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Modelling the dynamics of domestic low-temperature heat pump heating systems for improved performance and thermal comfort: a systems approach
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The present environmental concerns and the rising human requirement for solutions with better comfort and lower costs have resulted in an increased awareness for the energy use in the built environment. Technical advances in building structural systems and materials, heating and other comfort-providing systems and controlling strategies all lead to the integration of building technology with the function of buildings and the aesthetics. Therefore, in the process of improving the performance of energy systems and increasing the energy efficiency, integrated system approaches are of high importance. Performing the necessary energy analysis before any construction-installation occurs can help designers and decision makers reach guided solutions. Hence, a broad range of calculation tools for evaluating the operation of energy systems and the controls in buildings have been developed the latest years with different levels of complexity and angles of focus.

However, research and development regarding holistic energy system designs and techniques are in their infancy. The standard tactic has been to isolate system parts, study them as stand-alone sub-systems and focus on optimising components or processes of a complex function. In the present study, it is demonstrated the necessity for uniting energy engineers, architects, installers and technicians regarding decision making upon the energy use for heating, ventilation and air-conditioning (HVAC) in the built environment. Systems approach has been employed for studying the research issue that is presented in the current thesis. An extended part of this treatise has been devoted to systems thinking in practice.

The thesis demonstrates systematic methods of modelling and analysing certain, integrated, domestic, HVAC applications. The reference system boundaries enclose the building as a construction and as a dynamic function, a comfort-providing system based on a heat pump, a low-temperature hydronic heat distribution system and controls in a residential application. Obviously, these are not the only components met in a hydronic heating system. Numerous pieces of equipment, as piping, circulating pumps, expansion tanks, zone valves, relief valves and other essential elements are needed to make a safe and functional heating system. However, this study focuses on the analysis of the chosen reference system. Several models have been developed in the computational tools of TRNSYS and EES. These tools have been employed because they allow co-solving, hence the integrated system as well as the interaction between the different parts of the system can be studied.

The foremost result of this study is that approaching the system as a whole provides a better picture of the operation of every system component and the interaction between them. Explanations are given for the parameters that have a significant impact on the system’s performance. The thesis shows the importance of factors that are not easy to predict, as well as the difference in the building’s behaviour under fast changing thermal loads when the incorporated thermal mass is altered. Finally, implementing sophisticated controls for reducing the energy costs without compromising thermal comfort is vital.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , 131 p.
Series
Trita-REFR, ISSN 1102-0245 ; 05:46
Keyword [en]
Technology, heat pump, domestic heating and ventilation, low-temperature hydronic heat distribution, systems approach, integration, simulation, energy efficiency
Keyword [sv]
TEKNIKVETENSKAP
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-269ISBN: 91-7178-018-1 (print)OAI: oai:DiVA.org:kth-269DiVA: diva2:8383
Public defence
2005-06-14, Sal M3, Brinellvägen 64, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101008Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-10-08Bibliographically approved
List of papers
1. Towards Energy-Use Optimisation of a Domestic Heating System based on a Heat Pump
Open this publication in new window or tab >>Towards Energy-Use Optimisation of a Domestic Heating System based on a Heat Pump
2001 (English)In: Strojniski vestnik, ISSN 0039-2480, Vol. 47, no 8, 506-511 p.Article in journal (Refereed) Published
Abstract [en]

The overall efficiency of a heat pump system i.e. heat source, heat pump unit and distribution system, is strongly affected by the design temperature levels of the system. The temperature levels influence the performance, in every single process from the time that energy flows from the ambient to the heat source until the heat is released from the building envelope to the environment. The heat exchanging processes in every step affect the energy flow, the losses and generally the energy efficiency of the heating system. The objective of this paper is to show how the different temperature levels influence the energy efficiency and the performance of a heat pump system for domestic applications. The heat pump unit and the heat distribution system are approached as an integrated system. Hence, calculations are performed in order to estimate possibilities for energy savings and for improving the overall efficiency of a heating system based on a heat pump. The results show mainly the increasing call reducing the supply temperature of heat distribution systems. The influence of the refrigerant characteristics on optimal heat pump designs will be discussed.

Keyword
Energy efficiency, Heat exchangers, Heat losses, Optimization, Refrigerants
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5305 (URN)000173235400025 ()
Note
QC 20101004Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
2. Modelling the Performance of a Domestic Low-Temperature Heating System based on a Heat Pump
Open this publication in new window or tab >>Modelling the Performance of a Domestic Low-Temperature Heating System based on a Heat Pump
2002 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5306 (URN)
Conference
Proceedings of the 9th International Refrigeration and Air Conditioning Conference at Purdue, 2002,July 16-19; West Lafayette, IN, USA
Note

QC 20101008

Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2014-10-03Bibliographically approved
3. Energy Analysis of a Low-Temperature Heat Pump Heating System in a Single-Family House
Open this publication in new window or tab >>Energy Analysis of a Low-Temperature Heat Pump Heating System in a Single-Family House
2004 (English)In: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 28, no 1, 1-12 p.Article in journal (Refereed) Published
Abstract [en]

 Energy costs and environmental concerns have made energy optimisation a viable option for buildings. Energy-efficient heating systems together with an effective use of buildings thermal mass and tightness have a significant impact on the energy requirement and on the possibility for sizeable running cost savings. In this study we use the simulation tool TRNSYS-EES to model and analyse the performance of a residential house and the low-temperature heating system that serves its thermal needs. The building is a single-family house with controlled ventilation and the chosen heating system is a hydronic floor heating system connected to an exhaust air heat pump. The aim of the simulation is to study the performance of the building, the heating system and the controls in an integrated manner. Overall, the results indicate that the energy efficiency issue implicates system design and system thinking concerns as well as techno-economic difficulties. Them controls and the choice of the operation mode are of a great importance.

Keyword
heat pump, floor heating, exhaust air, tight building construction, ventilation, controls, simulation, co-solving
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5307 (URN)10.1002/er.947 (DOI)000188544100001 ()2-s2.0-0442312924 (Scopus ID)
Note
QC 20100913Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
4. Influence of the Design Criteria on the Operation of a Domestic Heat Pump Heating System
Open this publication in new window or tab >>Influence of the Design Criteria on the Operation of a Domestic Heat Pump Heating System
2003 (English)In: Proceedings of the 21st IIR International Congress of Refrigeration, 2003, Vol. 28, no 1Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5308 (URN)
Conference
Proceedings of the 21st IIR International Congress of Refrigeration, 2003 August 17-22; Washington D.C., USA
Note
QC 20101008Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2010-10-08Bibliographically approved
5. Modelling and Simulation Results for a Domestic Exhaust-Air Heat Pump Heating System
Open this publication in new window or tab >>Modelling and Simulation Results for a Domestic Exhaust-Air Heat Pump Heating System
2005 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 28, no 7, 1048-1056 p.Article in journal (Refereed) Published
Abstract [en]

Energy consumption in residential buildings has gained an increasing interest the latest years due to the rising demand for efficient energy use and higher comfort standards. In tight building constructions with controlled ventilation, heat recovery with exhaust-air heat pump connected to floor heating is regarded as energy efficient heating system that optimises the energy use in buildings while maintaining an acceptable level of thermal comfort. In this study, we use the computational tools TRNSYS and EES to model and analyse the performance of a residential house, its ventilation system and its floor heating system based on an exhaust air heat pump. The system analysis focuses particularly on the influence of internal and solar gains on the operation of the heating system and the thermal comfort of the house. Furthermore, the way that gains influences the performance of the floor heating system is examined. Overall, the results bring to light the impact of factors that are not easy to predict on the indoor climate and the thermal comfort.

Keyword
Energy consumption, Floor, Heat pump, Heat recovery, Heating, Modelling, Residential application, Simulation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5309 (URN)10.1016/j.ijrefrig.2005.03.007 (DOI)000232181800008 ()2-s2.0-24344480867 (Scopus ID)
Note
QC 20100923. Uppdaterad från Accepted till Published (20100923).Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved
6. Investigating Control Strategies for a Domestic Low-Temperature Heat Pump Heating System
Open this publication in new window or tab >>Investigating Control Strategies for a Domestic Low-Temperature Heat Pump Heating System
2006 (English)In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 29, no 4, 547-555 p.Article in journal (Refereed) Published
Abstract [en]

Despite energy conservation regulations and efforts for improving HVAC operations, numerous domestic buildings do not perform energy efficiently and many times the indoor environment is far away from specified comfort levels. Especially in houses served from low-temperature heating systems the low ability of the heating system to respond to fast changing thermal loads is common. In such cases, the implementation of new, sophisticated controls is an important issue. In this study, we use a reference model of a domestic low temperature heat pump heating system developed in TRNSYS-EES and analyse its operation. Several methods of control strategies have been applied for specified time periods in order to keep the comfort within reasonable ranges. Prognostic climatic control and increased ventilation rates when required are some of these methods. The results depict the influence of the control method on the indoor temperature and the comfort indexes of PMV and PPD. The highest indoor temperature difference for a chosen day reaches 4 degrees C when there is no shading and when there is internal shading with the option of applying prognostic climatic control. Generally, the findings highlight the importance of dynamics in controlling functions and the difficulty of incorporating in models unpredictable factors as the solar radiation.

Keyword
Automatic, Domestic application, Floor, Heat pump, Heating, Modelling, Regulation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-5310 (URN)10.1016/j.ijrefrig.2005.10.009 (DOI)000238333600004 ()2-s2.0-33646500970 (Scopus ID)
Note
QC 20100920. Uppdaterad från Submitted till Published (20100920).Available from: 2005-06-07 Created: 2005-06-07 Last updated: 2017-12-04Bibliographically approved

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