The number of data centers is on the rise. They consume nearly 3% of the electricity produced in the world. This is not really surprising considering the enormous computing power they do on a daily basis.

They are also prone to overheating, which explains the key role thermal management plays in their operation. For this purpose, several techniques are used to keep them at an ideal temperature, i.e. between 18 and 27°C. SirEnergies presents these different cooling solutions.

Classic data center cooling systems

Data center cooling is traditionally provided by a system based on raised floors and CRAC units (computer room air conditioner) and CRAH (computer room air treatment).

These two elements put pressure on the space available under the floor, which pushes fresh air into the server entrances. Afterwards, this fresh air passes through the various components of the server, is heated and then expelled. He then joined the CRAC and CRAH units, which ensured his cooling.

Let's look at these two technologies in more detail.

The air treatment of the computer room

CRAH is a particularly effective technique in spaces where the cold reigns. This system requires the provision of a chilled water plant (or water chiller unit) contained in a cooling exchanger that uses the fans to ensure the suction of outside air.

For an analogy, the CRAH units work more or less like chilled water air treatment units commonly found in most office buildings.

CRAH units are capable of regulating fan speed in order to maintain a certain static pressure. This allows them to ensure the stability of temperature and humidity levels. In this system, ice water is also produced by direct expansion or by means of DRY.

The computer room air conditioner

One of the biggest advantages of this air conditioning system is its low cost of use. In fact, it is for this reason that it is found in a good number of data centers. Its characteristics are very similar to those of conventional air conditioners. Its operation requires a compressor.

To do this, the CRAC units havea system of integrated compressors. These provide cooling by blowing air onto an exchanger filled with refrigerant.

The presence of a mixture of water, glycol or air allows excess heat to be evacuated. Most CRAC units provide a constant volume and only modulate basic on/off operation. However, the situation is about to change with the development of new models that should allow air flow variations.

CRAC units can be placed in a variety of ways, but they are usually installed opposite the hot aisles of a data center. From this strategic position, they release cold air through the perforations in the raised floor. It helps to cool computer servers more efficiently.

Modern data center cooling systems

With ongoing research to develop more efficient techniques, other cooling systems have emerged. This is particularly the case with free cooling, adiabatic cooling, water cooling and liquid cooling.

Free cooling or air cooling

The technique of Free cooling is essentially based on the direct use of cold outside air. This is filtered in order to cool the computer equipment in the data center.

The principle of this technique is relatively simple. Fresh outdoor air, whose temperature is lower than that of indoor air, is used. It is then sent to the data rooms after humidity control and correction.

Ideally, the temperature difference between outdoor and indoor air should not exceed 10°C. On very hot days, for example, it is essential to take steps to cool the outside air before it is sent to the computer rooms.

It is also possible to run the servers at a higher temperature to optimize the efficiency of free cooling. In order to take full advantage of this technique, the choice of the geographic location of the data center should not be risky.

Adiabatic cooling

In this system with proven effectiveness, the air is humidified in order to cool the fluid. In this way, the water then flows onto humidification media, which lowers the ambient temperature.

One of the biggest advantages of adiabatic cooling is that it is not subject to the ICPE regulation (installations classified for the protection of the environment) and is also not very demanding in terms of water. This technique also makes it possible to achieve significant energy savings.

With this system, the ambient air is humidified and cooled without additional energy costs by crossing adiabatic panels. The incoming air is thus at a low temperature, which guarantees a refrigeration capacity much greater than that obtained with free cooling.

Hybrid coolers

This technique combines the wet mode by trickling water onto the batteries and forced convection provided by fans. It thus resumes, to a certain extent, The principle of dry coolers and runoff towers.

The humid mode allows maximum cooling in summer. Hybrid chillers require on average half as much floor space as adiabatic systems, not to mention their greater efficiency.

Liquid cooling

Immersion liquid cooling is a technology that is still in its infancy. It makes it possible to optimize the thermal design by directly immersing the servers in a non-conducting liquid.

This fluid effectively absorbs the heat generated by computer components during their operation. This makes it possible to improve energy efficiency and to obtain higher densities per square meter.

Although this system has not yet been widely democratized, in particular because of its high costs, its numerous advantages are attracting a growing number of companies. The liquid cooling makes it possible, for example, to reduce energy consumption, which amortizes its initial cost.

This system also ensures better efficiency in the operation of the servers and promotes the reduction of the number of moving parts that require maintenance. While it is still too early to say what will be the future of data center cooling, there is clearly no shortage of assets. For now, each company is choosing the solution that best suits them to cool their data centers.