There is a lot of talking about free cooling, at different levels, and it is a really interesting application for industrial process cooling tasks. We are in fact dealing with free cooling when we have a low energy consumption cooling system.
But when is it possible to install a free cooling system? Often there are process industries that require cooling activities within their production process with rather low cooling water temperatures. Let’s say 10-15 or even 20° C. These are requirements that an evaporative tower cannot satisfy during the hot season, nor a system with a radiator, which exploits heat dissipation through the air. It is therefore necessary to use refrigerating groups.
But there are environmental conditions, during the cold season, or even during the coolest hours of the day, in which a refrigeration unit is essentially a waste, because being able to exploit the favorably cold environmental conditions in these situations, a dry cooler could be enough, i.e. a heat sink. What kind of advantages does a free cooling system bring?
In terms of costs, this is clearly something more that we need to implement within the refrigeration system. Basically, you must accompany a refrigerator with a free cooling system, an object that probably during the summer season will be useless. But during the winter season, it will allow to turn off the chillers. This actually leads to significant energy savings.
Taking a rough balance, with a refrigeration unit with COP 3 (Coefficient of Performance) to obtain a dissipation of 90 thermal kW, we have an electricity consumption of 30 kW, more or less. Of this 30 kW, 24-25 kW is typically consumed by the refrigeration compressors aimed at cooling the water. By using a free cooling system, these 24-25 kW will vanish because only the kW used for ventilation will remain, of course, and the kW dedicated to the water circulation pump. It is therefore clear that we will have significant energy savings while dissipating the same amount of thermal energy.
Now it’s also possible to make a couple of evaluations to understand what the return on investment of a free cooling system could be. Let’s say that there are many applications in which free cooling is certainly an excellent solution. It clearly depends on the latitude: the more the system is installed in a cold region or one that has a longer cold season, the easier it will be to have a shorter ROI of the free cooling solution.
