Paper No 792 – Free cooling in air conditioning: Investigation of its potential in Switzerland – 14th IEA Heat Pump Conference, Chicago, USA
In air conditioning, free cooling is often used for saving energy. Free cooling is understood here as a bypass water circuit with direct recooling by the environment, not heat removal by nightly ventilation. Contrary to common practice in Switzerland, free cooling is not always economically beneficial. To estimate its potential in air conditioning systems, there are no generally applicable evaluation criteria or guidelines available. The aim of this work is to assess the free cooling potential in Switzerland by applying quasistatic simulations depending on supply temperature, application, location, circuit and type of heat discharge. The results show that supply temperature is the most influential parameter. Below 14 °C all investigated applications (except data centers) show generally less than 10% of free cooling amount in total annual cooling load, therefore not economically benefitting from it. Furthermore, the potential is strongly dependent on climate at the location. Cold regions like the Swiss alps allow longer yearly free cooling operation than warmer regions. If recoolers are used to pre-cool the returning cold water flow, the free cooling potential can almost be doubled.