When constructed in 2008, the Cool Circle represented a unique project in Europe and is used to cool various buildings and research equipment on campus. Often, heat/cold storage takes place in the ground, but this is not possible on the UT site due to the composition of the soil. It was therefore decided to take an unconventional approach. The Cool Circle is a 10 meters deep and 35 meters wide large reservoir that stores over 10 million liters of cold water.
At night, the water in the pond is cooled: in summer with cooling machines, in winter to the outside air. The cool night combined with the cooling units cool the water to about 8 to 10 degrees Celsius. Through a loop system, the water is distributed through the buildings. The cooler water flows in at the bottom of the reservoir, while water of about 18 degrees that has been used to cool buildings flows in at the top. This creates a temperature gradient, with the top layer insulating the cooler water: a so-called ‘thermocline’.
At the bottom of the reservoir sits the cooled water and at the top sits the warmed water returning from the buildings. The boundary between cold and hot water drops during the day, but cold and hot will never mix. This makes for a very efficient system.
The cold circle has a cooling capacity of 11 MegaWatts, which is equivalent to the capacity of over 70,000 refrigerators. The cold circle also acts as a storage buffer in the event of a major fire. Currently, the Horst, Carré, Nanolab, Range, Ravelijn, Hall B, Zilverling, High Pressure Lab, Signal House and Tee House are all connected to the cold circle.
