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Lifetime Performance Assessment of Thermal Systems: Studies on Building, Solar and Disctrict Heating Applications
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The main questions today concerning thermal systems are their economical and environmental impacts. These entities are generally, at present, assessed on the basis of operation performances of newly installed/designed systems, during an assumed lifetime period. While this is the common way of perceiving thermal systems, performance-over-time will change as an effect of degradation, and not solely of different operation scenarios. How and to what extent is the question that needs assessing in order to evaluate if these changes will jeopardise the intended system performance requirement, hence service life (SL). The lack of knowledge/approaches and tools for assessing durability and performance-over-time of thermal systems complicates the task of incorporating these aspects in engineering. In turn, this pro-active assessment and analysis is in line with today’s performance based directives, laws and regulations; of which the working life is an essential part. The durability of materials, components and systems is not a topic that is an end in itself, but becomes a vital part in a comprehensive perspective as sustainability. The lifetime performance assessment of thermal systems, as presented in this thesis, shows that it is a vital part of the R&D in the quest of sustainable energy/thermal systems and energy use.

This thesis gives knowledge to the thermal (energy) system/technology R&D and engineering sector, regarding durability and lifetime performance assessment methodologies; but also to the durability of construction works sector, regarding the needs for assessing lifetime performance of materials and components in relation to system performance. It also presents descriptions of requirements on construction works. Specifically, the studies presented in the thesis show how durability and lifetime performance assessment of thermal systems may be sought, with knowledge on: methodologies, exposure test set-ups, modelling and the attainment and use of adequate tools. The main focus is on performance-over-time modelling, tying material/component degradation to altered thermal performance, thereby attaining performance-over-time assessment tools to be used in order to incorporate these aspects when engineering thermal systems; hence enabling the forecasting of SL. The presented work was predominantly done in association to the EU project ENDOHOUSING. The project developed a solar-assisted heat pump system solution, with heat storage, to provide the thermal energy to meet space heating, cooling and hot water requirements for domestic houses in different regions of the EU. The project constituted the platform for the work presented in this thesis, thereby outlining the main context with studies on durability and lifetime performance of:

  • flat plate solar collectors
  • ground heat sources/storages and interaction with a heat pump system
  • evaluation of the ENDOHOUSING solar-assisted heat pump system

The thesis also presents a study of SL prediction and estimation of district heating distribution networks (an additional thermal system application). In this particular context, the Factor Method is proposed as a methodology. The main issue of lifetime performance of thermal systems is how and to what extent performance reduction in individual materials or components influence the overall system performance, as the essence of energy/thermal system sustainability is system performance.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xvi, 112 p.
Keyword [en]
Lifetime performance, degradation, assessment, modelling, field exposure, thermal components and system
National Category
Building Technologies Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-10967ISBN: 978-91-7415-384-2 (print)OAI: oai:DiVA.org:kth-10967DiVA: diva2:233509
Public defence
2009-09-11, Gävle Teknikpark, Hörsalen, Nobelvägen 2, Gävle, 10:00 (English)
Opponent
Supervisors
Note
QC 20100810Available from: 2009-09-01 Created: 2009-09-01 Last updated: 2012-03-23Bibliographically approved
List of papers
1. On Reduced Energy Performance of a Solar-Assisted Heat Pump System due to Absorber Coating Degradation
Open this publication in new window or tab >>On Reduced Energy Performance of a Solar-Assisted Heat Pump System due to Absorber Coating Degradation
2005 (English)In: Proceedings of the 10th International Conference on Durability of Building Materials and Components (10DBMC), Lyon, France., 2005Conference paper, Published paper (Refereed)
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-19455 (URN)
Note
QC 20100810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-08-10Bibliographically approved
2. Long-Term Thermal Performance Modelling and Simulations of a Borehole
Open this publication in new window or tab >>Long-Term Thermal Performance Modelling and Simulations of a Borehole
2005 (English)In: Proceedings of the 7th Symposium on Building Physics in the Nordic Countries, Reykjavik, Iceland., 2005, 1-8 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the long-term thermal performance modelling and simulation of a single heat extraction borehole with a U-shaped pipe, by applying the Macro Element Modelling (MEM) method, developed by Schmidt (2004). The dynamic thermal performance of the ground around the borehole is analysed in the frequency domain. Thereafter, the ground properties are transformed into a network of discrete resistances and capacitances (RC’s) that together with the pipe, models the thermal performance of the borehole. The method allows the parameters of the RC- network components to be estimated and optimised for time domain simulations. The advantage of this modelling method is that it establishes a simplified yet accurate thermal borehole model, which requires less computing time and power compared to a traditional finite difference/element model. This makes it easier to perform several decades of long-term thermal performance simulations. In this paper the U-pipe was modelled by applying a star resistance network that calculates the weighted heat fluxes between the solid borehole and the U-pipe. The presented work shows that at small temperature increases and at relative large fluid velocities the U-pipe fluid temperature can be seen as rising linearly. This provides the borehole modelling with the possibility to model the entire borehole construction by using only one macro element. To compensate for any errors when using the linearly increasing fluid temperature for calculating the energy extraction from the borehole, the total U-pipe star resistance network is compensated. The U-pipe star network was also compared with a FEM (Finite Element Method) simulation, showing that the correspondence between the two models is good. The half 5-node network that was used by Schmidt (2004) for modelling the solid construction of the borehole was modified in this paper, with an additional resistance to ensure the stability of the network when simulation long-term heat extraction periods. The borehole RC-network was optimised for a time period of 100 years. The results from the long-term performance simulation made with the derived borehole model, were also compared to other presented borehole simulations. The model proved to have, at a first stage of comparison, a good correspondence with the other presented results.

Keyword
Borehole, long-term thermal performance, Macro Element Modelling (MEM), simulations.
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-19456 (URN)
Note
QC 20100810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-11-17Bibliographically approved
3. Natural and semi-natural field exposure testing and analysis, on optical degradation of a building integrated unglazed solar collector surface
Open this publication in new window or tab >>Natural and semi-natural field exposure testing and analysis, on optical degradation of a building integrated unglazed solar collector surface
2008 (English)In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 41, no 6, 1057-1071 p.Article in journal (Refereed) Published
Abstract [en]

Durability is of great importance when considering sustainable energy systems. In turn it lays emphasis on assessing performance over time of energy systems and components. This paper presents a study on optical degradation of a building-integrated Unglazed Solar Collector (USC) surface, by exposing USC specimens to a natural and semi-natural field exposure test. Particular interest is devoted to the semi-natural field exposure test method evaluation, and the degradation of optical properties. The study showed that about 11 months of field exposure testing did not cause any significant optical (total solar absorptance and IR emittance) or material (surface coating) degradation; although measurements revealed a decrease in specular reflectance as diffuse increased. It was likely due to surface pollution that predominantly consisted of quartz. The study also showed that it is possible to achieve a considerable increased moisture exposure on test surfaces (semi-natural field exposure test), through a relatively simple cooling device (Direct-Air Peltier-Element) and rough control strategy.

Keyword
natural and semi-natural field exposure, optical degradation, unglazed solar collector
National Category
Materials Engineering Building Technologies
Identifiers
urn:nbn:se:kth:diva-19457 (URN)10.1617/s11527-007-9306-1 (DOI)000256434800006 ()
Note
QC 20100810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
4. Use of a Peltier Element to Increase Time of Wetness of Unglazed Solar Collector Specimens in a Natural Field Exposure Test.
Open this publication in new window or tab >>Use of a Peltier Element to Increase Time of Wetness of Unglazed Solar Collector Specimens in a Natural Field Exposure Test.
2008 (English)In: Proceedings of the 11th International Conference on Durability of Building Materials and Components (11DBMC), Istanbul, Turkey., 2008Conference paper, Published paper (Refereed)
National Category
Materials Engineering Building Technologies
Identifiers
urn:nbn:se:kth:diva-19458 (URN)
Note
QC 20100810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-08-10Bibliographically approved
5. Simulated Long-Term Thermal Performance of a Building That Utilizes a Heat Pump System and Borehole.
Open this publication in new window or tab >>Simulated Long-Term Thermal Performance of a Building That Utilizes a Heat Pump System and Borehole.
2008 (English)In: Proceedings of the 11th International Conference on Durability of Building Materials and Components (11DBMC), Istanbul, Turkey., 2008Conference paper, Published paper (Refereed)
National Category
Building Technologies Materials Engineering
Identifiers
urn:nbn:se:kth:diva-19459 (URN)
Note
QC 2010810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2010-08-10Bibliographically approved
6. Life Cycle Management System: A planning tool supporting Long-term based design and maintenance planning
Open this publication in new window or tab >>Life Cycle Management System: A planning tool supporting Long-term based design and maintenance planning
2008 (English)In: 11th International Conference on Durability of Building Materials and Components, 2008Conference paper, Published paper (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-10308 (URN)
Conference
11th International Conference on Durability of Building Materials and Components
Note
QC 20100716Available from: 2009-05-06 Created: 2009-05-06 Last updated: 2012-03-23Bibliographically approved
7. A Steady State Thermal Duct Model Derived by Fin-Theory Approach and Applied on an Unglazed Solar Collector.
Open this publication in new window or tab >>A Steady State Thermal Duct Model Derived by Fin-Theory Approach and Applied on an Unglazed Solar Collector.
2009 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 10, 1838-1851 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (ID) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler ID analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no 'or negligible' temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the ID isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of events adopts a 1D heat flow that reassembles the conditions of the 1D simple model (for the assessed USC duct geometry); ID heat flow through the top and bottom fins/sheets as the duct wall reassembles a state of adiabatic condition.

Keyword
PERFORMANCE; DEGRADATION; VALIDATION; SYSTEMS; SURFACE; DESIGN; ENERGY
National Category
Building Technologies Materials Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-19461 (URN)10.1016/j.solener.2010.06.016 (DOI)000282498500009 ()2-s2.0-77956180250 (Scopus ID)
Note
QC 20100810, QC 20111110Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved
8. Status, needs and possibilities for servicelife prediction and estimation of district heating distribution networks
Open this publication in new window or tab >>Status, needs and possibilities for servicelife prediction and estimation of district heating distribution networks
2012 (English)In: Structure and Infrastructure Engineering, ISSN 1573-2479, E-ISSN 1744-8980, Vol. 8, no 1, 41-54 p.Article in journal (Refereed) Published
Abstract [en]

An optimised and proactive maintenance strategy aims to maximise the economical profit, minimise environmental impacts and keep the risk of failure to a low level. Implementation of such a strategy in the context of district heating requires efforts and abilities for predicting future performances and estimating service life of district heating components. A literature review on failures (damages and performance reductions) occurring on district heating pipes, reveals that failures in district heating pipes are mainly leaks due to corrosion or mechanical impacts and reduced thermal insulation performance: leaks being the more serious damage type. A feasible service life estimation method for this type of damage is the Factor Method. Since the application of this method within the context of DH pipes has not been found in other publications, this paper focuses on describing the method and discusses the possibilities on how to apply it in two specific cases with respect to leakage: service life estimation of repaired district heating pipe sections (i.e. maintenance of district heating network) and of district heating pipes in new or extended district heating networks. Particular attention is paid to which modifying factors should be considered and how to quantify them.

Keyword
district heating, maintenance strategy, service life, Factor Method
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-10311 (URN)10.1080/15732470903213740 (DOI)000302541400003 ()2-s2.0-84855962123 (Scopus ID)
Note
QC 20120509Available from: 2009-05-06 Created: 2009-05-06 Last updated: 2017-12-13Bibliographically approved
9. Build-up and long-term performance test of a full-scale solar-assisted heat pump system for residential heating in Nordic climatic conditions
Open this publication in new window or tab >>Build-up and long-term performance test of a full-scale solar-assisted heat pump system for residential heating in Nordic climatic conditions
2010 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 30, no 2-3, 188-195 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents the build-up and long-term performance test of a full-scale Solar-Assisted Heat Pump System (SAHPS) for residential heating in Nordic climatic conditions. This particular SAHPS was developed within the EU project ENDCHOUSING, by predominantly using components and techniques that are available on the market. The analysis primarily focuses on system performance, with emphasis on Heat Pump (HP) and total system Seasonal Performance Factor (SPF), based on long-term and full-scale operation. Analysis shows that despite unfavourable building conditions, for low energy use and utilisation of a SAHPS, the system was successfully in full operation (for about 2 years) fulfilling heating requirements. Data processing of the series representing the full year period of 2007(February)-2008(February), presented a HP and total SAHPS performance of. SPFHP = 2.85 and SPFSAHPS = 2.09. The authors argue that with an optimised SAHPS control and operation strategy, additional use of circulation pumps and energy (electricity) could be vastly reduced, hence attaining a SPFSAHPS value that is in parity with the SPFHP. As the Nordic (Swedish) Endohousing SAHPS has not yet been properly optimised/designed and installed in an appropriate house, the SPFHP = 2.85 is considered satisfactory.

Keyword
Solar-assisted heat pump system, Roof-integrated unglazed solar collector, Ground heat storage/source, Long-term, Full-scale, Test
National Category
Building Technologies Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-19462 (URN)10.1016/j.applthermaleng.2009.08.004 (DOI)000272001100015 ()2-s2.0-74449090530 (Scopus ID)
Note
QC 20100810Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2017-12-12Bibliographically approved

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