Finnish city uses data centres to heat its hot water

Heat generated in data centres in Mäntsälä, Southern Finland, is being used to warm the city’s water supply.

The initiative to tap into the waste data centre heat began when a heat recovery plant opened in December 2015 at a Yandex Data Factory data centre in the city, funded by Finnish energy company Mäntsälä Sahko. The recovery plant extracts the data centre servers’ excess heat output and uses it to heat the city’s district heating supply.

Water is fed from the city’s supply system into heat exchangers at the data centre where large ventilators pump in hot air generated by the servers. The hot air heats the water to 30–45°C, when it is then sent to the heat recovery plant where the temperature is boosted to a required level of 55–60°C. Once the process is complete, the water is transmitted back into the city network.

The project is expected to reduce heating costs for Mäntsälä citizens by 5% in the coming year and will cut utility providers’ gas consumption in half. It is expected to cut the city’s heating carbon emissions by 40%. The project also allows the company to cut expenditure on the data centre’s current electricity consumption by as much as a third, says Yandex.