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District Heating and Cooling

Annex XIII Project 04

The Research / IEA DHC Annexes / 2020-2023 / Annex XIII / Annex XIII Project 04

BeyondSubstation - Cost Benefit study on the building secondary network for improving DH performance

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Project summary

Most of District Heating (DH) systems have been connected to existing buildings with their own heating distribution system which is generally not optimised for reducing return temperatures. Hence, 60% of malfunctions stem from the secondary heating system (building’s internal heating system), 30% stem from District Hot Water systems and the last 10% are coming from a failure of a substation component (IEA DHC ANNEX VII, 2005).

Thus, there is a strong potential for improving the performance of existing and new DH but which is often difficult to seize since the district network operator is often different from the building operators. The project goal is to contribute to increase the share of renewables and to ease the utilization of low temperature heat sources in District Heating networks by decreasing the return water temperatures on the network.

To move towards lower carbon footprint DH, a key issue to be solved is the low performance of second heating systems. The project objective is to bring out some recommendations to improve the design and the operation of second heating systems in order to lower the return water temperatures and to identify heat tariffs models in order to foster building owners to improve the building-side hydronic systems.

The specific objectives of the project are to better identify the defaults, to set the best controls in the substations, to propose some cost-effective changes in the secondary systems in case of building retrofit and to give insights to practitioners when designing architectures original DH configurations for new or retrofitted buildings. To reach these objectives, the project team will assess the impact of secondary heating-network architectures (space heating and domestic hot water) and controls on the DH in order to identify cost-effective solutions to lower return water temperatures.

The projects methodology will be based on a simulation approach consolidated with on-site data analysis. Indeed, the project team pioneered new simulation tools to allow model district heating systems including secondary networks with all their complexities and constraints.

In this work, project’s simulation approach will be enhanced to achieve large parametric studies and optimisation in order to identify the best solutions and to assess their energy gains. As a result of this work, future business models with incentive tariffs will be built to encourage the building owners to reduce water return temperatures. The project team will identify what is known on motivational tariffs and how to design them efficiently in way that the reduction of incomes for DH companies caused by incentive tariffs are compensated by improved performance.

Taget groups

  • District Heating Network Operators
  • Building operators

Deliverables / Outcomes

  • Assessement of the economic benefits of different energy efficiency actions on existing DH 

  • Development of more efficient DH systems by lowering the return water temperatures

  • Identification of indicators to help in identifying malfunctions in customer stations and proposals for corrections of these faults.

  • Creation of easily understandable incentives to help the customer in his decision-making process. 

Project lead

ARMINES-Mines ParisTech, CES, Center for Energy Efficiency of Systems
60 bd Saint Michel
75006 Paris

Prof. Pascal Stabat
Phone: 00 33 1 40 51 91 52
E-Mail: pascal.stabat@mines-paristech.fr 

Project partners

  • ENGIE Lab CRIGEN, France
  • IVL The Swedish Environment Research Institute, Sweden