Facebook has created a new kind of liquid cooling system for the data centre, using water rather than air to cool facilities, so the company can build data centres in difficult climates.
The new evaporative cooling system, StatePoint Liquid Cooling (SPLC), is more efficient than previous indirect cooling systems. It also allows for deployment in parts of the world where data centres with traditional direct cooling could not operate.
Areas, for instance, with less than ideal environmental conditions such as high levels of dust, pollution or extreme humidity, will now be accessible. Facebook says that it will continue using direct cooling in most of its sites. This new technology offers new options for the company, however.
In other liquid cooling systems, water is used to cool air, which is used to cool the data centre. However, with the SPLC system, air is used to cool water and the water itself becomes the cooling agent, resulting in a far more energy- and water- efficient system that can be used in a variety of external environments.
Facebook’s liquid cooling news comes at the same time as Microsoft sinks a self-sustaining data centre into the sea off the Orkney Isles to test energy-efficiency.
Liquid cooling – the details
The SPLC system, developed with and patented by Nortek, is based on a liquid-to-air energy exchanger. Water evaporates through a layer of membrane that is thin, hydrophobic, and scale-resistant. The result is cold water, which is used to keep the data centre and servers at an optimal temperature.
The membrane itself protects the water and air from cross-contamination, and because it is resilient to scale formation and poor water quality, allows the system to operate in a high-pollution environment without damaging circuits. The SPLC system is also constructed to keep circuits clear, reducing maintenance and improving the lifespan of system components.
The new liquid cooling system can operate in three distinct modes: adiabatic, for warm exterior temperatures; super-evaporative, for hot and humid environments; and energy-efficient, for use in cool environments.
In a cool external environment, the system’s most water- and energy-efficient mode circulates air through the membrane exchanger to produce cool water. In a warm environment, adiabatic mode uses a heat exchanger that cools outside air before it is run through the recovery coil.
And in a hot, humid environment, the super-evaporative mode utilizes a separate, pre-cooling coil that cools outside air before it is processed.
While Facebook has not released specific efficiency results, in a blog post announcing the creation of the SPLC system, the company noted that its data centres have an overall power usage effectiveness (PUE) of 1.10; and noted that this new liquid cooling has a PUE that is ‘on par or better than the traditional direct evaporative system.’