Optimization of ground coverage of terrestrial solar array system

Abstract

A concentrator photovoltaic solar cell array for terrestrial use for generating electrical power from solar radiation including a central support which is rotatable about its central longitudinal axis, a support frame carried by, and rotatable with respect to, the central support about an axis orthogonal to said central longitudinal axis, and a solar array mounted on the support frame. The solar cell array includes a plurality of Fresnel concentrator lenses and multijunction III-V compound semiconductor solar cells each producing in excess of 10 watts of DC power. An actuator is provided for rotating the central support and the support frame so that the solar cell array is maintained substantially orthogonal to the rays of the sun as the sun traverses the sky.

1 - 12 . (canceled) 
     
     
         13 . A concentrator photovoltaic solar cell array system for producing energy from the sun using a plurality of sun-tracking solar cell arrays, each array comprising:
 a central support mounted on the ground, and a second member extending from the ground mountable first member and being capable of rotation relative to the stationary first member about its central longitudinal axis;   a support frame carried by a second, opposing end of the second member, the support frame being rotatable with respect to the central support about an axis orthogonal to said central longitudinal axis;   a generally rectangular planar solar cell array of greater than 1500 solar cell receivers for producing in excess of 18 kW peak DC power on full illumination, each receiver including a triple junction III-V semiconductor compound concentrator solar cell each capable of producing in excess of ten watts of power; and   an actuator for rotating the central support and the support frame so that the solar cell array is maintained substantially orthogonal to the rays from the sun as the sun traverses the sky.   
     
     
         14 . As system as claimed in  claim 13  wherein the generally rectangular planar solar cell array further comprises an aspect ratio between 1:2 and 1:5. 
     
     
         15 . A system as claimed in  claim 13 , wherein the solar cell array comprises a plurality of solar cell modules, each module including a single Fresnel lens disposed over a single solar cell for concentrating by a factor in excess of 500X the incoming sunlight onto the solar cell and producing in excess of 10 watts of DC power at AM 1.5 solar irradiation with conversion efficiency in excess of 37%, said module including a tapering support with the single Fresnel lens on one end and solar cell at the other end to focus light on the solar cell. 
     
     
         16 . A system as claimed in  claim 15 , wherein the solar cell array comprises a plurality of subarrays each subarray consisting of a portion of the plurality of solar modules arranged in a rectangular matrix with thirteen modules in a first matrix direction, and twenty six modules in a second matrix direction orthogonal to the first matrix direction. 
     
     
         17 . A system as claimed in  claim 16 , wherein the central support is constituted by a first member provided with means for mounting the central support on the ground, and the second member rotatably supported by, and extending upwardly from, the first member to support the support frame and solar array in a spaced apart relationship with the first member. 
     
     
         18 . A system as claimed in  claim 17 , wherein the support frame is mounted on a cross member which is rotatably mounted with respect to the second member of the central support about an axis orthogonal to said central longitudinal axis. 
     
     
         19 . A system as claimed in  claim 18 , wherein the support frame is constituted by a generally rectangular frame member which is provided with a plurality of parallel support struts which are parallel to the shorter sides of the rectangular frame member for supporting a plurality of subarrays. 
     
     
         20 . A system as claimed in  claim 19 , further comprising a plurality of support arms, each of which extends between a respect one of said support struts and said second member. 
     
     
         21 . A concentrator photovoltaic solar cell array system for producing energy from the sun using a plurality of sun-tracking solar cell arrays, comprising:
 a plurality of central supports mounted on the ground in a lattice pattern;   each central support having a support frame rotatable with respect to the central support about an axis orthogonal to a central longitudinal axis of the central support;   a rectangular solar cell array of greater than 1500 solar cell receivers having a predetermined aspect ratio, with the longitudinal of the array parallel to the ground for producing in excess of 18 kW peak DC power on full illumination, the array including a plurality of triple junction III-V semiconductor compound solar cell receivers each capable of producing in excess of ten watts of peak DC power mounted on the support frame; and   an actuator for rotating the central support and the support frame so that the solar cell array is maintained substantially orthogonal to the rays from the sun as the sun traverses the sky and wherein the lattice pattern for the plurality of arrays includes a spacing between each of the plurality of central supports based upon the predetermined aspect ratio so that each of the arrays is fully illuminated for all positions wherein the sun is fifteen or more degrees above the horizon and there is no shadowing of any given array by any other array   
     
     
         22 . A system as claimed in  claim 21  wherein the predetermined aspect ratio further comprises a value between 1:2 and 1:5. 
     
     
         23 . A system as claimed in  claim 21 , wherein the solar cell array comprises ten subarrays, each with thirteen solar cell modules connected together in series or parallel, each module including a single nine inch by nine inch Fresnel lens disposed over a single solar cell receiver and supported by a tapering support for concentrating by a factor in excess of 500X the incoming sunlight onto the solar cell and producing in excess of 10 watts of DC power at AM 1.5 solar irradiation with conversion efficiency in excess of 37%, wherein the tapered support focuses light on the solar cell. 
     
     
         24 . A system as claimed in  claim 23 , wherein the solar cell receiver comprises (i) a solar cell consists of a germanium bottom cell, a gallium arsenide middle cell, and an indium gallium phosphide top cell; (ii) an insulated bypass diode connected in parallel with the solar cell; and (iii) an electrical connector with an electrical cable for allowing the receivers to be electrically connected to each other in an electrical circuit. 
     
     
         25 . A concentrator photovoltaic solar cell array system for producing energy from the sun using a plurality of sun-tracking solar cell arrays, each array comprising:
 a plurality of central supports wherein each of the plurality of central supports further comprises:   a support frame rotatable, with respect to, the central supports about an axis orthogonal to a central longitudinal axis of the central supports;   a rectangular solar cell array of greater than 1500 solar cell receivers having a predetermined aspect ratio, the array including a plurality of triple junction III-V semiconductor compound solar cells each cell, each capable of producing in excess of 10 watts of peak DC power and including a triple junction solar cell for terrestrial applications comprising:   a germanium substrate including a first photoactive junction;   a gallium arsenide middle cell disposed on said substrate;   an indium gallium phosphide top cell disposed over said middle cell and having a bandgap to maximize absorption in the AM1.5 spectral region;   a surface grid for conduction of the relatively high current created by the cell;   an actuator for rotating the central support and the support so that the solar cell array is maintained substantially orthogonal to the rays from the sun as the sun traverses the sky; and   a spacing between each of the central supports based upon the predetermined aspect ratio that optimizes the amount of solar cells in a given ground area.   
     
     
         26 . A system as claimed in  claim 25 , wherein the predetermined aspect ratio further comprises a value between 1:2 to 1:5. 
     
     
         27 . A system as claimed in  claim 25 , wherein the solar cell array comprises a plurality of solar cell modules, each module including a single Fresnel lens disposed over a single solar cell for concentrating by a factor in excess of 500X the incoming sunlight onto the solar cell and producing in excess of 10 watts of DC power at AM 1.5 solar irradiation with conversion efficiency in excess of 37% with a tapered support with the Fresnel lens at one end and the solar cell at the other end and wherein the tapered support focuses light on the solar cell. 
     
     
         28 . A system as claimed in  claim 21  wherein the solar cell receivers further comprising a first electrical contact on a light absorbing side of the solar cell and a second contact on an opposing, back side of the solar cell. 
     
     
         29 . A system as claimed in  claim 21  wherein the solar cell receivers further comprising a dense grid pattern with 4-fold symmetry connected to the first electrical contact on a light-absorbing side of the receivers. 
     
     
         30 . A system as claimed in  claim 21  wherein the solar cell receivers wherein the triple junction solar cell receiver further comprises a top bandgap of 1.0 eV, a middle bandgap of 1.4 eV and a bottom band gap of 0.7 eV. 
     
     
         31 . A system as claimed in  claim 27  wherein the Fresnel lens and module further comprises a 520X concentration with an f#of 2. 
     
     
         32 . A system as claimed in  claim 27  wherein the solar cell array further comprising ten solar cell subarrays where each subarray has thirteen solar cell modules and each module has a 2×7 matrix of solar cells.