Patent Publication Number: US-2015061384-A1

Title: Shared Backup Power For Data Centers

Description:
BACKGROUND 
     Data centers are facilities used to house and operate computing resources such as computers, processors, servers, telecommunications equipment, data storage systems, and so forth. Data centers may be used to provide services such as large-scale internet applications. Data centers may also be used to provide infrastructure services to customers who may implement their own applications using the resources provided by data centers. Data centers are increasingly critical to various types of computing activities, services, and applications. 
     The reliability and continuous availability of data center equipment are critically important. Various equipment redundancies are typically implemented within data centers to ensure continuous availability. In particular, redundant power sources are provided to ensure continuous operation during power failures or outages. 
     Many data centers may include multiple resource zones, each having its own infrastructure and support system. Electrical power for the equipment within a resource zone is provided by an uninterruptable power supply (UPS). The UPS conditions alternating current (AC) power and includes an inverter for generating AC power from associated direct current (DC) batteries. 
     Normally, the UPS is powered from AC electric mains provided by a power utility. Upon a failure or outage of the AC electric mains, the UPS may temporarily draw DC power from its associated batteries for a short period of time to generate AC power while backup generators are started. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical components or features. 
         FIG. 1  is a figurative drawing of a data center having multiple resource zones, where each resource zone has a dedicated UPS and associated batteries that are potentially shared between the UPS&#39;s. 
         FIG. 2  is a figurative drawing of a data center having multiple resource zones. Each resource zone has a dedicated UPS and associated batteries. In addition, the data center has an additional set of batteries that are potentially shared between the UPS&#39;s of the different resource zones. 
         FIGS. 3 ,  4 , and  5  are block diagrams illustrating example configurations that may be used within data centers to provide backup power to resource zones of the data centers. 
         FIG. 6  is a flow diagram illustrating an example method of operating a data center using shared UPS power storage elements. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure describes systems and techniques for providing backup power to computing resources and other equipment within a data center. The data center has multiple resource zones supported by infrastructures that are generally independent of each other, so that failures relating to one resource zone do not affect the ongoing operations of other resource zones. 
     Various types of computing resources are located within each of the resource zones. With regard to power distribution, each resource zone has an uninterruptable power supply (UPS) that provides power to the computing resources within the zone. A set of batteries or other energy storage elements are located in the resource zone along with the UPS. Each resource zone may also have a backup generator for providing power during power outages. 
     The UPS within a particular resource zone normally receives alternating current (AC) power from an electric mains of a power utility. Upon failure of the electric mains, the UPS receives AC power from a backup generator that is dedicated to the resource zone. In the time between failure of the AC mains and startup of the backup generator, the UPS draws direct current (DC) power from its associated batteries and uses an electrical inverter to generate AC power for the equipment of the resource zone. 
     A power bus may be provided to allow sharing of DC power between the UPS&#39;s of different resource zones. The power bus may extend between and/or pass through each of the resource zones, and may be configured to provide a common connection between the DC outputs of the UPS batteries of the different resource zones. The UPS batteries of the different zones may therefore be operated in parallel, to increase the length of time that a particular UPS may operate from DC power. This may be useful in various situations, and may allow battery capacities to be reduced overall and/or within individual resource zones. 
     In certain embodiments, the power bus may be switched, and control logic may be provided to selectively direct DC power from one resource zone to another based on need. For example, DC power may be directed from a first resource zone to a second resource zone in response to a detected depletion of the batteries of the second resource zone. 
       FIG. 1  shows an example of a data center  100  in which the described techniques may be implemented. The data center  100  has a plurality of resource zones  102  in different areas or locations of the data center  100 . Each resource zone  102  may, for example, comprise a room of the data center. As another example, each resource zone  102  may comprise a specific area of the data center. In general, each resource zone is supported by an independent local infrastructure, so that a failure relating to one of the resource zones does not affect other resource zones. 
     Each resource zone  102  has or contains multiple computing resources  104 . The resources  104  may include computers, processors, servers, storage devices, networking equipment, telecommunications equipment, control equipment, support equipment, and so forth. The computing resources  104  are typically housed in racks, which are arranged in rows within the data center  100 . 
     Each resource zone  102  has an uninterruptable power supply (UPS)  106  and associated UPS power storage elements  108 . The power storage elements  108  may comprise sets of batteries or other power storage mechanisms, including chemical and kinetic power storage devices. For example, each UPS storage element  108  may comprise one or more batteries connected to provide direct current (DC) power to the associated UPS  106 . The UPS  106  charges the batteries during normal mains-powered operation, and may draw upon the batteries when conditioning alternating current (AC) mains power or generator-provided AC power. Alternatively, each UPS power storage element or set  108  may comprise a flywheel energy storage unit. 
     Each resource zone  102  may have its own UPS  106  and corresponding set of storage elements  108 , which may be physically located within the resource zone  102 . 
     Each resource zone  102  may also have its own dedicated backup generator  110  or set of backup generators  110  for use during power outages or interruptions. During normal operation, the UPS  106  operates from AC mains provided by an electric power utility. In the case of an AC mains failure, AC power may be provided by the backup generator  110 . In the interim between AC mains failure and startup of the backup generator  110 , the UPS  106  may generate AC power based on DC power drawn from the storage elements  108  associated with the UPS  106 . The UPS  106  may have one or more inverters (not shown) that are used to generate AC power from DC power. 
     In the described embodiment, a common power bus  112  extends between and into each of the resource zones  102  to provide a common connection between the UPS storage elements  108  of the multiple resource zones  102 . The common power bus allows for DC power sharing between the UPS&#39;s of the resource zones. 
     Generally, each of the UPS power storage elements  108  has a power output comprising multiple power terminals, lines, or connections. For example, each set of the storage elements  108  may have a positive terminal, a negative terminal, and a ground terminal. The power bus  112  may have conductors corresponding to each of the multiple terminals, and may be connected in such a way that corresponding terminals of the multiple storage elements  108  are connected in common. Multi-conductor DC power bus bars may be used for this purpose. 
     The interconnection of the UPS storage elements shown in  FIG. 1  may be useful in various situations. As an example, it may happen at the beginning of a power outage that most of the generators start up within an expected startup time, while one of the generators does not start as expected. In a situation like this, the UPS storage elements associated with the resource zones that are receiving backup power from their backup generators may be used to supplement the power of the storage element within the resource zone of the malfunctioning generator. This may allow more time for technicians to troubleshoot and/or manually start the malfunctioning generator. 
     As another example, it may happen that a bank of UPS storage elements associated with a particular resource zone fails or becomes depleted in an unusually or abnormally short time. In this situation, the UPS storage elements of the other resource zones may be drawn from to supplement or replace the power that would otherwise have been provided by the malfunctioning or depleted storage elements. 
     As yet another example, it may happen that a UPS associated with a particular resource zone fails. In this situation, the power storage elements of that zone may be used to extend DC power availability to the UPS&#39;s of other zones. 
     Furthermore, it may be possible because of the shared arrangement of UPS power storage elements to reduce the number of storage elements that are located within each of the resource zones. Normally, UPS batteries within a particular zone are sized to accommodate anomalous conditions that are unlikely to occur simultaneously in multiple resource zones. With the arrangement described above, the batteries of different resource zones may be used in combination to supplement an individual zone that is experiencing an unusual or unique condition. 
       FIG. 2  shows an alternative implementation of the data center  100 . In addition to the UPS storage elements  108  that are dedicated to corresponding UPS&#39;s  106  and located within the same resource zones  102  as the associated UPS&#39;s  106 , additional or supplemental power storage elements  202  may be located within the data center  100 . The supplemental power storage elements  202  may comprise one or more chemical power storage devices such as battery banks or kinetic energy storage devices such as flywheels that are not collocated with or directly associated with corresponding UPS devices. The supplemental power storage elements  202  may be located within one of the resource zones  102  or at a separate or central location with the data center  100 , possibly apart from any UPS units of the data center  100 . The common power bus  112  connects the supplemental power storage elements  202  in common with each of the dedicated power storage elements  108 . 
     The supplemental power storage elements  202  may be useful in the scenarios described above, to supplement the power provided by the dedicated power storage elements  108 . In certain implementations, the availability of the supplemental storage elements  202  may make it possible to reduce the number or capacity of the dedicated power storage elements  108  that are located in each of the resource zones  102 . For example, the dedicated power storage elements  108  may be sized to accommodate normal or expected failure sequences, such as might be based on an assumption that the backup generators  110  will be started within an expected time after the beginning of an AC mains power failure. In the case that one or more of the backup generators  110  does not start as expected, the supplemental storage elements  202  may be used to provide additional DC power for the UPS  106  of the resource zone  102  where the backup generator  110  has failed to start. 
       FIG. 3  shows further details regarding an implementation of a data center backup power system  300 . The system  300  includes a plurality of UPS&#39;s  106  as described above. Each UPS  106  is associated with and dedicated to a particular resource zone, and may be located at or within the resource zone. Each UPS  106  provides conditioned power and backup power to the computing resources within the associated resource zone. 
     Each UPS  106  normally receives AC power from a power utility mains. In addition, a backup generator  110  is associated with and/or dedicated to each of the resource zones and the UPS&#39;s  106  of the resource zones. Upon failure or outage of the AC power mains, the generator  110  automatically starts within a period of time such as 45-120 seconds. During the interim between AC power mains failure and startup of the generator  110 , each UPS  106  draws power from one or more associated or dedicated power storage elements  108 , which in this example are illustrated as battery sets, groups, or banks. Each battery set may comprise one or more batteries or battery elements. Although  FIG. 3  is illustrated as being implemented with chemical-based battery sets, other implementations may use other types of storage elements in place of the battery sets. For example, kinetic energy storage devices may be used in place of the battery sets in certain embodiments. 
     In the embodiment of  FIG. 3 , each UPS  106  has a set  302  of power storage elements, which may comprise a number n of individual storage elements  108 . Each set  302  of power storage elements is located at or within its associated resource zone. Each set  302  of storage elements  108  is connected through power switches  304  with the common power bus  112 . The common power bus  112  extends into each of the resource zones to connect between the storage elements  108  of the different resource zones. 
     Control logic  306  may be provided to selectively direct and/or connect DC power from the storage element set  302  of one or more of the resource zones to the storage elements and/or UPS&#39;s  106  of one or more others of the resource zones. In some cases, the control logic  306  may monitor the power levels of the storage element sets  302 . In response to detecting depletion of power in one of the storage element sets  302 , the control logic  306  may direct or connect power to the depleted storage element set  302  and its associated UPS  106  from another of the storage element sets  302 . This may happen, for example, when the backup generator  110  associated with a particular UPS  106  fails to start as expected, and additional DC power is needed to sustain the UPS  106  while the backup generator  110  is started manually. 
       FIG. 4  shows details regarding another implementation of a data center backup power system  400 . The system  400  includes a plurality of UPS&#39;s  106  as described above. Each UPS  106  is associated with and dedicated to a particular resource zone, and may be located at or within the resource zone. Each UPS  106  provides conditioned power and backup power to the computing resources within the associated resource zone. 
     Each UPS  106  normally receives AC power from a power utility mains. In addition, a generator  110  is associated with and/or dedicated to each of the resource zones and the UPS&#39;s  106  of the resource zones. Upon failure or outage of the AC power mains, the generator  110  automatically starts within a period of time such as 45-120 seconds. During the interim between AC power mains failure and startup of the generator  110 , each UPS  106  draws power from one or more associated and dedicated power storage elements  402 . Each storage element may comprise one or more batteries, one or more kinetic energy storage devices, other types of energy storage devices, or sets of energy storage devices. For example, a single flywheel-based energy storage device may be associated with each of the UPS&#39;s  106 , in each of the resource zones. Each dedicated storage element  402  is located at or within its associated resource zone. 
     Each of the dedicated storage elements  402  is connected through power switches  404  with the common power bus  112 . The common power bus  112  extends into each of the resource zones to connect between the storage elements  402  of the different resource zones. 
     In addition to the dedicated storage elements  402 , which are collocated and associated directly with respective UPS units, the system  400  may include one or more shared or supplemental storage elements  406 , which may comprise one or more batteries, one or more kinetic energy storage devices, other types of energy storage devices, or sets of energy storage devices. 
     Control logic  408  may be provided to selectively direct and/or connect DC power from the supplemental storage elements  406  to one or more of the dedicated storage elements  402  and/or UPS&#39;s  106 . In some cases, the control logic  408  may monitor the power levels of the storage elements  402 . In response to detecting depletion of power in one of the dedicated storage elements  402 , the control logic  408  may direct power to the depleted storage element  402  and its associated UPS  106  from the supplemental storage elements  406 . This may happen, for example, when the backup generator  110  associated with a particular UPS  106  fails to start as expected, and additional DC power is needed to sustain the UPS  106  while the backup generator  110  is started manually. 
       FIG. 5  shows details regarding another implementation of a data center backup power system  500 . The system  500  includes a plurality of UPS&#39;s  106  as described above. Each UPS  106  is associated with and dedicated to a particular resource zone, and may be located at or within the resource zone. Each UPS  106  provides conditioned power and backup power to the computing resources within the associated resource zone. 
     Each UPS  106  normally receives AC power from a power utility mains. In addition, a generator  110  is associated with and/or dedicated to each of the resource zones and the UPS&#39;s  106  of the resource zones. Upon failure or outage of the AC power mains, the generator  110  automatically starts within a period of time such as 45-120 seconds. During the interim between AC power mains failure and startup of the generator  110 , each UPS  106  draws power from one or more power storage elements. 
     In the example of  FIG. 5 , the power storage elements may include one or more dedicated power storage elements  502  and one or more shared power storage elements  504 . Each dedicated power storage element  502  is associated with and located at or within a corresponding resource zone to provide temporary operating power to the UPS  106  associated with that zone. The shared power storage element  504  may be commonly located, such as at a central location within the data center or at any other location. The power bus  112  extends from the shared power storage element  504  to each of the resource zones. 
     Some of the resource zones and their UPS&#39;s  106  may not be associated with dedicated power storage elements. In this example, two of the UPS&#39;s  106  do not have dedicated or directly associated power storage elements  502 . Rather, these UPS&#39;s  106  are connected by the power bus  112  to receive temporary power directly from the shared power storage element  504 . 
     Each of the storage element  502  and  504  may comprise one or more batteries, one or more kinetic energy storage devices, other types of energy storage devices, or sets of energy storage devices. 
     The dedicated storage element  502  may be connected through a power switch  506  with the common power bus  112 . Control logic  508  may be provided to selectively direct and/or connect DC power from the shared power storage element  504  to the dedicated storage element  502  and/or UPS&#39;s  106 . In some cases, the control logic  508  may monitor the power levels of the dedicated storage element  502 . In response to detecting depletion of power in the dedicated storage element  502 , the control logic  508  may direct power to the depleted storage element  502  and its associated UPS  106  from the shared storage element  504 . 
       FIG. 6  illustrates an example method  600  of operating a data center in accordance with the techniques described above. An action  602  comprises operating a plurality of computing resources within different resource zones of a data center. The resource zones may in some cases comprise physically different areas or rooms of the data center, and may be locally supported by independent infrastructures. 
     An action  604  comprises supplying operating power to the computing resources from UPS&#39;s located respectively in the different resource zones. The UPS&#39;s may be configured to receive AC power from an AC power mains and/or from an AC generator. The generator may be used to supply AC power upon failure of the AC power mains. 
     An action  606  comprises providing temporary power to the UPSs from a plurality of power storage elements, including one or more power storage elements located in each of the different resource zones. This may be performed during initial stages of a power outage, before backup generators have been started. 
     An action  608  comprises sharing the temporary power from the power storage elements located in the different resource zones among the UPS&#39;s located in the different resource zones. In some embodiments, this may be accomplished by use a power bus that extends between the power storage elements. In some cases, the action  608  may comprise selectively directing the temporary power provided by a first of the power storage elements to the uninterruptable power supply associated with a second of the power storage elements in response to power depletion of the second of the power storage elements. 
     Although the subject matter has been described in language specific to structural features, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features described. Rather, the specific features are disclosed as illustrative forms of implementing the claims.