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Exergy and Parametric Analysis: Methods and Concepts for a Sustainable Built Environment
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
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: urn:nbn:se:kth:diva-105380ISBN: 978-91-7501-539-2 (print)OAI: oai:DiVA.org:kth-105380DiVA: diva2:570931
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
List of papers
1. Sustainability assessment of renovation packages for increased energy efficiency for multi-family buildings in Sweden
Open this publication in new window or tab >>Sustainability assessment of renovation packages for increased energy efficiency for multi-family buildings in Sweden
2012 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 61, 140-148 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we propose a method for assessing renovation packages drawn up with the goal of increasing energy efficiency. The method includes calculation of bought energy demand, life-cycle cost (LCC) analysis and assessment of the building according to the Swedish environmental rating tool Miljöbyggnad (MB). In this way the methodology assesses economic, indoor environmental quality (IEQ) and specifically environmental aspects associated with energy demand of such packages from a sustainability point-of-view. Through MB, energy efficiency packages are placed in context with other necessary measures required to improve environmental performance in buildings, providing a consistent and systematic basis other than simply financial performance by which to compare capital improvements. The method is further explained and analyzed by applying it in three case studies. In each case study a multi-family building representing a typologically significant class in the Swedish building stock is considered, and for each building a base case and two renovation packages with higher initial investment requirement and higher energy efficiency are defined. It is shown that higher efficiency packages can impact IEQ indicators both positively and negatively and that packages reducing energy demand by approx. 50% have somewhat higher LCC. Identified positive IEQ impacts point to added value for packages that may not otherwise be communicated, while negative impacts identify areas where packages need to be improved, or where MB indicators may be referred to as specifications in procurement procedures.

Keyword
Buildings, Sustainability, Environmental Rating Tools, Life-cycle costing
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-105422 (URN)10.1016/j.buildenv.2012.11.019 (DOI)000315754600013 ()2-s2.0-84872812419 (Scopus ID)
Projects
MECOREN
Funder
Swedish Research Council Formas
Note

QC 20130215. Updated from In press to published.

Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2017-12-13Bibliographically approved
2. The application of the parametric analysis for improved energy design of a ground source heat pump for residential buildings
Open this publication in new window or tab >>The application of the parametric analysis for improved energy design of a ground source heat pump for residential buildings
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
Keyword
Parametric analysis, GSHP, Energy, Residential buildings
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-105421 (URN)10.1016/j.enbuild.2013.03.050 (DOI)000320909500012 ()2-s2.0-84877789247 (Scopus ID)
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
3. Exergy analysis of single and multistep thermal processes
Open this publication in new window or tab >>Exergy analysis of single and multistep thermal processes
2011 (English)Conference paper, Published paper (Refereed)
Abstract [en]

The present paper introduces the concepts of exergy and treats it applications to analysis of the gain in exergy efficiency between one step and multi-step thermal processes. The analysis, which is carried out with the Excel based SEPE program, is exemplified with the comparison between single step and two-steps heat pump setup for providing heat to a heat floor system and a domestic hot water. The paper discusses the use of the concept of exergy efficiency as a measure of success for design of a heat pump application and how the use of information on exergy destruction and temperature levels in different parts of the system add a new perspective to the analysis and the evaluation of the system performance. The paper shows how this information can be used to improve the system configuration and also the operation of the system for given boundary conditions. This is especially useful when the energy from the low temperature sources is can be utilized at different temperature or quality levels such as for space heating and domestic hot water.

Keyword
thermal processes, exergy
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-53132 (URN)
Conference
2nd International Exergy, Life Cycle Assessment, and Sustainability Workshop & Symposium (ELCAS2) 19 - 21 June, 2011, NISYROS - GREECE
Note
QC20120116Available from: 2012-01-16 Created: 2011-12-22 Last updated: 2012-11-21Bibliographically approved
4. An Application of the Screening Analysis to Rank the Potential for the Reduction of the Energy Demand in Renovation
Open this publication in new window or tab >>An Application of the Screening Analysis to Rank the Potential for the Reduction of the Energy Demand in Renovation
(English)Article in journal (Other academic) Submitted
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-105420 (URN)
Note

QS 2012

Available from: 2012-11-21 Created: 2012-11-21 Last updated: 2012-11-21Bibliographically approved
5. Estimating exergy prices for energy carriers in heating systems: Country analyses of exergy substitution with capital expenditures
Open this publication in new window or tab >>Estimating exergy prices for energy carriers in heating systems: Country analyses of exergy substitution with capital expenditures
Show others...
2011 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 43, no 12, 3609-3617 p.Article in journal (Refereed) Published
Abstract [en]

Exergy represents the ability of an energy carrier to perform work and can be seen as a core indicator for measuring its quality. In this article we postulate that energy prices reflect the exergy content of the underlying energy carrier and that capital expenditures can substitute for exergy to some degree. We draw our line of argumentation from cost and technology data for heating systems of four European countries: Austria, Finland, The Netherlands, and Sweden. Firstly, this paper shows that the overall consumer costs for different heating options, widely installed in those countries, are in the same range. In this analysis we derived an overall standard deviation of about 8%. Secondly, additional analysis demonstrates that the share of capital costs on total heating cost increases with lower exergy input. Based on the data used in this analysis, we conclude that for the case of modern cost effective heating systems the substitution rate between exergy and capital is in the vicinity of 2/3. This means that by reducing the average specific exergy input of the applied energy carriers by one unit, the share of capital costs on the total costs increases by 2/3 of a unit.

Keyword
Exergy, Energy prices, Buildings, Heating
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-65554 (URN)10.1016/j.enbuild.2011.09.034 (DOI)000298268600037 ()2-s2.0-80755137040 (Scopus ID)
Note

QC 20120227

Available from: 2012-02-08 Created: 2012-01-25 Last updated: 2017-12-13Bibliographically approved

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