With the Expo2020 the Baden-Württemberg Pavilion opened in October 2021. Transsolar faced the challenge of creating outdoor comfort in a shaded location adapted to the local climate with the lowest possible energy demand for operation, especially for air conditioning. Also, the energy needed to produce the materials, the embodied energy, had to be as low as possible and materials had to be chosen with reusability in mind. Therefore, large parts of the structure and the facade cladding were made of wood from Baden-Württemberg.
The climate of Dubai is subtropical and hot. The sun shines almost every day and the daytime temperatures during opening times of the EXPO in autumn and spring – October to the end of March – are up to 40°C (104°F). At night it gets much cooler, around 30°C (86°F), but with very high humidity.
The curved glass and wood façade that dominates the pavilion's appearance was created in close collaboration between structural and façade planners Knippers Helbig and Transsolar to coordinate requirements for transparency and protection from morning sun. 500 square meters of roof-integrated PVT modules – hybrid thermal photovoltaic modules – form a rear-ventilated shading layer above the pavilion. They simultaneously cover the electrical energy demand for CO2-neutral conditioning of the entire pavilion and collect heat with the heat exchanger on the backside. This system heats the PV surfaces in the early morning hours preventing dew with dust particles settling on the modules, which would be burned in by the sun. The dust remains dry and is blown away by the wind or removed by a cleaning robot. A reduction in efficiency due to soiling is therefore significantly smaller; cleaning with valuable water is no longer necessary.
The heart of the comfort concept is a "CoolPool". It features design that reflects local site conditions by interacting with the environment and taking advantage of the dynamics of outdoor climatic conditions, not as a technical add-on, but integrated as part of the design itself. It reflects a natural phenomenon where cold, dry air accumulates and persists in desert sand pits and drops. As a cold lake with cloud formation, this phenomenon can also be witnessed in the valleys of the Black Forest. For the “CoolPool” to work in the pavilion, an inner courtyard has been created ,shaded by the floating exhibition box, which encloses a volume of air that is only open at the top and which is cooled during the day by a thermal storage unit under the building.
The PVT system on the roof regenerates this foundation heat exchanger at night with its thermal system. The heat absorbed in the “CoolPool” during the day is released to the night sky . Thus, the ground sink remains cool, with temperatures of 4 to 10 Kelvin far below those of the surroundings and offers Expo visitors a well-tempered shaded area as a resting zone - emission-free and energetically at zero cost.
Our system implementation and evaluation on site show that the "CoolPool" does its job: The surface temperatures were measured by using an infrared camera and the function confirmed; "Feel the Spirit of Innovation", the slogan of the Baden-Württemberg House, is literally possible.