City Cooling - Intelligent district cooling implementation, Vienna
Initial situation and motivation
Compression chillers commonly used to cool down buildings are responsible for a high electricity demand. An alternative solution consists in using thermally driven absorption chillers which have significant energetic and ecological advantages, in particular when waste heat generated in thermal power plants is available and can be used to operate the chillers. These chillers can be installed and operated at every single building (decentralised cooling supply) or can supply several buildings through a district cooling network (centralised cooling supply).
The commercial building complex TownTown is being built at the underground station Erdberg in Vienna and is provided with district heating. Because of the housing density and the high cooling demand a district cooling grid network is built in parallel with the district heating network. However, in order to be considered as a sustainable cooling concept, district cooling has to comply with particular requirements which are analysed at the example of this first district cooling network in Vienna. The characteristic features of an intelligent district cooling supply are summarised here in a structured way.
Contents and objectives
In a first step the cooling technologies of modern office buildings and the required technical framework for a district cooling application are collected. A methodical procedure is then developed and applied as a basis of a strategy to design an intelligent district cooling application. The design and operation characteristics of cooling towers play a major role in the assessment of the energy and ecological performance of district cooling. Therefore the different possibilities of reducing the amount of rejected energy in cooling towers are analysed here. The possibilities of optimising the building mix, the use of thermally activated construction elements (TABS) and storage units, the use of rejected heat as well as the economic optimisation of the network design and operation are analysed on the example of TownTown and are evaluated under technical, economical and ecological aspects.
The targets of the project are:
- Definition of an intelligent district cooling application considering alternative heat rejection concepts for the design of energy efficient district cooling network at the example of TownTown.
- Definition of flexible district cooling applications for different comfort levels, cooling systems and cooling use.
- Replicability of the developed district cooling applications and the concepts for alternative heat rejection in future district cooling networks in Austria.
Because of the broad field of analysis, the report is based on a comprehensive literature research. For all aspects which are analysed in other studies, the main results are summarised here and the reference to the relevant work is given. The project specific contributions have been developed by using the following modelling and simulation software:
- Calculation of cooling demand profiles using transient building and system simulation [TRNSYS]
- Evaluation of the effect of variation of different design parameters of a district cooling network using thermodynamic plant simulation [DYMOLA]
- Optimisation of district cooling network operation to reduce the operation costs with DEMS [DEMS]
The results are structured around a methodological procedure which is recommended for the design of a district cooling concept.
Indexes are proposed to be used in specific approaches to design cooling systems in combination with district cooling and different operational strategies for the TABS are evaluated under comfort aspects, cooling energy use and cooling energy load profiles. The economic feasibility of different grid design scenarios and operational strategies of the district cooling are assessed.
In parallel, concepts and methods are elaborated and proposed for different issues. In particular the comparability between TABS and conventional air cooling units is being analysed and possible concepts for using heat rejected from chillers are proposed.
DI Olivier Pol
Ing. Anita Preisler
DI (FH) Gernot Haslinger
Project or cooperation partner
- DI Hans-Joachim Kast
ILF beratende Ingenieure
- DI Adolf Penthor
Ing. Gerhard Kempel