Free Cooling for All – Data Center Heat Generation

Mechanical

Wednesday, 04 June 2008 10:52

Written by Rakesh Dogra

That is to say that the electrical energy which is being fed into the circuits to perform the intended tasks also produces a lot of heat, which may seem miniscule considering the size of such integrated circuitry, but the very same size, has become a source of problem. With increasing density of the electronic paraphernalia associated with computers, servers and so on, the amount of heat generated is also on the rise and the effective dissipation of this heat is a problem which is increasing becoming complex and costly over time.

Data Center Heat Generation

Data center is the generic term which is used for a place where lots of computer related paraphernalia is placed which may perform different functions such as connecting to the internet, storing vital information and data and so forth. With the miniaturization of technology, the data center equipments are becoming increasing dense and hence result in production of lots of heat which needs to the dissipated, the lack of which might render the equipment useless or damaged. Obviously the conventional approach to such cooling would be to place the necessary cooling and air conditioning equipment to drain the heat from within the physical space, which is an effective method but it might prove very costly in the long run, hence we will look at another methods which might tend to balance these requirements of effective cooling and lower operations costs.

The Concept of Free Cooling

To a person hearing this term for the first time, it might seem to be a misnomer for we all know that nothing is really “FREE” in this world and the word itself produces an image of some flashy advertisement rather than a scientific concept. But let me explain that although the term free cooling does refer to cooling which is “free” in a way, it does not mean totally free of cost. The further discussion elaborates this very point, and the pros and cons of using free cooling for data centers.

Actually the term free cooling refers to an arrangement wherein the normal cooling equipment such as the chiller is bypassed or not fully utilized, depending on out side climatic conditions such temperature and humidity. Chillers are used to extract heat from the data centers and they could be either water cooled or air cooled with appropriate economizers fitted in the system. These economizers tend to create the free cooling effect by utilizing the cool air of the outside atmosphere to provide cooling effect inside the data center building or space, thus bypassing the chiller in the process.

This seems a very lucrative idea but it is not possible all around the year since climate at any place across the globe tends to vary in seasons or cycles. It is only that when the outside temperature drops to a certain level that free cooling kicks in, otherwise the normal chiller operation continues to cool the system. Even if this free cooling is done for a few months each year, it has been observed to result in substantial savings of costs in this way.

Advantages of free cooling

• It saves energy costs which is obviously a big YES for any business and is good not only from the financial point of view for the particular organisation utilizing the concept but also for the overall environment of the planet.

• Air side economizers are a much better proposition compared to water side economizers in circumstances where the outside temperatures are relatively higher.

• Water side economizers are used more in conditions where the outside temperatures are relatively lower, and the cooling towers are used to cool the water, which is in turn used to cool the building or data center space.

• Since the chiller is bypassed fully or partially during the cut-in periods of the free cooling system that means that the compressor in the system is given adequate rest along with the other parts of the chiller, which obviously means less wear and tear and hence a prolonged life for the system.

• The changeover from chiller to free cooling unit is not manual but done automatically depending on the settings, which means that climate fluctuations can be taken care of automatically.

• In situations where free cooling isn’t installed, the cost of installed the additional paraphernalia is quite a bit, but given the energy savings resulting from a typical installation, the payback period could be as less as one calendar year which certainly justifies the case for installation of the same.

Drawbacks of free cooling

• The efficiency of free cooling depends to a great extent on the external conditions of climate such as temperature and humidity, which obviously is a natural phenomenon and hence beyond control.

• In regions where the climate is hot and humid, the free cooling cannot be effectively used since the amount of energy consumed in controlling the humidity of the incoming air nearly equals the energy savings resulting from the use of free cooling, thereby canceling any positive gains from the same.

• Water side economizers are relatively costly to retrofit obviously because of their more complex construction and hence their use in avoided in warmer climates.

Conclusion

Hence we can conclude from the above discussion that free cooling is an effective means of saving energy costs required for cooling considerations of data centers, although they have their own limitations with regards to the outside temperatures and humidity of air. Despite these limitations free cooling should be utilized to the maximum possible extent as this would decrease the dependency on the chillers at least for some proportion of time in the overall calendar year.

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