Leak-Free Liquid Cooled Heat Sinks
CoolestDC | Case Study
The Future of Sustainable Data Centers - Leak-free liquid cooled heat sinks reduce carbon footprint and energy consumption
CoolestDC launches highly customizable, leak free in-server liquid cooling solutions to accelerate green data center initiatives with EOS additive manufacturing technologies.
The data center sector has boomed considerably over the past few years thanks to the increasing demand for cloud applications, digitization, IoT devices and 4G and 5G edge computing. According to an IDC* forecast, the quantity of global data will reach 175 zettabytes by 2025. In addition, total investment in data centers is expected to increase from $ 244.74 billion in 2019 to $ 432.14 billion in 2025, at a compound annual growth rate (CAGR) of 9.9 %. But as the growth of data continues, the question of the impact of data centers on the environment also needs to be addressed. Decarbonization is a key factor, as it brings sustainability goals and renewable energy into focus. One of the main objectives is to build more sustainable data center operations with energy efficient cooling solutions. Direct-to-chip liquid cooling could become the primary cooling method, driven by rack density, electricity costs and sustainability activities.
Challenge
To find an alternative to brazed and assembled cold plates that minimize the risk of leakage in direct-to-chip liquid cooling applications, in order to shrink rack density, reduce electricity cost and improve sustainability.
Air-cooled heat sinks currently dominate the sector, as data center operators are more familiar with chilled water and direct expansion systems. However, there is a limit to power consumption and carbon emissions in terms of the total energy efficiency and potential savings with air-cooled heat sinks, as a large portion of power consumption in current air-cooled data centers is due to air chillers. Given the more stringent sustainability targets and introduction of the new carbon tax for data center owners, direct liquid cooling may eventually become the primary cooling technique employed by data center operators. At present, direct liquid cooling is a niche activity and only applicable to high-performance servers with special infrastructures or a warranty in place. One of the main barriers to the entry of liquid cooling heat sinks is the potential risk of leakage, which may result in damage to the servers. Hyperscale DC owners, operators and server OEMs are currently all exploring the possibilities of deploying leak-free direct liquid cooling solutions to meet the demands for higher rack density while improving total energy efficiency.
"Temasek Foundation is happy to support CoolestDC to develop a disruptive, energy-efficient, and low water consumption solution to cool data centers. As the solution can be deployed both in brownfield as well as greenfield applications, the innovation can be a blueprint for a sustainable data center operation enabling cities like Singapore to be a green data center hub.“
Lim Hock Chuan, Chief Executive Officer – Temasek Foundation
Solution
Using EOS DMLS technology together with a high-density EOS Copper CuCP process, we developed and built unibody leakless, gasket less and joint-free cold plates to create fully leak-free, in-server, liquid cooling solutions.
State of the art additive manufacturing (AM) technology from EOS enabled CoolestDC to design and build an integrated, leak-free unibody liquid cooled heat sink to address the concerns and requirements of industry. Using the AMCM M 290 1kW system together with the validated EOS Copper CuCP process (based on commercially pure copper), we manufactured a highly dense copper heat sink that can withstand water pressures of 6 bar and over, with no joints, assemblies or gaskets. Moreover, the AM process is versatile and able to produce thin-walled internal structures (0.2 mm and over), while the patented oblique fins are printed using an optimized
process to maintain their accuracy and high-resolution features. This all-in-one build not only addresses and eliminates leakage concerns which might otherwise lead to catastrophic failures of the server boards, but also drastically reduces manufacturing complexities (with no assembly and brazing required), thus increasing the part’s service life.
"In Singapore, we’re testing liquid cooling technology as an example. We’ve done a pilot with a local company called CoolestDC, part of National University of Singapore, who are using servers that are machine learning or AI related to lower their power densities. Using CoolestDC’s liquid and two-phase cooling solutions can result in up to 30 % savings in the total energy consumption for data centers. Related to this will be the significant reductions in carbon dioxide emissions and water consumption“
Mark Smith, Managing Director – Asia Pacific at Digital Realty
Results
- Leak-free unibody cold plate that can withstand water pressures of 6 bar and above.
- Reduction in CAPEX investment as there are zero tooling costs for different server boards.
- Freedom to design and fabricate mass customized plate thicknesses, fin densities, and locations.
CoolestDC’s unibody AM cold plate was tested against industry leading air-cooled heat sinks at a fully operational colocator facility belonging to Digital Realty. The findings were:
- Reduction of CPU die and core temperatures by 10 °C (Fig 1)
- Significant reduction in operating temperature of GPU by almost 50 % (Fig 2)
- Ability of GPU to run at full load at 40 % higher clock speeds, with no throttling (Fig 2)
- PUE reduced to 1.2 (calculated)
Figure 1 shows the benchmarking results of the AM liquid-cooled CPU cold plate (AM) against its air-cooled (AC) counterpart measured in terms of the CPU die and core temperatures. The effect of the AM cold plate was to reduce the CPU die and core temperatures by 9.6 °C to 14.9 °C and by 8.1 °C to 12.4 °C, respectively. Maximum temperature reductions occurred at full load conditions, at which point the air-cooled heat sink struggled to dissipate the heat generated.
Figure 2 shows the GPU of an air-cooled server operating at full load at its threshold temperature of 90 °C. This contributed to thermal throttling, in which a safety feature in the GPU reduced its performance (measured in terms of clock speed, MHz) to avoid overheating and potentially damaging the hardware. On the other hand, the liquid-cooled GPU was able to maintain its temperature at 40 °C, thus comfortably operating at its peak performance at 100 % load.
Advantages of liquid cooled heat sink vs. traditional air cooled heat sink
| Parameter | Air cooled heat sink 1U server |
Liquid cooled heat sink (AM unibody) |
|---|---|---|
| CPU Tdie at full load | 90 °C throttled | 46.0 °C |
| GPU performance at full load | 1 750 MHz throttled 5.8 TFlops throttled |
2 450 MHz 8.1 TFlops |
| PUE | 1.4 | 1.23 achievable with LCCRD |
| Leakage concern | - | Leak-free (w/o joints and gaskets) |
Benefits to data center providers and stakeholders
Based on the above GPU performance, a fully populated liquid-cooled rack with 25 1U servers (HPC servers with four GPUs) produces 810 TFlops. To achieve the same performance would require 30 air-cooled servers, which would have to be separated into two racks of 15 servers each, as it would otherwise exceed the maximum capacity of 15 kW of an air-cooled rack. We therefore estimate the value propositions and total cost savings for end customers as follows:
Estimated TCO (cost saving) for data center customer use cases and scenarios
Al or Big Data Analytic on
2 * 42U Rack Systems
1. EE =$42,071
2. Carbon =$7,853
3. Rack Rental =$24,000
4. Est. Total Cost Saving =$73,924
Online Gaming on
100 * 42U Rack Systems
1. EE =$1,051,800
2. Carbon =$196,331
3. Rack Rental =$1,200,000
4. Est. Total Cost Saving =$2,448,131
Blockchain Platform on
500 * 42U Rack Systems
1. EE =$5,259,000
2. Carbon =$981,655
3. Rack Rental =$6,000,000
4. Est. Total Cost Saving =$12,240,655
In collaboration with the EOS Additive Minds team, CoolestDC has developed an AM-centric design to further optimize product performance and reduce manufacturing costs by over 50 %. We are now also exploring a digitized workflow that will better support and accelerate the mass customization of cold plates for different customer requirements. Using AM, no tooling costs were incurred for mass-customized cold plates and no minimum order quantity is required for customers. With traditional manufacturing (machining, wire EDM and brazing, etc.), there is a minimum setup cost of around 3K for each new CPU and GPU model. This AM solution is suitable for both greenfield and brownfield applications including edge computing. We envisage, that this next generation of design will be even more cost effective and efficient, which will lead to greater savings and performance gains for the end user.
Short Company Profile:
CoolestDC is a Singapore-based deep tech start-up with considerable expertise in the thermal management of high heat-flux electronics and the ability to offer design services using Oblique Fin high-efficiency liquid cooling technology. CoolestDC currently collaborates with the EOS Singapore Additive Minds team in providing innovative additively manufactured cooling solutions to help drive sustainability in data centers. Further information: https://www.coolestdc.com
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