Heat from a depth of 100 metres

7 min read

mit Thomas Herrmann
Nowadays, it is a matter of course to use energy- efficient construction methods. What special challenges does a huge structure like the Humboldt Forum present?

Thomas Hermann: When dealing with a building of this size and form of usage, you need to tackle sustainability from an entirely different angle than when you’re looking at a single-family home. For example, cooling will be a key issue for the Humboldt Forum all year round – especially during opening hours, when heat and humidity are emitted by the lights and by the crowds of visitors. Just to give you an idea of the dimensions we’re talking about: The output of heating and cooling we’ll need for the Humboldt Forum would suffice for 1,500 to 2,000 single-family homes! This despite the fact that the building, thanks to its wellinsulated windows and walls, will be 30% more energy-efficient than the target levels imposed by the Energieeinsparverordnung (EnEV, Energy Savings Ordinance) of 2009.

Aside from size, what are some of the other special aspects?

Our sustainability strategy is like a mosaic consisting of many individual pieces, each of which addresses a specific point of the strategy’s technical agenda. For example, we have to provide a certain interior climate for the objects and artworks of the Ethnological Museum and Asian Art Museum and for the on-loan items displayed in the special exhibition areas. If organic materials are involved, for example, the temperature and humidity must be kept as constant as possible. We will therefore use a “multi-phase thermodynamic treatment process” to dehumidify and cool down the entire exhibition space in the summer and to humidify and heat it in the winter. This type of process consumes a lot of energy. So we’ve given a lot of thought to how we can use this energy as efficiently as possible while also generating it ourselves.

We will be using heat energy from the earth. We are drilling 100-metre-deep holes into which a total of 111 tubes will be inserted.
So the Humboldt Forum will actually generate energy?

Yes, with the aid of geothermal energy; in other words, we will be using heat energy from the earth. We are drilling 100-metre-deep holes into which a total of 111 tubes will be inserted. These are U-shaped pipes in which water circulates. At such depths, you have more or less consistent temperatures of 12 °C. During the summer, we will convey the heat out of the building, through the tubes and down into the earth, where we’ll store it; during the winter, we’ll bring it back to the surface and use it to heat the building.

You were saying that cooling will play a special role at the Humboldt Forum. That’s an energyintensive process. How will you keep a lid on consumption?

In order to exploit the cooling energy as efficiently as possible, we’ve divided our cooling networks into two sections: The first one will be used for dehumidification and cooling, the second one for cooling only. The exhibition areas will have to be constantly cooled and dehumidified. And these areas make up about half of the more than 40,000 square metres of total floor space. In other areas, such as the computer server rooms, cooling alone will suffice. What’s more, not all areas of the building will be air-conditioned; large parts of it will simply be ventilated and heated. Taken together, these measures will allow us to conserve lots of energy.

And what about the issue of ventilation?

Here, we intend to fall back on an old method which is unfortunately falling into disuse these days: We will recycle a portion of the exhaust air as inlet air. At night, when all the lights are off and the visitors are gone, the air will be simply recirculated, without any fresh air being supplied. During the day, when the spaces are again thronged with visitors, we will then go back to drawing fresh air from the outside; after treating and warming it, we will convey it into the building’s interior. A CO2 sensor will automatically measure the air’s composition and will regulate the intake process.

Why is it you don’t supplement the geothermal ground heat with other renewable energies, such as solar energy?

Well, for one thing we chose not to put solar cells on the roof for aesthetic reasons. But there are technical factors to consider as well: The Humboldt Forum has an electric power requirement of roughly 4,000 kilowatts. Based on an optimistic calculation, solar energy could contribute 200 kilowatts. Since our energy supply has to be assured at all times, this forces us to procure a guaranteed volume of power each month. The relatively small subvolume derived from solar power, which, moreover, may vary depending on the weather, would not change this situation.

What else will make the Humboldt Forum environmentally sustainable?

A key consideration, particularly for the city’s centre near the Spree River, is how to deal with rainwater. Last summer, when precipitation was heavy, many streets and underpasses were completely flooded, with the stairs of some metro stations turning into veritable waterfalls. Berlin’s sewer system just can’t absorb these huge volumes of water all at once. This also poses a problem because the city has a hybrid sewer system in which rainwater and sewage are channelled off together. So if the system overflows, the water drains off into the Spree River and other waterways and lakes. This is nothing to worry about where rainwater is concerned, but it’s a big problem in the case of untreated sewage water. Which is why we are catching the rainwater and channelling it directly into the Spree River rather than into the sewers. Since the site of the Humboldt Forum covers an area of roughly 40,000 square metres, we’re talking about several million litres of rainwater that the sewer system won’t have to absorb.

Interview: Kristina Simons

Author
Thomas Herrmann

Thomas Herrmann is a graduate engineer for supply engineering and energy consultant and head of the Facility Management section of the Humboldt Forum Foundation in the Berlin Palace.