In a novel first for green computing, excess heat from data centres in Stockholm will be used to heat homes across the city.
Data centres are the engine rooms of our digital age, but they can also draw down a lot of electricity and generate a lot of heat that, until now, has gone nowhere.
Under a bold new partnership between the City of Stockholm, Fortum Värme, Ellevio, Stokab and Invest Stockholm, excess heat generated by data centres will be funnelled back into a heatsink that can then be distributed to the city’s municipal heating system.
In this way, a data centre with 10MW capacity can heat around 20,000 modern residential apartments.
The win-win for the data centre is a new revenue stream as well as a net climate positive through practical reuse of CO2 intensive heat.
Under the Stockholm Data Parks initiative, a number of greenfield sites as well as existing buildings in Stockholm’s technology hub Kista have been earmarked for conversion.
The infrastructure providers have committed to provide power, cooling-as-a-service (CaaS), heat recovery and dark fibre.
A recent tax change in Sweden has meant that the electricity price for large data centres in Sweden is now below €0.04 per kilowatt – the lowest in the EU.
The Stockholm Data Parks initiative will contribute to the city’s target of phasing out fossil fuels altogether by 2040.
Hot in the city
According to Erik Rylander, head of Open District Heating under Fortum Värme, Stockholm already has 25 years of experience in capturing and reusing excess heat from steel and paper mills and other manufacturing facilities.
He said that more than 30 data centres are already connected to Fortum Värme’s network for cooling and heat recovery, including data centres belonging to Interxion, Bahnhof, Ericsson and H&M.
“To understand what makes it possible, we have large heating districts that cover most of our cities,” Rylander told Siliconrepublic.com. “The total heatsink in the heating system delivers up to 12 terawatt hours a year to customers. This could include the heat that can be recovered from data centres.
“Across Stockholm, there are more than 10,000 buildings connected to the district heating system where this heat can be used. The district heating system of Stockholm comprises more than 2,800km of piping.”
Rylander said that the selection of districts such as Kista is made possible by the close proximity of grid infrastructure to clusters of data centres.
“We have many big companies located in Stockholm, but not so much heavy industry. The data centre industry here could easily and logically fit into the plan and help heat the Stockholm area.”
The move could also be a boost for Stockholm’s digital credentials. The city, which is home to locally grown but globally known tech giants like Klarna, Spotify, King, Skype, Mojang and Ericsson, attracted 15pc of Europe’s FDI in 2014.
For data centres, the move by the city is a tantalising prospect: free cooling in exchange for waste heat.
According to Torbjörn Bengtsson from Invest Stockholm, the advent of using excess heat to warm homes represents the third age of the evolution of green computing.
He said that in the first generation of data centres, excess heat was managed by cooling machines and in the second (current) phase, renewable electricity is employed and free-air cooling is used to manage heat rejection.
But under the new proposal, CaaS heat recovery would offer chilled water in exchange for waste heat that would then be used to heat apartments.
“These are ambitious goals for Stockhom,” Bengtsson said. “We wanted to combine the tech strengths of our city with our green ambitions. The data centres generate a lot of heat and it was just being ventilated out.
“We decided it is time to do something about it.”
Stockholm’s example is one that other cities around the world should consider.
Dublin, for example, has more than 30 data centres, mostly clustered along the western fringes of the city.
If all 30 – supposing they were of 10MW capacity – were harnessed in the same way that Stockholm is proposing, excess heat from the data centres could potentially be used to heat up to 600,000 homes.
But that, of course, would require joined-up thinking.
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