Abstract:
Described is an adaptive automatic computer room air conditioner (CRAC) or computer room air handler (CRAH, CRAC and CRAH is referred interchangeably in this article) group control method. This method automatically controls each HVAC unit&#39;s on/off status, return temperature set point, fan speed or cooling valve position to secure the data center thermal environment for server&#39;s secure running and minimize the cooling energy use. The method creates a comprehensive feedback control loop between temperature sensor network, data center environment and CRACs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/269,913, filed Dec. 18, 2015, the entire contents of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to mechanical cooling system optimal control and energy efficiency. 
       BACKGROUND OF THE INVENTION 
       [0003]    Data centers are one of the largest and fastest growing consumers of electricity in the United States. In 2013, U.S. data centers consumed an estimated 91 billion kilowatt-hours of electricity—enough electricity to power all the households in New York City twice over—and are on-track to reach 140 billion kilowatt-hours by 2020. To ensure safe operation of a data center, its cooling system usually is over sized and runs excessively to keep it as cool as possible. This however sacrifices cooling efficiency and cooling energy consumption therefore skyrockets. A smart cooling system control logic which drives the cooling system to provide just the right level of cooling so safety may be guaranteed with minimum cooling energy use, is desired. 
         [0004]    There are a few companies who propose control logic that aims to address the above issues. Some of them adapt several inherently conflicting indices in their control logic, resulting in less efficient control results. Some use a single HVAC unit to address hot spots, resulting in unsatisfactory thermal conditions. Some are specific to a certain type of server, rack or cooling system. Still some require human intervention and are not automatic enough. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the present invention, there is provided a smart adaptive cooling system control algorithm. The algorithm uses rack cooling index over temperature (RCIHI) to determine the existence of hot spots and maintains the RCIHI at a desired level. The logic generates cooling request to other computer room air conditioners (CRACs) when hot spots happen or persist. The purpose is to try to get extra cooling from other CRACs. In absence of hot spots, cooling requests are recalled gradually. In absence of cooling request, the CRAC adjusts its control target to maintain the RCIHI at the desired level. Each CRAC runs the control algorithm independently. 
         [0006]    In some embodiments, the described systems provide a dynamically adaptive algorithm to optimally control each component of the cooling system, including but not limited to HVAC unit&#39;s on/off status, return air temperature, supply fan speed, and cooling valve. 
         [0007]    In some embodiments, a logic that uses a special index to determine the thermal health of a data center and for control logic is provided. In some embodiments, this special index is used to control the computer room air conditioning systems. In some embodiments, an algorithm that networks all available HVAC units to help eliminate hot spots is provided. In some embodiments, a generic control logic which can be adapted to any data centers, independent of types of servers, racks, and cooling equipment is provided. In some embodiments, a control logic that minimizes cooling energy consumption and ensures normal operation for data centers is provided. In some embodiments, a fully automatic control logic without human intervention is provided. 
         [0008]    In some embodiments, an adaptive automatic computer room air conditioners (CRAC) master control method for optimizing mechanical cooling systems and minimize cooling energy consumption in data centers comprises determining a rack cooling index over temperature (RCIHI) for one or more racks under control of a first CRAC, determining the existence of hot spots using the determined RCIHI, maintaining the RCIHI at a desired level by generating cooling requests to one or more other CRACs in addition to the first CRAC when hot spots occur or persist, and recalling the cooling requests when the hotspot is eliminated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent, detailed description, in which: 
           [0010]      FIG. 1  is a plan view of a data center in accordance with the invention; 
           [0011]      FIG. 2  is an elevation view of a computer room air conditioning unit shown in  FIG. 1 ; and 
           [0012]      FIGS. 3A-3C  are flow charts of the adaptive control process. 
       
    
    
       [0013]    For purposes of clarity and brevity, like elements and components will bear the same designations and numbering throughout the Figures. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  is a plan view of a data center  1 . The data center  1  includes one or multiple racks (rack  2 ) and CRAC units (CRAC unit  3 ). A rack  2  consists of one or multiple computer equipment. For example, there are  25  CRACs and  10  columns of racks, with  15  racks each column in  FIG. 1 . This method can be used in rooms with any numbers of CRAC units. 
         [0015]      FIG. 2  is an elevation view of a CRAC unit  3  shown in  FIG. 1 . Return air  4  from internal space of the data center  1  is drawn by the supply fan  6  through the top of the unit. After passing through the cooling coil  5 , it is cooled and becomes cool supply air  8 . Inside the cooling coil  5  runs chilled water, refrigerant or other cold media, the flow of which is regulated by the cooling valve  7 . Temperature of the return air  4  (RAT) usually is the control target of the CRAC unit  3 . Speed of the supply fan  6  or the cooling valve  7  or another means is adjusted to vary the cooling output of the CRAC unit  3  and maintain the control target, in this case the RAT, at a desired level. 
         [0016]      FIGS. 3A-3C  are flow charts of the smart adaptive cooling system control logic that&#39;s run by each CRAC unit  3 . It is a repetitive control process  9  based on several concepts: RCIHI of a CRAC&#39;s direct control racks, RCIHI of a single rack  2  and cooling request. RCI (Rack Cooling Index) is a best practice performance metric for quantifying the conformance with thermal data center standards such as ASHRAE and NEBS. The RCI metric compresses the intake temperatures (measured or modeled) into two numbers: RCIHI and RCILO (Rack Cooling Index Under Temperature). The two indices are measures of the equipment room health at the high (HI) and at the low (LO) end of the temperature range, respectively. RCIHI can be calculated for multiple racks or a single rack. A level m cooling request is defined as: when a rack has to get extra cooling from its level m (m is an integer) CRAC because its own RCIHI or the RCIHI of the direct control area it is in, is below the setpoint, and all of the m-1 CRAC before the level m CRAC in the CRAC priority vector reaches the maximum cooling output, the cooling request is a level m cooling request. 
         [0017]    The control logic begins by turning on a CRAC and setting operational parameters to default values at box start  10 . RCIHI of all of the racks under the CRAC&#39;s direct control is measured and calculated at box measure RCIHI  11 . At box compare RCIHI  12 , the actual RCIHI of the CRAC&#39;s direct control area is compared to the setpoint. 
         [0018]    When the actual RCIHI is above its setpoint, if at least one rack in the CRAC&#39;s direct control area has a level  2  or higher cooling request (at box cooling request exists  13 ), generate cooling request recall based on appropriate rules, and send the recall to target CRAC at box generate cooling request recall  14 , and goes on to box measure CRAC control target  20 . But if no cooling request exists, if the CRAC&#39;s cooling output is not at maximum (compared at box CRAC at max cooling  15 ), change the control target of the CRAC so its cooling output decreases (for example raise RAT setpoint appropriately but capped at the allowable high limit (at box decrease cooling  16 ). Otherwise, goes on to box measure CRAC control target  20 . 
         [0019]    When the actual RCIHI is below its setpoint, if the CRAC&#39;s cooling output is not maxed out, increases the cooling output at box increase cooling  17  and move to the box measure CRAC control target  20 . Otherwise, the area has to get extra cooling from other CRACs. In order to do so, at box find highest RCIHI rack  18 , identify the rack with the highest single rack RCIHI in the CRAC&#39;s direct control area, the highest level cooling request of the identified rack, and the target CRAC associated with the highest level cooling request. The logic shall keep generating a higher level cooling request at box generate cooling request  26  if the target CRAC of the existing top cooling request is at its maximum cooling output. If cooling output of all of the CRACs have reached maximum, but hot spots still exist, a warning should be generated at box warning generation  19 . 
         [0020]    After measuring the CRAC control target at box measure CRAC control target  20 , if the CRAC does not have any cooling request from any rack, the CRAC maintains the control target at box maintain control target  20 . Otherwise system checks whether the CRAC receives any cooling request recall at box cooling request recall  21 . If no, increase cooling output of the 
         [0021]    CRAC occurs based on the control logic of cooling request at box adjust cooling by control target  23 . If yes, perform the recall at box perform recall  22 . If the top level cooling request is recalled, reduce CRAC cooling output based on the control logic of recalling cooling request at box reduce cooling by recall  24 . Otherwise, continue increasing CRAC cooling output based on the control logic of the top level cooling request at box increase cooling by top cooling call  25 . After all of the above steps, current control cycles ends. A new control cycle starts from box measure RCIHI  11  again. 
         [0022]    Each CRAC runs the above control algorithm independently. 
         [0023]    Thus, in summary, it can be seen that what is provided is a smart adaptive cooling system control algorithm. The algorithm uses RCIHI to determine the existence of hot spots and maintains the RCIHI at a desired level. The logic generates cooling request to other CRACs when hot spots happen or persist. The purpose is to try to get extra cooling from other CRACs. In absence of hot spots, cooling requests are recalled gradually. In absence of cooling request, the CRAC adjusts its control target to maintain the RCIHI at the desired level. 
         [0024]    Each CRAC system can include one or more of processors for running the control algorithm and software. The processor may be any suitable type of processor capable of communicating with the other components of the system in order to execute computer-readable instructions and to cause system to carry out actions in accordance with the instructions. For example, the processor may access a computer program (e.g., software) that may be stored on storage and execute the program to cause the system to perform various actions in accordance with the program. In some embodiments, a computer program or other instructions executed by processor may be stored on any transitory or non-transitory computer-readable storage medium readable by processor. 
         [0025]    The CRAC system may also include any suitable device capable of transmitting and receiving signals over a network, such as a network interface chip or card. The CRAC system may also include storage that can be any suitable device the provides storage, such as an electrical, magnetic or optical memory including a RAM, cache, hard drive, CD-ROM drive, tape drive or removable storage disk. Software may be stored in storage and executed by the processor, may include, for example, the programming that embodies the functionality of the methods, techniques, and other aspects of the present disclosure (e.g., as embodied in the computers, servers and devices as described above). 
         [0026]    The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated. 
         [0027]    Although the disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims.