While the demand for heating is decreasing due to climate change, the cooling of buildings is becoming massively more important, especially in densely built-up inner cities. "Thermal networks and cooling" was therefore also a focus topic of the 22nd IGE seminar of the Institute of Building Technology and Energy at Lucerne University of Applied Sciences and Arts.
As a result of climate change, densely built-up inner cities in particular are affected by increasingly intense summer heatwaves. An efficient and environmentally friendly alternative to decentralized air conditioning systems are thermal networks that supply cold water via pipe systems to cool buildings such as office complexes, hospitals or data centers. They usually use a lake or river as a "cooling source". In winter, the network can be used for district heating.
Andreas Hurni, Managing Director of Swiss Thermal Grids, highlighted the importance of thermal grids for the energy transition. In terms of cooling supply, he recommended "getting big instead of getting small", as the demand for cooling is likely to increase massively by 2050, as well as using synergies with the parallel expansion of district heating in order to improve cost-effectiveness and energy efficiency.
Cooling supply in Zug, Zurich and Vienna
Thermal networks for the supply of heating and cooling are already a reality in many cities or are under construction or in planning. Three speakers provided insights into projects in Zug, Zurich and Vienna. Circulago, which supplies large parts of the city of Zug with environmentally friendly heating and cooling energy, is already in operation. Adrian Steiner, WWZ Energie AG, presented the most important findings from five years of operating experience. He emphasized that cooling planning is much more complicated than heating planning, because while heat output and heating degree days correlate very well, this is not the case with cooling output and cooling degree days.Burkhard Hölzl, Wien Energie GmbH, was also able to draw on many years of experience. One of the largest district cooling networks in Europe is in operation in Vienna and is being continuously expanded. The network runs in a ring around the old town and uses water from the Danube. Hölzl explained that district cooling is also suitable for listed buildings, which is relevant for Vienna with its large stock of such buildings. CoolCity Zurich is still in the planning or early construction phase and will cover the heating and cooling requirements of numerous office buildings and service areas with renewable energy from Lake Zurich from 2032. Pascal Leumann, ewz Energy Solutions, presented the generation project in Switzerland’s largest city, which will cost over 300 million. The plans include seven tunnels, one of which has already been realized.
Planning with the microclimate
Veronika Sutter from Zurich’s Department of Buildings explained how else the city of Zurich is tackling the heat, with reference to the approximately 12,000 m2 Koch Park, which contributes to heat reduction in the city with large trees, sophisticated rainwater management with seepage vessels, large areas of unsealed surfaces, light-colored paving and a pioneer forest. With QKM, an add-in for the BIM software Revit, Markus Koschenz, Lucerne University of Applied Sciences and Arts, presented a new tool for district climate simulation. It can be used to quantify the effect of urban development on the microclimate based on parameters such as radiation, shade, water balance, etc. The calculation is much faster than with conventional tools. Koschenz also drew attention to the CAS Urban Climate offered by Lucerne University of Applied Sciences and Arts.Research projects from the Lucerne University of Applied Sciences and Arts
Michael Bayer, Lucerne University of Applied Sciences and Arts, is researching seasonal thermal energy storage. He spoke about the advantages of heat storage systems in cascaded operation for heating and cooling networks: flexible temperature levels, adaptable storage capacity and flexibility with changing load profiles. Timotheus Zehnder, Lucerne University of Applied Sciences and Arts, showed how firewood can be used more efficiently thanks to flue gas cooling and condensation in wood firing systems. A solution with an absorption heat pump proved to be ideal.Cooling strategies for people
At the end of the event, Dr. Dieter Kissling, ifa Institute for Occupational Medicine, showed how heat affects the human body. He also spoke about the ideal room temperature. What is considered a comfortable temperature in offices depends on gender: According to a formula from the 1960s, for example, most rooms are cooled down to meet the needs of men (21-22 degrees), while women tend to freeze at these temperatures due to their physiology. At higher temperatures (26-27 degrees), women become significantly more productive. From an economic point of view and with an increasing proportion of women in offices, we should therefore discuss whether warmer offices would not make more sense.The broad range of topics makes it clear: climate change, more intense periods of heat and the associated challenges are occupying many disciplines. Solutions are being worked on, but there is still a lot to do.
