Air-side Economizer Research Articles

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.

Potentiometric and economic analysis of using air and water-side economizers for data center cooling based on various weather conditions

In this study, a thermo-economic analysis was carried out for using Air-Side Economizer (ASE), Water-Side Economizer (WSE) and Combined Air or Water Economizer (CAWE) operation mode in order to cool a data center in ten cities of Iran with various weather conditions. The energy and cost saving potentials in Mashhad municipality's data center was studied as a case study and the findings were generalized for all cities during a year. The results showed that there are energy and cost savings potential by employing CAWE operation mode for all cities except coastal cities. In addition, the Power Usage Effectiveness (PUE) of the data center can be improved by a range from 10% to 12% using CAWE cooling mode for most cities. Finally, it was found that economic index of relative net present value (RNPV) for ASE, WSE and CAWE will be positive if their relative annual potential (RAP) are higher than 12%, 23% and 35%, respectively.

Towards the stand-alone operation of data centers with free cooling and optimally sized hybrid renewable power generation and energy storage

Recent increases in the global demand for IT services have increased the power consumption, total ownership costs and environmental footprint of data centers. Recent efforts to reduce these effects have focused on either their cooling systems, or their power systems. In this paper, we have developed an integrated approach to minimize the total power demand of data centers, whilst their reliance on power imported from the grid is minimized. First, the power demand of data center has been reduced utilizing various air-side economizer-based cooling systems. Since the effectiveness of economizers significantly depends on the local weather conditions, 42 stations in major cities across the world have been considered. A more than 80% reduction in total cooling power consumption is achieved by using the most appropriate air-side economizer at each location. Second, the reliance of data centers on power imported from the grid is minimized utilizing on-site hybrid renewable power generation and energy storage. The on-site renewable power generation and capacity factors have been calculated for 1 MW wind and solar renewable power plants to identify the location with the highest renewable power generation capability. The optimal size of a hybrid renewable power plant, and associated battery energy storage system, is also determined for each data center using linear programming to minimize total levelized costs. Finally, the optimal location for constructing and operating the most energy efficient, cost-effective and sustainable data center has been identified by calculating its level of independence from the power grid. It is found that the level of grid independence increases as we move away from the equator, for example more than 50% grid independence can be achieved at Regina station located in Canada.

Analysis of Air-Side Economizers in Terms of Cooling-Energy Performance in a Data Center Considering Exhaust Air Recirculation

Demand is soaring for data centers with advanced data-processing capabilities. In data centers with high-temperature information technology (IT) equipment, enormous cooling systems are operated year-round. To date, studies have aimed to improve the cooling efficiency of server-room units, but cooling-energy-consumption analysis considering the recirculation of exhaust air (EA) has not been researched to a sufficient degree. This study analyzed the cooling-energy saving effects considering the EA-recirculation and supply-air (SA)-temperature conditions when direct and indirect air-side economizers were applied to a data center in Korea. Thirteen case studies were conducted. The results showed that when the EA-recirculation ratio in the direct air-side economizer was 15%, its annual cooling-energy consumption increased by approximately 6.1% compared to the case with no recirculation. The indirect air-side economizer also exhibited an approximately 9% increase in cooling-energy consumption. On the other hand, when the SA temperature changed to 22 °C, the annual cooling-energy consumption of the direct and indirect air-side economizers decreased by approximately 67% and 55%, respectively, compared to a central chilled-water system. This indicates the importance of developing measures to prevent EA recirculation and of securing a wind path for the improvement of air-conditioning efficiency in data centers at the design stage.

Optimization of Enclosed Aisle Data Centers With Induced CRAH Bypass

Aisle containment systems reduce temperature nonuniformities in traditional air-cooled data centers and pave the way for higher cooling air temperature and more efficient operation of the cooling system and wider application of economizers. However, enclosing the aisle does not guarantee the lowest possible cooling infrastructure power. Enclosed air (EA) configurations require computer room air handler (CRAH) fans to provide the entire rack air flowthrough the perforated tiles, as well as the leakage flow that inherently exists in data centers. In this paper, we propose the installation of induction bypass (BP) fans beneath the cold aisle (CA) perforated tiles that draw air from the plenum, placing the latter under a slightly depressed pressure. In doing so, warm air from the hot aisle is drawn into the plenum, where it is mixed with a smaller amount of cold air from the CRAH. As a result, the CRAH fans operate at lower speeds and consume less power, but the air passing through the CRAH is cooled to a lower temperature so that the air supplied to the enclosed CA remains at or slightly below the server redline temperature (~27 °C). Detailed optimization based on hour-by-hour annual energy simulations for seven U.S. cities has shown that the proposed induced CRAH BP scheme can reduce combined chiller and air-moving power consumption substantially in EA data centers with or without an airside economizer.

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.

Economic analysis of data center cooling strategies

Advancements in information technology have led to an increasing demand for data centers (DCs), and the energy consumption of DCs has gained attention worldwide. Many researchers have attempted to develop efficient DC cooling systems to reduce the energy required for cooling DCs, however, there are limitations in identifying the effect of such systems from the economic perspective. Subsequently, project owners find it difficult to decide whether to apply these systems to their particular DCs. The present research aims to analyze the economic performance of seven cooling strategies developed by the combinations of widely used DC cooling systems. The economic performance of each strategy is estimated by the life cycle cost analysis technique, and the analysis results show that Strategy 5 (A2_M: air-side economizer and supplementary cooling by a mechanical system) yields economic benefits of 26.84% in comparison to the conventional cooling system. The proposed research methodology and obtained results are expected to aid project owners in making effective decisions regarding the selection of an appropriate cooling strategy from an economic perspective.

Impact of Air-side Economizer Control Considering Air Quality Index on Variable Air Volume System Performance

The objective of this study is to determine the effectiveness of a modified air-side economizer in improving indoor air quality (IAQ). An air-side economizer, which uses all outdoor air for cooling, affects the building’s IAQ depending on the outside air quality and can significantly affect the occupants’ health, leading to respiratory and heart disease. The Air Quality Index (AQI), developed by the US Environmental Protection Agency (US EPA), measures air contaminants that adversely affect human beings: PM10, PM2.5, SO2, NO2, O3, and CO. In this study, AQI is applied as a control for the operation of an air-side economizer. The simulation is analyzed, comparing the results between the differential enthalpy economizer and AQI?modified economizer. The results confirm that an AQI?modified economizer has a positive effect on IAQ. Compared to the operating differential enthalpy economizer, energy increase in an operating AQI?modified economizer is 0.65% in Shanghai and 0.8% in Seoul.

Energy conservation effects of a multi-stage outdoor air enabled cooling system in a data center

Energy consumption rates in a data center have increased year by year, and by this, the introduction of energy conserving cooling systems is rapidly emerging all over the world. In this study, a multi-stage outdoor air enabled (MOA) cooling system is proposed as the safer and more energy conserving system for a data center. An MOA cooling system is composed of the combination of water-side economizer, air-side economizer and mechanical cooling. Effects of an MOA cooling system are investigated by energy simulation from various viewpoints. The results show that the MOA cooling system can save cooling energy consumption rates by about 21%, and if combined with a special rack enclosure, by about 33%. Introducing outdoor air flow into the MOA cooling system decreases energy use to about half of that of the air-side economizer, and if combined with the rack enclosure, by about 9%. Thus, the concerns about particulate and gaseous contamination can be reduced. Continuous operating time of the humidifier drops to about 3 days, and if combined with the rack enclosure, to ‘0’ day. These results make it possible to remove the humidifier as part of the MOA cooling system.

A review of current status of free cooling in datacenters

In this study, an overview of current status of the free cooling technologies applicable for datacenters had been discussed, including airside economizers, waterside economizers, and heat pipe technology. By introducing the free cooling technologies, the compressor loading of refrigeration system can be partially or completely relieved. Utilization of airside or waterside free cooling relies strongly on the ambient conditions, yet either airside free cooling or waterside free cooling may be integrated with other systems such as absorption, solar system, adsorption, geothermal, evaporative cooling, and the like to extend its performance. On the other hand, thermosiphon heat exchangers and pulsating heat pipes feature unique characteristics to transfer heat at small temperature difference are quite promising for datacenter free cooling.

Energy, environmental and economical saving potential of data centers with various economizers across Australia

One of the main concerns in designing and operating data centers is the significant energy consumption of the cooling systems. Over the past years, developing and applying more energy efficient cooling strategies to reduce the environmental footprint and the total cost of ownership of data centers has drawn considerable attention. Cooling systems with air-side economizer cycle provide one of the most efficient methods. Their effectiveness in terms of energy and exergy, and the environmental and economical impact have been analyzed quantitatively in this research. Since the effectiveness highly depends on the local climate conditions, the analysis has been carried out for 23 locations across Australia. First, a detailed cooling load of the data center has been estimated by considering the workload and heat generation characteristics of the running IT equipment. Then, a comprehensive energy, exergy, environment and economic model of nine different air-side economizer cycles has been developed. Finally, the effectiveness and profitability of each economizer cycle has been compared to a conventional cooling system by evaluating the annual and monthly saving potential at each location. The air-side economizers can yield maximum savings of 84%, 80%, 75% and 85% in the annual cooling energy consumption, exergy destruction, CO2 emission and cooling costs, respectively. The power usage effectiveness (PUE) of the data centers can be also reduced from an average of 1.42 to 1.22. These savings and efficiency enhancements are highly correlated with the type and geographic location of the air-side economizers. In general, the saving potential increases as we move further south in Australia, due to more favorable climate conditions.

Free cooling potential of an airside economizer in Estonia

Nearly zero-energy buildings are designed to minimize energy consumption and the low energy demand is to be covered by local renewable energy resources. Free cooling is a method that utilizes low outdoor temperatures as a cooling medium to save energy in air-conditioning systems and is included in nearly zero-energy buildings renewable energy use system boundary. This article explores free cooling potential of direct airside economizer in Estonia. A detailed weather analysis was conducted to develop temperature bin data, which was used to calculate free cooling potential at different ventilation supply air temperatures. The results are presented as yearly, monthly, and hourly airside economizer cooling capacities. Free cooling potential in Estonia is high from October to April, during summer months, airside economizer operation is possible at higher ventilation supply air temperatures.

Experimental evaluation of anti-windup extremum seeking control for airside economizers

The performance of anti-windup extremum seeking control (ESC) as a model free online optimization strategy is evaluated by experimental studies for energy efficient operation of both chilled-water and direct-expansion airside economizers. For the chilled-water based system, the ESC takes the chilled-water valve control signal as the feedback, and controls the outdoor air damper (OAD) position to minimize the cooling coil load. For the direct-expansion system, the ESC takes the total electricity power consumption as the feedback, and controls the OAD position to minimize the power consumption. Experimental results verify the effectiveness of the ESC scheme for model-free operation without temperature and humidity measurements.

外気冷房を導入したデータセンターの性能評価に関する研究（第9報）空調条件の変動に伴うサーバ室内温熱環境把握のための実験

外気冷房を導入したデータセンターの性能評価に関する研究（第9報）空調条件の変動に伴うサーバ室内温熱環境把握のための実験

Data Center Energy and Cost Saving Evaluation

In data centers, about 40% of the total energy is consumed for cooling the IT equipment. Cooling costs are thus one of the major contributors to the total electricity bill of large data centers. This paper studies two factors affecting data center cooling energy consumption, namely air flow management and data center location selection. A unique rack layout with a vertically cooling air flow is proposed. Two cooling systems, computer room air conditioning (CRAC) cooling system and airside economizer (ASE), have been studied. Based on these two cooling systems, four cities have been selected from the worldwide data center locations. A number of energy efficiency metrics are explored for data center cooling, such as power usage effectiveness (PUE), coefficient of performance (COP) and chiller hours. By analyzing the effects of chiller hours and economizer hours, comparative economic results of cooling power consumption are provided in both systems. The results show that the cooling efficiency and operating costs vary significantly with different climate conditions, energy prices and cooling technologies. As climate condition is the major factor which affects the airside economizer, employing the airside economizer in the cold climate yields much lower energy consumption and operation costs.

Optimum supply air temperature ranges of various air-side economizers in a modular data center

In order to reduce data center cooling energy, ASHRAE Technical Committee 9.9 expanded thermal environmental ranges for data centers and recommended using the economizer, and it has reduced data center cooling energy successfully. The main purpose of this research is to establish an energy optimization process for the air-side economizer in a modular data center with respect to various parameters (supply air conditions, server thermal characteristics, cooling system configurations, and heat exchange effectiveness), and to determine optimum supply air ranges through simulation. The cooling energy simulation is conducted for three types of air-side economizers by changing the supply air temperature (SAT) and heat exchanger effectiveness at 16 locations in South Korea based on the three thermal environmental ranges. The simulation result shows that the lowest cooling energy consumption appears when the computer room air handler (CRAH) SAT is within 18–23 °C, and at higher SAT conditions, the cooling energy consumption increases, since chiller energy reduction is offset by the increase in CRAH fan energy.

Energy saving potential of various air-side economizers in a modular data center

With the recent development of the IT technology, the demand for data centers has significantly increased, and modular data centers have attracted considerable attention because of their excellent stability, scalability, and economic feasibility. This research quantitatively analyzed the applicability of various air-side economizers and their energy-saving potential in modular data centers. A detailed cooling load estimation process was established for modular data centers, and annual cooling energy simulations were carried out using various air-side economizers. The various air-side economizers yielded cooling coil load savings of 76–99% in comparison to conventional cooling systems in data centers, and the total cooling energy savings of the economizers ranged from 47.5% to 67.2%. Indirect air-side economizers with high-effectiveness heat exchangers were found to yield significant energy saving (63.6%) and have simple system configurations.

Impact of integrated hot water cooling and desiccant-assisted evaporative cooling systems on energy savings in a data center

The primary objective of this paper is to propose the integration of a hot water cooling system with a desiccant-assisted evaporative cooling system for air conditioning a data center. The feasibility of the integrated system is analyzed by a detailed energy simulation for a model data center by using TRNSYS (transient system simulation) 16 with a commercial equation solver program. The energy saving potential of the proposed system is evaluated by comparing it to a conventional air handling system with an air-side economizer serving the model data center.The results show that the proposed system saves more than 95% of the peak power demand and 84% of annual operating energy consumption with respect to the conventional air conditioning system for the data center. This advantage in energy savings is primarily obtained by the use of water-side free cooling in the hot water cooling system and the evaporative cooling effect enhanced by the liquid desiccant system in the air-side supply. Fan energy savings caused by reduced air flow in the proposed system also contributes to the reduction in operating energy.

Simplified server model to simulate data center cooling energy consumption

This paper proposes a server model that can be applied to simulating the annual cooling energy consumption of data centers and an analysis of its impact. Recently, aisle containment architecture and the variable air volume system have been widely adopted in the data center industry because of their superior indoor thermal management and cooling energy savings. However, the current simulation method, which fixes the server heat generation and the supply and return air temperature difference of the computer room air handler (CRAH), does not correctly reflect current cooling systems. In this study, a server model was developed that accounts for server thermal characteristics – including server power, fan airflow, and exhaust temperature – according to the given CPU utilization and temperature. After the proposed server model was validated, the annual cooling energy consumption was simulated for modular data centers with an air-side economizer and high ambient temperature. Unlike the conventional method, the proposed model showed that the cooling energy consumption increased when the CRAH supply air temperature was higher than 19°C because of the increase in fan energy consumption.

모듈러 데이터 센터에 적용된 다양한 외기냉방 시스템의 급기 조건 및 지역별 에너지 절감효과 분석

The main purpose of this paper is to analyze energy saving potentials of various economizers in modular data center by thermal conditions and locations in response to explosive IT demand and data centers' energy consumption increase. To investigate holistic energy saving potentials, various server thermal characteristics, economizers, and locations are analyzed on a modular data center. As a results, economizers can save cooling coil load 75-100% according to their running conditions, and indirect air-side economizer showed better performance than direct air-side economizer. Even though there is more chiller energy saving with server inlet temperature increase, total energy saving decreased more sharply due to fan energy increase. Furthermore, there should be more energy saving potentials in high latitude climates regardless of type of economizers.