Abstract:
Embodiments of the present invention generally relate to the field of data center cooling and energy management. In an embodiment of the present invention, multiple PODs within a data center are controlled by a controller via active dampers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No.: 62/048,423 filed on Sep. 10, 2014, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Data center cooling energy efficiency is critical to successful operation of modern large data centers. The cooling infrastructure can account for an average of 40% of the total data center energy consumption. Adopting methods to raise the efficiency of cooling in data centers can significantly affect the cost of running them, as well as extending their life. The current trend of deploying high heat load density cabinets in data centers necessitates the use of air containment systems. Many of the modern data centers use some kind of air containment systems to achieve high cooling energy efficiency. Air containment in simple terms provides physical separation between the supplied cool air and the cabinet exhaust hot air. This separation of cold and hot air results in cooling energy savings; however, in order to observe the maximum energy savings a proper control system for cooling units is required. Typically, the cooling units get controlled based on a coupled control scheme, wherein both the fan speed and the chilled water valve/compressor speed get controlled based on a single parameter, i.e., return or supply air temperature. These type of control schemes work well for data centers without containment systems but they may not be the best way to control cooling in data centers with containment systems. 
         [0003]    In containment systems, the cooling units and the information technology (IT) equipment are tightly connected with each other via supply air plenum and aisle containment system. Therefore, it becomes important to not only have cold air available at a proper temperature but also have the cooling airflow in the correct amount at the IT equipment inlet. Use of coupled control schemes (i.e. supply air temperature or return air temperature) in containment system does not necessarily guarantee the above conditions and almost always results in either oversupply and/or undersupply of cooling airflow. Oversupply of cooling airflow means waste in cooling energy and cooling capacity of the data center. Undersupply of cooling airflow results in IT equipment starving for cooling airflow, which could result in unreliable operation of IT equipment. 
         [0004]    One common aspect in these decoupled control methods is the use of supply air temperature sensor to control the temperature of the air supplied by the cooling unit. Controlling the amount of air supplied to the data center however varies significantly between the different methods. Some of the ways used to control the amount of air supplied to the data center included using underfloor pressure, server or cabinet inlet temperatures, temperature difference across a containment, and containment pressure. If a data center includes only one containment system, some of these methods may succeed in reaching optimum control. Also, if a data center includes multiple containment systems that all have exactly the same heat load and airflow demand at all times, some of these methods may again succeed in reaching optimum control. However, a typical data center almost always has more than one containment system and it is rare to have the heat load and airflow demand the same for all containment systems at all times. In these situations, the existing control schemes fall short of optimum control for cooling units and result in unwanted cooling airflow bypass, which result in waste of cooling fan energy. 
       SUMMARY  
       [0005]    In an embodiment, the present invention is a data center. The data center comprises a first datacenter POD including a first plurality of rows of cabinets where each of the first plurality of rows of cabinets are adjacent to and share a first cold aisle, the first cold aisle including a first temperature and a first pressure set point; a second datacenter POD including a second plurality of rows of cabinets where each of the second plurality of rows of cabinets are adjacent to and share a second cold aisle, the second cold aisle including a second temperature set point and a second pressure set point; a cold air supply connected to both the first cold aisle and the second cold aisle, the cold air supply providing a cold air flow having both a temperature and a volumetric flow rate associated therewith; a first active damper connected to and between the first cold aisle and the cold air supply; a second active damper connected to and between the second cold aisle and the cold air supply; and a controller connected to the cold air supply, the first active damper, and the second active damper, the controller controlling the temperature of the cold air flow, the controller further controlling the first active damper to partition the volumetric flow rate to approximately achieve the first pressure set point in the first cold aisle, the controller further controlling the second active damper to partition the volumetric flow rate to approximately achieve the second pressure set point in the second cold aisle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a perspective view of a data center with cold aisle containment systems according to an embodiment of the present invention; 
           [0007]      FIG. 2  is a schematic side view of the data center of  FIG. 1 ; 
           [0008]      FIG. 3  is a block diagram of a cooling control system according to an embodiment of the present invention; 
           [0009]      FIG. 4  is a flow chart of the cooling control system of  FIG. 3 ; 
           [0010]      FIG. 5  is a flow chart of the cooling unit fan speed control of  FIG. 4 ; 
           [0011]      FIG. 6  is a flow chart of the supply air temperature set point control of  FIG. 4 ; and 
           [0012]      FIG. 7  is a block diagram of a cooling control system according to an alternative embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    One embodiment of the present invention is a cooling control solution for data centers with multiple cold aisle containment (CAC) PODs. A POD is defined as two rows of cabinets sharing a common cold aisle. The present invention includes a process that controls the amount of cooling airflow supplied by the cooling units and controls the amount of cooling airflow going into each CAC POD. The cooling control scheme closely matches the amount of air supplied by the cooling units to the amount of air required by the IT equipment while maintaining safe cabinet inlet temperatures (within threshold limits), to ensure safe and reliable operation of the IT equipment. The cooling control scheme also monitors and balances the amount of cooling airflow going into each POD. 
         [0014]    Achieving optimum cooling control (lowest energy consumption while maintaining cabinet inlet air temperature within user defined threshold limits) in a data center with containment system can require independent control of cooling fan speed and cooling air temperature. The control scheme of the present invention decouples the control of the cooling unit; using at least one variable to control the amount of air provided by the cooling unit fan to the data center, and at least one other variable to control the temperature of the air supplied by the cooling unit. 
         [0015]    With the use of the present invention, the data center manager/operator can reduce the amount of supplied cooling airflow and hence the cooling fan power consumption, while maintaining proper thermal environment for the IT equipment. The amount of cooling airflow saved can be used to cool additional IT equipment heat load (reclaim lost cooling capacity) that gets commissioned in future and hence helps in extending the life of the data center. The reduction in supplied cooling airflow also optimizes the cooling capacity usage by increasing the return air temperature to the cooling units. 
         [0016]      FIG. 1  is an isometric view of a data center with two CAC PODs for an embodiment of the present invention, which includes cabinet enclosures  1   a - 1   d  that house IT equipment  2   a - 2   d  with cold aisle containment enclosures  3   a - 3   b  deployed for two separate PODs. The data center is cooled using two perimeter cooling units  4   a - 4   b.  Cabinet inlet temperature sensors  5   a - 5   b  are installed at the intake of each cabinet enclosure  1   a - 1   d . Containment pressure sensors  6   a - 6   b  are installed in each cold aisle containment enclosure  3   a - 3   b.  The raised-floor plenum in the data center has underfloor pressure sensors  7  and supply air temperature sensors  8   a - 8   b  installed.  FIG. 2  provides additional details of the data center described in  FIG. 1 . In  FIG. 2 , each of the two PODs described previously have a combination of active damper tiles  9   a - 9   b  and perforated tiles  10   a - 10   b.  The IT equipment  2   a - 2   d  are cooled by the cold supply air  11   a - 11   b  that is flooded into the underfloor plenum, which then enters each POD through its associated active damper tiles  9   a - 9   b  and perforated tiles  10   a - 10   b.  Cold inlet air flow  12   a - 12   d  enters the IT equipment  2   a - 2   d  to cool the IT equipment components and returns to the data center room air as hot exhaust air  13   a - 13   d.  The hot return air  14   a - 14   b  is drawn by the cooling unit fans  15   a - 15   b  through the cooling unit  4   a - 4   b  to be cooled once again and the cycle continues. 
         [0017]      FIG. 3  is a block diagram of an embodiment of the present invention and its different components. The present invention includes an active CAC controller  17  which receives information from all the sensors deployed in the data center; cabinet inlet temperature sensors  5   a - 5   d,  containment pressure sensors  6   a - 6   b,  underfloor pressure sensors  7 , and supply air temperature sensors  8   a - 8   b  as well as a system for receiving information from the active damper tiles  9   a - 9   b  on their position. Active CAC controller  17  interacts with the cooling units&#39; fans  15   a - 15   b  and cooling units chilled water valves  16   a - 16   b  through the cooling units&#39;  4   a - 4   b  and it interacts with a user interface  18  which allows the user to view all the data received by the active CAC controller  17  and input the desired set points for the different variables. The figure also details which specific sensor measurement inputs are used to control the active damper tiles  9   a - 9   b,  cooling units fans  15   a - 15   b  and cooling units chilled water valves  16   a - 16   b.  Input  1 ( i ) from both supply air temperature sensors  8   a - 8   b  and cabinet inlet temperature sensors  5   a - 5   d  is used to control the cooling units chilled water valves  16   a - 16   b  opening through the output signal  1 ( o ). Input  2 ( i ) from the underfloor pressure sensors  7  are used to control the cooling unit fans  15   a - 15   b  speeds through the output signal  2 ( o ). Input  3 ( i ) from the containment pressure sensors  6   a - 6   b  is used to control the active damper tiles  9   a - 9   b  openings through the output signal  3 ( o ). 
         [0018]      FIG. 4  details the flow of an embodiment of the invented process. In step S 2 , the deployed sensors are constantly measuring different variables within the data center. In step S 4 , providing the information collected in step S 2  to the active CAC controller  17  and the user interface  18 . In Step S 6 , the active CAC controller  17  modulates local active damper tiles  9   a - 9   b  based on local POD containment pressure sensor reading  6   a - 6   b  and POD differential pressure set point defined in user interface  18 . In Step S 8 , the active CAC controller  17  modulates cooling units&#39; fans  15   a - 15   b  speed based on underfloor pressure sensor reading  7  and underfloor pressure set point defined in user interface  18 . With airflow balanced between all PODs in the data center and the underfloor pressure set point satisfied, in step S 10  the active CAC controller  17  modulates chilled water valve  16   a - 16   b  opening based on supply air temperature sensor reading  8   a - 8   b  and supply air temperature set point defined in user interface  18 . 
         [0019]    Using the above described process, airflow is matched in each CAC POD based on the IT equipment  2   a - 2   d  airflow demand in the respective POD to the air supplied by the cooling unit fans  15   a - 15   b  which ensures that minimum to none of the air supplied is wasted. This helps achieve the optimum control of the cooling unit fans  15   a - 15   b  which in turn reduces their energy consumption. In addition to energy savings, saving the amount of air flow supplied by the cooling unit fans  15   a - 15   b  also optimizes the cooling capacity usage of the cooling units  4   a - 4   b , allowing to extend the life of the data center and enabling the use of the full designed capacity of the cooling units  4   a - 4   b.    
         [0020]      FIG. 5  details the flow chart for cooling unit fans  15   a - 15   b  speed control. In step S 12 , containment pressure sensor  6   a - 6   b  measurements, and underfloor pressure sensor  7  measurements are reported to the active CAC controller  17 . In Step  14 , the active CAC controller  17  checks if any of the pressure sensors are not working If a pressure sensor isn&#39;t working, an alarm is sent to the user interface  18  to report which sensor is not working in step S 16 . In step S 18 , the active CAC controller  17  checks if the underfloor pressure sensor  7  measurements match the underfloor pressure set point defined in user interface  18 . If not, in step S 20  a proportional integral control loop is used to control the cooling unit fans  15   a - 15   b  to maintain the underfloor pressure set point. If the underfloor pressure set point is satisfied in step S 22 , the active CAC controller  17  checks if all containment pressure sensor  6   a - 6   b  measurements match the containment pressure set point defined in user interface  18  in step S 24 . If the containment pressure sensor  6   a - 6   b  measurements do not match the set point in step S 24 , the active CAC controller  17  checks if the active damper tiles  9   a - 9   b  associated with the cold aisle containment enclosure  3   a - 3   b  that has a mismatch in pressure is at a 100% or 0% opening in step S 26 ; if so, in step S 28 , active CAC controller  17  overrides the initial underfloor pressure set-point condition and controls the cooling unit fans  15   a - 15   b  speed based on the containment pressure sensor  6   a - 6   b  to maintain its set point. 
         [0021]      FIG. 6  details the flow chart for the supply air temperature set point control. In step S 42 , all supply temperature sensors  8   a - 8   b  measurements, and cabinet inlet temperature sensor  5   a - 5   d  measurements are reported to the active CAC controller  17 . In step S 44 , the active CAC controller  17  checks if any of the temperature sensors are not working. If a temperature sensor isn&#39;t working, an alarm is sent to the user interface  18  in step S 45  to report which sensor is not working. In S 46  the active CAC controller  17  checks if a POD door is open. If so, an alarm is sent to the user interface  18  in step S 47  to report which POD door is open and active controller  17  does not make any changes. If no POD door is open, the active CAC controller  17  checks if the supply air temperature sensor  7  measurement is within range of the supply air temperature set point in step S 48 . If not within range, the active CAC controller  17  does not make any changes, to wait for the cooling units chilled water valve  16   a - 16   b  to regulate based on the supply air temperature set point. If within range, in step S 50  the active CAC controller  17  checks if all cabinet inlet temperature sensor  5   a - 5   d  measurements are within range of the cabinet inlet temperature set point. If yes, the active CAC controller  17  does not make any changes. If no, in step S 51  active CAC controller  17  changes the supply air temperature set point defined in the user interface  18  by a delta value defined in the user interface  18 . 
         [0022]    In an another embodiment according to the present invention, the cooling units  4   a - 4   b  illustrated in  FIG. 1  and  FIG. 2  can be replaced with large air handling units that are physically located outside of the data center. However, cold air supply to the data center and warm air exhaust from the data center are in a similar fashion as depicted in  FIG. 1  and  FIG. 2 . 
         [0023]    In an another embodiment according to the present invention, the cooling units  4   a - 4   b  illustrated in  FIG. 1  and  FIG. 2  can be direct expansion (DX) cooling units that utilize a compressor for cooling instead of the chilled water supply. In this case, the cooling capacity is regulated by a compressor speed instead of a chilled water valve opening. 
         [0024]    In an another embodiment according to the present invention, the cooling units  4   a - 4   b  illustrated in  FIG. 1  and  FIG. 2  can be equipped with air-side economization and/or evaporative cooling capability. In this case, the cooling capacity is regulated using supply air set point temperature and outside ambient air condition. 
         [0025]    In an another embodiment according to the present invention, the active damper tiles  9   a - 9   b  are controlled through a damper tile controller  19  instead of the active CAC controller  17 , based on a user specified set point through the user interface  18 . All other aspects of the present invention remain the same.  FIG. 7  is a block diagram of the present invention in the separate described embodiment. 
         [0026]    Note that while this invention has been described in terms of several embodiments, these embodiments are non-limiting (regardless of whether they have been labeled as exemplary or not), and there are alterations, permutations, and equivalents, which fall within the scope of this invention. Additionally, the described embodiments should not be interpreted as mutually exclusive, and should instead be understood as potentially combinable if such combinations are permissive. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present invention. It is therefore intended that claims that may follow be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.