Airside Economization Research Articles

The sustainability benefits of economization in data centers containing chilled water systems

This study provides the first known conservative estimates of reductions in carbon and water scarcity footprints when employing economization technologies in chilled water-based data centers (DCs) in the U.S. Specifically, a generic DC that employs a Computer Room Air Handling (CRAH)-based cooling system with a total IT load of 400 kW is computationally modeled at 925 locations in the U.S. with airside and/or water-side economization. The energy savings and environmental benefits are presented in terms of key DC performance metric reductions, including Carbon Usage Effectiveness (CUE) and Water Scarcity Usage Effectiveness (WSUE). The results suggest that implementing both water-side and airside economization schemes under conditions within the ASHRAE A1 Allowable envelope reduces the mean state-averaged PUE, WUE, CUE, and WSUE by 11%, 22%, 11%, and 15%, respectively. These results highlight the environmental benefits of economization technologies and provide guidance on economization strategies.

Simplified and Detailed Analysis of Data Center Particulate Contamination at Server and Room Level Using Computational Fluid Dynamics

Abstract Continuous rise in cloud computing and other web-based services propelled the data center proliferation seen over the past decade. Traditional data centers use vapor-compression-based cooling units that not only reduce energy efficiency but also increase operational and initial investment costs due to involved redundancies. Free air cooling and airside economization can substantially reduce the information technology equipment (ITE) cooling power consumption, which accounts for approximately 40% of energy consumption for a typical air-cooled data center. However, this cooling approach entails an inherent risk of exposing the ITE to harmful ultrafine particulate contaminants, thus, potentially reducing the equipment and component reliability. The present investigation attempts to quantify the effects of particulate contamination inside the data center equipment and ITE room using computational fluid dynamics (CFD). An analysis of the boundary conditions to be used was done by detailed modeling of ITE and the data center white space. Both two-dimensional and three-dimensional simulations were done for detailed analysis of particle transport within the server enclosure. An analysis of the effect of the primary pressure loss obstructions like heat sinks and dual inline memory modules inside the server was done to visualize the localized particle concentrations within the server. A room-level simulation was then conducted to identify the most vulnerable locations of particle concentration within the data center space. The results show that parameters such as higher velocities, heat sink cutouts, and higher aspect ratio features within the server tend to increase the particle concentration inside the servers.

Effects of Gaseous and Particulate Contaminants on Information Technology Equipment Reliability—A Review

Abstract Over the last decade, several hyper-scale data center companies such as Google, Facebook, and Microsoft have demonstrated the cost-saving capabilities of airside economization with direct/indirect heat exchangers by moving to chiller-less air-cooled data centers. Under pressure from data center owners, information technology equipment OEMs like Dell and IBM are developing information technology equipment that can withstand peak excursion temperature ratings of up to 45 °C, clearly outside the recommended envelope, and into ASHRAEs A4 allowable envelope. As popular and widespread as these cooling technologies are becoming, airside economization comes with its challenges. There is a risk of premature hardware failures or reliability degradation posed by uncontrolled fine particulate and gaseous contaminants in presence of temperature and humidity transients. This paper presents an in-depth review of the particulate and gaseous contamination-related challenges faced by the modern-day data center facilities that use airside economization. This review summarizes specific experimental and computational studies to characterize the airborne contaminants and associated failure modes and mechanisms. In addition, standard lab-based and in-situ test methods for measuring the corrosive effects of the particles and the corrosive gases, as the means of testing the robustness of the equipment against these contaminants, under different temperature and relative humidity conditions are also reviewed. It also outlines the cost-sensitive mitigation techniques like improved filtration strategies and methods that can be utilized for efficient implementation of airside economization.

Development of a Precise and Cost-Effective Technique to Measure Deliquescent Relative Humidity of Particulate Contaminants and Determination of the Operating Relative Humidity of a Data Center Utilizing Airside Economization

Abstract A remarkable amount of energy in data centers is consumed in eliminating the heat generated by the information technology (IT) equipment to maintain and ensure safe operating conditions and optimum performance. The installation of airside economizers (ASEs), while very energy efficient, bears the risk of particulate contamination in data centers, hence, deteriorating the reliability of IT equipment. When relative humidity (RH) in data centers exceeds the deliquescent relative humidity (DRH) of salts or accumulated particulate matter, it absorbs moisture, becomes wet, and subsequently leads to electrical short-circuiting because of degraded surface insulation resistance (SIR) between the closely spaced features on printed circuit boards (PCBs). Another concern with this type of failure is the absence of evidence that hinders the process of evaluation and rectification. Therefore, it is imperative to develop a practical test method to determine the DRH value of the accumulated particulate matter found on PCBs. This research is a first attempt to develop an experimental technique to measure the DRH of dust particles by logging the leakage current versus RH% for the particulate matter dispensed on an interdigitated comb coupon. To validate this methodology, the DRH of pure salts like MgCl2, NH4NO3, and NaCl is determined, and their results are then compared with their published values. This methodology was therefore implemented to help lay a modus operandi of establishing the limiting value or an effective relative humidity envelope to be maintained at a real-world data center facility situated in Dallas industrial area for its continuous and reliable operation.

Thermal Control Strategies for Reliable and Energy-Efficient Data Centers

Two self-developed control schemes, ON/OFF and supervisory control and data acquisition (SCADA), were applied on a hybrid evaporative and direct expansion (DX)-based model data center cooling system to assess the impact of controls on reliability and energy efficiency. These control schemes can be applied independently or collectively, thereby saving the energy spent on mechanical refrigeration by using airside economization and/or evaporative cooling. Various combinations of system-level controls and component-level controls are compared to a baseline no-controls case. The results show that reliability is consistently met by employing only sophisticated component-level controls. However, the recommended conditions are met approximately 50% of the simulated time by employing system-level controls only (i.e., SCADA) but with a reduction in data center cooling system power usage effectiveness (PUE) values from 3.76 to 1.42. Moreover, the recommended conditions are met at all averaged times with an even lower cooling system PUE of 1.13 by combining system-level controls only (SCADA and ON/OFF controls). Thus, the study introduces a simple method to compare control schemes for reliable and energy-efficient data center operation. The work also highlights a potential source of capital expenses and operating expenses savings for data center owners by switching from expensive built-in component-based controls to inexpensive, yet effective, system-based controls that can easily be imbedded into existing data center infrastructure systems management.

Identification and Characterization of Particulate Contaminants Found at a Data Center Using Airside Economization

Contamination due to the use of airside economizer has become a major issue that cost companies revenue. This issue will continue to rise as server components become smaller, densely packed, and as companies move into more polluted environments. Contaminants with small particles less than 10 μm are not noticeable; yet, these particles are most likely to get to areas where they can cause damage. Dust from different sources and suspended in air settles on surfaces of electrical components. The dust mainly contains two components: salts and metallic particles. The salts may be neutral or corrosive and the nature of the salt depends on the deliquescent humidity. For metallic particles, surveys are performed in various data centers in order to determine the limits in terms of weight per unit area and particle size distribution. It is necessary to first identify those contaminants that directly affect the information technology (IT) equipment in the data center. In this research, a real-world data center utilizing airside economization in an ANSI/ISA classified G2 environment was chosen for the study. Servers were removed and qualitative study of cumulative corrosion damage was carried out. The particulate contaminants were collected from different locations of a server and material characterization was performed using scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and Fourier transform infrared spectroscopy (FTIR). The analysis from these results helps to explain the impact of the contaminants on IT equipment reliability.

外気冷房を活用した次世代インターネットデータセンターの計画と性能検証 （第2報）施工時実験と運用性能検証

外気冷房を活用した次世代インターネットデータセンターの計画と性能検証 （第2報）施工時実験と運用性能検証

Energy and Exergy Analysis of Modular Data Centers

The data center industry focuses on initiatives to reduce its enormous energy consumption and to minimize its adverse environmental impact. Modular data centers provide considerable operational flexibility in that they are mobile and are manufactured using standard containers. This paper develops steady-state energy and exergy destruction models for modular data centers with the open-source EnergyPlus software package. Three different cooling approaches are examined: direct expansion (DX) cooling, evaporative cooling (direct evaporative cooling, DEC, in this study), and free air cooling (air-side economization in this study). This paper shows that for hot and arid climates like those in the southwestern U.S., augmenting DX cooling with evaporative and free air cooling can result in energy savings of up to 38% and 36%, respectively. This paper also applies exergy analysis to suggest that the Energy Reuse Effectiveness of the data center increases with decreasing ambient (outdoor) temperature and increasing server inlet–outlet temperature difference. Furthermore, simulations indicate that the use of passive cooling techniques (e.g., DEC and free air cooling) decrease data center heating, ventilation, and air-conditioning energy consumption, except in extremely hot and humid climates.

Qualitative Study of Cumulative Corrosion Damage of Information Technology Equipment in a Data Center Utilizing Air-Side Economizer Operating in Recommended and Expanded ASHRAE Envelope

Deployment of airside economizers (ASEs) in data centers is rapidly gaining acceptance to reduce cost of cooling energy by reducing hours of operation of computer room air conditioning (CRAC) units. Airside economization has associated risk of introducing gaseous and particulate contamination into data centers, thus degrading the reliability of information technology (IT) equipment. The challenge is to determine reliability degradation of IT equipment if operated in environmental conditions outside American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) recommended envelope with contamination severity levels higher than G1. This paper is a first attempt at addressing this challenge by studying the cumulative corrosion damage to IT equipment operated in an experimental modular data center (MDC) located in an industrial area with measured level of air contaminants in ISA severity level G2. This study serves several purposes including: correlating IT equipment reliability to levels of airborne corrosive contaminants and studying degree of reliability degradation when IT equipment is operated outside ASHRAE recommended envelope at a location with high levels of contaminants. Reliability degradation of servers exposed to outside air via an airside economizer was determined qualitatively by examining corrosion of components in these servers and comparing the results to corrosion of components in other similar servers that were stored in a space where airside economization was not used. In the 4 years of the modular data center's servers' operation, none of the servers failed. This observation highlights an opportunity to significantly save data center cooling energy by allowing IT equipment to operate outside the currently recommended and allowable ASHRAE envelopes and outside the ISA severity level G1.

外気冷房を活用した次世代インターネットデータセンターの計画と性能検証 （第1報）計画概要と性能予測

外気冷房を活用した次世代インターネットデータセンターの計画と性能検証 （第1報）計画概要と性能予測