In the past, since the mid-90s, processors have been actively cooled with fans. With a 486 processor, a small heat sink 10 mm high was sufficient to cool the processor with the air flow barely available in the housing.

Modern CPUs have a TDP value of up to 500W, GPUs up to 1500W. This means that it is no longer technically possible to cool all components with air. On the one hand, up to 30% of the energy used is lost to the high-performance fans that blow the heat out of the device, which then has to be transported outside via cooling machines using even more energy and is lost unused. Not very efficient and not favourable in terms of the electricity bill either.

Everyone knows that if you want to cool something, you use water: every modern car with an internal combustion engine does this.

Why is that the case? Well, hydrogen has the highest heat storage capacity – unfortunately, liquid hydrogen cannot be used in a technically sensible way, but fortunately water consists of 2 parts hydrogen and one part oxygen, so although it only has less than 30% of the capacity of hydrogen, it still has much more than other common materials, so it can absorb a comparatively large amount of heat energy with little heating.

Good for cooling, bad for the energy bill for a hot bath.

For the same cooling effect of one litre of water you theoretically need about 4m3 of air, while the water splashes comfortably, the air has to be blown at high speed over heat sinks. In reality, the amount of air is even greater because the heat transfer is less efficient.

In order to achieve optimum heat dissipation, special heat exchangers are used on all relevant components (GPUs, CPUs, memory, voltage regulators) and in this way the heat is transferred directly into a liquid, which in turn transfers the energy into water in a heat exchanger.

The great thing about this is that you now have “hot” water at ~60-70 degrees, which can be put to good use, e.g. for heating or hot water. If this is not possible, the hot water can be cooled again with a cooling tower on the roof or other heat exchangers without using a lot of energy so that it can be used again for the servers. In contrast to air cooling, which requires intake air at around 20 degrees, the water can return at around 40 degrees – so there is no need for energy-hungry chillers even in summer.

Many data centres in Europe are stuck in the 90s, rack power is often 5kW and “liquid cooling” is a foreign word.

You can’t run a GPU server there – you won’t get far with 5kW. We don’t have a solution for that, it’s up to the data centre operator. But there is a solution for the cooling issue: on the one hand, modern GPUs with air cooling have a reduced TDP value (unfortunately, less energy also means less computing power for the same purchase price) and on the other hand, as mentioned above, the air movement can only be achieved through high energy consumption by the fans.

Our side-by-side rack contains a large heat exchanger that is operated between 2 GPU racks, so two “Direct Liquid Cooled” racks with 100kW power each can be optimally cooled using this “side-by-side” rack, you have the full GPU power and overall less power consumption, no conversion is required in the data centre, the thermal energy is released into the room as with servers, only more efficiently.