Abstract:
A system and method for providing energy assessment and optimization in a data center that includes at least one cooling provider, and at least one cooling consumer, the at least one cooling consumer having cooling requirements. The method according to one aspect includes receiving data regarding cooling availability and power consumption for the at least one cooling consumer, cooling capacity of the at least one cooling provider, and a physical relationship between the at least one cooling consumer and the at least one cooling provider in the data center, storing the received data, determining airflow distribution effectiveness between the at least one cooling consumer and the at least one cooling provider, and displaying at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider.

Description:
BACKGROUND 
     1. Field of the Invention 
     At least one embodiment in accordance with the present invention relates generally to systems and methods for data center management assessment, and more specifically, to systems and methods for managing data center airflow and energy usage. 
     2. Discussion of Related Art 
     In response to the increasing demands of information-based economies, information technology networks continue to proliferate across the globe. One manifestation of this growth is the centralized network data center. A centralized network data center typically consists of various information technology (IT) equipment, collocated in a structure that provides network connectivity, electrical power and cooling capacity. In a typical data center, only about half of the energy consumption goes directly to IT loads. The remainder is consumed in the power and cooling infrastructure with the cooling equipment consuming the majority. 
     Various processes and software applications, such as the InfrastruXure® Central product available from American Power Conversion Corporation of West Kingston, R.I., have been developed to aid data center personnel in designing and maintaining efficient and effective of data centers configurations. These tools often guide data center personnel through activities such as designing the data center structure, positioning equipment within the data center prior to installation and repositioning equipment after construction and installation are complete. Thus, conventional tool sets provide data center personnel with a standardized and predictable design methodology. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is directed to a computer-implemented method for providing energy assessment and optimization in a data center that includes at least one cooling provider, and at least one cooling consumer, the at least one cooling consumer having cooling requirements. The method includes receiving data regarding cooling availability and power consumption for the at least one cooling consumer, cooling capacity of the at least one cooling provider, and a physical relationship between the at least one cooling consumer and the at least one cooling provider in the data center, storing the received data, determining at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider, and displaying the at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider. 
     The method may further include displaying at least one optimized setting for the at least one cooling provider that results in a reduction in energy usage of the data center while satisfying the cooling requirements of the cooling consumer. The at least one optimized setting may be an airflow setting of the at least one cooling provider. The at least one optimized setting may relate to temperature of a coolant supplied to the at least one cooling provider. The method may further include adjusting the at least one optimized setting for the at least one cooling provider to reduce energy usage of the data center. Adjusting the at least one optimized setting may include adjusting an airflow setting of the at least one cooling provider. Adjusting the at least one optimized setting may include adjusting temperature of a coolant supplied to the at least one cooling provider, and may include adjusting an airflow setting of the at least one cooling provider and adjusting temperature of a coolant supplied to the at least one cooling provider. The at least one cooling consumer may include a plurality of equipment racks in the data center, and the at least one cooling provider may include a plurality of coolers, and the method may further include creating a model of the data center with the plurality of equipment racks represented by a single equipment rack and the plurality of coolers represented by a single cooler, and determining lumped cooling availability and power consumption for the single equipment rack, based on characteristics of each of the plurality of equipment racks, and determining lumped cooling capacity of the single cooler based on characteristics of the plurality of coolers, wherein determining at least one value representative of the effectiveness of the distribution of airflow includes determining at least one value representative of the effectiveness of the distribution of airflow between the single equipment rack and the single cooler. The method may further include providing a user interface on a computer screen, wherein the user interface includes user selectable elements to adjust settings for the at least one cooling provider, receiving input from a user to adjust the settings for the at least one cooling provider, and providing an updated value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider in real time based on the input received. The method may further include determining the at least one optimized setting based at least in part on any fractional increase in power due to an increase in fan speed of at least one server in the data center. 
     Another aspect of the invention is directed to a system for presenting a cooling model of a data center that includes at least one cooling provider, and at least one cooling consumer, the at least one cooling consumer having cooling requirements. The system includes an interface, and a controller configured to receive data regarding cooling availability and power consumption for the at least one cooling consumer, cooling capacity of the at least one cooling provider, and a physical relationship between the at least one cooling consumer and the at least one cooling provider in the data center, store the received data, determine at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider, and display on the interface the at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider. 
     The controller may be further configured to display on the interface at least one optimized setting for the at least one cooling provider that results in a reduction in energy usage of the data center while meeting the cooling requirements of the at least one cooling consumer, and the at least one optimized setting may be an airflow setting of the at least one cooling provider. The at least one optimized setting may relate to temperature of a coolant supplied to the at least one cooling provider. The controller may be further configured to adjust the at least one optimized setting for the at least one cooling provider to reduce energy usage of the data center, and the controller may be configured to adjust an airflow setting of the at least one cooling provider to reduce energy usage of the data center, and to adjust temperature of a coolant supplied to the at least one cooling provider. The controller may also be configured to adjust an airflow setting of the at least one cooling provider and adjust temperature of a coolant supplied to the at least one cooling provider. The at least one cooling consumer may include a plurality of equipment racks in the data center, and the at least one cooling provider may includes a plurality of coolers, and the controller may be further configured to create and display on the interface a model of the data center with the plurality of equipment racks represented by a single equipment rack and the plurality of coolers represented by a single cooler, and determine lumped cooling availability and power consumption for the single equipment rack, based on characteristics of each of the plurality of equipment racks, and determine lumped cooling capacity of the single cooler based on characteristics of the plurality of coolers. The controller may be further configured to display on a computer screen of the user interface graphics that include user selectable elements to adjust settings for the at least one cooling provider, receive input from a user to adjust the settings for the at least one cooling provider, and provide an updated value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider in real time based on the input received. The controller may be configured to determine the at least one optimized setting based at least in part on any fractional increase in power due to an increase in fan speed of at least one server in the data center. 
     Another aspect of the invention is directed to a computer readable medium. The computer readable medium has stored thereon sequences of instruction including instructions that will cause a processor to receive data regarding cooling availability and power consumption for at least one cooling consumer, cooling capacity for at least one cooling provider, and a physical relationship between the at least one cooling consumer and the at least one cooling provider in a data center, store the received data, determine at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider, and provide output to display on an interface the at least one value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider. 
     The sequences of instruction may include instructions that will cause the processor to display on the interface at least one optimized setting for the at least one cooling provider that results in a reduction in energy usage of the data center while meeting the cooling requirements of the cooling consumer. The at least one optimized setting may be an airflow setting of the at least one cooling provider. The at least one optimized setting may relate to temperature of a coolant supplied to the at least one cooling provider. The sequences of instruction may include instructions that will cause the processor to provide an output to adjust the at least one optimized setting for the at least one cooling provider to reduce energy usage of the data center. The sequences of instruction may include instructions that will cause the processor to provide an output to adjust an airflow setting of the at least one cooling provider to reduce energy usage of the data center. The sequences of instruction may also include instructions that will cause the processor to provide an output to adjust temperature of a coolant supplied to the at least one cooling provider. The sequences of instruction may include instructions that will cause the processor to provide an output to adjust an airflow setting of the at least one cooling provider and adjust temperature of a coolant supplied to the at least one cooling provider. The sequences of instruction may further include instructions that will cause the processor to create and display on the interface a model of a data center with a plurality of equipment racks represented by a single equipment rack and a plurality of coolers represented by a single computer room air conditioner, and determine lumped cooling availability and power consumption for the single equipment rack, based on characteristics of each of the plurality of equipment racks, and determine lumped cooling capacity of the single cooler based on characteristics of the plurality of coolers, and determine at least one value representative of the effectiveness of the distribution of airflow in the data center between the single equipment rack and the single cooler. The sequences of instruction may include instructions that will cause the processor to provide data to the interface to display graphics that include user selectable elements to adjust settings for the at least one cooling consumer, receive input from a user to adjust the settings for the at least one cooling consumer, and provide an updated value representative of the effectiveness of the distribution of airflow in the data center between the at least one cooling consumer and the at least one cooling provider in real time based on the input received. The sequences of instruction may include instructions that will cause the processor to determine the at least one optimized setting based at least in part on any fractional increase in power due to an increase in fan speed of at least one server in the data center. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
         FIG. 1  shows an example computer system with which various aspects in accord with the present invention may be implemented; 
         FIG. 2  illustrates an example distributed system including an embodiment; 
         FIG. 3  shows a graph comparing rack inlet temperature rise verses air ratio; 
         FIG. 4  shows a basic block diagram of a data center; 
         FIG. 5  shows an airflow diagram that may be used as part of a user interface in at least one embodiment of the invention; 
         FIG. 6  shows a graphical user interface that may be used in one embodiment to input settings into a software tool; 
         FIG. 7  shows a graphical user interface that may be used to display results of one or more processes conducted in accordance with one embodiment of the invention; 
         FIG. 8  shows a graphical user interface that may be used to display results of one or more processes conducted in accordance with one embodiment of the invention; 
         FIG. 9  shows a graphical user interface that may be used to display results of one or more processes conducted in accordance with one embodiment of the invention; and 
         FIG. 10  shows a graphical user interface that may be used to display results of one or more processes conducted in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present invention disclosed herein, are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. These aspects are capable of assuming other embodiments and of being practiced or of being carried out in various ways. Examples of specific implementations are provided herein for illustrative purposes only and are not intended to be limiting. In particular, acts, elements and features discussed in connection with any one or more embodiments are not intended to be excluded from a similar role in any other embodiments. 
     At least some embodiments in accordance with the present invention relate to systems and processes through which a user may assess the airflow and energy usage in a data center, and modify parameters of equipment in the data center to optimize airflow and energy usage. As discussed above, only about half of the energy consumption in a data center goes directly to the IT loads. The remainder is consumed in the power and cooling infrastructure with the cooling equipment consuming the majority of this energy. Within the cooling equipment itself, the majority of power consumption is by the chiller and Computer Room Air Conditioner (cooler) fans. Even a modest increase in the chilled water temperature of the chiller, or a modest reduction in fan speed (and airflow rate) can result in large energy savings. 
     A full energy analysis of a data center typically requires the use of complex computational fluid dynamics (CFD) software along with finely detailed input data of characteristics of the data center. Such an analysis can be very expensive, require highly skilled personnel, and may take days or weeks to produce high quality results. 
     At least one embodiment of the present invention provides a method and a system for performing airflow and energy-use assessments in real-time without specially trained personnel. In embodiments of the invention discussed herein, the performance of assessments and calculations in real-time refers to processes that are completed in a matter of a few seconds or less rather than several minutes or longer as can happen with complex CFD calculations. The ability to perform assessments quickly and inexpensively is particularly beneficial in performing multiple assessments as part of an optimization process. 
     Embodiments of the invention may be implemented in one or more computer systems. For example, according to one embodiment of the present invention, a computer system is configured to perform any of the functions described herein, including but not limited to, configuring, modeling, assessing and presenting information regarding specific data center configurations. However, such a system may also perform other functions, such as suggesting changes to data center configurations, based on, for example, industry best practices, and may also provide suggestions for and implement changes to the cooling system including one or more chillers and one or more coolers. Moreover, the systems described herein may be configured to include or exclude any of the functions discussed herein. Thus the invention is not limited to a specific function or set of functions. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     Computer System 
     Various aspects and functions described herein in accordance with the present invention may be implemented as hardware or software on one or more computer systems. There are many examples of computer systems currently in use. These examples include, among others, network appliances, personal computers, workstations, mainframes, networked clients, servers, media servers, application servers, database servers and web servers. Other examples of computer systems may include mobile computing devices, such as cellular phones and personal digital assistants, and network equipment, such as load balancers, routers and switches. Further, aspects in accordance with the present invention may be located on a single computer system or may be distributed among a plurality of computer systems connected to one or more communications networks. 
     For example, various aspects and functions may be distributed among one or more computer systems configured to provide a service to one or more client computers, or to perform an overall task as part of a distributed system. Additionally, aspects may be performed on a client-server or multi-tier system that includes components distributed among one or more server systems that perform various functions. Thus, the invention is not limited to executing on any particular system or group of systems. Further, aspects may be implemented in software, hardware or firmware, or any combination thereof. Thus, aspects in accord with the present invention may be implemented within methods, acts, systems, system elements and components using a variety of hardware and software configurations, and the invention is not limited to any particular distributed architecture, network, or communication protocol. 
       FIG. 1  shows a block diagram of a distributed computer system  100 , in which various aspects and functions in accord with the present invention may be practiced. Distributed computer system  100  may include one more computer systems. For example, as illustrated, distributed computer system  100  includes computer systems  102 ,  104  and  106 . As shown, computer systems  102 ,  104  and  106  are interconnected by, and may exchange data through, communication network  108 . Network  108  may include any communication network through which computer systems may exchange data. To exchange data using network  108 , computer systems  102 ,  104  and  106  and network  108  may use various methods, protocols and standards, including, among others, token ring, ethernet, wireless ethernet, Bluetooth, TCP/IP, UDP, Http, FTP, SNMP, SMS, MMS, SS7, Json, Soap, and Corba. To ensure data transfer is secure, computer systems  102 ,  104  and  106  may transmit data via network  108  using a variety of security measures including TSL, SSL or VPN among other security techniques. While distributed computer system  100  illustrates three networked computer systems, distributed computer system  100  may include any number of computer systems and computing devices, networked using any medium and communication protocol. 
     Various aspects and functions in accordance with the present invention may be implemented as specialized hardware or software executing in one or more computer systems including computer system  102  shown in  FIG. 1 . As depicted, computer system  102  includes processor  110 , memory  112 , bus  114 , interface  116  and storage  118 . Processor  110  may perform a series of instructions that result in manipulated data. Processor  110  may be a commercially available processor such as an Intel Pentium, Motorola PowerPC, SGI MIPS, Sun UltraSPARC, or Hewlett-Packard PA-RISC processor, but may be any type of processor or controller as many other processors and controllers are available. Processor  110  is connected to other system elements, including one or more memory devices  112 , by bus  114 . 
     Memory  112  may be used for storing programs and data during operation of computer system  102 . Thus, memory  112  may be a relatively high performance, volatile, random access memory such as a dynamic random access memory (DRAM) or static memory (SRAM). However, memory  112  may include any device for storing data, such as a disk drive or other non-volatile storage device. Various embodiments in accordance with the present invention may organize memory  112  into particularized and, in some cases, unique structures to perform the aspects and functions disclosed herein. 
     Components of computer system  102  may be coupled by an interconnection element such as bus  114 . Bus  114  may include one or more physical busses, for example, busses between components that are integrated within a same machine, but may include any communication coupling between system elements including specialized or standard computing bus technologies such as IDE, SCSI, PCI and InfiniBand. Thus, bus  114  enables communications, for example, data and instructions, to be exchanged between system components of computer system  102 . 
     Computer system  102  also includes one or more interface devices  116  such as input devices, output devices and combination input/output devices. Interface devices may receive input or provide output. More particularly, output devices may render information for external presentation. Input devices may accept information from external sources. Examples of interface devices include keyboards, mouse devices, trackballs, microphones, touch screens, printing devices, display screens, speakers, network interface cards, etc. Interface devices allow computer system  102  to exchange information and communicate with external entities, such as users and other systems. 
     Storage system  118  may include a computer readable and writeable nonvolatile storage medium in which instructions are stored that define a program to be executed by the processor. Storage system  118  also may include information that is recorded, on or in, the medium, and this information may be processed by the program. More specifically, the information may be stored in one or more data structures specifically configured to conserve storage space or increase data exchange performance. The instructions may be persistently stored as encoded signals, and the instructions may cause a processor to perform any of the functions described herein. The medium may, for example, be optical disk, magnetic disk or flash memory, among others. In operation, the processor or some other controller may cause data to be read from the nonvolatile recording medium into another memory, such as memory  112 , that allows for faster access to the information by the processor than does the storage medium included in storage system  118 . The memory may be located in storage system  118  or in memory  112 , however, processor  110  may manipulate the data within the memory  112 , and then copies the data to the medium associated with storage system  118  after processing is completed. A variety of components may manage data movement between the medium and integrated circuit memory element and the invention is not limited thereto. Further, the invention is not limited to a particular memory system or storage system. 
     Although computer system  102  is shown by way of example as one type of computer system upon which various aspects and functions in accordance with the present invention may be practiced, aspects of the invention are not limited to being implemented on the computer system as shown in  FIG. 1 . Various aspects and functions in accord with the present invention may be practiced on one or more computers having a different architectures or components than that shown in  FIG. 1 . For instance, computer system  102  may include specially-programmed, special-purpose hardware, for example, an application-specific integrated circuit (ASIC) tailored to perform a particular operation disclosed herein. While another embodiment may perform the same function using several general-purpose computing devices running MAC OS System X with Motorola PowerPC processors and several specialized computing devices running proprietary hardware and operating systems. 
     Computer system  102  may be a computer system including an operating system that manages at least a portion of the hardware elements included in computer system  102 . Usually, a processor or controller, such as processor  110 , executes an operating system which may be, for example, a Windows-based operating system, such as, Windows NT, Windows 2000 (Windows ME), Windows XP or Windows Vista operating systems, available from the Microsoft Corporation, a MAC OS System X operating system available from Apple Computer, one of many Linux-based operating system distributions, for example, the Enterprise Linux operating system available from Red Hat Inc., a Solaris operating system available from Sun Microsystems, or a UNIX operating system available from various sources. Many other operating systems may be used, and embodiments are not limited to any particular implementation. 
     The processor and operating system together define a computer platform for which application programs in high-level programming languages may be written. These component applications may be executable, intermediate, for example, C−, bytecode or interpreted code which communicates over a communication network, for example, the Internet, using a communication protocol, for example, TCP/IP. Similarly, aspects in accord with the present invention may be implemented using an object-oriented programming language, such as .Net, SmallTalk, Java, C++, Ada, or C# (C-Sharp). Other object-oriented programming languages may also be used. Alternatively, functional, scripting, or logical programming languages may be used. 
     Additionally, various aspects and functions in accordance with the present invention may be implemented in a non-programmed environment, for example, documents created in HTML, XML or other format that, when viewed in a window of a browser program, render aspects of a graphical-user interface or perform other functions. Further, various embodiments in accord with the present invention may be implemented as programmed or non-programmed elements, or any combination thereof. For example, a web page may be implemented using HTML while a data object called from within the web page may be written in C++. Thus, the invention is not limited to a specific programming language and any suitable programming language could also be used. 
     A computer system included within an embodiment may perform additional functions outside the scope of the invention. For instance, aspects of the system may be implemented using an existing commercial product, such as, for example, Database Management Systems such as SQL Server available from Microsoft of Seattle Wash., Oracle Database from Oracle of Redwood Shores, Calif., and MySQL from MySQL AB of Uppsala, Sweden or integration software such as Web Sphere middleware from IBM of Armonk, N.Y. However, a computer system running, for example, SQL Server may be able to support both aspects in accord with the present invention and databases for sundry applications not within the scope of the invention. 
     Example System Architecture 
       FIG. 2  presents a context diagram including physical and logical elements of distributed system  200 . As shown, distributed system  200  is specially configured in accordance with the present invention. The system structure and content recited with regard to  FIG. 2  is for exemplary purposes only and is not intended to limit the invention to the specific structure shown in  FIG. 2 . As will be apparent to one of ordinary skill in the art, many variant system structures can be architected without deviating from the scope of the present invention. The particular arrangement presented in  FIG. 2  was chosen to promote clarity. 
     Information may flow between the elements, components and subsystems depicted in  FIG. 2  using any technique. Such techniques include, for example, passing the information over the network via TCP/IP, passing the information between modules in memory and passing the information by writing to a file, database, or some other non-volatile storage device. Other techniques and protocols may be used without departing from the scope of the invention. 
     Referring to  FIG. 2 , system  200  includes user  202 , interface  204 , data center design and management system  206 , communications network  208  and data center database  210 . System  200  may allow user  202 , such as a data center architect or other data center personnel, to interact with interface  204  to create or modify a model of one or more data center configurations. According to one embodiment, interface  204  may include aspects of the floor editor and the rack editor as disclosed in Patent Cooperation Treaty Application No. PCT/US08/63675, entitled METHODS AND SYSTEMS FOR MANAGING FACILITY POWER AND COOLING, filed on May 15, 2008, which is incorporated herein by reference in its entirety and is hereinafter referred to as PCT/US08/63675. In other embodiments, interface  204  may be implemented with specialized facilities that enable user  202  to design, in a drag and drop fashion, a model that includes a representation of the physical layout of a data center or any subset thereof. This layout may include representations of data center structural components as well as data center equipment. The features of interface  204 , as may be found in various embodiments in accordance with the present invention, are discussed further below. In at least one embodiment, information regarding a data center is entered into system  200  through the interface, and assessments and recommendations for the data center are provided to the user. Further, in at least one embodiment, optimization processes may be performed to optimize cooling performance and energy usage of the data center. 
     As shown in  FIG. 2 , data center design and management system  206  presents design interface  204  to user  202 . According to one embodiment, data center design and management system  206  may include the data center design and management system as disclosed in PCT/US08/63675. In this embodiment, design interface  204  may incorporate functionality of the input module, the display module and the builder module included in PCT/US08/63675 and may use the database module to store and retrieve data. 
     As illustrated, data center design and management system  206  may exchange information with data center database  210  via network  208 . This information may include any information required to support the features and functions of data center design and management system  206 . For example, in one embodiment, data center database  210  may include at least some portion of the data stored in the data center equipment database described in PCT/US08/63675. In another embodiment, this information may include any information required to support interface  204 , such as, among other data, the physical layout of one or more data center model configurations, the production and distribution characteristics of the cooling providers included in the model configurations, the consumption characteristics of the cooling consumers in the model configurations and one or more cooling metrics characterizing the amount of cool air produced by the cooling providers that is lost prior to being consumed by the cooling consumers. 
     In one embodiment, data center database  210  may store types of cooling providers, the amount of cool air provided by each type of cooling provider, and a temperature of cool air provided by the cooling provider. Thus, for example, data center database  210  includes record of a particular type of cooling unit that is rated to deliver airflow at the rate of 5,600 cfm at a temperature of 68 degrees Fahrenheit. In addition, the data center database  210  may store one or more cooling metrics, such as inlet and outlet temperatures of the coolers and inlet and outlet temperatures of one or more equipment racks. The temperatures may be periodically measured and input into the system, or in other embodiments, the temperatures may be continuously monitored using devices coupled to the system  200 . 
     Data center database  210  may take the form of any logical construction capable of storing information on a computer readable medium including, among other structures, flat files, indexed files, hierarchical databases, relational databases or object oriented databases. The data may be modeled using unique and foreign key relationships and indexes. The unique and foreign key relationships and indexes may be established between the various fields and tables to ensure both data integrity and data interchange performance. 
     The computer systems shown in  FIG. 2 , which include data center design and management system  206 , network  208  and data center equipment database  210 , each may include one or more computer systems. As discussed above with regard to  FIG. 1 , computer systems may have one or more processors or controllers, memory and interface devices. The particular configuration of system  200  depicted in  FIG. 2  is used for illustration purposes only and embodiments of the invention may be practiced in other contexts. Thus, embodiments of the invention are not limited to a specific number of users or systems. 
     Data Center Assessment and Optimization Embodiments 
     In at least one embodiment, which will now be described, data center airflow and energy assessments are performed based on a novel data center performance characteristic identified as Air Distribution Effectiveness (ADE), which relates equipment rack inlet temperatures to cooler airflow rate by a relationship which is determined based on the type of cooling architecture that is used (e.g., in-row, raised floor, overhead supply, etc.) In other embodiments other airflow metrics other than ADE may be used. ADE characterizes a facility&#39;s effectiveness at delivering cooling airflow to IT equipment racks, and in at least one embodiment, the ADE for a facility, as described below in greater detail, is computed from simple temperature measurements along with an estimate of total IT load. The ADE may be expressed as a single number between 0% (indicating poor performance) and 100% (indicating satisfactory performance). With a known ADE, in embodiments of the invention, chilled water supply temperature and cooler airflow can be adjusted to maximize energy savings while maintaining acceptable equipment rack inlet temperatures. 
     In one embodiment, which will now be described in detail, the data center design and management system  200  is configured to perform a process that determines ADE for a facility and provides tools implemented as graphical user interfaces that allow a user to optimize energy savings associated with cooling IT equipment in a facility. In this embodiment, calculations for a data center are performed by first producing a model of the data center as one cooler and one IT equipment rack. The single lumped cooler airflow and supply and return temperatures are equal to the actual cooler airflow and average supply and return temperatures respectively. Similarly, the single lumped rack airflow and inlet and exhaust temperatures are equal to the actual total rack airflow and average inlet and exhaust temperatures respectively. As discussed below in greater detail, inputs to the tool include measured temperatures, along with parameters associated with the facility&#39;s chillers, coolers and IT equipment racks. Also, the user can set a maximum inlet temperature for the IT equipment racks. The tool determines an “r” factor (described below), and based on the r factor and the other parameters, computes the facility&#39;s optimized air ratio (AR), which is defined as the ratio of total cooler airflow to total IT load airflow. The “r” factor is an empirically-determined factor related to the coupling that exists in a facility between the airflow output from the facility&#39;s coolers, and the airflow input to the facility&#39;s IT equipment racks. 
     In a data center, as well understood by one of ordinary skill in the art, the average temperature at the inlet side of an IT equipment rack T i  relative to the cooler supply temperature T s , defined as ΔT IT =T i −T s , may change gradually or very rapidly with changes in the air ratio (AR) depending on the coupling factor r.  FIG. 3  demonstrates how the inlet temperature of equipment racks varies with changes in air ratio for different r values. For a facility in which the airflow is extremely well mixed (for example, a facility with upflow cooling units or ceiling diffusers), r is low and the temperature rise is substantially inversely proportional (r=1) to the air ratio (AR). For a well-designed raised floor facility, it has been found that r may be as great as 5, such that the relationship is 1/AR 5 . 
     The Air Distribution Effectiveness (ADE or ε), mentioned above, may be calculated using equation (1) below: 
                   ɛ   =     ⅇ         -   Δ     ⁢           ⁢     T   IT     ⁢     AR   r         Δ   ⁢           ⁢     T   L                   Equation   ⁢           ⁢     (   1   )                 
where ΔT L =T e −T i  is the (airflow-weighted) average temperature rise across the IT racks, with T e  being the temperature of air exiting from the rack and T i  being the temperature of air entering the rack. Solving (1) for ΔT IT  results in equation (2) below:
 
     
       
         
           
             
               
                 
                   
                     Δ 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       T 
                       IT 
                     
                   
                   = 
                   
                     
                       
                         - 
                         ln 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       ɛΔ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         T 
                         L 
                       
                     
                     
                       AR 
                       r 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
     The graph in  FIG. 3  shows the relationship between the temperature rise at the equipment rack inlet for several different values of r based on equation 2 with ε=0.7 and ΔT L =20° F. 
     From equation (1), it is seen that for a very large AR (for example approaching infinity), the Air Distribution Effectiveness ε goes to zero, showing that the cooling distribution becomes ineffective as the air ratio gets very large. Further, as ΔT IT  approaches zero, the Air Distribution Effectiveness ε approaches 1, showing that the cooling distribution is more effective the closer ΔT IT  is to zero. Finally, as ΔT L  gets large, the Air Distribution Effectiveness ε approaches one, implying that, for a fixed AR and ΔT IT , the greater the IT load the more effective the cooling architecture. 
     Based on the foregoing, it is readily apparent to one of ordinary skill in the art, that the value of the Air Distribution Effectiveness, for a given data center family (fixed r value), is a single number between 0 and 1 (or, alternatively, a percentage between 0% and 100%) which is independent of IT load and air ratio that assesses the facility&#39;s ability to deliver cooling airflow to the IT equipment. Thus, it is meaningful to compare the Air Distribution Effectiveness between facilities of similar architecture but it is not meaningful to compare the ADE of a facility that uses InRow cooling to the ADE of a facility that uses upflow cooling. In addition to serving as a valuable assessment metric for a facility, the Air Distribution Effectiveness concept provides a link between IT load inlet temperature and AR (Equation 2) which is useful in embodiments of the invention to optimize AR and chilled water temperature settings while respecting the rack inlet temperature limit without the need for complex CFD calculations. 
     In embodiments of the present invention, in addition to Air Distribution Effectiveness, other metrics have been developed and are used to analyze the cooling effectiveness of a facility. These metrics include Bypass Ratio (BR) and Recirculation Ratio (RR). The Bypass Ratio and Recirculation Ratio are determined using Equations (3) and (4) below: 
     
       
         
           
             
               
                 
                   BR 
                   = 
                   
                     
                       
                         
                           T 
                           e 
                         
                         - 
                         
                           T 
                           r 
                         
                       
                       
                         
                           T 
                           e 
                         
                         - 
                         
                           T 
                           s 
                         
                       
                     
                     = 
                     
                       
                         Bypass 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         airflow 
                       
                       
                         CRAC 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         supply 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         airflow 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
             
               
                 
                   RR 
                   = 
                   
                     
                       
                         
                           T 
                           i 
                         
                         - 
                         
                           T 
                           s 
                         
                       
                       
                         
                           T 
                           e 
                         
                         - 
                         
                           T 
                           s 
                         
                       
                     
                     = 
                     
                       
                         Recirculation 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         airflow 
                       
                       
                         Total 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         IT 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         airflow 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
     Unlike Airflow Distribution Effectiveness, BR and RR vary with air ratio. More specifically, the amount of bypass and recirculated airflow will change with changes in cooler airflow. 
     As discussed above, methods and systems in accordance with embodiments of the invention may be used to provide energy savings in a facility by allowing increases in the chilled water temperature and decreases in the cooler airflow, while maintaining satisfactory cooling of IT equipment. As discussed in “Cooling Solutions for IT: A Guide to Planning, Design and Operation, BSRIA Guidance,” Note BG, May, 2003, by N. Pavey, et al. for every 1 degree C. increase in chilled water temperature, about 3.5% of the chiller power can be saved. This statement can be expressed in dimensionless form for temperatures in degrees F. by Equation (5) below: 
     
       
         
           
             
               
                 
                   
                     
                       
                         P 
                         
                           c 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       - 
                       
                         P 
                         
                           c 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                     
                     
                       P 
                       
                         c 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   = 
                   
                     0.39 
                     ⁢ 
                     
                       
                         
                           T 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             2 
                           
                         
                         - 
                         
                           T 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                       
                         Δ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           T 
                           ref 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
       
     
     where ΔT ref =20° F.=11.1° C. 
     In Equation (5), P C  is the chiller power and T C  is the chiller water temperature. The subscripts “1” and “2” refer to current and alternative operating points respectively. 
     As is known, in a typical cooler, fan power increases with the cube of airflow rate, and accordingly, the total fan power savings as a result of lowering the airflow rate of a cooler can be expressed using Equation (6) below: 
     
       
         
           
             
               
                 
                   
                     
                       
                         P 
                         
                           f 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           1 
                         
                       
                       - 
                       
                         P 
                         
                           f 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                     
                     
                       P 
                       
                         f 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   = 
                   
                     1 
                     - 
                     
                       
                         ( 
                         
                           
                             AR 
                             2 
                           
                           
                             AR 
                             1 
                           
                         
                         ) 
                       
                       3 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
       
     
     In Equation (6), P F  is fan power, and the subscripts “1” and “2” refer to current and alternative operating points. The Total Fractional Power Savings (TFPS) for a configuration in a facility may then be determined in embodiments of the invention using Equation (7). Equation (7) results from combining Equations (5) and (6). 
     
       
         
           
             
               
                 
                   TFPS 
                   = 
                   
                     
                       
                         ( 
                         
                           0.39 
                           ⁢ 
                           
                             
                               
                                 T 
                                 
                                   c 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   2 
                                 
                               
                               - 
                               
                                 T 
                                 
                                   c 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   1 
                                 
                               
                             
                             
                               Δ 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 T 
                                 ref 
                               
                             
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             P 
                             
                               c 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             
                               P 
                               
                                 c 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             + 
                             
                               P 
                               
                                 f 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                         
                         ) 
                       
                     
                     + 
                     
                       
                         { 
                         
                           1 
                           - 
                           
                             
                               ( 
                               
                                 
                                   AR 
                                   2 
                                 
                                 
                                   AR 
                                   1 
                                 
                               
                               ) 
                             
                             3 
                           
                         
                         } 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             P 
                             
                               c 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             
                               P 
                               
                                 c 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             + 
                             
                               P 
                               
                                 f 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     7 
                     ) 
                   
                 
               
             
           
         
       
     
     The optimal operating point from an energy perspective is determined in at least some embodiments by maximizing Equation (7) subject to certain constraints and assumptions. In a simple embodiment, it is assumed that the temperature difference between the cooler supply and the chilled water remains constant as the chilled water temperature is varied (T c −T s =constant). In other embodiments, the cooler supply temperature is computed more accurately using well-known heat exchanger-analysis techniques such as the Log Mean Temperature Difference (LMTD) or ε-NTU methods. Thus, variations in the chilled water temperature of from chiller result in the a variation in temperature of the supply airflow from the cooler. It is also assumed that the supply temperature is limited by the maximum allowable rack inlet temperature. This limit for the supply temperature can be determined by expressing Equation (2) above, in the form shown by Equation (8) below: 
     
       
         
           
             
               
                 
                   
                     T 
                     
                       s 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       2 
                     
                   
                   ≤ 
                   
                     
                       T 
                       max 
                     
                     + 
                     
                       
                         ln 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         ɛΔ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           T 
                           L 
                         
                       
                       
                         AR 
                         2 
                         r 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     8 
                     ) 
                   
                 
               
             
           
         
       
     
     In Equation (8), T max  is the maximum allowable input temperature for the IT equipment racks, which is set by the user in at least some embodiments, and T s2  is the resulting optimized temperature of the supply air from the cooler. In some embodiments of systems and tools that implement the above described optimization process, additional constraints on values may be imposed by the user. For example, the user may impose additional upper and lower limits on AR 2  and T C2  based on practical considerations. For example, the data center may be served by a campus-wide chiller system that does not accommodate changes to T c . Further, in at least some embodiments, a user is not permitted to set the cooler return temperature to be higher than the equipment rack exhaust temperature. 
     In one embodiment, a software tool determines the optimum T c2  and AR 2  using Excel Solver; however in other embodiments, other techniques, including non-linear methods, such as “steepest ascent” or “Newton directions” may be used. In other embodiments, approximate results can also be found by compiling a table of possible air ratio and coolant temperature combinations then searching through the points to find the best feasible pairing in the table with respect to a design goal such as minimizing energy consumption. 
     Embodiments of the present invention will now be described in further detail with reference to  FIGS. 4-7 .  FIG. 4  shows a basic block diagram representing a model of a data center  400 . The data center includes a controller  402 , an equipment or IT rack  404 , a cooler  406  and a chiller  408 . The controller  402  is coupled to the cooler  406  and the chiller  408  to monitor and control parameters of each. The controller  402  is also coupled to the equipment rack  404 , and more particularly, may be coupled to one or more sensors internal and/or external to the equipment rack to measure air temperatures and monitor power of the equipment rack  404 . The coupling between the controller and the other equipment may be accomplished using one or more computer networks as discussed above, and additional controllers may be used. The chiller is coupled to the cooler  406  using input and return coolant lines  410  and  412 . As is well known, the chiller may be located outside the data center. In the model shown in  FIG. 4 , as discussed above, the cooler  406  and the equipment rack  404  may be representative of multiple coolers and equipment racks contained in a data center, and the controller may be coupled to the multiple coolers and equipment racks to monitor performances of each cooler and equipment rack. In one embodiment, the controller  402  may be part of a data center design and management system such as system  206 , shown in  FIG. 2 , and the system may be programmed to provide a software tool operable by a user to optimize the chiller water temperature and the cooler airflow using principles described above and further described below. 
       FIG. 5  provides an airflow diagram  502  used in a software tool of one embodiment to provide a representation of the data center  400  to the user and to provide data input blocks for the user to input data to the tool. The airflow diagram  502  may be used to represent multiple equipment racks and coolers in a data center as described above with the racks lumped together and represented in the diagram as a single rack, and the coolers lumped together and represented as a single cooler. The airflow diagram may be presented to the user as part of a graphical user interface. The airflow diagram includes an equipment rack  504 , a cooler  506 , and a chiller  508 . The flow of chilled water (or some other coolant) and the flow of air in the data center are shown in the airflow diagram  502 . Two air mixing blocks  510  and  512  are also shown in the airflow diagram. Mixing block  510  is used to represent the undesirable mixing of bypass air from the cooler with return air from the load, and mixing block  512  is used to represent the undesirable mixing of recirculated air from the load with air from the cooler. 
     The flow diagram  502  includes three air temperature input boxes  514   a ,  514   b  and  514   c , which respectively represent the air temperature at the output of the cooler, at the input of the load, and at the input to the cooler. In one embodiment, a user inserts temperature values into each of the boxes that are representative of average cooler and equipment rack temperature values measured in a data center. In other embodiments, the controller  402  may automatically gather temperature values from sensors placed in a data center and average the values received. In this embodiment, while average values are used for the input temperature to the load, it is actually the maximum inlet temperature that can not be exceeded for proper cooling to occur. In other embodiments, particularly when there are large variations in equipment rack inlet air temperature measurements, it may be desirable to insert a maximum measured value in box  514   b  in place of the average value. The user may also be provided with a number of best-practice-type suggestions that may be implemented in the data center in order to drive maximum rack inlet temperatures closer to the average values. Also, in other embodiments, techniques other than averaging may be used to lump parameters. 
     The flow diagram also includes an input box  516  in which a user inserts a value for the coolant temperature of the facility&#39;s chiller, and the diagram includes an input box  518  in which the Coefficient of Performance (COP), defined as the ratio of the rate of heat removal to the power input of the chiller, is entered. The flow diagram includes boxes  522  and  524  in which characteristics of the equipment racks are entered. In box  522  the total power draw of the load is entered, and in box  524 , the user indicates whether the equipment racks are low, medium or high density racks, which is used to estimate the rack airflow. In another embodiment, the user may be prompted to enter the relative fractions of different IT equipment types (e.g. 1U servers, blade servers, etc.) Value box  528  provides a value for the temperature of air exiting the equipment rack. The value in box  528  is calculated based on the average input temperature, the total load and the total airflow rate of the equipment racks. The flow diagram also includes an input box  530  in the cooler  506 . Input box  530  is used to input the total output in kW of the coolers. 
     After inputting the information into the airflow diagram, the user may press the settings box  526  to enter further information into the tool. Activation of the settings button results in the settings screen  600  shown in  FIG. 6  to be displayed. As with the airflow diagram above, the settings screen may be presented to a user as part of a graphical user interface. The settings screen includes three data input areas including an “r” calculation input area  602 , an air ratio basis input area  604 , and a maximum inlet temperature area  606 . Area  602  is used to determine the r value for optimization calculations to be performed by the tool. The factor r is described in greater detail above. In the embodiment shown, r will have a value between 1.0 and 6.0 depending on the user&#39;s positioning of button  608  in the sliding scale based on characteristics of the data center and the amount of air mixing likely to occur in the data center. In other embodiments, in place of the button and sliding scale, the user may be presented with a set of questions regarding the data center, and the tool produces the r value based on answers provided by the user. 
     Input area  604  of display screen  600  is used to select the basis for air ratio calculations by the tool. The air ratio may be calculated based on temperature inputs or cooler parameters. If cooler parameters are selected as the basis, then either cooler nameplate rating or specified total cooler airflow may be used. With the “nameplate rating” option the total cooler airflow is computed as the product of an assumed airflow per unit power (e.g., cfm/kW) of the cooler and the total cooler capacity (e.g., kW). If the air ratio is based on “temperature inputs,” then the air ratio is computed as AR=(T i −T c )/(T r −T s ). The different options for computing air ratio can be used to provide a “check” on the input data; the current air ratio should be approximately the same number regardless of the calculation method. Input area  606  is used to input the maximum allowable inlet temperature for equipment racks in the data center. Once the data has been entered, the user can activate the “OK” button  610 , at which point the tool processes the information and displays the results screens  700  ( FIG. 7) and 800  ( FIG. 8 ). In different embodiments, the results screens  700  and  800  may be combined as one screen in a graphical user interface or displayed separately. 
     The results screen  700  provides airflow management analysis and includes two pie charts  702  and  704  that respectively display cooler airflow and load airflow. The cooler airflow chart  702  indicates the breakdown of airflow from the cooler that is delivered to the load and bypasses the load. The load airflow chart  704  indicates the breakdown of airflow supplied to the load by that which is supplied directly from the cooler and that which is recirculated from the load exhaust. On results screen  700 , in box  706 , the airflow distribution effectiveness is displayed as a percentage, and in the example provided, the ADE is 92%. The display screen  700  also includes a display box  708  that indicates opportunity for improvement and a display box  710  that provides recommendations. The information displayed in boxes  708  and  710  is based on the ADE calculated. Table 1 provides display information for boxes  708  and  710  based on calculated ADE in one embodiment with ADE expressed as a value between 0 and 1 rather than an a percentage. In other embodiments, other display information may be provided using different ADE thresholds. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Assessment based on Air Distribution Effectiveness 
               
             
          
           
               
                 Air Distribution 
                 Opportunity for 
                   
               
               
                 Effectiveness 
                 improvement 
                 Recommendation 
               
               
                   
               
               
                 0.7 ≦ ADE ≦ 1 
                 Little 
                 Optimize chiller and 
               
               
                   
                   
                 cooler settings as suggested 
               
               
                   
                   
                 below 
               
               
                 0.5 ≦ ADE &lt; 0.7 
                 Some 
                 Consider best 
               
               
                   
                   
                 practices and repeat analysis if 
               
               
                   
                   
                 necessary 
               
               
                   0 ≦ ADE &lt; 0.5 
                 Substantial 
                 Implement best 
               
               
                   
                   
                 practices and repeat analysis 
               
               
                   
               
             
          
         
       
     
     The results screen  800  ( FIG. 8 ) provides an indication of the potential energy savings available if the chilled water temperature and the air ratio are adjusted to optimal values. Screen  800  includes a section  802  that provides operating ranges for the chilled water temperature and the air ratio. In one embodiment, the user can adjust the ranges by inserting values in the boxes shown. Activation of optimization button  808  causes the tool to perform an optimization routine as discussed above to find optimized air ratio and chilled water values for the data center. Depending on a user&#39;s selection in box  806  of user screen  800 , the tool can replace the current user values in the airflow diagram screen  400  ( FIG. 4 ) with the optimized values. Screen  800  also includes a graph  804  indicating the total percentage energy savings that can be achieved if the optimal values are used in the data center. The graph includes two data points  810  and  812 . Data point  810  represents the current settings for air ratio temperature and chilled water temperature, and data point  812  is the optimized settings for air ratio and chilled water as calculated by the tool. As indicated in the graph, if the settings are changed from the current settings to the optimized settings, an energy savings of approximately 38% may be achieved. 
     In the embodiment described above, several display screens of a tool used to optimize the design of a data center are described. In one embodiment, the screens,  500 ,  600 ,  700  and  800  may be combined to be included in one graphical user interface. 
     In another embodiment, screens  900  and  1000  ( FIGS. 9 and 10 ) may be displayed by the tool in addition to screens  500 ,  600 ,  700  and  800  or in place of one or more of screens  500 ,  600 ,  700  and  800 . Screen  900  is similar to screen  500  described above, and like elements are numbered similarly with the elements on screen  500  starting with the numeral  5 , and the elements on screen  900  starting with the numeral  9 . Screen  900  differs from screen  500  in that each of the input or output boxes  514   a ,  514   b ,  514   c , and  516 , and value box  528  are replaced with double value boxes  914   a ,  914   b ,  914   c ,  916  and  928  that indicate current values and optimized values calculated by the tool. Similar to screen  500 , screen  900  includes representations of an equipment rack  904 , a cooler  906 , and a chiller  908 , two mixing blocks  910  and  912  a settings button  926 , an input box  918 , and boxes  922  and  924 . 
     Screen  1000  ( FIG. 10 ) includes pie charts  1002  and  1004  that are similar to pie charts  702  and  704  above, and pie charts  1002  and  1004  respectively display the fraction of cooler airflow that bypasses the load (bypass ratio) and the fraction of IT load air which has been recirculated (recirculation ratio). Screen  1000  also includes a graph  1006 , two slider bars  1008  and  1010 , a reset button  1012 , and a box  1016  that displays the total fractional power savings. Slider bar  1008  may be adjusted by the user to test the effect on power savings of changing the chiller coolant temperature from a present value, and slider bar  1010  may be adjusted by the user to test the effect on power savings of changing the air ratio from a present value. Reset button  1012  resets the coolant temperature and the air ratio to the current value. 
     Graph  1006  shows the total fractional power savings as a function of air ratio. The savings shown result from adjusting the chiller coolant temperature and the air ratio from the current values. On the graph  1006 , point  1016  displays the power savings and air ratio for the values set by slider bars  1008  and  1010 . For a fixed value of chiller coolant temperature, the point  1014  will move in real-time along curve  1018  as the air ratio slider bar  1010  is adjusted. Curve  1018  is bounded by a lower limit bar  1020  and an upper limit bar  1022 . In the example shown in  FIG. 10 , with the coolant temperature at 45.4 degrees as shown, if the AR is adjusted below the lower limit bar  1020 , the inlet temperature to the equipment rack will pass the maximum temperature limit set by the user. If the AR is adjusted above the upper limit bar  1022 , then this increases the AR beyond the current set value and is not meaningful from an energy savings perspective, unless the chiller coolant temperature is also increased. 
     On screen  1000 , for a fixed AR, movement of the coolant temperature slider bar  1008 , will cause the lower limit bar  1020  and the upper limit bar  1022  to move, and the curve  1018  will also adjust in real time on the display. With adjustments of the slider bar  1010 , the pie charts  1002  and  1004  are also updated. In one embodiment, screens  900  and  1000  may be simultaneously displayed and values in both screens may be updated in real-time as the slider bars are adjusted. With embodiments of the invention that use screen  1000 , a user can see the effects in real time of adjusting the coolant temperature and the airflow, while other embodiments discussed above, directly calculate and present optimized values. 
     In embodiments of the invention, as described above, a controller, such as controller  402  in  FIG. 4  can be used to measure temperatures that are used as the input to the tool. In at least one embodiment, the controller may also be configured to control the chiller coolant temperature and/or the airflow from one or more coolers such that the energy optimization process can occur in real time. In this embodiment, the controller can detect changes in temperatures in the facility to ensure that inlet temperatures to equipment racks do not exceed maximum levels. 
     In tools and methods of embodiments discussed above, coolant temperature and cooler airflow are adjusted to maximize power efficiency in a data center. In some servers used in equipment racks in data centers, when the server inlet temperature exceeds a critical temperature (e.g., 77 degrees F.), the servers may increase the speed of internal fans to increase the airflow rate through the servers. The increase in fan speed results in an increase in power draw that could at least partially negate any power savings achieved by increasing coolant temperature and decreasing cooler air flow. In one embodiment that will now be described, the total fractional power savings that is achieved accounts for the increase in power due to an increase in server airflow. In a typical server, an increase in fan speed is directly proportional to an increase in airflow, and a fractional increase fan speed x=RPM 2 /RPM 1 , where RPM 1  equals an initial fan speed, and RPM 2  equals a second or adjusted fan speed. For a particular configuration, the value of x may be a user input dependent on particular equipment types, or x may be calculated by the tool based on the input temperature to equipment racks. 
     Fan power typically increases with the cube of airflow rate, and the fraction of total server fan power increase as a result of an increase of fan speed can be expressed as shown in Equation (9).
 
% Server Fan Power Increase= x   3 −1  Equation (9)
 
     The server fan power can be assumed to be a fixed portion of the total IT load under normal (lower-inlet temperature) conditions. In one embodiment, the fixed portion y is set to 10% and the fan speed can increase by 30% when the inlet temperature exceeds the critical temperature. Values for x and y in different applications may be determined using information from the server manufacturer. The Total Fractional Power Increase (TFPI) as a result of server fan power increase can be determined using Equation (10). 
     
       
         
           
             
               
                 
                   
                     
                       
                         TFPI 
                         = 
                         
                           
                             Server 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Fan 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Power 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Increase 
                           
                           
                             Total 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Cooling 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Power 
                           
                         
                       
                     
                   
                   
                     
                       
                         = 
                         
                           
                             
                               
                                 ( 
                                 
                                   
                                     x 
                                     3 
                                   
                                   - 
                                   1 
                                 
                                 ) 
                               
                               · 
                               y 
                               · 
                               Total 
                             
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             IT 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             Load 
                           
                           
                             
                               P 
                               
                                 c 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             + 
                             
                               P 
                               
                                 f 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     10 
                     ) 
                   
                 
               
             
           
         
       
     
     In Equation 10, P c  and P f  are initial chiller power and cooler fan power respectively. In at least some tools and methods in accordance with the present invention, when calculating the total fractional power savings (TFPS) that can be achieved, the TFPI is subtracted from the power savings that would otherwise be achieved by reducing cooler fan power and increasing chiller coolant temperature. Equation (11) calculates TFPS based on TFPI. 
     
       
         
           
             
               
                 
                   TFPS 
                   = 
                   
                     
                       
                         ( 
                         
                           0.39 
                           ⁢ 
                           
                             
                               
                                 T 
                                 
                                   c 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   2 
                                 
                               
                               - 
                               
                                 T 
                                 
                                   c 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   1 
                                 
                               
                             
                             
                               Δ 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               
                                 T 
                                 ref 
                               
                             
                           
                         
                         ) 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             P 
                             
                               c 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             
                               P 
                               
                                 c 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             + 
                             
                               P 
                               
                                 f 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                         
                         ) 
                       
                     
                     + 
                     
                       
                         { 
                         
                           1 
                           - 
                           
                             
                               ( 
                               
                                 
                                   AR 
                                   2 
                                 
                                 
                                   AR 
                                   1 
                                 
                               
                               ) 
                             
                             3 
                           
                         
                         } 
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             P 
                             
                               f 
                               ⁢ 
                               
                                   
                               
                               ⁢ 
                               1 
                             
                           
                           
                             
                               P 
                               
                                 c 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                             + 
                             
                               P 
                               
                                 f 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 1 
                               
                             
                           
                         
                         ) 
                       
                     
                     - 
                     
                       
                         
                           
                             ( 
                             
                               
                                 x 
                                 3 
                               
                               - 
                               1 
                             
                             ) 
                           
                           · 
                           y 
                           · 
                           Total 
                         
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         IT 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         Load 
                       
                       
                         
                           P 
                           
                             c 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                         + 
                         
                           P 
                           
                             f 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             1 
                           
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     ( 
                     11 
                     ) 
                   
                 
               
             
           
         
       
     
     In at least one embodiment, tools and methods can provide outputs to optimize parameters of a data center to maximize Equation (11) using techniques described above. 
     In embodiments described above, tools are described for evaluating data centers that contain coolers and equipment racks. As readily understood by one of ordinary skill in the art, in other embodiments, processes and systems may be used with cooling providers other than the coolers described herein and with cooling consumers other than equipment racks. 
     In embodiments described herein, the terms coolant and chilled water are used to describe cooling fluids used with chillers and coolers. As understood by one of ordinary skill in the art, chilled water is one type of coolant, and other types of coolant may also be used in embodiments of the invention. Further, in at least one embodiment, multiple chillers may be used in data centers, and models and tools of the invention may lump the chillers into one representative chiller during optimization processes conducted. 
     Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.