Servers generate lots of heat, and a growing number of data centers are using this heat to warm nearby homes. The latest company to embrace this strategy is Facebook, which announced Monday that its cloud campus in Odense, Denmark will connect to a neighborhood district heating system.
Heat recycling projects allow huge data centers to contribute large amounts of heat energy to their communities. Facebook expects the Odense system will warm 6,900 homes, and thousands more homes are being heated by data center servers in Stockholm and other European cities that employ district heating.
These data centers are designed for peak sustainability, combining renewable energy, efficient cooling systems, and heat recycling to dramatically reduce their impact on the environment, while boosting their usefulness to the local community. It’s a virtuous cycle that aligns all facets of data center operations to optimize energy impact.
Heat recycling also positions data centers as beneficial neighbors, which could help counter growing tensions about data centers’ impact on their communities. This has become an issue in U.S. data center projects that require expanded energy capacity, either through on-site generation or new high-capacity transmission lines. (See The NIMBY Challenge: A Way Forward for the Data Center Industry for more on this trend).
These European projects show how district heating systems can create new types of relationships between data centers and local residents.
There are challenges in making heat recycling work in the United States, especially in existing data centers. But recent mixed-use developments by Amazon and Telus offer a model for using server heat recycling in office buildings in urban centers.
How Server Heat Recycling Works
Temperatures in most data center hot aisles range from 80 to 115 degrees Fahrenheit (27 to 46 degrees Celsius), still fairly low temperatures for some heat recovery strategies. Data centers can use heat pumps to boost the temperature of the waste heat, making it more valuable for use in district heating, often by transferring the heat to liquids that are easier to transport and incorporate into heating systems. This approach requires additional ducting and pipes, but these costs can be offset by selling the heat energy to local utilities.
District heating systems like data centers because they provide steady heat around the clock, including the weekend.
In Denmark, Facebook is building a new heat pump facility that will capture heat from servers and prepare it for use in a local district heating system operated by utility Fjernvarme Fyn.
“In Odense we will direct air heated by the servers over water coils to recover the heat by raising the temperature of the water,” Facebook said. “The temperature of the warm water is further raised by a heat pump facility powered from renewable energy. The hot water is then delivered to the district heating network and distributed to the local community.”
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Here’s a look at how the system will work (click for larger image)
The Odense facility was announced in January, and is part of a rapdi expansion of Facebook’s data center capacity around the globe.
When complete, Facebook says the heat recovery infrastructure will enable the recovery of 100,000 MWh of energy per year, which can produce enough heat to warm 6,900 homes. “At all of our data centers, we look to make our operations as sustainable as possible, but our ability to recycle heat from our servers is unique to our Odense data center,” the company said.
Stockholm Looks to Lead
Stockholm is seeking to establish itself as a hotbed for server heat recycling. Ninety percent of the city’s buildings are connected to the district heating network.
“It’s fantastic that a growing number of companies are connecting their systems to our district heating network and stop wasting data center excess heat,” said Erik Rylander, Head of Stockholm Data Parks at Fortum Värme. “It’s smart and profitable, and together we can make Stockholm even more sustainable.”
Fortum Varne has partnered with city officials and economic development agency Invest in Stockholm to create Stockholm Data Parks, a new data center campus that builds upon the city’s early successes in heat recycling. The developers have created a companion web site, Open District Heating, to market the concept to the data center industry. The utility has developed rate plans for the price of energy it will pay data centers for their recycled energy, creating a market for the server exhaust heat.
The effort has paid off in recent customer wins. Last week Swedish IT provider Borderlight AB said it will create a 5 megawatt data center at Stockholm Data Parks to house high-density servers for its GoGreenHost unit.
“Our target is to become a leading supplier of advanced IT services coupled with efficient heat recovery from data centers that reach close to 100 percent recovery of consumed electrical power,” said Sten Oscarsson, CEO of Borderlight and GoGreenHost AB. “GoGreenHost technology creates a new potent heat energy source with a very low carbon foot print. Our plan is to contract installation of 30 MW in new data center capacity 2017 and another 60 MW 2018 in sizes from 1-6 MW per site, all connected to a redundant high capacity fiber backbone.”
Stockholm Data Parks says the Borderlight faciltiies could ultimately provide enough energy to heat 10,000 homes.
In July, Fortum Varne announced that one of fashion retailer H&M, which has been using heat recycling for its Stockholm data center since 2013, would build a new 1 megawatt data center at Stockholm Data Parks. European data center specialist Interxion has also agreed to 3.5 megawatt data center within Stockholm Data Parks.
Amazon Taps Westin Building for District Heating
While district heating systems are used in a number of major cities in Europe, they are less common in the United States. Several new urban development projects are including district heating systems that can tap server exhaust heat from adjacent data centers.
In Seattle, Amazon’s newest office buildings in the Denny Triangle area recycling heat energy from servers housed in data centers within the nearby Westin Building, the city’s largest carrier hotel. Server exhaust heat will be recycled through underground water pipes instead of being vented into the atmosphere. Amazon expects that the system will heat nearly 3 million square feet of office space. The company says this approach is nearly four times more efficient than traditional heating methods and will also enable the Westin Building data center to cut back on the energy it uses to cool its building.
A similar approach is used by the Telus Garden office tower in Vancouver, which uses heat energy from servers inside the nearby Telus data center to provide heating for the entire 450,000 square foot complex.
Interested in more info on data center heat recycling? Check out this excellent column Mark Monroe wrote last year for Data Center Knowledge