1-axis and 2-axis solar trackers

Abstract

A one-axis sun position tracking device with its rotation axis parallel to the rotation axis of the Earth, rotates perpetually at a constant speed in the opposite direction of the Earth's rotation. This device comprises a shaft that is aligned to the Earth's polar axis, one or more crossbars are rigidly attached to and perpendicular to the shaft, solar energy collectors are mounted on the crossbar and could rotate around the crossbar that defines declination angle. A self-latched declination angle adjustment mechanism keeps the declination angle constant at most of time. A drive mechanism keeps this solar tracker to rotate perpetually. An automatic and abrupt declination angle change will keep the declination angle updated to correct value each day. A similarly configured two-axis tracker that continuously updates its declination angle by a mechanism derived from a differential coaxial rotation. Two independent driving mechanisms control the speed and/or duration of the two coaxial rotations, and are programmed to eliminate all tracking errors from various sources.

1 . A 1-axis solar tracking device consists:
 a rotating shaft with one or multiple crossbars perpendicularly attached to it,   this shaft is mounted along the celestial rotation axis of the Earth, rotates continuously and perpetually at constant speed of one turn per day, in the opposite direction of the Earth's rotation   solar energy collectors mounted on the crossbar and can rotate around this crossbar for at least ±23½°, this rotation defines declination angle,   a self-latch mechanism keeps the declination angle constant most of the day,   an automatic and non-continuous declination angle update mechanism.   
     
     
         2 . The 1-axis solar tracking device of  claim 1 , the mechanism that determines the declination angle of the solar energy collectors consists:
 a gear, which is mounted on a beam that is rigidly attached to the main rotating shaft,   a rod with one end pivot connected to this gear and the other end pivot connected the solar energy collector,   a steady rotation of the gear translates into an approximate sinusoidal oscillation of the declination angle of the solar energy collector through the mechanic linking rod,   the amplitude of the oscillation of the declination angle is 23½°.   
     
     
         3 . The 1-axis solar tracking device of  claim 1 , the self-latch mechanism that keeps the declination angle constant consists:
 a spring loaded ball pushes against the notch between two adjacent teeth of a gear, prevents the gear from rotating freely,   the strength of the spring and the gear tooth slope determine the workload of this latch,   an additional worm gear stage provides a unidirectional and stronger latch of the declination angle,   
     
     
         4 . The 1-axis solar tracking device of  claim 1 , the automatic and non-continuous declination angle update mechanism consists:
 an open worm tooth which is spiral shaped, its cross section matches that of the worm gear,   the open worm tooth which is fixedly mounted on the ground, sits roughly in a plane that is perpendicular to the main rotating shaft,   the distance between one end of the open worm tooth to the center of the main rotating shaft is different from the distance between the other end of the open worm tooth to the center of the main rotating shaft, the difference is one tooth pitch of the worm gear,   during most time of a day, the open worm tooth does not engage with anything; at a pre-determined time of the day, the open worm tooth engages with the worm gear, and forces the worm gear to turn one notch during the engagement.   
     
     
         5 . The 1-axis solar tracking device of  claim 1 , once the initial declination angle is set correctly, and the gear ratio is set close enough to 365.242199, perpetual rotation of the main rotating shaft will provide a very good solar tracking. However, if the gear ratio is set slightly different from the ideal number 365.242199, periodical manual adjustments is needed to reset the accumulated error in declination angle. For example, if the gear ratio is set to 365, then only one manual declination angle adjustment every four years is needed, which is simply to manually turn the self latched gear by one notch once every four years; similarly, if the gear ratio is set to 366 or 364, then 3 or 5 manual adjustments every four years are needed, so on and so forth. 
     
     
         6 . The 1-axis solar tracking device of  claim 1 , to correct the error due to non-uniform day length, that is because each day is not exact 24 hour, the main rotating shaft may be programmed to rotate a little faster or slower from day to day to counter such variance, or only to rotate a little faster or slower during a portion of night time is enough to compensate the day length variance problem. 
     
     
         7 . A variance of the 1-axis solar tracking device of  claim 1 , if a ratchet is incorporated in the declination angle adjustment mechanism, the main rotating shaft could have an option to rotate back and forth while the declination angle is still updated as if the main rotating shaft was rotate perpetually, with all the benefit of its declination angle fixed during each day, and abruptly updates its declination angle daily and automatically. 
     
     
         8 . A 2-axis solar tracking device consists:
 a rotating shaft with one or multiple crossbars perpendicular attached to it,   this shaft is mounted essentially along the celestial rotation axis of the Earth, rotates continuously and perpetually at constant speed of one turn per day, in the opposite direction of the Earth's rotation,   solar energy collectors mounted on the crossbar and can rotate around this cross bar for at least ±23½°, this rotation defines declination angle,   a co-axial rotation mechanism, though mechanical link, changes the declination angle continuously,   an error correction program controls both rotations.   
     
     
         9 . The 2-axis solar tracking device of  claim 8 , the mechanism that determines the declination angle of the solar energy collectors consists:
 a gear, which is mounted on a beam that is rigidly attached to the main rotating shaft,   a rod with one end pivot connected to this gear and the other end pivot connected the solar energy collector,   a steady rotation of the gear translates into an approximate sinusoidal oscillation of the declination angle of the solar energy collector through the mechanic linking rod,   the amplitude of the oscillation of the declination angle is 23½°.   
     
     
         10 . The 2-axis solar tracking device of  claim 8 , the mechanism that continuously changes the declination angle consists:
 a gear, which rotates coaxially with the main rotating shaft, engages with the other gear whose rotation causes the oscillation of the declination angle,   two independent driving mechanisms that drive this gear and the main rotating shaft,   the differential rotation speed between this gear and the main rotating shaft, combines with the gear ratio in the drive train, continuously changes the declination angle.   
     
     
         11 . The 2-axis solar tracking device of  claim 8 , the error correction program controls both rotations can slightly adjust both rotation speed and/or duration; that will compensate polar tracking errors from all sources. Those small errors are well known and could be tabulate into control programs. 
     
     
         12 . A variance of the 2-axis solar tracking device of  claim 8 , the driving mechanism have an option to rotate the main rotating shaft back and forth with all the benefit of accurate polar tracking during the daylight time. 
     
     
         13 . A variance of the 2-axis solar tracking device of  claim 8 , the error correction program can be extended to counter tracking error when this 2-axis solar tracker is not mounted in polar orientation.