Abstract:
If an inverter is merely attached to the back side of a solar battery module, the inverter becomes an obstacle to transport and installation, it may be broken if it strikes a building structure at the time of installation and it may malfunction owing to impact with an object. Accordingly, a weather-resistant film, a first filler, a solar battery element, a second filler and a back reinforcing material are stacked in the order mentioned and the fillers are melted using a vacuum laminator to thereby seal the solar battery element in resin between the back reinforcing material and weather-resistant film. At this time an inverter is placed on the surface of the back reinforcing material that opposes the solar battery element.

Description:
FIELD OF THE INVENTION 
     This invention relates to a solar battery module and to a method of manufacturing the same. More particularly, the invention relates to a solar battery module having solar batteries and a power converter, a method of manufacturing the same and a power generating apparatus using this solar battery module. 
     BACKGROUND OF THE INVENTION 
     In an effort to tackle environmental problems, many types of solar power generating apparatus have been installed in recent years. Such an apparatus converts DC power, which has been generated by solar batteries, to AC power using an inverter, and supplies this AC power to a domestic load (hereinafter referred to simply as a “load” and/or a commercial power system (hereinafter referred to simply as a “system”). 
     A solar power generating apparatus of this kind is noteworthy also as an emergency power supply for use at the time of disasters such as earthquakes. A type of solar power generating apparatus that has appeared recently is detached from the system and is allowed to run independently to supply power to a load in the event of a power outage caused by an earthquake, system malfunction or maintenance. 
     Furthermore, an AC module is noteworthy as a small- to medium-size solar power generating apparatus or emergency power supply. Such an AC module includes an inverter, which is referred to as an MIC (Module Integrated Converter), attached to the back side of a solar power generating apparatus and adapted to convert DC power generated by solar batteries to AC power. Such an AC module makes it possible for a single solar battery module to output AC power. 
     The inverter included in the AC module can be attached to the solar battery module by various methods, such as mounting it directly on the back side of the solar battery module, connecting it to a terminal box or securing it to a frame, as described in the specification of Japanese Patent Application Laid-Open No. 9-271179. 
     If the inverter is attached to the back side of the solar battery module, however, various problems arise. Specifically, the inverter becomes an obstacle to transport and installation, it may be broken if it strikes a building structure at the time of installation and it may malfunction owing to impact with an object. 
     SUMMARY OF THE INVENTION 
     The present invention has been devised in order to solve, individually or collectively, the problems of the prior art described above, and an object thereof is to prevent damage to and a decline in the reliability of a power converter when a solar battery module is transported and installed. 
     According to the present invention, the foregoing object is attained by providing a solar battery device comprising: a solar battery; a power converter arranted to convert power output from the solar battery, wherein the solar battery and the power converter are integrated; and a metal plate for mounting the integrated solar battery and the power converter; wherein the power converter is placed at a position intermediate the solar battery and the metal plate. 
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram illustrating the structure of a solar battery module according to the present invention; 
     FIG. 2 is a diagram useful in describing in detail the mounting of an inverter in the solar battery module; 
     FIG. 3 is a diagram useful in describing in detail the mounting of an inverter in the solar battery module; 
     FIG. 4 is a perspective view of a solar battery module that has been worked into the shape of a roofing tile; 
     FIG. 5 is a diagram illustrating a method of installing a solar battery module in the shape of a roofing tile; and 
     FIG. 6 is a diagram showing another structure of a solar battery module according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of a solar battery module according to the present invention will now be described in detail. 
     Solar Battery Module 
     Though there is no particular limitation upon the solar battery elements and solar battery module used in this embodiment, examples of solar batteries that can be used as silicon-semiconductor photovoltaic elements are monocrystalline silicon solar batteries, polycrystalline silicon solar batteries and amorphous silicon solar batteries, and examples of solar batteries that can be used as compound-semiconductor photovoltaic elements are III-V-family compound solar batteries, II-VI-family compound solar batteries and I-III-VI-family compound solar batteries. 
     If an amorphous silicon solar battery is used in this embodiment, an advantage gained is that a decline in power generating efficiency is suppressed by the annealing effect. Furthermore, since an amorphous silicon solar battery can be formed as a thin film on a film substrate or electrically conductive substrate, the solar battery itself can be made light in weight. Such a solar battery is effective when it is integrated with a building material. 
     The non-light-receiving side of a solar battery module often has a terminal box for extracting power or an output cable structure to which is attached an output cable having a waterproof connector at its distal end. By connecting terminal boxes using an output cable or by connecting waterproof connectors together, a plurality of solar battery modules can be connected to construct a solar array. 
     An inverter for converting DC power, which is output from the solar batteries, to AC power is placed between the solar battery elements and a back reinforcing material of the solar battery module according to this embodiment. An output cable is led from the inverter of the solar battery module to the non-light-receiving side or to the side face of the module. By connecting these output cables of a plurality of solar battery modules, a solar battery array is constructed and power can be supplied to a load and/or linked to a system. 
     In a case where a DC/DC converter is used instead of the inverter, a solar battery module and solar array can be constructed in a similar manner. In such case collected DC power is converted to AC power by an inverter and the power is supplied to the load and/or linked to the system. 
     Furthermore, the solar battery module according to this embodiment preferably employs a weather-resistant transparent film as a material for protecting the surface of the module, and a steel plate, such as is used for metal roofing, as the back reinforcing material. The surface of the steel plate preferably is coated with a polyester resin or fluoroplastic in order to provide weather resistance. A solar battery module having such a structure can be formed into building material such as roofing material or wall material. In particular, an amorphous silicon solar battery using an electrically conductive substrate has a high mechanical strength and flexibility. Such a solar battery exhibits a high degree of freedom in terms of shaping and working and lends itself to the shape of roofs and walls. 
     Further, in a case where air is warmed utilizing the space between a roof and sarking, as disclosed in the specification of Japanese Patent Application Laid-Open No. 10-54118, a solar battery module using a steel plate as the back reinforcing material is effective. In particular, if the solar battery module is one having the inverter on the back side thereof, then the heat evolved by the inverter can be utilized effectively. 
     Inverter 
     The inverter comprises a booster circuit for boosting the DC voltage, which is output from the solar battery module, up to the input voltage of an inverter circuit, the inverter circuit for converting the boosted DC power to AC power, and a control circuit for controlling inverter start/stop, optimum operation of the solar batteries and the operating mode, etc. 
     A booster chopping circuit, a voltage doubler circuit and a serial-parallel chopper circuit, etc., can be used as the booster circuit. It is preferred that the inverter circuit be of voltage type, in which an IGBT or MOSFET is used as the switching element. The requisite output power can be obtained by driving the gate of the switching element based upon a control signal from the control circuit. Further, the control circuit has, e.g., a CPU, a PWM waveform controller, a frequency/voltage reference generator, a current reference generator, a mode changeover unit and a switching controller. 
     Further, it may be so arranged that the control circuit can be operated externally via a communication line or communication path. An arrangement may be adopted in which the control circuit per se is placed outside the inverter so that a plurality of inverters can be controlled collectively. 
     When the inverter operates, the switching elements used in the inverter and booster circuits, and a linking reactor produce heat. In order that such heat may escape efficiently, it is preferred that the material constituting the outer package of the inverter be a metal, especially aluminum or an alloy thereof. 
     The inverter in this embodiment is secured using a filler employed in the solar battery module. However, if the inverter is provisionally secured by adhesion or bonding with a thermal conductor interposed between the inverter and the back reinforcing material, operability when the solar battery module is fabricated will be improved. 
     It is preferred that the surface of the inverter package that opposes the back reinforcing material be formed to have recesses and protrusions as necessary. Since bringing the surface of the inverter package and the surface of the back reinforcing material into perfect contact is difficult in actuality, effecting this contact upon first embossing the surface of the inverter package will in effect provide greater surface area. It is preferred that the heat-radiating effect be enhanced by providing the inverter package surface with protrusions such as fins and inserting a thermal conductor between the package surface and the back reinforcing material. 
     The inverter preferably is fabricated so as to be as thin as possible. Producing a hybrid IC that contains a solar cell can be achieved using a thin-film inductor, as set forth in The Institute of Electrical Engineers of Japan, Technical Report (Section II), No. 449, though this involves a high degree of difficulty. 
     Thermal Conductor 
     The thermal conductor is interposed between the back reinforcing material of the solar battery module and the inverter and transmits heat evolved by the inverter to the back reinforcing material. 
     The thermal conductor preferably has the form of a gel, paste, grease, sheet or oil compound, though the member is not limited to these. An insulating or non-insulating material can be employed. Preferred examples of materials are metals or metal oxides such as mercury, aluminum and aluminum oxide or resins such as silicone, acrylic and epoxy resins containing an electrically conductive material. Among these materials, those exhibiting a stickiness, a thermocompression bonding property or an adhesive property can be used. In case of a material having such properties, the inverter can be secured to the back reinforcing material more strongly. 
     Structure of Solar Battery Module 
     FIG. 1 is a diagram illustrating the structure of a solar battery module  101 . 
     As shown in FIG. 1, the solar battery module  101  includes a weather-resistant film  102 , a back reinforcing material  103 , fillers  104  and  105 , a solar battery element  106 , an inverter  107  and lead wires  108 . 
     By stacking weather-resistant film  102 , filler  104 , solar battery element  106 , filler  105  and the back reinforcing material  103  in the order mentioned and melting the fillers  104  and  105  at 150° C. using a vacuum laminator, the solar battery module  101 , in which the solar battery element  106  is resin-sealed between the back reinforcing material  103  and weather-resistant film  102 , is created. 
     The inverter  107  is placed on the surface of the back reinforcing material  103  that opposes the solar battery element  106  and is disposed in such a manner that the package thereof is in direct contact with the back reinforcing material  103 . The latter has a hole through which the lead wires  108 , which extract AC power generated by the inverter  107 , are passed. 
     An opening for connecting the output terminals of the solar battery element  106  to the inverter  107  is provided in the filler  105  at a position corresponding to these terminals. 
     If the solar battery module  101  thus formed is subjected to a prescribed amount of solar radiation, DC power generated by the solar battery element  106  can be converted to AC power by the inverter  107  mounted on the back reinforcing material  103 . The solar battery module  101  delivers this AC power at its output. 
     A solar array that outputs AC power can also be constructed by connecting a plurality of the solar battery modules  101 . 
     Thus, the inverter  107  is fixed in the filler within the solar battery module  101 . When the solar battery module  101  is transported or installed, therefore, the inverter  107  will not strike building structures and it is possible to prevent damage to the inverter  107  and a decline in the reliability thereof. 
     Further, when the solar battery module  101  generates power and the inverter  107  operates, heat evolved by the inverter  107  can be transferred effectively to the back reinforcing material  103  of the solar battery module  101 . As a result, the heat evolved by the inverter  107  escapes efficiently and the reliability of the inverter  107  can be improved. 
     In a case where an amorphous silicon solar battery is used as the solar battery element  106 , an improvement in conversion efficiency can be expected owing to an annealing effect brought about by a rise in the temperature of the back reinforcing material  103 . 
     First Embodiment 
     FIG. 2 is a diagram useful in describing in detail the mounting of the inverter  107  in the solar battery module  101  illustrated in FIG.  1 . 
     The back reinforcing material  103  has a coating  203 . Before the inverter  107  is mounted on the back reinforcing material  103 , the portion of the coating  203  corresponding to an inverter mounting position  206  is removed by MEK (methyl ethyl ketone). After the coating  203  corresponding to the inverter mounting position  206  is removed, the inverter  107  is mounted on the back reinforcing material  103  and the solar battery module  101  is fabricated by carrying out the lamination process mentioned above. Of course, a thermal conducting material may be applied as necessary between the inverter  107  and back reinforcing material  103 . 
     When the solar battery module  101  having the structure shown in FIG. 2 generates AC power, the heat produced by the inverter  107  is transferred effectively to the back reinforcing material  103  because the coating  203  on the back reinforcing material  103  beneath the inverter  107  has been removed. The heat from the  107  therefore escapes efficiently so that the reliability of the inverter  107  is enhanced. 
     Second Embodiment 
     FIG. 3 is a diagram useful in describing in detail the mounting of the inverter  107  in the solar battery module  101  shown in FIG.  1 . 
     The inverter  107  has fins  306  provided at a fine pitch on its bottom side, and a thermal conductor  305  is interposed between the fins  306  and the back reinforcing material  103 . Mercury paste, for example, is used as the thermal conductor  305 , and the fins  306  and back reinforcing material  103  are brought into intimate contact so that the heat evolved by the inverter  107  will be transferred effectively to the back reinforcing material  103 . 
     When the solar battery module  101  having the structure shown in FIG. 3 generates AC power, the heat produced by the inverter  107  is transferred effectively to the back reinforcing material  103  because the thermal conductor  305  is interposed between the inverter  107  and the back reinforcing material  103 . The heat from the  107  therefore escapes efficiently so that the reliability of the inverter  107  is enhanced. 
     Third Embodiment 
     FIG. 4 is a perspective view of the solar battery module  10 , which has been worked into the shape of a roofing tile. Here the longitudinal side edges of the solar battery module  101  are bent to form upstanding portions  402 . 
     FIG. 5 is a diagram illustrating a method of installing the solar battery module  101  in the shape of a roofing tile. 
     As shown in FIG. 5, spacers  504  are placed at prescribed intervals on sarking  505 , and centering strips  503  are placed on respective ones of the spacers  504 . The solar battery module  101  is placed on step portions formed by the spacers  504  and centering strips  503 , and the solar battery module  101  is fixed by driving nails into the centering strips  502 . 
     By thus installing the solar battery module  101 , an air-flow passageway  506  is formed between the sarking  505  and solar battery module  101 . The air-flow passageway  506  is for utilizing air, which flows in from the direction of the ridge, upon warming the air by the heat produced by the inverter  107 . 
     Though not shown in FIG. 5, the necessary number of solar battery modules are installed by connecting the solar battery modules  101  in the direction of the ridge. 
     Thus, in the third embodiment, the air between the solar battery module  101  in the shape of a roofing tile and the sarking  505  can be warmed efficiently. This embodiment is effective in heat collection that relies upon a roof. 
     Fourth Embodiment 
     FIG. 6 is a diagram showing another structure of the solar battery module  101 . 
     Numeral  607  denotes a hybrid device obtained by integrating a solar battery element and an inverter. More specifically, an inverter circuit is incorporated beforehand in a solar battery element by using a thin-film inductor. A heat conducting member  608  is interposed between the inverter portion of the device  607  and the back reinforcing material  103 . 
     Thus, the inverter circuit is incorporated in the solar battery element. When the solar battery module  101  is transported or installed, therefore, the inverter  107  will not strike building structures and it is possible to prevent damage to the inverter  107  and a decline in the reliability thereof in a manner similar to that of the solar battery module  101  shown in FIG.  1 . 
     Further, when the solar battery module  101  generates power and the inverter circuit operates, heat evolved by the inverter circuit can be transferred effectively to the back reinforcing material  103  of the solar battery module  101  via the heat conducting member  608  in a manner similar to that of the solar battery module  101  shown in FIG.  1 . As a result, the heat evolved by the inverter  107  escapes efficiently and the reliability of the inverter  107  can be improved. 
     The effects set forth below are obtained with the embodiments described above. It goes without saying that the same effects can be expected also in a case where a DC/DC converter is used instead of an inverter. 
     (1) The inverter is secured within the solar battery module. As a result, the inverter will not strike building structures and it is possible to prevent damage to the inverter and a decline in the reliability thereof. 
     (2) Heat evolved by the inverter is transferred effectively to the back insulating material of the solar battery module. As a result, the heat evolved by the inverter escapes efficiently and the reliability of the inverter can be improved. 
     (3) In a case where an amorphous silicon solar battery is used as the solar battery element, the temperature of the back reinforcing material rises owing to heat produced by the inverter. As a result, an improvement in conversion efficiency owing to the annealing effect can be expected. 
     (4) In a case where a solar battery module in the shape of a roofing tile is utilized in a heat collecting roof, air between the solar battery module and sarking can be warmed efficiency by heat that is transferred effectively from the inverter to the back reinforcing material. 
     As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.