Located south of Paris, the Data4 campus hosts the data of major CAC 40 companies. Among the nine data centres spread over 111 hectares, is DC05. This new-generation data center, in service since the end of 2017, has a single facade, clad with blocks capable of drawing in external oxygen. "Once filtered, this air at room temperature is used to cool the core of the building, or the temperature of some components can easily rise to 60°C. This free cooling system replaces the frozen water reserves and large mechanical cold cabinets used in older data centres," explains Jérôme Totel, site manager.
Free cooling is in vogue and is becoming increasingly popular, mainly for economic reasons. Indeed, data centers consume nearly 10% of the world's electricity. "And nearly half of this energy is used to operate cooling systems," explains Guilhem Cottet, General Delegate of France Datacenter. Today, the temperature range of air sent to server rooms is much higher than it was ten years ago. Indeed, international guidelines recommend between 20 and 27°C.
However, "cooling a data center is a real science," says Jean-Michel Rodriguez, Chief Technology Officer at IBM. The ambient temperatures and humidity in the northern European countries naturally ensure good cooling throughout the year, making it easier to use free cooling. However, this is not the case with a more Mediterranean climate since this system can only operate for part of the year. Hosting companies therefore often rely on more modest installations such as simple air conditioning coupled with "cold aisles". "Each year brings its share of new products. We are in a state of constant optimization," confirms François Salomon, Schneider's free cooling specialist.
This is the case, for example, of Facebook, which last June revealed a system combining free cooling and water, or Lenovo, which relies on liquid cooling. 2CRSI, a Strasbourg-based company, offers a shared cooling system. Many researchers are currently working on algorithms that can reduce server consumption. Although the energy efficiency indicator for data centres has improved significantly in recent years, some experts are sounding the alarm bell. "Calculation and energy needs will increase exponentially. To develop artificial intelligence, optimizing cooling will not be enough. So much so that we will have to rethink the design of our data centers," warns Pierre Perrot of CryoConcept.
This observation has led engineers to develop diametrically different technologies such as immersion. Asperitas now immerses its servers in oil. "It is a non-conductive and non-corrosive liquid that absorbs up to 1,500 times more heat than air," says Pierre Batsch, head of the company's development in France. Thus there is no need for air conditioning, false ceilings, cold aisles, etc. While Alibaba has already announced a similar project for some of its servers, other players such as "cryptomone mining" factories or the financial world are also interested in this solution.
Microsoft has decided to immerse part of its infrastructure in the ocean. "Water is 800 times denser than air. When you touch it, you are in contact with many molecules, which means you can transfer heat faster and more efficiently," explains Ben Cutler, project manager at Microsoft. But this initiative is met with some criticism: "Will the heat released have an impact on the marine ecosystem? Wouldn't it be better to reuse it?," persimmates an expert. These remarks will not discourage Microsoft, which has not finished making waves.
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Source : L'Express