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District heating system analysis and challenges within the urban transformation of Kiruna
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. (Energiteknik)
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is currently an ongoing urban transformation in a small Swedish town named Kiruna, it is located in the very north of Sweden well above the Arctic Circle in a sub-arctic climate. Large part of the town will be relocated due to the ground deformation that is caused by the progressing iron ore mining activity and it is affecting all infrastructures of the town. This thesis aims to accomplish a holistic analysis on the district heating (DH) system for the town of Kiruna and its future challenges.

Energy companies with a DH system recognize the importance in having a good understanding about the network characteristics, for obtaining an efficient and stabile heat delivery to the end-users. In this thesis, a method for modeling and simulation of meshed DH networks is described, that makes it possible to study and analyze the flow pattern in order to locate non-obvious paths, bottlenecks and overloaded pipes.

For carrying out the DH simulations a fundamental input is to set the thermal losses for each pipe segment in the model, a fictitious series with all pipe diameters is created which corresponds to the annual losses in the real network. In comparison with the pipes series manufactured today the created one is best described by the series with least insulation and highest thermal losses. The studied network has its origin in the 60th and is the sum of the different piping technics that has been valid over time, this mixture is positioning the thermal performance as a close to a worst-case scenario.

To the meshed DH network a number of heat production sites are connected for delivering the thermal requested by the end-users, each site consisting of several boilers and using different resources. A hybrid evolutionary-Mixed Integer Linear Programing (MILP) optimization approach is developed and applied for finding the cost-optimal heat production for three scenarios in combination of two heating demand levels. It is stated that no matter the geographically location of the site the cheapest resource should always be favorable as fuel, in the case when the same resource is viable at different sites a differentiated heat production is obtained. The supply temperature from each site is found to be the one lowest possible in order to serve all site-concerned end-users with a temperature level high enough for hot water production. The findings recommend a network temperatures reduction with the consequence in higher cost related to pumping work, but is lower than the savings due to the reduction in thermal losses.

In order to provide the relocated part of the town with DH the hybrid evolutionary-MILP optimization routine is reshaped for finding different alternatives for network expansion layouts. The result is presented as a multi objective analysis between the operation cost and installation cost, showing the complete spectra of all optimal possible solutions and how the different cost correlate to each other. In this way, the outcome can be used for support in decision making, helping network owners is their planning and pipe sizing for new areas.

For constructing the buildings that will populate the new city-area the Swedish government has stated a number of recommendations for achieving livable thermal indoor climate. An investigation is carried out analyzing the impact from the usage of three different heating system; air/air heat pump, air heating and floor heating in a low energy family house, where the first two system are aimed to use heat from the DH network. The analysis show that only the floor heating system satisfies the recommendations stated, but with carefully planning an air heating system could also fulfill the recommendations. Further, a techno-economical evaluation declares that the cheapest heating cost over 30 years is by using an air/air heat pump. In order to make DH competitive as heating source the needed price reduction is found for the hydronic floor and air heating system.

Finally, three different building energy performance scenarios are studied in conjunction with the urban transformation in combination with the suggested energy measures from the Energy Performance certificates (EPC). In order to reach the national target entailing a reduction of 50% until 2050 all re-built buildings have to be built with passive standard and all advised measures in the EPC has to be carried out. Wort noticing is that the scenarios is analyzed as part of a 3-D City Model, which is found to be a worthwhile working tool for staff dealing with energy related issues.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2017.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keyword [en]
District heating, analysis, optimization, design, heat production
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-63091ISBN: 978-91-7583-894-6 (print)ISBN: 978-91-7583-895-3 (electronic)OAI: oai:DiVA.org:ltu-63091DiVA: diva2:1089592
Public defence
2017-06-15, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2017-04-24 Created: 2017-04-20 Last updated: 2017-05-19Bibliographically approved
List of papers
1. A method for the simulation and optimization of district heating systems with meshed networks
Open this publication in new window or tab >>A method for the simulation and optimization of district heating systems with meshed networks
2015 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 89, 555-567 p.Article in journal (Refereed) Published
Abstract [en]

There are two main methods nowadays for modeling district heating systems, but a key disadvantage of both is that a real network containing loops cannot be described without artificial simplifications in order to eliminate those distinguishing features. However, loops are very common in mature networks that have developed a meshed structure, and make the distribution of mass and heat flows quite characteristic. For this reason, a new process integration method for modeling complex district heating systems containing loops is described in this paper. This method makes it possible to analyze how loops and bottlenecks affect the behavior of the network, as well as the distribution path of the thermal energy in it. The district heating system in the town of Kiruna (located in the north of Sweden) has a complex design with several loops and part of it is used in the paper as an example of application.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-9152 (URN)10.1016/j.enconman.2014.10.002 (DOI)7b800504-b27d-4e1c-ba92-dcf3a103f468 (Local ID)7b800504-b27d-4e1c-ba92-dcf3a103f468 (Archive number)7b800504-b27d-4e1c-ba92-dcf3a103f468 (OAI)
Note
Validerad; 2015; Nivå 2; 20141029 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-04-20Bibliographically approved
2. Evaluation of losses in district heating system, a case study
Open this publication in new window or tab >>Evaluation of losses in district heating system, a case study
2013 (English)Conference paper, Presentation (Refereed)
Abstract [en]

To be able to create a model that accurately describes a district heating system, it is important to identify the thermal losses and how they are distributed. However, general methods targeting the determination of losses are scarce in the literature. In the current case the losses for a district heating system in Kiruna, a town in northern Sweden, has been estimated in the year 2010 to be 12%, which is in the range for a typical Swedish network. Unfortunately, detailed information of the thermal losses is lacking.In this paper two methods to determine loss distribution in a district heating system are presented.Two databases of pipe lengths and diameters have been compiled for two piping categories, loops and feeds. Any missing data regarding pipe diameters in the map has then been determined with the two different methods.In the first method average pipe diameters for loops and feeds are calculated. All pipes with unknown diameter are then assumed to have the average one. The second method considers a percentage based distribution of known diameters and assigns the same distribution to the missing pipe diameters. The losses were estimated in the whole system according to the data from a pipe producer catalogue, in which losses are calculated according to current European standard. The results show that the losses in the system are similar to the losses caused by pipes with the lowest insulating capacity.By using the two methods two fictitious pipe series reproducing exactly the losses in the system are created by scaling the calculated losses of the catalogue pipe series which would give the most similar losses (the one with the lowest insulating capacity). This adjustment was +3.1% by using the first method, and +4.9% by using the second method.The major conclusion of this study is that, both methods can be used for calculating the distribution of thermal losses in the district heating system of Kiruna; moreover, this kind of analysis can be an important tool for analyzing investments in the district heating network in Kiruna.

Keyword
Engineering mechanics - Mechanical and thermal engineering, District heating, Evaluation, Losses, Pipe series, Case study, Teknisk mekanik - Mekanisk och termisk energiteknik
National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-35161 (URN)84903555210 (ScopusID)993dab3f-390e-4afa-971f-2ff67d74beb7 (Local ID)993dab3f-390e-4afa-971f-2ff67d74beb7 (Archive number)993dab3f-390e-4afa-971f-2ff67d74beb7 (OAI)
Conference
International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems : 16/07/2013 - 19/07/2013
Note
Godkänd; 2013; 20140305 (matves)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-04-20Bibliographically approved
3. Simulation and analysis of a meshed district heating network
Open this publication in new window or tab >>Simulation and analysis of a meshed district heating network
2016 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 122, 63-73 p.Article in journal (Refereed) Published
Abstract [en]

The flow distribution in a district heating network tends to become no longer obvious when system design is developed and its complexity increased. As a consequence, the network owner, often the local energy company, is in need of a simulation program to have the possibility of analysing network behaviour and expand the understanding about the operation of district heating system. In this paper, a simulation tool developed in MATLAB/Simulink is applied in order to analyse the flow distribution in the district heating network of the town of Kiruna (Sweden). The network in Kiruna has been developing since the 60s and is today a complex network with a meshed structure, i.e. it is formed by a set of loops from which secondary branches depart. The simulation tool is part of a methodology that has specifically been developed to analyse the flow pattern in such kind of networks without altering their physical structure, and it is expected to be a valuable tool for the redesign of the network in the forthcoming relocation of some of the urban districts. The results about the current network configuration show that only a few pipes in the network are exceeding the levels of heat flow recommended by pipe manufacturers. The largest drops in pressure and temperature from the heat production site to the nodes serving the main consumer areas are within 1.2 bar and 9 °C in the days of highest demand.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-5877 (URN)411b63db-cfe4-4756-852e-77f5593f749f (Local ID)411b63db-cfe4-4756-852e-77f5593f749f (Archive number)411b63db-cfe4-4756-852e-77f5593f749f (OAI)
Note
Validerad; 2016; Nivå 2; 20160530 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-04-20Bibliographically approved
4. Optimization of multi-source complex district heating network, a case study
Open this publication in new window or tab >>Optimization of multi-source complex district heating network, a case study
2017 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 126, 53-63 p.Article in journal (Refereed) Published
Abstract [en]

The level of complexity for a district heating network increases with the maturity of the network, and this affects the pattern of the distribution of the hot water from the heat production sites to the end users. The majority of district heating systems are also multi-source networks, typically supported with heat from one main production site and other smaller satellite sites that are activated when required. In general, local energy companies have a lack of knowledge regarding how a meshed network behaves when different production sites are operated. The schedule of heat generation at the different sites is often based on staff experience and some general rules of thumb.

In this paper a method for modeling and simulating complex district networks is further developed in order to optimize the total operating costs of a multi-source network, with constraints on the pressure and temperature levels in the user areas and on the heat generation characteristics at each production site.

The optimization results show that the usage of the cheapest resources is preferred to a distributed generation of heat, even if some of the pipes may exceed the recommended thermal load capacity. The main site water supply temperature is found to be the lowest allowed by the constraint on the temperature of the water supplied to the end users, since the decrease of the costs associated with the lower thermal losses in the network is not counterbalanced by the increase of those associated with the pumping power of a larger water mass flow rate.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-62320 (URN)10.1016/j.energy.2017.03.018 (DOI)2-s2.0-85014911271 (ScopusID)
Note

Validerad; 2017; Nivå 2; 2017-03-15 (rokbeg)

Available from: 2017-03-06 Created: 2017-03-06 Last updated: 2017-04-20Bibliographically approved
5. CFD simulation and evaluation of different heating systems installed in low energy building located in sub-arctic climate
Open this publication in new window or tab >>CFD simulation and evaluation of different heating systems installed in low energy building located in sub-arctic climate
2015 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 89, 160-169 p.Article in journal (Refereed) Published
Abstract [en]

Computational Fluid Dynamics (CFD) simulations were used to study the indoor climate in a low energy building in northern Sweden. The building’s low heat requirement raise the prospect of using a relatively simple and inexpensive heating system to maintain an acceptable indoor environment, even in the face of extremely low outdoor temperature. To explore the viability of this approach, the indoor climate in the building was studied considering three different heating systems: a floor heating system, air heating through the ventilation system and an air heat pump installation with one fan coil unit. The floor heating system provided the most uniform operative temperature distribution and was the only heating system that fully satisfied the recommendations to achieve tolerable indoor climate set by the Swedish authorities. On the contrary, air heating and the air heat pump created a relatively uneven distribution of air velocities and temperatures, and none of them fulfills the specified recommendations. From the economic point of view, the air heat pump system was cheaper to be installed but produced a less pleasant indoor environment than the other investigated heating systems.

National Category
Energy Engineering
Research subject
Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-11144 (URN)10.1016/j.buildenv.2015.02.024 (DOI)a0dde22a-a36f-4f00-a108-d848722aa479 (Local ID)a0dde22a-a36f-4f00-a108-d848722aa479 (Archive number)a0dde22a-a36f-4f00-a108-d848722aa479 (OAI)
Note
Validerad; 2015; Nivå 2; 20150305 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-04-20Bibliographically approved
6. Energy performance certificates and 3-dimensional city models as a means to reach national targets: A case study of the city of Kiruna
Open this publication in new window or tab >>Energy performance certificates and 3-dimensional city models as a means to reach national targets: A case study of the city of Kiruna
2016 (English)In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 116, 42-57 p.Article in journal (Refereed) Published
Abstract [en]

Enhanced dissemination of information regarding energy saving and climate change targeted toward property owners is considered to be an important strategy in order to reach the Swedish national target of energy efficiency in the building sector by 2050. Here the municipality energy advisors and the national register for energy performance certificates can facilitate the mitigation of energy use in the building stock. So far few studies have focused on the practical road map to the national target of energy use on the city/district level and to the communication aspects with stakeholders in the creation of energy city models.In this paper a city energy model is developed based on the requests and need for visualization from a group of energy advisors. Six different scenarios are studied in order to analyze the possibility of reaching the energy targets specified by the government in the town of Kiruna. The results show that: (1) it is possible to automatically create city energy models using extract, transform and load tools based on spatial and non-spatial data from national registers and databases; (2) city energy models improve the understanding of energy use in buildings and can therefore be a valuable tool for energy advisors, real estate companies and urban planners. The case study of Kiruna showed that the proposed energy saving measures in the energy performance certificates need to be implemented and new buildings in the urban transformation must be of high energy standard in order to reach the national target in Kiruna.

National Category
Construction Management Energy Engineering
Research subject
Construction Engineering and Management; Energy Engineering
Identifiers
urn:nbn:se:ltu:diva-14165 (URN)10.1016/j.enconman.2016.02.057 (DOI)d82fcec8-829a-4bc9-a429-8e0d2c0bcef3 (Local ID)d82fcec8-829a-4bc9-a429-8e0d2c0bcef3 (Archive number)d82fcec8-829a-4bc9-a429-8e0d2c0bcef3 (OAI)
Note
Validerad; 2016; Nivå 2; 20160310 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-04-20Bibliographically approved

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