What’s Free Cooling?

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Freecooling uses outside air to cool water, reducing electricity consumption. It works best in locations with temperatures below 59°F/15°C and can be retrofitted to existing systems. It’s ideal for data centers, but outside air can harm electronics and filters add cost. The system cannot operate below 39°F/4°C.

Freecooling is a method of using the outside air temperature in the natural environment to reduce the temperature of the stored water. This chilled water can, in some cases, completely replace the chiller in a cooling system, significantly saving on electricity consumption. Various industries use free cooling systems, from hotels and hospitals, to server farms in computer data centers and companies that want to use green technologies to protect the environment.

The free cooling idea works better in some locations than others. In the UK, for example, the temperature is below 59° Fahrenheit (15° Celsius) almost 75% of the year, making free cooling very practical for many needs. In addition, the UK offers energy efficient loans for the installation of freecooling systems, which can easily be retrofitted to standard chilled water units or incorporated into new ones. It is also possible to incorporate freecooling systems into standard air-cooled or heating, ventilation and air conditioning (HVAC) units, but the efficiency level of this type of upgrade is lower than modernizing a pure water-based chiller .

Computer rooms generate a significant amount of heat and also consume a lot of electricity and are, therefore, a prime market for free cooling, often referred to as economizer systems. Economizer systems can reduce the energy consumption of cooling equipment by 30-50%, depending on the outdoor temperature and humidity conditions. It is recommended that outdoor temperatures average in or below a range of 68-77° Fahrenheit (20-25° Celsius) for a free cooling system to work well. Relative humidity should also be below a maximum of 60% to avoid damaging data center equipment by introducing external moisture.

One drawback to this technology, especially when used to cool sensitive electronic equipment, is that the outside air can be harmful to the electronics. A study of information technology (IT) original equipment manufacturers (OEMs) found that there was an 81% increase in IT equipment failures over an 8-month period, once a system was in place of free cooling. The high quality filters in the system are designed to capture outside particulate matter, but they are not 100% effective and add cost to the system as they become more sophisticated to clean the outside air.

The limitations of freecooling systems also require that the outdoor water tower must not drop below 39° Fahrenheit (4° Celsius), as frozen water will damage the equipment. This makes environments where temperatures routinely fall below 41° Fahrenheit (5° Celsius) unsuitable for the use of freecooling chillers. In locations such as the Northern Hemisphere, this generally means that such heat exchanger systems can be used for two or three seasons of the year, but must have a more conventional system to sustain them during periods of inactivity.




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