U.S. patent application number 12/852454 was filed with the patent office on 2011-02-24 for two-axes solar tracker system and apparatus for solar panel and likes.
Invention is credited to HENRY H. LIAO.
Application Number | 20110041834 12/852454 |
Document ID | / |
Family ID | 43604290 |
Filed Date | 2011-02-24 |
United States Patent
Application |
20110041834 |
Kind Code |
A1 |
LIAO; HENRY H. |
February 24, 2011 |
Two-Axes Solar Tracker System and Apparatus for Solar Panel and
Likes
Abstract
The present invention relates to a simplified and lower cost
two-axes tracker for solar PV (photovoltaic) or CPV (concentrated
photovoltaic) solar panel, as well as heliostat solar reflectors
and solar Stirling engine. In particular, the disclosure addresses
a simplified and gravity centered tracker structure with low cost
single or dual linear actuators mounted on the side of ground post
which is easier for replacement and maintenance at lower cost.
Inventors: |
LIAO; HENRY H.; (Los
Alamitos, CA) |
Correspondence
Address: |
Flash Intellectual Property, Inc.;Attn. Cheng-Ju Chiang
P.O. Box 766
Chino
CA
91708
US
|
Family ID: |
43604290 |
Appl. No.: |
12/852454 |
Filed: |
August 7, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61274927 |
Aug 24, 2009 |
|
|
|
Current U.S.
Class: |
126/605 |
Current CPC
Class: |
G05D 3/105 20130101;
H02S 20/10 20141201; Y02E 10/47 20130101; F24S 2030/15 20180501;
F24S 30/452 20180501; F24S 2030/115 20180501; F24S 25/10 20180501;
H02S 20/32 20141201 |
Class at
Publication: |
126/605 |
International
Class: |
F24J 2/38 20060101
F24J002/38 |
Claims
1. A two-axes solar tracker apparatus comprising: a ground post
made of an elongated cylindrical tubing including a top end and a
bottom end; wherein said top end providing support to a rotating
head; and wherein said top end of said ground post is either open
or closed; and wherein said bottom end of said ground post being
secured into a substructure such as ground; said rotating head is
made of a larger cylindrical tubing sealed with a top plate;
wherein the inner wall of said rotating head is looped on the outer
wall of said ground post with two bushings or bearings fitting in
the gap at the top and the bottom ends; an elongated cylindrical
horizontal beam (tubing) is attached and balanced on top of said
rotating head directly or via a cylindrical bushing; a tracker
frame is mounted on said horizontal beam symmetrically on two sides
of said rotating head and symmetrically versus said horizontal
beam; one or two azimuth linear actuators attached horizontally to
the side between said ground post and said rotating head for
driving the rotating head and tracker frame in azimuth rotation;
and one elevation linear actuator attached vertically between said
rotating head and said tracker frame for driving said tracker frame
in elevation rotation with axis of rotation centered on said
horizontal beam.
2. The solar tracker apparatus of claim 1 wherein all tracker
frame, post, tubing and components are made of rustproof steel
metal or rustproof metal alloy materials.
3. The solar tracker apparatus of claim 1 wherein the azimuth
rotation is facilitated by said outer rotating head looped on said
inner ground post with said upper and lower bushings or bearings
in-between providing coaxial rotation of said rotating head versus
said ground post; and wherein said upper bushings or bearings
further carry the load of said rotating head and said tracker
frame.
4. The solar tracker apparatus of claim 1 wherein said top bushing
is a cylindrical flanged bushing with flange fitting the inner wall
of said rotating head; and wherein the body of said flanged bushing
fitting the inner wall of said ground post; and wherein an optional
washer bushing is fittingly sitting on top of said flanged bushing
facilitating easier rotation; and wherein said lower bushing is a
cylindrical bushing.
5. The solar tracker apparatus of claim 1 wherein said top bushing
is a combination of one or two disk bushings or washer bushings
fitting at the top end with a first cylindrical bushing fitting at
the top side wall; and wherein said two disk or washer bushings
with lubricant sides face each other facilitating easier rotation;
and wherein a second cylindrical bushing fits at the lower side
wall.
6. The solar tracker apparatus of claim 1 wherein said top bearing
is a tapered roller bearing; and wherein said bottom bearing is a
cylindrical bushing; and wherein said top bearing is replaced by a
combination of a thrust roller bearing at the top end and a
cylindrical bushing at the top side wall; and wherein both said
cylindrical bushings at the side wall is replaced by roller
bearings or needle bearings.
7. The solar tracker apparatus of claim 1 wherein the azimuth
rotation of said rotating head is driven by one linear actuator
with its jack head and body hinged on extended brackets to the
sides of said rotating head and said ground post, respectively; and
wherein said attachment positions of said jack head and said body
of linear actuator is reversed.
8. The solar tracker apparatus of claim 7 wherein a first bracket
is fixed to the side of said rotating head with the jack head of
said linear actuator hinged at the end of said first bracket
horizontally; and wherein the body of said linear actuator is fixed
to a rotating arm; and wherein said rotating arm is hinged on a
second bracket fixed on the ground post; and wherein said linear
actuator rotates horizontally by the extension of said jack head
together with said rotating arm.
9. The solar tracker apparatus of claim 8 wherein said second
bracket is duplicated on the opposite side of said ground post for
the hinging of said rotating arm to rotate said rotating head in
opposite plane.
10. The solar tracker apparatus of claim 1 wherein the azimuth
rotation of said rotating head is driven by dual linear actuators
hinged on brackets to the sides of said rotating head and said
ground post, respectively.
11. The solar tracker apparatus of claim 10 further comprising: an
upper and a lower brackets fixed to the sides of said rotating head
and said ground post respectively; wherein said two linear actuator
bodies are hinged on the open ends of said upper and lower brackets
respectively; and wherein said two linear actuators rotates
horizontally versus said upper and lower brackets, respectively;
and a rotating ring fittingly looped on said ground post between
said upper and lower brackets; and wherein an horizontal arm is
attached to the side of said rotating ring; and wherein the end of
said horizontal arm is attached with a vertical tubing for hinging;
and wherein the jack heads of said two linear actuators are hinged
on top and bottom ends of said vertical tubing; wherein said
rotating head is rotated in azimuth direction more than 180 degrees
by the extension of said jack heads of said lower linear actuator
and said upper linear actuator together.
12. The solar tracker apparatus of claim 1 wherein the azimuth
rotation of said rotating head versus said ground post is driven by
a stepping motor with geared rotor attached on the sides of either
said ground post or said rotating head; and wherein a geared ring
mated to said geared rotor is looped and fixed on said rotating
head or ground post, opposite to said stepping motor attachment;
and wherein said geared ring is replaced by a half circle geared
ring attached onto said rotating head.
13. The solar tracker apparatus of claim 1 wherein the azimuth
rotation of said rotating head is driven by a stepping motor linked
to a worm gear attached on the sides of either said ground post or
said rotating head horizontally; and wherein a slanted teeth geared
ring, mating to said worm gear, is fixed on either said rotating
head or said ground post, opposite to said worm gear and stepping
motor attachment; and wherein said slanted teeth geared ring is
replaced by a half circle slanted geared ring attached onto said
rotating head.
14. The solar tracker apparatus of claim 1 wherein the azimuth
rotation of said rotating head versus said ground post is driven by
a stepping motor with permanent or electromagnetic rotor attached
on said ground post with rotor in close contact with said rotating
head made of magnetic attractable material; and wherein activated
magnetic attraction provide gearless friction force for the
rotation of said rotating head.
15. The solar tracker apparatus of claim 1 wherein said horizontal
beam is secured and balanced on top of said rotating head via a
cylindrical bushing looped on the middle of said horizontal beam
facilitating rotation of said horizontal beam; and wherein
two-sided symmetrical tracker frame is mounted on said horizontal
beam and balanced on said rotating head; and wherein each side of
said tracker frame is further balanced on said horizontal beam with
the elevation rotating axis centered on said horizontal beam.
16. The solar tracker apparatus of claim 1 wherein said horizontal
beam is fixed and secured directly on top and balanced on said
rotating head; and wherein said horizontal beam is looped with
multiple cylindrical bushings for the mounting of crossing beams of
said tracker frame; and wherein said tracker frame is rotated
around said fixed horizontal beam with elevation rotating axis
centered on said horizontal beam.
17. The solar tracker apparatus of claim 1 wherein a linear
actuator with its body hinged vertically on a fix arm attached to
said rotating head, and wherein the jack head of said linear
actuator is hinged directly on said tracker frame, or hinged
vertically on fix arms attached to said horizontal beam; and
wherein the extension of the jack head of said linear actuator
rotates said tracker frame in elevation direction with rotating
axis centered on said horizontal beam.
18. The solar tracker apparatus of claim 1 wherein said tracker
frame is made of crossing reversed T-beams mounted and balanced on
said horizontal beam; and wherein said crossing reversed T-beams
are made of bended sheet metal with reversed U-shaped center T-post
in the middle for the mounting and securing of said photovoltaic
solar panels.
19. The solar tracker apparatus of claim 1 wherein two
electromagnetic wind lock devices with one attached on said ground
post adjacent to said rotating head, and the other attached on said
top plate adjacent to said horizontal beam; and wherein two drum
shaped rod heads are in the center of solenoid of said wind lock
devices; and wherein said rod head are attracted to said rotating
head and said horizontal beam upon solenoid activation; and wherein
said tracker will be locked in desired wind lock position by
electromagnetic attraction force.
20. The solar tracker apparatus of claim 19 wherein said wind lock
devices are activated between consecutive steps of azimuth and
elevation driver activation in a stepwise wind lock of said
two-axes solar tracker rotation.
21. The solar tracker apparatus of claim 1 wherein said tracker
load may be a photovoltaic solar panel, a concentrated photovoltaic
panel, trough or dish concentrator, a heliostat solar reflector, a
solar thermo concentrator or a satellite dish antenna.
22. The solar tracker apparatus of claim 1 wherein said rotating
head and attachment to ground post is modified to be mounted on a
light post; wherein an cylindrical inner tubing with a lower
extruded flange ring is attached to support the tracker frame; and
wherein an outer flanged bushing rotating head is looped fittingly
and matched with the inner tubing flange ring with a thrust washer
bushing and optional cylindrical bushings inserted in-between for
easier rotation; and wherein a horizontal beam mounted with two
sided tracker frames and solar panels is balanced on the flange and
secured on the body of said rotating head.
23. The solar tracker apparatus of claim 22 wherein said inner
tubing with flange ring, said outer flanged bushing and said thrust
washer bushing are made from half cylinders or rings and mated in
the middle to make a full cylinder or ring; and wherein the mating
seams of each cylinder and each ring are interleaved for retrofit
mounting on said light pole.
24. A two-axes solar tracker system comprising: a ground post made
of an elongated cylindrical tubing including a top end and a bottom
end; and wherein said top end providing support to a rotating head;
and wherein said bottom end being secured into a substructure such
as ground; said rotating head is made of a larger cylindrical
tubing sealed with a top plate; wherein said rotating head is
looped on said ground post with multiple bearings fitting in the
gaps between said ground post and said rotating head; an elongated
horizontal beam is attached and balanced on top of said rotating
head; a tracker frame is mounted on said horizontal beam
symmetrically on two sides of said rotating head and symmetrically
versus said horizontal beam; an azimuth motor driver attached
between said ground post and said rotating head for driving said
rotating head and said tracker frame in azimuth rotation; and an
elevation linear actuator attached between said rotating head and
said tracker frame (or said horizontal beam) for driving said
tracker frame in elevation rotation.
25. The solar tracker system of claim 24 wherein the azimuth
rotation is facilitated by said rotating head looped on said inner
ground post with said upper and lower bearings in-between for the
coaxial rotation of said rotating head versus said ground post.
26. The solar tracker system of claim 24 wherein the azimuth
rotation of said rotating head versus said ground post is driven by
single linear actuator attached on the sides between said rotating
head and said ground post.
27. The solar tracker system of claim 24 wherein said tracker
azimuth rotation plane is reversed to opposite side plane by
changing the attachment of said linear actuator to the opposite
side of said ground post.
28. The solar tracker system of claim 24 wherein the azimuth
rotation of said rotating head versus said ground post is driven by
linked dual linear actuators attached on the sides of said rotating
head and said ground post, respectively; and wherein the
combination of said dual linear actuators extensions rotate said
rotating head more than 180 degrees in azimuth direction versus
said ground post.
29. The solar tracker system of claim 24 wherein the azimuth
rotation of said rotating head versus said ground post is driven by
a stepping motor with geared rotor and a gear ring attached of the
ground post and rotating head, respectively; and wherein said
geared rotor is a worm drive rotor.
30. The solar tracker system of claim 24 wherein the azimuth
rotation of said rotating head versus said ground post is driven by
a stepping motor with a permanent or an electromagnetic gearless
rotor with magnetic attraction force for rotation.
31. The solar tracker system of claim 24 wherein elevation rotation
of the tracker frame is via rotation of said horizontal beam
pivoted on top of said rotating head; and wherein the elevation
rotation axis is center on said horizontal beam.
32. The solar tracker system of claim 24 wherein said horizontal
beam is fixed and secured directly on top of said rotating head;
and wherein the elevation rotation is facilitated by the rotation
of said tracker frame with rotating axis pivoted on said horizontal
beam.
33. The solar tracker system of claim 24 wherein the elevation
rotating is driven by linear actuator hinged between said rotating
head and said tracker frame or an extension arm fixed to said
horizontal beam; and wherein the extension of said linear actuator
rotates said tracker frame in elevation direction with rotating
axis centered on said horizontal beam.
34. The solar tracker system of claim 24 wherein two
electromagnetic wind lock devices are installed between said ground
post and said rotating head; and between said rotating head and
said horizontal beam or tracker frame; wherein the activation of
magnetized attraction force will lock said tracker at any desired
azimuth and elevation position, respectively.
35. The solar tracker system of claim 34 wherein said wind lock
devices are activated between consecutive steps of azimuth and
elevation rotations in a stepwise wind lock of said solar tracker
rotation.
36. The solar tracker system of claim 24 wherein said two-axes
tracker is used for a concentrated photovoltaic panel, trough of
dish concentrator, a heliostat solar reflector, a solar thermo
concentrator or a satellite dish antenna.
37. The solar tracker system of claim 24 wherein said rotating head
and attachment to the ground post is modified to be mounted on a
light post for the charging of hybrid or electric automobile during
the day, or for the storage of electricity generated by solar panel
for night lighting.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims benefit of U.S.
Provisional Application Ser. No. 61/274,927, filed on Aug. 24,
2009.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a simplified and lower cost
two-axes tracker for solar PV (photovoltaic) or CPV (concentrated
photovoltaic) solar panel, as well as heliostat solar reflectors
and solar Stirling engine. In particular, the disclosure addresses
a simplified and gravity centered tracker structure with low cost
single or dual linear actuators mounted on the side of ground post
which is easier for replacement and maintenance at lower cost.
[0004] 2. Description of the Prior Art
[0005] Photovoltaic solar panels are gradually becoming a fixture
on roof tops in residential street. The sun exposure to fix panel
on the roof is proportional to sine of sun elevation angle to the
panel. In other words, solar collection on horizontal flat panel at
sunrise and sunset are near zero at lowest elevation angle. At 34
degree latitude location, solar panel could collect 49% more power
if mounted on a two-axes solar tracker relative to a horizontal
fixed panel. The PV panels commonly seen on residential roof are
not practical to have a solar tracker. In a solar farm, mounting
photovoltaic solar panels on a tracker is feasible if the tracker
cost is not predominant. In CPV (Concentrated Photovoltaic)
systems, the solar panels must face the sun directly to concentrate
solar beam with optical accessory. The cost of traditional two-axes
tracker constitute a major cost item for PV and CPV systems. In PV
systems, if the solar tracker cost more than half of the solar
panels cost, it might be as well ignore the solar tracker since the
improvement does not worth the investment. In addition, moving
parts of solar tracker has lower reliability than fixed parts.
However, it is mandatory for CPV systems to collect sun rays
perpendicular to the panel to function properly.
[0006] In concentrated solar thermo power (CSP) applications, solar
trackers are also used to reflect and concentrate sun rays to a
center chamber. A great number of solar reflectors are attached to
two-axes trackers in a large field to collect the solar energy
focusing on a centralized heating chamber of water or molten salt
for turbo engine electricity generation. Such large solar plant is
commonly called "heliostat". The cost of solar trackers constitutes
a major portion of total cost for heliostat farm. In yet another
field of application, the solar thermo Stirling engine also needs
two-axes sun tracking to collect concentrated solar rays to heat up
the Stirling engine in order to generate electricity. This
disclosure will benefit the solar thermo concentration with its
simplified installation, lower parts cost, lower maintenance and
longer durability for a large solar farm.
[0007] A typical two-axes solar tracker consists of a ground post
secured to the ground structure with concrete base. A better
ecological ground post uses a helical pile post drilling directly
into the ground without concrete base. On top of the ground post, a
slewing drive is mounted to support the weight of solar panel and
azimuth rotation at the same time. On top of the slewing drive, a
linear actuator is attached between the slewing drive and solar
panel structure for the lifting of solar panel in the elevation
direction. Two axes of motions in azimuth and elevation will drive
the solar panel to face the sun directly.
[0008] However, there are a few drawbacks with a traditional
tracker. 1) The slewing drive not only has to support the entire
weight of the panel, but also has to bear the lateral force and
torque caused by constant tilting and the wind load on the solar
panel. 2) The weight of solar panel and torque caused by the
lateral force makes the size of slewing drive highly dependant on
the size and weight of solar panel. The components of worm drive
and the rotating gear must be packaged together with the ball
bearings which support the entire weight and torque applied to the
slewing drive, which makes the slewing drive very bulky. 3) If any
fault occurred in the slewing drive, the entire solar panel has to
be dismantled in order to repair or replace the slewing drive. 4)
With the lifting mechanism of a single solar panel by the linear
actuator, the center of gravity of solar panel with respect to the
pivoting point of slewing drive is constantly changing which
mandate the slewing drive to carry the maximum torque possible.
Therefore, the slewing drive and the linear actuator must be
designed for the maximum torque and lateral force of the tilted
panel, which makes a traditional two-axes tracker very bulky and
costly. This disclosure proposes a simplified solar tracker at a
very low cost, light weight and low maintenance for the benefit of
coming solar energy revolution.
BRIEF SUMMARY OF THE INVENTION
[0009] With the above mentioned deficiencies, the subject
disclosure may resolve some or all of the issues related to a
traditional two-axes tracker. In the first aspect of the invention,
the disclosed two-axes tracker is designed to keep the solar panel
weight and lateral force away from the azimuth and elevation
drives. The weight of the solar panel will sit on top of rotating
head, which is looping directly on top of the ground post with
upper and lower bearings fitting in-between. The rotating head and
bearings not only carry the entire panel weight in the vertical
direction, but also leveraged on the torque caused by the wind load
of solar panel in the lateral direction. In addition, the upper and
lower bearings are selectively using low cost, maintenance free
bushing materials for long term usage. Therefore, the azimuth
drive, which is attached to the side between the lower post and
upper rotating head, is free from both the vertical (gravitational
weight) and lateral torque of the solar panel. Hence, the azimuth
drive demands very little force for turning the entire solar
panel.
[0010] In another aspect of the disclosure, the solar tracker will
be divided into two sections of equal weight carried by a
horizontal beam (tubing) with center of gravity on top of the
cylindrical rotating head. Each section of the solar panels are
also balanced on the horizontal beam, enabling rotation of two
solar panel sections around the center line of gravity on the
horizontal beam freely. Therefore, the elevation drive of the solar
panel also demands very little force for rotation similar to the
azimuth drive.
[0011] In another aspect of the disclosure, the azimuth and
elevation drivers can be mounted as an accessory to the side of the
ground post and rotating head with nuts and bolts, which can be
easily installed, removed, replaced in routine maintenance by a
single person. This is the major difference from the traditional
tracker, where the slewing drive is located at the center between
the ground post and solar panel. If anything happen to the slewing
drive, the entire solar panel has to be removed or dismantled. By
attaching the azimuth drive on the side proposed by this
disclosure, it can extend the life of solar tracker by routine
maintenance or replacement of low cost linear actuator.
[0012] In yet another aspect of the disclosure, the two-axes solar
tracker is designed with a wind lock device which can be activated
whenever a strong wind exceeds a threshold. The wind lock device
uses electromagnetic force to lock up the solar tracker in wind
neutral position firmly on the ground post using two
electromagnetic activated locks. This will bear the vibration and
pounding of solar tracker exercised on the linear actuators during
strong wind. Furthermore, in windy areas with constant blowing
wind, this wind lock device can be used in a stepwise wind lock to
protect the linear actuators between activations. This will greatly
prolong the life span of linear actuator and the solar tracker from
wind abuse.
[0013] These and other features, aspects and advantages of the
present disclosure will become understood with reference to the
following description, appended claims and accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is the general view of the two-axes tracker with
rotating cylindrical rotating head before the attachment of linear
actuators.
[0015] FIG. 2 is a sectional view of single linear actuator
attachment to the ground post and rotating head for azimuth
rotation.
[0016] FIGS. 3A-3C illustrate three top views of upper rotating
head rotation versus ground post by linear actuator extension.
[0017] FIG. 4 is a side view of tracker azimuth and elevation
rotation by two linear actuators.
[0018] FIGS. 5A-5C show an alternative solar tracker frame mounting
with rotation around fixed horizontal beam.
[0019] FIG. 6 is a sectional view of double linear actuators for
azimuth rotation.
[0020] FIGS. 7A-7C illustrate three top views of double linear
actuators azimuth rotation.
[0021] FIG. 8 is a sectional view of stepping motor and gear
attachment to the ground post and rotating head for azimuth
rotation.
[0022] FIG. 9 is a sectional view of wind lock devices for azimuth
and elevation lock.
[0023] FIG. 10 is a modified 2-axes tracker for light pole
mount.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Spatially relative terms, such as "beneath", "below",
"lower", "above", "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. It
will be understood that the spatially relative terms are intended
to encompass different orientations of the device in use or
operation in addition to the orientation depicted in the
figures.
Tracker Supporting Structure
[0025] As shown in FIG. 1, one aspect of the disclosed two-axes
tracker generally designated as 10, includes a fixed cylindrical
ground post 20, with a cylindrical rotating head 30 looped on top
of the ground post 20. The rotating head 30 is made of a
cylindrical tube with top end sealed (welded) by a top square plate
36, or other shape such a U-shaped pipe holder, etc. Preferred
embodiment of the ground post 20 and rotating head 30 are made of
rust-proof steel material which attract magnet. Inside the rotating
head, the lower end is a cylindrical bushing 34 tightly fits
between the gap of the ground post and the cylindrical rotating
head. The lower bushing 34 not only facilitates coaxial rotation of
the rotating head versus the ground post, but also leverages on the
lateral torque exercised on the solar panel by the wind load.
Inside the top end of rotating head 30, a cylindrical flanged
bushing 22 (which could be closed at the flange top) is tightly
fitted between the rotating head and the ground post. In other
words, the top flange of bushing 22 fits the inner wall of rotating
head 30 and bottom cylinder of 22 fits inside the inner wall of
ground post 20. Therefore, the top flanged bushing 22 supports the
entire weight of tracker frame and solar panel in the vertical
direction and provides pivot point of lateral wind load torque
leveraged by the lower bushing 34. Preferred embodiment is putting
another thrust washer bushing on top of flanged bushing for easier
rotation. However, commercial flanged bushing may not fit exactly
the inner diameter of outer rotating head and inner diameter of
ground post. Therefore, the flanged bushing can be replaced by top
disk bushing 16 or washer busing 17 as depicted at the right hand
side of flanged bushing in FIG. 1; where the disk diameter can be
smaller than the inner diameter of rotating head. It is even better
to use double layers of disk or washer bushings with lubricant
sides face each other to facilitate smooth frictionless rotation of
the rotating head. The lubricant could be either liquid or solid
lubricant with no refill needed throughout the life time of
tracker. Additional side wall bushing identical to 34 inside the
rotating head at top and bottom ends are needed to maintain coaxial
rotation and lateral support whenever top disk or washer bushings
are used. Preferred embodiment of rotating bushings is made of
metal alloy materials with embedded solid lubricant.
[0026] Alternative to flanged bushing 22 is using a single piece
tapered roller bearing 19, or using a combination of thrust roller
bearing 18 on the top and a cylindrical bushing identical to 34 at
the side wall. However, the top end of ground post needs to be
welded with a cylindrical neck to fit into the center hole of a
tapered roller bearing or a thrust roller bearing. The advantage of
using thrust roller bearing is that its diameter does not have to
fit exactly the inner diameter of rotating head; since identical
cylindrical bushings 34 are used at top and bottom ends to
facilitate rotating head coaxial rotating and bear the lateral
force. Alternative to cylindrical bushing 34 is a cylindrical
roller bearing, or specifically a needle bearing to narrow the gap
between the rotating head and the ground post. Using roller
bearing, the rotating head can be rotated faster with less
friction. However, solar tracker azimuth rotation of 180 degrees in
12 hours daylight is a very slow rotation which enables the usage
of lower cost bushings. In addition, the force needed for rotation
is mainly to counter the wind load on solar panel with a small
proportion used for rotating head.
[0027] Flanged bushing, disk or washer bushings seem to provide the
best combination of lower cost and maintenance free for long term
usage under rough weather conditions. In addition, the cylindrical
bushing, circular flanged bushing and disk or washer bushing
designed for industrial heavy machinery are commercially available
in many sizes. The bushings are made of porous alloy, brass, bronze
or synthetic materials. It also provides low friction rotation and
low maintenance with one time solid lubricant for long term usage
under extreme weather conditions.
[0028] On top of the rotating head, an elongated cylindrical
horizontal beam (tubing) 50 is secured with U-clamps 44 to the top
plate 36 with a cylindrical bushing looped in between as
illustrated in FIG. 1. The top cylindrical bushing is made of
similar material as the bushing inside the rotating head. The
horizontal beam 50 is preferably seamless galvanized steel tubing
for better rotation. On both sides of horizontal beam 50, two
symmetrical tracker frame 521 and solar panel 52 are attached. The
horizontal beam 50 is balanced with center of gravity on the
cylindrical bushing 40. Furthermore, the tracker frames 52 at both
sides of rotating head 30 are further balanced on the horizontal
beam 50 as center line of gravity. Therefore, two sides of solar
panels 52 on the tracker not only balanced on the center
cylindrical bushing 40, but also balanced on the beam 50. The
balanced weight on both axes requires two symmetrical solar panels
52 being mounted on the beam 50. An alternative mounting of tracker
frame with non-rotating beam 50 will be discussed in later section.
This tracker mounting is quite different from traditional solar
panel mounting with one big panel pivoted at the slewing drive and
lifted instead of rotated by a linear actuator. Two sided panels
mounting also has the advantage of allowing near zero degree
elevation to catch the sunrise and sunset on the horizon. In
addition, it is easier to dispose dust and water in vertical panel
position at night. FIG. 1 only illustrates the solar tracker
without azimuth and elevation actuators. It demonstrates that the
tracker can be rotated in azimuth and elevation with minimal force
before any electro-mechanical driver is attached. This is the key
difference from the traditional tracker and advantage of this
disclosure.
[0029] At this point, those skilled in the art may vary the
rotating head attachment to the horizontal beam in many ways. For
example, a square or rectangle beam may replace the cylindrical
beam as long as the section atop the rotating head is cylindrical;
such as a square beam can fit inside cylindrical tube in the middle
section. A square or rectangle beam may be more convenient for
solar panel frame mounting.
Azimuth Rotation with Single Linear Actuator
[0030] FIG. 2 illustrates the sectional view of azimuth rotation
with a single linear actuator attached to the side between the
rotating head and ground post. An L-shaped bracket 38 is attached
onto the upper rotating head 30 with open end linked to the jack
head 27 of linear actuator via a horizontal hinge 25 (a bolt fits
on two holes). The body of linear actuator 28 is attached to the
ground post 20 via a rotating arm 26 which is hinged on 24. Hinge
24 is built like a door hinge fixed on the ground post 20 with an
extended bar. Preferred embodiment of the rotating arm 26 is to
twist the end ninety degrees in order to clamp on the linear
actuator 28 horizontally. It is more logical to attach L-bracket 38
to the upper rotating head 30 since it has larger diameter than
ground post 20; and therefore shorter L-bracket 38 is needed. The
main body of linear actuator 28 is clamped by the rotating arm 26.
Preferred embodiment is clamping on top end of linear actuator body
perpendicular to the arm. Reverse attachment of linear actuator and
jack head on rotating head and ground post is possible, but it is
less preferred.
[0031] In FIGS. 3A-3C, the rotating mechanism of the upper rotating
head 30 versus the lower ground post 20 is illustrated from the
bottom (or top) view. The smaller solid circle is the ground post
20, while the larger dotted circle 30 is the cylindrical rotating
head. The initial position of the tracker is shown in FIG. 3C when
L-bracket 38 and hinge 24 are aligned. The L-bracket 38, arm 26 and
jack head 27 form a right triangle with arm 26 and jack head 27 as
two legs. This is the position of the tracker when the solar panel
normally facing the east in the morning. As the linear actuator
jack head extends as illustrated in FIG. 3B, the jack head will
push the long arm 38 together with the rotating head 30 to rotate
clockwise versus ground post 20. (The actuator 28 will not be
pushed back since in geometry theory with one leg 26 of right
triangle fixed and the other leg 27 extends, the "hypotenuse" line
between hinges 24 and 25 must increase in length as depicted in the
upper right triangle of FIG. 3B. Therefore, rotating head 30 must
be rotated clockwise to increase the hypotenuse which results in
the entire tracker frame rotating clockwise). The solar panel will
be pushed to face south (assuming the tracker is located at
northern hemisphere) in FIG. 3B. In southern hemisphere, the linear
actuator would be attached to opposite side. When the linear
actuator is near fully extended at FIG. 3A, the bracket 38 and
rotating head 30 is pushed near 180.degree. opposite the hinge 24.
Therefore, the solar panel is rotated to face the sunset. A little
more then 180.degree. rotation is possible providing the L-bracket
38 and rotating arm 26 is made longer. This is needed if the
tracker latitude location is just under the tropics. If the tracker
is located at latitude higher then the tropics, the actuator
attachment needs not be changed throughout all seasons of the year.
If the tracker is located between the two tropics, especially near
the equator, dual hinges 24, 74 can be installed on opposite side
of ground post 20 as illustrated at FIG. 3C. On the day when the
sun orbit is crossing the zenith point in the summer, rotating arm
26 and linear actuator can be hinged to opposite side hinge 74 and
the rotating head L-bracket 38 will be rotated 180.degree. to
rotate in opposite plane facing the sun orbit.
[0032] Those skilled in the art can easily change the configuration
of the linear actuator attachment with different length and
different angle of attachment between the ground post, rotating
head, and it is not necessary to form a right triangle in the
initial position. By changing this attachment, it may make azimuth
rotation to a greater angle. But it does not change the essence of
the disclosure of using linear actuator to do the azimuth
rotation.
Elevation Rotation with Linear Actuator
[0033] FIG. 4 illustrates the attachment of the linear actuator for
the rotation of the solar panel in elevation direction. An upper
V-shaped bar 51 is attached to both sides of the horizontal beam 50
with hinge 54 at open end. A lower fixed bar 49 is attached to the
rotating head 30 horizontally with hinge 56 at open end. The hinges
54 and 56 are attached to the jack head and body of the linear
actuator 58 respectively. Alternative to V-shaped bars, the hinge
54 can be attached directly on the tracker frame. As the jack head
of linear actuator 58 extends, the V-shaped bar 51 will rotate the
horizontal beam 50 and tracker frame toward lower elevation angle
(perpendicular line to the panel versus horizon). Since both solar
panels are balanced on the beam 50, the rotation of solar panel
demands little rotational torque. Normally, the maximum required
elevation rotation of solar panel is from zero degree (vertical
position) to 90 degree (flat position). If more than 90 degrees
rotation is needed, it can be accomplished by simply attaching the
horizontal bar 49 to a lower position.
[0034] As one can observe in FIG. 4, the rotation of azimuth linear
actuator 28 shall not be interfered by elevation linear actuator
58. Therefore, the V-shaped bar 51 and fixed horizontal bar 49 must
keep clearance of the azimuth actuator 28. The actuator 58 can be
shorter length with shorter horizontal bar 49 and V-shaped bar 51,
or the rotating head 30 can be made longer. Alternatively, one
shall design the length of azimuth actuator 28 just long enough to
rotate the rotating head 30 to 180 degree while keeping the
horizontal bar 49 long.
[0035] To those skilled in the art, the V-shaped bar and horizontal
bar can be changed in shape and attachment mechanism, such as
changing of V-shaped bar 51 into U-shaped and changing single bar
49 into parallel bars to hinge linear actuator from both sides.
Alternative Elevation Rotation with Non Rotating Beam
[0036] FIGS. 5A-5C illustrate an alternative of rotating the
tracker frame with horizontal beam fixed directly on the top plate
36 of rotating head. The horizontal beam is secured and fixed to
the rotating head plate with simple U-bolts type of device 44
without bushing 40. The horizontal beam is not rotated versus the
rotating head, but rather the tracker frame is rotated with respect
to the horizontal beam. Multiple bushings 59 are secured between
the tracker frame crossing beams and the horizontal beam with
clamps or U-bolts. Preferred embodiment will be a pillow block
clamp 62 securing the cylindrical bushing 59 on the crossing beam
54. The pillow block clamp 62 and cylindrical bushing 59 is
depicted at FIG. 5C.
[0037] If flat photovoltaic solar panels are mounted on the
tracker, the crossing beam may be a reversed T-beam with the height
of T matching the solar panel depth. Preferred embodiment of the
T-beam is made from bended metal strip with a center reversed
U-shaped T-post as depicted in FIG. 5A. The solar panel 52 can be
further secured on the U-shaped T-post from the top edge of panel
with clamping brackets 60 and screw 61 drilled into the bottom of
T-post. With cylindrical bushings, the crossing T-beams 54 of the
tracker frame can be rotated around the fixed horizontal beam 50 by
the linear actuator 58. To complete the tracker frame, L-beams 55
can be connected to both end of crossing T-beams to make a
rectangular tracker frame. Furthermore, four triangular plates 53
can be attached to four corners joining the L-beam and T-beam for
rectangular tracker frame support. The length and spacing of
T-beams shall accommodate the dimension of solar panels 52 to be
mounted. One difference from previous rotating horizontal beam is
that the V-shaped bar 51 must be attached to the tracker frame
rather than on the fixed horizontal beam.
[0038] The alternative installation using rotation of T-beam rather
than rotation of horizontal beam can accommodate larger tracker
frame for larger solar panel output. Comparing to previous
embodiment with one bushing carrying the entire tracker load, the
tracker frame rotation on horizontal beam distributes the larger
tracker load on multiple bushings. Furthermore, non-rotating of the
horizontal beam put less stress on the elevation linear actuator.
The alternative installation is preferred on larger tracker.
Azimuth Rotation with Dual Linear Actuators
[0039] Yet another aspect of the disclosure is the use of two
linear actuators for azimuth rotation as illustrated in FIG. 6. Two
linear actuators 29, 39 are attached to the ground post 20 and
rotating head 30 on L-brackets 25 and 35, respectively. Both
attachments on the L-brackets 25 and 35 are via horizontal rotating
hinges. In between the upper and lower linear actuators, a rotating
ring 21 encircles and attached to the ground post 20 via a
cylindrical bushing or needle bearing. A horizontal arm 23 is fixed
to the rotating ring 21 at one end, and attached with a cylindrical
hinge 27 on the open end. Cylindrical hinge 27 is a simple tubing
with both ends bolted with washer bushings on the jack head rings
of two linear actuators at the top and the bottom,
respectively.
[0040] The rotating mechanism of dual linear actuators is
illustrated in FIGS. 7A-7C. On FIG. 7C is the closed position of
two linear actuators; where the linear actuator 39 is on top of
linear actuator 29 with rotating ring 21 and hinge 27 in between.
When the lower actuator 29 extends, the upper actuator 39 and
rotating head 30 will be pushed to turn clockwise, together with
the rotating ring 21, arm 23 and hinge 27. In FIG. 7B, the position
of rotating head 30 is turned about 120.degree. when the lower
actuator 29 is fully extended while the actuator 39 is still in the
initial position. When the upper actuator 39 is fully extended, the
rotating head 30 attached to actuator 39 is further rotated about
120 more degrees at FIG. 7A. In the second rotation, the center
ring 21, horizontal arm 23 and rotating hinge 27 stay in the same
position. Therefore, the upper rotating head 30 can be rotated
about 240 degrees with respect to the lower ground post 20.
[0041] The advantages of using two linear actuators are twofold; 1)
the rotating head 30 can be rotated more than 180 degrees to around
240 degrees, 2) two shorter linear actuators are used instead of a
single long actuator. By rotating 240 degrees, the area of the
world between two Tropics zones can benefit without moving the
actuators whenever the Sun orbit is crossing the Zenith point.
These tropical zones of the world enjoy the most sunshine days
throughout the year. The disadvantage of dual linear actuator is
that the actuators must be very short to make clearance for the
solar panels in low elevation angle. However, if traditional
lifting of solar panel for elevation rather than rotating for
elevation is used, the dual linear actuators may not have the
problem of clearance.
Azimuth Rotation with Stepping Motor and Geared Drive
[0042] Yet another aspect of the disclosure is the use of direct
stepping motor drive with gear ring looped on either the rotating
head or the ground post as illustrated in FIG. 8. For illustration,
the gear ring 31 is fixed on the rotating head 30. The direct drive
stepping motor 33 is then attached to the ground post 20 with
matching rotor gear 32. Reduction gear may be used for the stepping
motor to get finer rotation resolution. Alternatively, the stepping
motor and gear ring can be changed in positions. It is a custom
designed fitting to mate the rotor gear 32 and gear ring 31 for
desired resolution in azimuth rotation. If the gear ring has 720
teeth, then 180.degree. rotation will take 360 steps of geared
rotation. If each stepping of motor makes one tooth step without
gear reduction, it results in half degree of azimuth rotation.
Finer resolution requires either increase the teeth number of gear
ring or gear reduction in stepping motor. It is noticed that a
circular gear ring 31 is hard to replace after the tracker is
installed in place. Instead, a half circle gear ring 311 depicted
at the left of FIG. 8. is used for half circle or more rotation.
Half circle gear ring 311 has the advantage of retrofitting onto
the rotating head if the original ring wore out or rusted after
long term usage. The half circle can be more than 180 degrees which
can be looped up from the smaller ground post while
installation.
[0043] Another alternative of geared ring with stepping motor is
using a horizontal worm drive gear 32 mating with a slanted gear
ring 41 as depicted in the lower right corner of FIG. 8. A stepping
motor 43 is coupled with the worm drive 42 as illustrated. The worm
drive 42 is used mostly in existing two-axes tracker slewing drive
packed together with the azimuth rotating ball bearing ring. Using
worm drive with slanted gear ring together with motor gear
reduction can achieve desired rotation resolution without changing
the gear ring teeth number. It also has smoother rotation with
slanted gear teeth.
[0044] The advantage of this approach is the stepping motor and
geared ring takes little space on the rotating head and ground post
to avoid interference with elevation actuator. Also, the rotating
head can be rotated 360 degrees potentially. It could be lower cost
if mass production of identical geared motor is needed in a large
scale solar farm. However, the disadvantages of this approach are:
1) The gear ring and stepping motor are exposed to adverse weather
condition which need to be covered and sealed to protect the gear
and motor, 2) The gear ring and rotor gear has to be custom made
for every size of rotating head, 3) The mating between gear ring
and stepping motor must be tightly fitted which may become a
problem after wind load damage and long term vibration, 4) Replace
the wear out gear ring must remove the rotating head or two piece
gear ring being designed.
Azimuth Rotation with Stepping Motor and Magnetic Rotor
[0045] Yet another aspect of the disclosure is the use of direct
stepping motor drive without a geared ring on the rotating head.
Instead, a permanent or electromagnetic magnetic rotor 321 is used
for the rotor of the stepping motor with or without reduction gear
as depicted at the lower left corner of FIG. 8. The rotating head
30 must be made of steel material attractable by the magnetic
rotor. It is equivalent to a gearless friction rotor 321 versus the
rotating head 30. However, the magnetic attraction by the rotor
ensures non-slipping in the friction drive between the rotor 321
and the rotating head 30. The rotating force or rotating friction
is proportional to the size of magnetic rotor 321. Therefore, the
larger the size and the heavier the weight of the tracker frame
load, the stronger the magnetic force needed. However, since the
larger tracker requires larger ground post 20 and rotating head 30,
the magnetic rotor 321 can be larger as well. Furthermore, if
electromagnetic rotor is used, the attraction force is proportional
to the solenoid current and number of rings of winding wire. The
rotor can be smaller diameter with much stronger force than the
permanent magnet.
[0046] The advantage of magnetic rotor is the simplicity and lower
cost of the azimuth drive. Without the gear ring and geared rotor,
it removes the problem of corrosion, rain and dust cover,
maintenance and lubrication. The ratio of the diameter of rotating
head 30 divided by the diameter of magnetic rotor 321; multiplied
by the steps per revolution of stepping motor will be the azimuth
resolution in one revolution. A resolution of one to two degrees is
adequate for a photovoltaic solar panel. Higher degree of
resolution needs reduction gear in the rotor for higher precision
systems such as CPV or Heliostat tracker.
Wind Lock Devices for Azimuth and Elevation Rotations
[0047] It is shown in FIG. 3A-3C that the installed solar panel 52
is best to be aligned with L-bracket 38 to avoid interference with
the linear actuator 28. As depicted at FIG. 3C, the jack head 27
force vectors is largest since the jack head is near perpendicular
to the L-bracket 38 and the solar panel 52 in FIG. 3A, the force
vector is smallest with slanted angle between the jack head 27 and
L-bracket 38. This position is not good for the wind load pushing
on the linear actuator at a small slanted angle. For elevation
rotation shown in FIG. 4, the problem becomes even worse when fully
extended jack head of linear actuator 58 with smallest slanted
angle. It must stand up against maximum side blowing wind on near
vertical solar panel.
[0048] A proposed solution to the above problem is using an
electromagnetic wind lock devices 65 as depicted in FIG. 9. Since
both rotating head 30 in azimuth rotation and horizontal beam 50 in
elevation rotation is cylindrical shaped, an electromagnetic lock
shaped like an old style automobile drum brake is used. The
difference is that the drum brake uses friction force for braking
while the wind lock uses the electromagnetic attraction force for
locking In FIG. 9, the rod 63 of an electromagnetic lock device 65
is drum shaped matching cylindrical tubing with a solenoid
activation coil 64 surrounding the rod at back. When solenoid 64 is
activated by DC current, the rod 63 will be magnetized to attract
to the rotating head 30 or the horizontal beam 50 both made of
steel for wind locking However, in the design when horizontal beam
is fixed with rotating tracker frame, the electromagnetic rod head
has to be designed to attract the tracker frame. The wind lock
device 65 is attached to the ground post 20 and top plate 36 with
securing brackets 66 for the azimuth and elevation wind lock
devices 65, respectively. The wind lock devices 65 are useful
devices to protect the linear actuator in the flat solar tracker
position to counter strong wind exceeding designed threshold.
[0049] In this disclosure, we propose an even more useful
application of the wind lock device. In windy places such as costal
areas when the solar panel is under constant wind assault, the
linear actuators will be under perpetual wind abuse and prone to
failure. An innovative idea is adopting a stepwise wind lock to
counter constant blowing wind using the same wind lock device. The
procedure of stepwise wind lock is described as follows: 1) The
wind locking period down-counter reaches zero at the tracker
controller, 2) The electromagnetic solenoid 64 is commanded by the
controller to release rod 63 to unlock position, 3) The linear
actuator 28 or 58 is commanded by controller to rotate one step in
azimuth or elevation direction, 4) The wind lock rod 63 is
activated to lock up the tracker in current position and the
tracker controller restart the locking period down counter.
[0050] It is a very slow motion for the tracker rotation in a day.
The most azimuth rotation is 180 degrees, while the most elevation
rotation is only 90 degrees. If the rotation is happened at equinox
day with 12 hours of day light, each degree of azimuth rotation
takes 4 minutes while elevation rotation takes 8 minutes. On the
other hand, each step of linear actuator activation may take only
fraction of second. Therefore, the solar tracker is in the locking
state for majority of time. The wind locking between consecutive
activations will alleviate the linear actuator from constant wind
load vibration and pounding. This will prolong the life of linear
actuators and therefore increase the life of solar tracker in windy
areas.
Mounting Two-Axes Solar Tracker on Light Pole
[0051] FIG. 10 illustrates subject two-axes tracker modified to be
mounted on a light pole. Since the light pole is not uniformly
cylindrical shaped with the base larger than the top, an inner
uniform cylindrical tubing 20 is looped and secured on the light
pole at the top and bottom ends. The cylindrical tubing substitute
the ground post 20 in FIG. 1. But there is an extruded flange ring
36 attached on the bottom part of tubing 20 to serve similar
function of holding and supporting the rotating head 30. The
rotating head 30 is build like a flanged bushing with the bottom
flange sitting on top of extruded flange 36 of inner tubing 20. An
optional thrust washer 17 is inserted between the flange ring 36
and flange bushing 30 facilitating easier rotation. Also, there are
optional upper and lower bushings 34 inserted fittingly between the
inner tubing 20 and outer rotating head 30 facilitating easier
rotation and bear the lateral torque and force. However, if the
outer lining of tubing 20 and inner lining of rotating head 30 are
made of porous bushing material and fit nicely, the bushings 34 are
not necessary.
[0052] The horizontal beam 50 is held on by the flange of the
rotating head 30 and secured with U-bolts to the body of rotating
head 30 horizontally. Multiple cylindrical bushings 56 are looped
on the horizontal beam for the elevation rotation of solar panels
52. It is identical to the elevation rotation with non-rotating
beam discussed previously. In addition, a rechargeable battery and
controller box 45 is attached at convenient location of the light
pole for night time lighting.
[0053] The attachment of azimuth rotation with single or dual
linear actuators is similar to those described in FIGS. 2 and 6.
The elevation rotating is similar to that described in FIG. 4
except the elevation actuator is mounted on one side of the
rotating head and tracker frame rather than the center as depicted
in FIG. 4.
[0054] The construction of inner tubing 20 and outer rotating head
30 will depend on whether the tubing can be looped on the pole from
the top. It will be easier with a complete rotating assembly built
and looped from the top before the light fixture is installed.
However, retrofitting on existing light pole will be a challenging
engineering problem. It will require inner tubing, outer tubing and
thrust washer to be built in half cylinders or rings and mated to
make full cylindrical inner and outer tubing. Furthermore, the
mating seams of each cylinder and each washer ring are preferred to
be interleaved while mounting to provide better security for the
mating seams.
[0055] Although various aspects of the disclosed two-axes tracker
have been shown and described, modification may occur to those
skilled in the art upon reading the specification. Furthermore,
many aspects of the disclosed two-axes tracker is not limited to
photovoltaic panel tracking application, but can be applied to much
broader aspect of solar tracking, or satellite tracking For
example, the disclosed two-axes tracker can be used for a
concentrated photovoltaic panel; a dish concentrator for Stirling
engine, a heliostat solar reflector, a linear trough solar
concentrator, a solar thermo concentrator or a satellite dish
antenna. The present application includes such applications or
modifications and limited only by the scope of the claims.
* * * * *