Water-side Economizer Research Articles

Hybrid geothermal heat pumps for cooling telecommunications data centers

The technical and economic performance of hybrid geothermal heat pump (GHP) systems supplying year-round cooling to small data centers were analyzed and compared to air-source heat pump (ASHP) cooling systems. Numerical TRNSYS models were used to simulate the operation of five configurations that included GHPs, ASHPs, air-cooled heat exchangers – dry coolers (DCs), and/or waterside economizers (WSEs). The models were validated against data measured from an experimental GHP cooling system in Ithaca, NY, USA. The average coefficient of performance (COP) and the total cost of ownership (TCO) of the optimized systems were evaluated and compared to a base case ASHP cooling system. The results showed that the GHP systems had higher lifetime average COPs than the ASHP system, while the TCOs of the GHP systems were slightly higher than the ASHP system. The reductions in cooling capacity and performance of the geothermal systems due to subsurface temperature increases were calculated and showed that the addition of a DC or WSE mitigated capacity reductions and improved lifetime performance. The economic performance of the GHP systems relative to ASHP systems were analyzed using weather data from several locations across the U.S., with sensitivities to soil conductivity, price of electricity, and cost of drilling the geothermal wells quantified. GHP systems performed best in colder climates with greater temperature variability both seasonally and diurnally.

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.

Reliability and availability analysis of a hybrid cooling system with water-side economizer in data center

The cost of data center downtime has increased significantly recently and it is critical for any data center to minimize the unplanned downtime. A reliable cooling system is of great importance to ensure the thermal environment and achieve this goal. The reliability and availability analysis (RAA) is a scientific way to quantify the risk and determine the potential solutions for a system design and operation. Hybrid cooling system with water-side economizer as a promising energy saving method in data center has complicated configuration and multi operation modes. Thus, it is very necessary to conduct the RAA on this novel system and understand it. In this study, the Markov model combined with reliability block diagram method, which can drastically reduce the computation dimension, was developed to evaluate the reliability and operational availability (OA). Functional Availability (FA) was presented as a new measure by integrating OA with specific function criteria such as room temperature. Additionally, we proposed a maximum allowable downtime (MADT) to quantify how long a repair time is acceptable in different scenarios. The detailed method, evaluation procedure and results of a hybrid cooling system were presented.

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.

Transient simulation of wet cooling strategies for a data center in worldwide climate zones

A promising way to significantly reduce the total cost of ownership (TCO) of a data center is to minimize the cooling system energy consumption. To come up with the most energy efficient cooling system design, detailed analysis of various configurations based on local climate data is crucial. In this paper, an enterprise data center of 180ton (TR) cooling load is modeled using a transient energy analysis software TRNSYS with the operating environment in the data center maintained as per the guidelines of ASHRAE TC 9.9. Promising cooling strategies including water side economizer and indirect evaporative cooler (IEC) are modeled and analyzed for the 17 worldwide climate zones defined by ASHRAE 90.1. Energy savings potential of these strategies is presented. Amount of water consumed and the number of hours the strategy is active in a year is also estimated. Results indicate significant energy saving potential of water side economizer and IEC in most of the zones. As compared to air cooled chiller systems, more than 30% energy savings can be achieved in climate zones 3–7 by using IEC. Also, more than 25% energy savings can be achieved by using water side economizer in climate zone 4 and 5.

Energy conservation benefit of water-side free cooling in a liquid desiccant and evaporative cooling-assisted 100% outdoor air system

The main purpose of this research was to experimentally investigate a liquid desiccant and evaporative cooling-assisted 100% outdoor air system. The proposed system was integrated with water-side free cooling in the desiccant solution and process air cooling to enhance its energy performance. The experimental results show that the required cooling water temperature for the desiccant solution is higher than the conventional cooling water supply temperature; that is, approximately 22–27°C. Consequently, water-side free cooling was applied to produce the cooling water for the desiccant solution. The operation of the proposed system with the water-side economizer showed a 40–70% effectiveness of the indirect evaporative cooler, while that of the direct evaporative cooler was greater than 95%, and the supply air temperature ranged between 17 and 20°C. The energy coefficient of performance (COP) of water-side free cooling applied to cool the desiccant solution was 8–17, whereas that of the conventional air-cooled chiller was 1–3. Economic consideration indicated that the operating energy savings might offset the penalty in the initial cost of the proposed system.

Impact of aisle containment on energy performance of a data center when using an integrated water-side economizer

The main purpose of this study is to analyze the impact of cold aisle containment on the thermal management performance of a data center, as well as on the amount of energy consumed for cooling. The thermal management performance of the aisle containment architecture, which has been widely employed throughout the data center industry, is demonstrated by experiment. A computational fluid dynamics (CFD) modeling strategy is used for the containment air leakage prediction validated by experiments. The thermal management performance of an uncontained and contained aisles are compared through CFD simulation. In addition, since the containment's energy performance is maximized when an economizer is incorporated, a model-based simulation of the annual cooling energy consumption of a modular data center with an integrated water-side economizer is conducted. The simulation results show that the thermal management performance is excellent in both architectures with an appropriate cooling system control, but the energy savings are much greater with the contained architecture.

Airflow Optimization In Data Centers

A good airflow management scheme is critical to any data center operation. State-of-the-art IT equipment would fail to perform its functions if not provided with the required amount of cooling. Efficient cooling systems alone will not be able to do the job. Airflow—which acts as a liaison between these systems and carries the “cooling” from cooling systems to IT equipment, needs to be paid equal attention. Poor airflow management can turn a very good cooling and IT system into a mediocre one. On the other hand, a good airflow management scheme can help even a modest IT and cooling system to realize their full potential. The intent of this publication is to look at some ways of optimizing airflow in a data center space. These include but are not limited to: 1. Component Strategies: hot and cold aisle containment, efficient floor tiles, return air plenum extensions, variable frequency drives (VFDs), blanking panels, brush guards, return air registers, floor sealants, high efficiency plug fans, electronically commutated direct drive fan motors, etc.2. Control Strategies: integrated and smart control systems, wireless and wired sensors, optimization of temperature setpoints, run sequence, VFD speeds, air- and water-side economizer setpoints, reheat and humidification controls, etc.

Simulation of a temperature adaptive control strategy for an IWSE economizer in a data center

Nowadays, with the constant evolution of Information Technology (IT) equipments, the energy consumption of data center over the world becomes a major concern. In 2011 the ASHRAE Technical committee 9.9 (TC9.9) issued important guidelines concerning server temperature and hygrometric environment to help engineer in the design of cooling solutions. While raising the temperature may be a source of heat pump energy savings, it induces an increase in the Computer Room Air Handling (CRAH) unit energy requirement, lowering the benefits. Hence optimal temperature cooling set point must be found to maximise the efficiency of the cooling plant. To test various chiller control strategy a “full scale” model is proposed. A 32kW data center is considered, cooled by a centrifugal heat pump linked to a wet cooling tower. An Integrated Water Side Economizer (IWSE) is added to minimize the energy consumption the regulation and the chilled air production is simulated with the software TRNSYS. The temperature field in the server room is calculated with the CFD code Thetis. To create a link between the 2 simulation environments, a Reduced Order Model (ROM) using Proper Orthogonal Decomposition (POD) is program with MATLAB. Finally this numerical model is used to investigate the effect of server room temperature increase on the cooling plant energy consumption. A new Temperature Adaptive Control Strategy (TACS) that minimizes the energy need is proposed and tested.

Study on Outdoor Air Cooling System with Combined Air-side and Water-side Economizer for Data Centers : Part1-Efficiency Comparison of Each System

Study on Outdoor Air Cooling System with Combined Air-side and Water-side Economizer for Data Centers : Part1-Efficiency Comparison of Each System

Modelica Buildings library

This article describes the Buildings library, a free open-source library that is implemented in Modelica, an equation-based object-oriented modelling language. The library supports rapid prototyping, as well as design and operation of building energy and control systems. First, we describe the scope of the library, which covers heating, ventilation and air-conditioning systems, multi-zone heat transfer and multi-zone airflow and contaminant transport. Next, we describe differentiability requirements and address how we implemented them. We describe the class hierarchy that allows implementing component models by extending partial implementations of base models of heat and mass exchangers, and by instantiating basic models for conservation equations and flow resistances. We also describe associated tools for pre- and post-processing, regression tests, co-simulation and real-time data exchange with building automation systems. The article closes with an example of a chilled water plant, with and without water-side economizer, in which we analysed the system-level efficiency for different control setpoints.

Viability of datacenter cooling systems for energy efficiency in temperate or subtropical regions: Case study

In general, a proper balance of temperature and humidity control is essential for efficient datacenter operation and is integral to protecting the significant investment in computer and network technology in datacenter facilities. However, the rising costs of energy and the drive to be green are resulting in a greater demand to conserve energy. One method of reducing facility costs for a chilled water plant is by adding an economizer. The purpose of this study is to develop energy models of the most common economizer systems. A normal chiller plant with an air-side economizer and a water-side economizer are compared. Results show that outdoor conditions influence facility energy consumption. This paper provides terminology and definitions for the two different types of economizer modes and compares their energy performance against key datacenter attributes in temperate or subtropical regions. The electrical end use breakdown and the Power Usage Effectiveness (PUE) value for a typical year were estimated. The water-side economizer made it possible to achieve a maximum energy performance improvement of about 16.6% over the reference base cooling system, whereas the air-side economizer made it possible to achieve about 42.4% improvement.

403 外気冷熱を利用したデータセンター空調システムの検討(省エネルギー(1))

A outside air economizer systems is one effective solution for reducing the power consumption of air conditioning systems. In recent years, outside air economizer systems have gained the spotlight in Japan, so we have conducted a survey and simulation-based estimation toward their introduction. The estimation results have shown that the water-side economizer requires doubling the capacity of the cooling tower and consideration of the installation space and cost, while the air-side economizer increases the humidifying power, which requires the relaxation of indoor humidity specifications. According to this simulation-based comparison results, the package-type air-conditioning unit with an expanded scope of low pressure ratio control has the lowest power consumption per year.

Free Cooling Using Walter–side Economizer: Process Cooling Application At a Plastic Extrusion Plant

ABSTRACT This article is based on a detailed feasibility study conducted in 2007 for the installation of a free cooling system for process cooling at a plastic extrusion plant in the greater Toronto area utilizing a water economizer circuit. The energy consumption of the cooling system, which had a 130-ton chiller capacity, comprised 20 percent of the total electrical energy consumption for the production plant under study. Although the case study presented in this article is for a plastic extrusion process application, the findings can be applied to the design and savings calculations of free cooling systems for other industrial processes and for space cooling applications as well. This study proposed a free cooling system design for the process cooling system. The design makes use of a plate and frame heat exchanger that serves as a water-side economizer to cool the chilled water holding tank, using cooling tower water during cold weather conditions. This article explores the technical and financial fea...

A Case Study of Energy Savings by using the Water-Side Economiser System in a Large Office Building in Montreal

This paper presents the feasibility study of the implementation of a water-side economizer system in a large existing office building in Montreal, for reducing the electricity consumption and the peak electric demand for chillers in winter. The evaluation was performed by computer simulation using the MICRO-DOE2 program. The study predicts, under conservative assumptions, energy savings of about 34,000 CAN$/year.