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Economizer Based Server Liquid Cooling to Enable Significant Data Center Energy Savings
Keywords: server liquid cooling, data center energy efficiency, advanced thermal interfaces
Information Technology (IT) data centers consume a large amount of electricity in the US and world-wide. Cooling has been found to contribute a large portion of this energy use. In addition to significant energy usage, traditional data center cooling also results in refrigerant and make up water consumption. Thus, understanding and improving the thermal management and energy efficiency of data center cooling systems is of growing importance from a cost and sustainability perspective. The proposed IMAPS ATW presentation will summarize the progress on a Department of Energy cost shared grant (2010-2012) with IBM Research and IBM Systems & Technology groups to develop highly energy efficient, warm liquid cooled servers for use in chiller-less data centers that would save significant data center energy use and reduce data center refrigerant and make up water usage. The technologies being developed as part of this project include liquid cooling hardware for high volume servers, advanced thermal interface materials, and economizer based facility level cooling systems that reject the IT heat load directly to the outside ambient air. Project Description The objective of this project is to reduce the cooling energy to 5% or less of total data center energy. The project has focused on the development of two complementary novel technologies that can radically reduce the energy consumption of data centers by using direct cooling from the outside ambient environment and eliminating refrigeration equipment Firstly, a server compatible Liquid Metal Thermal Interface (LMTI) [1] was developed to improve the thermal conduction path of the hot server components to the data center ambient cooling. This liquid metal thermal interface has a thermal conductivity an order of magnitude better than currently deployed state of the art materials. When integrated directly between a bare die and a water cooled heat sink this technology will achieve a significant improvement in thermal conduction and enable the computer devices to operate in a higher ambient temperature environment. Secondly, a dual enclosure air/liquid cooling system was developed to allow direct cooling from the outside ambient environment [2]. This Dual Enclosure Liquid Cooling (DELC) system uses recirculated air and water which are cooled only by dry heat exchange with the outside ambient air. The DELC also comprises sensors and servo control algorithms that adjust the cooling component operating parameters based upon the server rack heat load and the outdoor air temperature to reduce the cooling component energy usage. The use of the DELC system eliminates the data center refrigeration chiller plant as well as several other cooling components, thus allowing for as much as 85% reduction in the cooling energy cost. The water, cooled only by heat exchange with the outside ambient environment, enters the DELC at a temperature above the outdoor air temperature and warms up by extracting heat from the higher temperature server components. To maximize the energy impact, this project focuses on the largest segment of the server market which is the Volume server. The processor power for Volume servers is currently in the range of 60-130 watts and has been increasing. The solutions to be demonstrated in this project are applicable to much higher power processors > 200W and can be applied to today's Mid-range and High-end servers, allowing extendibility to future server requirements. Thus far, water cooling has been limited to the use of chilled water for High-End systems due to cost of infrastructure, implementation and energy required to provide refrigeration for chilled water. The LMTI and DELC technologies advance the state of the art of water cooling by enabling the use of ambient cooled water to provide a cost effective solution for commercial Volume, Mid-range and High-End systems where the largest segment will use processor power of 90 watts or greater and node power of 200 watts or above. REFERENCES [1] Y.Martin and T.Van Kessel, 2007, “High Performance Liquid Metal Thermal Interface for Large Volume Production”, IMAPS (Int.Microelectronics And PackagingSoc.) Thermal and Power Management, San Jose CA, Nov.11-15. [2] R. Chu, M. Iyengar, V. Kamath, and R. Schmidt, 2010, “Energy Efficient Apparatus and Method for Cooling an Electronics Rack”, Patent US 7791882 B2.
Madhusudan Iyengar, Senior Engineer
IBM Corporation
Poughkeepsie, NY

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