Smart low-carbon district heating networks supporting the energy system transition

Mikko Wahlroos

Research output: ThesisDoctoral ThesisCollection of Articles


Heating and cooling sector represents approximately 50% of the total energy consumption in the EU. The European Commission has begun to put more emphasis on the heating and cooling sector by publishing the EU strategy on heating and cooling. District heating (DH) is one of the most efficient heating solutions, especially in the colder regions with high population density. The amount of DH based heat production has remained on a rather stable level during the past decade. Furthermore, DH has been mainly produced with fossil fuels nowadays, and in order to tackle the emissions of heat production, current DH systems are facing a transition towards cleaner and more cost-efficient production. This dissertation investigates increasing smartness in DH networks and assesses the introduction of new heat sources to DH networks. In this context, smart DH networks stand for cost-efficient, low-carbon networks that allow prosumers to gain market access to sell their heat to DH networks. This dissertation models increasing the amount of additional heat supply by heat pumps (HPs), solar thermal production, and data center (DC) waste heat in existing DH networks in Finland. Furthermore, the potential for low-temperature DH networks and dynamic pricing of DH production is studied, as well as the future for biomass based combined heat and power (CHP) production in the EU-27. The results of this thesis indicate that increasing the amount low-carbon DH production technologies decreases utilization of existing units, mainly CHP based heat production and heat-only boilers. Decreasing operational hours of CHP units may decrease the profitability of these units, and the future of CHP is at risk. The current investment environment in the EU does not suggest that biomass CHP would contribute significantly to overall energy efficiency. The results suggest that HPs and DC waste heat would be a suitable alternative for low-carbon DH production, and they could supply heat with high operational hours. DCs can supply heat on a stable level but there are still many barriers slowing down DC waste heat utilization, mainly related to business models between different parties. However, if alternative heat production capacity is not owned by the DH companies, the pricing structure of district heat production should be assessed. Pricing for third-party heat should be transparent so that the utilities can easily assess whether the investment is profitable. Solar thermal production is not feasible for a large-scale DH network in Finland with the current price level, but they could benefit from lower distribution temperatures. Additionally, lower distribution temperatures would increase profitability of HPs and potential for additional low-temperature waste heat supply.
Translated title of the contributionÄlykkäät vähähiiliset kaukolämpöverkot tukemassa energiasysteemien murrosta
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Syri, Sanna, Supervising Professor
  • Syri, Sanna, Thesis Advisor
Print ISBNs978-952-60-8495-4
Electronic ISBNs978-952-60-8496-1
Publication statusPublished - 2019
MoE publication typeG5 Doctoral dissertation (article)


  • district heating
  • heat production
  • energy efficiency
  • data center
  • heat pumps
  • combined heat and power production
  • flexibility
  • two-way heat markets


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