In the Danish city of Odense, the depths of the winter months see average temperatures verge on -1℃. And for the last few months, many of us have been unknowingly warming up their households by the click of a "Like" button on Facebook, or the sharing of a post on Instagram.
Facebook runs a two-building, 50,000 square-meter data center in Odense, and the tech company has teamed up with local district heating company Fjernvarme Fyn to redistribute the heat generated by the facility's servers straight to the nearby community's radiators.
In most data centers, air conditioners cool down the servers to keep them at an optimal temperature of about 28℃, and pump hot air out into the atmosphere. Facebook's facility in Odense, instead, recycles the heat to eventually deliver it to households.
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The heat is transferred via copper coils filled with water, which link one of Fjernvarme Fyn's heat pump facilities to the 176 cooling units in the data center. The hot air in the servers heat up the water flowing through the coils, which then travels back to the heat-pump facility.
Fjernvarme Fyn's heat pumps then use the warm water to raise the temperature of the water loop that provides hot water to Odense's households' radiators.
Lauren Edelman, energy program manager at Facebook, explained that the system is already working in Odense, and is currently being used to warm a local hospital and several other buildings in the surrounding community.
"We have been producing heat for the local community for the last few months," said Edelman. "It is only in partial operation because it is the summer, and there is lower demand, but we are excited to ramp up production throughout this year."
When the system is running at full throttle, Facebook expects that the data center will recover 100,000 MWh of energy annually, which is enough to warm 6,900 homes.
Recycling the heat wasted by data centers, in itself, is not a novelty. As early as 2008, the Swiss town of Uitikon, just outside Zurich, started funneling the heat produced by a nearby IBM data center to warm up a local swimming pool.
And for the past three years, Amazon's corporate headquarters in Seattle has been kept warm by using waste heat from a non-Amazon 34-story data center in a neighboring district, which houses over 250 telecom and internet companies.
According to Facebook, however, the scale of the project in Odense is yet to be matched, with up to 25 MW per hour of usable heat produced, to warm up thousands of buildings instead of only a few.
In addition, the tech giant stressed that the heat distribution system it has developed uses exclusively renewable energy. The data center is entirely supplied by wind power, and Fjernvarme Fyn's facility only uses pumps and coils to transfer the heat. As a result, the project is expected to reduce Odense's demand for coal by up to 25%.
Although Facebook is keen to use the heat recovery system in other locations, the company didn't reveal any plans to export the technology just yet. "Our ability to do heat recovery depends on a number of factors, so we will evaluate them first," said Edelman. For example, the proximity of the data center to the community it can provide heat for will be a key criteria to consider.
Improving data centers' green credentials has been a priority for technology companies as of late. Google recently showcased a new tool that can match the timing of some compute tasks in data centers to the availability of lower-carbon energy.
The platform can shift non-urgent workloads to times of the day when wind or solar sources of energy are more plentiful. The search giant is aiming for "24x7 carbon-free energy" in all of its data centers, which means constantly matching facilities with sources of carbon-free power.
Facebook has announced similar objectives in its first sustainability report, which the company released together with the news of its data center heat-recovery system in Odense. The new report shows that the tech giant has cut greenhouse gas emissions by 59% compared to 2017 levels, and that it has reached 86% renewable energy for all of its operations.
In 2018, Facebook committed to reduce greenhouse gas emissions by 75% and powering global operations with 100% renewable energy by the end of 2020.
Edward Palmery, Facebook's director of sustainability, said: "We will continue hammering away at our carbon footprint to reduce it further. In 2019, we made significant progress, and we are very much in line with our 2020 goal."
The company's sustainability report shows a renewed focus on the use of clean energy in data centers. Facebook stipulates that it is committed to accelerating the transition to renewable energy in the communities where it operates, which is why all of the company's renewable energy projects are on the same electrical grids as the data centers they support.
Some of the electricity generated by Facebook's renewable energy projects, therefore, may end up powering the tech giants' data centers. That is not to say, however, that the company can run its data centers entirely on renewable power.
Facebook, in fact, had already admitted that given the scale of data-centers, supporting facilities with 100% renewable energy "make on-site solutions nearly impossible". The company's commitment to renewable energy, therefore, also includes green tariffs and corporate purchases of renewable energy projects.