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Daily heat load variations in Swedish district heating systems
Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS), Energiteknik.
Halmstad University, School of Business, Engineering and Science, Biological and Environmental Systems (BLESS).ORCID iD: 0000-0001-9069-0807
2013 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 106, 47-55 p.Article in journal (Refereed) Published
Abstract [en]

Heat load variations in district heating systems are both seasonal and daily. Seasonal variations have mainly its origin from variations in outdoor temperature over the year. The origin of daily variations is mainly induced by social patterns due to customer social behaviours. Heat load variations cause increased costs because of increased peak heat load capacity and expensive peak fuels. Seasonal heat load variations are well-documented and analysed, but analyses of daily heat load variations are scarce. Published analyses are either case studies or models that try to predict daily heat load variations. There is a dearth of suitable assessment methods for more general analyses of existing daily load variations. In this paper, a novel assessment method for describing daily variations is presented. It is applied on district heating systems, but the method is generic and can be applied on every kind of activity where daily variations occur. The method was developed from two basic conditions: independent of system size and no use of external parameters other than of the time series analysed. The method consists of three parameters: the annual relative daily variation that is a benchmarking parameter between systems, the relative daily variation that describes the expected heat storage size to eliminate daily variations, and the relative hourly variation that describes the loading and unloading capacity to and from the heat storage. The assessment method could be used either for design purposes or for evaluation of existing storage. The method has been applied on 20 Swedish district heating systems ranging from small to large systems. The three parameters have been estimated for time series of hourly average heat loads for calendar years. The results show that the hourly heat load additions beyond the daily averages, vary between 3% and 6% of the annual volume of heat supplied to the network. Hereby, the daily variations are smaller than the seasonal variations, since the daily heat load additions, beyond the annual average heat load, are between 17% and 28% of the annual volume of heat supplied to the network. The size of short term heat storage to eliminate the daily heat load variations has been estimated to a heat volume corresponding to about 17% of the average daily heat supplied into the network. This conclusion can also be expressed as an average demand of 2.5 m3 of heat storage volume per TJ of heat supplied by assuming a water temperature difference of 40 C. The capacity for loading and unloading the storage should be equal to about half of the annual average heat load for heat supplied into the network. © 2013 Elsevier Ltd.

Place, publisher, year, edition, pages
Oxford: Pergamon Press, 2013. Vol. 106, 47-55 p.
Keyword [en]
District heating, daily heat load variations, heat storage, seasonal heat load variation, novel method
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:hh:diva-22166DOI: 10.1016/j.apenergy.2013.01.030ISI: 000317544400005Scopus ID: 2-s2.0-84873677803OAI: oai:DiVA.org:hh-22166DiVA: diva2:621791
Note

Funding: Fjärrsyn, the Swedish district heating research programme, and Öresundskraft

Available from: 2013-05-17 Created: 2013-05-17 Last updated: 2017-04-03Bibliographically approved

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CiteExportLink to record
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Cite
Citation style
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