Abstract:
Unlike symmetric power feeds for dual-corded server environments, an asymmetrical power system for high availability environments uses an imbalanced power feed system, allowing lower cost implementation and, in some cases, reduced energy loss in the primary power supply path. One asymmetric power feed uses a direct power feed to supply normal operating power and uses a second system to supply back up power via a switched, conditioned, path with UPS and generator. Because the main power delivery is through the direct line, reliability and power loss are improved.

Description:
BACKGROUND 
       [0001]    Data centers, server farms, and other high availability environments require consistent power to maintain operation. Such environments typically include power from two or more independent sources and servers/server racks typically have two cords so that power can be supplied from either or both sources. 
         [0002]    Each independent source often includes power conditioning, uninterruptible power supplies, generators, etc., to guarantee supply of power. Known implementations use symmetrical arrangements so that both sources supply equal power during normal operation and either source can supply all the required power during an outage or a failure in one source. 
         [0003]    As shown in prior art  FIG. 1 , a data center  10  is shown with server or servers  16  that have dual power cords  18  and  20 . A first power supply path, illustrated on the left side of the drawing, includes a transformer  22  representing a power company connection. A generator  24  is coupled to switch gear  26  for switching power between the transformer  22  and the generator  24  as required. An uninterruptible power supply (UPS)  28  can supply power either via the switch gear  26  or from an internal source, such as batteries and an inverter (not depicted). Mechanical switch gear  30  may switch between the transformer  22  (connection not depicted) and the UPS  28  to supply power to one or more mechanical systems  12 , such as lighting and general air conditioning systems. 
         [0004]    A UPS output switch  32  may be used to selectively provide power to a critical equipment switch  34  from the UPS  32  as needed and as available. The critical equipment switch  34  can selectively route power from either the transformer  22  (connection not depicted) or the UPS  32  to critical mechanical systems  14 , such as primary air conditioning, backup lighting, security equipment, etc. The server  16  is also connected to the UPS output switch  32  and during normal operation the server will draw approximately 50% of its power from this power path. 
         [0005]    An identical power path is shown on the right side of  FIG. 1 . The equipment in locations corresponding to the left side equipment perform the same functions and in the same proportions as their counterparts. The right side equipment includes a transformer  36 , a generator  38 , utility switch gear  40 , a UPS  42 , mechanical switch gear  44 , a UPS output switch  46 , and a critical equipment switch  48 . Obviously, not every data center or server farm follows this exact configuration. Some may have more equipment, such as additional generators, others may have less equipment. 
       SUMMARY 
       [0006]    The prior art symmetric architecture has several shortcomings. One is cost. Since both sides of the architecture can support 100% of the power requirements of the entire system, a system capable of supporting 200% of the system power needs must be purchased, installed and maintained. A second shortcoming is the operating efficiency. Each side is essentially idling at 50% of its design capacity instead of operating at something closer to its target capacity. A third shortcoming is the reliability issues introduced by the failure of the protection equipment itself. In the power path, each piece of equipment and the connections to it have their own reliability issues and increase the likelihood of a power failure due exclusively to the equipment in place that is supposed to protect against a power interruption. 
         [0007]    One additional, significant, shortcoming is the heat dissipation/power loss of the architecture. Every component of both power paths wastes energy in the form of generated heat. This heat loss not only consumes electric power intended for the destination equipment, e.g. servers and mechanical systems, but also requires additional air conditioning capacity and operating cost to remove this waste heat. 
         [0008]    An asymmetric power path architecture feeds raw or lightly conditioned power on one path to meet close to 100% of the operating power requirements for a high availability environment. A second, fully backed up path, similar to one of the paths of the prior art architecture operates at a very low level as a standby source. Because little or no equipment is in the primary path, power loss, heat, and reliability issues are minimized. Because the full backup path operates at a very low level, heat loss is minimized and component lifetime is maximized, improving its reliability as well. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a block diagram of a prior art system for providing power to a high availability environment, 
           [0010]      FIG. 2  is a block diagram of system for providing power to a high availability environment, 
           [0011]      FIG. 3  is a block diagram of another embodiment of a system for providing power to a high availability environment, and 
           [0012]      FIG. 4  is a flow chart of a method for providing power in a high availability environment. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the legal scope of the description is defined by the words of the claims set forth at the end of this disclosure. The detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. 
         [0014]    It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. § 112, sixth paragraph. 
         [0015]    Much of the inventive functionality and many of the inventive principles are best implemented with or in software programs or instructions and integrated circuits (ICs) such as application specific ICs. It is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation. Therefore, in the interest of brevity and minimization of any risk of obscuring the principles and concepts in accordance to the present invention, further discussion of such software and ICs, if any, will be limited to the essentials with respect to the principles and concepts of the preferred embodiments. 
         [0016]      FIG. 2  illustrates an system for supplying power in a high availability environment, that is, an environment where equipment must receive a reliable supply of electrical energy, during any number of different supply power events, such as loss of power, spikes, brown-outs, etc. The high availability environment may support any of a number of information technology environments, such as a server, storage device, server rack, etc., or other high availability environment, for example, a clean room or communication or security facility/equipment. This architecture is particularly applicable to “two corded” systems that are capable of being directly connected to separate power supply paths. 
         [0017]    A server  102 , representing any high availability equipment, is shown with dual power cords  104  and  106 , each cord capable of supporting up to 100% of the power needs of the server  102 . As in the prior art embodiment, the total power needs of the server  102  may be shared between power cords  104  and  106  in any ratio. 
         [0018]    Mechanical systems  108  may support the operation of the secure environment and may include air filters, air conditioning, lighting, etc. Critical mechanical systems  110  may include critical air conditioning, security functions, emergency lighting, etc. Power may supplied via two power paths, one power path  105 , begins at transformer  112  and the other, power path  107 , beginning at transformer  116 . The power path  105  may include little or no conditioning. In this exemplary embodiment, only utility switch gear  114  is included. The utility switch gear  114  may be used to isolate transformer  112  from its various loads, for example, if the power from transformer  112  becomes noisy or off-voltage. The utility switch gear  114  may supply power directly to the server  102  and both the regular and critical mechanical systems  108  and  110 , respectively. 
         [0019]    The power path  107  may include more traditional power conditioning. For example, in this exemplary embodiment, may include utility switch gear  118  that can selectively connect power from transformer  116  or generator  120 . An uninterruptible power supply (UPS)  122  may provide power when power is not available from either the transformer  116  or the generator  120 , as may occur when an outage occurs at the transformer  116  and before the generator  120  can be brought on line. As in the prior art implementation, the mechanical switch gear  124  and critical equipment switch gear  128  can be used to connect back up power from the generator  120  or UPS  122  when main power  116  is not available (connection not depicted). A UPS output switch  126  may further isolate the server  102  as required, or allow connection of additional conditioned sources (not depicted). 
         [0020]    In one exemplary embodiment, 90% or more of the power may be supplied by the power path  105  during normal operation. Because each piece of equipment in both power paths has a certain amount of power loss, especially the active components such as the UPS, when fewer components are present, the more energy efficiency will result. As such, the power path  105  will have a substantially greater energy efficiency than power path  107 . In this respect, the power path  105  may be considered a “green” path, that is, more environmentally friendly, because it reduces power wasted both in generating less heat in the green power path  105  and using less energy to cool the green power path  105 . Supplying more power via the power path  105  will result in greater efficiency, that is, less wasted energy, than if power were supplied equally between the two power paths  105  and  107 . Also, because fewer components are present, reliability will be higher and initial installation cost will be lower, and as mentioned, will require less cooling. In short, overall lifetime cost of ownership is reduced while the ability to supply power on a high availability basis is substantially maintained, especially in environments where power incidents are rare to begin with, such as some urban areas. 
         [0021]      FIG. 3  illustrates another embodiment of an asymmetric power supply architecture for high availability environments. In this embodiment, multiple loads  212  and  224  (or more) each have separate primary power paths  204  and  216 , respectively, and share a common backup power path  228 . Each primary power path includes a transformer  202  and  214  and switch gear  206  and  218  supplying power to respective mechanical systems  208  and  222 . Each primary power path has a UPS  210  and  220  and may include a generator  203  and  215 . As above, the loads  212  and  224  are “two-corded,” that is, capable of operating from either of two sources of power. In some embodiments a ratio of five primary systems to one back up system may be employed. 
         [0022]    The backup power path  228  may include a generator  230 , switch gear  232 , a UPS  236  and mechanical systems  234 . The mechanical systems  234  may be separate from the primary mechanical systems  208  and  222 , or may simply represent a power connection to the primary systems  208  and  222 . Because each primary and the backup power paths are essentially symmetrical, the backup path can fully supply any single load that experiences a power interruption on its primary path. The assumption is that multiple failures in the primary paths are unlikely, as may be determined by broader circumstances, such as past history, likelihood of natural disaster, etc. However, as shown in  FIG. 3 , in the event of a widespread outage, each load  212  and  224  (or more) would have to rely primarily on its respective UPS and generator  210 / 203  and  220 / 215 , although the backup power path  228  could supply some portion of the power to the loads  212  and  224 . In this embodiment, initial equipment costs are lowered and operating losses due to operation of fully redundant dual feed mechanisms are avoided. 
         [0023]      FIG. 4  is a flow chart of an exemplary method  400  of supplying power in a high availability environment. At block  402 , a load  102  is provided, the load  102  having separate and independent first  104  and second  106  electrical power inputs. The load  102  may be one or more servers, security equipment, medical equipment, etc, for which it is desirable to maintain power. At block  404 , a first electrical power path  105  is provided that connects a first utility connection via transformer  112  to the first electrical power input  104 , the first electrical power path supplying more than 90% of the electrical power needs of the load  102  via the first electrical power input  104 . 
         [0024]    At block  406 , a second electrical power path  107  may be provided connecting a second utility connection via transformer  116  to the second electrical power input  106 . The first electrical power path  105 , because it has fewer components, may deliver electrical power at a higher efficiency than the second electrical power path  107 . For this example, efficiency may be defined as a ratio of electrical power delivered at the respective first and second electrical power inputs  104 ,  106  of the load  102  divided by the electrical power delivered by the respective utility connections, e.g. at transformers  112  and  116 . 
         [0025]    At block  408 , the second electrical power path may be provided with an uninterruptible power supply (UPS)  122 . At block  410 , the second electrical power path  107  may be provided with a generator, to provide power when such power is not available at the second transformer  116 . 
         [0026]    At block  412 , the system  100  may be operated asymmetrically, such that the second electrical power path  107  supplies less than 10% of the electrical power needs of the load  102  during normal operation, that is, when power from both sources is available. During operation, because the first electrical power path  105  has both a greater inherent efficiency than the second power path  107  and because the first power path  105  delivers a greater percentage of the power to the load  102 , the overall efficiency of the system  100  is improved over a symmetrical power delivery system, such as that of  FIG. 1 . 
         [0027]    At block  414 , it may be determined that power from one source is not available. At block  416 , when power is not available from one source, the other source may supply 100% of the power needs of the load. For example, after determining that electrical power is unavailable via the first electrical power path  105 , 100% of the electrical power needs of the load  102  may be supplied to the second electrical power input  106  via the second power path  107 . 
         [0028]    This elegant, but simple, architecture acknowledges that may locales have mature power delivery infrastructure and that the quality of the power and the availability are quite good. In such environments, a significant cost savings can be realized by the asymmetric architectures disclosed above, by lowering initial installation costs and by improving overall operating efficiency, and in some cases, improving reliability by removing backup components and their own associated failure rates. 
         [0029]    Although the foregoing text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possibly embodiment of the invention because describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention. 
         [0030]    Thus, many modifications and variations may be made in the techniques and structures described and illustrated herein without departing from the spirit and scope of the present invention. Accordingly, it should be understood that the methods and apparatus described herein are illustrative only and are not limiting upon the scope of the invention.