Urban cooling demand in Austria 2030/2050 (UKÖ 2030/2050)

Motivation

The demand for building cooling is significantly increasing - worldwide and in Austria. It is caused by the increase of prosperity, urbanisation, demographic developments and climate change.
Meanwhile, the current scientific knowledge is insufficient to derive precise conclusions for policy and administration or to initiate technological innovations.

Project contents and objectives

Based on the background, the aim of this study is to quantify and present the future cooling demand of buildings and neighbourhoods in Austria, to support decision-makers in the development of climate protection measures and climate change adaptation strategies and to provide energy suppliers and technology manufactures with an estimate of future cooling demand.

Methodical procedure

The study is structured as follows:

1. The formation factors of the increasing cooling demand are systematically analysed.
2. Existing cooling demand scenarios are analysed and evaluated comparatively.
3. Cooling demand matrix is designed to illustrate future cooling demand depended on climate location, future climate scenario, building structure and comfort requirements. Numerical values of the cooling demand are determined using dynamic thermal building simulation.
4. The contents of this cooling demand matrix are geographically localised and clearly illustrated in cooling demand maps.
5. A structured techno-economic technology analysis is performed.
6. The collected findings are applied to five urban neighbourhoods as examples in a feasibility study.

Results

The main cooling demand factors 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 must be assumed that the average number of cooling degree days in Austria will increase by 50 % to almost 10 0% by 2050.

In addition to the outdoor climate, the quality of the building proves to be a determining factor for the cooling demand with particular emphasis on the quality of the fenestration and solar shading. Downstream but still relevant are the qualities of thermal insulation and ventilation. The final set of 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 2050 varies between 3 TWh and 19 TWh. One exception is the study by Kranzl et al. (2011), which is justifiable with the findings from 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 cooling demand formation factors determined. It considers 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 for the year 2050, depending on the scenario. The cooling demand in 2050 is significantly higher in Vienna and its surroundings, Burgenland and along the Danube valley compared to other regions. A similar picture emerges for the cooling capacity in the same year. Particularly significant influencing factors are 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.

The technology analysis and assessment reveal 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 limitations are their low availability, comparatively high costs or the fact that they can only be used sensibly 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 were evaluated for the five urban neighbourhoods. Shading and solar control glazing were considered in all studies. Cooling envelope materials and ventilated façades were not proposed in the studies, as they either represent a high-cost factor. In addition to the passive measures, the following system variants for active temperature control are proposed for the urban neighbourhoods under consideration:

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

Project management

Institute of Building Research & Innovation ZT GmbH

Project or cooperation partners

• Vasko + Partner ZT-GmbH
• BOKU Institute for Process and Energy Engineering (IVET)
• BOKU Institute for Spatial Planning, Environmental Planning and Land Use Planning (IRUB)

Felix Wimmer, BSc.
Wipplingerstraße 23/3
A-1010 Wien
Tel: + 43 (1) 581 13 19 812
E-mail: felix.wimmer@building-research.at
Web: www.building-research.at