The Evolution of Datacenter Cooling

The Origin of Datacenter Cooling

February 21, 2019

What we refer to as datacenters today, started out as computer rooms in the 60’s to house the first mainframe computers. While computers and servers evolved quickly over the years, an evolution of the datacenter itself per se and more specifically the cooling was not really necessary as the evolution in computing also brought significant innovations that allowed (apart from a few notable exceptions such as the CRAY 2 in 1985) denser computing and continued cooling with air and fans.

Liquid immersion cooling isn’t a new technology, it has been widely used since the 1940s to cool high-voltage transformers.

Front view of 1985 Supercomputer Cray-2

In the 1960s, IBM developed the very first direct liquid cooling system.

In the 1980s, with the advent of metal oxide semiconductors, the concept of a liquid cooling solution became less of a priority as this new method of packing multiple transistors didn’t generate the same proportionate heat as the size of the transistors and therefore their voltages were drastically reduced.

Today, cooling systems are definitely more complex and high-tech than 4-5 years ago, as cooling has had to catch up with the demands for denser computing and in part the beginnings of Moore’s law breaking down.

Immersion Cooling has come back into the spotlight (kind of analogous to the case for the electric car) and there is evidence that it will represent the most efficient cooling solution in the years to come and become mainstream in the not so distant future. Not everybody is fully convinced that Immersion Cooling can represent a viable solution, typical for anything different from the current normal way of doing things. Submer (amongst other) are invested in Liquid Immersion Cooling and are gathering increasing support for their vision of this tech as the present and the future of next generation datacenters.

Different Methods of Cooling for Datacenters

Cooling a datacenters typically takes a lot of energy (>50% depending on location and design) and a lot of planning. Traditionally, there are three different ways to cool a datacenter: air-based cooling, liquid-based cooling and a hybrid of the two, and within these categories are a couple different methods.
Among the air-based cooling systems, we have:

  1. The cold aisle/hot aisle method: it focuses on separating the cold air from the hot air by facing the cold sides of the server away from the hot sides producing a convection system. This method isn’t the most effective, as it forces datacenter managers to push more cold air into the room.
  2. The cold or hot air containment method: it takes the previous method and tries to improve it by physically containing the servers, so the hot and cold air don’t mix. This method works better than the cold aisle/hot aisle method, but datacenters still experience hot spots.
  3. The in-rack heat extraction method: it eliminates the hot air by adding a compression cooler built into the server rack.

When it comes to liquid-based cooling systems, it is necessary to distinguish between water, synthetic fluid and mineral coolant.

Water-cooled racks (otherwise known as rear-door chillers) have water flowing alongside the racks, but never actually touching the servers. This solution works well, but there is still the legitimate concern of water leaking onto the servers and components and compromise the IT Hardware integrity, not to mention the fact that the chilling is done with compressors and uses quite some energy to cool.

Direct liquid cooling mostly refers to water or other liquids that are delivered directly to a hot plate which is only on CPUs and GPUs, dealing with 70% of the heat.

With rear door cooling and direct liquid cooling, it is normally advised to have a secondary form of cooling such as a traditional CRAC unit to handle the excess heat in the room.

Liquid Immersion Cooling means that the entire servers (switches, etc.) are completely submerged in a synthetic or mineral fluid, designed to deal with 100% of the heat and preserving the IT Hardware (no particles being shot) and is the most efficient method to save energy if combined with dry coolers (with or without adiabatic functionality) using only ambient temperatures to lower the warm water of the secondary cooling loop.

Immersion Cooling for Datacenters

Just like the containment method improved the cold aisle/hot aisle system, the Immersion Cooling method designed by Submer can be seen as an improvement of the water-cooled racks system. The real revolution done by Submer (and that banishes all the doubts and fears about having your IT Hardware in direct contact with a liquid) is the use of a specific dielectric (does not conduct electricity) fluid, called SmartCoolant, that allows to dissipate the heat produced by the IT Hardware while preserving and protecting it. This cutting-edge method goes against the grain of the traditional air-based cooling systems and, considering the extremely high densities that can be achieved and the energy saving, we can quite confidently say that it represents the future of datacenter cooling.

Now, it is true that implementing a completely new system of cooling can seem difficult. Some people in the industry might even question if the change in method makes financial sense since lowering one's costs isn’t everything one needs to consider. All these doubts and concerns are legitimate. Submer guarantees unprecedented IT Hardware densities, in a very limited space, meaning:

  1. Less physical space compared to traditional air-based solutions (about 85%)
  2. Energy saving (about 50%) and lower maintenance costs
  3. Cheaper Builds
  4. PUE better than 1.03
  5. ROI in less than one year

An Efficient Solution

Immersion Cooling is more efficient than any air-based or water-based systems. According to Data Center Frontier, it is 1400 times more effective than traditional air-cooling. With air-based systems, fans need to be blasting 24 hours a day even when it isn’t needed (the old, unsolved question of “idle” datacenters).
With Submer Immersion Cooling, you just don’t need fans anymore and this means 15%-25% less power consumption than traditional methods. The typical datacenter and colocation provider will see up to 50% decrease in general electricity cost by adopting a datacenter Immersion Cooling solution.

Michael Isberto of Colocation America & Matteo Mezzanotte 

(a special thanks to Diarmuid Daltún)