Abstract:
A modular data center includes: a rack which houses an electronic device; a blower device capable of switching a flowing direction of air and configured to feed the air into the rack; a space housing a moisture absorbent; an in-rack temperature detector which detects a temperature inside the rack; a dew-point temperature detector which detects a dew-point temperature of outside air; and a controller. The controller receives signals inputted from the in-rack temperature detector and the dew-point temperature detector, and controls shutters and the blower device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of International Patent Application No. PCT/JP2013/057592 filed Mar. 18, 2013 and designated the U.S., the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The embodiments discussed herein are related to a modular data center. 
       BACKGROUND 
       [0003]    With the advent of an advanced information society in recent years, an amount of data treated by computers has been increasing and there has been a growing need for data centers which perform total management of numerous computers. 
         [0004]    A data center in general is equipped with a building constructed on a huge land, a large-scale air-conditioning system, and a large-scale electric system. For this reason, such a data center needs a long time to be completed and, therefore, has a difficulty in quickly responding to an increase or decrease in demand. Against this background, modular data centers have been developed and put to practical use. Here, a typical modular data center is formed by arranging racks which house computers (servers), together with an air-conditioning system and an electric system, in a unitized structure of a given size called a container. 
         [0005]    Meanwhile, each computer generates a large amount of heat in association with operation. A rise in temperature inside the computer may cause a malfunction, a failure, or a decline in performance and it is therefore preferable to provide a measure for cooling the computers. In a typical data center, low-temperature air is supplied into a room by using an air-conditioning machine (an air conditioner) and then the air in the room is introduced into the computers by cooling fans (blowers), thereby cooling electronic components inside the computers. 
         [0006]    In recent years, there has been an ever-growing demand for reduction in power consumption of data centers from the viewpoint of energy conservation. For this reason, there are many modular data centers which adopt an outside air cooling method designed to cool computers by use of outside air. A modular data center of this type does not have to use a large-size air conditioning machine which consumes a large amount of electricity. As a consequence, power used for cooling the computers is reduced. 
         [0007]    Modular data centers adopting the outside air cooling method include one configured to introduce low-temperature outside air directly from an intake port into a container, and one configured to cool the air in a container with outside cool air by using a heat exchanger. 
         [0008]    Note that techniques relating to the present application are disclosed in Japanese Laid-open Patent Publication Nos. 2012-53747 and 2012-97945. 
       SUMMARY 
       [0009]    According to an aspect of the disclosed technique, there is provided a modular data center which includes: a structure provided with an intake port and an exhaust port, the ports being connected to outside; a first shutter provided to the intake port, and made openable and closable; a second shutter provided to the exhaust port, and made openable and closable; a rack disposed in the structure and configured to house an electronic device; a blower device capable of switching a flowing direction of air, the blower device being disposed in the structure and configured to feed the air into the rack; a first space provided between the first shutter and the rack; a second space provided on an opposite side of the rack from the first space; a third space provided between the second space and the second shutter; a fourth space located adjacent to the second space and the third space, and housing a moisture absorbent inside; a third shutter provided between the second space and the third space, and made openable and closable; a fourth shutter provided between the second space and the fourth space, and made openable and closable; a fifth shutter provided between the third space and the fourth space, and made openable and closable; an in-rack temperature detector configured to detect a temperature inside the rack; a dew-point temperature detector configured to detect a dew-point temperature of outside air; and a controller configured to receive signals inputted from the in-rack temperature detector and the dew-point temperature detector, and to control the first shutter, the second shutter, the third shutter, the fourth shutter, the fifth shutter, and the blower device. 
         [0010]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0011]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]      FIG. 1  is a schematic side view illustrating an example of a modular data center according to an embodiment; 
           [0013]      FIG. 2  is a block diagram illustrating an airflow control system of the modular data center according to the embodiment; 
           [0014]      FIGS. 3A and 3B  are flowcharts illustrating airflow control in the data center of the embodiment; 
           [0015]      FIG. 4  is a first view illustrating airflow when a temperature inside a rack is equal to or below a dew-point temperature of outside air; 
           [0016]      FIG. 5  is a second view illustrating airflow when the temperature inside the rack is equal to or below the dew-point temperature of the outside air; 
           [0017]      FIG. 6  is a first view illustrating airflow when the temperature inside the rack is above the dew-point temperature of the outside air; 
           [0018]      FIG. 7  is a second view illustrating airflow when the temperature inside the rack is above the dew-point temperature of the outside air; and 
           [0019]      FIG. 8  is a view illustrating airflow when air in a first hot aisle has a temperature equal to or above a predetermined temperature and has a humidity equal to or below a predetermined humidity. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0020]    Before descriptions are provided for an embodiment, a prelude for facilitating the understanding of the embodiment will be explained below. 
         [0021]    As described previously, many modular data centers adopt the outside air cooling method. However, the outside air cooling method has the following problem. 
         [0022]    When a modular data center is installed in a cold region, for example, a temperature of a computer in a stopped state may fall below an outside temperature. In such a case, if outside air is introduced into a container, dew condensation may occur inside the computer and may lead to a failure such as a short circuit when the computer is operated. 
         [0023]    The following embodiment will describe a modular data center which may avoid occurrence of a failure of an electronic device attributed to dew condensation. 
       EMBODIMENT 
       [0024]      FIG. 1  is a schematic side view illustrating an example of a modular data center according to an embodiment, and  FIG. 2  is a block diagram illustrating an airflow control system of the data center. 
         [0025]    In the modular data center illustrated as an example in  FIG. 1 , a cooling fan unit  12  and a plurality of racks  13  are arranged inside a container  10  having a rectangular parallelepiped shape. 
         [0026]    Of two wall surfaces of the container  10  opposed to each other, an intake port to which a shutter  11  is attached is provided on one wall surface while an exhaust port to which a shutter  16  is attached is provided on the other wall surface. 
         [0027]    The shutters  11  and  16  are opened and closed by signals outputted from a controller  30 . A space inside the container  10  connects to an outside space when one or both of the shutters  11  and  16  are opened. The space in the container is closed off to the outside space when both of the shutters  11  and  16  are closed. 
         [0028]    Servers  13   a  are housed in each of the racks  13 . Moreover, each rack  13  is provided with a temperature sensor  13   b  which detects a temperature of the servers  13   a.  An output from the temperature sensor  13   b  is transmitted to the controller  30 . Here, each server  13   a  is an example of an electronic device. Other electronic devices such as storage units or power units may be housed in the racks  13 . Meanwhile, the temperature sensor  13   b  is an example of an in-rack temperature detector. 
         [0029]    A plurality of cooling fans  12   a  are provided to the cooling fan unit  12 . Each of the cooling fans  12   a  may be switched to rotate forward or reverse and its drive is controlled by the controller  30 . In this embodiment, rotation of the cooling fans  12   a  which causes air to flow from the cooling fan unit  12  toward the racks  13  is referred to as forward rotation while rotation in the opposite direction is referred to as reverse rotation. The cooling fan unit  12  is an example of a blower device. 
         [0030]    The space in the container  10  is separated into an outside air introduction section  21 , a cold aisle  22 , a first hot aisle  23 , a second hot aisle  24 , a moisture absorption section  25 , and a warm air circuit  26 . 
         [0031]    The outside air introduction section  21  is a space between the wall surface of the container  10 , on which the shutter  11  is provided, and the cooling fan unit  12 . Meanwhile, the cold aisle  22  is a space between the cooling fan unit  12  and the racks  13 . Further, the first hot aisle  23  is a space located on an opposite side of the racks  13  from the cold aisle  22 . 
         [0032]    The second hot aisle  24  and the moisture absorption section  25  belongs to a space between the first hot aisle  23  and the wall surface of the container  10  on which the shutter  16  is provided. A lower part of the space is the moisture absorption section  25  while an upper part thereof is the second hot aisle  24 . 
         [0033]    A shutter  17  is provided between the first hot aisle  23  and the second hot aisle  24 . Meanwhile, a shutter  18   a  is provided between the first hot aisle  23  and the moisture absorption section  25 , and a shutter  18   b  is provided between the moisture absorption section  25  and the second hot aisle  24 . The shutters  17 ,  18   a,  and  18   b  are also opened and closed by signals outputted from the controller  30 . 
         [0034]    A moisture absorbent  25   a  is disposed in the moisture absorption section  25 . For example, zeolite, activated carbon, silica gel, or a polymer moisture absorbent which may be renewed (dried) relatively at a low temperature is used as the moisture absorbent  25   a.  The moisture absorbent  25   a  preferably applies one which is designed to exert a favorable moisture absorption performance at a temperature below 40° C., and to discharge the absorbed moisture for renewal when the temperature is equal to or above 40° C. and a humidity is equal to or below 30% RH, for example. 
         [0035]    The warm air circuit  26  is a space provided above the cooling fan unit  12 , the cold aisle  22 , the racks  13 , and the first hot aisle  23 . The warm air circuit  26  connects the second hot aisle  24  and the outside air introduction section  21 . A shutter  19  is provided to the warm air circuit  26 . The shutter  19  is also opened and closed by signals outputted from the controller  30 . 
         [0036]    A humidity sensor  27   a  configured to detect a humidity of air in the cold aisle  22  is provided to the cold aisle  22 . Meanwhile, a temperature sensor  28  configured to detect a temperature of air in the first hot aisle  23  and a humidity sensor  27   b  configured to detect a humidity thereof are provided to the first hot aisle  23 . Outputs from the humidity sensors  27   a  and  27   b  and from the temperature sensor  28  are transmitted to the controller  30 . 
         [0037]    Furthermore, a dew-point temperature sensor  29  configured to detect a dew-point temperature of outside air is installed outside the container  10 . An output from the dew-point temperature sensor  29  is also transmitted to the controller  30 . The dew-point temperature sensor  29  is an example of a dew-point temperature detector. Here, a set of a temperature sensor and a humidity sensor, the temperature sensor configured to detect a temperature of the outside air and the humidity sensor configured to detect a relative humidity, a device which may measure an absolute humidity, or the like may be installed instead of the dew-point temperature sensor  29 , and the dew-point temperature may be detected by using outputs therefrom. 
         [0038]    Here, the outside air introduction section  21  and the cold aisle  22  are collectively an example of a first space while the first hot aisle  23  is an example of a second space. Moreover, the second hot aisle  24  is an example of a third space while the moisture absorption section  25  is an example of a fourth space. Furthermore, the warm air circuit  26  is an example of a fifth space. 
         [0039]    In the meantime, the shutter  11  is an example of a first shutter, the shutter  16  is an example of a second shutter, and the shutter  17  is an example of a third shutter. 
         [0040]    Moreover, the shutter  18   a  is an example of a fourth shutter, the shutter  18   b  is an example of a fifth shutter, and the shutter  19  is an example of a sixth shutter  19 . 
         [0041]    Now, air flow control in the data center of the embodiment will be described below with reference to flowcharts illustrated in  FIGS. 3A and 3B . Here, the servers  13   a  are assumed to be stopped in an initial state. 
         [0042]    First, in step S 11 , the controller  30  acquires data on the temperature inside each rack  13  from the temperature sensor  13   b  and acquires data on the dew-point temperature of the outside air from the dew-point temperature sensor  29 . 
         [0043]    Next, in step S 12 , the controller  30  compares the temperature inside the rack  13  acquired from the temperature sensor  13   b  with the dew-point temperature of the outside air acquired from the dew-point temperature sensor  29 . Then, step S 13  takes place when the temperature inside the rack  13  is equal to or below the dew-point temperature of the outside air (in the case of NO) or step S 17  takes place when the temperature inside the rack  13  is above the dew-point temperature of the outside air (in the case of YES). An operation stand-by mode is established when step S 13  takes place, and a normal operation mode is established when step S 17  takes place. 
         [0044]    When the control moves from step S 12  to step S 13 , i.e., when the temperature inside the rack  13  is equal to or below the dew-point temperature of the outside air, dew condensation may occur inside the servers  13   a  if the outside air is introduced into the rack  13 , and may lead to a breakdown or a failure. In this case, the controller  30  opens the shutters  11 ,  16 ,  18   a,    18   b,  and  19  and closes the shutter  17 . Thereafter, the control moves to step S 14  where the controller  30  conducts reverse rotation of the cooling fans  12   a  of the cooling fan unit  12 . 
         [0045]      FIG. 4  is a view illustrating airflow in this case. Outline arrows in  FIG. 4  indicate flowing directions of the air. 
         [0046]    By putting the cooling fans  12   a  of the cooling fan unit  12  into the reverse rotation, a pressure in the cold aisle  22  is reduced while a pressure in the outside air introduction section  21  is increased. Thus, part of the air in the outside air introduction section  21  is discharged to the outside through the shutter  11  while the rest of the air moves to the second hot aisle  24  through the warm air circuit  26 . 
         [0047]    In the meantime, the air in the amount equivalent to that discharged to the outside through the shutter  11  flows from the outside into the second hot aisle  24  through the shutter  16 . Then, the air in the second hot aisle  24  moves to the first hot aisle  23  through the moisture absorption section  25 , and then moves to the cold aisle  22  through the rack  13 . 
         [0048]    The air passing through the moisture absorption section  25  is deprived of moisture by the moisture absorbent  25   a  and thus becomes dry. In addition, heat is generated when the moisture absorbent  25   a  absorbs the moisture. As a consequence, the temperature of the air after passing through the moisture absorption section  25  becomes higher than the temperature of the air before passing through the moisture absorption section  25 . The air thus deprived of the moisture and having the higher temperature is introduced into the rack  13 , and dew condensation inside the servers  13   a  is avoided as a consequence. 
         [0049]    Although part of the outside air is taken into the container  10  by opening the shutters  11  and  16  in this embodiment, the shutters  11  and  16  may be closed instead.  FIG. 5  is a schematic view illustrating airflow inside the container  10  in this case. In this case as well, the temperature of the air in the container  10  is increased by the heat generated by the moisture absorbent  25   a  or the heat generated in association with the operation of the cooling fan unit  12 . 
         [0050]    The cooling fan unit  12  is operated in step S 14 , and then step S 15  takes place. In step S 15 , the controller  30  acquires data on the humidity of the air in the first hot aisle  23  from the humidity sensor  27   b,  and determines whether or not the humidity of the air in the first hot aisle  23  is equal to or below a first predetermined humidity (such as 80% RH). The control returns to step S 11  when the humidity of the air in the first hot aisle  23  is determined to be above the first predetermined humidity (in the case of NO). 
         [0051]    On the other hand, when the humidity of the air in the first hot aisle  23  is determined to be equal to or below the first predetermined humidity (in the case of YES) in step S 15 , there is no risk of occurrence of dew condensation inside the servers  13   a.  Accordingly, the control moves to step S 16  and the servers  13   a  are operated. 
         [0052]    When the servers  13   a  are operated in step S 16 , a large amount of heat is generated in association with the operation of the servers  13   a.  As a consequence, the temperature of the air in the container  10  is rapidly increased. After the servers  13   a  are operated in step S 16 , the control returns to step S 11 . 
         [0053]    The procedure from step S 11  to step S 16  will be repeated until the temperature inside the rack  13  is determined to be above the dew-point temperature of the outside air in step S 12 . 
         [0054]    When the temperature inside the rack  13  is determined to be above the dew-point temperature of the outside air (in the case of YES) in step S 12 , the control moves to step S 17  (a normal operation mode). When step S 17  takes place, the controller  30  opens the shutters  11 ,  16 , and  17  and closes the shutter  19 . In addition, the controller  30  closes the shutters  18   a  and  18   b,  thereby establishing a hermetically closed state of the moisture absorption section  25 . 
         [0055]    Thereafter, the control moves to the step S 18  where the controller  30  conducts forward rotation of the cooling fans  12   a  of the cooling fan unit  12  and operates the servers  13   a  in the rack  13 . Nonetheless, if the servers  13   a  are already in operation, then the controller  30  maintains the operating state. 
         [0056]      FIG. 6  is a view illustrating airflow in this case. As illustrated in  FIG. 6 , the outside air (the air) is introduced into the outside air introduction section  21  through the shutter  11 , and the air in the outside air introduction section  21  moves to the cold aisle  22  by using the cooling fan unit  12 . Then, the air moves to the first hot aisle  23  through the rack  13 , and moves further to the second hot aisle  24  through the shutter  17 . Eventually, the air is discharged to the outside through the shutter  16 . 
         [0057]    When the control moves from step S 12  to step S 17 , the temperature inside the rack  13  is higher than the dew-point temperature of the outside air. Accordingly, there is no risk of occurrence of dew condensation inside the servers  13   a  even when the outside air is introduced into the rack  13 . 
         [0058]    Here, when the outside air temperature is low, the shutter  19  may be opened so as to return part of the air in the second hot aisle  24  to the outside air introduction section  21 .  FIG. 7  is a view illustrating air flow when the shutter  19  is opened. 
         [0059]    Next, the control moves to step S 19  where the controller  30  acquires the temperature and the humidity of the air in the first hot aisle  23  from the temperature sensor  28  and the humidity sensor  27   b.  Then, the control moves to step S 20  where the controller  30  determines whether or not the temperature of the air in the first hot aisle  23  is equal to or above a predetermined temperature (such as 40° C.). The control returns to step S 11  when the temperature of the air in the first hot aisle  23  is determined to be below the predetermined temperature (in the case of NO). 
         [0060]    On the other hand, the control moves to step S 21  when the temperature of the air in the first hot aisle  23  is determined to be equal to or above the predetermined temperature (in the case of YES) in step S 20 . 
         [0061]    In step S 21 , the controller  30  determines whether or not the humidity of the air in the first hot aisle  23  is equal to or below a second predetermined humidity (such as 30% RH). Then, the control returns to step S 11  when the humidity of the air in the first hot aisle  23  is determined to be above the second predetermined humidity (in the case of NO). 
         [0062]    On the other hand, the control moves to step S 22  when the humidity of the air in the first hot aisle  23  is determined to be equal to or below the second predetermined humidity (in the case of YES) in step S 21 . In step S 22 , the controller  30  closes the shutter  17  and opens the shutters  18   a  and  18   b.  Thereafter, the control returns to step S 11  to continue the processing. 
         [0063]      FIG. 8  is a view illustrating airflow when the shutter  17  is closed and the shutters  18   a  and  18   b  are opened in step S 22 . In this state, the air having the temperature equal to or above the predetermined temperature and the humidity equal to or below the second predetermined humidity passes through the moisture absorption section  25 . As a consequence, the moisture evaporates from the moisture absorbent  25   a  and the moisture absorbent  25   a  is thus renewed (dried). 
         [0064]    As described above, in this embodiment, the operation stand-by mode is established when the temperature inside the rack  13  is equal to or below the dew-point temperature of the outside air, and the air deprived of the moisture as a consequence of the passage through the moisture absorption section  25  is fed into the rack  13 . In this way, it is possible to increase the temperature inside the rack  13  while avoiding occurrence of dew condensation inside the rack  13 . 
         [0065]    Moreover, in this embodiment, the normal operation mode is established when the temperature inside the rack  13  is above the dew-point temperature of the outside air. In the normal operation mode, the cooling fans  12   a  of the cooling fan unit  12  are rotated in the forward direction, and the servers  13   a  in the rack  13  are cooled by the outside air taken into the container  10  through the shutter  11 . Thus, it is possible to cool the servers  13   a  with less power and thus to reduce power consumption of the data center. 
         [0066]    Furthermore, in this embodiment, when the temperature of the air discharged from the rack  13  is above the predetermined temperature and the humidity thereof is below the second predetermined humidity, the air discharged from the rack  13  is fed into the moisture absorption section  25 . Thus, the moisture absorbed in the moisture absorbent  25   a  evaporates and the moisture absorbent  25   a  is renewed (dried). Accordingly, the moisture absorbent  25   a  may be reused many times so as to reduce its running cost. 
         [0067]    A description will be hereinbelow provided for experiments to examine the occurrence of dew condensation by actually operating the modular data center of to this embodiment. 
       Experiment 1 
       [0068]    The modular data center having the structure illustrated in  FIG. 1  is put to use while disposing 10 kg of zeolite as the moisture absorbent  25   a  in the moisture absorption section  25 . 
         [0069]    When the outside air temperature is  5 ° C., the outside air humidity is 100% RH, and the dew-point temperature of the outside air is 5° C., the temperature inside the rack  13  with the servers  13   a  in the stopped state is 3° C. 
         [0070]    Since the temperature inside the rack  13  is below the dew-point temperature of the outside air, the air is fed into the container  10  as illustrated in  FIG. 4  by conducting the reverse rotation of the cooling fans  12   a  of the cooling fan unit  12 . The humidity of the air passing through the moisture absorption section  25  is reduced to about 70% RH, and the humidity (the humidity at 3° C.) inside the rack  13  becomes equal to about 80% RH. 
         [0071]    Since the humidity inside the rack  13  is equal to or below a predetermined value (80% RH), the servers  13   a  are put into operation. When the servers  13   a  start the operation, the temperature inside the rack  13  is increased to  10 ° C. due to the heat generated by the servers  13   a.    
         [0072]    Since the temperature inside the rack  13  exceeds the dew-point temperature of the outside air, the rotation of the cooling fans  12   a  of the cooling fan unit  12  is changed to the forward rotation. In the meantime, the shutter  17  is opened and the shutters  18   a  and  18   b  are closed. Thus, the airflow inside the container  10  turns into the one illustrated in  FIG. 6 . As a consequence, the servers  13   a  are successfully operated while avoiding dew condensation inside the servers  13   a.    
       Experiment 2 
       [0073]    The modular data center having the structure illustrated in  FIG. 1  is put to use while disposing 10 kg of ecoPoD (registered trademark) polymer sorbent manufactured by Okayama Eco Energy Gijutsu Kenkyusho KK. as the moisture absorbent  25   a  into moisture absorption section  25 . 
         [0074]    When the outside air temperature is 5° C., the outside air humidity is 100% RH, and the dew-point temperature of the outside air is 5° C., the temperature inside the rack  13  with the servers  13   a  in the stopped state is 3° C. 
         [0075]    Since the temperature inside the rack  13  is below the dew-point temperature of the outside air, the air is fed into the container  10  as illustrated in  FIG. 4  by conducting the reverse rotation of the cooling fans  12   a  of the cooling fan unit  12 . The humidity of the air passing through the moisture absorption section  25  is reduced to about 70% RH, and the humidity (the humidity at 3° C.) inside the rack  13  becomes equal to about 80% RH. 
         [0076]    Since the humidity inside the rack  13  is equal to or below the predetermined value (80% RH), the servers  13   a  are put into operation. When the servers  13   a  start the operation, the temperature inside the rack  13  is increased to 10° C. due to the heat generated by the servers  13   a.    
         [0077]    Since the temperature inside the rack  13  exceeds the dew-point temperature of the outside air, the rotation of the cooling fans  12   a  of the cooling fan unit  12  is changed to the forward rotation. In the meantime, the shutter  17  is opened and the shutters  18   a  and  18   b  are closed. Thus, the airflow inside the container  10  turns into the one illustrated in  FIG. 6 . As a consequence, the servers  13   a  are successfully operated while avoiding dew condensation inside the servers  13   a.    
         [0078]    Thereafter, the temperature of the air in the first hot aisle  23  reaches 45° C. and the humidity thereof reaches 25% RH. Hence the shutter  17  is closed and the shutters  18   a  and  18   b  are opened. Thus, the air is fed into the moisture absorption section  25  and the moisture absorbent  25   a  is renewed (dried). 
         [0079]    All examples and conditional language recited herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.