Abstract:
A photovoltaic receiver comprising an elongated structure bearing a plurality of photovoltaic cells. Said structure carries a plurality of finned dissipators, mounted on which are said photovoltaic cells, and ventilating means, designed to convey a flow of cooling air towards said dissipators

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of European patent application Ser. No. 09425112.1, filed Mar. 20, 2009, which is herein incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to photovoltaic systems for the production of electrical energy. More precisely, the invention regards a photovoltaic receiver designed to receive the solar radiation reflected by one or more mirrors. 
         [0004]    2. Description of the Related Art 
         [0005]    In concentration solar systems a high intensity of the solar radiation is obtained on the photovoltaic elements of the receiver. The high concentration of the solar radiation is advantageous from the standpoint of the yield of the photovoltaic elements, but poses problems caused by the excessive heating of the latter. In fact, above a certain temperature, the efficiency of the photovoltaic elements deteriorates sensibly. It is consequently necessary to envisage a cooling system that will enable the photovoltaic elements to operate in the temperature range that corresponds to high efficiency. On the other hand, it is necessary for the cooling system to be efficient and present a low energy consumption. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to provide a receiver for a concentration photovoltaic system equipped with a cooling system that is simple and inexpensive and presents a low energy consumption. 
         [0007]    According to the present invention, the above object is achieved by a photovoltaic receiver having the characteristics forming the subject of claim  1 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present invention will now be described in detail with reference to the attached drawings, which are provided purely by way of non-limiting example, wherein: 
           [0009]      FIG. 1  is a perspective view of a concentration photovoltaic system that uses a receiver according to the present invention; 
           [0010]      FIG. 2  is a side view of the photovoltaic system of  FIG. 1 ; 
           [0011]      FIG. 3  is a perspective view of a module of the photovoltaic receiver according to the present invention; and 
           [0012]      FIG. 4  is a side view of the module of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    With reference to  FIGS. 1 and 2 , designated by  10  is a concentration photovoltaic system including a supporting structure  12  bearing a reflecting element  14  and a receiver  16 . The reflecting element  14  is preferably formed by a mirror with parabolic reflecting surface that concentrates the solar radiation reflected onto the receiver  16 . 
         [0014]    The receiver  16  according to the present invention has a structure elongated in a longitudinal direction  20 , formed by a plurality of modules  18  set alongside one another. The single modules  18  are set alongside and fixed to one another along respective front surfaces  28  ( FIG. 3 ) orthogonal to the direction  20  so as to form a self-bearing structure elongated in the longitudinal direction  20 . 
         [0015]    With reference to  FIGS. 3 and 4 , each module  18  comprises a casing  22  having two side walls  24  and a top wall  26 , preferably of arched shape. The casings  22  of the individual modules  18  are identical to one another. Each casing  22  is open on its front sides  28  and has an open bottom end  30 . Each casing  22  has a central section  32 , a top section  34 , and a bottom section  36 . Housed in the central section  32  is an axial-flow electric fan  38 . The top section  34  forms a suction chamber for intake of the flow of air, which communicates with the external environment by means of windows  40  formed in the side walls  24 . The windows  40  are preferably equipped with grilles with one-way valves  42 . The fan  38  in operation generates a flow of air directed from the top section  34  towards the bottom section  36 , or vice versa. In the example illustrated, said flow of air is directed orthogonally to the bottom opening  30  of the casing  22 , as indicated by the arrows  44  in  FIG. 4 . Alternatively, it could be convenient to reverse the directions of suction and delivery of the fan  38  with respect to what is illustrated in  FIG. 4 . In this case, the flow of cooling air would be sucked into the bottom section and sent towards the top section  34 . 
         [0016]    The casings  22  of the various modules are fixed to one another along the respective front surfaces  28 , for example by means of welding, gluing or the like. The top sections  34  and the bottom sections  36  of the adjacent modules are in direct communication with one another through the respective front openings. In this way, in the case where the fan of a module does not function, the flow of cooling air is supplied by the fans of the adjacent units. 
         [0017]    Each module  18  comprises a finned dissipator  46  made of material with high thermal conductivity, such as for example aluminium or the like. The finned dissipator  46  has a base wall  48  and a plurality of fins  50  orthogonal to the base wall  48 . The fins  50  are fixed to the bottom end of the casing  22 . Each dissipator  46  is open at its side ends so that on each side of the module  18  there are formed two openings  52  for discharge of the flow of air, each opening  52  being delimited by the walls  48 ,  50  of the dissipator  46  and by the bottom end of the respective side wall  24  of the casing  22 . Preferably, each opening  52  is associated to a respective protection fin  54 , which extends from the bottom end of the respective side wall  24  of the casing  22 . Protection fins  56  of this sort can be provided in positions corresponding to the suction windows  40 . The fins  54 ,  56  are inclined with respect to the side walls  24  according to a general roof-like configuration so as to protect the openings  40 ,  52  from the entry of rain. 
         [0018]    A plurality of photovoltaic cells  58  is fixed on the bottom face of the base wall  48  of the dissipator  46 . The photovoltaic cells  58  are connected electrically to one another, preferably in pairs in parallel with respect to one another, and these pairs are then connected in series. With the connection in series between the pairs of cells  58 , it is possible to prevent any electrical insulation between the photovoltaic cells  58  and the dissipator  56 . The fact of preventing electrical insulation between the cells  58  and the dissipator  46  enables an improvement in the efficiency of thermal dissipation. The photovoltaic cells  58  of each module  18  are connected in series to the cells of the adjacent modules. Alternatively, in certain cases it may be envisaged that the photovoltaic cells  58  of each module  18  are connected in parallel to one another. 
         [0019]    In operation, the electric fan  38  generates a flow of cooling air directed towards the finned dissipator  46 . The fan  38  takes the air from the top section  34 , which communicates with the external environment through the windows  40 . The flow of air laps the fins  50  of the dissipator and exits from the openings  52 . Alternatively, the flow of air is drawn in from the external environment through the openings  52 , laps the fins  50  of the dissipator  46 , and is expelled from the openings  42  of the top section  34 . The receiver according to the present invention can be equipped with a fan  38  for each module  18 . Alternatively, each fan  38  can serve two or more adjacent modules. 
         [0020]    The receiver according to the present invention enables an effective cooling of the photovoltaic cells to be obtained, preventing excessively high temperatures (which would lead to a loss of efficiency of the photovoltaic cells) from being reached even in conditions of high concentration of solar radiation. Air cooling with dissipators and fans enables a reduction in the consumption energy of the operation of cooling. The modular structure of the receiver is particularly advantageous from the constructional standpoint and enables convenient adaptation of the dimension in the longitudinal direction of the receiver to the respective reflecting element. 
         [0021]    The solution according to the present invention enables use of a small amount of energy for cooling the photovoltaic cells. The flows of cooling air have short paths and extend through a very permeable structure. Consequently, a modest amount of energy is sufficient to move large amounts of air. 
         [0022]    The cooling structure is very compact and has overall dimensions in plan view equal to the size of the photovoltaic cells. In this way, the effect of obscuration of the lenses due to the shadow projected on the mirrors by the cooling structure is minimized. 
         [0023]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.