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Data center cooling technology reduces the summertime air-conditioning power consumption by half

Featured Technologies

June 29, 2018

It is expected that we can reduce CO₂ emissions in every industry, transportation, and consumer life by using IT. Data centers provide the cloud services that handle the information that drives such activities and is one element of infrastructure along with electricity, gas, and waterworks. In recent years, the development of IoT and the increased demand of virtual currency mining have led to data centers accounting for 0.5% of the global energy consumption. This proportion is predicted to only expand toward the future, and it is estimated that by 2025 the data centers' power consumption will outweigh that of electric vehicles.

Around 30% to 40% of the power used at data centers is consumed by air-conditioning systems for cooling IT equipment. Enormous amounts of power are consumed in hot climates and during summertime. To alleviate this, data centers have been established in cooler climates and other mitigating approaches were taken in terms of installation and establishment, but the increased distance between the data center and user has created inconvenience.

In response to this, NEC developed a technology that can reduce the power consumption of air-conditioning systems at data centers in high temperature environments. This technology reduces the power drain from air conditioning at data centers in hot climates, which achieves both convenience and lower operating costs.

Features of the new technology

  1. Reduces power consumed by fans and compressors by means of localized air conditioning of the server racks
    The air-conditioning power consumption ratio of compressors for cooling and fans for ventilating heat from IT equipment to outdoors is roughly 6 to 4. Conventionally, air circulation in the server room replaced warm air (heat exhaust from IT equipment) with cool air. However, as you can imagine from the fact that air is used as insulator, it is not an efficient medium for carrying heat.
    Thus, if a refrigerant 100 times more efficient can be circulated close to the IT equipment―the heat source―fan power consumption can be reduced. Additionally, the power consumption by compressors can also be curtailed by heat exchanging with the refrigerant before the temperature of IT equipment drops from heat dissipation into the server room.
  2. Flow technology with low pressure drop enables application of low-pressure refrigerant to air-conditioning systems
    However, to circulate the refrigerant throughout the server room, the refrigerant must be depressurized to about 1/10 of the refrigerant pressure currently adopted for air conditioning to meet the safety requirement. Low-pressure refrigerants are eco-friendly, but the latent heat―material value of heat transfer―is extremely small, in which case a larger volumetric flow rate is required in the piping. This means that, any area of high resistance in the flow of refrigerant, such as a narrow part in the piping, can increase the power consumption of the compressor. This creates the problem of the piping design being difficult. This also results in the pipe diameter and compressor having to be larger, which is the reason why low-pressure refrigerants have not been used for air conditioning.
    Therefore, NEC implemented a piping design that minimizes the flow resistance by not having any sharps bends or steep expansion or shrinkage of pipe diameter. We also used multiple narrow pipes to build flow paths like expressways where the refrigerant can smoothly join and split. This can both lower the flow resistance and make piping installation easier.

The cooling system was introduced at a data center in southern India for experimenting. Under a temperature of 35℃, we introduced the cooling system to a 7.5 kW rack―double the heat generation of an average rack―and compared the result with the existing air-conditioning system. As a result, we demonstrated that the coefficient of performance (COP, quotient of cooling performance divided by air-conditioning power consumption), an indicator of air-conditioning efficiency is 3.2 to the 1.6 obtained from the existing air-conditioning system.

Today, NEC is furthering improvement aimed at productizing this cooling system. NEC will contribute to the realization of a sustainable society by continuing to provide technologies that streamline data center operations.