Abstract:
A wind turbine generator capable of preventing a salt damage and reducing noise as well as easily starting in a cold region is provided. The wind turbine generator includes a nacelle ( 3 ) for accommodating a generator set, an internal heat exchanging unit ( 13, 15, 16 ) accommodated in the nacelle ( 3 ) to exchange heat between the generator set and a refrigerant, an external heat exchanging unit ( 17 ) disposed outside the nacelle ( 3 ) to exchange heat between an outside air and the refrigerant, a compressor ( 18 ) disposed in the nacelle ( 3 ) to compress the refrigerant and circulate the refrigerant between the internal heat exchanging unit ( 13, 15, 16 ) and the external heat exchanging unit ( 17 ), and an expansion unit ( 19 ) to expand the refrigerant compressed by the compressor ( 18 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a wind turbine generator. 
     BACKGROUND ART 
     As conventional means for converting wind power energy into thermal energy, wind power energy is converted into electric energy, the converted electric energy is converted into thermal energy through a heat pump (see PTL 1 and 2 for example). 
     For example, “a cooling system using a wind turbine and a heat pump” announced in 1987 is known as an apparatus for driving a heat pump. This system converts wind power energy into electric energy by means of a wind turbine, the electric energy is charged into a secondary battery, and a refrigeration cycle (the heat pump) is operated by a DC generator. 
     As an example of the combination of a wind turbine and a heat pump, there is known a system in which a heat pump (a refrigeration cycle) is disposed outside the wind turbine, mechanical energy obtained by the wind turbine is transmitted through a rotation shaft passing through a tower, a compressor of the heat pump is driven to convert the mechanical energy into thermal energy, as described in PTL 2. 
     CITATION LIST 
     Patent Literature 
     
         
         {PTL 1} 
         Specification of U.S. Patent Application No. 2007/0024132 
         {PTL 2} 
         The Publication of Japanese Patent No. 3949946 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, a large wind turbine having several MW output is used as recent commercial wind turbine generators. In a case where such a large wind turbine and a heat pump are combined with each other, the following problems are caused. 
     Specifically, when the wind turbine is increased in size, the tower is increased in height (e.g., 50 m to 70 m). Therefore, there is a problem that a rotation shaft passing through the tower for transmitting power becomes long and heavy, and loss of mechanical energy converted from wind power energy is largely increased. 
     Further, a radiation amount of heat radiated from a machine disposed in a nacelle, e.g., a gear box, a main bearing, a transformer and a generator is several % of output of the wind turbine generator (e.g., 100 kW to 300 kW), but there is a problem that in Patent Citations referred to above, a cooling system for dealing with the heat is unclear. 
     Generally, the outside air is introduced into a nacelle through an air intake such as a louver provided in the nacelle, and devices in the nacelle are cooled by the introduced outside air. That is, using the cooling system, heat is dissipated to the outside air introduced from a cooler of the cooling system, and the outside air of which heat is absorbed is discharged outside of the nacelle. 
     When the wind turbine is disposed at sea or at seaside, however, since outside air containing salt is introduced into the nacelle, there is a problem that lifetime of a device in the nacelle is shortened by salt. 
     When the wind turbine generator is disposed near a house, there is caused a problem of noise from the cooling system, e.g., noise caused by rotation of a cooler fan. In addition, an application range of a large wind turbine generator is expanded to a cold region, but since there is no cooling system (heat pump) in the nacelle, there is a problem that the wind turbine generator cannot be applied to the cold region. 
     The present invention has been accomplished to solve the above problems, and it is an object of the present invention to provide a wind turbine generator capable of preventing salt damage, capable of reducing noise, and capable of easily starting in the cold region. 
     Solution to Problem 
     To achieve the above object, the present invention provides the following solutions. 
     According to an aspect of the present invention, a wind turbine generator includes: a nacelle for accommodating a generator set; an internal heat exchanging unit accommodated in the nacelle to exchange heat between the generator set and refrigerant; an external heat exchanging unit disposed outside the nacelle to exchange heat between outside air and the refrigerant; a compressor disposed in the nacelle to compress the refrigerant and circulate the refrigerant between the internal heat exchanging unit and the external heat exchanging unit; and an expansion unit to expand a pressure of the refrigerant compressed by the compressor. 
     According to this aspect, for example, a refrigerant is circulated from a compressor through an external heat exchanging unit, an expansion unit, an internal heat exchanging unit, and the compressor in this order so as to constitute a refrigeration cycle. With this, heat generated in a device disposed in the nacelle, e.g., generated in a generator set can be radiated outside of the nacelle via the refrigerant. That is, heat of a device in the nacelle can sufficiently be radiated outside the nacelle even if the nacelle is not provided with an opening through which the outside air is introduced into the nacelle. Thus, it is possible to prevent the outside air including salt from flowing into the nacelle. Further, noise generated from the device in the nacelle does not leak outside of the nacelle. 
     If a refrigerant is circulated in a direction opposite from that described above, i.e., from the compressor through the internal heat exchanging unit, the expansion unit, the external heat exchanging unit and the compressor in this order so as to constitute a heat pump cycle, the device in the nacelle can be heated. When a wind turbine generator is started when the outside air is cold, even if it is necessary to heat a lubricant such as oil used for the device in the nacelle to lower its viscosity, it is possible to easily heat the lubricant such as oil. 
     In the above aspect, preferably, there is further included a wind turbine to supply a rotation driving force to the generator set using wind power, wherein the compressor is driven by the rotation driving force supplied by the wind turbine. 
     According to this structure, the compressor is driven using a rotation driving force supplied by branching the wind turbine energy. Therefore, a heat exchanging ability in the internal heat exchanging unit, i.e., a cooling ability of the generator set is changed in accordance with the number of revolutions of the wind turbine or the rotation torque. In other words, the cooling ability of the generator set is automatically controlled by the rotation driving force supplied from the wind turbine. 
     For example, if the rotation driving force supplied to the compressor is increased, a mass flow rate of a refrigerant discharged in the compressor is increased. Thus, the heat exchanging ability in the internal heat exchanging unit is enhanced, and the cooling ability of the generator set is automatically controlled such that the ability is enhanced. 
     In the above aspect, preferably, there is further included a motor to rotate and drive the compressor. 
     According to this structure, for example, by driving the compressor using electricity generated by the generator set, the heat exchanging ability in the internal heat exchanging unit, i.e., the cooling ability of the generator set is changed in accordance with the output of the wind, turbine generator. In other words, the cooling ability of the generator set is automatically controlled by the electricity supplied by the generator set. 
     For example, if the electricity supplied to the compressor is increased, a mass flow rate of a refrigerant discharged in the compressor is increased. Thus, the heat exchanging ability in the internal heat exchanging unit is enhanced, and the cooling ability of the generator set is automatically controlled such that the ability is enhanced. 
     In the above aspect, preferably, the external heat exchanging unit is provided with a heater to supply heat to the refrigerant. 
     According to this structure, when refrigerant is evaporated using the external heat exchanging unit as an evaporator, even when the outside air temperature outside the nacelle is low, the refrigerant can easily be evaporated by heating the refrigerant using a heater. Further, heat can be supplied to the main body of the external heat exchanging unit and a piping system to the external heat exchanger. When it is necessary to heat lubricant such as oil used for the generator set to lower its viscosity, it is possible to easily heat the lubricant such as oil. 
     Advantageous Effects of Invention 
     According to the wind turbine generator of the present invention, by circulating a refrigerant from the compressor through the external heat exchanging unit, the expansion unit, the internal heat exchanging unit and the compressor in this order so as to constitute a refrigeration cycle, without an opening in the nacelle, heat of a device in the nacelle can sufficiently be radiated outside of the nacelle. Therefore, there is an effect that salt damage and noise can be reduced. Further, by circulating a refrigerant from the compressor through the internal heat exchanging unit, the expansion unit, the external heat exchanging unit and the compressor in this order so as to constitute a heat pump cycle, a device in the nacelle can be heated. Therefore, there is an effect that a wind turbine generator can easily be started in a cold region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a general view for explaining a structure of a wind turbine generator according to a first embodiment of the present invention. 
         FIG. 2  is a schematic diagram for explaining a structure of an interior of a nacelle shown in  FIG. 1 . 
         FIG. 3  is a schematic diagram for explaining a flow of a refrigerant when the wind turbine generator shown in  FIG. 2  is started from a cold state. 
         FIG. 4  is a schematic diagram for explaining a structure of a wind turbine generator according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A wind turbine generator according to a first embodiment of the present invention will be explained with reference to  FIGS. 1 to 3 . 
       FIG. 1  is a general view for explaining a structure of the wind turbine generator according to the present embodiment. 
     A wind turbine generator  1  produces electricity using wind power. 
     As shown in  FIG. 1 , the wind turbine generator  1  includes a column (a tower)  2  standing on a base B, a nacelle  3  provided on an upper end of the column  2 , a rotor head (wind turbine)  4  provided on the nacelle  3  such that the rotor head  4  can rotate around a substantially horizontal axis, a head capsule  5  covering the rotor head  4 , a plurality of wind turbine rotor blades (the wind turbine)  6  radially mounted around a rotation axis of the rotor head  4 , and a device in the nacelle (a generator set)  7  which generates electricity by rotating the rotor head  4 . 
     Although three wind turbine rotor blades  6  are provided in the present embodiment of the invention, the number of the wind turbine rotor blades  6  is not limited to three, but the number may be two, four or more with no particular limitation. 
     As shown in  FIG. 1 , the column  2  extends upward from the base B (upward in  FIG. 1 ), and a plurality of units is connected in the vertical direction or the like. The uppermost portion of the column  2  is provided with the nacelle  3 . When the column  2  includes the plurality of units, the nacelle  3  is disposed on the uppermost unit. 
     As shown in  FIG. 1 , the nacelle  3  rotatably supports the rotor head  4 , and the device  7  in the nacelle for generating electricity by rotating the rotor head  4  is accommodated in the nacelle  3 . 
     The nacelle  3  is not provided with a venting opening (a louver) through which the outside air is introduced into the nacelle  3  from outside the nacelle  3 , and the nacelle  3  is only provided with an opening for allowing a main shaft (not shown) for transmitting a rotation driving force of the rotor head  4  to pass through, and a doorway for maintenance. 
     As shown in  FIG. 1 , the plurality of wind turbine rotor blades  6 , which radially extends, is mounted on the rotor head  4  around the rotation axis thereof, and the periphery, of the rotor head  4  is covered with the head capsule  5 . 
     The rotor head  4  is provided with a pitch control unit (not shown) which rotates the wind turbine rotor blade  6  around an axis of the wind turbine rotor blade  6  to change a pitch angle of the wind turbine rotor blade  6 . 
     In this structure, when a wind hits the wind turbine rotor blades  6  from a direction of the rotation axis of the rotor head  4 , a force for rotating the rotor head  4  around its rotation axis is generated in the wind turbine rotor blades  6 , and the rotor head  4  is rotated and driven. 
       FIG. 2  is a schematic diagram for explaining a structure of an interior of the nacelle shown in  FIG. 1 . 
     As shown in  FIG. 2 , a device  7  in the nacelle accommodated in the nacelle  3  is provided with a main bearing  11  which rotatably supports a main shaft (not shown). The main shaft transmits a mechanical rotation driving force of the rotor head  4  to a generator  14 . The device  7  in the nacelle is also provided with a gear box (generator set)  12  which accelerates rotation of the rotor head  4  and transmits the rotation to the generator  14 , an oil heat exchanging unit (internal heat exchanging unit)  13  which cools or heats oil used for lubricating the main bearing  11  and the gear box  12 , the generator (generator set)  14  which generates electricity using the transmitted mechanical rotation driving force, a generator heat exchanging unit (internal heat exchanging unit)  15  which cools or heats the generator  14 , and an inverter heat exchanging unit (internal heat exchanging unit)  16  which cools or heats an inverter. The inverter controls voltage and frequency of generated electricity. The device  7  in the nacelle is also provided with an external heat exchanging unit  17  which exchanges heat between a refrigerant and the outside air outside the nacelle  3 , a compressor  18  which circulates a refrigerant between the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , the inverter heat exchanging unit  16  and the external heat exchanging unit  17 . The device  7  in the nacelle is also provided with an expansion valve (expansion unit)  19  which expands a pressure of a compressed refrigerant. 
     The main bearing  11  includes a bearing tank  22  and a bearing pump  21  which pumps lubricant oil (lubricant) for lubricating inside the main bearing  11 . The bearing pump  21  and the bearing tank  22  constitute a circulation path for lubricant oil together with the main bearing  11  and the oil heat exchanging unit  13 . 
     The main bearing tank  22  includes a main bearing heater (heater)  23  for heating lubricant oil stored therein. 
     The gear box  12  transmits a mechanical rotation driving force transmitted from the rotor head  4  to the generator  14  and to the compressor  18 . The number of revolutions, i.e., the rotation speed of the rotation driving force transmitted to the generator  14  and the compressor  18  is increased. 
     The gear box  12  includes a gear box tank  32  and a gear box pump  31  which pumps lubricant oil for lubricating inside the gear box  12 . The gear box pump  31  and the gear box tank  32  constitute a circulation path for lubricant oil together with the gear box  12  and the oil heat exchanging unit  13 . 
     The gear box tank  32  is provided with a gear box heater (heater)  33  which heats lubricant oil stored therein. 
     The oil heat exchanging unit  13  is a heat exchanger into which lubricant oil that lubricated the main bearing  11  and the gear box  12  flows. The oil heat exchanging unit  13  exchanges heat between a refrigerant circulated by the compressor  18  and a lubricant oil. 
     In a state where a viscosity of the lubricant oil is sufficiently low and the wind turbine generator  1  is operated, the oil heat exchanging unit  13  is used as an evaporator and the lubricant oil radiates heat to the refrigerant. 
     On the other hand, when the wind turbine generator  1  is started when the outside air is cold and a viscosity of lubricant oil is high, the oil heat exchanging unit  13  is used as a condenser, and a refrigerant radiates heat to lubricant oil. 
     The oil heat exchanging unit  13  is connected such that a refrigerant which flowed out from the oil heat exchanging unit  13  flows into the compressor  18 , the external heat exchanging unit  17 , and the expansion valve  19  in this order in a state where a viscosity of lubricant oil is sufficiently low and the wind turbine generator  1  is operated, and a refrigerant passing through the expansion valve  19  again flows into the oil heat exchanging unit  13 . By circulating the refrigerant in this manner, a refrigeration cycle is constituted. 
     The generator heat exchanging unit  15  is a heat exchanger disposed in adjacent to the generator  14 , and radiates heat generated by the generator  14  to a refrigerant. 
     The generator heat exchanging unit  15  is connected such that a refrigerant which flowed out from the generator heat exchanging unit  15  flows into the compressor  18 , the external heat exchanging unit  17 , and the expansion valve  19  in this order in a state where the wind turbine generator  1  is operated, and a refrigerant passing through the expansion valve  19  again flows into the generator heat exchanging unit  15 . By circulating a refrigerant in this manner, a refrigeration cycle is constituted. 
     The inverter heat exchanging unit  16  is a heat exchanger disposed behind the nacelle  3 , and radiates heat generated by an inverter (not shown) to a refrigerant. 
     The inverter heat exchanging unit  16  is connected such that a refrigerant which flowed out from the inverter heat exchanging unit  16  flows into the compressor  18  and the external heat exchanging unit  17  in this order in a state where the wind turbine generator  1  is operated, and a refrigerant passing through the expansion valve  19  again flows into the inverter heat exchanging unit  16 . By circulating a refrigerant in this manner, a refrigeration cycle is constituted. 
     The external heat exchanging unit  17  exchanges heat between a refrigerant and the outside air, and is disposed on a lower surface behind the nacelle  3 . 
     The external heat exchanging unit  17  is connected such that a refrigerant which flowed out from the external heat exchanging unit  17  flows into the expansion valve  19 , any of the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , and the inverter heat exchanging unit  16 , and the compressor  18  in this order in a state where the wind turbine generator  1  is operated, and a refrigerant which is discharged from the compressor  18  again flows into the external heat exchanging unit  17 . By circulating a refrigerant in this manner, a refrigeration cycle is constituted. 
     The external heat exchanging unit  17  is provided with an external heat exchanging heater (heater)  41  which heats lubricant oil stored in a main body of the external heat exchanging unit  17  or in a piping system connected to the external heat exchanging unit  17 . It is preferable to provide a shower (not shown) for washing off salt adhered to the external heat exchanging unit  17  to prevent the external heat exchanging unit  17  from being corroded by salt of the external heat exchanging unit  17 . 
     In the case of a refrigeration cycle which absorbs heat of a refrigerant in the oil heat exchanging unit  13 , the compressor  18  compresses a refrigerant and discharges the refrigerant into the external heat exchanging unit  17 . In the case of a heat pump cycle which supplies heat to a refrigerant in the oil heat exchanging unit  13 , the compressor  18 , compresses a refrigerant and discharges the refrigerant toward the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , and the inverter heat exchanging unit  16 . 
     A mechanical rotation driving force is transmitted to the compressor  18  from the rotor head  4  through the gear box  12 , and the compressor  18  compresses a refrigerant by the transmitted mechanical rotation driving force. In the present embodiment, the compressor  18  switches a discharging direction of a refrigerant. That is, the compressor  18  discharges a refrigerant to the external heat exchanging unit  17  in the case of a refrigeration cycle, and the compressor  18  discharges a refrigerant to the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , and the inverter heat exchanging unit  16  in the case of a heat pump cycle. 
     A compressor capable of switching a discharging direction of a refrigerant may be used as described above, or a compressor which discharges a refrigerant only in one direction, and a three-way valve or a four-way valve which controls a flowing direction of a refrigerant may be used, and this is not especially limited. 
     An outline of an electricity generating method in the wind turbine generator  1  having the above-described structure will be explained. 
     In the wind turbine generator  1 , wind power energy which hits the wind turbine rotor blade  6  from a rotation axial direction of the rotor head  4  is converted into mechanical energy which rotates the rotor head  4  around the rotation axis. 
     Rotation of the rotor head  4  is transmitted to the device  7  in the nacelle. In the device  7  in the nacelle, electricity, e.g., AC electricity having frequency of 50 Hz or 60 Hz suitable for a subject to which electricity is supplied is generated. 
     At least while electricity is generated, in order to effectively apply wind power energy to the wind turbine rotor blade, the nacelle  3  is appropriately rotated on a horizontal plane, thereby controlling the rotor head  4  such that it is oriented to an upstream direction of wind. 
     Next, as the feature of the present embodiment, the heat exchanging operation in the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , the inverter heat exchanging unit  16  and the external heat exchanging unit  17  will be explained. 
     When electricity is generated in the wind turbine generator  1 , to constitute a refrigeration cycle as shown in  FIG. 2 , the oil heat exchanging unit  13 , the generator heat exchanging unit  15  and the inverter heat exchanging unit  16  act as a cooler (evaporator). That is, a refrigerant absorbs heat in the oil heat exchanging unit  13  and the like and evaporates the refrigerant. The external heat exchanging unit  17  acts as a condenser, and a refrigerant radiates heat to the outside air and is condensed. 
     More specifically, a refrigerant is compressed to have a high temperature and high pressure by the compressor  18  to which a mechanical rotation driving force of the rotor head  4  is transmitted through the gear box  12 , and the refrigerant is discharged toward the external heat exchanging unit  17 . The refrigerant which flowed into the external heat exchanging unit  17  radiates heat to the outside air in the external heat exchanging unit  17  and is condensed. The condensed and liquefied refrigerant flows into the expansion valve  19  and is expanded when the refrigerant passes through the expansion valve  19 . The expanded refrigerant flows into the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , and the inverter heat exchanging unit  16 . 
     The refrigerant which flowed into the oil heat exchanging unit  13  lubricates the main bearing  11  and the gear box  12  in the oil heat exchanging unit  13 , the refrigerant absorbs heat from the high temperature lubricant oil and is evaporated. The evaporated refrigerant flows out from the oil heat exchanging unit  13 , flows into the compressor  18 , and is compressed again. 
     Lubricant oil for main bearing of which heat is removed and which is cooled is circulated through the bearing tank  22 , the bearing pump  21 , and the main bearing  11  in this order and again flows into the oil heat exchanging unit  13 . Lubricant oil for the gear box is circulated through the gear box  12 , the gear box tank  32 , and the gear box pump  31  in this order and again flows into the oil heat exchanging unit  13 . 
     The refrigerant which flows into the generator heat exchanging unit  15  absorbs heat generated from the generator  14  in the generator heat exchanging unit  15  and is evaporated. The evaporated refrigerant flows out from the generator heat exchanging unit  15 , flows into the compressor  18 , and is again compressed. 
     The refrigerant which flows into the inverter heat exchanging unit  16  absorbs heat generated from the inverter  14  in the inverter heat exchanging unit  16  and is evaporated. The evaporated refrigerant flows out from the inverter heat exchanging unit  16 , flows into the compressor  18  and is again compressed. 
       FIG. 3  is a schematic diagram for explaining a refrigerant flow when the wind turbine generator shown in  FIG. 2  is started from its cold state. 
     When the wind turbine generator  1  is started under such an environment in which the outside air temperature is, for example, −30° to −40°, i.e., when the wind turbine generator  1  is started in a state where a viscosity coefficient of lubricant oil which lubricates the main bearing  11  and the gear box  12  is as high as a few ten thousand cSt and lubrication ability cannot be expected, a circulation direction of a refrigerant is set to a direction opposite from that shown in  FIG. 2 , i.e., a refrigerant is allowed to flow so as to constitute a heat pump cycle instead of a refrigeration cycle, and lubricant oil is heated. 
     More specifically, a refrigerant compressed by the compressor  18  to have a high temperature and high pressure is discharged toward the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , and the inverter heat exchanging unit  16 . 
     The high temperature and high pressure refrigerant which flowed into the oil heat exchanging unit  13  discharges heat to lubricant oil which lubricates the main bearing  11  and the gear box  12  and is condensed. The condensed refrigerant flows out from the oil heat exchanging unit  13  and flows into the expansion valve  19 . 
     Lubricant oil which absorbs heat discharged from the refrigerant and which is heated is lowered in viscosity to such a level that lubricating ability can be expected. The lubricant oil flows out from the oil heat exchanging unit  13  and then, the lubricant oil is supplied to the main bearing  11  and the gear box  12  and used for lubrication. 
     As described above, only heat of a refrigerant may be used and the lubricant oil may be heated, or the bearing heater  23  may further be used to heat the lubricant oil, or the gear box heater  33  may further be used to heat the lubricant oil. The heating method of lubricant oil is not especially limited to heating from a refrigerant. 
     A refrigerant flows into the expansion valve  19  from the oil heat exchanging unit  13 , the generator heat exchanging unit  15 , and the inverter heat exchanging unit  16 , and when the refrigerant passes through the expansion valve  19 , the refrigerant is expanded. The expanded refrigerant flows into the external heat exchanging unit  17 . 
     An external heat exchanging heater  41  is disposed in a main body of the external heat exchanging unit  17  or in a piping system connected to the external heat exchanging unit  17 . A refrigerant heated by the external heat exchanging heater  41  is evaporated, and the evaporated refrigerant flows into the compressor  18  and is again compressed. 
     As described above, a refrigerant may be evaporated by the main body of the external heat exchanging unit  17  or the external heat exchanging heater  41  disposed on the piping system connected to the external heat exchanging unit  17 , or a refrigerant may be evaporated by an other heating device (not shown). The evaporating device of a refrigerant is not especially limited. 
     According to the above structure, for example, in a generator system of the wind turbine generator  1  disposed on the ocean, if a refrigerant is circulated from the compressor  18  through the external heat exchanging unit  17 , the expansion valve  19 , the generator heat exchanging unit  15  and the like and again the compressor  18  in this order, heat generated in the generator  14  can be radiated outside the nacelle  3  through the refrigerant. That is, it is possible to sufficiently radiate heat of the generator set outside the nacelle  3  without directly introducing the outside air including salt into the nacelle  3  from outside the nacelle  3 , and it is possible to prevent lifetime of the wind turbine generator  1  from being shortened. As well as the generator  14 , this effect can be expected also in the device  7  in the nacelle such as the main bearing  11 , the gear box  12  and the inverter. 
     Further, since noise generated from the generator  14  and a cooler fan of the gear box  12  is enclosed in the nacelle  3 , it is possible to prevent noise from leaking outside of the wind turbine generator  1 . 
     If a refrigerant is circulated from the compressor  18  through the oil heat exchanging unit  13 , the expansion valve  19 , and the external heat exchanging unit  17 , and again the compressor  18  this order to constitute a heat pump cycle, oil in the gear box  12  and the main bearing  11  can be heated. For example, when the wind turbine generator  1  is started in a state where the outside air temperature is as cold as −30° to −40°, even if it is necessary to heat lubricant oil used for the gear box  12  and the main bearing  11  and to lower the viscosity of the lubricant oil to such a level that lubricating ability can be expected, it is possible to easily heat the lubricant oil and easily start the wind turbine generator  1 . 
     If a refrigerant is heated using the main body of the external heat exchanging unit  17  or the external heat exchanging heater  41  disposed on the piping system connected to the external heat exchanging unit  17 , it is possible to easily evaporate the refrigerant. Therefore, even when it is necessary to increase the temperature of lubricant oil used for the gear box  12  or the main bearing  11  and to lower the viscosity of the lubricant oil to such a level that lubricating ability can be expected, it is possible to make it easier to start the wind turbine generator  1 . 
     Since the compressor  18  is driven using a mechanical rotation driving force supplied by the rotor head  4 , the heat exchanging ability in the oil heat exchanging unit  13 , i.e., cooling ability of lubricant oil in the generator  14  or the gear box  12  is changed in accordance with the number of revolutions and the rotation torque of the rotor head  4 . In other words, the cooling ability of the generator  14  or the gear box  12  is automatically controlled by the mechanical rotation driving force supplied by the wind turbine generator  1 . 
     For example, when the rotation driving force supplied to the compressor  18  is increased, a mass flow rate of a refrigerant discharged in the compressor  18  is increased. Therefore, control is performed such that the heat exchanging ability in the oil heat exchanging unit  13  is enhanced and the cooling ability in the cooler of the generator  14  or the gear box  12  is enhanced. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be explained with reference to  FIG. 4 . 
     The basic structure of the wind turbine generator of the present embodiment is the same as that of the first embodiment, but the driving method of the compressor is different from that of the first embodiment. Therefore, in the present embodiment, only the structure of the periphery of the compressor will be explained with reference to  FIG. 4 , and explanation of other structures will not be repeated. 
       FIG. 4  is a schematic diagram for explaining the structure of the wind turbine generator according to the present embodiment. 
     The same constituent elements as those of the first embodiment are designated with the same symbols, and explanation thereof will not be repeated. 
     As shown in  FIG. 4 , a generator set  107  accommodated in a nacelle  3  in a wind turbine generator  101  includes a main bearing  11 , a gear box  12 , an oil heat exchanging unit  13 , a generator  14 , a generator heat exchanging unit  15 , an inverter heat exchanging unit  16 , an external heat exchanging unit  17 , a compressor  18 , an expansion valve  19 , and an electric motor (a motor)  118  which rotates and drives the compressor  18 . 
     Electricity generated by the generator  14  is supplied to the electric motor  118 , and the motor  118  rotates and drives the compressor  18  using the supplied electricity. 
     When electricity is generated in the wind turbine generator  101 , the compressor  18  rotated and driven by the electric motor  118  discharges a refrigerant compressed to have a high temperature and high pressure toward the external heat exchanging unit  17 . Since the operation thereafter is the same as that of the first embodiment, explanation thereof will not be repeated. 
     According to the above structure, since the compressor  18  is driven using electricity generated by the generator  14 , the heat exchanging ability in the oil heat exchanging unit  13 , i.e., cooling ability in a cooler of the generator  14  or the gear box  12 , is changed in accordance with output of the wind turbine generator  101 . In other words, the cooling ability of the cooler of the generator  14  or the gear box  12  can be automatically controlled by the electricity supplied from the generator  14 . 
     For example, when supplied electricity is increased, a mass flow rate of a refrigerant discharged in the compressor  18  is increased. Therefore, control is performed such that the heat exchanging ability in the oil heat exchanging unit  13  is enhanced and the cooling ability in the cooler of the generator  14  or the gear box  12  is enhanced. 
     REFERENCE SIGNS LIST 
     
         
           1 ,  101 : Wind turbine generator 
           3 : Nacelle 
           4 : Rotor head (Wind turbine) 
           6 : Wind turbine rotor blade (Wind turbine) 
           7 : Device in nacelle (Generator set) 
           12 : Gear box (Generator set) 
           13 : Oil heat exchanging unit (Internal heat exchanging unit) 
           14 : Generator (Generator set) 
           15 : Generator heat exchanging unit (Internal heat exchanging unit) 
           16 : Inverter heat exchanging unit (Internal heat exchanging unit) 
           17 : External heat exchanging unit 
           18 : Compressor 
           19 : Expansion valve (Decompression unit) 
           23 : Bearing heater (Heater) 
           33 : Gear box heater (Heater) 
           41 : External heat exchanging heater (Heater) 
           118 : Motor