Solar concentrator

Abstract

A collector includes a convergent lens ( 2 ) having a focal distance f and an image focal plane (PFI). The convergent lens ( 2 ) defines one of the walls of a casing ( 1 ) defined by two pairs of side walls ( 4 a, 4 c ), a bottom wall ( 3 ) and a front wall defined by the lens ( 2 ), the side and bottom walls on the inside of the casing being reflective, and the depth p of the casing being lower than the focal distance f of the lens so that after multiple reflections, the ray beam (R 1 , R 2 ) thus reflected is concentrated on a final image focus (I′) located inside the casing, the collector including a mobile receptor ( 6 a ) held inside the concentrated beam or in a position at least intersecting the beam by elements controlling the movement of the collector ( 6 a ) with that of the beam.

1 - 18 . (canceled) 
     
     
         19 . A solar concentrator of the type comprising, as collector, a convergent lens having a focal distance and an image focal plane, on which are concentrated, along a line, called “primary image focus”, the beam of the solar rays that said lens receives, said concentrated beam moving with the trajectory of the sun, wherein said convergent lens forms one of the walls of a chamber defined by:
 two pairs of side walls, a bottom wall and a front wall formed by said lens, the side walls of each pair being parallel to each other, and each pair of side walls being perpendicular to the other pair,   the side and bottom walls, inside the chamber, being reflective,   the depth between the front wall and the bottom wall being less than the focal distance of the lens,   such that, after multiple reflections, the duly reflected beam of rays is concentrated on a line called “final image focus” symmetrical to said primary image focus relative to said bottom wall and belonging to a “near image focal plane” itself symmetrical to said image focal plane relative to said bottom wall, but located inside said chamber,   said concentrator enclosing a mobile receiver maintained within said concentrated beam, or in a position at least secant to said beam, by means servo-controlling the movement of said receiver to the movement of said beam.   
     
     
         20 . The concentrator as claimed in  claim 19 , wherein said chamber is rectangular parallelepiped and wherein the depth p of the chamber, for this purpose, satisfies the relation
     p= 0.5*( f+e+b )   
       where:
 e is the penetration thickness of the lens in the chamber, and 
 b is the distance between the lens and the near image focal plane or useful operating distance. 
 
     
     
         21 . The solar concentrator as claimed in  claim 19 , wherein the center of said receiver is located within an area that affects an extent ranging from +k to −k either side of said near image focal plane, median to said area, k satisfying the relation: 
       
         
           
             
               k 
               = 
               
                 r 
                 
                   sin 
                    
                   
                     [ 
                     
                       A 
                        
                       
                           
                       
                        
                       
                         tan 
                          
                         
                           ( 
                           
                             d 
                             f 
                           
                           ) 
                         
                       
                     
                     ] 
                   
                 
               
             
           
         
       
       where:
 r is the radius of the transverse section of the receiver if this section is circular or of the circle inscribed in the section of the receiver if this section is not circular, given that the expression “center of the receiver” is understood to mean the straight line parallel to the final image focus and which passes through the center of said circle; 
 sin[A tan] stands for sinus[arc tangent]; 
 d is the distance between the optical axis of the lens and the edge of the lens, taken in the plane containing said optical axis and which is perpendicular to the bottom of the chamber and orthogonal to the final image focus. 
 
     
     
         22 . The concentrator as claimed in  claim 19 , wherein said convergent lens is flat-convex, biconvex or convergent meniscus. 
     
     
         23 . The concentrator as claimed in  claim 19 , wherein said convergent lens is a Fresnel lens. 
     
     
         24 . The concentrator as claimed in  claim 19 , wherein said convergent lens is a flat-convex Fresnel lens fitted so that its flat face faces the outside of said chamber. 
     
     
         25 . The concentrator as claimed in  claim 19 , wherein said convergent lens is a biconvex Fresnel lens, fitted so that its convex smooth face faces the outside of said chamber. 
     
     
         26 . The concentrator as claimed in  claim 19 , wherein said receiver is a heat pipe covered with a material, the heat absorption coefficient of which is greater than the heat emission coefficient. 
     
     
         27 . The concentrator as claimed in  claim 19 , wherein said receiver is a heat pipe covered with a material, the heat absorption coefficient of which is greater than the heat emission coefficient, said heat pipe taking the form of a pipe included in a pipe under vacuum. 
     
     
         28 . The concentrator as claimed in  claim 19 , wherein said receiver is a heat pipe covered with a material, the heat absorption coefficient of which is greater than the heat emission coefficient, said receiver being connected to an extraction exchanger fed with a heat-carrying fluid. 
     
     
         29 . The concentrator as claimed in  claim 19 , wherein the receiver is a photovoltaic cell receiver. 
     
     
         30 . The concentrator as claimed in  claim 19 , wherein said receiver is an extraction exchanger fed with heat-carrying fluid. 
     
     
         31 . The concentrator as claimed in  claim 19 , wherein said receiver can occupy two positions, namely a service position in which it receives a certain thermal energy and a retracted position in which It receives a lesser thermal energy than in the service position. 
     
     
         32 . The concentrator as claimed in  claim 19 , wherein the receiver is connected to a Stirling engine. 
     
     
         33 . The concentrator as claimed in  claim 19 , wherein the surfaces of the lens and/or the reflective walls of the chamber are treated to reduce the potential degradation of their material over time. 
     
     
         34 . The concentrator as claimed in  claim 19 , wherein the outer surface of the lens includes an anti-glare treatment. 
     
     
         35 . The concentrator as claimed in  claim 19 , wherein the reflective walls are made of removable reflective panels. 
     
     
         36 . The concentrator as claimed in  claim 19 , wherein, to control the speed and the direction of movement of the receiver, the latter is provided with a photon flux meter adapted to send signals to driving means to which said receiver is subjected. 
     
     
         37 . The solar concentrator as claimed in  claim 20 , wherein the center of said receiver is located within an area that affects an extent ranging from +k to −k either side of said near image focal plane, median to said area, k satisfying the relation: 
       
         
           
             
               k 
               = 
               
                 r 
                 
                   sin 
                    
                   
                     [ 
                     
                       A 
                        
                       
                           
                       
                        
                       
                         tan 
                          
                         
                           ( 
                           
                             d 
                             f 
                           
                           ) 
                         
                       
                     
                     ] 
                   
                 
               
             
           
         
       
       where:
 r is the radius of the transverse section of the receiver if this section is circular or of the circle inscribed in the section of the receiver if this section is not circular, given that the expression “center of the receiver” is understood to mean the straight line parallel to the final image focus and which passes through the center of said circle; 
 sin[A tan] stands for sinus[arc tangent]; 
 d is the distance between the optical axis of the lens and the edge of the lens, taken in the plane containing said optical axis and which is perpendicular to the bottom of the chamber and orthogonal to the final image focus.