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District Heating and Cooling

Annex VII Project 06

The Research / IEA DHC Annexes / 2002-2005 / Annex VII / Annex VII Project 06

Dynamic Heat Storage Optimisation and Demand Side Management

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Description of the project

The pipeline system of a district heating system has a huge potential for the storage of energy. Especially for distributed systems like combined energy supply systems with renewable energies and CHP the optimal use of these storage capabilities increases the overall efficiency. Additionally, it enables the displacement of expensive peak power plants, to reduce electrical power peaks and to enable a better utilization of tariffs. With the application of sophisticated load management systems the complex dynamic interactions of combined energy systems can be considered and optimized with respect to improved heat storage processes and in the end with a higher efficiency of the system. While dynamic heat storage is a strategy regarding the energy supply and distribution, as a different approach demand side management (DSM) is a promising technique to increase the efficiency of energy supply systems focussing on energy peaks coming from the demand side.

This project will continue on the results of the project "Simple Models for Operational Optimization" which was carried out in Annex VI. This project compiled data from real DH-systems in Denmark, Finland and Germany which has been used to study the effects of the different simplification strategies on the accuracy of DH network models for simulation and optimization purposes. The application of these algorithms was very promising. As a continuation this project will focus on the application of the developed and tested simplification strategies in order to evaluate advantages of dynamic heat storage optimization techniques for DH systems and to compare heat storage possibilities to DSM approaches.

On the basis of real data, models with special consideration towards heat storage and the co-generation plants have been elaborated in Denmark, Finland and Germany. By the exchange of the different systems data it will be ensured that the strategies will be applicable in each country.

Summary of the final report of the project

In a partnership of the Department of Mechanical Engineering, Technical University of Denmark, the Finnish Research Institute VTT Processes and the German Fraunhofer Institute for Environmental, Safety und Energy Engineering UMSICHT within this project heat storage possibilities in the respective partner countries have been evaluated. For this purpose three different district heating systems in the participating IEA member countries have been regarded. On basis of different strategies to determine the possible impact of heat storage applications in district heating systems the economic and ecological effects for energy supply companies supplying heat and electricity can be estimated. Within this context especially heat storage applications with respect to the storage capacity of the pipeline system of the district heating network were regarded. Additionally, demand side management strategies based on a partial reduced supply of several customer substations in order to apply the building's volume and mass as a heat storage were in the centre of interest. These Dynamic Heat Storage (DHS) and Demand Side Management (DSM) strategies can be used as a supplement to steel tanks or other ways of heat accumulation.

After a comprehensive data collection phase the project group applied available strategies in order to determine the operational improvement by DHS and DSM strategies. The dynamic heat storage evaluations were based on simulation and optimisation models using simplified network models of the participating energy supply systems.

In the Danish Næstved system it has been shown how DHS could be used to store heat in the network if a failure in the CHP/waste incineration plant occurs. For the Parkvej subsystem in Næstved and the Finnish Jyväskylä DH-system it has been shown how DHS can be used to avoid the use of expensive fuel during the morning peaks. Within the German EVO system it has been evaluated whether the uncoupling of heat and power production in a CHP system could lead to financial and economic advantages. Model based optimisations on the Jyväskylä DH showed that DSM can further help not to use the expensive fuel at peak loads.

The project results can be summarised as follows:

  • For DH systems with electricity production (CHP), DHS can increase the possibility for electricity production, resulting in economic savings of up to 5 % per day determined in the Jyväskyla and EVO cases. For the entirely Finnish DH market savings can be estimated of about 3 billion US$ a year.
  • For DH systems without electricity production, the savings will be smaller, but DHS can be used to store heat made from the cheapest fuel source, for instance if a failure in the supply occurs as it has been simulated for the Næstved system.
  • DSM should be used to cut peak loads in order to shift from expensive to cheaper fuel. Possible savings of approximately 1-5% in Jyväskyla and Næstved have been determined. For the Finnish DH market due to DSM savings of about 6.5 billion US$ a year are possible.

Prepared by:
Fraunhofer Institut Umsicht , Germany


Fraunhofer Institut Umwelt-Sichterheit Energietechnik Umsicht



Technical University of Denmark, Denmark
VTT Energy Finland, Finland