General Role: coordination support, dynamic system simulations and final report writing.
Specific technologies in charge of: dynamic system simulations of DH systems in combination with ice storages using pytrnsys.
Main goal of the project: The overall goal of this project was to quantify the potential and the effects of ice storage tanks used within 5GDHC networks. Ice storage tanks are expected to be a benefit in 5 GDHC with limited heat sources. Different combinations of heat sources were analyzed using detailed dynamic system simulations with TRNSYS. Heat sources studied were waste heat of sewage plants and a generalised constant source (for example from data center cooling), air heat exchangers and solar thermal collectors. Different control and integration strategies have been tested and the most important factors influencing the performance of thermal networks with ice storage tanks have been identified.
Extended Summary: According to the Energy Strategy 2050+, the share of district heating (DH) in Switzerland’s heat supply is set to rise sharply to around 30 %. An increasingly popular type of DH networks is the so-called anergy network, which distributes energy to decentralised heat pumps installed in buildings from a low temperature source. Many of the low temperature sources available in Switzerland are either limited in their power output (e.g. waste heat from sewage treatment plants), or are only available to a limited extent on cold winter days, if at all (e.g. solar thermal energy). In this project we investigated the potential of integrating ice storages into low temperature heating networks in order to bridge such performance bottlenecks and/or gaps. Due to the high amount of energy released (or absorbed) during the phase transition, ice storage systems are suitable for storing large amounts of energy at temperatures near 0 ºC. For this reason, more and larger ice storage systems are being used as an energy source for heat pumps in Switzerland. As an example district our investigations use the Jona energy network, which distributes the waste heat from a waste after treatment plant to decentralised heat pumps and thus makes it usable. Ice storage tanks can be easily and directly integrated into antifreeze bearing networks such as this example network. However, freezing of the heat exchanger on the sewage treatment plant side must be prevented by a partial re-circulation from the flow pipe. Based on the results in this study, the following findings emerge:
1) In combination with power limited waste heat sources, even small ice storage volumes are sufficient to bridge power peaks in winter.
2) As a lot of surplus waste heat is readily available for regenerating ice storage systems during the transition period, ice storage systems can at least double the capacity of such sources.
3) When combining ice storage tanks with scalable seasonal heat sources (e.g.outdoor air or solarthermal energy), ice storage sizes of approx. 0.6 m3/MWh are required to enable year-round operation of the network at 0 ºC.
Duration: 2022-2024
Web: https://www.aramis.admin.ch/Grunddaten/?ProjectID=49264
Subcontracted by: Insitute for Solar Technology (SPF)
Funding Agency: Swiss Federal Office Of Energy (SFOE)
