Scientists from Nanyang Technological University, Singapore (NTU Singapore) have invented a more sustainable and green method for cooling down servers in data centres, potentially reducing up to 26 per cent in both energy costs and carbon footprint.
Currently, data centres in Singapore account for seven per cent of the nation’s total electricity consumption.
With demand for cloud computing increasing, it is critical to find a sustainable solution that reduces energy consumption and carbon footprint of data centres.
In a data centre, the hottest component in a server is the CPU – central processing unit – which requires a dedicated air-cooled heatsink for heat dissipation.
When servers are stacked together in a rack vertically, they produce a substantial amount of heat, so cold air is required for cooling.
The need for cooling is the reason why data centres are so energy intensive and require air conditioning systems to lower the air temperature.
In comparison, this new method developed by NTU scientists uses a special spray of non-conductive fluids to cool the CPU directly without a heatsink, utilising a combination of highly efficient heat removal mechanisms such as evaporation and boiling.
The gases and excess fluids are then collected in an enclosed system, condensed into liquid at tropical ambient temperatures (around 30 degrees Celsius) and recirculated back into the system to be reused.
More importantly, spray cooling has 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.
Based on the power consumed by the servers in a rack (known as rack density), the resulting waste heat generated is estimated to be around 7kW per cubic metre in conventional air-cooled racks.
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 per cubic metre.
If spray cooling is adopted industrially, it can 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 per cent when compared to conventional data centres that use air-cooling systems, a significant advantage for land scarce countries like Singapore.
Leader of the project, associate professor Wong Teck Neng from NTU’s School of Mechanical and Aerospace Engineering, said the main benefits of their new method are its high energy efficiency and targeted approach.
“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,” he said.
“The inspiration for our innovation is simple. If there is a fire breaking out on a piece of wood, we are taught to point the fire extinguisher at the base of the fire to put it out, not spray at the flames or around the fire to cool it down, since the fire will continue to burn at the source.
“Similarly, why are we spending an immense amount of energy cooling down the air around the heat source, when we should be cooling it directly?”
Neng said this targeted approach is smarter, 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 18 degrees Celsius, which accounts for about 40 per cent of its total energy usage.
With spray cooling, CPUs can maintain their optimal temperature at about 55 degrees Celsius 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. This can result in significant savings in cooling energy when compared to traditional air-cooled data centres which are usually at 1.8 PUE.