Yes, those servers are in a bathtub – this is how immersion cooling works
Hot. The worst enemy, what limits a processor the most is the heat it generates when working at full capacity. It’s what makes your laptop sound like a plane about to take off when you open a game, and what causes one of the biggest expenses in a data center is cooling it.
The solution to mitigating this heat has almost always been ducted ventilation, with some more advanced examples using ductwork. liquid refrigeration. But what if we could go further and directly submerge the servers in containers filled with liquid? That is precisely what immersion cooling does., and there are already several companies that offer it as an alternative.
Immersing servers in liquid is no longer crazy
No, you are not getting it wrong: immersion cooling consists of immerse entire servers in liquid, so that the heat they generate is easily transferred to that liquid and cooled more efficiently. Microsoft has tried it dipping servers into the sea with positive results, but in this case we are talking about plunging data center servers into liquid-filled tanks large enough for them to be completely submerged. Here’s a video from Fujisu showing the process:
The liquid used in these cases is dielectric, which means that it is capable of isolating the electrical current that electronic devices need (unlike water, a conductive liquid). That liquid can be a mineral oil, deionized water or a solution created specifically for this use.
We can generally classify immersion cooling into two broad types: single phase immersion and double phase immersion. The single phase immersion It uses a cooling liquid that receives the heat from the submerged servers and passes through a circuit to another tank where a water circuit cools it again.
Once cooled, the liquid returns to the servers to perform its function again. In this case, the coolant never boils or evaporates, nor does it freeze. Thanks to this, too complex installations are not necessary.
The two phase immersion goes further: it uses a dielectric liquid with a low boiling point (Submer uses the example of one that boils at 49ºC against 100ºC water) and let it boil and evaporate due to the heat generated by submerged servers. The vapor that rises from the tank passes through some condensers, so that there it returns to a liquid state and “rains” on top of the tank, being able to start the process again. 3M has a video where we can see one of these tanks filled with boiling coolant:
This process has the advantage of requiring fewer circuits and valves, but the vapor escaping from the condensers causes liquid losses. Still, companies like the one in top video advertise energy cost savings of up to 95%.
Goals, advantages and disadvantages of server immersion
The Submer company website describe who can this type of server cooling be focused on: companies whose data centers cannot be in cold climates, or people who need to squeeze the maximum performance of their servers with activities such as graphics rendering (watch out for those cloud gaming services like GeForce Now The Google Stadia), or the cryptocurrency mine that already returns to be the protagonist high energy consumption.
This activity is precisely what other companies such as SCATE Ventures, who put on the table the problem of chips with more and more and smaller transistors and that therefore generate more and more heat. They promote their immersion methods guaranteeing 25% to 55% more capacity of hashing depending on the server models that are used thanks to the efficiency resulting from sinking them in liquid. According to Fujitsu, immersion cooling can save even 40% energy compared to conventional air cooling.
The main advantage is thus obvious: as the servers are cooled better, their chips can run at higher power and be more efficient. Also, we can remove all the air cooling fans that they may include. That in turn gives us quiet data centers, and that can prevent breakdowns caused by dust, floating particles or vibrations caused by those fans.
At an environmental level, in addition to the better efficiency in energy consumption, we can also add that the dielectric liquids used can be biodegradable, with a useful life that can exceed twenty years and that they do not contribute at all to global warming. And the very fact of being a liquid protects the servers immersed in it from corrosion that can appear over time.
Immersion cooling can save costs, be more environmentally friendly and extend the life of your servers, but not all are benefits
Nevertheless not everything is benefits. For starters, the initial investment to have a data center that cools by immersion is higher. And quite definitive, because reverting to standard refrigeration again costs a lot more to have to change the entire installation.
As well more physical space is required in the data center, as servers move from being horizontally placed in racks to be submerged vertically in tanks (although compensates not having to install air ventilation). And liquid-filled tanks will weigh a lot, so the data center has to be prepared to support it with reinforced floors if necessary. Let’s not forget that you have to be prepared for any coolant leak from these tanks, which can be disastrous.
The Rittal server company puts a balance In the form of a figure: you believe that immersion cooling is profitable only in cases of data centers that need to have a server density such that they consume 100kW for each rack. In cases where the needs are less stringent, conventional cooling or liquid cooling are methods that can give better results.
We are going towards an increasingly connected world, so each time we will need more and more data centers that will consume more energy. Methods such as immersion cooling, well implemented, can be a good way to reduce the impact that all those servers running constantly have.