Free cooling

Free cooling is an economical method of using low external air temperatures to assist in chilling water, which can then be used for industrial processes, or air conditioning systems. The chilled water can either be used immediately or be stored for the short- or long-term. When outdoor temperatures are lower relative to indoor temperatures, this system utilizes the cool outdoor air as a free cooling source. In this manner, the system replaces the chiller in traditional air conditioning systems while achieving the same cooling result. Such systems can be made for single buildings or district cooling networks. For a human-powered version, see yakhchal. When the ambient air temperature drops to a set temperature, a modulating valve allows all or part of the chilled water to by-pass an existing chiller and run through the free cooling system, which uses less power and uses the lower ambient air temperature to cool the water in the system. This can be achieved by installing an air blast cooler with any existing chiller or on its own. During low ambient temperatures, an installation can by-pass an existing chiller giving energy savings of up to 75%, without compromising cooling requirements. In heating, ventilation, and air conditioning (HVAC) in winter months, large commercial buildings interior spaces may need cooling, even while perimeter spaces may need heating. Free cooling is the production of chilled water without the use of a chiller, and can be used generally in the late fall, winter and early spring, in temperate zones. Free cooling is not entirely free since the chiller is still operational. Assuming that the system can utilize free cooling, there are three ways to use free cooling: The cooling tower water can be directly linked into the flow through the chilled water circuit. If the cooling tower is open then a strainer is required to eliminate any debris that could accumulate within the tower. The cost savings are associated with the limited use of the water chiller energy. There is an increased risk of corrosion using this method.