent electricity demand data is used to characterise and assess demand-wind variability and net demand ramp events. A unit commitment and economic dispatch (UCED) model is developed to evaluate the likely operating regimes of thermal power plants and CCS-equipped units across a range of future UK wind scenarios. Security constraints for reserve and power plant operating constraints, such as power output limits, ramp rates, minimum up/down times, and start-up times, ensure the operational feasibility of dispatch schedules. The load factors, time spent at different loads, and the ramping and start-up requirements of thermal power plants are assessed. CO2 duration curves are developed to assess the impacts of increasing wind capacity on the distribution of CO2 emissions. A sensitivity analysis investigates the impacts of part-load efficiency losses, ramp rates, minimum up/down times, and start-up/shut-down costs on power plant operating regimes and flexibility requirements. The interactions between a portfolio of energy storage units and flexible CO2 capture units are then explored. This multi-disciplinary research presents a temporally-explicit and detailed assessment of operational flexibility requirements at full 8760 hour resolution, highlighting the non-linear impacts of increasing wind capacity. The methodological framework presented here uses high spatial-and temporal-resolution wind data but is expected to provide useful insights for other VREbased power systems to mitigate the implications of inadequate flexibility.

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Sarvghad, Moghaddam Madjid. "Corrosion of structural alloys in molten salts for solar thermal energy storage." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/118056/1/Madjid_Sarvghad%20Moghaddam_Thesis.pdf.

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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.

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Aldubyan, Mohammad Hasan. "Thermo-Economic Study of Hybrid Photovoltaic-Thermal (PVT) Solar Collectors Combined with Borehole Thermal Energy Storage Systems." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1493243575479443.

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Hasib, A. M. M. Golam. "Effect of Dispersed Particles and Branching on the Performance of a Medium Temperature Thermal Energy Storage System." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc499995/.

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The main objective of my thesis is to develop a numerical model for small-scale thermal energy storage system and to see the effect of dispersing nano-particles and using fractal-like branching heat exchanger in phase change material for our proposed thermal energy storage system. The associated research problems investigated for phase change material (PCM) are the low thermal conductivity and low rate of heat transfer from heat transfer fluid to PCM in thermal energy storage system. In this study an intensive study is carried out to find the best material for thermal storage and later on as a high conductive nano-particle graphite is used to enhance the effective thermal conductivity of the mixed materials. As a thermal storage material molten solar Salt (60% NaNO3+40%KNO3) has been selected, after that detailed numerical modeling of the proposed design has been done using MATLAB algorithm and following the fixed grid enthalpy method. The model is based on the numerical computation of 1-D finite difference method using explicit scheme. The second part of the study is based on enhancing the heat transfer performance by introducing the concept of fractal network or branching heat exchanger. Results from the numerical computation have been utilized for the comparison between a conventional heating system (with a simple single tube as a heat exchanger) and a passive PCM thermal energy storage system with branching heat exchanger using NTU-effectiveness method and charging time calculation. The comparison results show a significant amount improvement using branching network and mixing nano-particle in terms of heat transfer (13.5% increase in effectiveness of branching level-02 heat exchangers from the conventional one ), thermal conductivity (increased 73.6% with 20% graphite nano-particle mix with solid PCM), charging time (57% decrease of charging time for the effect of both the dispersion of Graphite nano-particle and branching heat exchange) and pressure drop (36% decrease in level-02 branching). The results of this study prove that the proposed medium temperature TES system coupled with solar ORC can be the stepping-stone for energy efficient and sustainable future in small-scale/building level as the system proves to be better in terms of enhanced heat transfer, increased thermal conductivity and reduced pumping power and overall sustainability.

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18

Myers, Philip D. Jr. "Additives for Heat Transfer Enhancement in High Temperature Thermal Energy Storage Media: Selection and Characterization." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5749.

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Inorganic salts are very promising as high-temperature heat transfer fluids and thermal storage media in solar thermal power production. The dual-tank molten salt storage system, for example, has been demonstrated to be effective for continuous operation in solar power tower plants. In this particular storage regime, however, much of the thermal storage potential of the salts is ignored. Most inorganic salts are characterized by high heats of fusion, so their use as phase-change materials (PCMs) allows for substantially higher energy storage density than their use as sensible heat storage alone. For instance, use of molten sodium-potassium eutectic salt over a temperature range of 260 to 560°C (the approximate operating parameters of a proposed utility-scale storage system) allows for a volumetric energy storage density of 212 kWhth/m3, whereas the use of pure sodium nitrate (T_m = 307°C) over the same temperature range (utilizing both sensible and latent heat) yields a storage density of 347 kWhth/m3. The main downside to these media is their relatively low thermal conductivity (typically on the order of 1 W/m-K). While low conductivity is not as much an issue with heat transfer fluids, which, owing to convective heat transfer, are not as reliant on conduction as a heat transfer mode, it can become important for PCM storage strategies, in which transient charging behavior will necessarily involve heating the solid-phase material up to and through the process of melting. This investigation seeks to develop new methods of improving heat transfer in inorganic salt latent heat thermal energy storage (TES) media, such as sodium / potassium nitrates and chlorides. These methods include two basic strategies: first, inclusion of conductivity-enhancing additives, and second, incorporation of infrared absorptive additives in otherwise transparent media. Also, in the process, a group of chloride based salts for use as sensible storage media and/or heat transfer fluids has been developed, based on relevant cost and thermophysical properties data. For direct conductivity enhancement, the idea is simple: a PCM with low conductivity can be enhanced by incorporation of nanoparticulate additives at low concentration (~5 wt %). This concept has been explored extensively with lower temperature heat transfer fluids such as water, ethylene glycol, etc. (e.g., nanofluids), as well as with many lower temperature PCMs, such as paraffin wax. Extension of the concept to high temperature inorganic salt thermal storage media brings new challenges—most importantly, material compatibility. Also, maintenance of the additive distribution can be more difficult. Promising results were obtained in both these regards with nitrate salt systems. The second heat transfer enhancement strategy examined here is more novel in principle: increasing the infrared absorption of a semitransparent salt PCM (e.g., NaCl) with a suitable additive can theoretically enhance radiative heat transfer (for sufficiently high temperatures), thereby compensating for low thermal conductivity. Here again, material compatibility and maintenance of additive dispersion become the focus, but in very different ways, owing to the higher temperatures of application (>600°C) and the much lower concentration of additives required (~0.5 wt %). Promising results have been obtained in this case, as well, in terms of demonstrably greater infrared absorptance with inclusion of additives.

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19

Malmberg, Malin. "Transient modeling of a high temperature borehole thermal energy storage coupled with a combined heat and power plant." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226160.

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Coupling High-Temperature Borehole Thermal Energy Storages (HT-BTES) with existing Combined Heat and Power (CHP) systems is a promising approach to increase energy efficiency of district energy systems through recovery of otherwise wasted heat. This solution is currently being discussed in Sweden by the company Tekniska Verken in Linköping AB, for storing waste heat from their CHP operation in summer in a HT-BTES and to utilize it during peaks in winter. This would increase the flexibility between energy supply and demand in one of their plants. The available supply temperature during charge of the BTES is around 95C. There is, though, still limited experience of HT-BTES operation with just a few installations throughout the world. The aim of this Master´s thesis has been to evaluate a potential system design configuration for effective extraction and storage of waste heat from the Gärstadverket CHP-plants in connection to a HT-BTES. Data from previous operation of the CHP-plants and an existing TRNSYS model, developed at KTH and Bengt Dahlgren AB based on the well-known DST approach (Duct Ground Heat Storage Model), was used as a starting point to the development of a new, more complete model that includes a heat pump. The heat pump model was developed from manufacturer’s data for a non-standard 50 MW heat pump system using R717 as refrigerant. As an additional objective, design and operational experience of already existing HT-BTES installations has been compiled and analyzed. The BTES design were simulated with varied number of boreholes and borehole depth. The system was furthermore simulated with two different borehole heat exchangers (BHEs): double U-pipes and coaxial. Based on the results three optimized designs were found: 1 400 boreholes with double U-pipes and a borehole depth of 300 m, 1 300 boreholes with coaxial BHEs and a borehole depth of 300 m, and a design with 1 500 boreholes and 275 m borehole depth – all three designs with a borehole spacing of 5 m and with loops of 3 boreholes connected in series. The three BTES designs showed similar results with a potential to store around 107 GWh/year and to extract around 93 GWh/year with the use of a GSHP. The resulting discharge temperature from the BTES ranges between 40-60C, and up to 70C in the initial discharge period in the tenth simulation year. Further investigation is though needed regarding if there are any coaxial BHE available on the market that can work with the high temperatures in the BTES. Coupling High-Temperature Borehole Thermal Energy Storages (HT-BTES) with existing Combined Heat and Power (CHP) systems is a promising approach to increase energy efficiency of district energy systems through recovery of otherwise wasted heat. This solution is currently being discussed in Sweden by the company Tekniska Verken in Linköping AB, for storing waste heat from their CHP operation in summer in a HT-BTES and to utilize it during peaks in winter. This would increase the flexibility between energy supply and demand in one of their plants. The available supply temperature during charge of the BTES is around 95C. There is, though, still limited experience of HT-BTES operation with just a few installations throughout the world. The aim of this Master´s thesis has been to evaluate a potential system design configuration for effective extraction and storage of waste heat from the Gärstadverket CHP-plants in connection to a HT-BTES. Data from previous operation of the CHP-plants and an existing TRNSYS model, developed at KTH and Bengt Dahlgren AB based on the well-known DST approach (Duct Ground Heat Storage Model), was used as a starting point to the development of a new, more complete model that includes a heat pump. The heat pump model was developed from manufacturer’s data for a non-standard 50 MW heat pump system using R717 as refrigerant. As an additional objective, design and operational experience of already existing HT-BTES installations has been compiled and analyzed. The BTES design were simulated with varied number of boreholes and borehole depth. The system was furthermore simulated with two different borehole heat exchangers (BHEs): double U-pipes and coaxial. Based on the results three optimized designs were found: 1 400 boreholes with double U-pipes and a borehole depth of 300 m, 1 300 boreholes with coaxial BHEs and a borehole depth of 300 m, and a design with 1 500 boreholes and 275 m borehole depth – all three designs with a borehole spacing of 5 m and with loops of 3 boreholes connected in series. The three BTES designs showed similar results with a potential to store around 107 GWh/year and to extract around 93 GWh/year with the use of a GSHP. The resulting discharge temperature from the BTES ranges between 40-60C, and up to 70C in the initial discharge period in the tenth simulation year. Further investigation is though needed regarding if there are any coaxial BHE available on the market that can work with the high temperatures in the BTES.
Koppling av högtemperatur-borrhålslager (HT-BTES) med befintliga kraftvärmeverk (CHP) är ett lovande tillvägagångssätt för att öka energieffektiviteten i fjärrvärmesystem genom återvinning spillvärme. Denna lösning diskuteras för närvarande i Sverige av Tekniska Verken i Linköping AB, för att lagra spillvärme från kraftvärmeproduktion sommartid i en HT-BTES och utnyttja denna under effekttoppar på vintern. Detta skulle öka flexibiliteten mellan energiförsörjning och efterfrågan i en av deras anläggningar, Gärstadverket. Den tillgängliga framledningstemperaturen under laddning av borrhålslagret är ca 95 ℃. Det finns dock fortfarande begränsad erfarenhet av HT-BTES med bara några få installationer i drift över hela världen. Syftet med detta masterexamensarbete har varit att utvärdera en potentiell systemkonfigurationskonfiguration för effektiv utvinning och lagring av spillvärme från Gärstadverkets kraftvärmeverk kopplat till ett HT-BTES. Data från tidigare drift av kraftvärmeverket och en befintlig TRNSYS-modell, utvecklad hos KTH och Bengt Dahlgren AB baserat på den välkända DST-metoden (Duct Ground Heat Storage Model), användes som utgångspunkt för utvecklingen av en ny, mer komplett modell som inkluderar en värmepumpsmodell. Värmepumpsmodellen utvecklades utifrån data från en värmepumpstillverkare för ett icke-standardiserat 50 MW värmepumpsystem, med R717 som kylmedium. Som ett ytterligare mål har designparametrar och erfarenheter från drift av redan befintliga HT-BTES installationer sammanställts och analyserats. BTES-designen varierades genom simuleringar med olika antal borrhål och borrhålsdjup. Systemet simulerades fortsatt med två olika borrhålsvärmeväxlare (BHE): dubbla U-rör och koaxiala BHE. Baserat på resultaten hittades tre optimerade BTES-geometrier: 1 400 borrhål med dubbla U-rörs BHE och 300 m borrhålsdjup, 1 300 borrhål med koaxiala BHE och 300 m borrhålsdjup samt en design med 1 500 borrhål med dubbla U-rör och ett borrhålsdjup på 275 m – alla tre konfigurationer med ett borrhålsavstånd på 5 m och borrhålsloopar med tre borrhål kopplade i serie. De tre BTES-geometrierna visade liknande resultat med potential att lagra cirka 107 GWh / år och att extrahera runt 93 GWh / år med användning av en värmepump. Den resulterande urladdningstemperaturen från borrhålslagret varierar mellan 40-60 °C och upp till 70 °C i början av urladdningsperioden under det tionde simuleringsåret. Vidare studie krävs dock för att undersöka tillgängligheten av koaxiala BHE på marknaden som kan fungera med de höga temperaturerna i borrhålslagret.

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Calderón, Díaz Alejandro. "Study of solid particle materials as high temperature Thermal Energy Storage and Heat Transfer Fluid for Concentrating Solar Power." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667863.

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Renewable energies have a major role in today’s energy systems development, energy security and climate change fight. Thermal Concentrating Solar Power (CSP) has the potential to get up to 11.3% of world’s electricity production with the adequate support. This type of renewable energy has proved to be price competitive and to have the advantage of integrating Thermal Energy Storage (TES). This adds the generation flexibility that other renewable energies, like wind or photovoltaics, does not have integrated. In order to continue developing this technology, solid particle CSP has been proposed. This design uses granular solid materials as Heat Transfer Fluid (HTF) and TES material in solar towers in order to be able to achieve higher operation temperatures, than current commercial CSP. Higher temperature means more efficiency in heat-to-electricity conversion, due to the use of better power generation cycles. The main objective of this thesis is to enhance relevance and provide theoretical and experimental background for solid particles to be used as TES material and HTF for CSP tower power plants, from the materials perspective, by using existent or new methodologies. During this dissertation, current scientific output and relevance were studied in two separate contributions, one for CSP and the other for TES, both by using bibliometric methods. For the CSP study, additional analyses were carried out according to the harvesting technologies (parabolic trough, solar tower, Stirling dish and linear Fresnel). For the TES study, the additional analyses were performed according to the different ways to store thermal energy (sensible, latent and thermochemical). For both analyses, most productive countries, regions, authors, journals and research communities were identified. Moreover, funding impact and cooperation between countries and authors were analyzed. For developing these bibliometric analyses, a specific methodology was implemented following Bibliometrics principles. For these purposes, two existing software programs were used for a part of the analysis, while for performing the rest of the analysis a special software was developed ad-hoc for this study. For providing background, two state-of-the-art analyses were performed in order to get current development status of solid particle CSP. The first one was oriented to the plant design itself. Several solar receivers were analyzed, as well as TES, Heat Exchanger (HEX) and conveyance systems. During the second state-of-the-art, a material driven study was carried out in order to understand the behavior expected by the particle media and to identify some of the materials proposed by the most relevant researchers in this field. Next step of this dissertation was focused on establishing the design criteria for solid particle CSP technology, from the materials science perspective. This was achieved by finding the most relevant objectives that a power plant of this kind must comply, as well as the influence of the particle media properties and parameters. Last part of this dissertation is related with two studies regarding the durability of some of the most promising solid particle materials from high temperature exposure effect perspective. The first study was focused on analyzing the effect of long term high temperature (900 °C) in the optical, mechanical, thermal and chemical properties and parameters of the solid particle material. The second study was focused in the effect of long term thermal cycling, in which is considered that the materials should resist several thousand charge-discharge cycles remaining with acceptable operational conditions. For achieving an accelerated thermal cycling test with realistic thermal conditions, a novel device was developed to perform the thousands of thermal cycles required. Electronic, software and hardware design was developed and implemented. Current device has performed more than 20 thousand cycles for different kind of materials, analyzing the same properties and parameters as the first study.
Para continuar desarrollando la energía solar de concentración (CSP), se ha propuesto el uso de sólidos particulados. En este nuevo tipo de planta CSP de torre, se utilizan materiales sólidos granulados como Fluido de Transferencia de Calor (HTF) y material para el almacenamiento de energía térmica (TES). El objetivo principal de esta tesis es establecer la relevancia y proporcionar antecedentes, tanto teóricos como experimentales, sobre el uso de sólidos particulados para esta nueva tecnología. Durante este trabajo, la producción científica actual y la relevancia científica fueron estudiados mediante dos estudios bibliométricos, una para CSP y otra para TES. Para ambos análisis, se identificaron los países, regiones, autores, revistas, comunidades de investigación más productivos, el impacto del financiamiento y la cooperación entre países y autores. Para este fin, se utilizaron tres programas informáticos, de los cuales uno tuvo que se desarrollado a la medida. Se realizaron dos análisis del estado del arte para obtener el estado actual de desarrollo de las plantas CSP con uso de sólidos particulados. En el primero, se analizaron varios receptores solares, así como sistemas TES, intercambiadores de calor (HEX) y sistemas de transporte del material granulado. En el segundo, se llevó a cabo un estudio basado en los sólidos particulados, comprendiendo el comportamiento de estos materiales, así como recopilar los materiales potenciales. Se establecieron los criterios de diseño desde la perspectiva de los materiales, logrando encontrar los objetivos relevantes, y la influencia de las propiedades y parámetros de estos materiales. Se realizaron dos estudios sobre la durabilidad en cuanto a la exposición a altas temperaturas. El primero, se centró en analizar el efecto de la temperatura a largo plazo y su efecto en las propiedades ópticas, mecánicas, térmicas y químicas. El segundo, se centró en el efecto de los miles de ciclos térmicos esperados. Se desarrolló un nuevo dispositivo capaz de realizar los ciclos térmicos requeridos en las condiciones requeridas. Se desarrolló e implementó el diseño electrónico, de software y de hardware. Se caracterizaron las mismas propiedades analizadas en el primer estudio.

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Egersand, Anton, and Emil Fransson. "THE POTENTIAL OF A LATENT HEAT THERMAL ENERGY STORAGE : An Investigation on Rocklunda's Sport Facilities." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-55539.

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The world is ever increasing in its energy usage, making energy that is sustainable and secure harder to achieve. To fulfil the Paris agreement to limit global warming, the world needs to transition from fossil fuels toward more renewable energy sources, like wind and solar, but these sources have fluctuation in supply which often create a mismatch with demand. To combat this issue, thermal energy storage can be utilized, and one such technology is latent heat thermal energy storage. This study aimed to investigate the potential of latent heat thermal energy storage by developing a simple model of such a system and studying its impact on Rocklunda’s sport facilities. The model was developed by using MATLAB, primarily using the photovoltaic overproduction of the facilities to store as energy for the latent heat thermal energy storage. The implemented storage, based on the model’s result, had overall positive impact on the facilities. The optimized storage capacity was about 510 kWh, which throughout the storage’s lifetime would save ~4 989 MWh worth of heat by using the best performing phase change material: aluminium-silicon. The storage would also be able to utilize ~82% of the annual photovoltaic overproduction that would otherwise be unused/sold as well as reducing the heat demand by ~12% by using the heat stored via the storage. The implementation also proved to have beneficial effects on the environment as the saved heat was the equivalent of mitigating ~304 ton of CO2 emissions. Furthermore, there is a profit of ~236 000 SEK.
Reduction and Reuse of energy with interconnected Distribution and Demand (R2D2)

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He, Bo. "High-Capacity Cool Thermal Energy Storage for Peak Shaving - a Solution for Energy Challenges in the 21st century." Doctoral thesis, KTH, Chemical Engineering and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3781.

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Due to climatic change, increasing thermal loads inbuildings and rising living standards, comfort cooling inbuildings is becoming increasingly important and the demand forcomfort cooling is expanding very quickly around the world. Theincreased cooling demand results in a peak in electrical powerdemand during the hottest summer hours. This peak presents newchallenges and uncertainties to electricity utilities and theircustomers.

Cool thermal storage systems have not only the potential tobecome one of the primary solutions to the electrical powerimbalance between production and demand, but also shift coolingenergy use to off-peak periods and avoid peak demand charges.It increases the possibilities of utilizing renewable energysources and waste heat for cooling generation. In addition, acool storage can actually increase the efficiency of combinedheat and power (CHP) generation provided that heat drivencooling is coupled to CHP. Then, the cool storage may avoidpeaks in the heat demand for cooling generation, and this meansthat the CHP can operate at design conditions in most oftime.

Phase Change Materials (PCMs) used for cool storage hasobtained considerable attention, since they can be designed tomelt and freeze at a selected temperature and have shown apromising ability to reduce the size of storage systemscompared with a sensible heat storage system because they usethe latent heat of the storage medium for thermal energystorage.

The goal of this thesis is to define suitable PCM candidatesfor comfort cooling storage. The thesis work combines differentmethods to determine the thermophysical properties oftetradecane, hexadecane and their binary mixtures, anddemonstrates the potential of using these materials as PCM forcomfort cooling storage. The phase equilibrium of the binarysystem has been studied theoretically as well asexperimentally, resulting in the derivation of the phasediagram. With knowledge of the liquid-solid phase equilibriumcharacteristics and the phase diagram, an improvedunderstanding is provided for the interrelationships involvedin the phase change of the studied materials. It has beenindicated that except for the minimum-melting point mixture,all mixtures melt and freeze within a temperature range and notat a constant temperature, which is so far often assumed in PCMstorage design. In addition, the enthalpy change during thephase transition (heat of fusion) corresponds to the phasechange temperature range; thus, the storage density obtaineddepends on how large a part of the phase change temperaturerange is valid for a given application.

Differential Scanning Calorimetery (DSC) is one frequentlyused method in the development of PCMs. In this thesis, it hasbeen found that varying results are obtained depending on theDSC settings throughout the measurements. When the DSC runs ata high heating/cooling rate it will lead to erroneousinformation. Also, the correct phase transition temperaturerange cannot be obtained simply from DSC measurement. Combiningphase equilibrium considerations with DSC measurements gives areliable design method that incorporates both the heat offusion and the phase change temperature range.

The potential of PCM storage for peak shaving in differentcooling systems has been demonstrated. A Computer model hasbeen developed for rapid phase equilibrium calculation. The useof phase equilibrium data in the design of a cool storagesystem is presented as a general methodology.

Keywords:Comfort cooling, peak shaving, PCM, coolthermal storage system, DSC, phase change temperature range,the heat of fusion, phase equilibrium, phase diagram. Language:English

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FERNANDEZ, ANTONIO P. R. "Estudo das características elétricas e microestruturais de supercapacitores para armazenamento de energia." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26824.

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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T16:52:08Z No. of bitstreams: 0
Made available in DSpace on 2016-11-11T16:52:08Z (GMT). No. of bitstreams: 0
Esta dissertação tem por objetivo reportar dados relativos às características elétricas e microestruturais de eletrodos aplicadas em dispositivos armazenadores de energia, especificamente supercapacitores constituídos por eletrodos de carvão ativado. Os parâmetros elétricos estudados foram a resistência em série equivalente obtida pelo método da interrupção de corrente (ESR(Inst)) (sendo que a sigla ESR é oriunda do termo inglês Equivalent Series Resistance), a resistência em paralelo equivalente (EPR(Dep)) obtida pelo método do valor dependente (sendo que a sigla EPR é oriunda do termo inglês Equivalent Parallel Resistance) e a capacitância (C(DC)) obtida pelo método da corrente contínua (sendo que a sigla DC oriunda do termo inglês Direct Current). Tais parâmetros foram escolhidos devido ao impacto que causam no tempo de vida útil, na capacidade de armazenamento de cargas elétricas, na velocidade de carga e descarga, na perda por efeito termoiônico nos processos de carga e descarga e na perda de cargas armazenadas devido à autodescarga em supercapacitores. Os dados microestruturais reportam por meio de imagens a homogeneidade da porosidade e por meio de valores correlacionados a composição química e eventuais contaminações presentes nos eletrodos. Os dados e valores coletados possuem a intenção de servir como referência comparativa de qualidade e apontar qual parâmetro afeta mais a qualidade do supercapacitor. Para tanto foram realizados testes a fim de coletar valores de C(DC), ESR(Inst) e EPR(Dep) após a exposição de supercapacitores de 1F/5,5V a temperaturas de 50ºC, 75ºC, 100ºC e 125ºC por 672 horas, sendo os dados coletados ao inicio dos testes, à temperatura ambiente, e posteriormente a cada 168 horas. Feitos os experimentos concluiu-se que o parâmetro que sofreu maior deterioração com o acréscimo de energia térmica foi a EPR(Dep), em seguida a C(DC), que de fato pouco sofreu alteração e a ESR(Inst), em que a mudança dentro do erro de medição foi imperceptível.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Ali, Haider Adel Ali, and Ziad Namir Abdeljawad. "THERMAL MANAGEMENT TECHNOLOGIES OF LITHIUM-ION BATTERIES APPLIED FOR STATIONARY ENERGY STORAGE SYSTEMS : Investigation on the thermal behavior of Lithium-ion batteries." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-48904.

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Batteries are promising sources of green and sustainable energy that have been widely used in various applications. Lithium-ion batteries (LIBs) have an important role in the energy storage sector due to its high specific energy and energy density relative to other rechargeable batteries. The main challenges for keeping the LIBs to work under safe conditions, and at high performance are strongly related to the battery thermal management. In this study, a critical literature review is first carried out to present the technology development status of the battery thermal management system (BTMS) based on air and liquid cooling for the application of battery energy storage systems (BESS). It was found that more attention has paid to the BTMS for electrical vehicle (EV) applications than for stationary BESS. Even though the active forced air cooling is the most commonly used method for stationary BESS, limited technical information is available. Liquid cooling has widely been used in EV applications with different system configurations and cooling patterns; nevertheless, the application for BESS is hard to find in literature.To ensure and analyze the performance of air and liquid cooling system, a battery and thermal model developed to be used for modeling of BTMS. The models are based on the car company BMW EV battery pack, which using Nickel Manganese Cobalt Oxide (NMC) prismatic lithium-ion cell. Both air and liquid cooling have been studied to evaluate the thermal performance of LIBs under the two cooling systems.According to the result, the air and liquid cooling are capable of maintaining BESS under safe operation conditions, but with considering some limits. The air-cooling is more suitable for low surrounding temperature or at low charging/discharge rate (C-rate), while liquid cooling enables BESS to operate at higher C-rates and higher surrounding temperatures. However, the requirement on the maximum temperature difference within a cell will limits the application of liquid cooling in some discharge cases at high C-rate. Finally, this work suggests that specific attention should be paid to the pack design. The design of the BMW pack is compact, which makes the air-cooling performance less efficient because of the air circulation inside the pack is low and liquid cooling is more suitable for this type of compact battery pack.

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Trahan, Jamie. "A Technical and Economic Comparative Analysis of Sensible and Latent Heat Packed Bed Storage Systems for Concentrating Solar Thermal Power Plants." Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5598.

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Though economically favorable when compared to other renewable energy storage technologies, thermal energy storage systems for concentrating solar thermal power (CSP) plants require additional cost reduction measures to help transition CSP plants to the point of grid-parity. Thermocline packed bed storage is regarded as one potential low cost solution due to the single tank requirement and low cost storage media. Thus sensible heat storage (SHS) and latent heat storage (LHS) packed bed systems, which are two thermocline varieties, are frequently investigated. LHS systems can be further classified as single phase change material (PCM) systems or cascaded systems wherein multiple PCMs are employed. This study compared the performance of SHS, single PCM, and cascaded PCM direct storage systems under the conditions that may be encountered in utility-scale molten salt CSP plants operating between 565°C and 288°C. A small-scale prototype SHS packed bed system was constructed and operated for use in validating a numerical model. The drawbacks of the latent heat storage process were discussed, and cascaded systems were investigated for their potential in mitigating the issues associated with adopting a single PCM. Several cascaded PCM configurations were evaluated. The study finds that the volume fraction of each PCM and the arrangement of latent heat in a 2-PCM and a 3-PCM system influences the output of the system, both in terms of quality and quantity of energy. In addition to studying systems of hypothetical PCMs, real salt PCM systems were examined and their selection process was discussed. A preliminary economic assessment was conducted to compare the cost of SHS, single-PCM LHS, cascaded LHS, and state-of-the-art 2-tank systems. To the author's knowledge, this is the first study that compares the cost of all three thermocline packed bed systems with the 2-tank design. The SHS system is significantly lower in cost than the remaining systems, however the LHS system does show some economic benefit over the 2-tank design. If LHS systems are to be viable in the future, low cost storage media and encapsulation techniques are necessary.

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Lundgren, Henrik. "Thermal Aspects and Electrolyte Mass Transport in Lithium-ion Batteries." Doctoral thesis, KTH, Tillämpad elektrokemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166857.

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Temperature is one of the most important parameters for the performance, safety, and aging of lithium-ion batteries and has been linked to all main barriers for widespread commercial success of electric vehicles. The aim of this thesis is to highlight the importance of temperature effects, as well as to provide engineering tools to study these. The mass transport phenomena of the electrolyte with LiPF6 in EC:DEC was fully characterized in between 10 and 40 °C and 0.5 and 1.5 M, and all mass transport properties were found to vary strongly with temperature. A superconcentrated electrolyte with LiTFSI in ACN was also fully characterized at 25 °C, and was found to have very different properties and interactions compared to LiPF6 in EC:DEC. The benefit of using the benchmarking method termed electrolyte masstransport resistivity (EMTR) compared to using only ionic conductivity was illustrated for several systems, including organic liquids, ionic liquids, solid polymers, gelled polymers, and electrolytes containing flame-retardant additives. TPP, a flame-retardant electrolyte additive, was evaluated using a HEV load cycle and was found to be unsuitable for high-power applications such as HEVs. A large-format commercial battery cell with a thermal management system was characterized using both experiments and a coupled electrochemical and thermal model during a PHEV load cycle. Different thermal management strategies were evaluated using the model, but were found to have only minor effects since the limitations lie in the heat transfer of the jellyroll.
Temperatur är en av de viktigaste parametrarna gällande ett litiumjonbatteris prestanda, säkerhet och åldring och har länkats till de främsta barriärerna för en storskalig kommersiell framgång för elbilar. Syftet med den här avhandlingen är att belysa vikten av temperatureffekter, samt att bidra med ingenjörsverktyg att studera dessa. Masstransporten för elektrolyten LiPF6 i EC:DEC karakteriserades fullständigt i temperaturintervallet 10 till 40 °C för LiPF6-koncentrationer på 0.5 till 1.5 M. Alla masstransport-egenskaper fanns variera kraftigt med temperaturen. Den superkoncentrerade elektrolyten med LiTFSI i ACN karakteriserades även den fullständigt vid 25 °C. Dess egenskaper och interaktioner fanns vara väldigt annorlunda jämfört med LiPF6 i EC:DEC. Fördelen med att använda utvärderingsmetoden elektrolytmasstransportresistivitet (EMTR) jämfört med att endast mäta konduktivitet illustrerades för flertalet system, däribland organiska vätskor, jonvätskor, fasta polymerer, gellade polymerer, och elektrolyter med flamskyddsadditiv. Flamskyddsadditivet TPP utvärderades med en hybridbils-lastcykel och fanns vara olämplig för högeffektsapplikationer, som hybridbilar. Ett kommersiellt storformatsbatteri med ett temperatur-kontrollsystem karakteriserades med b.de experiment och en kopplad termisk och elektrokemisk modell under en lastcykel utvecklad för plug-inhybridbilar. Olika strategier för kontroll av temperaturen utvärderades, men fanns bara ha liten inverkan på batteriets temperatur då begränsningarna för värmetransport ligger i elektrodrullen, och inte i batteriets metalliska ytterhölje.

QC 20150522

Swedish Hybrid Vehicle Center

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27

Gondre, Damien. "Numerical modeling and analysis of heat and mass transfers in an adsorption heat storage tank : Influences of material properties, operating conditions and system design on storage performances." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI022/document.

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Le développement de solutions de stockage de l'énergie est un défi majeur pour permettre la transition énergétique d'un mix énergétique fortement carboné vers une part plus importante des énergies renouvelables. La nécessité de stocker de l'énergie vient de la dissociation, spatiale et temporelle, entre la source et la demande d'énergie. Stocker de l'énergie répond à deux besoins principaux : disposer d'énergie à l'endroit et au moment où on en a besoin. La consommation de chaleur à basse température (pour le chauffage des logements et des bureaux) représente une part importante de la consommation totale d'énergie (environ 35 % en France en 2010). Le développement de solutions de stockage de chaleur est donc d'une grande importance, d'autant plus avec la montée en puissance des énergies renouvelables. Parmi les technologies de stockage envisageables, le stockage par adsorption semble être le meilleur compromis en termes de densité de stockage et de maintient des performances sur plusieurs cycles de charge-décharge. Cette thèse se focalise donc sur le stockage de chaleur par adsorption, et traite de l'amélioration des performances du stockage et de l'intégration du système au bâtiment. L'approche développée pour répondre à ces questions est numérique. L'influence des propriétés thermophysiques de l'adsorbant et du fluide sur la densité de puissance d'une part, mais aussi sur la densité de stockage et l'autonomie du système, est étudiée. L'analyse des résultats permet de sélectionner les propriétés des matériaux les plus influentes et de mieux comprendre les transferts de chaleur et de masse au sein du réacteur. L'influence des conditions opératoires est aussi mise en avant. Enfin, il est montré que la capacité de stockage est linéairement dépendante du volume de matériau, tandis que la puissance dépend de la surface de section et que l'autonomie dépend de la longueur du lit d'adsorbant. Par ailleurs, le rapport entre l'énergie absorbée (charge) et relâchée (décharge) est d'environ 70 %. Mais pendant la phase de charge, environ 60 % de la chaleur entrant dans le réacteur n'est pas absorbée et est directement relâchée à la sortie. La conversion globale entre l'énergie récupérable et l'énergie fournie n'est donc que de 25 %. Cela montre qu'un système de stockage de chaleur par adsorption ne peut pas être pensé comme un système autonome mais doit être intégré aux autres systèmes de chauffage du bâtiment et aux lois de commande qui les régissent. Utiliser la ressource solaire pour le préchauffage du réacteur est une idée intéressante car elle améliore l’efficacité de la charge et permet une réutilisation de la part récupérée en sortie pour le chauffage direct du bâtiment. La part stockée sous forme sensible peut être récupérée plusieurs heures plus tard. Le système est ainsi transformé en un stockage combiné sensible/adsorption, avec une solution pour du stockage à long terme et pour du stockage à court terme
The development of energy storage solutions is a key challenge to enable the energy transition from fossil resources to renewable energies. The need to store energy actually comes from a dissociation between energy sources and energy demand. Storing energy meets two principal expectations: have energy available where and when it is required. Low temperature heat, for dwellings and offices heating, represents a high share of overall energy consumption (i.e. about 35 %). The development of heat storage solutions is then of great importance for energy management, especially in the context of the growing part of renewable energies. Adsorption heat storage appears to be the best trade off among available storage technologies in terms of heat storage density and performances over several cycles. Then, this PhD thesis focuses on adsorption heat storage and addresses the enhancement of storage performances and system integration. The approach developed to address these issues is numerical. Then, a model of an adsorption heat storage tank is developed, and validated using experimental data. The influence of material thermophysical properties on output power but also on storage density and system autonomy is investigated. This analysis enables a selection of particularly influencing material properties and a better understanding of heat and mass transfers. The influence of operating conditions is also underlined. It shows the importance of inlet humidity on both storage capacity and outlet power and the great influence of discharge flowrate on outlet power. Finally, it is shown heat storage capacity depends on the storage tank volume, while outlet power depends on cross section area and system autonomy on bed length. Besides, the conversion efficiency from absorbed energy (charge) to released energy (discharge) is 70 %. But during the charging process, about 60 % of incoming heat is not absorbed by the material and directly released. The overall conversion efficiency from energy provided to energy released is as low as 25 %. This demonstrates that an adsorption heat storage system cannot be thought of as a self-standing component but must be integrated into the building systems and control strategy. A clever use of heat losses for heating applications (in winter) or inlet fluid preheating (in summer) enhances global performances. Using available solar heat for system preheating is an interesting option since a part is instantly retrieved at the outlet of the storage tank and can be used for direct heating. Another part is stored as sensible heat and can be retrieved a few hours later. At least, it has the advantage of turning the adsorption storage tank into a combined sensible-adsorption storage tank that offers short-term and long-term storage solutions. Then, it may differ avoidable discharges of the sorption potential and increase the overall autonomy (or coverage fraction), in addition to optimizing chances of partial system recharge

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28

Lopes, Telma Sofia Risso. "Advantages and drawbacks of a linear focusing system with low melting point molten salts." Master's thesis, Universidade de Évora, 2019. http://hdl.handle.net/10174/31058.

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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.

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Ntsendwana, Bulelwa. "Advanced low temperature metal hydride materials for low temperature proton exchange membrane fuel cell application." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_8494_1307431585.

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Energy is one of the basic needs of human beings and is extremely crucial for continued development of human life. Our work, leisure and our economic, social and physical welfare all depend on the sufficient, uninterrupted supply of energy. Therefore, it is essential to provide adequate and affordable energy for improving human welfare and raising living standards. Global concern over environmental climate change linked to fossil fuel consumption has increased pressure to generate power from renewable sources [1]. Although substantial advances in renewable energy technologies have been made, significant challenges remain in developing integrated renewable energy systems due primarily to mismatch between load demand and source capabilities [2]. The output from renewable energy sources such as photo-voltaic, wind, tidal, and micro-hydro fluctuate on an hourly, daily, and seasonal basis. As a result, these devices are not well suited for directly powering loads that require a uniform and uninterrupted supply of input energy.

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30

Sara, Hanna. "Analysis and valorization of new thermal management systems for a vehicle powertrain application." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0019/document.

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La gestion thermique est un des moyens de réduction de la consommation spécifique d’un véhicule. Avec le réchauffement climatique, les normes de dépollution deviennent de plus en plus sévères et les constructeurs automobiles cherchent à améliorer le rendement des véhicules. Le but de ces travaux de recherche est de valoriser, par simulation numérique, les nouveaux systèmes de gestion thermique en fonction du cycle d’homologation et de la température ambiante.Un modèle de simulation 1-D du moteur et de ses circuits de refroidissement et de lubrification ont été développés en utilisant le logiciel GT-Suite. Quatre cycles d’homologation ont été choisis : NEDC, WLTC, AH et AU. De plus, un nouveau cycle a été proposé durant cette étude. Le bilan d’énergie effectué pendant les différentes phases des cycles souligne l’importance du stockage et de la récupération d’énergie.Le stockage d’énergie dans un volume eau et/ou d’huile abouti à l’amélioration de la montée en température des deux fluides. Plusieurs configurations ont été proposées comme, par exemple, un carter d’huile multifonctionnel.Ainsi, une réduction importante de la consommation en carburant est obtenue.La récupération de chaleur au sein des gaz d’échappement est ensuite mise en oeuvre. L’échangeur est caractérisé sur un banc d’essais puis modélisé. Le réchauffement indirect et direct d’huile abouti à une réduction importante des frottements et de la consommation. Une configuration est proposée afin de contrôler la température maximale de l’huile.Finalement, différentes stratégies comme : le type d’huile, l’isolation du moteur, une température de régulation plus élevée etc… ont été étudiées et valorisées
Thermal management proved itself in improving the fuel efficiency of the engine. Nowadays, automotive companies tend to apply different strategies to answer the greenhouse severe laws. The PhD aim is to valorize and analyze the different thermal management strategies with numerical simulations over different driving cycles and ambient conditions. A 1-D simulation code of the engine and its hydraulic circuits were built using GT-Suite. Four known driving cycles were chosen: NEDC, WLTC, AH and AU. In addition, an in-house developed driving cycle was introduced. An energy balance made over the different stages of the driving cycles underlines the importance of the heat storage and the exhaust heat recovery strategies.Heat recovery was applied over the coolant and the oil at ambient temperatures of -7°C and 20°C. Hot coolant storage and hot oil storage led to improve the coolant and lubricant initial temperatures respectively. Different configurations (total of 7) were proposed and studied. A multifunctional oil sump was introduced. Important fuel consumption savings were obtained. Exhaust heat recovery was then valorized. Heat exchanger was characterized over experimental setup then added to the engine model. Indirect and direct heating of the lubricant as well as both strategies back to back were tested. Remarkable friction reduction and fuel savings were obtained. Special configuration was proposed to control the lubricant high temperature instead of the bypass on the exhaust line. The study ended by valorizing minor strategies as the oil’s grade influence, the engine insulation, high temperature set point …

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Müller, Daniel Richard [Verfasser], Traugott [Akademischer Betreuer] Scheytt, Simona [Akademischer Betreuer] Regenspurg, Thomas [Gutachter] Neumann, Traugott [Gutachter] Scheytt, Michael [Gutachter] Kühn, and Simona [Gutachter] Regenspurg. "The impact of temperature and oxygen on water-rock interactions in siliciclastic rocks and implications for aquifer thermal energy storage systems / Daniel Richard Müller ; Gutachter: Thomas Neumann, Traugott Scheytt, Michael Kühn, Simona Regenspurg ; Traugott Scheytt, Simona Regenspurg." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1174990546/34.

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Fella, Thierry. "Contribution a l'etude du comportement thermomecanique de sols non satures : mise au point d'un appareil triaxial thermique." Toulouse 3, 1987. http://www.theses.fr/1987TOU30229.

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Realisation, mise au point et premieres utilisations d'un appareil triaxial nouveau, par l'introduction du parametre temperature. Utilisation pour prevoir le comportement thermique, hydraulique et mecanique d'un sol non sature, dans un contexte de stockage de chaleur dans le sous-sol

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33

Lin, JiaCheng, and HaoRan Teng. "Influence of Nucleation Techniques on the Degree of Supercooling and Duration of Crystallization for Sugar Alcohol as Phase Change Material : Investigation on erythritol-based additiveenhanced Composites." Thesis, KTH, Energiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-257758.

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Utilizing Phase Change Materials (PCM) for Latent Thermal Energy Storage (LTES) applications have previously been extensively researched as a measure to reduce greenhouse gas emissions from energy consumption. In order to make use of the waste heat from industrial processes for LTES purposes, a new demand emerged for PCMs capable of phase change in mid-temperature ranges of 100 °C - 200 °C. This higher temperature requirement made most of the previously studied material inapplicable as they had much lower melting and solidification temperatures. With this in mind, a new generation of PCMs consisting of Sugar Alcohols (SA) has been proposed. Erythritol is seen as an especially promising SA with good thermophysical properties for LTES purposes. However, it has been shown to suffer from severe supercooling, which makes it unreliable in real applications. To eradicate this issue, two additives, Graphene Oxide (GO) and Polyvinylpyrrolidone (PVP) at varying mass fractions were mixed with pure erythritol to form a composite which was studied using the Temperature-history (T-history) method to determine its effectiveness in reducing supercooling. Results show that at its most effective mass fraction, GO reduces supercooling by 28 o C and a 31 o C reduction is seen by the addition of PVP. The impacts on the duration of crystallization was also documented and analyzed using the same method. It was observed that the duration of crystallization was increased with increasing mass fractions of the additives. Other important properties of the composites were also studied in order to determine the overall feasibility for industrial applications. It includes analysis of the storage capacity through latent heat, changes in viscosity along with impacts on thermal diffusivity of the composites.
Att använda fasändringsmaterial (PCM) för termisk energilagring i form av latent värme (LTES) har tidigare extensivt forskats och undersökts som en lösning för att minska utsläppen av växthusgaser från energiförbrukning. För att utnyttja spillvärme från industriella processer för LTES-ändamål uppstod en efterfrågan på PCM som ändrar fas i temperaturer mellan 100 °C - 200 °C. Detta krav på högre temperatur gjorde att de flesta av de tidigare aktuella materialen inte kunde tillämpas eftersom de hade mycket lägre smält- och kristalliseringstemperaturer. Med detta i åtanke har en ny generation av PCM bestående av sockeralkoholer (SA) föreslagits. Erytritol ses som ett särskilt lovande SA med goda egenskaper för LTES-ändamål. Den har dock visat sig drabbas av svår underkylning, vilket gör den opålitligt i verkliga tillämpningar. För att utrota detta problem blandades två tillsatser, Graphene Oxide (GO) och Polyvinylpyrrolidone (PVP) vid olika massfraktioner med ren erytritol för att bilda en komposit som studerades med metoden Temperature-history (T-history) för att bestämma dess effektivitet på att minska underkylningen. Resultaten visar att GO på sin mest effektiva massfraktion minskar underkylningen med 28 o C och tillsats av PVP lyckats minska den med som mest 31 o C. Påverkningarna på varaktighet av kristallisering dokumenterades och analyserades med samma metod. Det var observerad att varaktigheten av kristallisering ökades med ökande massfraktioner av tillsatserna. Även andra viktiga egenskaper hos kompositerna studerades för att avgöra rimligheten att använda dessa för industriella tillämpningar. Det inkluderar analys av lagringskapaciteten genom latent värme, förändringar i viskositet tillsammans med påverkan på kompositernas termiska diffusivitet.

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Lahoori, Mojdeh. "Thermo-hydro-mechanical behavior of an embankment to store thermal energy." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0252.

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Le stockage de chaleur dans des géostructures énergétiques telles que des remblais est réalisable en installant des échangeurs horizontaux au sein des différentes couches de sol compacté. Dans ce système, l'énergie thermique qui est injectée en été via un fluide caloporteur circulant dans les échangeurs de chaleur, peut être extraite en période hivernale. Dans ces conditions, lors de la mise en service, le sol compacté est soumis à des variations de température quotidiennes et saisonnières. Ces variations pourraient modifier les performances thermo-hydro-mécaniques du sol compacté. Ainsi, le but de cette étude est d'étudier les performances thermiques et mécaniques d'un sol compacté lorsqu'il est soumis à des variations de température monotones et cycliques. Le sol étudié est un limon fréquemment utilisé dans les constructions de remblais en France. Le comportement thermique et mécanique du sol est étudié à un état de compactage correspondant aux propriétés thermiques optimales. Dans cet état, le sol compacté est non saturé ce qui complexifie l'estimation de ses propriétés thermiques. Pour pallier à ces difficultés, dans cette étude, un modèle inverse est proposé pour estimer les propriétés thermiques du sol compacté. L’efficacité du modèle est testée sur un jeu de données acquises dans la gamme de 20 à 50 °C dans un modèle réduit en laboratoire. Les valeurs obtenues sont ensuite comparées à des mesures classiques en laboratoire (méthodes en régime transitoire et en régime permanent). Cette méthode pourrait permettre de suivre l’évolution des propriétés thermiques du stockage et ainsi assurer son efficacité tout au long de sa durée de vie. La question de la stabilité à long terme de ces structures soumises à des variations thermiques monotones (5, 20 et 50 °C) et cycliques (5 à 50 °C) est ensuite abordée à l'aide d'essais oedomètriques et d’essais de cisaillement direct à température contrôlée. Les résultats des essais de compressibilité ont montré que l'effet de la variation de température est plus prononcé sous une contrainte verticale supérieure à la pression de préconsolidation. Les indices de compression et de gonflement peuvent être considérés comme indépendants des variations de température. Donc le tassement global du remblai dû aux variations thermiques pourrait être considéré comme négligeable. Les résultats des essais de cisaillement direct ont montré que les variations de température (monotones ou cycliques) augmentent la cohésion ce qui est avantageux pour la capacité portante et la stabilité des pentes des remblais. Dans la phase de conception d'un remblai de stockage, ces résultats seraient utiles au dimensionnement du système si des trajectoires thermomécaniques similaires à celles de cette étude sont respectées. Dans une dernière partie, une simulation numérique prenant en compte l'interaction sol-atmosphère est réalisée afin d’évaluer la performance thermique de ce sol compacté en conditions naturelles. Différentes profondeurs d'installation de boucles d'échangeurs de chaleur sont testéss ainsi que différents scénarios de stockage. Les résultats ont montré que le sol compacté augmente de 8.5% les performances du système par rapport à l'installation d'une boucle horizontale dans le sol naturel (non compacté). Les résultats de deux scénarios différents ont montré qu’en été avec un fluide ayant une température d'entrée de 50 °C augmente significativement la performance du système. De plus, une installation plus profonde des boucles horizontales améliore également la performance du système. Il convient de noter que le remblai est en interaction avec l'atmosphère depuis ses surfaces supérieure et latérale, l'efficacité thermique de la structure pourrait être affectée en raison des pertes de chaleur. Par conséquent, il est préférable de placer les échangeurs de chaleur loin des surfaces supérieures et latérales
Nowadays, thermal energy storage in geostructures like embankments can be possible by installing the horizontal heat exchangers in different layers of compacted soil. In this system, the thermal energy is stored in summer via a fluid, circulating in the heat exchangers, to be extracted in the demand period. When the serviceability of embankment as a medium to store the thermal energy starts, the compacted soil will be subjected to the daily and seasonally temperature variations. These seasonal temperature variations could modify the thermo-hydro-mechanical performance of the compacted soil. Thus, the aim of this study is to investigate the thermal and mechanical performances of a compacted soil when it is subjected to monotonic and cyclic temperature variations. The studied soil is a sandy lean clay that is frequently used in embankment constructions in France. The thermal and mechanical behavior of the soil are investigated at a compaction state corresponding to the optimal thermal properties. However, this compacted soil is unsaturated and the estimation of its thermal properties is complex. In this study, an inverse analytical model is proposed to estimate the thermal properties of the soil using temperature monitoring in the range of 20 to 50 °C in a soil compacted in a large container. The estimated thermal parameters were compared to classical laboratory measurements (transient and steady-state methods). The comparison showed that the estimated values were close to the results obtained in transient laboratory method. Using this method, the thermal efficiency of the compacted soil can be verified in the lifetime of the storage system. To ensure the structure stability, long-term mechanical response of these systems subjected to monotonic and cyclic temperature variations should be investigated. To achieve this aim, using temperature-controlled oedometric and direct shear devices, consolidation and shear parameters of the studied soil at different monotonic (5, 20, and 50 °C) and cyclic (5 to 50 °C) temperatures were investigated. The results of temperature-controlled oedometric tests showed that the effect of the temperature variation is more pronounced under vertical pressures higher than the preconsolidation pressure. The compression and swelling indexes could be considered independent of temperature variations. Therefore, the overall settlement of the embankment due to thermal variation near the heat exchangers could be considered negligible. The results of temperature-controlled direct shear tests showed that the temperature variations (monotonic heating or cooling, or temperature cycles) increased the cohesion which is beneficial for the bearing capacity and slope stability of embankments. These results can be directly used in the design of embankments to store thermal energy exposed to similar thermo-mechanical paths. Finally, the thermal performance of the compacted soil is verified using a numerical simulation considering the soil atmosphere interaction. Different depths installation of heat exchanger loops and different heat storage scenarios were simulated. The results showed that the compacted soil increases 8.5% the systems performance compared to the horizontal loop installation in the local soil. The results of two different scenarios show that an inlet fluid temperature of 50 °C in summer increases highly the system performance (13.7% to 41.4%) while the improvement is less significant (0% to 4.8%) for the ambient inlet temperature. Moreover, a deeper installation of horizontal loops increases the system performance. From the numerical simulation results can be concealed that the embankment is in interaction with the atmosphere from its upper and lateral surfaces, the thermal efficiency of the structure could be affected due to heat losses. Therefore, it is preferable to place the heat exchangers away from the top and side surfaces

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35

Lin, Jiacheng, and Haoran Teng. "Influence of Nucleation Techniques on the Degree of Supercooling and Duration of Crystallization for Sugar Alcohol as Phase Change Material : Investigation on erythritol-based additiveenhanced composites." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264271.

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Utilizing Phase Change Materials (PCM) for Latent Thermal Energy Storage (LTES) applications have previously been extensively researched as a measure to reduce greenhouse gas emissions from energy consumption. In order to make use of the waste heat from industrial processes for LTES purposes, a new demand emerged for PCMs capable of phase change in mid-temperature ranges of 100 °C - 200 °C. This higher temperature requirement made most of the previously studied material inapplicable as they had much lower melting and solidification temperatures. With this in mind, a new generation of PCMs consisting of Sugar Alcohols (SA) has been proposed. Erythritol is seen as an especially promising SA with good thermophysical properties for LTES purposes. However, it has been shown to suffer from severe supercooling, which makes it unreliable in real applications. To eradicate this issue, two additives, Graphene Oxide (GO) and Polyvinylpyrrolidone (PVP) at varying mass fractions were mixed with pure erythritol to form a composite which was studied using the Temperature-history (T-history) method to determine its effectiveness in reducing supercooling. Results show that at its most effective mass fraction, GO reduces supercooling by 28 oC and a 31 oC reduction is seen by the addition of PVP. The impacts on the duration of crystallization was also documented and analyzed using the same method. It was observed that the duration of crystallization was increased with increasing mass fractions of the additives. Other important properties of the composites were also studied in order to determine the overall feasibility for industrial applications. It includes analysis of the storage capacity through latent heat, changes in viscosity along with impacts on thermal diffusivity of the composites.
Att använda fasändringsmaterial (PCM) för termisk energilagring i form av latent värme (LTES) har tidigare extensivt forskats och undersökts som en lösning för att minska utsläppen av växthusgaser från energiförbrukning. För att utnyttja spillvärme från industriella processer för LTES-ändamål uppstod en efterfrågan på PCM som ändrar fas i temperaturer mellan 100 °C - 200 °C. Detta krav på högre temperatur gjorde att de flesta av de tidigare aktuella materialen inte kunde tillämpas eftersom de hade mycket lägre smält- och kristalliseringstemperaturer. Med detta i åtanke har en ny generation av PCM bestående av sockeralkoholer (SA) föreslagits. Erytritol ses som ett särskilt lovande SA med goda egenskaper för LTES-ändamål. Den har dock visat sig drabbas av svår underkylning, vilket gör den opålitligt i verkliga tillämpningar. För att utrota detta problem blandades två tillsatser, Graphene Oxide (GO) och Polyvinylpyrrolidone (PVP) vid olika massfraktioner med ren erytritol för att bilda en komposit som studerades med metoden Temperature-history (T-history) för att bestämma dess effektivitet på att minska underkylningen. Resultaten visar att GO på sin mest effektiva massfraktion minskar underkylningen med 28 oC och tillsats av PVP lyckats minska den med som mest 31 oC. Påverkningarna på varaktighet av kristallisering dokumenterades och analyserades med samma metod. Det var observerad att varaktigheten av kristallisering ökades med ökande massfraktioner av tillsatserna. Även andra viktiga egenskaper hos kompositerna studerades för att avgöra rimligheten att använda dessa för industriella tillämpningar. Det inkluderar analys av lagringskapaciteten genom latent värme, förändringar i viskositet tillsammans med påverkan på kompositernas termiska diffusivitet.

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Lambert, Julien. "Etude structurale d’aluminosilicates de calcium : application à la valorisation de déchets amiantés pour le stockage thermique d’énergie solaire." Thesis, Orléans, 2013. http://www.theses.fr/2013ORLE2012.

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L’objectif de ce travail de thèse est d’établir les relations entre les propriétés structurales et les conditions d’élaboration d’un vitrifiat de déchets amiantés (nom commercial Cofalit®), dans la perspective de fabriquer un prototype de module de stockage thermique d’énergie solaire. Malgré des provenances de déchets très diverses, les variations de compositions du vitrifiat restent limitées. Les conditions d’élaboration (de refroidissement en particulier) induisent par contre d’importantes disparités dans la microstructure. L’analyse d’une carotte de Cofalit nous a permis de déterminer les mécanismes de cristallisation lors de la fabrication du Cofalit (refroidissement non contrôlé), conduisant à un mélange de phases cristallisées et vitreuse. Nous avons étudié les propriétés structurales (par DRX et RMN) et de cristallisation d’échantillons modèles représentatifs du matériau industriel. Les variations de composition observées sur celui-ci ont été simulées par des ajouts de silice ou de chaux. L’influence de la teneur en fer sur les propriétés radiatives, structurales (verres et céramiques) et de cristallisation a également été quantifiée. Le suivi de la cristallisation séquentielle des céramiques a été effectué par DRX in situ à haute température, à partir de l’état vitreux et à partir de l’état liquide lors du refroidissement. Ces essais ont montré que le Cofalit cristallise complètement pour des vitesses de refroidissement inférieures à 10 K/min. La stabilité du Cofalit (au niveau structural) lors de recuits à hautes températures a également été démontrée
The aim of this work is to establish relationships between structural properties and production conditions of a vitrified asbestos-containing wastes ceramics (commercially named Cofalit®), with the goal of elaborating a prototype for thermal energy storage of solar energy. Despite various waste sources, the variations of composition observed for this material are limited. On the contrary, the production conditions (cooling stage in particular) induce important differences in the material microstructure. The analysis of a Cofalit core sample allowed us to determine the crystallisation mechanisms during its fabrication process (uncontrolled cooling), leading to a mixture of vitreous and crystalline phases. We propose a structural study (by XRD and NMR) and crystallization properties analyses of synthetic samples, representative of the industrial material. Observed variations of composition on the latter are simulated by additions of silica and lime. The influence of iron oxide content on radiative, structural and crystallization properties (of both glass and ceramic samples) have also been investigated. The following of the sequential crystallisation of ceramic samples has finally been performed using in situ high temperature XRD, from glassy state and during cooling from liquid state. These tests show that the Cofalit crystallizes completely for rates lower than 10 K/min. The high temperature stability on a structural level has also been demonstrated during annealings

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Helánová, Blanka. "Energetická náročnost přípravy teplé vody." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226006.

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Master’s thesis on Energy performance of domestic hot water preparation is concerned with calculating and comparing the energy performance of domestic hot water preparation in two-generation family house with an administrative part. Energy performance of domestic hot water preparation is calculated by two calculation methods and by experimental measurements, which are compared at the end of the thesis. The calculation is performed according to standard ČSN 06 0320 and set of standards ČSN EN 15316-3. Thesis is processed in accordance with valid legislative regulations.

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Saulich, Sven. "Generic design and investigation of solar cooling systems." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13627.

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This thesis presents work on a holistic approach for improving the overall design of solar cooling systems driven by solar thermal collectors. Newly developed methods for thermodynamic optimization of hydraulics and control were used to redesign an existing pilot plant. Measurements taken from the newly developed system show an 81% increase of the Solar Cooling Efficiency (SCEth) factor compared to the original pilot system. In addition to the improvements in system design, new efficiency factors for benchmarking solar cooling systems are presented. The Solar Supply Efficiency (SSEth) factor provides a means of quantifying the quality of solar thermal charging systems relative to the usable heat to drive the sorption process. The product of the SSEth with the already established COPth of the chiller, leads to the SCEth factor which, for the first time, provides a clear and concise benchmarking method for the overall design of solar cooling systems. Furthermore, the definition of a coefficient of performance, including irreversibilities from energy conversion (COPcon), enables a direct comparison of compression and sorption chiller technology. This new performance metric is applicable to all low-temperature heat-supply machines for direct comparison of different types or technologies. The achieved findings of this work led to an optimized generic design for solar cooling systems, which was successfully transferred to the market.

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Hallqvist, Karl. "Högtempererat borrhålslager för fjärrvärme." Thesis, Uppsala universitet, Naturresurser och hållbar utveckling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231586.

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The district heating load is seasonally dependent, with a low load during periods of high ambient temperature. Thermal energy storage (TES) has the potential to shift heating loads from winter to summer, thus reducing cost and environmental impact of District Heat production. In this study, a concept of high temperature borehole thermal energy storage (HT-BTES) together with a pellet heating plant for temperature boost, is presented and evaluated by its technical limitations, its ability to supply heat, its function within the district heating system, as well as its environmental impact and economic viability in Gothenburg, Sweden, a city with access to high quantities of waste heat. The concept has proven potentially environmentally friendly and potentially profitable if its design is balanced to achieve a good enough supply temperature from the HT-BTES. The size of the heat storage, the distance between boreholes and low borehole thermal resistance are key parameters to achieve high temperature. Profitability increases if a location with lower temperature demand, as well as risk of future shortage of supply, can be met. Feasibility also increases if existing pellet heating plant and district heating connection can be used and if lower rate of return on investment can be accepted. Access to HT-BTES in the district heating network enables greater flexibility and availability of production of District Heating, thereby facilitating readjustments to different strategies and policies. However, concerns for the durability of feasible borehole heat exchangers (BHE) exist in high temperature application.
Värmebehovet är starkt säsongsberoende, med låg last under perioder av högre omgivningstemperatur och hög last under perioder av lägre omgivningstemperaturer. I Göteborg finns en stor mängd spillvärme tillgängligt för fjärrvärmeproduktion sommartid när behovet av värme är lågt. Tillgång till säsongsvärmelager möjliggör att fjärrvärmeproduktion flyttas från vinterhalvår till sommarhalvår, vilket kan ge såväl lönsamhet som miljönytta. Borrhålsvärmelager är ett förhållandevis billigt sätt att lagra värme, och innebär att berggrunden värms upp under sommaren genom att varmt vatten flödar i borrhål, för att under vinterhalvåret användas genom att låta kallt vatten flöda i borrhålen och värmas upp. I traditionella borrhålsvärmelager används ofta värmepump för att höja värmelagrets urladdade temperatur, men på grund av höga temperaturkrav för fjärrvärme kan kostnaden för värmepump bli hög. I denna rapport föreslås ett system för att klara av att nå höga temperaturer till en lägre kostnad. Systemet består av ett borrhålsvärmelager anpassat för högre temperaturer (HT-BTES) samt pelletspannor för att spetsa lagrets utgående fluid för att nå hög temperatur. Syftet med rapporten är att undersöka potentialen för detta HT-BTES-system med avseende på dess tekniska begränsningar, förmåga till fjärrvärmeleverans, konsekvenser för fjärrvärmesystemet, samt lönsamhet och miljöpåverkan. För att garantera att inlagringen av värme inte är så stor att priset för inlagrad värme ökar väsentligt, utgår inlagringen från hur mycket värme som kyls bort i fjärrvärmenätet sommartid. I verkligheten finns betydligt mer värme tillgänglig till låg kostnad. När HT-BTES-systemet producerar fjärrvärme, ersätts fjärrvärmeproduktion från andra produktionsenheter, förutsatt att HT-BTES-systemets rörliga kostnader är lägre. I Göteborg ersätts främst naturgas från kraftvärme, men också en del flis. Kostnadsbesparingen beror på differensen för total fjärrvärmeproduktionskostnad med och utan HT-BTES-systemet. Undersökningen visar att besparingen är större om HT-BTES-systemet placeras i ett område där det är möjligt att mata ut fjärrvärme med lägre temperatur. Om urladdning från HT-BTES kan ske med hög temperatur ökar också besparingen. Detta sker om lagrets volym ökar, om avståndet mellan borrhål minskar eller om värmeöverföringen mellan det flödande vattnet i borrhålen och berggrunden ökar. Dessa egenskaper för lagret leder också till minskade koldioxidutsläpp. Storleken på besparingen beror dock i hög grad på hur bränslepriser utvecklas i framtiden. Strategiska fördelar med HT-BTES-systemet inkluderar; minskad miljöpåverkan, robust system med lång teknisk livslängd (för delar av HT-BTES-systemet), samt att inlagring av värme kan ske från många olika produktionsenheter. Dessutom kan positiva bieffekter identifieras. Undersökningen visar att HT-BTES-systemet har god potential att ge lönsamhet och minskad miljöpåverkan, och att anläggning och drift av lagret kan ske utan omfattande lokal miljöpåverkan. Det har också visats att de geologiska förutsättningarna för HT-BTES är goda på många platser i Göteborg, även om lokala förhållanden kan skilja sig åt. För att nå lönsamhet för HT-BTES-systemet krävs en avvägning på utformning av lagret för att nå hög urladdad temperatur utan att investeringskostnaden blir för stor. Undersökningen visar att om anslutning av HT-BTES-systemet kan ske mot befintlig anslutningspunkt eller till befintlig värmepanna kan investeringskostnaden minska och därmed lönsamheten öka. Placering av HT-BTES-systemet i områden med risk för överföringsbegränsningar kan också minska behovet av att förstärka fjärrvärmenätet, och således bidra till att minska de kostnader som förstärkning av nätet innebär. Betydelsefulla parametrar för att nå lönsamhet för HT-BTES-system inkluderar dessutom kostnaden för inlagrad värme liksom vilket vinstkrav som kan accepteras. Tillgång till HT-BTES möjliggör ökad nyttjandegrad och flexibilitet för fjärrvärmeproduktionsenheter, och därmed ökad anpassningsmöjlighet till förändrade förutsättningar på värmemarknaden. Dock återstår att visa att komponenter som klarar de höga temperaturkraven kan tillverkas till acceptabel kostnad.

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Monfors, Lisa, and Corinne Morell. "Byggnadsutformning för ett framtida varmare klimat : Klimatscenariers påverkan på energianvändning och termisk komfort i ett flerbostadshus och alternativa byggnadsutformningar för att förbättra resultatet." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-79953.

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När byggnader projekteras används klimatfiler från 1981-2010 för att dimensionera konstruktionen och energisystemet. Detta leder till att byggnader dimensioneras för ett klimat som varit och inte ett framtida klimat. SMHI har tagit fram olika klimatscenarier för framtiden som beskriver möjliga utvecklingar klimatet kan ta beroende på fortsatt utsläpp av växthusgaser. Dessa scenarier kallas för RCP (Representative Concentration Pathways). I denna studie används två olika klimatscenarier, RCP4,5 och RCP8,5. Siffran i namnet står för den strålningsdriving som förväntas uppnås år 2100. I RCP4,5 kommer medelårstemperaturen öka med 3 °C fram till år 2100 jämfört med referensperioden 1961-1990. För samma tidsperiod sker en ökning på 5 °C enligt RCP8,5. Ett flerbostadshus certifierad enligt Miljöbyggnad 2.2 nivå silver placerat i Vallentuna i Stockholms län används i denna studie som referensbyggnad. Byggnaden simuleras i programmet IDA ICE där den utsätts för RCP4,5 och RCP8,5. Resultatet visar att byggnaden inte skulle klara av kraven för Miljöbyggnad 2.2 gällande termiskt klimat sommar i något av de två klimatscenarierna. De operativa temperaturerna blir för höga i byggnaden utan att tillsätta komfortkyla. Byggnaden ändras för att se vilka faktorer som kan förbättra resultatet gällande det termiska klimatet. Resultatet visar att värmelagringsförmåga hos byggmaterial och solavskärmning har störst påverkan på det termiska klimatet. I studien gjordes flertal olika kombinationer av byggnadsutformningar. Enbart kombinationen av en tung stomme av betong tillsammans med fönster med lägre g-värde klarar kraven för Miljöbyggnad 2.2 i RCP4,5 och RCP8,5 utan komfortkyla. Kombinationen får lägst energianvändning i RCP8,5 av de olika kombinationerna som testats i studien. En kombination av tung stomme av KL-trä med lågt U-värde, fönster med lägre g-värde och komfortkyla får lägst energianvändning i grundklimatet och RCP4,5 av de olika kombinationerna som testats i studien trots användningen av komfortkyla. Frågan om vilket alternativ som är bäst ur ett hållbarhetsperspektiv är svårt att svara på. Det finns många aspekter som behöver tas i hänsyn till som byggnadens totala klimatavtryck både i tillverkning och användning. Oavsett val av konstruktion är det viktigt att projektera för att komfortkyla och solavskärmning skall kunna appliceras när ett varmare klimat råder.
When buildings are designed climate files from 1981 to 2010 are used to construct the building and its energy system. This leads to building being designed to a climate that has been and not to a future warmer climate that will come. SMHI has developed different climate scenarios for the future that describe different paths the climate can take depending on continued emissions of greenhouse gas. This climate scenarios are called RCP (Representative Concentration Pathways) In this study two of the climate scenarios, RCP4,5 and RCP8,5 are used. The number in the name stands for the radiation forcing that is expected in the year 2100. In RCP4,5 the mean average air temperature will increase with 3 °C until year 2100 compared to the reference period 1961-1990. In the same time period RCP8,5 will increase with 5 °C. An apartment building certified according to Miljöbyggnad 2.2 level silver placed in Vallentuna, Stockholms län is used as a reference building. The building is simulated through the simulation software program IDA ICE where it´s exposed to RCP4,5 and RCP8,5. The results demonstrate that the reference building would not meet Miljöbyggnad 2.2 requirement in the indicator about thermal comfort during summer. The operative temperature in the building is too high unless comfort cooling is used. The design of the building changes to see what factors can improve the results regarding the thermal comfort. The results demonstrate that thermal conductivity and solar shading has the greatest impact on thermal comfort. In this study several combinations of different building designs were made. Only the combination of a concrete frame with windows with low g-value met the requirement of Miljöbyggnad 2.2 regarding the thermal comfort during summer without using comfort cooling in RCP4,5 and RCP8,5. The combination had the lowest energy demand in RCP8,5 of all the combinations tested in the study. A combination of cross laminated wood frame with low U-value, windows with low g-value and comfort cooling had the lowest energy demand in the original climate file and RCP4,5 despite the use of comfort cooling. The questing about which building construction is the best from a sustainable perspective is difficult to answer. To answer that question the building´s total climate footprint in both production and use must be calculated. Regardless of the choice of building construction it is important to have in mind when designing a building that comfort cooling and solar shading should be easily applied when a warmer climate will prevail.

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Mayer, Didier. "Etude des proprietes thermophysiques de materiaux a transition solide-solide en vue d'applications au stockage de la chaleur." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0063.

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La determination de ces proprietes de cristaux plastiques de la famille des polyols a debouche sur la selection de trois composes organiques : le pentaerythritol, le pentaglycerine et le neopentylglycol, a partir desquels des melanges de solutions solides stables sont possibles. Le niveau de temperature peut etre choisi dans une gamme allant de 25**(o)c a 95**(o)c et de 165**(o)c a 185**(o)c; les enthalpies de transition sont comprises entre 80 kj/kg et 250 kj/kg. Mise en oeuvre avec incorporation de 80% de resines synthetiques en masse. Resultats

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Garg, Pardeep. "Thermodynamics of Distributed Solar Thermal Power Systems with Storage." Thesis, 2015. http://etd.iisc.ernet.in/2005/3940.

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Distributed power generation through renewable sources of energy has the potential of meeting the challenge of providing electricity access to the off-grid population, estimated to be around 1.2 billion residing across the globe with 300 million in India, in a sustainable way. Technological solutions developed around these energy challenges often involve thermal systems that convert heat available from sources like solar, biomass, geothermal or unused industrial processes into electricity. Conventional steam based thermodynamic cycle at distributed scale (< 1 MWe) suffers from low efficiency driving scientific research to develop new, scalable, efficient and economically viable power cycles. This PhD work conducts one such study which provides a database of thermal power blocks optimized for the lowest initial investment cost to developers of distributed power plants. The work is divided in two steps; a) feasibility study of various thermodynamic cycles for distributed power generation covering different operating temperature regimes and b) perform their detailed thermo-economic modelling for the heat sources mentioned above. Thermodynamic cycles are classified into three temperature domains namely, low (< 450 K), medium (< 600 K) and high (< 1000 K) T cycles. Any fluid whose triple point temperature is below the typical ambient temperatures is a potential working fluid in the power cycle. Most of the organic and the inorganic fluids satisfy this criterion and can be perceived as potential power cycle fluids. The general notion is that organic fluids are more suited for low or medium temperature cycles whereas inorganic fluids for high temperature ones. Organic fluids can further be classified into hydrofluorocarbon and hydrocarbon. While the former has high global warming potential (GWP), the latter is flammable in nature. Their mixture in certain compositions is found to obviate both the demerits and perform equally well on thermodynamic scales for low T cycles. On the similar lines, mixture of HCs and inorganic fluids, such as propane+CO2 and isopentane+CO2 are found to be more appropriate for medium T applications if the issues like pinch temperature in the regenerator arising due to temperature glide are taken care of. In the high temperature domain, high efficiency Brayton cycle (supercritical CO2) and transcritical condensing cycles are studied with the latter being 2 % more efficient than the former. However, application of the condensing cycle is limited to low temperature ambient locations owing to low critical temperature of CO2 (304 K). In the same cycle configuration, mixture of CO2 and propane (52 and 48%) with a critical temperature of ~ 320 K is observed to retain the thermodynamic performance with the increased heat rejection temperature matched to the tropical ambient conditions. However, these cycles are plagued by the high operating pressures (~300 bar) calling for high temperature steel making the power block uneconomical. In this regard, the advanced CO2 cycles are developed wherein the optimum operating pressures are limited to 150 bar with an increased cycle efficiency of 6 % over the S-CO2 cycle. Feasibility study carried out on these cycles in the Indian context indicates the low and medium T cycles to be better suited for distributed power generation over the high T cycles. In the second part of work, a comprehensive study is performed to optimize the low and the medium T cycles on a thermo-economic basis for the minimum specific investment cost ($/We). Such a study involves development of component level models which are then integrated to form the system of interest, thus, following a bottom-up approach. A major emphasis is given on the development of scroll expander and low cost pebble bed thermal energy storage system that are the reported in the literature as the areas with high uncertainties while connecting them to the system. Subsequently, the key design parameters influencing the specific cost of power from an air-cooled ORC are identified and used to formulate a 7-dimensional space to search for the minimum costs for applications with a) geothermal/waste or biogas heat sources and b) solar ORCs. Corresponding maps of operating parameters are generated to facilitate distributed power engineers in the design of economic systems within constraints such as available heat source temperatures, maximum expander inlet pressures imposed, etc. Further, the effect of power scaling on these specific costs is evaluated for ORC capacities between 5 and 500 kWe.

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賴元生. "A study on the thermal analysis and model of thermal transfer of multi-temperature energy storage materials." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/52570328883144183891.

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碩士
中國文化大學
材料科學與製造研究所
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The purpose of this research is to study and to develop a highly efficient multi-temperature logistic system with energy storage materials which can store or release thermal energy and in the mean time change their phase states at different temperatures over day and night. Moreover, this project can provide the database for design and manufacturing technologies with energy saving, low pollution and low cost of the multi-temperature logistic system. The energy storage materials which can release (or absorb) thermal energy during freezing (or melting), can be either phase change single-inorganic-component or multi- inorganic-components with large specific heat capacity, high heat transfer rate, desired transition temperature and repeatable usage. The durability test was set to fulfill the industrial requirement for the life time of those multi-temperature energy storage materials expected to be used over ten years or three thousands times. In this research, the eutectic property and heat capacity of the single- or multi-component inorganic phase change materials(ex. NaBr(aq), Na2CO3(aq), KCl(aq), NH4Cl(aq), Na2CO3．10H2O, Na2HPO4．12H2O, CaCl2．2H2O, Paraffin Wax, Ba(OH)2．8H2O, and Mg(NO3)2．6H2O) with the large latent heat and melting points between -35℃ ~ 90℃ were experimentally determined. The experimental operating parameters, such as the additive amounts of thickening agent, stability agent and nucleation agent were applied to prevent the subcooling phenomenon as well as the phase-separation. The measurement results about melting point, latent heat and eutectic components of energy storage materials experimentally analyzed by Differential Scanning Calorimetry (DSC) were used to design the energy storage logistic system. From the results, the energy saving performance under various operation conditions, the cold tank can be maintained at the temperature from -18℃ to 10℃ within 3~13 hours. The eutectic temperature of the energy storage materials does not change obviously under durability test. However, the latent heat started to decline with the increase of test cycle after testing several hundred cycles, due to the solvent leakage in DSC cell pan. The COSMOS Floworks simulations was used to search the optimal design baseline for the energy storage system and to setup the best operating parameters. To reduce the experimental cost, the best practical design and manufacturing parameters as well as the best operating parameters were studied through the comparison of simulation results with experimental results.

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Mohan, Gowtham. "Development of high-temperature sensible thermal energy storage systems for advanced concentrating solar power generation." Phd thesis, 2018. http://hdl.handle.net/1885/157319.

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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.

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Nikolakakis, Thomas. "A Mixed Integer Linear Unit Commitment and Economic Dispatch Model for Thermo-Electric and Variable Renewable Energy Generators With Compressed Air Energy Storage." Thesis, 2017. https://doi.org/10.7916/D8CN78M1.

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The objective of this PhD thesis is to create a Unit Commitment and Economic Dispatch (UCED) modelling tool that can used to simulate the deterministic performance of a power system with thermal and renewable generators and energy storage technologies. The model was formulated using mixed integer programing (MIP) on GAMS interface. A robust commercial solver by IBM (CPLEX) is used as solver. Emphasis on the development of the tool has been given on the following aspects. a) Technical impacts of Variable Renewable Energy (VRE) integration. The UCED model developed in this thesis is a high resolution short-term dispatch model. It captures the variability of VRE power on the intra-hour level. In addition the model considers a large number of important real world, system, unit and policy constraints. Detailed representation of a power system allows for a realistic estimation of maximum penetration levels of VRE and the related technical impacts like cycling of generators (part-loading and number of start-ups). b) CO2 emissions. High levels of VRE penetration can potentially increase consumption of fuel in thermal units per unit of electricity produced due to increased thermal cycling. The dispatch of units in the UCED model is based on minimizing system wide operational costs the most important of those being fuel, start-up costs and the cost of carbon. Fuel consumption is calculated using technical data from Input/Output curves of individual generators. The start-up cost is calculated based on times the generator units have been off and the energy requirement to bring the unit back to hot state. Thus dynamic changes on fuel consumption can be captured and reported. c) Technical solutions to facilitate VRE integration. VRE penetration can be facilitated if appropriate solutions are implemented. Energy storage is an effective way to reduce the impact of RE variability. The UCED model includes an integrated Mixed Integer Linear (MILP) compressed air energy storage (CAES) simulation sub-model. Unlike existing CAES models, the new “Thermo-Economic” (TE) CAES model developed in this thesis uses technical data from major CAES manufacturers to model the dynamic effect of cavern pressure on both the compression and expansion sides during CAES operation. More specifically the TE model takes into account that a) a compressor discharges at a pressure equal to the back-pressure developed in the cavern at each moment, b) the speed of charging can be regulated through inlet guide vanes; higher charging speed can take place at the expense of additional power consumption, c) the maximum power output during expansion can be limited by the levels of cavern pressure; there is a threshold pressure level below which the maximum output decreases linearly with pressure. Since it uses actual power curves to simulate CAES operation, the TE model can be assumed to be more accurate than conventional Fixed Parameter (FP) models that don’t model dynamic effects of cavern pressure on CAES operation. The TE model in this thesis is compared with conventional FP models using historical market prices from the Irish electricity market. The comparison was based on the ability of a CAES unit to arbitrage energy for making profit in the Irish electricity market. More specifically a “Base” scenario was created that included the operation of a 270MW CAES unit with technical characteristics obtained from a major CAES manufacturer and assumed discharge time of 13hr. Various sensitivities on discharge time, natural gas prices and system marginal prices (SMPs) were modeled. An additional scenario was created to show the benefit on CAES profitability if the unit participated in both the energy and ancillary services markets. All scenarios were modeled using both the TE and FP CAES models. The results showed that the most realistic TE model returns around 15% less profitability across more scenarios. The reduction in profitability grows to around 30% when the cavern volume (discharge time) is reduced to half (6 hours). The latter is related to the sensitivity of the TE model on cavern pressure that is being built faster when the volume is reduced. A CAES unit won’t get a positive net present value (NPV) in Ireland under any scenario unless SMPs are greatly increased. Thus, it was shown that that existing FP CAES models overestimate CAES profitability. More accurate models need to be used to estimate CAES profitability in deregulated markets. Additionally, it might deem necessary to create additional markets for energy storage units and increase the possible revenue sources and magnitude to facilitate an increase of storage capacity worldwide. The second step of analysis involved the integration of the CAES and UCED models. The UCED model developed in this thesis was validated and applied using data from the Irish grid, a power system with more than 50 thermal generators. A vast of existent data was used to create a mathematical model of the Irish system. Such data include technical specifications and variables of thermal generators, maintenance schedules and historical solar, wind and demand data. The validation exercise was deemed successful since the UCED model simulated utilization factors of 45 out of 52 generators with an absolute difference between modeled and actual results on utilization factors of less than 6% (the absolute differences are called Delta in this thesis). In addition the results of validation exercise were compared with the results of a similar exercise where PLEXOS was the modelling tool and it was found that the results of the two models were similar for the vast majority of generators. More specifically, the PLEXOS model results showed higher deltas for the coal-fired generators compared to the UCED model. On the other hand the UCED model, reported higher delta values for peat-fired generators. The results of the PLEXOS model were slightly better for the gas-fired generators while both models reported deltas nearly zero for all oil and distillate-fired generators. Finally the model was applied to study the benefits of energy storage in Ireland in 2020 when wind penetration is expected to reach 37% of total demand. The analysis involved the development of two groups of 3 scenarios each. In the first group the main scenario also called the “Reference” was used to simulate the short-term unit (30 min step) commitment within the Irish system without storage. The results of the reference scenario were compared with two additional scenarios that assumed the existence of one 270MW CAES unit in Northern Ireland by 2020 (again the first scenario involved the TE and the second the FP CAES model). The results showed –when using the TE model- that the inclusion of one 270MW CAES unit in AI can help reduce wind curtailment by 88GWh, CO2 emissions by 150,000 tonnes and system costs by € 6 million per year. If an FP model had been used instead the reductions would be: wind curtailment by 108GWh, CO2 emissions by 270,000 tonnes and annual system costs by €13 million. Two main conclusions can be obtained from the specific set of results. The first conclusion is that storage units have a financial benefit over the whole system. Thus, when a CAES unit operates to minimize the costs of the whole system can incur substantially more benefits compared to if the CAES unit operated to maximize the individual unit’s profits as in the case presented earlier. The benefits of storage over the whole system should be accounted to make policy decisions and create incentives for investors to increase energy storage capacity in national grids. The second important conclusion is that existing CAES FP models overestimate the ability of a CAES unit to facilitate VRE penetration. More accurate TE models should be used to assess a unit’s capability to increase system flexibility. A second group of scenarios was created to simulate the benefit of CAES at even higher VRE penetration levels. In the second group the “Reference” scenario again, assumed no storage however, wind production was increased by 25%. Again the “Reference” was compared with two additional scenarios that assumed integration of 3x270MW=810MW of storage capacity in AI (one scenario used the TE model and the other the FP). The results for the TE model show that each of the 3 CAES units reduces wind curtailment by 188,000MWh, total system costs by €29 million and CO2 emissions by 180,000 tonnes. The same reductions for the FP model are 217,000MWh of wind curtailment, €25.6 million on total system costs and 180,000 tonnes of CO2. Thus, the results of the second group of scenarios show that as the installed capacity of both CAES and wind increases in Ireland a) the system-wide benefits of CAES increase and b) the differences on results between the TE and FP models become much smaller.

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Lozano, Adolfo. "Analysis of a novel thermoelectric generator in the built environment." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4131.

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This study centered on a novel thermoelectric generator (TEG) integrated into the built environment. Designed by Watts Thermoelectric LLC, the TEG is essentially a novel assembly of thermoelectric modules whose required temperature differential is supplied by hot and cold streams of water flowing through the TEG. Per its recommended operating conditions, the TEG nominally generates 83 Watts of electrical power. In its default configuration in the built environment, solar-thermal energy serves as the TEG’s hot stream source and geothermal energy serves as its cold stream source. Two systems-level, thermodynamic analyses were performed, which were based on the TEG’s upcoming characterization testing, scheduled to occur later in 2011 in Detroit, Michigan. The first analysis considered the TEG coupled with a solar collector system. A numerical model of the coupled system was constructed in order to estimate the system’s annual energetic performance. It was determined numerically that over the course of a sample year, the solar collector system could deliver 39.73 megawatt-hours (MWh) of thermal energy to the TEG. The TEG converted that thermal energy into a net of 266.5 kilowatt-hours of electricity in that year. The second analysis focused on the TEG itself during operation with the purpose of providing a preliminary thermodynamic characterization of the TEG. Using experimental data, this analysis found the TEG’s operating efficiency to be 1.72%. Next, the annual emissions that would be avoided by implementing the zero-emission TEG were considered. The emission factor of Michigan’s electric grid, RFCM, was calculated to be 0.830 tons of carbon dioxide-equivalent (CO2e) per MWh, and with the TEG’s annual energy output, it was concluded that 0.221 tons CO2e would be avoided each year with the TEG. It is important to note that the TEG can be linearly scaled up by including additional modules. Thus, these benefits can be multiplied through the incorporation of more TEG units. Finally, the levelized cost of electricity (LCOE) of the TEG integrated into the built environment with the solar-thermal hot source and passive ground-based cold source was considered. The LCOE of the system was estimated to be approximately $8,404/MWh, which is substantially greater than current generation technologies. Note that this calculation was based on one particular configuration with a particular and narrow set of assumptions, and is not intended to be a general conclusion about TEG systems overall. It was concluded that while solar-thermal energy systems can sustain the TEG, they are capital-intensive and therefore not economically suitable for the TEG given the assumptions of this analysis. In the end, because of the large costs associated with the solar-thermal system, waste heat recovery is proposed as a potentially more cost-effective provider of the TEG’s hot stream source.
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