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Novel low temperature heat distribution technology
Halmstad University, School of Business, Engineering and Science, The Rydberg Laboratory for Applied Sciences (RLAS).ORCID iD: 0000-0003-2885-0923
Halmstad University, School of Business, Engineering and Science, The Rydberg Laboratory for Applied Sciences (RLAS).ORCID iD: 0000-0001-9069-0807
2018 (English)In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 145, p. 526-539Article in journal (Refereed) Published
Abstract [en]

Lower future heat demands and lower availability of non-fossil high temperature heat supply are expected future market conditions that restrain the long-term viability of contemporary district heating systems. Hence, current district heating technology should be enhanced to increase system performance in new heat distribution areas. This paper aims to outline a proposal for technical improvements required to achieve lower annual average return temperatures in new residential buildings to improve viability in future market conditions. The proposed technical solution consists of three principle changes: three-pipe distribution networks, apartment substations, and longer thermal lengths for heat exchangers. The three technical modifications aims at addressing system embedded temperature errors. Furthermore, a simulation model was developed to assess the proposed technical solution concerning different energy performances of buildings and different thermal lengths in heat exchangers. The results show that implementation of the three technical modifications reaches time-weighted annual average return temperatures of 17–21 °C with supply temperatures of about 50 °C. The results also verify the increased necessity to separate the network return flows into delivery and recirculation flows in residential substations as energy performance in buildings increase.

Place, publisher, year, edition, pages
London: Elsevier, 2018. Vol. 145, p. 526-539
Keywords [en]
Low temperature, District heating, Three-pipe system, Recirculation, 4GDH-3P
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:hh:diva-38360DOI: 10.1016/j.energy.2017.12.157ISI: 000426413400045Scopus ID: 2-s2.0-85040108589OAI: oai:DiVA.org:hh-38360DiVA, id: diva2:1263919
Available from: 2018-11-18 Created: 2018-11-18 Last updated: 2020-02-18Bibliographically approved
In thesis
1. Enhanced District Heating Technology: Maintaining Future System Feasibility
Open this publication in new window or tab >>Enhanced District Heating Technology: Maintaining Future System Feasibility
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

When heat demand and high temperature heat supply gradually decreases in the future, then it will effect district heating systems ability to compete on the heat market. A good way to mitigate less district heating feasibility is to operate systems with lower temperature levels and the most conceivable way to achieve lower temperature levels is to decrease return temperatures.

Thus, this thesis emphasise temperature errors embedded in district heating systems. Only a selection of temperature errors are analysed in this thesis. First, the temperature error that occurs due to recirculation in distribution networks at low heat demands. Second, the temperature error that occurs due to hot water circulation in multi-family buildings. Third, the temperature error that occurs due to less than possible heat transfer in heat exchangers, i.e. too short thermal lengths.

In order to address these temperature errors three technology changes have been proposed (i) three-pipe distribution network to separate the recirculation return flow from the delivery return flow, (ii) apartment substations to eliminate hot water circulation utilisation, and (iii) improved heat exchangers for lower return temperatures at a constant scenario. Analysis of proposed changes has resulted in annual average return temperatures between 17-21 °C.

Furthermore, rapid introduction of intermittent renewable electricity supply in the energy system has prompted an increased necessity of power system balancing capacities. Large-scale conversion of power-to-heat in electric boilers and heat pumps is a feasible alternative to achieve such balancing capacities. Analysis of the unique Swedish experience with utilisation of large heat pumps installations connected to district heating systems show that since the 1980s 1527 MW of heat power has been installed, about 80 % of the capacity was still in use by 2013. Thus, a cumulative value of over three decades of operation and maintenance exists within Swedish district heating systems.

The two papers presented in this thesis are related to future district heating systems through the five abilities of fourth generation district heating (4GDH), which are documented in the definition paper of 4GDH.

Place, publisher, year, edition, pages
Lund: Lund University Open Access, 2017. p. 75
National Category
Energy Engineering
Identifiers
urn:nbn:se:hh:diva-39199 (URN)978-91-7753-507-2 (ISBN)978-91-7753-508-9 (ISBN)
Presentation
2017-12-18, M:B (M-huset), Ole Römers väg 1, Lund, 13:15 (English)
Opponent
Supervisors
Note

Med populärvetenskaplig sammanfattning på svenska. I publikationen felaktigt: ISSN 0282-1990

Available from: 2019-04-04 Created: 2019-04-04 Last updated: 2019-04-04Bibliographically approved
2. Low-temperature District Heating: Various Aspects of Fourth-generation Systems
Open this publication in new window or tab >>Low-temperature District Heating: Various Aspects of Fourth-generation Systems
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

With decreasing heat demand and less availability of high-temperature heat supply in future energy systems, the current district heating systems may experience increased competition on the heat market. A viable option to mitigate increasing competition is to operate systems with lower temperature levels, and the most conceivable way to achieve lower temperature levels is to decrease return temperatures.In this thesis, aspects of improvements in district heating systems are assessed. Three aspects, in particular, have been analysed. These are integration between energy systems, improvements in heat distribution technology, and economic benefits of low-temperature district heating systems.An increasing interest in integrating different energy systems has been prompted by the rapid introduction of intermittent renewable electricity supply in the energy system. Large-scale conversion of power to heat in electric boilers and heat pumps is a feasible alternative to achieve the balancing capacities required to maintain system functioning. Analysis of the unique Swedish experience using large heat-pump installations connected to district heating systems shows that, since the 1980s, 1527 MW of heat power has been installed, and about 80% of the capacity was still in use in 2013. Thus, a cumulative value of over three decades of operation and maintenance exists within Swedish district heating systems.Increased competition prompted by changes in the operation environment necessitates improved heat distribution. This thesis focuses on three system-embedded temperature errors: first, the temperature error that occurs due to recirculation in distribution networks at low heat demands; second, the temperature error that occurs due to hot-water circulation in multi-family buildings; third, the temperature error that occurs due to lower heat transfer than is possible in heat exchangers (i.e. too-short thermal length). To address these temperature errors, three technology changes have been proposed (i) a three-pipe distribution network to separate the recirculation return flow from the delivery return flow, (ii) apartment substations to eliminate hot-water circulation use, and (iii) improved heat exchangers for lower return temperatures. The analysis of the proposed changes indicates annual average return temperatures between 17°C and 21°C.The final analysed aspect is the economic benefits of low-temperature district heating. It was identified that strong economic motives for lower operating temperatures in future heat supply exist, whereas the economic motives are significantly weaker for the traditional heat supply.The five papers presented in this thesis are related to future district heating systems through the five abilities of fourth-generation district heating (4GDH), which are documented in the definition paper on 4GDH.

Place, publisher, year, edition, pages
Lund: Lund University, 2019. p. 31
Keywords
District heating, low temperature, three-pipe systems, 4GDH-3P
National Category
Energy Engineering
Identifiers
urn:nbn:se:hh:diva-41080 (URN)978-91-7895-316-5 (ISBN)978-91-7895-317-2 (ISBN)
Public defence
2019-12-11, M:B, M-huset, Ole Römers väg 1, Lund, 13:15 (English)
Opponent
Supervisors
Note

ISRN: LUTMDN/TMHP-19/1153-SE. I publikationen felaktigt: ISSN 0282-1990

Available from: 2020-02-18 Created: 2019-12-03 Last updated: 2020-02-18

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