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Submerged finned heat exchanger latent heat storage design and its experimental verification
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Thermal Energy Storage, Energy Technology)ORCID iD: 0000-0001-6982-2879
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. (Kraft- och värmeteknologi, Heat and Power Technology)ORCID iD: 0000-0001-9556-552X
2012 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 93, no SI, 507-516 p.Article in journal (Refereed) Published
Abstract [en]

Thermal energy storage (TES) has shown potential in improving the overall performance in energy systems, through shifting of thermal load demand, and through matching of uneven energy availability in time and in space. Latent heat TESs demonstrate advantages over sensible heat TESs for their high storage density and small temperature swing; however, lack of accurate knowledge in novel material properties and lack in a holistic design protocol often lead to difficulties in reaching technically viable storage design. With the aim of proposing a sound latent heat based TES design-to-validation protocol, this paper covers material property characterization through Temperature-history (T-history) method, heat exchanger design through heat transfer modeling, and model validation through experimental verification. A model for submerged cylindrically finned heat exchanger latent heat storage unit with phase change material was built. The results show that performance of gelled salt-hydrate based TES can be assessed with a pure conduction based model. This material property characterization-to-model verification approach may serve as a standard in providing accurate storage design for performance evaluation.

Place, publisher, year, edition, pages
2012. Vol. 93, no SI, 507-516 p.
Keyword [en]
PCM, Energy Storage, T-History, Heat Transfer Enhancement, modeling
National Category
Energy Engineering
Research subject
SRA - Energy
Identifiers
URN: urn:nbn:se:kth:diva-34261DOI: 10.1016/j.apenergy.2011.12.019ISI: 000302836500059Scopus ID: 2-s2.0-84857996845OAI: oai:DiVA.org:kth-34261DiVA: diva2:419985
Projects
Cold Thermal Energy Storage
Funder
StandUp
Note

QC 20120524

Available from: 2011-05-30 Created: 2011-05-30 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Heat Transfer Aspects of Using Phase Change Material in Thermal Energy Storage Applications
Open this publication in new window or tab >>Heat Transfer Aspects of Using Phase Change Material in Thermal Energy Storage Applications
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Innovative methods for providing sustainable heating and cooling through thermal energy storage (TES) have gained increasing attention as heating and cooling demands in the built environment continue to climb. As energy prices continue to soar and systems reach their maximal capacity, there is an urgent need for alternatives to alleviate peak energy use. TES systems allow decoupling of energy production from energy utilization, both in location and in time. It is shown in this thesis that successful implementation of TES in the built environment alleviates peak energy load and reduces network expansion as well as the marginal energy production cost.

This thesis analyzes phase change material (PCM) based TES systems in terms of material property characterization, numerical modeling and validation of thermal storage, as well as case specific techno-economic feasibility studies of system integration. The difficulties identified in latent heat TES design, such as heat transfer aspects, subcooling and identification of phase separation, have been analyzed through Temperature-History mapping and TES numerical modeling with experimental validation. This work focuses on the interdependency between resource availability, thermal charge/discharge power and storage capacity. In a situation where resource availability is limited, e.g. when using free cooling, waste heat or off-peak storage, the thermal power and storage capacity are strongly interrelated and should always be considered in unison to reach an acceptable techno-economic solution. Furthermore, when considering TES integration into an existing thermal energy distribution network, three adverse aspects are revealed in the Swedish case study: the single tariff system, the low-return temperature penalty, and the low storage utilization rate. These issues can be overcome through better adapted policies and optimized storage control strategies. Finally, despite the currently unfavorable conditions in the Swedish energy system, it is shown that TES has the potential to mitigate climate change through greenhouse gas emission reduction by displacing fossil-fuel based marginal thermal energy production.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xiv, 59 p.
Series
Trita-KRV, ISSN 1100-7990 ; 11/04
Keyword
thermal energy storage, comfort cooling, phase change materials, heat transfer
National Category
Energy Engineering Other Materials Engineering Other Environmental Engineering
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-34263 (URN)978-91-7501-034-2 (ISBN)
Presentation
2011-06-22, M2, Brinellvägen 64, KTH, Stockholm, 15:47 (English)
Opponent
Supervisors
Projects
Cold Thermal Energy Storage
Funder
StandUp
Note
QC 20110629Available from: 2011-06-29 Created: 2011-05-30 Last updated: 2011-06-29Bibliographically approved
2. Latent Heat Thermal Energy Storage for Indoor Comfort Control
Open this publication in new window or tab >>Latent Heat Thermal Energy Storage for Indoor Comfort Control
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Equating Earth’s existence to 24 hours, we, the Homo sapiens, came about in the last four seconds. Fossil fuel came to our knowledge with mass extraction dating from the Industrial Revolution two centuries ago, in other words 4 milliseconds out of Earth’s 24-hour equivalent lifetime. With the unruly use of fossil fuel based resources, global temperature increase due to anthropogenic emission is projected by the Intergovernmental Panel on Climate Change (IPCC) to increase between 2 °C and 6 °C by 2100. The expected results are unprecedented climatic phenomena, such as intense tropical cyclones, extreme heat waves, and heavy precipitation among others. Limiting climate change has become one of the most discerning issues in our highly energy dependent society.

Ever-increasing energy demand goes in hand with improved living standard due to technologic and economic progress. Behavioral change is one of the ultimate solutions to reduce energy demand through adequate life style change; however such approach requires societal paradigm shift. In this thesis, we look into using energy storage technology to peak shave and to load shift energy so as to attain increased renewable energy source utilization, improved system’s energy efficiency, and reduced Greenhouse Gas (GHG) emission without compromising living comfort.

High energy density thermal energy storage (TES) systems utilize phase change materials as storage mediums where thermal energy is principally stored in the form of latent heat (LH). Advantages of such systems are compact components and small storage temperature swing. However, challenges remain in implementing LHTES to the built environment, namely lack of understanding of system dynamics, uncertainty in component design, and non-documented material property are to be addressed.

The goal of this thesis is to address the issues on material property characterization, on component heat transfer study and on system integration. A methodology in measuring material’s thermo physical property through T-History setup is defined. Caveats of existing methodology are presented and improvements are proposed. The second part of this thesis consists of establishing valid numerical models of LHTES component for both shape stabilized and free flowing PCMs. Experimental verifications were performed and models were validated. Improvement to the thermal power performance was studied and was reached with multistage multi-PCM storage design. Techno-economic optimization and parametric study were carried out for transient TES integrated system study. Finally, an estimation of the Swedish peak energy demand reduction was performed through study of TES implementation to the existing energy systems. The peak energy shave attained through TES implementation determines the amount of fossil fuel based marginal energy that can be reduced for a greener environment.

Abstract [sv]

Om vi låter jordens livstid motsvaras av 24 timmar, har mänskligheten endast existerat under de sista fyra sekunderna. Fossila bränslen med utvinning i stor skala kom till vår kännedom under den industriella revolutionen för två sekel sedan, med andra ord fyra millisekunder av jordens dygnslånga livstid. På grund av ohämmad fossilbränsleanvändning förutspår FN:s klimatpanel (IPCC) att den av människor orsakade globala uppvärmningen blir mellan 2°C och 6°C till år 2100. Onormala klimatfenomen förväntas som resultat, till exempel starka tropiska cykloner, extrema värmeböljor, och kraftig nederbörd. Att begränsa klimatförändringarna har blivit en av de viktigaste frågorna i vårt starkt energiberoende samhälle.

Ständigt ökande efterfrågan på energi går hand i hand med förbättrad levnadsstandard på grund av teknologiska och ekonomiska framsteg under det senaste århundradet. Beteendeförändringar, att anpassa vår livsstil, har betraktats som den slutgiltiga lösningen, men en sådan strategi kräver långsiktig utbildning och vilja. I denna avhandling undersöks en ny energiteknik: energilagring, för att minska topplaster och skifta belastningen så att vi kan gå mot ett paradigmskifte i form av ökat nyttjande av förnybara energikällor, förbättrad energieffektivitet och minskade utsläpp av växthusgaser utan att ge avkall på boendekomfort.

System för termisk energilagring med hög densitet (TES) använder fasändringsmaterial som lagringsmedia, där värmeenergi huvudsakligen lagras i form av latent värme (LH). Fördelarna är kompakta komponenter och små variationer i lagringstemperatur. Utmaningar återstår i att integrera LHTES i fastigheter: bristande förståelse för systemdynamiken, osäkerhet i komponentdesign och odokumenterade materialegenskaper.

Målet med denna avhandling är att ta itu med frågor kring materialkarakterisering, studier av värmeöverföring för komponenter och om systemintegration. En metod för att mäta materials entalpi genom Temperature-History definieras genom att identifiera brister i existerande metoder, och implementera förbättringar. Den andra aspekten består i att upprätta gångbara numeriska modellerna för LHTES, där experimentell verifiering har genomförts. Förbättring av den termiska effekten erhålls med flerstegs-fasändringsmaterial-lagring. Känslighetsanalys och teknisk-ekonomisk optimering utförs för integrerad systemdesign med TES. Slutligen görs en uppskattning av hur mycket Sveriges topplast i energisystemet kan minskas genom att studera implementering av TES. Minskningen i topplast som uppnås genom implementation av TES bestämmer mängden marginalenergi från fossila bränslen som kan reduceras för att nå ett mer uthålligt samhälle.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xvii, 77 p.
Series
Trita-KRV, ISSN 1100-7990 ; 13:02
Keyword
Thermal Energy Storage, Phase Change Material, Indoor Comfort, Heat Transfer, Termisk Energilagring; Fasändringsmaterial; Inomhuskomfort; Värmeöverföring
National Category
Energy Engineering Energy Systems
Identifiers
urn:nbn:se:kth:diva-119275 (URN)978-91-7501-679-5 (ISBN)
Public defence
2013-04-09, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130312

Available from: 2013-03-12 Created: 2013-03-11 Last updated: 2013-03-12Bibliographically approved

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