Server room heat recovery and free cooling with CO₂ and propane

Free cooling is a possible solution when the temperature for the cooling load is above the outdoor temperature. To increase efficiency on a yearly basis, the objective is to raise the temperature level at which free cooling can be applied in order to achieve more hours of free cooling operation. By supplementing the traditional glycol based free cooling system with a CO₂ based system, the benefits of phase transition and an increased heat transfer coefficient are utilized and the temperature limit is raised, lowering the annual energy consumption. To further reduce operating costs the heat is recovered from the server room and the canteen refrigeration system by the use of heat pumps. Calculations show a significant reduction in the energy consumption.