Data centre cooling

With the explosive spread of data-intensive applications such as artificial intelligence (AI) and IoT, even the most modern data centres in which powerful IT devices are installed at the highest density tend to be physically less and less able to handle the workloads that arise.

Cooling plays a central role in data centres. Waste heat has to be dissipated from the servers and the humidity regulated in order to ensure effective data security. You can use air, water or evaporative condensation. The aim is to keep the operating temperature within a defined range with as few fluctuations as possible. The optimum is usually between 22 and 25 degrees Celsius. Temperatures up to 27 degrees are also possible.

Data centre cooling is a global growth market that will swell to 15.7 billion US Dollars by 2025, according to MarketsandMarkets.

The topic of sustainability
Data centre operators not only have to ensure the security of data and applications, but also keep an eye on sustainability and profitability. By 2030, data centres are expected to account for up to eight percent of global electricity consumption. If you think about it in terms of “cost” alone, it´s understandable that data centre energy efficiency is such an important issue, regardless of whether it´s an enterprise, hyperscale, colocation, cloud-based or edge data centre.

One of the most important metrics for sustainability is Power Usage Effectiveness (PUE). This value results from the ratio of the energy that a data centre requires overall to the energy that the IT infrastructure uses for computing. The closer the value is to 1, the more efficiently a data centre works. With modern technology, values below 1.3 can now be achieved. This is only possible with a reliable cooling system that uses as little energy as possible.

Three methods of cooling
There are basically three types of cooling in a data centre: free cooling (direct and indirect, i.e. with a heat exchanger), mechanical cooling (using refrigerants) and evaporative or adiabatic cooling using water or water vapor. Air and liquid cooling are the most popular cooling methods.

Cooling using circulating air within the premises is particularly suitable for smaller to medium-sized data centres. An additional hot or cold aisle concept with Closed Coupled Cooling (CCC) ensures that cooling efficiency is maximised. The cool air only circulates in the devices or in the racks themselves. The latter is the method used, for example, in Datwyler´s Smart Modular Data Centres (SMDC). It is generally more efficient than room-based cooling concepts as it combines hot and cold aisle containment.

This method can also be implemented with liquid cooling. Liquid is a better conductor of heat than air and is also suitable for higher device densities and devices that generate above-average heat, for example in high-density data centres. Compared to air cooling, liquid cooling is a more efficient and less expensive cooling system to operate for hyperscale data centres, especially when installed directly on the devices in the data centre that require the most cooling.

Liquid cooling is a growth market
There are two main types of liquid cooling: immersion cooling and water cooling. With immersion cooling, the entire electrical device is immersed in a non-flammable dielectric liquid in a closed system. Or hoses lead the dielectric liquid directly to the chips or motherboards. 

In addition, there are two types of immersion cooling systems: In single-phase immersion cooling, the dielectric fluid remains in a liquid state after it has absorbed the heat from the components. The heat is transferred to a heat exchanger, dissipated there, and the cooled liquid is returned to the circuit. In contrast, two-phase immersion cooling uses a dielectric liquid that boils at a relatively low temperature (typically between 50 and 60 degrees Celsius or 122 and 140 degrees Fahrenheit) and turns into vapor. The vapor rises, condenses on a cooling surface (e.g. a coil), turns back into liquid and returns to the tank. Both cooling methods are effective. However, two-phase systems generally provide higher thermal efficiency due to the latent heat of vaporization.

With water cooling, the cooling also takes place directly on the chip – with all the advantages mentioned. According to market observers, this method is on the rise in mega data centres, especially when cooling servers, GPUs and flash memories, because direct cooling with water does not yet work so well for components such as hard drives, storage tapes, UPSs and network components.

The liquid and immersion cooling market is expected to reach 2.5 billion US Dollars by 2030.