At the IET Institute of Energy Technology, experts in simulation technology, measurement technology, building services engineering and other specialist areas are working on current challenges: Room ventilation, UV decontamination and thermal management.

The impulse program "Innovative Power Switzerland" promotes innovative product developments. At the IET, the focus is on holistic and interdisciplinary research questions.

With the Corona Summer 2020, room ventilation is suddenly in vogue. Mass media reported on the efficient filtering performance of ventilation in airplanes and hotels. Fogging experiments were conducted in concert halls and theaters to assess whether a critical concentration of aerosols might form or where exhaled air might presumably pass through. Such experiments and field tests are important to perform, but visualizing the air currents involves a great deal of effort. Here, however, only one aspect is illuminated: with the winter, questions about heat management in buildings are added. After all, if the windows are open all the time, you can literally let money flow out.

Human well-being in a room depends on many factors. Individual sensations meet physically precisely measurable variables such as temperature, humidity and airflow velocity. Is it pleasantly warm? Is there a draught? Is the air thick? Every person feels differently. Finding an individually appropriate assessment of the indoor climate seems almost impossible.

Hand in hand

Modern scientific knowledge is based on three pillars: classical experiments, theoretical correlations, and virtual experiments (computer simulations). Flow simulations performed on powerful computers are often associated only with the automotive and aircraft industries or racing. However, they are a proven tool that can be adapted to specific circumstances. In many places they also serve as a favorable supplement and alternative. At the IET Institute of Energy Technology, simulations are used in teamwork by experts in building technology, measurement technology, and simulation technology to jointly master current challenges of the economy and society.

Indoor climate simulations are more established than the current hype might suggest. Back in 2014, we conducted comparisons between simulations and experiments on climate ceilings together with Barcol-Air as an industry partner. Barcol-Air operates an elaborately equipped measurement laboratory with a large number of sensors and heating sources ("standard humans"), which is intended to simulate various aspects of an office workspace. One measurement difficulty lies in the nature of things: the measurement laboratory must first be "calibrated" with the surrounding building.

The measurement laboratory first has to be "calibrated" with the surrounding building in order to reproduce the typical temperature cycle of a normal working day. This settling can take several days and leads to high costs until the actual measurement series can finally start.

What is shown in the video? The air rises above the heating sources ("norm people") and at the cold window pane it sinks. The color of the ceiling elements indicates warm or cold areas: in the cold area the air cools down and sinks to the ground. All in all, complex structures of the air flow are created, which are made visible by means of arrows. In the second part of the video you can see a second, identical arrangement, but without tempered ceiling elements. Comparing the two rooms, you can clearly see that the airflow is faster. This can be perceived as a draft in some circumstances. Conclusion: the tempered ceiling elements can specifically influence the air flow and contribute to a more pleasant stay.
Was ist im Video dargestellt? Die Luft steigt über den Heizquellen ("Norm-Menschen") auf und bei der kalten Fensterscheibe sinkt sie ab. Die Farbe der Deckenelemente zeigt warme bzw. kalte Bereiche an: im kalten Bereich kühlt sich die Luft ab und sinkt zu Boden. Insgesamt entstehen komplexe Strukturen der Luftströmung, die mittels Pfeilen sichtbar gemacht sind. Im zweiten Teil des Videos sehen Sie eine zweite, identische Anordnung, jedoch ohne temperierte Deckenelemente. Im Vergleich der beiden Räume sieht man deutlich, dass die Luftströmung schneller ist. Dies kann unter Umständen als Zugluft empfunden werden. Fazit: die temperierten Deckenelemente können die Luftströmung gezielt beeinflussen und zu einem angenehmeren Aufenthalt beitragen

Virtual becomes reality

Therefore, the initial situation was simulated identically on the computer. Some processes and materials were unknown and were simulated with simplified models. The comparison between experiment and simulation showed good agreements. Overall, the simulations were so convincing that they were presented at the Swissbau Basel trade fair together with a mobile measuring stand. Visitors could view the simulations with 3D glasses and compare details directly with the fog clouds at the measuring stand. For Barcol-Air, however, another aspect was in the foreground: the computer simulations made it possible to assess various arrangements in the sample room within a few days and to design their products accordingly.

Reducing energy and disinfection costs with UV rays?

In classical window ventilation - in a simplified view - warm exhaust air is replaced by cold fresh air. This in turn has to be heated up, which leads to higher heating and operating costs. Room ventilation with a built-in heat exchanger makes it possible to reduce the additional costs. We have measured the effect of air exchange in VBZ streetcars and buses under real conditions and incorporated it into a holistic approach that takes total costs into account.

We are also working on the decontamination of drinking water using ultraviolet (UV) LEDs. This emerging technology can equally be used to sterilize surfaces, food, and especially air. This raises exciting research questions: how efficiently can fresh as well as indoor air be disinfected with UV light? How expensive is UV technology in this field of application? Could it be used to efficiently increase occupational hygiene?

Promotion of innovative products

Innosuisse is the Swiss agency for innovation promotion. It provides SMEs with easy access to knowledge and resources of research institutions, taking into account the protection of intellectual property. Innosuisse's services include small innovation checks as well as the promotion of multi-year development cycles of novel products. The Federal Council approved an additional CHF 63 million for project funding with the impulse program "Innovation Power Switzerland". Do you have an innovative idea that would complement your product range? We will be happy to advise you!