When a production process requires for example cold water at the temperature of 15° C, its is necessary to install a chiller that allows to obtain water at these temperatures for the whole time period of the year. But during the Winter season it’s possible to employ direct thermal transfer systems leveraging the low temperatures of external ambient air. These are dry cooling or free cooling systems consisting in thermal transfer arrays or huge radiators with ventilation that allow to cool water.
The convenience of installing these kind of systems depends on two main factors, first of all the latitude of the installation site of the plant. Secondary, the temperature levels required by the kind of industrial process involved.
Having for example a production process that needs cooling water at the temperature of 15° C, it will be necessary to have a chiller during the Summer season. But during Winter, or whenever the ambient air temperature falls down 10° C, it is possible to obtain water at the temperature of 15° C using a classic dry cooler. Achieving a significant energy saving: it is indeed possible to completely shut down the compressors of the chiller, while keeping only the energy consumption related to the pumps that provide the circulation of refrigerated water and the fans for ventilation. For a 100 kW plant, for examples, it leads to a saving of 30 kW of energy consumption related to the compressors per hour. The energy saving that can be achieved is then directly related to the thermal duty required.
It is therefore necessary to properly evaluate both the temperatures required by the industrial process and the average local seasonal temperatures, in order to estimate the return of investment in every specific case of the implementation of a free cooling system.
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