Market-leading data slurper Facebook is hoping to save energy and water by using indirect evaporative cooling in its data centres.
Zuck & Co's bit barns typically employ direct evaporative cooling processes to prevent racks overheating, but it isn't feasible in some climates because atmospheric air varies in temperature and humidity. Both these factors affect the evaporation rate from a body of water.
With this is mind, The Social Network™ developed the StatePoint Liquid Cooling (SPLC) system with Nortek Air Solutions. It can be used in places and situations where direct cooling is not the best option.
When water evaporates, it cools: direct evaporative cooling removes heat from a data centre by evaporating water within the airstream. Indirect evaporative cooling accomplishes the same except the water does not come into direct contact with the conditioned air – ideal for already humid environments.
The SPLC lowers the temperature of water by employing a liquid-to-air energy exchanger using a membrane to separate the water and the air yet permit evaporation.
SPLC Membrane scheme (Image: Nortek Air Solutions)
The membrane is thin, hydrophobic, and scale resistant. The SPLC system outputs cooled water, which removes heat from the data centre's air.
StatePoint Technology Unit showing intake and exhaust dampers, filters, coils, fans, and the membrane exchanger (Image: Nortek Air Solutions)
The system operates in one of three modes to optimise water and power consumption, depending on outside temperature and humidity levels.
- Normal mode: when outside air temperatures are low, the SPLC uses outside air to produce cold water
- Adiabatic mode: when outside air temperatures rise, the SPLC system uses a heat exchanger to cool the warm outside air before it goes into the recovery coil to produce cold water
- Super-evaporative mode: in hot and humid weather, the SPLC operates with a pre-cooling coil to cool the outside air which is then used to produce cold water
The normal mode is the most energy and water efficient.
The schematic below demonstrates the SPLC cooling scheme for a data centre. The SPLC units are deployed on the rooftop.
SPLC rooftop deployment scheme. SPLC units produce cold water, which is supplied to the fan-coil wall (FCW) unit. These FCW units use the cold water to cool the servers. The resulting hot water is returned to SPLC units for cooling and recycled through the system
The SPLC unit has integrated supply water temperature and distribution pumping control, and is claimed to simplify data centre piping requirements. It can be connected to a range of different data centre cooling delivery systems; fan-coil walls, air handlers, in-row coolers, rear-door heat exchangers, and chip cooling.
Compared to other indirect cooling schemes, the SPLC uses less water and is more energy-efficient, according to Facebook, because it uses air to cool water instead of using water to cool air, even when operating in adiabatic and the super-evaporative modes.
The SPLC system is forecast by Facebook to reduce water usage by more than 20 per cent for data centres in hot and humid climates and by almost 90 per cent in cooler climates.
Facebook would have us believe in its green credentials, even though it pisses on your personal data environment. ®