Abstract:
A power usage management system includes, in order to efficiently distribute electric power, a power feeding gate device supplied with electric power from a power line and controlling supply of electric power based on a key code, a server system transmitting a key code corresponding to identification information for identifying the power feeding gate device, and a mobile receptacle attachable/detachable to/from the power feeding gate device, receiving identification information from the power feeding gate device, receiving the key code corresponding to the identification information from the server system, and providing the key code to the power feeding gate device.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a mobile receptacle, an electric-power feeding gate device, a server device and an electric-power usage management system. In particular, the invention relates to a mobile receptacle, an electric-power feeding gate device, a server device and an electric-power usage management system for supplying electric power to household electrical appliances.  
           [0003]    2. Description of the Background Art  
           [0004]    Japanese Utility Model Registration No. 3,061,831 discloses a coin-operated locker for vending electric power. This locker is used for electrically charging, anywhere away from home, such mobile equipment as a personal computer, an electronic notepad, a portable stereo player with a headphone and a cellular telephone, without the risk of theft of the equipment.  
           [0005]    Japanese Patent Laying-Open No. 2000-123246 discloses an electric power vending machine for electrically charging a cellular phone conveniently at any place away from home, without the need for an AC feeder line.  
           [0006]    In addition, a portable power generator has been known that uses a portable gasoline engine for example.  
           [0007]    In consideration of the issue of security, the location where the power vending locker is installed is limited to well-trafficked places where a locker-keeper attends, resulting in the need for the labor cost of the keeper. Moreover, if a certain shop or store owns and manages the locker, the locker is unavailable after the shop or store is closed.  
           [0008]    The power vending locker dispenses electric power only when the locker is closed. This means that the locker can be used for only those products that are chargeable and small enough to be held within the locker. Thus, the locker cannot be used for charging electric vehicles that are now becoming pervasive or motor-assisted bicycles. Further, since the power can be delivered only when the locker is closed, it is impossible to electrically charge such electric appliances as portable television and refrigerator that are used at a campsite for example.  
           [0009]    There is a problem with the locker for vending electric power and the power vending machine for charging a cellular phone. Specifically, this problem is that the locker and machine can only be used when the user has ready cash at hand.  
           [0010]    Further, the locations where the power vending locker and power vending machine for charging a cellular phone are installed are often found away or remote from electric mains (power lines on power poles). Therefore, a long line is necessary for drawing electric power to such installations, or large electric power cannot be supplied to the installations when there are some branches at midpoints of the mains.  
           [0011]    With regard to the portable generator using the gasoline engine for example, if the generator is used for a long-term camping for example, the campsite is limited to any place where refueling is available at a gas station or the like. Further, the heavy generator and fuel are inappropriate for portable use. In addition, the flammable gasoline used as a fuel is inappropriate for portable use and storage.  
           [0012]    A further problem with the portable generator using gasoline engine for example is that the generator produces noise and exhaust gas.  
           [0013]    Although electric vehicles are expected to become widespread in the future, there are currently few places where electric vehicles can readily be charged when the electric vehicles run out of fuel on the way. Full-charging of currently-developed electric vehicles generally takes the whole night, however, the fully-charged electric vehicles can travel approximately 200 km at most, which is extremely shorter than that of gasoline-powered and diesel-powered automobiles. If the battery of the electric vehicle is increased in size for the purpose of achieving a longer travelling distance, the greater battery results in a longer charging time and increase in the weight and size of the body. Consequently, many problems arise such as deterioration of the energy efficiency and increase in cost.  
           [0014]    Regarding the conventional power distribution grid (system), the state of electric power usage can be examined for only the total amount of used power measured at a power feeding source (electric power plant) and thus it is impossible to examine the state of power usage on the basis of area or time. Then, it is difficult to distribute power according to the amount of used power, causing an unbalance between supply and demand which hinders enhancement of the power usage efficiency.  
         SUMMARY OF THE INVENTION  
         [0015]    The present invention is made to solve the above-described problems. One object of the invention is to provide a mobile receptacle, a power feeding gate device, a server device and a power usage management system by which electric power can efficiently be delivered.  
           [0016]    Another object of the present invention is to provide a mobile receptacle, a power feeding gate device, a server device and a power usage management system by which a fee or rate for the amount of used electric power can automatically be charged.  
           [0017]    Still another object of the present invention is to provide a mobile receptacle, a power feeding gate device, a server device and a power usage management system by which an amount of used electric power can be monitored on the basis of the place or period of power usage for efficiently delivering electric power.  
           [0018]    According to one aspect of the present invention, a mobile receptacle is attachable/detachable to/from a power feeding gate device which is supplied with electric power from a power line and which has a switch turned on/off to control power-on and power-off based on a key code. The mobile receptacle communicates information with a server device. The mobile receptacle includes an identification information acquiring unit to acquire, from the power feeding gate device to which the mobile receptacle is attached, identification information about the power feeding gate device, an identification information transmitting unit connected to the identification information acquiring unit to transmit to the server device the acquired identification information about the power feeding gate device, a key code receiving unit to receive from the server device a key code corresponding to the identification information about the power feeding gate device for turning on the switch, and a key code output unit connected to the key code receiving unit to output the received key code to the power feeding gate device.  
           [0019]    The identification information about the power feeding gate device is obtained from the power feeding gate device to which the mobile receptacle is attached. In return for the identification information, the key code is provided from the server device. This key code is transmitted to the power feeding gate device and accordingly power becomes available. Thus, the user at any place away from home can easily use the electric power by attaching the mobile receptacle to the power feeding gate device.  
           [0020]    According to another aspect of the present invention, a power feeding gate device supplies electric power from a power line to an attachable/detachable mobile receptacle. The power feeding gate device includes a switch turned on/off according to whether electric power is supplied to the mobile receptacle or not, a key code acquiring unit to acquire, from the mobile receptacle to which the power feeding gate device is attached, a key code for turning on the switch, and a control unit connected to the switch and the key code acquiring unit to control turning on/off of the switch based on the acquired key code.  
           [0021]    Whether or not electric power is fed to the mobile receptacle is determined based on the key code acquired from the mobile receptacle.  
           [0022]    According to still another aspect of the present invention, a server device communicates information with a mobile receptacle attached to a power feeding gate device which is supplied with electric power from a power line and which has a switch. The server device includes a first storage unit to store a key code per identification information about the power feeding gate device, the key code being used for turning on the switch, a receiving unit to receive from the mobile receptacle the identification information for identifying the power feeding gate device, an extracting unit to extract the key code stored in the first storage unit based on the identification information about the power feeding gate device received by the receiving unit, and a transmitting unit to transmit the key code extracted by the extracting unit to the mobile receptacle.  
           [0023]    The server device receives the identification information about the power feeding gate device from the mobile receptacle, and then transmits the key code corresponding to that identification information to the mobile receptacle. Accordingly, usage of power by mobile receptacle becomes possible.  
           [0024]    According to a further aspect of the present invention, a power usage management system includes a power feeding gate device supplied with electric power from a power line and controlling supply of electric power based on a key code, a server device transmitting the key code corresponding to identification information for identifying the power feeding gate device, and a mobile receptacle attachable/detachable to/from the power feeding gate device, receiving the identification information from the power feeding gate device, receiving the key code corresponding to the identification information from the server device, and providing the key code to the power feeding gate device.  
           [0025]    The mobile receptacle receives from the server device the key code corresponding to the identification information about the power feeding gate device to which the mobile receptacle is attached. Then, the mobile receptacle provides the key code to the power feeding gate device. Based on the key code, power feeding gate device determines whether it supplies power or not. In this way, the user can obtain and use electric power in a simplified manner.  
           [0026]    The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    [0027]FIG. 1 externally shows a power usage management system.  
         [0028]    [0028]FIG. 2 is a block diagram showing a hardware configuration of the power usage management system.  
         [0029]    [0029]FIG. 3 is a block diagram showing a hardware configuration of a mobile receptacle.  
         [0030]    [0030]FIG. 4 is a block diagram showing a hardware configuration of a power feeding gate device.  
         [0031]    [0031]FIG. 5 is a block diagram showing a hardware configuration of a server system.  
         [0032]    [0032]FIG. 6 shows information regarding the power feeding gate device that is stored in a storage unit.  
         [0033]    [0033]FIG. 7 shows information regarding the mobile receptacle that is stored in a storage unit.  
         [0034]    FIGS.  8 - 12  show a flowchart illustrating an operation of the power usage management system.  
         [0035]    [0035]FIG. 13 is a block diagram showing a hardware configuration of the power usage management system. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]    One embodiment of the present invention is applied herein for example to charging of an electric vehicle and accordingly described below.  
         [0037]    &lt;Entire Structure of the System&gt; 
         [0038]    Referring to FIGS. 1 and 2, a power usage management system includes a power plant (power feeding source)  44 , a power line  47  for conveying electric power generated by power feeding source  44 , a power feeding gate device  41  connected to power line  47  for controlling the amount of power, a mobile receptacle  42  which is portable and connected to power feeding gate device  41  through power line  47  and a communication line  48  when electric power is used, and a server system  45  of an electric power company that is connected to mobile receptacle  42  through a communication line  49  which is of radio communication, for example, for managing the state of usage of the electric power as well as monetary charging information. To mobile receptacle  42 , electric-power-driven equipment or machine such as an electric vehicle  43  for example is connected, and accordingly electric power is fed to electric vehicle  43 .  
         [0039]    Electric power company  46  includes power feeding source  44  and server system  45 .  
         [0040]    Communication line  48  is used for transmitting signals between power feeding gate device  41  and mobile receptacle  42  for using electric power.  
         [0041]    Communication line  49  is used for transmitting information about usage of power, for example, between mobile receptacle  42  and server system  45 . Communication line  49  may be such a wire as telephone line, power line or optical fiber by which two-way communication is possible.  
         [0042]    &lt;Mobile Receptacle&gt; 
         [0043]    Referring to FIG. 3, mobile receptacle  42  includes an antenna  2 , a radio communication unit  3  connected to antenna  2  for radio communication between antenna  2  and electric power company  46 , a storage unit  4  for storing various types of information, an interface circuit  11  connected to power feeding gate device  41  through power line  47  and communication line  48  for transmitting and receiving power and signals between mobile receptacle  42  and power feeding gate device  41 , a power usage integrating meter  13  connected to interface circuit  11  for measuring the amount of electric power used by electric vehicle  43 , and a receptacle  15  connected to integrating meter  13  for supplying electric power to electric vehicle  43 .  
         [0044]    Mobile receptacle  42  further includes a battery  14  storing electric power used for driving components of mobile receptacle  42 , a sensor  10  detecting connection of mobile receptacle  42  to power feeding gate device  41 , a display unit  6  showing information regarding whether or not mobile receptacle  42  can be used, a period of time for which the mobile receptacle is used, and the amount of used power, for example, and a control unit  9  connected to radio communication unit  3 , storage unit  4 , display unit  6 , sensor  10 , interface circuit  11  and integrating meter  13  for generally controlling each of the components.  
         [0045]    Storage unit  4  stores an ID code of mobile receptacle  42 , an ID request signal of power feeding gate device  41  that is necessary for using power feeding gate device  41 , a key code request signal of power feeding gate device  41  that is necessary for using power feeding gate device  41 , a specified value (upper limit) of the number of times a retry request is made to electric power company  46  for a key code of power feeding gate device  41  when a key code of power feeding gate device  41  does not match a code transmitted from mobile receptacle  42 , a gate device unavailability signal transmitted to electric power company  46  when power feeding gate device  41  cannot be used, and a usage finish notification signal for informing electric power company  46  of the end of power usage.  
         [0046]    Storage unit  4  temporarily stores an ID code of power feeding gate device  41 , a key code request signal of power feeding gate device  41  that is transmitted from power feeding gate device  41  when a key code of power feeding gate device  41  does not match a code transmitted from mobile receptacle  42  and a retry request is made to electric power company  46  for a key code of power feeding gate device  41 , and a retry number which is the number of times a retry request is made to electric power company  46  for a key code of power feeding gate device  41  when a key code of power feeding gate device  41  does not match a code transmitted from mobile receptacle  42 .  
         [0047]    Mobile receptacle  42  may conduct wire communication with electric power company  46 . In this case, a wire communication unit is employed instead of radio communication unit  3 .  
         [0048]    &lt;Power Feeding Gate Device&gt; 
         [0049]    Referring to FIG. 4, power feeding gate device  41  includes a switch  22  connected to power line  47  for limiting transmission of power, which is fed from electric power company  46 , to mobile receptacle  42 , an interface circuit  23  for transmitting control signals and electric power between power feeding gate device  41  and mobile receptacle  42 , and a sensor (connection detecting sensor)  27  for detecting connection of mobile receptacle  42  to power feeding gate device  41 .  
         [0050]    Power feeding gate device  41  further includes a storage unit  25  for storing ID code specific to power feeding gate device  41 , a key code for turning switch  22  on for using power, a key code request signal for requesting a key code to turn on switch  22  for using power, and a usage start notification signal indicating that switch  22  is turned on, and includes a control unit  24  connected to switch  22 , interface circuit  23 , storage unit  25  and connection detecting sensor  27  for generally controlling each of the components.  
         [0051]    &lt;Server System  45  of Electric Power Company  46 &gt; 
         [0052]    Referring to FIG. 5, server system  45  of electric power company  46  includes a storage unit  34  storing information concerning the power feeding gate device, a storage unit  35  storing information concerning the mobile receptacle, an antenna  36 , a radio communication unit  32  connected to antenna  36  for communication between server system  45  of electric power company  46  and mobile receptacle  42 , a clock  37  for managing a period of time during which power feeding gate device  41  is used, and a control unit  31  connected to radio communication unit  32  and storage units  34  and  35  for generally controlling each of the components.  
         [0053]    Wired communication may be conducted between server system  45  and the mobile receptacle. In this case, a wire communication unit is used instead of radio communication unit  32 .  
         [0054]    Referring to FIG. 6, storage unit  34  stores ID code information specific to power feeding gate device  41 , key code information associated with each power feeding gate device  41  for controlling switch  22  of power feeding gate device  41 , installation site indicating where power feeding gate device  41  is installed, ID information of mobile receptacle  42  that uses power feeding gate device  41 , usage start time indicating when a user starts using power feeding device  41 , usage finish time indicating when the user finishes using power feeding gate device  41 , a power usage amount indicating how much the user uses power supplied from power feeding gate device  41 , fault information indicating record of fault of power feeding gate device  41 , and usage time information indicating the number of times mobile receptacle  42  uses power feeding gate device  41 .  
         [0055]    The ID code information, key code information and installation site are registered in advance by an electric power management company when electric power company  46  installs power feeding gate device  41 .  
         [0056]    Referring to FIG. 7, storage unit  35  stores ID code information specific to mobile receptacle  42 , user information associated with mobile receptacle  42  (information about the address, name, contact address for example of a user), a value indicated by power usage integrating meter  13  of mobile receptacle  42  when the user starts using power feeding gate device  41 , usage start time of power feeding gate device  41 , a value of power usage integrating meter  13  of mobile receptacle when the user finishes using power feeding gate device  41 , usage finish time of power feeding gate device  41 , an ID code of power feeding gate device  41  utilized by the user, an amount of power used by the user, a fee for the amount of used power, and information about an account of the user in order for electric power company  46  to collect the usage fee from the user.  
         [0057]    In the power management company, the ID code information, user information and the information about the account of the user are registered in advance when the user arranges for usage of the system.  
         [0058]    A person in charge in electric power company  46  is informed of occurrence of fault from the fault information of power feeding gate device  41  to locate the site of installation of failed power feeding gate device  41  according to the installation site information of power feeding gate device  41 . After this, the person in charge in electric power company  46  or a member of a maintenance company repairs the failed power feeding gate device  41 .  
         [0059]    Referring to FIGS.  8 - 12 , an operation of the power usage management system is now described.  
         [0060]    Referring to FIG. 8, a user attaches mobile receptacle  42  to interface circuit  23  of power feeding gate device  41  for electrically charging electric vehicle  43  (S 2 ).  
         [0061]    Sensor  10  of mobile receptacle  42  detects whether or not mobile receptacle  42  is connected to power feeding gate device  41 . A resultant detection signal is input to control unit  9 . Control unit  9  detects the detection signal to read an ID code request signal of power feeding gate device  41  that is stored in storage unit  4 , and transmits the ID code request signal to power feeding gate device  41  through interface circuit  11  (S 4 ).  
         [0062]    Power feeding gate device  41  receives the ID request signal of power feeding gate device  41  from mobile receptacle  42  through communication line  48  and interface circuit  23  (S 6 ). This ID request signal is input to control unit  24 . Control unit  24  reads ID code of power feeding gate device  41  that is stored in storage unit  25 , and transmits the ID code to mobile receptacle  42  through interface circuit  23  with respect to mobile receptacle  42  and through communication line  48  for communication with mobile receptacle  42  (S 8 ).  
         [0063]    A signal including the ID code of power feeding gate device  41  is provided from power feeding gate device  41  to interface circuit  11  of mobile receptacle  42  (S 10 ), and that signal is transmitted to control unit  9 . In response to the signal, control unit  9  reads ID code of mobile receptacle  42  and the key code request signal of power feeding gate device  41  for turning switch  22  on that are stored in storage unit  4 . Control unit  9  transmits, to radio communication unit  3 , the ID code of power feeding gate device  41 , the ID code of mobile receptacle  42 , and the key code request signal of power feeding gate device  41  for turning switch  22  on. Radio communication unit  3  converts the signal from control unit  9  into radio wave which is accordingly radiated from antenna  2 . The signal from antenna  2  is transmitted to the electric power company (S 12 ).  
         [0064]    Communication unit  32  in server system  45  of electric power company  46  receives from mobile receptacle  42  the ID code of power feeding gate device  41 , the ID code of mobile receptacle  42 , and the key code request signal for turning on switch  22  of power feeding gate device  41  (S 14 ), and transmits the signal to control unit  31 . Control unit  31  reads, from storage unit  34  storing information about power feeding gate device  41 , a key code for turning on switch  22  of power feeding gate device  41  corresponding to the ID code of power feeding gate device  41 , and transmits the key code to communication unit  32  (S 16 ). Communication unit  32  then transmits the key code back to mobile receptacle  42 . (S 18 ).  
         [0065]    Radio communication unit  3  of mobile receptacle  42  receives a signal including the key code of power feeding gate device  41  from electric power company  46 , and converts the signal into an electric signal which is transmitted to control unit  9  (S 20 ). Control unit  9  receives and then transmits the key code signal of power feeding gate device  41  to power feeding gate device  41  through interface circuit  11  (S 22 ).  
         [0066]    Interface circuit  23  of power feeding gate device  41  receives, from mobile receptacle  42  through communication line  48  and interface circuit  23 , the key code for turning on switch  22  of power feeding gate device  41  and inputs the signal to control unit  24  (S 24 ). Control unit  24  reads a key code of power feeding gate device  41  stored in storage unit  25  and compares the read key code with the key code provided from mobile receptacle  42  (S 26 ). If these key codes do not match (NO in S 26 ), a retry process is carried out as shown in FIG. 10 and the subsequent drawing and described later. If the key codes match (YES in S 26 ), control unit  24  transmits the signal to switch  22  for turning on switch  22 . In response to this signal, switch  22  is turned on (S 28 ). Control unit  24  transmits a signal indicating that switch  22  is made on (usage start notification signal) to mobile receptacle  42  through interface circuit  23  and communication line  48 . At this time, power is output to interface circuit  23  with respect to mobile receptacle  42  (S 30 ).  
         [0067]    Referring to FIG. 9, interface circuit  11  of mobile receptacle  42  receives the usage start notification signal from power feeding gate device  41 , and the signal is transmitted to control unit  9  (S 32 ). Control unit  9  receives the usage start notification signal to read the ID code of mobile receptacle  42  that is stored in storage unit  4  and a value indicated by power usage integrating meter  13 . Control unit  9  provides the usage start notification signal, ID code of mobile receptacle  42  and the value indicated by power usage integrating meter  13  to radio communication unit  3 . Radio communication unit  3  converts the signal received from control unit  9  into radio wave which is accordingly radiated from antenna  2 . The signal radiated from antenna  2  is transmitted to electric power company  46  (S 34 ).  
         [0068]    Further, control unit  9  receives the usage start notification signal to show on display unit  6  that electric power is now available (S 36 ). Control unit  9  further resets, to zero, the number of times a retry is made that is stored in storage unit  4  (S 38 ). Power usage integrating meter  13  calculates the integral of the amount of used power (S 40 ). Then, an external equipment (e.g. charging plug of electric vehicle  43 ) is connected to receptacle  15  (S 42 ), and accordingly power becomes available when the external equipment is powered on (S 44 ).  
         [0069]    After the step S 34 , communication unit  32  in server system  45  of electric power company  46  receives the ID code of mobile receptacle  42 , the value indicated by the power usage integrating meter included in mobile receptacle  42  and the usage start notification signal that are provided from mobile receptacle  42 , and then transmits them to control unit  31  (S 46 ). Control unit  31  stores, in a relevant area of storage unit  35  storing information about mobile receptacle  42 , the value indicated by power usage integrating meter  13  included in mobile receptacle  42 . Control unit  31  reads the time indicated by clock  37  and stores the time as usage start time of power feeding gate device  41  in storage unit  35 .  
         [0070]    Control unit  31  records in a relevant area of storage unit  35  storing information about mobile receptacle  42 , ID code of power feeding gate device  41  to be used (S 48 ). Control unit  31  records the ID code of mobile receptacle  42  and the usage start time in a relevant area for power feeding gate device  41  in storage unit  34  storing information about power feeding gate device  41  (S 50 ).  
         [0071]    Referring back to FIG. 8, if the key code of power feeding gate device  41  that is stored in storage unit  25  do not match the key code transmitted from mobile receptacle  42  (NO in S 26 ), a retry process is carried out.  
         [0072]    Referring to FIG. 10, the retry process is described.  
         [0073]    Control unit  24  of power feeding gate device  41  reads the key code request signal and ID code of power feeding gate device  41  that are stored in storage unit  25  and transmits them to mobile receptacle  42  through interface circuit  23  and communication line  48  (S 52 ).  
         [0074]    Interface circuit  11  of mobile receptacle  42  receives the key code request signal and ID code of power feeding gate device  41  and transmits this information to control unit  9  (S 54 ). Control unit  9  temporarily stores the information in storage unit  4 . Control unit  9  determines whether the number of times the retry request is made (retry number) exceeds a specified number stored in storage unit  4  (S 56 ). Control unit  9  adds  1  to the retry number stored in storage unit  4  for updating the retry number which is accordingly stored in storage unit  4 . Control unit  9  thereafter compares the updated retry number with the upper limit of the retry number which is also stored in storage unit  4 .  
         [0075]    If the retry number is equal to or greater than the upper limit of the retry number (YES in S 56 ), which means that power is unavailable. Then, the subsequent process is carried out that is shown in FIG. 11 and described later.  
         [0076]    If the retry number is smaller than the upper limit (NO in S 56 ), control unit  9  transmits, to radio communication unit  3 , the key code request signal of power feeding gate device  41  and respective ID codes of mobile receptacle  42  and power feeding gate device  41  that have already been stored in storage unit  4 . Radio communication unit  3  converts the signal from control unit  9  into radio wave which is accordingly radiated from antenna  2 . The signal sent from antenna  2  is transmitted to electric power company  46  (S 58 ).  
         [0077]    Communication unit  32  of server system  45  receives, from mobile receptacle  42 , the ID code of mobile receptacle  42 , the ID code of power feeding gate device  41 , and the key code request signal of power feeding gate device  41 , and transmits the signal to control unit  31  (S 60 ). Control unit  31  reads from storage unit  34  which stores information about power feeding gate device  41 , a key code for turning switch  22  on that corresponds to the ID code of power feeding gate device  41 , and transmits the key code to communication unit  32  (S 62 ). Communication unit  32  sends the key code in return to mobile receptacle  42  (S 64 ). After this, a process is carried out that is the same as the process starting from step S 20  of FIG. 8, which is performed when mobile receptacle  42  receives the key code of power feeding gate device  41  from server system  45  of electric power company  46 .  
         [0078]    Referring to FIG. 11, if the retry number is equal to or greater than the upper limit of retry number (YES in S 56 ), a process is carried out which is the same as that performed when mobile receptacle  42  determines that power feeding gate device  41  is unavailable. More specifically, control unit  9  of mobile receptacle  42  transmits, to radio communication unit  3 , the ID code of power feeding gate device  41  which is temporarily stored in storage unit  4 , the unavailability signal (indicating that power feeding gate device  41  cannot be used) that is stored in advance in storage unit  4 , and the ID code of mobile receptacle  42  stored in storage unit  4 . Radio communication unit  3  converts the signal from control unit  9  into radio wave which is accordingly radiated from antenna  2 . The signal from antenna  2  is transmitted to electric power company  46  (S 66 ). Control unit  9  shows on display unit  6  that power feeding gate device  41  is unavailable (S 68 ) to finish using power feeding gate device  41 .  
         [0079]    Communication unit  32  in server system  45  of electric power company  46  receives the ID code of power feeding gate device  41 , the signal for informing that power feeding gate device  41  is unavailable, and the ID code signal of mobile receptacle  42 , and transmits the signal and codes to control unit  31  (S 70 ). Control unit  31  records occurrence of fault as fault information stored in storage unit  34  which stores information about power feeding gate device  41  (S 72 ). A person in charge in power company  46  checks the fault information in system maintenance to effect repair for the fault (S 74 ).  
         [0080]    Referring to FIG. 12, when external equipment or machine, for example, electric vehicle  43  finishes using the electric power and accordingly mobile receptacle  42  is detached from power feeding gate device  41 , an operation is carried out as described below.  
         [0081]    When the usage of power is finished, a user powers off the external equipment (S 82 ) and detaches mobile receptacle  42  from power feeding gate device  41  (S 84 ). Then, a signal indicating that mobile receptacle  42  is detached from power feeding gate device  41  is transmitted from sensor  10  of power feeding gate device  41  to control unit  9 . In response to this signal, control unit  9  transmits to radio communication unit  3  a value measured by power usage integrating meter  13 , the ID code of mobile receptacle  42  stored in storage unit  4 , and the usage finish notification signal stored in advance in storage unit  4 . Radio communication unit  3  converts the signal received from control unit  9  into radio wave which is accordingly radiated from antenna  2 . The signal from antenna  2  is transmitted to power company  46  (S 86 ).  
         [0082]    After the step S 84  of detaching mobile receptacle  42  from power feeding gate device  41 , a signal indicating the detachment of mobile receptacle  42  from power feeding gate device  41  is sent from connection detecting sensor  27  contained in power feeding gate device  41  to control unit  24  (S 88 ). Control unit  24  thus receives this signal to turn switch  22  off (S 90 ). Accordingly, supply of electric power to interface circuit  23  is stopped.  
         [0083]    On the other hand, after the step S 86 , communication unit  32  in server system  45  of electric power company  46  receives the ID code of mobile receptacle  42 , the value measured by the power usage integrating meter contained in mobile receptacle  42  and the usage finish notification signal and transmits them to control unit  31  (S 92 ).  
         [0084]    Control unit  31  reads the time indicated by clock  37  to store the time, as the time when usage of power feeding gate device  41  is finished, in storage unit  35 , and then increases by one the number of times power feeding gate device  41  is used that is stored in storage unit  35 . The value indicated at the usage finish time (when usage of power feeding gate device  41  is finished) by the power usage integrating meter contained in mobile receptacle  42  is then recorded in storage unit  35  (S 94 ).  
         [0085]    Control unit  31  subtracts, from the value at the usage finish time, the value at the usage start time (when usage of power feeding gate device  41  is started) that is indicated by power usage integrating meter contained in mobile receptacle  42 , in order to determine the amount of used power. This power amount is recorded in both of the area of power usage amount of mobile receptacle  42  in storage unit  35  and the area of power usage amount of power feeding gate device  41  (S 96 ). Control unit  31  determines a fee for this amount of used power (S 98 ) and records this fee in the area of power fee of mobile receptacle  42  in storage unit  35  (S 100 ).  
         [0086]    Control unit  31  records the time when it receives the usage finish notification signal in storage unit  34 , specifically in the area of usage finish time of power feeding gate device  41  (S 102 ). Control unit  31  transmits the power usage fee and the power usage amount to communication unit  32 . Communication unit  32  transmits the power usage amount and the power usage fee to mobile receptacle  42  (S 104 ).  
         [0087]    Radio communication unit  3  of mobile receptacle  42  thus receives the signal representing the power usage amount and the power usage fee from electric power company  46  through antenna  2 , and this signal is input to radio communication unit  3  (S 106 ). Radio communication unit  3  converts the signal to an electric signal which is transmitted to control unit  9 . Control unit  9  thus shows the received power usage amount and the power usage fee on display unit  6  (S 108 ) and the user finishes using this system.  
         [0088]    Referring to FIG. 13, the power usage management system may employ a power line  67  through which signals can be transmitted, instead of the communication line and power line. Specifically, by means of power line  67 , mobile receptacle  42  and power feeding gate device  41 , power feeding gate device  41  and power feeding source  44 , and power feeding gate device  41  and server system  45  are connected.  
         [0089]    According to the description above, radio communication unit  3 , power usage integrating meter  13  and receptacle  15  are provided within mobile receptacle  42 . However, these components may be provided within power feeding gate device  41 .  
         [0090]    The ID code of mobile receptacle  42 , and the value indicated by power usage integrating meter  13  provided within mobile receptacle  42  may be transmitted to power company  46  at regular intervals. In this case, if such a signal is not transmitted to power company  46  within the interval, power company  46  accordingly determines that any fault occurs in mobile receptacle  42 . Then, power company  46  calculates the power usage fee by using any value indicated by power usage integrating meter  13  that the power company receives last.  
         [0091]    Instead of using power usage integrating meter  13 , the fee for using mobile receptacle  42  may be determined as a flat monthly rate.  
         [0092]    It may naturally possible to connect any electric power-driven product other than electric vehicle  43  to mobile receptacle  42 .  
         [0093]    As discussed above, power feeding gate device  41  has a simple structure and thus can be installed at any place where power line  47  is provided. Power feeding gate device  41  can thus be installed near the power mains to enable the user to obtain large electric power. As power feeding gate device  41  can easily be installed, power feeding gate devices  41  may be placed at an increased number of installation sites. This means that electric vehicle  43  may have its battery reduced in size which accordingly shorten the time required for charging the battery. Then, it is possible to reduce the weight of the body of the vehicle as well as the cost of the vehicle, and accordingly widespread use of electric vehicle  43  is promoted.  
         [0094]    Power feeding gate device  41  is placed outside as an AC receptacle, which means that device  41  can be used for charging electric vehicle  43  and which eliminates the above described problems or inconveniences that the electric power can be used only when the power vending locker is closed, and that only those products which is small enough to be held in the power vending locker can be supplied with the power by the locker.  
         [0095]    Since radio communication unit  3  transmits information regarding power usage to electric power company  46 , the user can utilize the electric power when the user has no cash at hand.  
         [0096]    In addition, since there is no need for fuel as required by the power generator using a gasoline engine for example, the problem of noise and exhausted gas is eliminated.  
         [0097]    Moreover, based on the installation site of power feeding gate device  41  as well as the status of usage of mobile receptacle  42 , the area-based and time-based power usage status can be examined. Then, a power supply line can be established that achieves well-balanced supply and demand.  
         [0098]    Further, any person in charge in electric power company  46  can know the frequency of usage according to information about usage history of power feeding gate device  41 . For example, in summer, power feeding gate devices  41  are used with greater frequency near seaside resorts and with smaller frequency near ski resorts. On the other hand, in winter, power feeding gate devices  41  are used with greater frequency near ski resorts and with smaller frequency near seaside resorts. Then, according to this information about usage of the devices, the person in charge in electric power company  46  moves power feeding gate devices  41  placed near ski resorts to places near seaside resorts in summer, and moves power feeding gate devices  41  placed near seaside resorts to places near ski resorts in winter. In this way, efficient use of power feeding gate devices  41  that are relatively small in number is possible.  
         [0099]    Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.