A government-funded district heating system is taking waste heat from Interxion's Vienna data center campus, to the neighboring Floridsdorf Hospital. From figures quoted in the media, it seems the project is heavily dependent on heat pumps installed by Wien Energie.

The Austrian government is paying around €3.5 million ($3.7m) from environmental funds to lay an insulated pipe between Interxion's campus on Louis-Häfliger-Gasse, and the Floridsdorf Klinik, located virtually next door on Brünner Strasse. Hot water from the data center, boosted by electric heat pumps, will be used to warm the hospital from 2023.

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Folridsdorf Klinik (left) is across the road from the Interxion campus – Google Maps

The project is expected to save 4,000 tons of CO2 emissions per year.

Server heat beats Russian gas?

"We need to end the dependence on Russian natural gas. Only when we create our own energy are we strong," said Austria’s Environment Minister, Leonore Gewessler on Facebook. "Klinik Floridsdorf is a real pioneer and uses the data center warmth with heat pumps to heat the whole area. This is smart, energy-efficient, and delivers half the warmth necessary for the clinic."

Emphasizing the drive to energy independence, by harvesting otherwise wasted energy, she said: "Projects like this protect our independence and I am happy that we can support them."

The Interxion facility has some 120,000 servers on site in two data centers. The campus is due to expand on nearby land, after it was announced in 2020.

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– Leonore Gewessler

The hospital, a few hundred yards away, already has a heat circulation system, with 90,000 m of pipes. It uses 73,000 cubic meters of hot water per year, and the buildings need heating on an average of 150 days per year. The organizations estimate that the hospital will be able to get 50 percent to 70 percent of its heat from the scheme.

How much heat energy actually comes from the data center is not clear from. The servers will be air-cooled, which does not produce very high-grade heat. According to Vienna Online, the water leaves the server room at a tepid 26°C, while European news source TheMayor.eu reports the project will deliver water to the hospital at a much more useful 82C.

Another story on SocialPost, explains the difference. Apparently, Wien Energie is installing three heat pumps, each with a capacity of 1 megawatt, in the Floridsdorf Clinic’s energy center. These extract and boost heat from the warm cooling water, to deliver water to the Floridsdorf Clinic to 82°C. The heat will be used in the hospital, and the cooled water returned to Interxion.

Interxion Austria marketing manager Ingemar Wandl told DCD in an email that heat energy in the system came from the data center, and the heat pump simply increased the temperature, drawing an analogy with the way an electrical transformer increases the voltage of electricity: "The described system can be compared with the principle of low voltage (26°C), a transformer (heat pump) and high voltage (82°C). The transformer is technically responsible for increasing the voltage, but the basis for the total power lies in the low voltage."

– Wien Energie

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