Central receiver solar collector using mechanically linked mirrors

Abstract

A solar collector having a central radiation receiver and a field of mirrors which are mechanically linked to track the sun and reflect solar radiation onto the radiation receiver. A rigid mechanical controlling element is carried by a plurality of parallel arms which are continuously aligned in the direction of the sun. Each mirror is coupled at normal incidence to a linear guide member which engages one of a plurality of positional guides mounted on the rigid controlling element to keep the mirrors in proper alignment.

I claim: 
     
       1. A solar radiation collector utilizing mechanically linked mirrors to provide radiation concentration, comprising: (a) a radiation receiver,   (b) a first rigid structure substantially greater in dimensional extent in at least one dimension than the .[.dimentions.]. .Iadd.dimensions .Iaddend.of the radiation receiver, the first rigid structure being generally fixed with respect to the radiation receiver at a position displaced from the radiation receiver along a line normal to the directions of major dimensional extent of the first rigid structure,   (c) a first plurality of articulated joints carried by the first rigid structure, the joints allowing free rotation in any direction within a substantial range of angular positions,   (d) a plurality of mirrors, each mirror being coupled to and rotatable about an individual joint of the first plurality of articulated joints so that, when properly oriented, each of the mirrors may reflect radiation from a radiation source onto the radiation receiver,   (e) a second rigid structure which is translatably movable in three mutually perpendicular directions with respect to the first rigid structure, with the motion being constrained so that each point on the second rigid structure generally moves over a spherical surface particular to that point,   (f) a plurality of positional guides carried by the second rigid structure, each individual positional guide being paired with an individual joint of the first plurality of articulated joints .[.in that each positional guide is disposed with respect to the second rigid structure in such a way that the particular spherical surface to which a positional guide is constrained contains an articulated joint of the first plurality of joints, with the articulated joint positioned at the intersection with the spherical surface of a straight line which passes through the position of the radiation receiver and the center of the particular sphere of constraint.].,   (g) a plurality of linear guide members, each coupled to an individual articulated joint of the first plurality of joints and extending to the positional guide associated with that particular joint, with the positional guide slidably engaging the linear guide member and with each linear guide member adapted to orient the individual mirror associated with that particular joint to a position normal to the linear guide member, and   (h) means for moving the second rigid structure, in response to changes in the angular position of the sun, so that each positional guide lies along a line which passes through the center of the particular sphere of constraint for that positional guide and is aligned .Iadd.generally .Iaddend.in the direction of the sun.   
     
     
       2. The radiation collector of claim 1, wherein: (a) the first plurality of articulated joints is distributed over a segment of a first generally smooth surface of revolution which is fixed with respect to the first rigid structure, with the axis of revolution being a line passing through the radiation receiver, and   (b) the plurality of positional guides is distributed over a segment of a second generally smooth surface of revolution which is fixed with respect to the second rigid structure, with the axis of revolution being parallel to the axis of revolution for the first surface of revolution and further being coincident with the axis of revolution for the first surface of revolution when the second rigid structure is in a position appropriate for focusing radiation from a source lying along the axes of revolution, and with the further detailed relationship between the surfaces of revolution being as recited in the specification.   
     
     
       3. The radiation collector of claim 2, wherein the second surface of revolution is a plane surface. 
     
     
       4. The radiation collector of claim 2, wherein the first surface of revolution is a plane surface. 
     
     
       5. The radiation collector of claim 1, further comprising: (a) a second plurality of articulated joints carried by the first rigid structure, with each joint providing a first pivotal motion about a common first axis direction and a second pivotal motion about a second axis direction which is orthogonal to the first axis direction and which is rotatable about the first axis direction,   (b) a third plurality of articulated joints, carried by the second rigid structure, with each joint of the third plurality of joints being paired with a corresponding joint in the second plurality of joints, and with the spatial relationship among the third plurality of joints being identical to the spatial relationship among the second plurality of joints, and   (c) a plurality of equal length parallel arms, each arm articulatably linking an articulated joint of the second plurality of joints with the corresponding joint of the third plurality of joints.   
     
     
       6. The radiation collector of claim 5, wherein the means for moving the second rigid structure comprises a first rotary actuator acting about the first axis direction and a second rotary actuator acting about the second axis direction on at least one articulated joint of the second plurality of joints, with the first and second rotary actuators controlled by sun sensing means fixed to one of the parallel arms so that the parallel arms are kept continually aligned parallel to the direction of incoming sunlight. 
     
     
       7. The radiation collector of claim 5, wherein at least two joints of the second plurality of joints are colinear along the common first axis direction. 
     
     
       8. The radiation collector of claim 7, further comprising at least one rotatable shaft rigidly linking at least two colinear joints of the second plurality of joints along their common first axis direction in such a manner that the second axis directions are rigidly held common for the colinear joints so linked. 
     
     
       9. The radiation collector of claim 6, wherein: (a) the first rigid structure is comprised of the local earth surface over which the collector is disposed,   (b) the second rigid structure is comprised of rigid steel members,   (c) the second rigid structure is constructed in sections, with individual sections linked by expansion joints adapted to transfer generally vertical forces between sections while limiting the displacement due to thermal expansion within the second rigid structure to the expansion associated with each individual section, and   (d) each individual section of the second rigid structure is provided individual motional means, with the motional means for each section moving that section in identical fashion to every other section, whereby the second rigid structure as a whole retains substantially greater dimensional stability under changing ambient temperature than would be possible for a non-sectioned steel structure.   
     
     
       10. The radiation collector of claim 5, wherein the common first axis direction of the second plurality of articulated joints is contained in a vertical plane oriented in the north-south direction. 
     
     
       11. The radiation collector of claim 1, further comprising a plurality of mounting posts, each having a first end fixed to the first rigid structure and a second end carrying an articulated joint of the first plurality of joints. 
     
     
       12. The radiation collector of claim 11, wherein the articulated joints of the first plurality of joints are ball and socket joints. 
     
     
       13. The radiation collector of claim 12, wherein the individual mounting posts comprise a straight portion and a bent portion, the bent portion being located in the region of the second end of each mounting post and being shaped in such a way that the center of rotation of the ball and socket joint carried by that post is in line with an extension of the straight portion of the post, while in the region of attachment of the ball and socket joint to the second end of the mounting post the bent portion of the post makes an angle of up to 35° with respect to an extension of the straight portion of the post. 
     
     
       14. The radiation collector of claim 1, wherein: (a) the first rigid structure comprises a plurality of linear elements arranged in a rectangular lattice, whereby there are a plurality of points of intersection between orthogonally disposed linear elements,   (b) each articulated joint of the first plurality of joints comprises: (1) a ball centered at a point of intersection between the orthogonal linear elements of the lattice, and   (2) a segmented socket having four narrow segments adapted for gripping the ball without interfering with the linear elements of the first rigid structure lattice,     (c) each mirror is segmented, with each individual segment carried by an individual segment of the socket portion of the particular ball and socket joint with which the mirror associated, and with the individual mirror segments separated sufficiently to provide clearance for the linear elements comprising the first rigid structure as the mirror is moved through a range of angular positions; and   (d) each positional guide of the plurality of positional guides comprises an angular coupling adapted to maintain the associated linear guide member in a defined rotational position about an axis coincident with the linear guide member, with each positional guide having a fixed pivot axis parallel to one of the orthogonal directions of orientation of the linear elements comprising the first rigid structure.   
     
     
       15. The radiation collector of claim 2, further comprising: (a) a first layer of thin durable material containing a first plurality of spaced small holes,   (b) a second layer of thin durable material containing a second plurality of spaced small holes, the second layer of material being spaced from the first layer of material, wherein: (1) the first rigid structure comprises a shaping framework which holds the first layer of material in the form of the first surface of revolution of claim 2,   (2) the second rigid structure comprises a shaping framework which holds the second layer of material in the form of the second surface of revolution of claim 2,   (3) the individual holes of the second plurality of holes in the second layer of material are paired with the individual holes of the first plurality of holes in the first layer of material, and the position of each individual hole in the second layer of material is spatially related to the position of an associated hole in the first layer of material according to the prescription recited in the specification for the spatial relationship between a positional guide and an associated articulated joint of the first plurality of joints,   (4) each linear member of the plurality of linear guide members is comprised of a pin having a thickened region along its length, the thickened region functionally dividing each pin into a generally shorter portion and a generally longer portion,   (5) the longer portion of each pin is inserted through an associated pair of holes in the first and second layers of thin durable material, with the thickened region of the pin serving as a stop to allow the pin to be supported by the uppermost layer of thin durable material, and   (6) the plurality of mirrors, each having a diameter generally comparable to the length of the shorter portion of a pin and generally less than the dimensions of the radiation receiver, are attached to the free ends of the shorter portion of the pins.     
     
     
       16. The radiation collector of claim 1, wherein the plurality of mirrors includes mirrors of differing size, with the mirrors in closest proximity to the radiation receiver being relatively larger in size and the mirrors at the greatest distance from the radiation receiver being relatively smaller in size. 
     
     
       17. The radiation collector of claim 1, further comprising a transparent covering disposed between the plurality of mirrors and the radiation receiver. 
     
     
       18. The radiation collector of claim 17, further comprising: (a) a large area radiation absorber disposed on the opposite side of mirrors from the radiation receiver, and   (b) means for transporting thermal energy from the large area radiation absorber to a use region.   
     
     
       19. The radiation collector of claim 18, wherein: (a) the second rigid structure comprises: (1) a peripheral frame,   (2) narrow structure sections, each slidably engaging the peripheral frame,     (b) each mirror of the plurality of mirrors is made reflective on both its front and back surfaces, and   (c) the collector further comprises means for varying the spacing of the individual structure sections comprising the second rigid structure between a first spacing, in which the positional guides are in suitable position to produce simultaneous focusing alignment of all the mirrors, and a second spacing, which allows all the mirrors to be tilted simultaneously to angles generally in excess of 60 degrees with respect to the plane of the collector. .Iadd.   
     
     
       20.  A concentrating solar radiation collector comprising: (a) a radiation receiver,   (b) a first generally rigid structure much larger in at least one dimension than any dimension of the radiation receiver,   (c) a first plurality of articulated joints carried by the first generally rigid structure,   (d) a plurality of linear guide members, each coupled to one of the articulated joints carried by the first generally rigid structure,   (e) a plurality of mirrors, each coupled perpendicularly to a linear guide member,   (f) a second generally rigid structure translatably movable in three mutually perpendicular directions with respect to the first generally rigid structure,   (g) a plurality of positional guides carried by the second generally rigid structure, each positional guide slidably engaging an individual linear guide member and thereby being associated with the particular articulated joint to which that guide member is coupled, with the position of each positional guide on the second generally rigid structure being established relative to the position of the associated articulated joint on the first generally rigid structure in a manner, dependent on the location of the positional guide and its associated articulated joint relative to the radiation receiver, such that parallel incoming radiation striking the plurality of mirrors may be simultaneously reflected from each of the mirrors to the radiation receiver; and   (h) means for so adjusting the relative positions of the first and second generally rigid structures that generally parallel solar radiation is reflected from each mirror onto the radiation receiver for a large range of angular positions of the sun. .Iaddend. .Iadd.21. A concentrating solar radiation collector comprising:   (a) a radiation receiver,   (b) a first generally rigid structure much larger in at least one dimension than any dimension of the radiation receiver,   (c) a second generally rigid structure,   (d) a plurality of interconnecting linkages of equal length, each extending between the first and second generally rigid structures and being articulatably connected to the respective structures in a manner allowing the orientations of the interconnecting linkages to be varied through a wide range of angular positions in parallel alignment with one another, with the variations in angular orientation of the interconnecting linkages accompanied by translational changes in the relative positions of the first and second generally rigid structures in three mutually perpendicular directions,   (e) a plurality of articulated joints carried by the first generally rigid structure,   (f) a plurality of linear guide members, each coupled to an articulated joint carried by the first generally rigid structure,   (g) a plurality of mirrors, each coupled perpendicularly to a linear guide member,   (h) a plurality of positional guides carried by the second generally rigid structure, each slidably engaging an individual linear guide member; with the position of each positional guide on the second generally rigid structure being established relative to the position on the first generally rigid structure of the particular articulated joint which is coupled to the linear guide member engaged by that positional guide in a manner, dependent on the location of the particular positional guide and articulated joint relative to the radiation receiver, such that parallel incoming radiation is reflected from each mirror onto the radiation receiver when the interconnecting linkages are directed generally parallel to the direction of the incoming radiation; and   (i) means for so adjusting the relative positions of the first and second generally rigid structures that generally parallel solar radiation is reflected from each mirror onto the radiation receiver for a large range   
     
     
        of angular positions of the sun. .Iaddend. .Iadd.22.  The radiation collector of claim 24, further comprising at least one rotatable shaft which engages at least two of the interconnecting linkages in a manner such that the linkages engaged by the shaft are constrained to a common plane which is rotatable with the shaft, with the engagement of the shaft to the linkages allowing pivotal motion of the engaged linkages within the common plane. .Iaddend.