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Preparation and thermal properties of polyethylene glycol/expanded graphite blends for energy storage
Mälardalen University, School of Sustainable Development of Society and Technology. (bioenergy group)
Mälardalen University, School of Sustainable Development of Society and Technology. (bioenergy group)ORCID iD: 0000-0003-0300-0762
2009 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 86, no 9, p. 1479-1483Article in journal (Refereed) Published
Abstract [en]

Expanded graphite is a promising heat transfer promoter due to its high conductivity, which improves the thermal conductivity of organic phase change materials. Moreover, it can also serve as supporting materials to keep the shape of the blends stable during the phase transition. After various investigation, the results showed that the maximum weight percentage of polyethylene glycol was as high as 90% in this paper without any leakage during the melting period, with the latent heat of 161.2 J g−1 and the melting point of 61.46 °C. It was found that the value of the latent heat was related to the polyethylene glycol portion, increased with the increase in polyethylene glycol content. Moreover, the measured enthalpy of the composite phase change materials was proportional to the mass ratio of the polyethylene glycol component. The melting temperatures were almost the same with different ratios of composites. The conductivity of blends was improved significantly with the high value of 1.324 W m−1 K−1 compared to the pure polyethylene glycol conductivity of 0.2985 W m−1 K−1.

Place, publisher, year, edition, pages
Elsevier , 2009. Vol. 86, no 9, p. 1479-1483
Keywords [en]
Polyethylene glycol; Expanded graphite; Form-stable materials; Thermal conductivity
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-7451DOI: 10.1016/j.apenergy.2008.12.004ISI: 000265735300015Scopus ID: 2-s2.0-63449093377OAI: oai:DiVA.org:mdh-7451DiVA, id: diva2:274729
Available from: 2009-11-16 Created: 2009-10-30 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Mobilized Thermal Energy Storage for Heat Recovery for Distributed Heating
Open this publication in new window or tab >>Mobilized Thermal Energy Storage for Heat Recovery for Distributed Heating
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2010
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 92
National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-11142 (URN)978-91-86135-98-0 (ISBN)
Public defence
2010-12-20, Lambda, Mälardalen University, Västerås, 10:00 (English)
Opponent
Supervisors
Projects
Ångpanneföreningens Forskningsstiftelse (ÅF)
Available from: 2010-11-22 Created: 2010-11-18 Last updated: 2010-11-29Bibliographically approved

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