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Kolesnik, Lindgren Julian. "Aquifer Thermal Energy Storage : Impact on groundwater chemistry." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232110.
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Groundwater is potentially a useful source for storing and providing thermal energy to the built environment. In a nordic context, aquifer thermal energy storage, (ATES) has not been subject to a wider extent of research concerning environmental impact. This thesis intends to study the impact on groundwater chemistry from an ATES that has been operational since 2016 and is located in the northern part of Stockholm, on a glaciofluvial deposit called the Stockholm esker. Analysis of groundwater sampling included a period of 9 months prior to ATES operation as well as a 7 month period after operation and sampling was conducted in a group of wells in vicinity of the installation and within the system as ATES operation began. Means of evaluation constituted a statistical approach which included Kruskal-Wallis test by ranks, to compare the ATES wells with the wells in the surroundings and principal component analysis, (PCA), to study the chemical parameters that could be related to ATES. In addition, a geophysical survey comprising 2D-resistivity and induced polarization, (IP) was done to elucidate whether the origin of high salinity could be traced to nearby possible sources. The analysis was based on foremost the cycle of cold energy storage. The results showed large variations in redox potential, particularly at the cold wells which likely was due to the mixing of groundwater considering the different depths of groundwater being abstracted/injected from different redox zones. Arsenic, which has shown to be sensitive to high temperatures in other research showed a decrease in concentration compared to surrounding wells. There were found to be a lower specific conductivity and total hardness at the ATES well compared to their vicinity. That indicates that they are less subject to salinization and that no accumulation has occurred to date. It is evident that the environmental impact from ATES is governed by the pre-conditions in soil- and groundwater.
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Kolesnik, Lindgren Julian. "Aquifer Thermal Energy Storage : Impact on grondwater chemistry." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-241055.
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Groundwater is potentially a useful source for storing and providing thermal energy to the built environment. In a nordic context, aquifer thermal energy storage, (ATES) has not been subject to a wider extent of research concerning environmental impact. This thesis intends to study the impact on groundwater chemistry from an ATES that has been operational since 2016 and is located in the northern part of Stockholm, on a glaciofluvial deposit called the Stockholm esker. Analysis of groundwater sampling included a period of 9 months prior to ATES operation as well as a 7 month period after operation and sampling was conducted in a group of wells in vicinity of the installation and within the system as ATES operation began. Means of evaluation constituted a statistical approach which included Kruskal-Wallis test by ranks, to compare the ATES wells with the wells in the surroundings and principal component analysis, (PCA), to study the chemical parameters that could be related to ATES. In addition, a geophysical survey comprising 2D-resistivity and induced polarization, (IP) was done to elucidate whether the origin of high salinity could be traced to nearby possible sources. The analysis was based on foremost the cycle of cold energy storage. The results showed large variations in redox potential, particularly at the cold wells which likely was due to the mixing of groundwater considering the different depths of groundwater being abstracted/injected from different redox zones. Arsenic, which has shown to be sensitive to high temperatures in other research showed a decrease in concentration compared to surrounding wells. There were found to be a lower specific conductivity and total hardness at the ATES well compared to their vicinity. That indicates that they are less subject to salinization and that no accumulation has occurred to date. It is evident that the environmental impact from ATES is governed by the pre-conditions in soil- and groundwater.Grundvatten har förutsättningen att utgöra en värdefull resurs för att lagra och förse byggnader med termisk energi. I en nordisk kontext har termisk energilagring i akviferer, (ATES) inte varit föremål för någon bredare forskning angående miljöpåverkan. Denna uppsats syftar till att studera kemisk grundvattenpåverkan från ett ATES som togs i drift 2016 i norra Stockholm, i en isälvsavlagring vid namn Stockholmsåsen. Analysen omfattar grundvattenprovtagning 9 månader före ATES driften samt 7 månader efter driftstart och provtagningen genomfördes i ett antal brunnar i närheten av installationen samt i ATES systemet då driften startade. Utvärderingsmetoden bestod av ett statistiskt tillvägagångssätt och omfattade Kruskal-Wallis test by ranks, för att jämföra ATES brunnarna med omgivande brunnar och principal component analysis, (PCA), för att studera kemiska parametrar som kan kopplas till ATES. I tillägg genomfördes en geofysisk undersökning som omfattar 2D-resistivitet samt inducerad polarisation, (IP) för att klarlägga huruvida källan till den höga saliniteten kunde spåras. Analysen baseras på främst på cykeln då kyld energi lagras. Resultaten visar stor variation i redoxpotential, i synnerhet vid de kalla brunnarna vilket sannolikt beror på omblandning av grundvatten med tanke på en differens i djup som grundvattnet infiltrerar/pumpas från med tillhörande skillnad i redox zon. Arsenik vilket har visat sig känsligt för höga temperaturer i annan forskning visade minskade koncentrationer jämfört med omgivande brunnar. ATES brunnarna uppvisade även lägre specifik konduktivitet och totalhårdhet i jämförelse. Det pekar mot att brunnarna är mindre utsatta för salinitet och att ingen ackumulering har skett till dags dato. Det framgår tydligt att miljömässig påverkan från ATES styrs av grundförutsättningarna i mark och grundvatten.
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Allen, Diana M. "Steady-state and transient hydrologic, thermal and chemical modelling of a faulted carbonate aquifer used for aquifer thermal energy storage, Carleton University, Ottawa, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22158.pdf.
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Allen, Diana M. (Diana Margaret) Carleton University Dissertation Earth Sciences. "Steady-state and transient hydrologic, thermal and chemical modelling of a faulted carbonate aquifer used for Aquifer Thermal Energy Storage, Carleton University, Ottawa, Canada." Ottawa, 1996.
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Barrios, Rivero Matías. "EVALUATION OF AN AQUIFER THERMAL ENERGY STORAGE (ATES) SYSTEM FOR THE CITY HOSPITAL IN KARLSRUHE (GERMANY)." Thesis, Karlsruhe Institute of Technology (KIT), Institute of Applied Geosciences (AGW), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-267554.
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The objective of the present study is to evaluate the economic, technical and environmental feasibility of an Aquifer Thermal Energy Storage (ATES) system combined with groundwater heat pumps (GWHP) for providing space cooling and heating for the future surgery building at the city hospital in Karlsruhe. The base case system used as reference for comparison is a system similar to the one currently supplying space cooling from a GWHP system and space heating by the local district-heating network. In addition, two alternative systems were included in the analysis, an Absorption Chiller (AbC) and a Desiccative Evaporative Cooling (DEC) system, both fed from the district-heating network. The study shows that the ATES system combined with a GWHP system is the most environmentally and economically attractive system for the planned facility. The results for the AbC system and the DEC systems show a negative net present value, meaning that this alternative is economically unfeasible. Furthermore, the AbC system and the DEC system do not provide any environmental advantage, showing an annual increase in CO2 emissions compared to the base case. A similar system like the one already providing cooling to some of the facilities would have several advantages over these two alternatives. However, it cannot compete with the ATES system together with GWHP, which apart from providing cooling at slightly higher efficiencies than the base case also delivers heating at high efficiencies. Therefore, it offers great potential savings and also provides an annual reduction in green house gas emissions. Concerning the technical feasibility of the four studied systems, no obstacle or significant barrier could be identified yet.
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Fleuchaus, Paul [Verfasser], and P. [Akademischer Betreuer] Blum. "Global application, performance and risk analysis of Aquifer Thermal Energy Storage (ATES) / Paul Fleuchaus ; Betreuer: P. Blum." Karlsruhe : KIT-Bibliothek, 2020. http://d-nb.info/1212512456/34.
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Revholm, Johan. "Energisimulering av kvarteret Hästskon 9 och 12 med ombyggnad och termiskt akviferlager." Thesis, KTH, Uthålliga byggnadssystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124630.
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Detta examensarbete utreder lönsamheten i en systemlösning för termiskt akviferenergilager tillsammans med ny VVS-teknisk lösning i fastigheterna kv Hästskon 9 och 12 vid en föreslagen framtida helrenovering. Dessutom utreds förutsättningar för miljöklassning i energi- och miljöcertifieringssystemet Miljöbyggnad avseende energianvändning, dagsljuskomfort, solvärmelast och termisk komfort för om- och tillbyggnadsförslaget med målsättning på nivå GULD. Genom att utnyttja akviferen under fastigheterna kvarteret Hästskon 9 och 12 idag kan man åstadkomma mycket låg energianvändning med en säsongsenergiverkningsgrad via kylmaskiner för värme- och kylaförsörjning på 5,6. En LCC-kalkyl visar att det finns en energikostnadsbesparing för fastighetsägaren Vasakronan omkring 3,65 MSEK per år jämfört med dagens situation om den beskrivna akviferlösningen används. Det ger en återbetalningstid om cirka 4,5 år på investeringen som måste göras. Energiklassning i Miljöbyggnadssystemet för befintliga fastigheter är troligtvis möjlig utan andra åtgärder än akviferlagersystemet, men då med BRONS eller möjligtvis SILVER nivå. Vid ett framtida om- och tillbyggnadsförslag får fastighetsägaren cirka 13 000 m² ytterligare uthyrbar lokalyta för handelslokaler och kontor. Trots detta kan energianvändningen minska ännu mer tack vare en säsongsenergiverkningsgrad via kylmaskiner för värme- och kylaförsörjning på 7,0 då SEB:s datakylanläggning kvarstår med värmeåtervinning på fastigheternas värmesystem, värme- och kylsystem byggs om för låg värmebärartemperatur och hög köldbärartemperatur, luftbehandlingssystem optimeras för låg fläktelenergi och hög värmeåtervinningsgrad, glaslösningar väljs med hänsyn till begränsad solinstrålning och byggnadens klimatskärm tilläggsisoleras i viss omfattning. Energikostnadsbesparingen ökar då ytterligare framåt 4,8 MSEK per år jämfört med dagens situation. Även om SEB:s datakylanläggning faller bort vid en ombyggnad finns ändå möjligheten att självständigt försörja fastigheten med egenproducerad värme via ytterligare en värmepump, vilket avlägsnar beroendet av SEB IT:s datahall för värmeproduktion och ändå ger en energikostnadsbesparing på 4,25 MSEK per år jämfört med dagens situation. Vid en sådan lösning blir den specifika energianvändningen enligt BBR 2012:s definition endast cirka 30 kWh/m² Atemp, år. Denna siffra är mycket lägre än nybyggnadskraven i BBR 2012 och i klass med nyproducerade byggnader med borrhålsenergilager. Utifrån analysen av Miljöbyggnadssystemets indikatorer för energianvändning, solvärmelast, dagsljuskomfort och termisk komfort bedöms det möjligt att klassa kvarteret Hästskon 12 och 9 vid om- och tillbyggnad i klass GULD med vissa förändringar av om- och tillbyggnadsförslaget. För att uppnå klass GULD med hänsyn till dagsljuskomfort och solvärmelast krävs särskild anpassning av glasning på S-huset, M-husets fasad mot Malmskillnadsgatan, samt en stor ljusgård i H-huset för att släppa in tillräckligt mycket dagsljus samtidigt som man åstadkommer effektiv solavskärmning.This thesis investigates the viability of a system solution for aquifer thermal energy storage along with new HVAC technical solutions in real estates Hästskon 9 and 12 at a proposed future renovation. It also explores opportunities for certification in the Swedish energy and environmental certification system Miljöbyggnad (Environmental Building) regarding energy consumption, daylight comfort, solar heat load and thermal comfort for the renovation and extension proposal of Hästskon 12 with the goal of the GOLD level. By exploiting the aquifer in the properties Hästskon 9 and 12 today, very low energy consumption is achievable with seasonal energy efficiency via chillers for heating and cooling supply of 5.6. The LCC analysis shows that there are energy cost savings for property owner Vasakronan of about 3.65 million SEK per year compared to the current situation, if the described aquifer thermal energy storage solution is used. This gives a payback time of approximately 4.5 years in the investment to be made. Certification in the Miljöbyggnad system for existing buildings is probably possible with the aquifer thermal energy storage, but with BRONZE or possibly SILVER level. In the future refurbishment and extension proposal, the property owner adds about 13 000 m² of additional rentable commercial premises and offices. Nevertheless, the energy use of the properties decreases further owing to a seasonal energy efficiency via chillers for heating and cooling supply of 7.0 when the data centre refrigeration equipment for tenant SEB persists with heat recovery on the properties' heating systems, heating and cooling systems are adapted for low heat carrier temperature and high brine water temperature, ventilation systems are designed for low fan electricity demand and high heat recovery rate, glass solutions chosen are based on limited solar radiation and the building envelope is additionally insulated to some extent. Energy cost savings are furthered to 4.8 million SEK per year compared to the current situation. Even if the data centre refrigeration equipment for tenant SEB is closed down in a future refurbishment scenario, there is possibility to independently supply the property with its own heat produced by an additional heat pump, which removes the dependence of tenant SEB's data centre for heat supply and yet provides an energy saving of 4.25 million SEK per year compared the current situation. Such a solution will result in specific energy with the BBR 2012 (Swedish building regulations) definition of only about 30 kWh / m² Atemp, year. This figure is much lower than new construction requirements of BBR 2012 and on par with virgin buildings with borehole energy storage system. Based on the analysis of the Miljöbyggnad system indicators for energy, solar thermal load, daylight comfort and thermal comfort it is possible to certify Hästskon 12 and 9 in a future refurbishment and extension at GOLD level with some changes in the refurbishment proposal. In order to achieve GOLD level with respect to daylight comfort and solar heat load, special adaptation of the glazing on the S building, M building's facade facing Malmskillnadsgatan, and a large atrium in the H-building is required to let in enough natural light while still providing effective solar shading.
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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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Martin, Gregory D. "Aquifer underground pumped hydroelectric energy storage." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447687.
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Ranjith, Adam. "Thermal Energy Storage System Construction." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264530.
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In the framework of 2020 PUPM HEAT project three different types of thermal energy storage (TES) systems are being constructed and analyzed at a demonstration site set up at the power plant IREN in Moncalieri, Italy. KTH will assist this project by setting up a validation rig where three TES systems in smaller dimensions will be constructed and analyzed for its performance, to use as guideline for the demonstration site rig. The first TES system that is being constructed is the submerged parallel spiral heat exchanger which is a completely new version of latent heat storage to be tested. For this idea, parallel layers of spiral copper coils will fill up a tank shell which in turn will be filled with phase change material. By injecting high temperature heat transfer fluid, phase change material will change its state and energy will be stored in the system. When injecting low temperature heat transfer fluid, the energy will be extracted. This BSc thesis will present detailed design solutions for the tank shell and the spiral copper coils that will be used for the heat exchanger. Presented solutions are then used to order parts needed to initiate the construction phase.Inom ramverket för 2020 PUPM HEAT projektet kommer tre olika typer av värmeenergilagrings enheter tillverkas och analyseras vid energikraftverket IREN i Moncalieri, Italien. KTH kommer att assistera detta projekt genom att sätta upp en anläggning med tre liknande värmeenergilagrings enheter i mindre dimensioner som kommer konstrueras och analyseras. Dess data kommer sedan användas som riktlinje för att tillverka de större värmeenergilagringsenheterna i IREN. Den första enheten som tillverkas är en värmeväxlare som bygger på en ny version av latent energilagring. Den kommer att bestå av parallella lager av spiral formade koppar rör som fyller en tank. Tomrummet som blir över kommer att fyllas upp av fasändrings material (PCM). Genom att injicera varmt vatten i systemet kommer PCM:et att byta fas, vilket resulterar i att värmeenergin lagras i systemet. När sedan kallt vatten injiceras kan den sparade energin bli utvunnen. Den här rapporten kommer att presentera designen till tank kåpan såväl som den inre strukturen med kopparrör som behövs till värmeväxlaren. Resultatet ska möjliggöra beställning av alla delar som behövs för att konstruera värmeväxlaren.
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Bembry, Walter T. IV. "Emergency thermal energy storage: cost & energy analysis." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/13086.
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Master of ScienceDepartment of Mechanical Engineering
Donald Fenton
The need to store and access electronic information is growing on a daily basis as more and more people conduct business and personal affairs through email and the internet. To meet these demands, high energy density data centers have sprung up across the United States and around world. To ensure that vital data centers run constantly, proper cooling must be maintained to prevent overheating and possible server damage from occurring. Emergency cooling systems for such systems typically utilize traditional batteries, backup generator, or a combination thereof. The electrical backup provides enough power to support cooling for essential components within the data centers. While this method has shown to be reliable and effective, there are several other methods that provide reliable emergency cooling at a fraction of the cost. This paper address the lack of information regarding the initial, operation, and maintenance costs of using Thermal Energy Storage (TES) tanks for emergency cooling. From research and various field examples, five emergency cooling system layouts were designed for various peak cooling loads. Looking at the different cooling loads, components, and system operations an economic evaluation of the system over a 20 year period was conducted. The economic analysis included the initial and maintenance costs of each system. In an effort to better understand power consumption of such systems and to help designer’s better estimate the long term costs of TES tanks systems, five layouts were simulated through a program called TRNSYS developed for thermal systems. To compare against current systems in place, a benefit to cost ratio was done to analyze TES versus a comparable UPS. The five simulated systems were one parallel pressurized tank, one parallel and one series atmospheric tank, one parallel low temperature chilled water, and one series ice storage tank. From the analysis, the ice storage and pressurized systems were the most cost effective for 1 MW peak cooling loads. For 5 MW peak cooling loads the ice storage and chilled water systems were the most cost effective. For 15 MW peak loads the chilled water atmospheric TES tanks were the most cost effective. From the simulations we concluded that the pressurized and atmospheric systems consumed the least amount of power over a 24 hour period during a discharge and recharge cycle of the TES tank. From the TRNSYS simulations, the ice storage system consumed 22 – 25% more energy than a comparable chilled water system, while the low temperature storage system consumed 6 – 8% more energy than the chilled water system. From the benefit-cost-ratio analysis, it was observed that all systems were more cost effective than a traditional battery UPS system of comparable size. For the smaller systems at 1 MW the benefit-cost-ratio ranged between 0.25 to 0.55, while for larger systems (15 MW) the ratio was between 1.0 to 3.5 making TES tanks a feasible option for providing emergency cooling for large and small systems.
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Ohannessian, Roupen. "Thermal Energy Storage Potential in Supermarkets." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-140647.
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The objective of this research is to evaluate the potential of thermal energy storage in supermarkets with CO2 refrigeration systems. Suitable energy storage techniques are investigated and the seasonal storage technology of boreholes is chosen to be the focus of the study. The calculations are done for five supermarket refrigeration systems with different combinations of heating systems and borehole thermal energy storage control strategies. The two heating systems analyzed are the ground source heat pump and the heat recovery from the supermarket’s refrigeration system. The simulation results show that the introduction of thermal energy storage in the scenarios with heat pump can reduce the annual total energy by 6.3%. It is also shown that increasing the number of boreholes can decrease the life cycle cost of the system. Moreover, it is established that a supermarket system with heat recovery consumes 8.1% less energy than the one using heat pump and adding thermal energy storage on the heat recovery system further improves the energy consumption by 3.7% but may become costly.
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Berglund, Simon. "Rock cavern as thermal energy storage." Thesis, Luleå tekniska universitet, Energivetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79596.
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In the fall of 2019, a comprehensive idea study was conducted on heat storage in two rock caverns located at Näsudden in Skelleftehamn and was part of the project course "Energiteknik, huvudkurs" at Luleå University of Technology. This idea study investigated the conditions of using waste heat from Boliden AB:s copper smeltery (Rönnskär) and storing this waste heat in two rock caverns and use them as seasonal thermal storage tanks, with the purpose of using the heat in the nearby district heating network, thus replacing some of the oil burned at Rönnskär. To investigate this, the authors of the idea study looked at two different storage cycles of seasonal storage and modeled this in ANSYS Fluent to simulate the heat storage and the heat losses. The results from this idea study showed promising results for using these caverns as heat storage and this work is therefore a continuation of the idea study. Since the study provided a good understanding of the conditions for seasonal storage, some questions arose about how the rock caverns will behave during an intermittent operation, which is the planned mode of operating the caverns in case of deployment. In this thesis, intermittent operation of these caverns are explored and how this effects the temperature in the caverns and its surrondings, the charge/discharge speed, how insulated walls affect the operation and how much oil is replaced. At the beginning of this project a review of the idea study and similar projects was done to gain deeper knowledge about the subject, but also to get a wider grasp on the different problems that could arise during the thesis. Relevant data for the caverns was collected and acquired to get a deeper understanding of its geometry, layout and what kind of modifications are really possible. Further data from the district heating networks of Boliden AB and Skellefteå Kraft was acquired. The available waste heat from Rönnskär was examined and used to calculate the chargeable energy by hour for the caverns, with the limits of Skelleftehamn district heating network in mind. By examining the different steam boiler patterns, the discharge pattern could be calculated. Using CFD, the unknown global heat transfer coefficient between the cavern water and the cavern wall can be determined. This data was then used with a set of differential equations to model the behavior of the caverns in Simulink. This allowed to determine the behavior for the caverns during normal operation, such as how the heat losses evolve, how the temperatures fluctuate, how much heat the caverns can be charged with and how much they can discharge. The results from the simulations showed that the caverns discharge a higher amount of energy when operating intermittently than when operating seasonally. Depending on how the caverns are utilized, different amounts of discharged energy are obtained. This range from 2224,7MWh to 7846,1MWh for the different discharging patterns. The usage also affects the efficiency of the cavern giving the efficiency a range between 19% to 53,9%. The heat losses range from around 20kW to 1000kW, depending on operation. Insulating the cavern walls reduces on average the heat losses by a factor of 5. Operating the caverns intermittently would on average remove a total of 29 ktonne CO2 and 88,74 tonne NOx for its expected lifespan of 30 years. Economically, the rock caverns have good economic potential as they would save about 80 million SEK during their lifetime just from buying less oil.Hösten 2019 genomfördes en omfattande idéstudie om värmelagring i två bergrum vid Näsudden i Skelleftehamn och var en del av projektkursen "\textit {Energiteknik, huvudkurs}" vid Luleå tekniska universitet. Denna idéstudie undersökte villkoren för att använda spillvärme från Boliden AB:s kopparsmältverk (Rönnskär) och lagra denna värme i bergrummen och använda dem som säsongslagrade ackumulatortankar. Syftet med detta var att använda värmen i det närliggande fjärrvärmenätverket och därmed ersätta en del av den förbrända oljan hos Rönnskär. Författarna utforskade detta genom att undersöka två olika lagringscykler för säsongslagring och modellerade detta i ANSYS Fluent för att simulera värmelagring och värmeförluster. Resultaten från idéstudien visade lovande resultat för säsongsbaserad värmelagring i dessa bergrum och detta arbete är därför en fortsättning av idéstudien. Eftersom studien gav en god förståelse för förhållandena för säsongslagring, uppstod några frågor om hur bergrummen kommer att bete sig under en intermittent drift, vilket är den planerade driften av bergrummen vid en framtida användning. I detta projekt undersöks intermittent drift av dessa bergrum och hur detta påverkar temperaturen i bergrummen och dess omgivning, laddnings- / urladdningshastigheten, hur isolerade väggar påverkar driften och hur oljeförbrukningen reduceras. I början av detta projekt gjordes en genomgång av idéstudien och liknande projekt för att få djupare kunskap om ämnet, men också för att få ett bredare grepp om de olika problem som kan uppstå under arbetets gång. Relevant data för bergrummen samlades in och anskaffades för att få en djupare förståelse för dess geometri, layout och vilken typ av ändringar som verkligen är möjliga. Ytterligare data från fjärrvärmenätverket för Boliden AB och Skellefteå Kraft förvärvades. Den tillgängliga spillvärme från Rönnskär undersöktes och användes för att beräkna den urladdningsbara energin per timme för bergrummen, med begränsningarna i Skelleftehamns fjärrvärmenät i åtanke. Genom att undersöka de olika ångpannmönstren kan urladdningsmönstret beräknas. Med hjälp av CFD kan den okända globala värmeöverföringskoefficienten mellan bergrumsvattnet och bergväggen bestämmas. Denna data användes sedan med en uppsättning differentialekvationer för att modellera driften av bergrummen i Simulink. Detta gjorde det möjligt att bestämma beteendet för bergrummen under normal drift, till exempel hur värmeförlusterna utvecklas, hur temperaturen fluktuerar, hur mycket värme bergrummen kan laddas med och hur mycket de kan ladda ur. Resultaten från simuleringarna visade att bergrummen kan ladda ur en större mängd energi än vid en säsongsbetonad drift. Beroende på hur grottorna utnyttjas erhålls olika mängder urladdad energi. Detta sträcker sig från 2224,7MWh till 7846,1MWh för de olika urladdningsmönstren. Användningen påverkar också grottans effektivitet vilket ger en effektivitet mellan 19% och 53,9%. Värmeförlusterna sträcker sig från cirka 1000 kW till 20kw, beroende på drift. Isolering av bergväggarna minskar i genomsnitt värmeförlusten med en faktor 5. Att använda grottorna intermittent skulle i genomsnitt ersätta totalt 29 kton CO2 och 88,74 ton NOx för den förväntade livslängden på 30 år. Bergrummen har även god ekonomisk potential eftersom de skulle spara cirka 80 miljoner SEK under sin livstid bara från minskade oljekostnader.
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Ugur, Burcu. "Thermal Energy Storage in Adsorbent Beds." Thesis, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24362.
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Total produced energy in the world is mostly consumed as thermal energy which is used for space or water heating. Currently, more than 85% of total thermal energy consumption is supplied from fossil fuels. This high consumption rate increases the depletion risk of fossil fuels as well as causing a tremendous release of hazardous gases such as carbon dioxide, carbon monoxide, sulfur oxides, nitrogen oxides and particulate matter that effects both environment and human health. Those drawbacks force humankind to search for new technologies, like renewables, to reduce fossil fuel dependency on thermal energy production.
Thermal energy storage in adsorbent beds is one of the resulting technologies. Adsorption is an exothermic process in which a fluid (adsorbate) diffuses into the pores of a porous solid material (adsorbent) and trapped into the crystal lattice. In this system, exothermic adsorption of water vapor from air is carried out by using hybrid adsorbent of activated alumina and zeolite. In previous studies, through literature review, this adsorbent was selected to be the most efficient adsorbent for this process due to its high water adsorption capacity, high heat of adsorption, and stability [Dicaire and Tezel, 2011]. In this study, previous studies started on this project was confirmed and pursued by trying to increase the efficiency of the process and confirm the feasibility and applicability of this system in larger scales.
In this thesis, various zeolite and activated alumina hybrid adsorbents with varying zeolite compositions were screened to find the most efficient adsorbent for thermal energy storage process that gives the highest energy density. Then, existing small column was replaced with a new one, which is 16 times bigger in volume, in order to confirm the feasibility of this process at larger scales. Applicability of on-off heat release in adsorption process was also investigated by conducting several on-off experiments at different on-off time periods. Moreover, exothermic adsorption process was modeled by doing mass and energy balances in the column, water accumulation balance in the pellets, and energy balance in the column wall. Validity of this model was confirmed by comparing it with experimental results at different column volumes, and at different volumetric flow rates. Finally, an overall plant design, capital cost and thermal energy price estimations were done for adsorption thermal energy storage plants for different storage capacities and payback periods.
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Alfasfos, Rami. "Cavern Thermal Energy Storage for District Cooling. Feasibility Study on Mixing Mechanism in Cold Thermal Energy Storage." Thesis, KTH, Kraft- och värmeteknologi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-219932.
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Bugaje, Idris M. "Thermal energy storage in phase change materials." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335920.
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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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McTigue, Joshua. "Analysis and optimisation of thermal energy storage." Thesis, University of Cambridge, 2016. https://www.repository.cam.ac.uk/handle/1810/263019.
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The focus of this project is the storage of thermal energy in packed beds for bulk electricity storage applications. Packed beds are composed of pebbles through which a heat transfer fluid passes, and a thermodynamic model of the heat transfer processes within the store is described. The packed beds are investigated using second law analysis which reveals trade-offs between several heat transfer processes and the importance of various design parameters. Parametric studies of the reservoir behaviour informs the design process and leads to a set of design guidelines. Two innovative design features are proposed and investigated. These features are segmented packed beds and radial-flow packed beds respectively. Thermal reservoirs are an integral component in a storage system known as Pumped Thermal Energy Storage (PTES). To charge, PTES uses a heat pump to create a difference in internal energy between two thermal stores; one hot and one cold. The cycle reverses during discharge with PTES operating as a heat engine. The heat pumps/engines require compression and expansion devices, for which simple models are described and are integrated with the packed bed models. The PTES system behaviour is investigated with parametric studies, and alternative design configurations are explored. A multi-objective genetic algorithm is used to undertake thermo-economic optimisations of packed-bed thermal reservoirs and PTES systems. The algorithm generates a set of optimal designs that illustrate the trade-off between capital cost and round-trip efficiency. Segmentation is found to be particularly beneficial in cold stores, and can add up to 1% to the round-trip efficiency of a PTES system. On the basis of the assumptions made, PTES can achieve efficiencies and energy densities comparable with other bulk electricity storage systems. However, the round-trip efficiency is very sensitive to the efficiency of the compression–expansion system. For designs that utilised bespoke reciprocating compressors and expanders, PTES might be expected to achieve electricity-to-electricity efficiencies of 64%. However, using compression and expansion efficiencies typical of off-theshelf devices the round-trip efficiency is around 45%.
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Al, Edhari Ahmed J. "Thermal Energy Storage Using Natural Porous Media." Thesis, California State University, Fullerton, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10275441.
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Heat transfer and fluid flow through porous media have received great attention due to its wide applications in engineering fields, such as acoustics, filtrations, and thermal energy storage. Thermal energy storage (TES) is a technique to stock thermal energy for later use in many applications, such as district heating. TES is used to store solar thermal energy and excessive heat from non-natural sources to provide a reliable, stable, and cheap thermal energy. The present study considers a simple and inexpensive design which can easily be constructed using readily available porous media that are commonly found in nature. The applications of the present study can aid in decreasing the expenditures of heating spaces by reducing energy consumption and peak demand. The present study experimentally investigated the effect of grains size of used porous media (sand, gravel, and rocks) on the heat transfer through TES. Also, the experimental study was used to validate the numerical model which was implemented to investigate the effect of the design parameters, such as pipes burial depth and pipes spacing and the permeability of porous media, on the performance of TES during the charging and discharging processes. The present study showed that a shallow burial depth and placing pipes close together resulted in the maximized performance of TES. Moreover, the stored thermal energy can last longer during thermal discharging process when the used storage medium has low permeability. An experimental model can be used for future studies to optimize the performance during the discharging process to save time and money.
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Edwards, Jacob N. "Thermal energy storage for nuclear power applications." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/36238.
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Master of ScienceDepartment of Mechanical and Nuclear Engineering
Hitesh Bindra
Storing excess thermal energy in a storage media that can later be extracted during peak-load times is one of the better economical options for nuclear power in future. Thermal energy storage integration with light water-cooled and advanced nuclear power plants is analyzed to assess technical feasibility of different storage media options. Various choices are considered in this study; molten salts, synthetic heat transfer fluids, and packed beds of solid rocks or ceramics. In-depth quantitative assessment of these integration possibilities are then analyzed using exergy analysis and energy density models. The exergy efficiency of thermal energy storage systems is quantified based on second law thermodynamics. The packed bed of solid rocks is identified as one of the only options which can be integrated with upcoming small modular reactors. Directly storing thermal energy from saturated steam into packed bed of rocks is a very complex physical process due to phase transformation, two phase flow in irregular geometries and percolating irregular condensate flow. In order to examine the integrated physical aspects of this process, the energy transport during direct steam injection and condensation in the dry cold randomly packed bed of spherical alumina particles was experimentally and theoretically studied. This experimental setup ensures controlled condensation process without introducing significant changes in the thermal state or material characteristics of heat sink. Steam fronts at different flow rates were introduced in a cylindrical packed bed and thermal response of the media was observed. The governing heat transfer modes in the media are completely dependent upon the rate of steam injection into the system. A distinct differentiation between the effects of heat conduction and advection in the bed were observed with slower steam injection rates. A phenomenological semi-analytical model is developed for predicting quantitative thermal behavior of the packed bed and understanding physics. The semi-analytical model results are compared with the experimental data for the validation purposes. The steam condensation process in packed beds is very stable under all circumstances and there is no effect of flow fluctuations on thermal stratification in packed beds. With these experimental and analytical studies, it can be concluded that packed beds have potential for thermal storage applications with steam as heat transfer fluid. The stable stratification and condensation process in packed beds led to design of a novel passive safety heat removal system for advanced boiling water reactors.
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Basgall, Lance Edgar. "Thermal energy storage design for emergency cooling." Thesis, Kansas State University, 2010. http://hdl.handle.net/2097/4637.
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Master of ScienceDepartment of Mechanical and Nuclear Engineering
Donald L. Fenton
Emergency cooling systems are applied to any application where the loss of cooling results in damage to the product, loss of data, or equipment failure. Facilities using chilled water for cooling that experience an electrical power outage, even a small one, would cause the chiller to shut down for 20 minutes or more. If emergency cooling is not available, temperatures would continue to increase to dangerous levels, potentially damaging the facility. Examples of facilities that could be protected by having emergency cooling systems are data centers, hospitals, banks, control rooms, laboratories, clean rooms, and emergency shelters among others. This project addresses the current lack of information and methods needed to correctly design emergency cooling systems. Three application uses were investigated for the possible benefits of having emergency cooling systems. The software TRNSYS was used to simulate five typical emergency cooling systems for each of the three applications. The characteristics and differences of the systems developed from the simulations were then analyzed and documented. The five systems simulated include a pressurized chilled water tank (parallel), atmospheric chilled water tank (parallel and series), low temperature chilled water tank (parallel), and ice storage tank (series). Simulations showed that low temperature chilled water tanks were less stratified than regular chilled water tanks by approximately 10%. Simulations also showed that the differences between atmospheric and pressurized tanks were negligible. Each tank discharged energy in the same manner and managed to replenish itself in the same amount of time. Examination of the different system configurations showed that tanks in series with the thermal load have issues with recharging due to its inability to isolate itself from the thermal load. It was also observed that while low temperature chilled water and ice storage tanks had the potential of reducing the storage tank volume, the amount of time ragged cooling will last is decreased by at least a factor of two. The examination of the five systems produced the desired design methodologies needed to address the lack of information on emergency cooling systems. With the reported information designers can effectively engineer systems to meet their needs.
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Fredi, Giulia. "Multifunctional polymer composites for thermal energy storage and thermal management." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/265328.
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Thermal energy storage (TES) consists in storing heat for a later use, thereby reducing the gap between energy availability and demand. The most diffused materials for TES are the organic solid-liquid phase change materials (PCMs), such as paraffin waxes, which accumulate and release a high amount of latent heat through a solid-liquid phase change, at a nearly constant temperature. To avoid leakage and loss of material, PCMs are either encapsulated in inert shells or shape-stabilized with porous materials or a nanofiller network. Generally, TES systems are only a supplementary component added to the main structure of a device, but this could unacceptably rise weight and volume of the device itself. In the applications where weight saving and thermal management are both important (e.g. automotive, portable electronics), it would be beneficial to embed the heat storage/management in the structural components.
The aim of this thesis is to develop polymer composites that combine a polymer matrix, a PCM and a reinforcing agent, to reach a good balance of mechanical and TES properties. Since this research topic lacks a systematic investigation in the scientific literature, a wide range of polymer/PCM/reinforcement combinations were studied in this thesis, to highlight the effect of PCM introduction in a broad range of matrix/reinforcement combinations and to identify the best candidates and the key properties and parameters, in order to set guidelines for the design of these materials.
The thesis in divided in eight Chapters. Chapter I and II provide the introduction and the theoretical background, while Chapter III details the experimental techniques applied on the prepared composites. The results and discussion are then described in Chapters IV-VII. Chapter IV presents the results of PCM-containing composites having a thermoplastic matrix. First, polyamide 12 (PA12) was melt-compounded with either a microencapsulated paraffin (MC) or a paraffin powder shape-stabilized with carbon nanotubes (ParCNT), and these mixtures were used as matrices to produce thermoplastic laminates with a glass fiber fabric via hot-pressing. MC was proven more suitable to be combined with PA12 than ParCNT, due to the higher thermal resistance. However, also the MC were considerably damaged by melt compounding and the two hot-pressing steps, which caused paraffin leakage and degradation, as demonstrated by the relative enthalpy lower than 100 %. Additionally, the PCM introduction decreased the mechanical properties of PA12 and the tensile strength of the laminates, but for the laminates containing MC the elastic modulus and the strain at break were not negatively affected by the PCM. Higher TES properties were achieved with the production of a semi-structural composite that combined PA12, MC and discontinuous carbon fibers. For example, the composite with 50 wt% of MC and 20 wt% of milled carbon fibers exhibited a total melting enthalpy of 60.4 J/g and an increase in elastic modulus of 42 % compared to the neat PA. However, the high melt viscosity and shear stresses developed during processing were still responsible for a not negligible PCM degradation, as also evidenced by dynamic rheological tests. Further increases in the mechanical and TES properties were achieved by using a reactive thermoplastic matrix, which could be processed as a thermosetting polymer and required considerably milder processing conditions that did not cause PCM degradation. MC was combined with an acrylic thermoplastic resin and the mixtures were used as matrices to produce laminates with a bidirectional carbon fabric, and for these laminates the melting enthalpy increased with the PCM weight fraction and reached 66.8 J/g. On the other hand, the increased PCM fraction caused a rise in the matrix viscosity and so a decrease in the fiber volume fraction in the final composite, thereby reducing the elastic modulus and flexural strength. Dynamic-mechanical investigation evidenced the PCM melting as a decreasing step in ’; its amplitude showed a linear trend with the melting enthalpy, and it was almost completely recovered during cooling, as evidenced by cyclic DMA tests.
Chapter V presents the results of PCM-containing thermosetting composites. A further comparison between MC and ParCNT was performed in a thermosetting epoxy matrix. First, ParCNT was mixed with epoxy and the mixtures were used as matrices to produce laminates with a bidirectional carbon fiber fabric. ParCNT kept its thermal properties also in the laminates, and the melting enthalpy was 80-90 % of the expected enthalpy. Therefore, ParCNT performed better in thermosetting than in thermoplastic matrices due to the milder processing conditions, but the surrounding matrix still partially hindered the melting-crystallization process. Therefore, epoxy was combined with MC, but the not optimal adhesion between the matrix and the MC shell caused a considerable decrease in mechanical strength, as also demonstrated by the fitting with the Nicolais-Narkis and Pukanszky models, both of which evidenced scarce adhesion and considerable interphase weakness. However, the Halpin-Tsai and Lewis-Nielsen models of the elastic modulus evidenced that at low deformations the interfacial interaction is good, and this also agrees with the data of thermal conductivity, which resulted in excellent agreement with the Pal model calculated considering no gaps at the interface. These epoxy/MC mixtures were then reinforced with either continuous or discontinuous carbon fibers, and their characterization confirmed that the processing conditions of an epoxy composite are mild enough to preserve the integrity of the microcapsules and their TES capability. For continuous fiber composites, the increase in the MC fraction impaired the mechanical properties mostly because of the decrease in the final fiber volume fraction and because the MC phase tends to concentrate in the interlaminar region, thereby lowering the interlaminar shear strength. On the other hand, a small amount of MC enhanced the mode I interlaminar fracture toughness (Gic increases of up to 48 % compared to the neat epoxy/carbon laminate), as the MC introduced other energy dissipation mechanisms such as the debonding, crack deflection, crack pinning and micro-cracking, which added up to the fiber bridging.
Chapter VI introduces a fully biodegradable TES composite with a thermoplastic starch matrix, reinforced with thin wood laminae and containing poly(ethylene glycol) as the PCM. The wood laminae successfully acted as a multifunctional reinforcement as they also stabilized PEG in their inner pores (up to 11 wt% of the whole laminate) and prevent its leakage. Moreover PEG was proven to increase the stiffness and strength of the laminate, thereby making the mechanical and TES properties synergistic and not parasitic.
Finally, Chapter VII focused on PCM microcapsules. The synthesis of micro- and nano-capsules with an organosilica shell via a sol-gel approach clarified that the confinement in small domains and the interaction with the shell wall modified the crystallization behavior of the encapsulated PCM, as also evidenced by NMR and XRD studies and confirmed by DSC results. In the second part of Chapter VII, a coating of polydpamine (PDA) deposited onto the commercial microcapsules MC. The resulting PDA coating was proven effective to enhance the interfacial adhesion with an epoxy matrix, as evidenced by SEM micrographs. XPS demonstrated that the PDA layer was able to react with oxirane groups, thereby evidencing the possibility of forming covalent bond with the epoxy matrix during the curing step.
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Renaldi, Renaldi. "Modelling and optimisation of energy systems with thermal energy storage." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31214.
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One of the main challenges in the implementation of renewable energy is the mismatch between supply and demand. Energy storage has been identified as one of the solutions to the mismatch problem. Among various storage technologies, thermal energy storage (TES) is foreseen to have a significant role to achieve a low carbon energy systems because of the large share of thermal energy demand and its relatively low cost. However, integrating TES into energy systems requires careful design and implementation since otherwise potential financial and environmental savings may not be achieved. Computational-based design tools are ubiquitous in the design process of modern energy systems and can be broadly categorised into two methodologies: optimisation and simulation. In both cases, designing an energy system with storage technology is significantly more complicated than those without, mainly due to the coupling of variables between time steps. This thesis is concerned with two facets of the application of TES in energy systems. First, the role of TES in improving the performance of renewable-based domestic heating systems. Second, the implementation of optimisation and simulation tools in the design of energy systems with integrated TES. They are addressed by examining two case studies that illustrate the spatial and temporal variance of energy systems: a single dwelling heat pump system with a hot water tank, and a solar district heating system with a borehole thermal energy storage. In the single dwelling case study, the technical and financial benefits of TES installation in a heat pump system are illustrated by the optimisation model. A simulation model which utilises the optimisation results is developed to assess the accuracy of the optimisation results and the potential interaction between the two methodologies. The solar district heating case study is utilised to highlight the potential of a time decomposition technique, the multiple time grids method, in reducing the computational time in the operational optimisation of the system. Furthermore, the case study is also employed to illustrate the potential of installing a similar system in the UK. The latter study was performed by developing a validated simulation model of the solar district heating system. The findings of the analyses reported in this thesis exemplify the potential of TES in a domestic and community-level heating system in the UK. They also provide a basis for recommendations on the improved use of optimisation and simulation tools in the design process of energy systems.
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Meroueh, Laureen. "Electrically charged thermal energy storage systems for grid-level electricity storage." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115660.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 155-171).
Unlike most other commodities, electricity produced at any given time must match the electricity being consumed or the stability of the electric grid is jeopardized. Electricity demand changes throughout the day result in required generation ramp-ups that strain power plants, reduce cycle efficiency and increase CO2 emissions. This problem is exacerbated when renewable sources such as wind and solar are integrated into the grid, due to their intermittency. A change in methods of energy production globally that allows synergistic coupling of renewable and fossil fuels is needed. Currently, pumped hydroelectric and compressed air energy storage are the two most common methods of storage, but are highly geographic dependent systems and thus of limited applicability. There exists a strong demand for grid-scale energy storage that are cost-effective and without geographic constraints. In this thesis, storage systems that are charged by electricity and discharged to produce electricity at times of high demand, are theoretically evaluated. Various types of storage such as chemical, thermal, and mechanical, are reviewed to determine the most ideal method for grid-level energy storage. Thermal energy storage systems using phase change materials are most attractive on a cost and energy density basis. Two system designs are evaluated that can couple to both existing and future power plants since they are electrically charged, via joule heating for example, and later discharged to produce electricity using the plant's turbomachinery. Described within is a novel system in which silicon is used as the storage medium and energy release is predominantly through radiative heat transfer. Another design based on the eutectic alloy Al0.88 Si0.12 and other sensible energy storage materials is also evaluated. As an example, the energy storage systems are coupled to a power plant operating according to a supercritical Rankin cycle, and their performance is compared to that of a boiler. Additionally, system cost is compared to existing storage technologies. Although storing electricity as heat and back to electricity is thermodynamically unfavorable, we present an analysis to show that this approach can be cost competitive and provides a segue from fossil fuels to renewable energy.
by Laureen Meroueh.
S.M.
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Arnold, David. "Thermal characteristics of encapsulated ice storage." Thesis, Cranfield University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280954.
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Tarragona, Roig Joan. "Smart control techniques for thermal energy storage systems." Doctoral thesis, Universitat de Lleida, 2021. http://hdl.handle.net/10803/671420.
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Augmentar l’ús d’energia provinent de fonts renovables és important en la lluita contra el canvi climàtic. No obstant, la seva implantació planteja reptes importants deguts a la manca de continuïtat en la seva generació i al desajust que existeix amb els perfils de consum. La present tesi doctoral s’emmarca en dues propostes per incrementar el rendiment dels panells fotovoltaics en l’àmbit dels sistemes de calefacció per edificis. Per una banda, el sistema integra un tanc d'emmagatzematge d'energia tèrmica, que permet emmagatzemar l'energia generada pels panells durant el dia, a fi de poder-la consumir a les hores amb més demanda. D'altra banda, el sistema també compta amb una estratègia de control predictiu, que permet pronosticar les condicions meteorològiques i les demandes de calefacció futures, per tal d'ajustar el funcionament de tot el conjunt d'elements, considerant aquesta informació. El sistema proposat ha demostrat ser efectiu en diferents tipus de clima i habitatges.Aumentar el uso de energía procedente de fuentes renovables es importante en la lucha contra el cambio climático. No obstante, su implantación plantea retos importantes debidos a la falta de continuidad en su generación y al desajuste que existe con los perfiles de consumo. La presente tesis doctoral se enmarca en dos propuestas para incrementar el rendimiento de los paneles fotovoltaicos en el ámbito de los sistemas de calefacción para edificios. Por un lado, el sistema integra un tanque de almacenaje de energía térmica, que permite almacenar la energía generada por los paneles durante el día, a fin de poderla consumir a las horas con más demanda. Por otro lado, el sistema también cuenta con una estrategia de control predictivo, que permite pronosticar las condiciones meteorológicas y las demandas de calefacción futuras, para ajustar el funcionamiento de todo el conjunto de elementos, considerando esta información. El sistema propuesto demostró ser efectivo en distintos tipos de climas y viviendas.
To increase the use of energy that comes from renewables is important to fight against climate change. However, their deployment leads to significant challenges due to the intermittence in their generation and the mismatch between energy demand and supply. In that sense, this PhD thesis is framed in two proposals to increase the performance of photovoltaic panels in heating systems integrated in the building sector. On the one hand, the system considers a thermal energy storage tank, which allows to store the energy produced by the panels during the solar hours, in order to consume it along the peak demand periods. On the other hand, the system also takes into account a model predictive control strategy, which enables to forecast weather conditions and future heating demands, to adjust the operation of all the elements. The proposed system demonstrated a good and effective behaviour in different climate conditions and buildings.
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Al-Mosawi, Alaa Liaq Hashem. "Thermal energy storage for building-integrated photovolaic components." Thesis, University of Strathclyde, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549422.
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Kotze, Johannes Paulus. "Thermal energy storage in metallic phase change materials." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96049.
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Thesis (PhD) -- Stellenbosch University, 2014.ENGLISH ABSTRACT: Currently the reduction of the levelised cost of electricity (LCOE) is the main goal of concentrating solar power (CSP) research. Central to a cost reduction strategy proposed by the American Department of Energy is the use of advanced power cycles like supercritical steam Rankine cycles to increase the efficiency of the CSP plant. A supercritical steam cycle requires source temperatures in excess of 620°C, which is above the maximum storage temperature of the current two-tank molten nitrate salt storage, which stores thermal energy at 565°C. Metallic phase change materials (PCM) can store thermal energy at higher temperatures, and do not have the drawbacks of salt based PCMs. A thermal energy storage (TES) concept is developed that uses both metallic PCMs and liquid metal heat transfer fluids (HTF). The concept was proposed in two iterations, one where steam is generated directly from the PCM – direct steam generation (DSG), and another where a separate liquid metal/water heat exchanger is used – indirect steam generation, (ISG). Eutectic aluminium-silicon alloy (AlSi12) was selected as the ideal metallic PCM for research, and eutectic sodium-potassium alloy (NaK) as the most suitable heat transfer fluid. Thermal energy storage in PCMs results in moving boundary heat transfer problems, which has design implications. The heat transfer analysis of the heat transfer surfaces is significantly simplified if quasi-steady state heat transfer analysis can be assumed, and this is true if the Stefan condition is met. To validate the simplifying assumptions and to prove the concept, a prototype heat storage unit was built. During testing, it was shown that the simplifying assumptions are valid, and that the prototype worked, validating the concept. Unfortunately unexpected corrosion issues limited the experimental work, but highlighted an important aspect of metallic PCM TES. Liquid aluminium based alloys are highly corrosive to most materials and this is a topic for future investigation. To demonstrate the practicality of the concept and to come to terms with the control strategy of both proposed concepts, a storage unit was designed for a 100 MW power plant with 15 hours of thermal storage. Only AlSi12 was used in the design, limiting the power cycle to a subcritical power block. This demonstrated some practicalities about the concept and shed some light on control issues regarding the DSG concept. A techno-economic evaluation of metallic PCM storage concluded that metallic PCMs can be used in conjunction with liquid metal heat transfer fluids to achieve high temperature storage and it should be economically viable if the corrosion issues of aluminium alloys can be resolved. The use of advanced power cycles, metallic PCM storage and liquid metal heat transfer is only merited if significant reduction in LCOE in the whole plant is achieved and only forms part of the solution. Cascading of multiple PCMs across a range of temperatures is required to minimize entropy generation. Two-tank molten salt storage can also be used in conjunction with cascaded metallic PCM storage to minimize cost, but this also needs further investigation.
AFRIKAANSE OPSOMMING: Tans is die minimering van die gemiddelde leeftydkoste van elektrisiteit (GLVE) die hoofdoel van gekonsentreerde son-energie navorsing. In die kosteverminderingsplan wat voorgestel is deur die Amerikaanse Departement van Energie, word die gebruik van gevorderde kragsiklusse aanbeveel. 'n Superkritiese stoom-siklus vereis bron temperature hoër as 620 °C, wat bo die 565 °C maksimum stoor temperatuur van die huidige twee-tenk gesmelte nitraatsout termiese energiestoor (TES) is. Metaal fase veranderingsmateriale (FVMe) kan termiese energie stoor by hoër temperature, en het nie die nadele van soutgebaseerde FVMe nie. ʼn TES konsep word ontwikkel wat gebruik maak van metaal FVM en vloeibare metaal warmteoordrag vloeistof. Die konsep is voorgestel in twee iterasies; een waar stoom direk gegenereer word uit die FVM (direkte stoomopwekking (DSO)), en 'n ander waar 'n afsonderlike vloeibare metaal/water warmteruiler gebruik word (indirekte stoomopwekking (ISO)). Eutektiese aluminium-silikon allooi (AlSi12) is gekies as die mees geskikte metaal FVM vir navorsingsdoeleindes, en eutektiese natrium – kalium allooi (NaK) as die mees geskikte warmteoordrag vloeistof. Termiese energie stoor in FVMe lei tot bewegende grens warmteoordrag berekeninge, wat ontwerps-implikasies het. Die warmteoordrag ontleding van die warmteruilers word aansienlik vereenvoudig indien kwasi-bestendige toestand warmteoordrag ontledings gebruik kan word en dit is geldig indien daar aan die Stefan toestand voldoen word. Om vereenvoudigende aannames te bevestig en om die konsep te bewys is 'n prototipe warmte stoor eenheid gebou. Gedurende toetse is daar bewys dat die vereenvoudigende aannames geldig is, dat die prototipe werk en dien as ʼn bevestiging van die konsep. Ongelukkig het onverwagte korrosie die eksperimentele werk kortgeknip, maar dit het klem op 'n belangrike aspek van metaal FVM TES geplaas. Vloeibare aluminium allooie is hoogs korrosief en dit is 'n onderwerp vir toekomstige navorsing. Om die praktiese uitvoerbaarheid van die konsep te demonstreer en om die beheerstrategie van beide voorgestelde konsepte te bevestig is 'n stoor-eenheid ontwerp vir 'n 100 MW kragstasie met 15 uur van 'n TES. Slegs AlSi12 is gebruik in die ontwerp, wat die kragsiklus beperk het tot 'n subkritiese stoomsiklus. Dit het praktiese aspekte van die konsep onderteken, en beheerkwessies rakende die DSO konsep in die kollig geplaas. In 'n tegno-ekonomiese analise van metaal FVM TES word die gevolgtrekking gemaak dat metaal FVMe gebruik kan word in samewerking met 'n vloeibare metaal warmteoordrag vloeistof om hoë temperatuur stoor moontlik te maak en dat dit ekonomies lewensvatbaar is indien die korrosie kwessies van aluminium allooi opgelos kan word. Die gebruik van gevorderde kragsiklusse, metaal FVM stoor en vloeibare metaal warmteoordrag word net geregverdig indien beduidende vermindering in GLVE van die hele kragsentrale bereik is, en dit vorm slegs 'n deel van die oplossing. ʼn Kaskade van verskeie FVMe oor 'n reeks van temperature word vereis om entropie generasie te minimeer. Twee-tenk gesmelte soutstoor kan ook gebruik word in samewerking met kaskade metaal FVM stoor om koste te verminder, maar dit moet ook verder ondersoek word.
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Darkwa, K. "Thermal energy storage (TES) systems involving thermochemical reactions." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309836.
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Cho, Eugene N. (Eugene Nammyoung). "Understanding and engineering azobenzene for thermal energy storage." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111320.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 135-146).
This thesis focuses on the understanding and engineering of a molecule known as azobenzene which holds unique properties for thermal storage applications. The azobenzene molecule undergoes structural change into a metastable state which has the ability to store energy. This thesis utilizes the energy storage and structural change properties of this molecule to develop new materials for thermal energy storage. The first is through a concept called solar thermal fuel which is storing the solar energy in rearranged bonds of the azobenzene and later releasing that energy in the form of heat. The second approach is through the structural property difference of its two states in order to moderate the phase change temperature of organic phase change materials. Essentially, the molecule azobenzene was modified and engineered to be used as a thermal battery as well as to mediate thermal energy storage in other materials. The first chapter will give a brief introduction on the concept and past examples of solar thermal fuel. Chapter 2, 3, 4 will discuss about the development of solar thermal fuel while chapter 5 discusses about a recently developed concept of using azobenzene to moderate phase change temperature. Chapter 2 shows the first demonstration of using solar thermal fuel in the solid state through functionalizing azobenzene on a polymer template. The polymer platform allows fabrication of a thin film of this material which enabled charging, discharging, and heat release using optically chargeable molecules all within the solid-state. A demonstration of solid state application was shown by constructing a macroscopic device which resulted in heat release bringing a temperature increase of as high as 10 OC. Next in chapter 3, azobenzene was engineered on the molecular lever with bulky aromatic groups (phenyl, biphenyl, and tert-butyl phenyl groups). The molecules were designed and synthesized for the purpose of increasing energy stored while promoting solid state solar thermal fuels. The design allowed fabrication of molecular based thin film, which was able to be charged with light, a great improvement from the original azobenzene, which crystallized preventing switching in the solid state. Molecular engineering proved to be a powerful and effective method in improving other solar thermal fuel properties, such as energy storage in STFs, chargeability, and also the thermal stability of the molecular thin film. In chapter 4, new diacetylene derivatives with azobenzene moieties and with varied alkyl spacers and linkers were synthesized to show photocontrolled self-assembly and disassembly of photon energy storage materials. This azobenzene decorated diacetylenes not only allowed solar energy storage but also demonstrated phase change characteristic of organic materials can be a parameter to consider in terms of designing high energy density photon energy storage materials. Chapter 5 discusses azobenzene based dopants in organic phase change material to photomoderate the phase change temperature. Three different types, 8 in total, organic phase change materials were tested to show the possibilty of this concept in a wide variety of phase change materials. A deep understanding was developed giving parameters to achieve a large phase change temperature difference in the organic phase change materials using the structual difference of the trans and the cis state of azobenzene.
by Eugene N. Cho.
Ph. D.
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Amy, Caleb(Caleb A. ). "Thermal energy grid storage : liquid containment and pumping." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/128992.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 149-158).
As the cost of renewable energy falls below fossil fuels, the key barrier to widespread sustainable electricity has become availability on demand. Energy storage can enable dispatchable renewables, but only with drastic cost reductions compared to current batteries. In this thesis, I investigate an electricity storage concept that stores electricity as sensible heat in an extremely hot liquid (>2000°C) and uses multi-junction photovoltaics (MPV) as a heat engine to convert it back to electricity on demand hours, or days, later. In addition to a technoeconomic analysis, this thesis focuses experimentally on heating, liquid containment, and pumping. The transfer of the storage liquid is key because it enables conversion to and from electricity and compact, efficient heat transfer. However, operating at these extreme temperatures introduces many practical challenges, so several novel solutions related to containment and pumping are investigated including high-performance heaters, sealing a large multi-part tank with affordable materials, and pumping above 2000°C. The key result is that although affordable silicon can be contained in affordable graphite and pumped at these temperatures, temperature variation in the system causes it the graphite infrastructure to rapidly dissolve and ultimately fail in a matter of hours. Alternative embodiments are proposed with recommendations on areas of future work. The key takeaway from the technoeconomic modeling is that integrating low-cost thermal storage with an inexpensive heat engine can enable an economical approach to electricity storage, even without high round trip efficiencies. Thus, despite the challenges, future work is warranted.
by Caleb Amy.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Sweet, Marshall. "Numerical Simulation of Underground Solar Thermal Energy Storage." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2322.
Full textAbstract:
The United States Department of Energy indicates that 97% of all homes in the US use fossil fuels either directly or indirectly for space heating. In 2005, space heating in residential homes was responsible for releasing approximately 502 million metric tons of carbon dioxide into the atmosphere. Meanwhile, the Sun provides the Earth with 1000 watts per square meter of power everyday. This document discusses the research of modeling a system that will capture and store solar energy during the summer for use during the following winter. Specifically, flat plate solar thermal collectors attached to the roof of a single family home will collect solar thermal energy. The thermal energy will then be stored in an underground fabricated Seasonal Solar Thermal Energy Storage (SSTES) bed. The SSTES bed will allow for the collected energy to supplement or replace fossil fuel supplied space heat in typical single family homes in Richmond, Virginia. TRNSYS is a thermal energy modeling software package that was used to model and simulate the winter thermal load of a typical Richmond home. The simulated heating load was found to be comparable to reported loads for various home designs. TRNSYS was then used to simulate the energy gain from solar thermal collectors and stored in an underground, insulated, vapor proof SSTES bed filled with sand. Combining the simulation of the winter heat demand of typical homes and the SSTES system showed reductions in fossil fuel supplied space heating in excess of 64%.
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Jaconelli, Livio, and Anton Pettersson-Thurfjell. "Numerical Verification of Mobile Thermal Energy Storage Performance." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-216157.
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Sözen, Zeki Ziya. "Thermal energy storage by agitated capsules of phase change material." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25974.
Full textAbstract:
Thermal energy storage via the latent heat of suitable phase change materials has the advantages of higher energy storage density and relatively isothermal behaviour compared to sensible heat storage systems. Glauber's salt (Na₂S0₄∙10H₂0) is one of the most extensively studied phase change materials for solar energy systems because of its low price, suitable phase change temperature and high latent heat. However, segregation due to incongruent melting behaviour leading to loss in the heat storage efficiency upon repeated melting-freezing cycling is a serious problem which has severely limited application of Glauber's salt. In this study Glauber's salt was encapsulated in 25 mm diameter hollow spheres and agitated in different systems including a liquid fluidized bed, rotating drum and rotating tube to reduce or eliminate the Toss in its heat storage efficiency. The encapsulated mixture consisted of 96% Glauber's salt and 4% borax by weight with 5% by volume air space in the capsules. Some capsules containing 25%, 15% and 5% by weight excess sodium sulfate and 10% by weight excess water were also prepared, to test the effect of sodium sulfate concentration under different agitation conditions.
The heat storage capacity of 5756 capsules, agitated by fluidizing with water in a pilot plant size (0.34 m diameter) column, showed a decrease over the first three cycles to about 60% of that theoretically possible, but there was no further decrease over the next 93 cycles under fluidization conditions. The heat storage efficiency was found to be improved by increasing the superficial water velocity and by decreasing the cooling rate. Heating rate had little or no effect. The fluidized capsules provide enhanced heat transfer rates to or from the heat storage medium, enabling the energy to be charged or discharged in about one hour with realistic inlet and outlet temperatures. The high heat transfer rates are an important advantage for the system and may open new areas of applications for thermal energy storage by encapsulated phase change material. Economic analysis of the liquid fluidized bed heat storage system shows that operating costs are almost negligible compared to fixed capital costs.
The heat storage efficiency of capsules decreased to 38.4% of the theoretical capacity or 67% of the corresponding agitated (fluidized) system in only 7 cycles under fixed bed conditions, and the efficiency decreased with further cycling. 97.5% of the original heat storage-capacity was recovered within three cycles when these capsules were refluidized.
Performances of the regular and different composition capsules were tested in the rotating tube, with rotation around a fixed horizontal axis passing through the capsules' centers, and in the rotating drum, with impact due to collisions in addition to rotation. The results showed that full rotation of a capsule around a horizontal axis improves the heat storage efficiency. However, full recovery of the theoretical capacity was not possible, even under vigorous mixing conditions. The efficiencies in the rotating tube were similar to those in the rotating drum for capsules subject to the same number of rotations around a horizontal axis. At high rotation speeds centrifugal force had a negative influence, especially in the rotating tube. On the basis of heat storage capacity per unit volume or weight of phase change material, 47% by weight sodium sulfate concentration was found to be optimal for the rotating drum and the rotating tube cases.
Some small scale experiments were performed to determine the relative importance of different factors in the loss of heat storage capacity. Sodium sulfate concentration gradients in the capsules with different thermal cycling histories were found by thermogravimetric analysis. The results showed that bulk segregation of anhydrous sodium sulfate is not the only reason for the loss of heat storage capacity in systems using Glauber's salt. Microencapsulation of anhydrous sodium sulfate beneath a layer of Glauber's salt crystals is at least as important.
Experiments to determine the degree of subcooling, believed to be another factor in the loss of heat storage capacity, showed that a mixture of 96% Glauber's salt and 4% borax by weight undergoes subcooling of about 5 K in gently agitated capsules. Nucleation and crystallization temperatures both increase with increased agitation.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Heier, Johan. "Energy Efficiency through Thermal Energy Storage : Possibilities for the Swedish Building Stock." Licentiate thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118734.
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The need for heating and cooling in buildings constitutes a considerable part of the total energy use in a country and reducing this need is of outmost importance in order to reach national and international goals for reducing energy use and emissions. One important way of reaching these goals is to increase the proportion of renewable energy used for heating and cooling of buildings. Perhaps the largest obstacle with this is the often occurring mismatch between the availability of renewable energy and the need for heating or cooling, hindering this energy to be used directly. This is one of the problems that can be solved by using thermal energy storage (TES) in order to save the heat or cold from when it is available to when it is needed. This thesis is focusing on the combination of TES techniques and buildings to achieve increased energy efficiency for heating and cooling. Various techniques used for TES as well as the combination of TES in buildings have been investigated and summarized through an extensive literature review. A survey of the Swedish building stock was also performed in order to define building types common in Sweden. Within the scope of this thesis, the survey resulted in the selection of three building types, two single family houses and one office building, out of which the two residential buildings were used in a simulation case study of passive TES with increased thermal mass (both sensible and latent). The second case study presented in the thesis is an evaluation of an existing seasonal borehole storage of solar heat for a residential community. In this case, real measurement data was used in the evaluation and in comparisons with earlier evaluations. The literature reviews showed that using TES opens up potential for reduced energy demand and reduced peak heating and cooling loads as well as possibilities for an increased share of renewable energy to cover the energy demand. By using passive storage through increased thermal mass of a building it is also possible to reduce variations in the indoor temperature and especially reduce excess temperatures during warm periods, which could result in avoiding active cooling in a building that would otherwise need it. The analysis of the combination of TES and building types confirmed that TES has a significant potential for increased energy efficiency in buildings but also highlighted the fact that there is still much research required before some of the technologies can become commercially available. In the simulation case study it was concluded that only a small reduction in heating demand is possible with increased thermal mass, but that the time with indoor temperatures above 24 °C can be reduced by up to 20%. The case study of the borehole storage system showed that although the storage system worked as planned, heat losses in the rest of the system as well as some problems with the system operation resulted in a lower solar fraction than projected. The work presented within this thesis has shown that TES is already used successfully for many building applications (e.g. domestic hot water stores and water tanks for storing solar heat) but that there still is much potential in further use of TES. There are, however, barriers such as a need for more research for some storage technologies as well as storage materials, especially phase change material storage and thermochemical storage.Behovet av värme och kyla i byggnader utgör en betydande del av ett lands totala energianvändning och att reducera detta behov är av yttersta vikt för att nå nationella samt internationella mål för minskad energianvändning och minskade utsläpp. En viktig väg för att nå dessa mål är att öka andelen förnyelsebar energi för kylning och uppvärmning av byggnader. Det kanske största hindret med detta är det faktum att det ofta råder obalans mellan tillgången på förnyelsebar energi och behovet av värme och kyla, vilket gör att denna energi inte kan utnyttjas direkt. Detta är ett av problemen som kan lösas genom att använda termisk energilagring (TES) för att lagra värme eller kyla från när det finns tillgängligt till dess att det behövs. Denna avhandling fokuserar på kombinationen av TES och byggnader för att nå högre energieffektivitet för uppvärmning och kylning. Olika tekniker för energilagring, samt även kombinationen av TES och byggnader, har undersökts och sammanfattats genom en omfattande litteraturstudie. För att kunna identifiera byggnadstyper vanliga i Sverige gjordes även en kartläggning av det svenska byggnadsbeståndet. Inom ramen för denna avhandling resulterade kartläggningen i valet av tre typbyggnader, två småhus samt en kontorsbyggnad, utav vilka de två småhusen användes i en simuleringsfallstudie av passiv TES genom ökad termisk massa (både sensibel och latent). Den andra fallstudien som presenteras i denna avhandling är en utvärdering av ett existerande borrhålslager för säsongslagring av solvärme i ett bostadsområde. I detta fall användes verkliga mätdata i utvärderingen samt i jämförelser med tidigare utvärderingar. Litteraturstudien visade att användningen av TES öppnar upp möjligheter för minskat energibehov och minskade topplaster för värme och kyla samt även möjligheter till en ökad andel förnyelsebar energi för att täcka energibehovet. Genom att använda passiv lagring genom ökad termisk massa i byggnaden är det även möjligt att minska variationer i inomhustemperaturen och speciellt minska övertemperaturer under varma perioder; något som kan leda till att byggnader som normalt behöver aktiv kylning kan klara sig utan sådan. Analysen av kombinationen av TES och byggnadstyper bekräftade att TES har en betydande potential för ökad energieffektivitet i byggnader, men belyste även det faktum att det fortfarande krävs mycket forskning innan vissa av lagringsteknikerna kan bli kommersiellt tillgängliga. I simuleringsfallstudien drogs slutsatsen att en ökad termisk massa endast kan bidra till en liten minskning i värmebehovet, men att tiden med inomhustemperaturer över 24 °C kan minskas med upp till 20 %. Fallstudien av borrhålslagret visade att även om själva lagringssystemet fungerade som planerat så ledde värmeförluster i resten av systemet, samt vissa problem med driften av systemet, till en lägre solfraktion än beräknat. Arbetet inom denna avhandling har visat att TES redan används med framgång i många byggnadsapplikationer (t.ex. varmvattenberedare eller ackumulatortankar för lagring av solvärme) men att det fortfarande finns en stor potential i en utökad användning av TES. Det finns dock hinder såsom behovet av mer forskning för både vissa lagringstekniker samt lagringsmaterial, i synnerhet för lagring med fasändringsmaterial och termokemisk lagring.
QC 20130225
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Moreno, Argilés Pere. "Latent heat thermal energy storage units in HVAC systems for energy management." Doctoral thesis, Universitat de Lleida, 2014. http://hdl.handle.net/10803/288212.
Full textAbstract:
L'objectiu d'aquesta tesi és estudiar l'aplicació de tancs d'emmagatzematge d'energia tèrmica en
una bomba de calor convencional. En aquesta tesi s'inclou un estudi experimental on dos tancs
d'emmagatzematge d'energia són acoblats a una bomba de calor aigua-aigua amb l'objectiu
d'emmagatzemar energia tèrmica per després utilitzar-la per cobrir la demanda de refrigeració
d'un cubicle, produint un desplaçament de la corba de la demanda d'hores puntes a hores valls. En
aquest estudi s'analitza el comportament tèrmic del tanc i es realitza una comparativa entre la
utilització de PCM i aigua com a medis d'emmagatzematge d'energia tèrmica.
En aquesta tesi també s'inclou una descripció de sistemes similar publicats a la literatura, un
estudi teòric on es descriu un model matemàtic per simular la descàrrega del tanc i un anàlisi
d'incerteses dels paràmetres d'entrada, i finalment, un estudi de corrosió de diferents metalls quan
treballen en contacte amb PCM aptes per ser utilitzats en sistemes actius de climatització.El objetivo de esta tesis es estudiar la aplicación de tanques de almacenamiento de energía térmica en una bomba de calor convencional. En esta tesis se incluye un estudio experimental en donde dos tanques de almacenamiento de energía son acoplados a una bomba de calor agua-agua con el objetivo de almacenar energía térmica para posteriormente utilizarla para cubrir la demanda de refrigeración de un cubículo, produciendo un desplazamiento de la curva de la demanda desde las horas punta a las horas valle. En este estudio se analiza el comportamiento térmico del tanque i se realiza una comparativa entre la utilización de PCM i agua como medios de almacenamiento térmico. En esta tesis también se incluye una descripción de sistemas similares publicados en la literatura, un estudio teórico en donde se describe un modelo matemático para simular la descarga del tanque y un análisis de incertidumbres de los parámetros de entrada, y finalmente, un estudio de corrosión de diferentes metales cuando éstos trabajan en contacto con PCM aptos para ser utilizados en sistemas activos de climatización.
The objective of this thesis is to study the application of thermal energy storage tanks (TES) in a standard heat pump. This thesis includes an experimental study where two TES tanks are coupled to a water-to-water heat pump in order to accumulate thermal energy for later use. The system is used for shifting the cooling load of a small house-like cubicle, shifting the load from on-peak to off-peak periods. The thermal behaviour of the TES tank and a comparison between PCM and water as energy storage medium are evaluated in this study. Moreover, this thesis also includes a state-of-the-art review of similar studies found in the literature, a theoretical study where a mathematical model is developed to predict the thermal behaviour of the TES tank during discharging process, an uncertainties analysis of the input parameters, and finally, a corrosion study of different metals when work in contact with potential PCM to be used in HVAC systems.
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Lawson, Chukwuemeka Jonathan Adeolu. "Refrigeration appliances : Performance enchancements via novel thermal-energy storage." Thesis, Cranfield University, 1999. http://hdl.handle.net/1826/4194.
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In recent
*
years there has been increasing concern for the environmental impacts
of economic and technological development. This (principally socio-political) con-
cern has led to the well-known series of environmentall
,y
motivated (global and
local) conventions, agreements and legislation put forward in a bid to manage these
environmental impacts, which in turn has led to research and commercial activ-
ity on environmental issues. One of the major activities identified as adversely
impacting the environment is the manner in which energy is currently harnessed,
inter-converted and utilised. Cont/d.
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Pendyala, Swetha. "Macroencapsulation of Phase Change Materials for Thermal Energy Storage." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4200.
Full textAbstract:
The use of a latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy. Latent heat storage enables high-energy storage density which reduces the footprint of the system and the cost. However, PCMs have very low thermal conductivities making them unsuitable for large-scale use without enhancing the effective thermal conductivity. In order to address, the low thermal conductivity of the PCMs, macroencapsulation of PCMs has been adopted as an effective technique. The macroencapsulation not only provides a self-supporting structure of PCM and separates the PCM from thermal fluids but also enhances the heat transfer rate.
The current work involves study of various concepts of encapsulation of low cost inorganic PCMs. Sodium nitrate (NaNO3), a low cost PCM, was selected for thermal storage in a temperature range of 300 - 500˚C. Various techniques like electroless coatings, coatings using silicates, coatings with metal oxide (SiO2) and sand encapsulation are discussed. A novel technique of metal oxide coating was developed where firstly a high temperature polymer, such as, polymer (stable > 500˚C) was coated over PCM pellets, and cured, so that the pellet becomes insoluble in water as well as several organic solvents and later the metal oxide is coated over the pellet using self-assembly, hydrolysis, and simultaneous chemical oxidation at various temperatures. The coated PCM pellets were characterized.
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Hasnain, Syed Mahmood. "Latent heat thermal energy storage for solar heating applications." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252924.
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Khan, Fahad. "Spherical Tanks for Use in Thermal Energy Storage Systems." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/187.
Full textAbstract:
Thermal energy storage (TES) systems play a crucial part in the success of concentrated solar power as a reliable thermal energy source. The economics and operational effectiveness of TES systems are the subjects of continuous research for improvement, in order to lower the localized cost of energy (LCOE). This study investigates the use of spherical tanks and their role in sensible heat storage in liquids. In the two tank system, typical cylindrical tanks were replaced by spherical tanks of the same volume and subjected to heat loss, stress analysis, and complete tank cost evaluation. The comparison revealed that replacing cylindrical tanks by spherical tanks in two tank molten salt storage systems could result in a 30% reduction in heat loss from the wall, with a comparable reduction in total cost. For a one tank system (or thermocline system), a parametric computational fluid dynamic (CFD) study was performed in order to obtain fluid flow parameters that govern the formation and maintenance of a thermocline in a spherical tank. The parametric study involved the following dimensionless numbers: Re (500-7500), Ar (0.5-10), Fr (0.5-3), and Ri (1-100). The results showed that within the examined range of flow characteristics, the inlet Fr number is the most influential parameter in spherical tank thermocline formation and maintenance, and the largest tank thermal efficiency in a spherical tank is achieved at Fr = 0.5. Experimental results were obtained to validate the CFD model used in the parametric study. For the flow parameters within the current model, the use of an eddy viscosity turbulence model with variable turbulence intensity delivered the best agreement with experimental results. Overall, the experimental study using a spherical one tank setup validated the results of the CFD model with acceptable accuracy.
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Alkhazaleh, A. "Thermal energy storage and fire safety of building materials." Thesis, University of Bolton, 2018. http://ubir.bolton.ac.uk/1988/.
Full textAbstract:
Energy storage using organic phase change materials (PCMs) has attracted significant attention in recent years for renewable energy utilization in building materials. PCMs are capable of storing and releasing a large amount of latent heat during their phase transitions. Paraffin (PA), a eutectic mixture (EM) of capric acid (CA) and lauric acid (LA) and butyl stearate (BS) have been selected as PCMs for this work due to their melting temperatures being close to human comfort temperature, 17 - 28 oC. Plaster (PL) as a building material is chosen due to its ease of construction into plaster boards and also because it is a good insulator against heat and sound. The most significant concern when using an organic PCM is its flammability. This research sets out to determine the effect of using PCMs in PL on the product’s flammability, and whether it is possible to use carrier materials and/or flame retardants to reduce their flammability while maintaining the thermal energy storage properties. Three techniques of incorporation of PCMs into PL are used to address this question. The first one is to immerse PL into hot melted PCMs using a vacuum impregnation method. The PCM however, could easily leak to the surface of PL, particularly when the temperature is above the melting temperature of PCM and also their high flammability evaluated using cone calorimetry was a limiting factor to pursuance of this route. The second method is a direct incorporation technique, i.e. adding PCM directly to PL. With this method also the leakage of PCMs was observed and all samples ignited, though the flammability parameters were less intense than those observed when the immersion method was used. To prevent the leakage of PCM and to improve the consistency of organic PCM with building materials, form-stable PCMs composites are used in the third method. Carrier materials, namely nanoclay (NC), diatomaceous earth (DE), expanded perlite (EP), fly ash (FA) and brick dust (BD) were selected to adsorb and retain the PCMs in their pores. SEM (scanning electron microscope) demonstrated that PCMs were uniformly adsorbed in most of the carrier materials. DSC (differential scanning calorimeter) used to measure the thermal properties of PCMs showed that when these form stable composites were added to PL, they acted as PCMs, although the latent heat values were reduced. Thermal gravimetric analysis (TGA) results demonstrates that the PCMs’ decomposition was not affected by the presence of carrier materials or PL. Cone calorimetry showed that the use of carrier materials had minimal effect on the flammability of PCMs. To evaluate the thermal energy storage performance, a small environmental chamber was used, i.e. a small test “room” of PL with dimensions of 100 mm x 100 mm x 100 mm and thickness 10 mm was set up using 6 pieces of PL. The top board of the cubic room contained PCM, and the temperature differences between the surfaces of control PL and modified PL were recorded during heating and cooling of the room. The results from heating and cooling cycles showed that the PCMs and form stable-PCM composites reduced the peak temperature and delayed the time taken to release the stored energy, the values depending on the percentage of PCMs used. To reduce the flammability of PCMs while maintaining their energy storage performance, two approaches have been undertaken: (i) use of expanded graphite (EG) as a flame retardant carrier- material and (ii) use of a liquid flame-retardant, resorcinol bis(diphenyl phosphate) (RDP). The results demonstrated that the flame retardant did not affect the energy storage performance of the PCM. While RDP was not effective on a PA containing PL sample, the flammability of a PL+BS sample was significantly reduced with the addition of EG and RDP.
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Thompson, Dawn. "The role of nanoparticles in thermal energy storage systems." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.728678.
Full textAbstract:
The growing demand for energy on the one hand and climate change, which is closely related to increased energy consumption, on the other, have become central issues worldwide. The present investigation aims at identifying potential ways in which renewable energy can become more appealing and efficient by storing the energy produced, for example by a wind turbine or by residual heat, so that energy is readily available for the consumer in both peak and off peak hours. We can look at this both in terms of an energy storage device or as thermal insulation. An ideal thermal energy storage device should be easy and fast to charge and discharge, while sustaining minimal losses when inactive. The first aspect requires a search for materials with high thermal conductivity while in contact with the storage medium (an organic or aqueous-based substance). Amongst the many possibilities, we focus here on nanoparticles within a fluid, i.e. a nanofluid, as a means to store latent heat that is produced for example by a renewable source. Over the past decade nanoparticles have shown the potential to enhance the thermal conductivity of base fluids such as water, ethylene glycol and engine oil, in some cases quite dramatically. The idea here is to embed nanoparticles within a base fluid undergoing a phase change, in order to improve the characteristics of the charge/discharge cycle. However, this phenomenon is poorly understood and the literature is contradictory. Moreover, to avoid the aggregation and improve nanoparticle dispersion, surfactants are added to the nanofluid, thus introducing an additional active element whose role has to be understood. This Thesis focuses on the knowledge gained from simulations and experiments to propose modifications of the nanoparticles-surfactant-base fluid system to improve heat conduction for use in thermal energy storage devices.
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Olrog, Robert. "Numerical Analysis ofLatent Thermal Energy Storage in a Cavity." Thesis, KTH, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226727.
Full textAbstract:
Latent Thermal Energy Storage (LTES) has drawn attention because the technology is a simple and cost-efficient method to store large amounts of energy. Latent energy is either stored or released when the material inside the LTES undergoes phase-change. As LTES operates at a constant temperature it can be utilized in several fields such as waste heat management, building insulation, storage of solar energy and electronic cooling to name a few. An obstacle to widespread use of LTES is its low energy recharge and discharge rate due to the phase-change materials (PCM) thermophysical properties, namely thermal conductivity. PCMs such as fatty acids, salt hydrates and paraffins are potential materials for domestic application because of their melting temperature and are especially affected by low thermal conductivity.The objective is to numerically model a Latent Thermal Energy Storage and simulate the melting and solidification process with different boundary conditions, and afterwards analyze how it impacts natural convection, heat transfer rates, and the solid-liquid interface. Special attention will be given to natural convection as a change in its strength can have a large impact on heat transfer. Optimization and enhancing the rate of heat transfer is important as it improves LTES effectiveness.The geometry used in the numerical model is two-dimensional with 50 mm in width and 120 mm in height. The heat transfer surface area is the 120 mm wall. Four cases are examined; two of which are melting and two of solidification. The geometry is identical in all cases but placed in either a vertical or horizontal orientation.Transient simulations are performed using ANSYS Fluent which is a computational fluid dynamics software tool. The geometrical model used for ANSYS mimics the experimental setup that Kamkari and Shokouhmand (2014) built to analyze melting in a rectangular enclosure. This allows for a comparison between numerical data and experimental observations in one of the melting cases.The comparison between the numerical and experimental results show good agreement as the solid-liquid interface is nearly identical and the amount of liquid in the enclosure differs by less than 5 percent after two-hundred minutes. Natural convection is present in all cases to a varying degree, and the amount of phase-change correlates to its strength and duration. During melting convection is the main mode of heat transfer in both orientations, but in the vertical case the strength tapers off as time progresses. The horizontal orientation produces a natural convection for the entire duration of the simulation therefore leading to a higher melting rate.The solidification process entails conduction as the dominant mode of heat transfer. In the horizontal orientation there is no detectable natural convection. The vertical position shows convection in the early stages of solidification but disappears quickly. As a result there is a higher amount of solid material in the vertical orientation by the end of the simulation.Latent värme energilagring(LTES) har fått ökad uppmärksamhet eftersom teknologin är en simpel och kostnad-effektiv metod att lagra stora mängder energi. Latent värme lagras eller frigörs när materialet inuti LTES byter fas. Eftersom LTES bibehåller en konstant temperatur har den flera användningsområden inom isolering, solfångare och elektronisk kylning för att nämna några. Ett hinder till utspridd användning av LTES är den långsamma laddnings- och urladdningshastigheten på grund av fasbytesmaterialets(PCM) ämnesegenskaper, nämligen termisk konduktivitet. Låg termisk konduktivitet drabbar PCM som fettsyror, salthydrater och paraffin som är potentiella material för många LTES applikationer på grund av deras smälttemperatur.Målet är att numeriskt modellera en LTES och simulera smält och stelningsprocessen med olika randvillkor, och därefter analysera hur dessa påverkar naturlig konvektion, värmeöverföring och smältkonturen. Extra uppmärksamhet ges till naturlig konvektion eftersom en ändring i dess styrka kan ha en stor påverkan på värmeöverföringen. Att försöka optimera värmeöverföringen är viktig då det kommer öka LTES attraktivitet för termisk energilagring.Geometrin som används i den numeriska modellen är två-dimensionell med 50 mm i bredd och 120 mm i höjd. Värmeöverföringsarean är väggen som är 120 mm. Fyra fall examineras: två smältfall och två stelningsfall. Geometrin var identisk under alla fall men placeras i antingen en vertikal eller horisontell orientering.Transienta simuleringar utfördes i ANSYS Fluent som är en computational fluid dynamics mjukvara. Modellen liknar Kamkari, Shokouhmand (2014) experimentella uppsättning som byggdes för att analysera PCM smältning i en rektangulär behållare. Detta gjordes för att få möjligheten till att jämföra numerisk data till experimentella observationer i ett av fallen.Jämförelsen mellan simuleringens och experimentets resultat visar god likhet eftersom både smältkonturen och mängden vätska i behållaren är snarlika, samt skiljer sig mindre än 5% efter två-hundra minuter. Naturlig konvektion närvarar i alla fall, och mängden fasbyte korrelerar till dess styrka och varaktighet. Under smältning är konvektion den huvudsakliga drivaren av värmeöverföring i båda orienteringar, men i det vertikala fallet minskar styrkan under simuleringen. Det horisontala fallet producerar konvektion under hela simuleringen vilket leder till en högre smälthastighet jämfört med den vertikala.I stelningsprocessen är konduktion den huvudsakliga drivaren av värme. Det horisontella fallet visar ingen konvektion. I den vertikala positionen finns tecken på konvektion i det tidiga skedet, men minskar snabbt. Därför finns det mer fast materiel i den vertikala positionen vid slutet av simuleringen på grund av konvektion vid starten.
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Ampatzi, Eleni. "Potential for solar thermal technologies and thermal energy storage to reduce the energy use from Welsh housing." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/55906/.
Full textAbstract:
This thesis deals with the potential contribution that state-of-the-art solar thermal (ST) systems enhanced by thermal energy storage (TES) technologies might have in reducing the energy use in Welsh dwellings. The focus of this work lies with the share of the overall amount of conventional energy currently consumed for thermal comfort and hot water preparation that could be replaced by solar energy harvested by active, water-based, solar systems. Twelve typical Welsh dwellings drawn from a recent survey and considered as representative of the Welsh housing stock are modelled and the solar collectors' yield for different orientations and tilts is predicted. The subject is investigated with computer simulations using the TRNSYS simulation engine. The methodology dictates at first prediction and analysis of the thermal energy demand profiles of 12x4 case studies using average (smoothed) and actual (warmer) weather conditions, continuous and intermittent comfort maintenance. Next the ST potential is estimated considering solely a maximum (0.7) and an average (0.4) overall system efficiency and no other technical part for the ST system (modelling approach), in order to investigate the mismatch of energy demand and availability and the TES contribution. The performance characteristics of some representative European ST systems (short-term TES only), as derived from the IEA SHC Task 26 FSC method, are then applied to the simulations to reveal the potential with realistic losses and parasitic energy consumption included (applied only to 5 compatible models). It is revealed that all these house types are possible candidates for effective ST applications, assuming that economies of scale would allow for large absorber areas in the near future. The modelling approach shows that ST systems could contribute to thermal savings between 9%-34% solely with direct utilisation of the collected energy. Furthermore, for most cases, if reasonable sized stores would be used (up to 300kWh TES capacity) then the solar contribution to the overall thermal energy consumption, in the most favourable conditions, would be around 42-58%. Only a couple of models appear to have a lower potential, mainly due to lack of sufficient absorber areas. However for reaching the highest end of expectations for certain house types---up to 54% with average and up to 100% with warmer weather conditions---inter-seasonal storage would be required. In this case, the justifiable storage capacities predicted correspond to very large store volumes, revealing that these are currently not feasible options, as sensible heat storage is still the state-of-the-art for TES. Use of innovative storage types identified by the literature survey, that would only be available in the future, are required in order to achieve high solar contributions, considering space limitations in Welsh dwellings. The FSC results show that for the 5 models the use of solar energy would bring thermal energy savings of around 41-47% if the best system is employed compared to a conventional system, while if parasitic (electric) energy consumption is considered the expected energy savings could be as low as 10%. The actual ST potential is analysed and is found to be in between the two approaches, as both methods have advantages and limitations and complement each other.
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Allen, Kenneth Guy. "Performance characteristics of packed bed thermal energy storage for solar thermal power plants." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4329.
Full textAbstract:
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Solar energy is by far the greatest energy resource available to generate power. One of the difficulties of using solar energy is that it is not available 24 hours per day - some form of storage is required if electricity generation at night or during cloudy periods is necessary. If a combined cycle power plant is used to obtain higher efficiencies, and reduce the cost of electricity, storage will allow the secondary cycle to operate independently of the primary cycle. This study focuses on the use of packed beds of rock or slag, with air as a heat transfer medium, to store thermal energy in a solar thermal power plant at temperatures sufficiently high for a Rankine steam cycle. Experimental tests were done in a packed bed test section to determine the validity of existing equations and models for predicting the pressure drop and fluid temperatures during charging and discharging. Three different sets of rocks were tested, and the average size, specific heat capacity and density of each set were measured. Rock and slag samples were also thermally cycled between average temperatures of 30 ºC and 510 ºC in an oven. The classical pressure drop equation significantly under-predicts the pressure drop at particle Reynolds numbers lower than 3500. It appears that the pressure drop through a packed bed is proportional to the 1.8th power of the air flow speed at particle Reynolds numbers above about 500. The Effectiveness-NTU model combined with a variety of heat transfer correlations is able to predict the air temperature trend over the bed within 15 % of the measured temperature drop over the packed bed. Dolerite and granite rocks were also thermally cycled 125 times in an oven without breaking apart, and may be suitable for use as thermal storage media at temperatures of approximately 500 ºC. The required volume of a packed bed of 0.1 m particles to store the thermal energy from the exhaust of a 100 MWe gas turbine operating for 8 hours is predicted to be 24 × 103 m3, which should be sufficient to run a 25-30 MWe steam cycle for over 10 hours. This storage volume is of a similar magnitude to existing molten salt thermal storage.
AFRIKAANSE OPSOMMING: Sonenergie is die grootste energiebron wat gebruik kan word vir krag opwekking. ‘n Probleem met die gebruik van sonenergie is dat die son nie 24 uur per dag skyn nie. Dit is dus nodig om die energie te stoor indien dit nodig sal wees om elektrisiteit te genereer wanneer die son nie skyn nie. ‘n Gekombineerde kringloop kan gebruik word om ‘n hoër benuttingsgraad te bereik en elektrisiteit goedkoper te maak. Dit sal dan moontlik wees om die termiese energie uit die primêre kringloop te stoor, wat die sekondêre kringloop onafhanklik van die primêre kringloop sal maak. Dié gevalle studie ondersoek die gebruik van ‘n slakof- klipbed met lug as hitteoordragmedium, om te bepaal of dit moontlik is om hitte te stoor teen ‘n temperatuur wat hoog genoeg is om ‘n Rankine stoom kringloop te bedryf. Eksperimentele toetse is in ‘n toets-bed gedoen en die drukverandering oor die bed en die lug temperatuur is gemeet en vergelyk met voorspelde waardes van vergelykings en modelle in die literatuur. Drie soorte klippe was getoets. Die gemiddelde grootte, spesifieke hitte-kapasiteit en digtheid van elke soort klip is gemeet. Klip en slak monsters is ook siklies tussen temperature van 30 ºC en 510 ºC verkoel en verhit. Die klassieke drukverlies vergelyking gee laer waardes as wat gemeet is vir Reynolds nommers minder as 3500. Dit blyk dat die drukverlies deur ‘n klipbed afhanklik is van die lug vloeispoed tot die mag 1.8 as die Reynolds nommer groter as omtrent 500 is. Die ‘Effectiveness-NTU’ model gekombineerd met ‘n verskeidenheid van hitteoordragskoeffisiënte voorspel temperature binne 15 % van die gemete temperatuur verskil oor die bed. Doloriet en graniet klippe het 125 sikliese toetse ondergaan sonder om te breek, en is miskien gepas vir gebruik in ‘n klipbed by temperature van sowat 500 ºC Die voorspelde volume van ‘n klipbed wat uit 0.1 m klippe bestaan wat die termiese energie vir 8 ure uit die uitlaat van ‘n 100 MWe gasturbiene kan stoor, is 24 × 103 m3. Dit behoort genoeg te wees om ‘n 25 – 30 MWe stoom kringloop vir ten minste 10 ure te bedryf. Die volume is min of meer gelyk aan dié van gesmelte sout store wat alreeds gebou is.
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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.
Full textAbstract:
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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Maidadi, Mohaman Bello. "Packed-bed rock thermal energy storage for concetrated solar power: enhancement of storage time and system efficiency." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020914.
Full textAbstract:
Solar thermal energy harvesting is a promising solution to offset the electricity demands of a growing population. The use of the technology is however still limited and this can most likely be attributed to the capital cost and also the intermittent nature of solar energy which requires incorporation of a storage system. To make the technology more attractive and effective, cheap means of harvesting solar energy and the development of efficient and inexpensive thermal energy storage devices will improve the performance of solar energy systems and the widespread use of solar energy. Heat storage in a packed-bed rock with air as the working fluid presents an attractive and simple solution for storing solar thermal energy and it is recommended for solar air heaters. A packed-bed rock storage system consists of rocks of good heat capacity packed in a storage tank. The working fluid (air) flows through the bed to transfer its energy. The major concern of the design for a packed-bed rock thermal storage system is to maximize the heat transfer and minimise the pressure drop across the storage tank and hence the pumping power. The time duration the stored energy can be preserved and the air flow wall effect through the bed are the common complications encountered in this system. This study presents an experimental and analytical analysis of a vacuum storage tank with the use of expanded perlite for high temperature thermal energy storage in a packed-bed of rocks. Dolerite rocks are used as the storage medium due to their high heat capacity and as they are locally available. To minimise the pressure drop across the tank, moderate rock sizes are used. The tank contains baffles, allowing an even spread of air to rock contact through the entire tank, therefore improving heat transfer. There is a good correlation between the predicted and the actual results (4 percent) which implies that the baffles incorporated inside the vacuum tank forces the air through the entire tank, thereby resulting in an even lateral temperature distribution across the tank. The investigation of heat loss showed that a vacuum with expanded perlite is a viable solution to high temperature heat storage for an extended period. The research also focuses on the investigation of a proposed low cost parabolic trough solar collector for an air heating system as shown in Figure (1.3). The use of a standard solar geyser evacuated tube (@R130 each) has cost benefits over the industry standard solar tubes normally used in concentrating solar power systems. A mathematical was developed to predict the thermal performance of proposed PTC and it was found that the measured results compared well with the predictions. The solar energy conversion efficiency of this collector is up to 70 percent. This research could impact positively on remote rural communities by providing a source of clean energy, especially for off-grid applications for schools, clinics and communication equipment. It could lead to a significant improvement in the cost performance, ease of installation and technical performance of storage systems for solar heating applications.
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Golob, Matthew Charles. "Convective heat transfer performance of sand for thermal energy storage." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41061.
Full textAbstract:
This thesis seeks to examine the effective convective heat exchange of sand as a heat exchange medium. The goal of this exploratory research is to quantify the heat transfer coefficient of sand in a proposed Thermal Energy Storage (TES) system which intends to complement solar thermal power generation. Standard concentrator solar thermal power plants typically employ a heat transfer fluid (HTF) that is heated in the collector field then routed to the power generators or TES unit. A fairly clear option for a TES system would be to utilize the existing HTF as the working storage medium. However, the use of conventional HTF systems may be too expensive. These fluids are quite costly as the quantity needed for storage is high and for some fluids their associated high vapor pressures require expensive highly reinforced containment vessels. The proposed storage system seeks to use sand as the storage medium; greatly reducing the expenses involved for both medium and storage costs. Most prior TES designs using sand or other solids employed them in a fixed bed for thermal exchange. The proposed TES system will instead move the sand to drive a counter flow thermal exchange. This counter flow design allows for a much closer temperature of approach when compared to a fixed bed. As cost and performance are the primary goals to tackle of the proposed system, the evaluation of the sandâ s thermal exchange effectiveness in a flowing state is necessary. Experiments will be conducted to measure the effective heat transfer coefficient between the sand and representative solid surfaces used as the heat transfer conduits. Additional experiments that will be looked at are wear caused by the sand as a consideration for long term design viability as well as angle of repose of the sand and its effect on scoop design for improved materials handling. Key investigational aspects of these experiments involve the sand grain size as well as shape of the heat exchanger surfaces. The thesis will evaluate the resulting convective heat transfer coefficient of the sand as related to these features. The data will then be compared and verified with available literature of previously studied characteristic thermal properties of sand. The measured and confirmed data will then be used to further aid in a design model for the proposed TES system.
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Wang, Weilong. "Mobilized Thermal Energy Storage for Heat Recovery for Distributed Heating." Doctoral thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-11142.
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Conventional energy sources—oil and electricity—dominate the heat supply market. Due to their rising costs and their negative environmental effects on global climate change, it is necessary to develop an alternative heat supply system featuring low cost, high energy efficiency and environment friendliness. At present, it is often challenging to supply heat to detached buildings due to low energy efficiency and high distribution cost. Meanwhile, significant amounts of industrial waste and excess heat are released into the environment without recycling due to the difficulty of matching time and space differences between suppliers and end users. Phase change materials (PCMs), with the advantages of being storable and transportable, offer a solution for delivering that excess heat from industrial plants to detached buildings in sparse, rural areas. The objective of this thesis is to study PCMs and latent thermal energy storage (LTES) technology, and to develop a mobilized thermal energy storage (M-TES) system that can use industrial waste or excess heat for heat recovery and distribution to areas in need. Organic PCMs were chosen for study because they are non-toxic and non-corrosive, and they exhibit no phase separation and little sub-cooling when compared to inorganic PCMs. Two major issues including leakage of liquid PCMs and low thermal conductivity. Polyethylene glycol (PEG) was chosen to help analyze the thermal behavior of organic PCMs and PEG-based form-stable composites. To overcome the issue of low thermal conductivity, modified aluminum nitride (AlN) powder was added to the composites. Increased thermal conductivity traded off decreased latent heat. The PEG/EG composite, prepared by mixing the melted PEG into an expanded graphite (EG) matrix showed good thermal performance due to its large enthalpy and high thermal conductivity. To make a systematic study of the M-TES system, a compact lab-scale system was designed and built. Characteristics of PCM were studied, and the performance of the direct-contact TES container was investigated. A case study using an M-TES system to deliver heat from a combined heat and power (CHP) plant to a small village was conducted. A technical and economic feasibility study was conducted for an integrated heat supply system using the M-TES system. In addition, the options for charging a TES container at a CHP plant were analyzed and compared from the viewpoints of power output, heat output and incomes.Ångpanneföreningens Forskningsstiftelse (ÅF)
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Athukorala, Niluka. "Feasibility Study of Heat Driven Cooling Based Thermal Energy Storage." Thesis, KTH, Energiteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101318.
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Human needs are unlimited, but resources are limited to satisfy these needs. Because of this reason, consideration of sustainability in utilization of energy is of immense importance. As an intelligent species, mankind is interested in satisfying their needs sustainably. In this view, use of renewable energy, reduction of energy usage, and reduction/ elimination of use of fossil fuels are of great importance. It can be observed that there is rising demand for space cooling, and it has the highest share of energy consumption in the building sector. Colombo, Sri Lanka has a hot and humid climate, and above mentioned condition prominently prevails. On the other hand Sri Lanka experiences a considerable increase of energy demand and electricity tariff rates annually and this trend is prominent. Therefore the demand for finding energy efficient, renewable and cost effective solution is ever increasing. Accordingly, this study was carried out to conduct a techno-economic feasibility on thermal energy storage integrated into absorption chiller. Both these technologies are commercially available and have the measure towards sustainability. It was observed that most common air conditioning applications are in office buildings, and therefore the focus of this study is on a typical office building in Colombo city. The result of the study can be then applied to other office buildings in the city. Trace700 software tool was used to model and simulate the different system alternatives and to investigate the energy and economic performance. It was found that the cool thermal storage integrated into thermally driven absorption chiller has a good energy saving and cost saving potential and biogas can be a better energy source to supply the thermal energy required by the chiller and this energy is utilized in a sustainable manner.