UKÖ

UKÖ - Urbaner Kältebedarf Österreich

There is a significant increase in demand for building cooling - both worldwide and in Austria. It is driven by a combination of increasing prosperity, urbanisation, demographic developments and, last but not least, climate change. Against this background, the UKÖ project aims to

1. quantify and visualise the future cooling requirements of buildings in Austria,
2. support decision-makers in the development of climate protection measures and climate change adaptation strategies and
3. provide energy suppliers as well as technology and component manufacturers with an estimate of future cooling requirements.

To this end, Austria's building stock is categorised according to certain characteristics (year of construction, renovation status, window area and quality, etc.) in order to then calculate the cooling demand for different scenarios up to 2050 using dynamic building simulation software (IDA ICE). The results are combined with data on living space at municipal level (Statistics Austria) and thus visualised spatially.

In addition to the resulting cooling demand maps, the project provides a ‘cooling demand matrix’ (calculation aid for estimating the cooling demand based on a few building characteristics) and a catalogue of technology profiles for cooling buildings.

The main factors that determine the cooling demand are the outdoor climate, building quality and building utilisation. The relevant measure of the outdoor climate for cooling demand is the number of cooling degree days at a location. It can be assumed that the average number of cooling degree days in Austria will increase by 50 % to almost 100 % by 2050. In addition to the outdoor climate, the quality of the building proves to be a determining factor for cooling requirements. Above all, the quality of the windows and solar shading. Downstream, but still relevant, are the qualities of thermal insulation and ventilation. The last set of formation factors results from building utilisation, i.e. internal heat loads from people or appliances.

The national cooling demand scenarios forecast a diverse picture of cooling demand. Depending on the study, the cooling demand for the year 2050 varies between 3 TWh and 19 TWh. One exception is the study by Kranzl et al. (2011), which agrees with the findings of Persson and Werner (2015). In contrast to international cooling demand scenarios of climatically and culturally similar nations, including Germany and Belgium, the development of future cooling demand is comparable with Austria. Significant deviations result from the applied limit temperature for determining the cooling degree days, the area specification and - in individual cases - the consideration of area and population development with a moderate or dynamic approach.

A cooling matrix was developed as an Excel document based on the factors influencing the cooling requirement. It takes into account comfort level (general or adaptive), type of use (residential or office), construction period (before 1945, 1945-1990 or after 1990) and building condition (existing or refurbished). It also serves as a basic document for the geographical localisation of cooling demand and output in Austria. The cooling demand maps according to the general comfort model show an absolute cooling demand of 3.5 to 6.3 TWh/a for the year 2050, depending on the scenario. The cooling demand in 2050 is significantly high in Vienna and its surroundings, in Burgenland and along the Danube valley, compared to other municipalities. A similar picture emerges for the cooling capacity in the same year. The number of cooling degree days, the size of the area to be cooled, the utilisation of the building and the condition of the building are particularly significant influencing factors.

The technology analysis and assessment shows that some of the technologies analysed are considered to be of little relevance because their local cooling potential is not sufficiently known or is too low. Other reasons include their low availability, comparatively high costs or the fact that sensible use is only possible under certain conditions. In terms of sustainability, passive cooling measures or measures to improve comfort should always be considered first. Shading, natural ventilation cooling and comfort improvement beyond physical heat extraction should be particularly emphasised here. The use of cooling envelope materials and solar control glazing must be considered on an individual basis. Active cooling measures should only be utilised once these and other passive options have been exhausted.

As part of a feasibility study, passive and active cooling measures are taken for five representative urban neighbourhoods. Shading and solar control glazing were taken into account in all studies. Cooling envelope materials and ventilated façades were not proposed in the studies as they represent a high cost factor. In addition to the passive measures, the following system variants for active temperature control were proposed for the urban neighbourhoods under consideration:

1. Compression chiller with recooling to groundwater
2. Compression chiller with recooling into the public anergy grid
3. District cooling or compression chiller with recooling to geothermal probes and outside air
4. Heat pump/compression chiller with recooling to geothermal probes
5. Compression chiller with recooling in the district heating return flow

The project was funded by the Austrian Research Promotion Agency (FFG) and the Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology via the call Stadt der Zukunft, 9. Ausschreibung 2022 and carried out together with the Institute for Spatial Planning, Environmental Planning and Land Use Planning at BOKU, the Institute of Building Research & Innovation and VASKO+PARTNER INGENIEURE Ziviltechniker für Bauwesen und Verfahrenstechnik GesmbH.

Project status: completed