A lab is looking to remove the current two large chillers they are using to feed cold to there experimental chambers. These machines only recirculate the water as a cooling mechanism. The have installed air cooled room on the back side of the lab constant temp of 4°c. They have tried placing a 300L tank in the room to keep the water cold and have a continuous 1/2" pex loop feeding the machines. The machines require a constant water temp between 5-12°c. When all four chambers are runing the water temp in the tank reaches 21°c. Is there a way to reduce the water temp with out useing lage chillers ? Attached is a sketch.