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Thermal performance of the mobilized thermal energy storage system
Mälardalen University, School of Sustainable Development of Society and Technology.
Mälardalen University, School of Sustainable Development of Society and Technology. (Bioenergy)ORCID iD: 0000-0003-0300-0762
Mälardalen University, School of Sustainable Development of Society and Technology. (Bioenergy)ORCID iD: 0000-0002-7233-6916
2011 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A direct-contact mobilized thermal energy storage (M-TES) system with high heat density and heat transfer rate has been exploited to transport industrial heat for distributed users. In this paper, a lab-scale experimental setup has been built consisting of a direct-contact thermal energy storage (TES) container, oil/water tank, electrical boiler, oil/water pump and plate heat exchanger. Erythritol was chosen to work as an organic phase change material (PCM) due to its large heat density, suitable melting point (118oC) for industrial heat recovery, and non toxic and corrosive. Heat transfer oil (HTO) served as a heat transfer medium to carry and transfer heat. The theoretical heat capacity of the TES container is 13.1 kWh with 74 kg of Erythritol and 42 kg of HTO. In the charging process, electrical boiler heated HTO first, and then HTO was pumped into the bottom of the TES container to melt Erythritol directly. In the discharging process, heat was transferred to the cooling water through a plate heat exchanger. Results show that, the sub-cooling problem of Erythritol, which was found in the static experiments, was totally solved by dynamic heat exchange between Erythritol and HTO. During the whole process, the two liquid phases (oil and melted Erythritol) were separated clearly due to the big difference of their densities, and meanwhile a foam layer was also observed between the two sectors. In the charging process, the higher the flow rate of HTO, the less the charging time was needed, which resulted in the lower charging heat consumption. In the discharging process, the maximum heat of 10.6 kWh was released with the HTO flow rate of 12.5 l/min, which accounted for 80.9 % of the theoretical heat capacity of the TES container.

Place, publisher, year, edition, pages
2011.
Keyword [en]
Mobilized thermal energy storage system; Heat recovery; Phase change materials; distributed heating
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-10640OAI: oai:DiVA.org:mdh-10640DiVA: diva2:359505
Conference
International Conference on Applied Energy, MAY 16-18, 2011 PERUGIA, ITALY
Projects
Ångpanneföreningens Forskningsstiftelse (ÅF), Sweden
Available from: 2010-10-28 Created: 2010-10-28 Last updated: 2016-01-11Bibliographically 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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