Masoala Halle – Zoo Zurich
The Masoala Halle is an exhibit of the Zurich Zoological Garden. The Halle aims to recreate the environment of the Masoala Peninsula in the northern part of Madagascar, which is well-known for its unique, rich, and diverse fauna and flora. The Halle is a reproduction of the Masoala National Park with the main goals of informing and sensitizing visitors to the fragility of the environment it represents. The exhibit covers roughly 1 hectare (120m x 90m) with a maximum height of 30 meters. This artificial, tropical habitat houses approximately 300 individual animals including red ruffed lemurs, flying foxes, chameleons, geckos, and parrots.
The Masoala Halle is part of a nature conservation project funded by two main sources: private donations and a portion of the revenue from Zoo Zurich’s restaurants and shops. Zoo Zurich has committed to donating at least $125,000 (USD) each year, which is equivalent to approximately 25% of the annual budget of Masoala National Park. Zoo Zurich also promotes the reforestation of the region, sustainable agriculture and water supply, as well as the education of local children. This project was started in 1995, and has since raised more than 4 million Swiss Francs and counting.
The Halle contains 10 steel girders that support a foil roof constructed of inflated plastic (ETFE) cushions with a small overpressure inside.
This design has two main advantages:
- The plastic foil roof allows sunlight to pass through, thereby providing a necessary source of energy for the exhibit’s plants. Approximately 70% sunlight and 50% UV radiation passes through the air cushions of the roof.
- Air is an outstanding insulator due to its low heat conductivity; therefore, the air cushions minimize the heat loss from the roof which can be as low as 2 watts per square meter and Kelvin. However, the high humidity inside the hall and its resulting water condensation, would naturally lead to rapid algae growth on the inside of the roof, ultimately preventing the sunlight to pass through the roof. In order to prevent this outcome, the air cushions are dried via aeration with warm air.
The Halle is actively heated by a system of 40 geothermal probes and a thermal heat pump. The probes are buried 250 meters below the surface, where a constant temperature prevails. The heat is then conducted to the heat pump during the winter or brought back into the ground during the summer. During the winter, the geothermal heat (which is around 2-15 degrees Celsius) is brought to the heat pump, where it detracts heat out of the water and thus raises the temperature to around 40-45 degrees Celsius. During the summer, the ground probe is regenerated through warm air from the Masoala Halle.
If necessary, the main wood-chip-based heating system of the zoo supports the heat pump. The wood chips are from a local, sustainably sourced wood. Additionally, there is a heat recovery installation that extracts heat from the warm Masoala Halle air. This heat is then transferred to the water where it is used either to regenerate the ground probe or to preheat cool, outside air.
To maintain a tropical climate, the temperature inside the hall has to be kept above 18°C. Usually temperatures are between 18- 23°C in winter and up to 30°C (outside temperature + 2 Kelvin) in summer. To meet this requirement, the heating of the Halle consumes 1 gigawatt-hour of energy per year.
The Halle requires anywhere between 40 m3 of water per week and 140 m3 per day on a hot summer day. This large span is due to temperature fluctuations which cause variable evaporation. Considering the surface, this is equivalent to a consumption of approximately 3.6 liters/m2 per week or up to 12.7 liters/m2 per day.
Two water sources are used, both of which must be treated prior to entering the Halle. The first source is rain water collected from the roof. This water goes through several filtering and cleaning stages, namely ozonation, sand filtration, activated carbon filtration, and UV radiation. This water treatment is essential to prevent the import of local bacteria and microorganisms, which could harm the tropic fauna and flora of the Masoala Halle.
In the real Masoala Rainforest, there is roughly two times more precipitation than in Switzerland; therefore, an additional water source is necessary. This second source is the municipal drinking water of the City of Zurich. This already clean water must be softened and desalted before exhibit use. If this step is omitted, lime precipitate will settle on the exhibit’s plants.
Tour of the Masoala Halle organized by the Zoo Zurich, 19.12.18
Zoo Zürich AG
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