The life-sized “Thermos”

On the outskirts of the Swedish city of Borås, a strange metal tower reaching 80 meters high dominates the landscape. Although it is not open to visitors, it is very much appreciated by the inhabitants, who have affectionately nicknamed it “the Thermos.” The purpose of this reservoir – because that is what it is – is to store some of the thermal energy produced by the urban heating facilities in its 37,000 m3. Borås’ municipal department* saw it as a solution of the future to limit recourse to fossil fuels during peak consumption periods. But how does it work?

“Like a gigantic accumulator capable of constantly storing and distributing hot water, all year round,” states Tobias Klahr, Veolia Sweden’s Business Area Manager for Industry. “At night, when the urban heating demand is low, it keeps the unused hot water at a constant temperature. In the case of a rise during the day, it works like a buffer tank, distributing the amount of heat required for the boilers to operate at a constant rate.”

Incorporated with the city’s thermal power plant since 2010, the Thermos improves the performance of the district heating, which is powered by a mix of renewable energy and supplementary fuel. By smoothing production fluctuations, it optimizes combustion, which ultimately leads to savings in terms of maintenance and fossil fuels. By preventing the emission of 7,700 metric tons of CO2 each year, the Thermos fulfills the civic-minded role of helping achieve the carbon neutral goal that the city has set itself by 2025.

* Borås Energi och Miljö AB, which entrusted Veolia in Sweden with running and maintaining its thermal facilities from 2006 to 2016.