Primary concentrator with adjusted etendue combined with secondaries associated to multiple receivers and with convection reduction

Abstract

The present invention relates to primary and secondary concentrators of solar radiation. New primary concentrators of adjusted etendue combined with secondary concentrators are presented, for single of multiple receivers, capable of attaining the maximum possible concentration. The present invention also refers to devices which reduce the thermal losses by convection of the receivers.

1 . An optical system with primary concentrator of the Fresnel type and adjacent secondary concentrator, being the secondary receiver set above the primary, and characterized by the primary concentrator containing a stepped flow-line which shape verifies the condition that it reflects a set of edge rays so as to make them tangent to the receiver and the other set of edge rays in the direction of the secondary concentrator, which shape verifies the condition that it, on its turn, reflects the edge rays it receives from the primary concentrator in directions tangent to the receiver, producing there, theoretically, a maximum concentration, and in which the secondary is truncated. 
     
     
         2 . The optical system of  claim 1 , characterized by the receiver having a face of convex shape and also a flat face, and in which the secondary concentrator touches this flat face only on one point and in which this flat face can be replaced with a concave one, resulting in a secondary which does not touch the receiver. 
     
     
         3 . The optical system of  claim 1 , characterized by some or all of the portions of the stepped flow-line optic which follow the flow lines being absent, leaving only those portions which cross the flow lines, that is, the heliostats, and in which the continuous portions that may exist (not stepped) of the primary concentrator are also divided into heliostats. 
     
     
         4 . The optical system of  claim 1 , characterized by the heliostats being able to rotate around themselves to follow the apparent daily motion of the sun. 
     
     
         5 . (canceled) 
     
     
         6 . The optical system of  claim 1 , characterized by the heliostats being placed on a wave shaped surface, with cylindrical geometry, corresponding, basically, to a curve that optically conserves etendue. 
     
     
         7 . The optical system of  claim 6 , characterized by the heliostats of the primary concentrator being flat or curved. 
     
     
         8 . The optical system of  claim 6 , characterized by the overall shape of the primary concentrator being flat. 
     
     
         9 . The optical system of  claim 8 , characterized by all the receivers being substantially at the same height and the angles measured from the vertical through one of the receivers being about 33±10° with the line which, starting at the receiver, crosses the point of the primary which marks the transition between one and two receivers (angle α T ), of 61±5° with the line that crosses the midpoint of the primary optic (angle α M ) and of 71±5° with the line that crosses the other point of transition from one to two receivers (angle α R ). 
     
     
         10 . The optical system of  claim 9 , characterized by the angles measured from the vertical which crosses one of the receivers being: 32.6° with the line that, starting at the receiver, crosses the point of the primary that marks the transition between one and two receivers, of 61.2° with the line that crosses the midpoint of the primary optic and of 71.2° with the line that crosses the other point of transition from one to two receivers. 
     
     
         11 . The optical system of  claim 6 , characterized by not having secondary concentrators next to the receivers. 
     
     
         12 . The optical system of  claim 1 , characterized by the receivers having a larger size than that they would have if dimensioned for maximum or ideal concentration. 
     
     
         13 . The optical system of  claim 1 , characterized by comprising transparent covers substantially perpendicular to the flow lines and mirrors (mirrored on both sides) which substantially follow the flow lines for convection reduction next to the receiver. 
     
     
         14 . The optical system of  claim 13 , characterized by comprising mirrors and/or transparent covers, shaped as broken lines which substantially follow the flow lines or are substantially perpendicular to them, respectively, and in which the covers may be simple or double. 
     
     
         15 . (canceled) 
     
     
         16 . An optical system characterized by combining by means of intersecting at least two optical systems chosen from:
 an optical system with primary concentrator of the Fresnel type and adjacent secondary concentrator, the secondary receiver set being above the primary, and characterized by the primary concentrator containing a stepped flow-line optic which shape verifies the condition that it reflects a set of edge rays so as to make them tangent to the receiver and the other set of edge rays in the direction of the secondary concentrator, which shape verifies the condition that it, on its turn, reflects the edge rays it receives from the primary concentrator in directions tangent to the receiver, producing there, theoretically, a maximum concentration, and in which the secondary is truncated, and further characterized by some or all of the portions of the stepped flow-line optic which follow the flow lines being absent, leaving only those portions which cross the flow lines, that is, the heliostats, and in which the continuous portions that may exist (not stepped) of the primary concentrator are also divided into heliostats; or   an optical system with primary concentrator of the Fresnel type and adjacent secondary concentrator, the secondary receiver set being above the primary, and characterized by the primary concentrator containing a stepped flow-line optic which shape verifies the condition that it reflects a set of edge rays so as to make them tangent to the receiver and the other set of edge rays in the direction of the secondary concentrator, which shape verifies the condition that it, on its turn, reflects the edge rays it receives from the primary concentrator in directions tangent to the receiver, producing there, theoretically, a maximum concentration, and in which the secondary is truncated, and further characterized by the heliostats being able to rotate around themselves to follow the apparent daily motion of the sun;   thus forming a concentrator with multiple receivers.   
     
     
         17 . The optical system of  claim 16 , characterized by the heliostats being placed on a wave shaped surface, with cylindrical geometry, corresponding, basically, to a curve that optically conserves etendue. 
     
     
         18 . The optical system of  claim 16 , characterized by the heliostats of the primary concentrator being flat or curved. 
     
     
         19 . The optical system of  claim 6 , characterized by the overall shape of the primary concentrator being flat. 
     
     
         20 . The optical system of  claim 16 , characterized by the receivers having a larger size than that they would have if dimensioned for maximum or ideal concentration. 
     
     
         21 . The optical system of  claim 16 , characterized by comprising transparent covers substantially perpendicular to the flow lines and mirrors (mirrored on both sides) which substantially follow the flow lines for convection reduction next to the receiver. 
     
     
         22 . A method of concentrating solar energy, said method comprising: concentrating solar energy using an optical system with primary concentrator of the Fresnel type and adjacent secondary concentrator, the secondary receiver set being above the primary, and characterized by the primary concentrator containing a stepped flow-line optic which shape verifies the condition that it reflects a set of edge rays so as to make them tangent to the receiver and the other set of edge rays in the direction of the secondary concentrator, which shape verifies the condition that it, on its turn, reflects the edge rays it receives from the primary concentrator in directions tangent to the receiver, producing there, theoretically, a maximum concentration, and in which the secondary is truncated.