Abstract:
An alternating current (AC, or ac) solar electric power generation system includes a primary concentrator to concentrate sunlight, one optional reflector to redirect the concentrated sunlight, a concentrating solar PV (CPV) module, a rotary electric connector, and a motor with an optional gearbox to spin the CPV module. The photovoltaic cells produce a varying electric output that is transmitted to the stationary contact by the rotary connector. Two groups of solar cells installed in the opposite direction with a phase difference of 180 degrees generate the one-phase AC electric power. An air and water mist, or other coolant system may cool the solar cells.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority of U.S. Provisional Application Ser. No. 61/094,117 titled “Low Numerical Aperture (Low-NA) Solar Lighting System” filed Sep. 4, 2008, which is hereby incorporated by reference. This application also claims the benefit of priority of U.S. Provisional Application Ser. No. 61/094,113 titled “One-axis tracking concentrating photovoltaic and solar hot water hybrid system” filed Sep. 4, 2008, which is hereby incorporated by reference. This application also claims the benefit of priority of U.S. Provisional Application Ser. No. 61/094,115 titled “Alternating current electricity generation from concentrated sunlight” filed Sep. 4, 2008, which is hereby incorporated by reference. This application also claims the benefit of priority of U.S. Provisional Application Ser. No. 61/094,120 titled “Solar lighting system with one-axis tracking” filed Sep. 4, 2008, which is hereby incorporated by reference. This application is related to co-pending U.S. patent application Ser. No. 12/584,052, titled “LOW NUMERICAL APERTURE (LOW-NA) SOLAR LIGHTING SYSTEM,” filed Aug. 27, 2009, and co-pending U.S. patent application Ser. No. 12/584,050, titled “CONCENTRATED PHOTOVOLTAIC AND SOLAR HEATING SYSTEM,” filed Aug. 27, 2009, both of which are incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of Invention 
     This invention relates to the field of solar photovoltaic systems, specifically to the generation of alternating electric power using concentrated sunlight. 
     2. Related Art 
     The use of the photovoltaic cells to generate electric power from solar radiation is a major part of the solar energy application. However, the solar photovoltaic cells generate Direct Current electric power. For many applications, the Direct Current electric power must be converted to Alternating Current before the electrical can be used. The DC-to-AC conversion needs an expensive power inverter, which makes up a significant portion of the total cost of the solar electric system. The inverter also consumes power and lowers the system efficiency. 
     SUMMARY OF THE INVENTION 
     Systems and method provide for a solar electric alternating current (AC, or ac) power generator. The system may include a primary sunlight concentrator to concentrate sunlight, a concentrating photovoltaic module, a rotary connector, and a motor with gearbox to spin the solar module against the concentrated sunlight. The primary sunlight concentrator may be a parabolic concentrator or a Fresnel lens. A secondary sunlight concentrator may direct sunlight to an optical homogenizer, which directs the concentrated sunlight to a solar AC generator. 
     Multiple solar cells rotate in tandem connected to a rotary connector with a stationary output post. The relative motion between the photovoltaic cells and the concentrated sunlight causes the solar irradiance on each solar cell to produce an electric current with varying amplitude and polarity. The total effect of the system is that the concentrated sunlight generates alternating current without an electric inverter. 
     The solar cells may be cooled to offset heat from the concentrated sunlight and generated current. The cooling method may include an evaporative mist near the top and bottom of the solar cells, or a temperature controlled bath. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Elements in the figures are illustrated for simplicity and clarity and are not drawn to scale. The dimensions of some of the elements may be exaggerated relative to other elements to help improve the understanding of various embodiments of the invention. 
         FIG. 1  shows an embodiment of the system for generating alternating current from concentrated sunlight. 
         FIG. 2  shows details of the solar AC generator. 
         FIG. 3  shows a representative motion of the solar AC generator. 
         FIG. 4  shows a representative electrical connection for the solar AC generator. 
         FIG. 5  shows another embodiment of the system for generating alternating current from concentrated sunlight. 
         FIG. 6  shows an embodiment of the system for generating alternating current from concentrated sunlight with a lateral motion stage. 
         FIG. 7  shows an embodiment of the system for generating alternating current from concentrated sunlight with an open rotary motion stage and a rotating reflector. 
         FIGS. 8   a ,  8   b ,  8   c ,  8   d  and  8   e  show an embodiment of the system for generating three-phase alternating current from concentrated sunlight. 
         FIG. 9  shows a flowchart of a method for generating alternating current electricity from a solar power generation system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an embodiment of the system for generating alternating current from a concentrated sunlight. The embodiment may comprise a primary sunlight concentrator  105 , a secondary sunlight concentrator  110 , concentrated sunlight  115 , an aperture  120 , a solar tracker  125 , a reflector  130 , a hinge  135 , an optical homogenizer  140 , and a rotary solar AC generator  145 . 
     The primary sunlight concentrator  105  concentrates the incoming sunlight by directing the incoming sunlight toward a common focal point. In some embodiments, a secondary sunlight concentrator  110  is at the common focal point to receive the incoming sunlight. Although the secondary light concentrator  110  does not collimate the light, the secondary light concentrator  110  keeps the concentrated sunlight convergent and directs it toward aperture  120 . The concentrated light  115  then exits the primary light concentrator  105  via aperture  120 . 
     Tracking the sunlight is a solar tracker  125 , which is connected to the primary light concentrator  105  to assure that the primary light concentrator  105  is optimally oriented at all times toward the sun. In one embodiment, the solar tracker  125  monitors both the azimuth and elevation of the sun with a dual axis motor system, continuously aligns the primary light concentrator  105  to directly face the sun. In some embodiments, the solar tracker  125  may be single axis system. Other embodiments may simply track the sun without aligning the primary light concentrator  105 , or omit the solar tracker  125 . 
     After passing through aperture  120 , the concentrated light  115  strikes the reflector  130 . The reflector  130  may comprise a high-power high-reflectivity mirror. The reflector  130  may be flat or other shape. The reflector  130  may be attached to the primary concentrator  105  and to a hinge  135 . The reflector  130  may be set near 45 degrees from the horizontal plane when the solar elevation angle is 0 degree. The reflector  130  may be set near 90 degrees from the horizontal plane, which is vertical, when the solar elevation angle is 90 degrees. The hinge  135  is connected to the sunlight homogenizer  140 . A filter may be present to remove infrared radiation and/or ultraviolet light. 
     The reflector  130  reflects the concentrated sunlight  115  into the sunlight homogenizer  140 . The optical homogenizer  140  may be a light tube. The optical homogenizer  140  may have an average reflectivity of over 98%. The optical homogenizer  140  may be fabricated with highly reflective aluminum sheet. The sunlight homogenizer  140  may be manufactured with different diameters, such as 2″, 3″, 5″, etc. The optical homogenizer  140  may be more sophisticated, but may be more expensive. On passing through the optical homogenizer  140 , the concentrated sunlight  115  enters the rotary solar AC generator  145 . 
       FIG. 2  shows details of the rotary solar AC generator  145 . The rotary solar AC generator  145  may comprise a rotary motion stage  200 , a plurality of concentrated photovoltaic cells  205 , a motor power supply  210 , a motor  215 , a gearbox  220 , a rotary electrical connector  225 , an alternating output connector  230 , and a concentrated photovoltaic cell cooling system  235 . 
     Beneath the optical homogenizer  140  is the rotary motion stage  200  supporting the concentrated photovoltaic cells  205 . The rotary motion stage  200  may be round or any shape configured for supporting the concentrated photovoltaic cells  205 . For example, if the concentrated photovoltaic cells  205  are square, the rotary motion stage  200  might be square to properly support the plurality concentrated photovoltaic cells  205 . 
     To take proper effect of the concentrated sunlight from the optical homogenizer  140 , each of the concentrated photovoltaic cells  205  may be approximately the same size as the outlet of the optical homogenizer  140 . The rotary motion stage  200  may be sized to hold the concentrated photovoltaic cells  205 . 
     Beneath the rotary motion stage  200  is the rotational driving mechanism of the rotary motion stage  200 . The rotational driving mechanism comprises a motor power supply  210 , a motor  215 , and a gearbox  220 . 
     The motor power supply  210  supplies power to the motor  215 . The motor power supply  210  may be a battery for an electrical motor. In some embodiments, the motor power supply  210  may be an alternative source, e.g., mechanical or electrical, for driving the motor  215 , thus creating ‘green (renewable) power’. 
     A gearbox  220  may be used to adapt the speed and torque of the motor  215  for rotating the rotary motion stage  200 . The rotary movement of the rotary motion stage  200  may be adjusted to match the desired frequency of the resultant alternating current, such as 60 cycles per second, 50 cycles per second, or whatever frequency is desired. 
     Electrically coupled to each of the concentrated photovoltaic cells  205  is the rotary electrical connector  225 . The rotary electrical connector  225  collects the current from the plurality concentrated photovoltaic cells  205  and transmits the current to the alternating output connector  230 . The rotary electrical connector  225  may be a MERCOTAC® brand low resistance rotary electrical connector. One end of the rotary electrical connector  225  may be fixed to the center of the rotary motion stage  200 . The rotating side connecting wires of the rotary electrical connector  225  are connected to the concentrated photovoltaic cells  205 . The stationary side connecting wires of the rotary electrical connector  225  are connected to the alternating output connector  230 . As the concentrated photovoltaic cells  205  rotate under the optical homogenizer  140 , they generate alternating current, as described herein. Some embodiments may include rectifiers to avoid back current to the concentrated photovoltaic cells  205 . 
     The concentrated photovoltaic cells  205  may heat-up from the solar heat of the concentrated sunlight  115  and from the generated current. The concentrated photovoltaic cell cooling system  235  near the top or bottom or both of the CPV cells  205  serves to cool the plurality concentrated photovoltaic cells  205 . In some embodiments, the concentrated photovoltaic cell cooling system  235  may be an evaporative air and water mist. In some embodiments, the concentrated photovoltaic cell cooling system  235  may be a nonconductive mist. In some embodiments, the concentrated photovoltaic cell cooling system  235  may be a temperature-controlled non-conductive liquid bath. 
       FIG. 3  shows a representative motion of the rotary solar AC generator  145 . In this embodiment, there are two concentrating photovoltaic cells  205 . In some embodiments, there may be a plurality of pairs of the plurality concentrating photovoltaic cells  205 . The concentrated photovoltaic cells  205  are high efficiency models. 
     In this representation, the rotary motion  200  is shown turning counter-clockwise. Turning the rotary motion stage  200  is the motor  215  and optionally, the gearbox  220  (shown in  FIG. 2 ). In some embodiments, the rotary motion stage  200  may be turning clockwise. The direction of rotation does not affect the output electric power. 
     The rotary electrical connector  225  collects the electrical power generated by the concentrating photovoltaic cells  205 , and transmits the power to the alternating output connector  230 . 
       FIG. 4  shows a representative electrical connection for the rotary solar AC generator  145 . In this representation, there are two concentrating photovoltaic cells  205  across from each other to show opposition of their electrical connection to the rotary electrical connector  225 . 
     As each of the at least two concentrating photovoltaic cells  205  rotates under the optical homogenizer  140  ( FIG. 3 ), it enters and exits the concentrated sunlight  115 . While subject to the concentrated sunlight  115 , the concentrating photovoltaic cell  205  generates direct current, i.e. in one polarity. As the opposing terminals of each of the concentrating photovoltaic cells  205  are connected to the same post, one of the concentrating photovoltaic cells  205  generates current of one polarity, while the other concentrating photovoltaic cell  205  generates current of opposing polarity. Furthermore, the amplitude of current generated is a function of the area of the each concentrating photovoltaic cell  205  under the optical homogenizer  140 . 
     Consequently, the concentrating photovoltaic cells  205  generate alternating current as the concentrated photovoltaic cells  205  rotate in the concentrated sunlight  115  under the optical homogenizer  140 . In some embodiments, there may be a plurality of pairs of the plurality concentrating photovoltaic cells  205  producing single-phase alternating current, two-phase alternating current, etc. 
       FIG. 5  shows another embodiment  500  of the system for generating alternating current from concentrated sunlight. Embodiment  500  may comprise the same elements as embodiment  100 , including the solar tracker  125 , except that a Fresnel lens  505  replaces the primary sunlight concentrator  105 . Similarly, the secondary sunlight concentrator  110 , the aperture  120 , the reflector  130 , the hinge  135 , and the optical homogenizer  140  are not needed. 
     The Fresnel lens  505  includes a substantially polygonal focusing portion adapted to focus the incoming sunlight directly onto the concentrating photovoltaic cells  205 . The function and operation of the embodiment  500  pertaining to the rotary solar AC generator  145  is as described above. The concentrated photovoltaic cell cooling system  235  may also be present. 
       FIG. 6  shows another embodiment  600  of the system for generating alternating current from concentrated sunlight. Embodiment  600  may comprise the primary sunlight concentrator  105 , the secondary sunlight concentrator  110 , the aperture  120 , the reflector  130 , the hinge  135 , and the optical homogenizer  140  as described in  FIG. 1 through 4 . Embodiment  600  may instead comprise the Fresnel lens  505  as with embodiment  500 . 
     In lieu of the rotary solar AC generator  145 , the embodiment  600  comprises a lateral motion stage  605 , two or more concentrated photovoltaic cells  205 ( a ) and  205 ( b ) respectively, a motor power supply  610 , a motor  615 , a gearbox  620 , and an alternating current collector and output connector  625 . 
     The lateral motion stage  605  supports the two concentrated photovoltaic cells  205 ( a ) and  205 ( b ). Attached to the lateral motion stage  605  is a lateral driving mechanism comprising a motor power supply  610 , a motor  615 , and a gearbox  620 . The motor power supply  610  supplies power to the motor  615 . The motor power supply  610  may be a battery for an electrical motor. In some embodiments, the motor power supply  610  may be an alternative energy source, e.g., mechanical or electrical, for driving the motor  615 , thus creating ‘green (renewable) power’. The gearbox  620  may be used to adapt the speed and torque of the motor  615  for lateral movement of the lateral motion stage  605 . 
     Each of the concentrated photovoltaic cells  205 ( a ) and  205 ( b ) is electrically connected to the alternating current collector and output connector  625 . As the lateral motion stage  605  moves back and forth, the area illuminated by the concentrated sunlight  115  on any one concentrated photovoltaic cell  205 ( a ) or  205 ( b ) increases as the lateral motion stage approaches the end of travel, and decreases as the lateral motion stage approaches the middle. As described herein, the amplitude of the current generated varies proportionally to the area of the concentrated photovoltaic cell  205 ( a ) or  205 ( b ) exposed to the concentrated sunlight  115 , while the net polarity is function of which of the concentrated photovoltaic cells  205 ( a ) or  205 ( b ) is receiving more of the concentrated sunlight  115 . At the middle, equal areas of the two concentrated photovoltaic cells  205 ( a ) and  205 ( b ) are illuminated. 
     As the lateral motion stage  605  moves the concentrated photovoltaic cells  205 ( a ) under the concentrated sunlight  115 , the alternating current collector and output connector  625  collects the direct current from the concentrated photovoltaic cells  205 ( a ) and outputs the varying current according to the polarity of its attachment to the alternating current collector and output connector  625 . As shown in  FIG. 6 , one lead of concentrated photovoltaic cells  205 ( a ) is the negative lead, and the other lead is the positive lead. The leads of concentrated photovoltaic cells  205 ( b ), however, are oppositely connected, so the direction of the current output by the alternating current collector and output connector  625  alternates according to which concentrated photovoltaic cells  205 ( a ) or  205 ( b ) is currently receiving concentrated sunlight  115 . 
     Consequently, as with the rotary solar AC generator  145 , the lateral solar AC generator also generates alternating current. Furthermore, the frequency of the lateral movement of the lateral motion stage  605  may be adjusted to match the desired frequency of the resultant alternating current, such as 60 cycles per second, 50 cycles per second, or whatever frequency is desired. 
     Some embodiments may include the concentrated photovoltaic cell cooling system  235 . 
       FIG. 7  shows an embodiment  700  of the system for generating alternating current from concentrated sunlight with an open rotary motion stage and a rotating reflector. The embodiment  700  may comprise the primary sunlight concentrator  105 , the secondary sunlight concentrator  110 , the aperture  120 , the solar tracker  125 , a rotating reflector  720 , the plurality of concentrated photovoltaic cells  205  and the alternating output connector  230 . The embodiment  700  may further comprise a power supply  705 , a motor  710  a gearbox  715 , a rotating reflector  720 , a stationary stage  725  and a stationary alternating current collector  730 . 
     As in the other embodiments, the primary sunlight concentrator  105  concentrates the incoming sunlight by directing the incoming sunlight toward a common focal point. In some embodiments, a secondary light concentrator  110  is at the common focal point to receive the incoming sunlight. Although the secondary light concentrator  110  does not collimate the light, the secondary light concentrator  110  keeps the concentrated sunlight convergent and directs it toward aperture  120 . The concentrated light  115  then exits the primary light concentrator  105  via aperture  120 . 
     Tracking the sunlight is a solar tracker  125 , which is connected to the primary light concentrator  105  to assure that the primary light concentrator  105  is optimally oriented at all times toward the sun. In one embodiment, the solar tracker  125  monitors both the azimuth and elevation of the sun with a dual axis motor system, continuously aligns the primary light concentrator  105  to directly face the sun. In some embodiments, the solar tracker  125  may be a single axis system. Other embodiments may simply track the sun without aligning the primary light concentrator  105 , or omit the solar tracker  125 . 
     After passing through the aperture  120 , the concentrated light  115  strikes the rotating reflector  720 . The rotating reflector  720  may comprise a high-power high-reflectivity mirror. The rotating reflector  720  may be flat or other shape. Attached to the rotating reflector  720  is the gearbox  715 , which is driven by the motor  710 , which is powered by the power supply  705 . The motor power supply  705  may be a battery for an electrical motor. In some embodiments, the motor power supply  705  may be an alternative energy source, e.g., mechanical or electrical, for driving the motor  615 , thus creating ‘green (renewable) power’. The motor  710  and gearbox  715  are connected to the solar tracker  125  so that the rotating reflector  720  directs the concentrated sunlight  115  onto the plurality of concentrated photovoltaic cells  205  in a rotating sequential motion around the stationary stage  725 . 
     As the concentrated sunlight  115  strikes each of the plurality of concentrated photovoltaic cells  205  in sequence, each concentrated photovoltaic cell  205  generates direct current according to its polarity in an amplitude proportional to the area of the concentrated photovoltaic cell illuminated. The stationary alternating current collector  730  collects and outputs this current. As the concentrated sunlight  115  rotates around the stationary stage  725 , each concentrated photovoltaic cell generates direct current in an amplitude proportional to the area of the concentrated photovoltaic cell illuminated. As each adjacent concentrated photovoltaic cells  205  is inversely connected to the stationary alternating current collector  730 , the resulting output is alternating current. 
     Although this embodiment lacks the optical homogenizer of some other embodiments, the solar energy concentration of the concentrated sunlight is about 500 suns. At this concentration, the electrical energy produced by the ambient (unconcentrated) sunlight is comparatively negligible. 
       FIGS. 8   a ,  8   b ,  8   c ,  8   d  and  8   e  show an embodiment of the system for generating three-phase alternating current from concentrated sunlight. The system for generating three-phase alternating current from concentrated sunlight operates in a manner similar to the one-phase alternating current embodiment, but may comprise a rotary table  800  for a plurality of six concentrated photovoltaic cells  205  ( 205 ( a ),  205 ( b ),  205 ( c ),  205 ( d ),  205 ( e ), and  205 ( f )), a three-phase rotary electrical connector  805 , and three pair of output connectors  810 . Some embodiments may include the concentrated photovoltaic cell cooling system  235 . 
     As shown in  FIG. 8   a , the system for generating three-phase alternating current from concentrated sunlight differs from the one-phase system in that there are three pairs of leads to the three-phase rotary electrical connector  805 . Similarly, although each of the six concentrated photovoltaic cells  205 ( a ),  205 ( b ),  205 ( c ),  205 ( d ),  205 ( e ), and  205 ( f ) have a positive output, the reversal of the terminal connections for concentrated photovoltaic cells  205 ( d ),  205 ( e ), and  205 ( f ) results in a reversal of the current direction, i.e., a negative output from those concentrated photovoltaic cells. 
     Concentrated photovoltaic cells  205 ( b ) and  205 ( e ) comprise phase  1 , but are connected in opposing output polarity to the same terminals. Concentrated photovoltaic cells  205 ( a ) and  205 ( d ) comprise phase  2 , but are connected in opposing output polarity to the same terminals. Concentrated photovoltaic cells  205 ( t ) and  205 ( c ) comprise phase  3 , but are connected in opposing output polarity to the same terminals. 
     As shown in  FIG. 8   b , the concentrated sunlight is striking approximately of one-half of each of the concentrated photovoltaic cells  205 ( a ) and  205 ( f ). Consequently, as the rotary table  800  rotates, the concentrated sunlight  115  strikes a 120-degree arc on the rotary table  800  and the six concentrated photovoltaic cells  205 ( a ),  205 ( b ),  205 ( c ),  205 ( d ),  205 ( e ), and  205 ( f ). 
     As shown, concentrated photovoltaic cell  205 ( a ) is outputting a net positive one-half full amplitude to the phase  2  lead, while concentrated photovoltaic cell  205 ( f ) is outputting a net negative one-half full amplitude to the phase  3  lead at the three pair of output connectors  810 . Concentrated photovoltaic cells  205 ( b ) through ( e ) are at relatively near zero voltage and are thus negligible outputs. 
     As shown in  FIG. 8   c , the rotating stage has brought the concentrated sunlight  115  to concentrated photovoltaic cells  205 ( f ) (about one-quarter amplitude),  205 ( a ) (approximately full amplitude) and  208 ( b ) (about one-quarter amplitude). Consequently, concentrated photovoltaic cells  205 ( a ) is at a net positive full amplitude to the phase  2  lead, concentrated photovoltaic cells  205 ( b ) is at a net negative one-quarter full amplitude to the phase  1  lead, while concentrated photovoltaic cell  205 ( f ) is outputting a net negative one-quarter full amplitude to the phase  3  lead at the three pair of output connectors  810 . Concentrated photovoltaic cells  205 ( c ) through ( e ) are at relatively near zero voltage and are thus negligible outputs. 
     As shown in  FIG. 8   d , the rotating stage has brought the concentrated sunlight  115  to concentrated photovoltaic cells  205 ( a ) (about one-half amplitude) and  205 ( b ) (approximately one-half full amplitude). Concentrated photovoltaic cell  205 ( a ) is again outputting a net positive one-half full amplitude to the phase  2  lead, while concentrated photovoltaic cell  205 ( b ) is outputting a net negative one-half full amplitude to the phase  1  lead at the three pair of output connectors  810 . Concentrated photovoltaic cells  205 ( c ) through ( f ) are at relatively near zero voltage and are thus negligible outputs. 
       FIG. 8(   e ) shows the output of each solar cell and the resultant three-phase output as the concentrated sunshine  115  sequentially strikes the concentrated photovoltaic cells  205 ( a ),  205 ( b ),  205 ( c ),  205 ( d ),  205 ( e ), and  205 ( f ) as described above. 
     From zero degrees to 60 degrees, the concentrated photovoltaic cells  205 ( a ) and  205 ( b ) output positive current on phases  2  and  1  respectively, while the concentrated photovoltaic cell  205 ( f ) outputs a current on phase  3 . As the concentrated photovoltaic cell  205 ( f ) is inversely connected to phase  3 , however, the net current output on phase  3  is negative current. 
     From 60 degree to 120 degrees, the concentrated photovoltaic cells  205 ( a ),  205 ( b ) and  205 ( c ) output positive current on phases  2 ,  1  and  3  respectively. 
     From 120 degree to 180 degrees, the concentrated photovoltaic cells  205 ( b ) and  205 ( c ) output positive current on phases  1  and  3 , while the concentrated photovoltaic cell  205 ( d ) outputs a current on phase  2 . As the concentrated photovoltaic cell  205 ( d ) is inversely connected to phase  2 , however, the net current output on phase  2  is negative current. 
     From 180 degrees to 240 degrees, the concentrated photovoltaic cell  205 ( c ) outputs positive current on phase  3 , while the concentrated photovoltaic cells  205 ( d ) and ( 205 ( e ) output a current on phases  2  and  1 . As the concentrated photovoltaic cells  205 ( d ) and  205 ( e ) are inversely connected to phases  2  and  1  respectively, the net current outputs on phases  2  and  1  are negative. 
     From 240 degrees to 300 degrees, the concentrated photovoltaic cells  205 ( d ),  205 ( e ) and  205 ( f ) output current on phases  2 ,  1  and  3 . As these concentrated photovoltaic cells are inversely connected to their phases, however, the net current outputs are negative current. 
     From 300 degrees to 360 degrees, the concentrated photovoltaic cells  205 ( a ) outputs positive current on phase  2 , while the concentrated photovoltaic cells  205 ( e ) and  2059 ( f ) output negative current on phases  1  and  3 . As the concentrated photovoltaic cells  205 ( e ) and  205 ( f ) are inversely connected to phases  1  and  3  respectively, the net current outputs on phases  1  and  3  are negative. 
     Consequently, as the rotary table  800  rotates with the concentrated sunlight  115  striking a 120-degree arc, the system generates three-phase alternating current. 
       FIG. 9  shows a flowchart of a method for generating alternating current electricity from a solar power generation system. 
     At step  905 , sunlight is received and concentrated by a primary concentrator. 
     At step  910 , the concentrated sunlight is homogenized. 
     At step  920 , the homogenized sunlight is directed onto a plurality of concentrating photovoltaic cells. 
     At step  925 , the plurality of concentrating photovoltaic cells is moved through the concentrated sunlight in a periodic pattern. 
     At step  930 , direct current is generated from the plurality of concentrating photovoltaic cells. 
     At step  935 , the direct current is received from the plurality of concentrating photovoltaic cells in an oscillating amplitude and polarity. 
     At step  940 , the resulting alternating current is output. 
     The embodiments discussed here are illustrative of the present invention. Elements in the figures are illustrated for simplicity and clarity and are not drawn to scale. Some elements may be exaggerated to improve the understanding of various embodiments. The descriptions and illustrations, as well as the various modifications or adaptations of the methods and/or specific structures described are within the spirit and scope of the present invention. Hence, these descriptions and drawings should not be considered in a limiting sense, as it is understood that the present invention is in no way limited to only the embodiments illustrated.