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The application of the parametric analysis for improved energy design of a ground source heat pump for residential buildings
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.ORCID iD: 0000-0002-2300-2581
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.ORCID iD: 0000-0001-7073-2600
2013 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 63, 119-128 p.Article in journal (Refereed) Published
Abstract [en]

Energy use in buildings represents a major share of the overall energy used in developed countries. The reduction of the energy demand and the efficient energy use are often seen as feasible ways for a more sustainable energy use in the built environment. Ground source heat pumps (GSHPs) are efficient systems to supply heating and cooling energy to buildings but their design is critical for their performance. Furthermore, their performance depends on the cooling and heating demand and on the environmental conditions. The need for the end-use energy for a building supplied with GSHP has been studied with regard to four parameters in two different locations. The effect of two building performance parameters, roof and external walls insulation, and of two parameters affecting the performance of GSHP, boreholes spacing and number of boreholes, have been investigated by means of factorial analysis. Results show that from an energy point of view the optimal configurations of the boreholes change depending on the variation of building parameters such as insulation. The methodology proposed allows to quantify the impact of different design configurations on the need for end-use energy.

Place, publisher, year, edition, pages
Elsevier, 2013. Vol. 63, 119-128 p.
Keyword [en]
Parametric analysis, GSHP, Energy, Residential buildings
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-105421DOI: 10.1016/j.enbuild.2013.03.050ISI: 000320909500012Scopus ID: 2-s2.0-84877789247OAI: oai:DiVA.org:kth-105421DiVA: diva2:571011
Funder
Swedish Research Council FormasVINNOVASwedish Research Council
Note

QC 20130812. Updated from submitted to published.

Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Exergy and Parametric Analysis: Methods and Concepts for a Sustainable Built Environment
Open this publication in new window or tab >>Exergy and Parametric Analysis: Methods and Concepts for a Sustainable Built Environment
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy use in the world is continuously increasing. In the last 30 years the use of primary energy worldwide has more than doubled and it is mainly supplied with fossil fuels. A more efficient use of energy in the built environment has to be pursued if a more sustainable development is to be attained.

The housing sector accounts for a major share of the energy use. Both in residential and commercial buildings, energy is mainly used for heating. Heat is energy with low quality. Traditional energy analysis methods, by failing to consider the energy quality, cannot give a holistic insight of the potential for reducing the energy used in the built environment. Exergy, instead, provides a tool to quantify the energy quality based on thermodynamic grounds.

In this thesis a methodology based on both the reduction of the energy demand and exergy demand in buildings is proposed to mitigate the problems related to the energy use in buildings through a reduced and more efficient use of energy.

The complex relations between building parameters to reduce the energy demand are managed with parametric analysis tools. The potential for energy demand reduction is investigated by means of screening analyses, local sensitivity analyses and global methods. A method for assessing the potential reduction of the energy demand in existing buildings and to evaluate the cost-efficiency of renovation measures based on the screening analysis is introduced and tested on two building typologies. In parallel, a program tool for parametric energy simulations, Consolis Parametric, has been developed on the core of an existing dynamic software, Consolis Energy +.

Factorial analysis has been used to investigate the relations between the reduction of the energy demand and of the energy supply when ground source heat pumps are used for heating and cooling. Optimal configurations- dependent on the insulation of the building- of number of boreholes and spacing were identified for minimum electricity consumption.

In the second part of this thesis exergy is used as tool for the definition of the efficient energy use in the built environment. The analysis of a multi-step heat pump to supply energy at two temperature levels, for space heating and domestic hot water production, exemplified how the reduction of the exergy loss can lead to a more efficient use of energy. The analysis was performed by means of SEPE, a modular software program developed in this work for exergy analysis in buildings.

For the systematic reduction of the exergy losses in the built environment, an important prerequisite is the reduction of the exergy required by the building. Systems like floor heating and cooling, based on low difference emission temperature, are examples of low-exergy systems. Buildings with reduced need of exergy input increase the efficiency of systems like heat pumps and enhance the use of low quality energy, like waste heat and energy from low temperature renewable sources.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. x, 69 p.
Series
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5536 ; 209
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-105380 (URN)978-91-7501-539-2 (ISBN)
Public defence
2012-12-12, B2, Brinellvägen 23, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Formas
Note

QC 20121121

Available from: 2012-11-21 Created: 2012-11-20 Last updated: 2013-02-15Bibliographically approved
2. 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.
Series
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5536 ; 2015:01
Keyword
Borehole fields, g-functions, network, inclined, integrated design
National Category
Energy Engineering Building Technologies
Research subject
Energy Technology; Civil and Architectural Engineering
Identifiers
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)
Opponent
Supervisors
Funder
VINNOVA
Note

QC 20150507

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

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