How increasing computing density and reduce energy consumption of your air-cooled datacenter facility thanks to Calyos loop heat pipe ?

How increasing computing density and reduce energy consumption of your air-cooled datacenter facility thanks to Calyos loop heat pipe ?

Thomas Le Clerc – October 18th 2018

Nowadays, the datacenter market is one of the world’s fastest growing market due to data volume increase and the need of data management. This trend has a direct impact on datacenter infrastructures as a new paradigm happen: Densifying computing architectures to limit datacenter footprint and reduce energy consumption needed to operate.

As a result, electronic component’s power levels are constantly increasing while their footprint remain equivalent. Server boards are in parallel integrating more electronic components to achieve the best computing performance while chassis are getting more intensely populated. To deal with these requirements, traditional air-cooling technologies are facing more and more restrictions and necessitate additional energy (air flow, colder inlet temperature) to keep electronic components under their thermal specifications (~75°C). Sometimes, this additional energy is even insufficient to achieve the specification.

Thus, server manufacturers and end-users are confronted to the necessity to use advanced cooling technologies as a computing performance enabler. Three options are mainly given:

  1. Keep existing air-cooled facility and implement advanced cooling systems (close loop) into each server to improve local thermal performance and avoid infrastructure modification

  2. Switch facility to direct water cooling

  3. Switch facility to immersion cooling

Focusing on option 1, two major cooling technologies compete in offering high thermal performance at system level: Liquid Assisted Air Cooling (LAAC) and Loop Heat Pipe (LHP). Regarding the LHP, its intrinsic characteristics bring unique competitive advantages for system level cooling products:

  • Thermal performance competing with LAAC

  • Extreme reliability avoiding active components to operate the loop (i.e. working principles below) and using industrial assembly processes and material (no permeation, no leakage)

Calyos Loop Heat Pipe.png

  • Good safety running with dielectric fluid

  • Easy mechanical integration thanks custom tube routing (thin flexible or rigid tube)

  • Extensive customization opportunities to match specific requirements

    • Inner structure (vaporization & capillary pumping)

    • Heat exchanger design

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Such technology can allow datacenter facilities to keep their existing air-cooled infrastructure while using more performant electronic components and saving energy. As a concrete case study, a performance benchmarking has been achieved between a LHP and a vapor chamber heatsink to cool a 1U dual socket chassis with following specifications:

  • TDP: 2x205W

  • Fan reference: 40x28

  • Ambient temperature: 20°C

loop heat pipe Calyos.png
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Main output from this test is the opportunity to operate a lower fan speed and still achieve better thermal results with the LHP. This generates direct energy savings, estimated to be 50W per chassis meaning 0,05KW for 1U. Transferring this calculation to yearly savings we obtain the following table according to use rate and electricity price.

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Extrapolating these savings to rack level (42U), we obtain the following figures


In addition to it, supplementary energy savings can be achieved thanks to air conditioning with the opportunity to rise-up the room temperature. Having a look at the benchmarking detailed above, we observe that room temperature was 20°C while CPU temperature reached 68°C with the Loop Heat Pipe. Indeed, room temperature can be amplified by few degrees while the CPU will still be under its thermal specifications (~75°C). This room temperature increase will have a positive impact on air conditioning’s energy consumption. Industry experts estimate that each additional degree within the datacenter room can generate up to several percent energy reduction from air conditioning. In the meantime, reducing the temperature delta between indoor and outdoor can offer the opportunity to use lower powered air conditioning and optimize capital expenses.   

As a conclusion, we can state that Loop Heat Pipe is obviously more performant than traditional air-cooling systems and compete with LAAC being more reliable. Loop Heat Pipe system offers unique opportunity to handle high power levels and densities remaining air cooled. In the meantime, air-cooled facilities can lower their energy consumption while benefiting from more computing capacity.

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