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Spray cooling could reduce data centre cooling costs

Leader of the project NTU Associate Professor Wong Teck Neng (front left) and his team at Singapore’s Nanyang Technological University

SINGAPORE: Scientists in Singapore claim to have invented a more sustainable and green method for cooling data centre servers, potentially reducing energy costs by up to 26%.

This new method, developed by a team at Singapore’s Nanyang Technological University (NTU), uses a special spray of non-conductive fluids to cool the servers CPU directly without a heatsink. The gases and excess fluids are then collected in an enclosed system, condensed into liquid at tropical ambient temperatures (around 30ºC) and recirculated back into the system to be reused.

More importantly, spray cooling is said to have the potential to carry away more heat than air cooling, which will allow for CPUs to run faster and perform better than today’s speeds which are limited by air cooling, since faster speeds will lead to higher temperatures.

Currently, data centres in Singapore account for 7% of the nation’s total electricity consumption. The power consumed by the servers in  conventional air-cooled racks currently produce around 7kW/m3 of waste heat. In comparison, the spray-cooling prototype has shown to be able to dissipate significantly more heat, capable of handling rack densities as high as 23kW/m3

It is claimed that if spray cooling was adopted industrially, it could allow for higher computing power servers to be packed into a smaller space than current data centres. The team estimates that it could translate into space savings of 30% when compared to conventional data centres that use air cooling systems. 

“Instead of cooling the entire data centre conventionally, we designed special sprays to aim directly at the CPU, the critical component which is the key source of heat in a data centre,” said associate professor Wong Teck Neng from NTU’s School of Mechanical and Aerospace Engineering, who is also the assistant chair (faculty) at the school. 

He explained that their targeted approach is a smarter approach, especially in tropical environments, where the high humidity and heat can put a significant strain on traditional air cooling systems. 

For instance, a conventional data centre has to be cooled down to about 18ºC, which accounts for about 40% of its total energy usage. In contrast, using spray cooling, CPUs can maintain their optimal temperature at about 55ºC without the need for energy-intensive air conditioning units. 

Power usage effectiveness (PUE) – ratio of total amount of power used by the data centre versus the actual power delivered to the servers – of the new prototype can go as low as 1.08. 

Studies by the team also showed that based on a data centre IT load of 1MW, their spray cooled system can save up to 1550 tons of CO2 emission annually when compared to conventional air cooling systems. 

The prototype system consists of an enclosed spray-cooled server rack capable of operating near atmospheric pressure, a water pump, sprays with multiple nozzles over each CPU, a collection system to collect the vaporised liquid, and an energy-efficient room-temperature condenser to convert the gases back into liquid again. Unlike conventional air-conditioning systems, no chiller system is required.

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