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A network-based methodology for the simulation of borehole heat storage systems
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
2014 (English)In: Renewable energy, ISSN 0960-1481, Vol. 62, 265-275 p.Article in journal (Refereed) Published
Abstract [en]

The optimization of strategies to operate borehole thermal energy storage systems can play an important role for the exploitation of this technology. Available tools utilized for the design of borehole fields don't consider these aspects in the calculation. For this reason a network-based methodology which gives a sufficient level of detail to describe different system operation strategies has been developed. In particular, the method allows to calculate how the heat is distributed among the borehole heat exchangers in the field according to the way the brine is supplied to the borehole heat storage system. This enables to test the same borehole field configuration pattern for different piping arrangement. An example of application where a simultaneous need of heating and cooling is met by extracting and injecting heat in different region of the ground storage is considered to illustrate the potential of the method.

Place, publisher, year, edition, pages
2014. Vol. 62, 265-275 p.
Keyword [en]
Borehole heat exchanger, Finite line source, Ground heat storage
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-139252DOI: 10.1016/j.renene.2013.07.020ISI: 000328095000030ScopusID: 2-s2.0-84881256923OAI: diva2:685168

QC 20140109

Available from: 2014-01-09 Created: 2014-01-08 Last updated: 2015-05-07Bibliographically approved
In thesis
1. Developments in Ground Heat Storage Modeling
Open this publication in new window or tab >>Developments in Ground Heat Storage Modeling
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ground heat storage systems can play an important role for the reduction of green house gases emissions by increasing the exploitation of renewable energy sources and “waste heat” with a consequent diminution of the use of fossil fuels.

A ground heat storage consists in an array of vertical boreholes placed in such a way that promotes the mutual thermal interaction between the ground heat exchangers creating the necessary conditions required to effectively store and retrieve heat. Suitable modeling tools for the estimation of the thermal behavior of these systems are very important to build installations yielding economical performance compatible with what expected during the design phase.

This thesis aims at giving a contribution in the development of the thermal modeling of borehole heat storage systems. The main objective is introducing in the modeling process a few features that are not usually considered in state of the art models, with the goal of improving the representation of the physical phenomena. These features are the mathematical description of the topology of the borehole heat exchangers network, and the modeling of borehole fields with arbitrarily oriented boreholes.

The detailed modeling of the topology of the borehole heat exchangers is approached with a network model. The overall geothermal system is discretized into smaller systems called components. These are linked between each other in a network fashion to establish the logical relations required to describe a given boreholes connections arrangement. The method showed that the combination of a sufficient level of discretization of the system and of a network representation yields respectively the granularity and the flexibility required to describe any borehole field connections configuration.

The modeling of non-vertical borehole fields is approached by developing a method for the calculation of g-functions for these configurations. The method is an extension of a recent work done by Cimmino on the computation of g-functions for vertical borehole fields. This modeling technique is based on describing boreholes as sets of stacked finite line sources and on the superposition principle. This approach requires the computation of response factors relative to couples of finite lines. A procedure for the fast computation of these response factors for the case of arbitrarily oriented lines is given. This yields computational performance that guarantees the practical feasibility of the methodology.

The last part of the thesis deals with the modeling of the storage system from a broader perspective. The borehole field is considered as part of a larger system constituted by several interacting components (i.e. heat pump, building, etc.). Interactions play a key role in the resulting overall performance of these systems. The analysis of the mutual relations between building envelope and borehole field design is utilized as an example to highlight advantages and challenges of strategies yielding a more integrated design.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 73 p.
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5536 ; 2015:01
Borehole fields, g-functions, network, inclined, integrated design
National Category
Energy Engineering Building Technologies
Research subject
Energy Technology; Civil and Architectural Engineering
urn:nbn:se:kth:diva-166219 (URN)978-91-7595-566-7 (ISBN)
Public defence
2015-05-29, Kollegiesalen, Brinnelvägen 8, KTH, Stockholm, 13:00 (English)

QC 20150507

Available from: 2015-05-07 Created: 2015-05-05 Last updated: 2015-05-07Bibliographically approved

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