U.S. patent application number 12/793510 was filed with the patent office on 2010-12-09 for solar panel tracking and mounting system.
Invention is credited to Ken Hyun Park.
Application Number | 20100307479 12/793510 |
Document ID | / |
Family ID | 43298529 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100307479 |
Kind Code |
A1 |
Park; Ken Hyun |
December 9, 2010 |
Solar Panel Tracking and Mounting System
Abstract
A method for tracking solar panels includes the steps (a)
beginning a tracking cycle substantially at sunrise with adjacent
tilting panels all horizontal, (b) tilting the adjacent panels in
unison in a first angular direction toward the rising sun at a tilt
rate that just avoids shading of adjacent panels, (c) reversing
direction of panel tilt at a point that the panels reach either a
maximum tilt limited by mechanical design, or the panel surfaces
are orthogonal to the rising sun, (d) tilting the adjacent panels
in a second angular direction, following movement of the sun and
keeping the surface of the panels at right angles to the sun's
position, until a point is reached that shadowing is imminent from
the angle of the setting sun, and (e) reversing direction of panel
tilt again to the first angular direction, adjusting tilt as the
sun sets to avoid shading until the panels are again
horizontal.
Inventors: |
Park; Ken Hyun; (San Jose,
CA) |
Correspondence
Address: |
CENTRAL COAST PATENT AGENCY, INC
3 HANGAR WAY SUITE D
WATSONVILLE
CA
95076
US
|
Family ID: |
43298529 |
Appl. No.: |
12/793510 |
Filed: |
June 3, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61217794 |
Jun 3, 2009 |
|
|
|
61268237 |
Jun 9, 2009 |
|
|
|
61311745 |
Mar 8, 2010 |
|
|
|
Current U.S.
Class: |
126/601 ;
126/714 |
Current CPC
Class: |
H02S 20/00 20130101;
F24S 50/00 20180501; F24S 50/20 20180501; Y02E 10/47 20130101; F24S
30/425 20180501; Y02E 10/50 20130101; H02S 20/32 20141201; H01L
31/052 20130101 |
Class at
Publication: |
126/601 ;
126/714 |
International
Class: |
F24J 2/38 20060101
F24J002/38; F24J 2/00 20060101 F24J002/00 |
Claims
1. A method for tracking solar panels comprising the steps of: (a)
beginning a tracking cycle substantially at sunrise with adjacent
tilting panels all horizontal; (b) tilting the adjacent panels in
unison in a first angular direction toward the rising sun at a tilt
rate that just avoids shading of adjacent panels; (c) reversing
direction of panel tilt at a point that the panels reach either a
maximum tilt limited by mechanical design, or the panel surfaces
are orthogonal to the rising sun; (d) tilting the adjacent panels
in a second angular direction, following movement of the sun and
keeping the surface of the panels at right angles to the sun's
position, until a point is reached that shadowing is imminent from
the angle of the setting sun; (e) reversing direction of panel tilt
again to the first angular direction, adjusting tilt as the sun
sets to avoid shading until the panels are again horizontal.
2. The method of claim 1 wherein, in steps (b) and (e) the tilting
allows a pre-programmed constant percentage of shading to
occur.
3. The method of claim 1 wherein, in steps (b) and (e) the tilting
allows a pre-programmed percentage of shading to occur, and the
percentage varies with angle of tilt.
4. The method of claim 1 wherein tilting is accomplished in a
continuous motion.
5. The method of claim 1 wherein tilting is accomplished
incrementally at pre-programmed time increments
6. A solar panel system comprising: a plurality of solar panels
having a length substantially greater than a width, mounted
side-by-side with each panel enabled to tilt about along an axis in
the direction of the length of the panel; a tilting mechanism
coupled to adjacent panels, capable of tilting the panels in either
of two rotating directions about the panel axes; and a programmable
drive control enabled to control the rate and direction of tilt for
the panels in unison in a tracking cycle; wherein the tracking
cycle begins substantially at sunrise with the panels horizontal,
the panels are tilted in unison in a first angular direction toward
the rising sun at a tilt rate that just avoids shading of adjacent
panels, direction of tilt is reversed at a point that the panels
reach either a maximum tilt limited by mechanical design, or the
panel surfaces are orthogonal to the rising sun, the panels are
tilted in a second angular direction, following movement of the sun
and keeping the surface of the panels at right angles to the sun's
position, until a point is reached that shadowing is imminent from
the angle of the setting sun, and tilting direction is reversed
again to the first angular direction, adjusting tilt as the sun
sets to avoid shading until the panels are again horizontal.
7. The system of claim 6 wherein the tilting allows a
pre-programmed constant percentage of shading to occur.
8. The system of claim 6 wherein the tilting allows a
pre-programmed percentage of shading to occur and the percentage
varies with angle of tilt.
9. The system of claim 6 wherein tilting is accomplished in a
continuous motion.
10. The system of claim 6 wherein tilting is accomplished
incrementally at pre-programmed time increments.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims priority to a U.S. provisional
patent application Ser. Nos. 61/217,794, filed on Jun. 3, 2009,
61/268,237, filed on Jun. 9, 2009, and 61/311,745, filed on Mar. 8,
2010, disclosures of which are incorporated at least by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is in the field of solar tracking
systems and pertains particularly to methods and apparatus for
tracking the sun using at least one tilt angle while minimizing any
shadowing on adjacent solar collection panels.
[0004] 2. Discussion of the State of the Art
[0005] In the field of solar tracking systems, there are system
that can produce substantially more energy (watts/panel) compared
to fixed arrays of the same type and capacity by enabling tracking
of the sun. This difference is most pronounced for those using
crystalline silicon PV technologies, where a single-axis tracking
systems could add up to 30% more energy. However, there is a
drawback involved. When one side of array is raised at low sun
angles, the arrays cast larger shadows and require greater
separation compared to their fixed counterparts. Again, this
penalty is costliest for crystalline PV systems because relatively
small shading may result in a disproportionate reduction in power
generated by the system.
[0006] The overriding objective of a typical commercial or
residential rooftop installation is to achieve the highest energy
density within a confined rooftop space. Obviously, the extra
spacing lowers installation density in terms of the number of
panels/unit of area. Because of the space, weight and other
constraints, the fast-growing commercial segment has been largely
bypassing the conventional tracking option.
[0007] Today, practically all rooftop-based commercial solar
installations are fixed and most of the tracking systems can be
found in large utility-scale ground-based installations in remote
areas where space is relatively inexpensive and abundantly
available. Therefore, what is clearly needed is a solar tracking
system and method for tracking the sun that can minimize shadowing
thrown on adjacent panels and allow for more panels to be placed in
a smaller footprint without reducing the amount of efficiency of
the system.
SUMMARY OF THE INVENTION
[0008] The problem stated above is that maximum efficiency is
desirable for a solar collector system or array, but many of the
conventional means for maximizing solar energy collection is solar
system also create complexity and cost. The inventors therefore
considered functional elements of a modular solar collector system,
looking for elements that exhibit interoperability that could
potentially be harnessed to provide energy but in a manner that
would not create drag.
[0009] Every solar system is propelled by the suns rays, one
by-product of which is an abundance of stored energy that can be
utilized directly. Most such systems employ solar panels and
tilting means to minimize angle of incidence (AOI) thereby
increasing energy savings.
[0010] The present inventor realized in an inventive moment that
if, during solar tracking, modular solar collecting devices could
be caused to track the sun in unison using both synchronous and
counter synchronous tracking such that by one or more pivot axis'
the panels may be caused to tilt and/or track along those axis',
more solar efficiency in solar energy collection might be realized.
The inventor therefore constructed a unique modular system of solar
collection devices for rooftops and commercial installations that
allowed minimization of AOI during solar tracking thereby
increasing solar collection efficiency during the solar tracking
operation. A significant reduction in work results, with no
impediment to solar footprint or existing solar efficiency ratings
created.
[0011] Accordingly, in an embodiment of the present invention, a
method for tracking solar panels is provided comprising the steps
of (a) beginning a tracking cycle substantially at sunrise with
adjacent tilting panels all horizontal, (b) tilting the adjacent
panels in unison in a first angular direction toward the rising sun
at a tilt rate that just avoids shading of adjacent panels, (c)
reversing direction of panel tilt at a point that the panels reach
either a maximum tilt limited by mechanical design, or the panel
surfaces are orthogonal to the rising sun, (d) tilting the adjacent
panels in a second angular direction, following movement of the sun
and keeping the surface of the panels at right angles to the sun's
position, until a point is reached that shadowing is imminent from
the angle of the setting sun; and (e) reversing direction of panel
tilt again to the first angular direction, adjusting tilt as the
sun sets to avoid shading until the panels are again
horizontal.
[0012] In one aspect of the method in steps (b) and (e), tilting
allows a pre-programmed percentage of shading to occur. In a
variation of this aspect, in steps (b) and (e) the tilting allows a
pre-programmed constant percentage of shading to occur. In a
variation of this aspect, in steps (b) and (e) the tilting allows a
pre-programmed percentage of shading to occur, and the percentage
varies with angle of tilt. In one aspect the tilting is
accomplished in a continuous motion. In another aspect the tilting
is accomplished incrementally at pre-programmed time
increments.
[0013] In one aspect of the present invention a solar panel system
is provided and includes a plurality of solar panels having a
length substantially greater than a width mounted side-by-side with
each panel enabled to tilt about along an axis in the direction of
the length of the panel, a tilting mechanism coupled to adjacent
panels, capable of tilting the panels in either of two rotating
directions about the panel axes, and a programmable drive control
enabled to control the rate and direction of tilt for the panels in
unison in a tracking cycle.
[0014] The tracking cycle begins substantially at sunrise with the
panels horizontal, the panels are tilted in unison in a first
angular direction toward the rising sun at a tilt rate that just
avoids shading of adjacent panels, direction of tilt is reversed at
a point that the panels reach either a maximum tilt limited by
mechanical design, or the panel surfaces are orthogonal to the
rising sun, the panels are tilted in a second angular direction,
following movement of the sun and keeping the surface of the panels
at right angles to the sun's position, until a point is reached
that shadowing is imminent from the angle of the setting sun, and
tilting direction is reversed again to the first angular direction,
adjusting tilt as the sun sets to avoid shading until the panels
are again horizontal.
[0015] In one embodiment the tilting allows a pre-programmed
constant percentage of shading to occur. In another embodiment the
tilting allows a pre-programmed percentage of shading to occur, and
the percentage varies with angle of tilt. In one embodiment tilting
is accomplished in a continuous motion. In another embodiment
tilting is accomplished incrementally at pre-programmed time
increments.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0016] FIG. 1 is a block diagram illustrating tilt capabilities of
a solar collection device for maximizing exposure to the sun.
[0017] FIG. 2 is a perspective view of a modular solar device
including brackets for installation.
[0018] FIG. 3 is a perspective view of a modular solar device
having slot adapters for installation.
[0019] FIG. 4 is a side view of a modular solar device illustrating
horizontal tilt capability according to an embodiment of the
present invention.
[0020] FIG. 5 is a perspective view of a standard solar panel
installation.
[0021] FIG. 6 is a perspective view of a modular device according
to an embodiment of the present invention.
[0022] FIG. 7 is a perspective view of a modular solar array
according to an embodiment of the present invention.
[0023] FIG. 8 is an architectural overview of an integrated network
for remote access and maintenance of a system of flat-panel
arrays.
[0024] FIG. 9 is a perspective view of a modular device array
according to an embodiment of the present invention.
[0025] FIG. 10 is a perspective view of a modular device array
including a lateral transfer system according to another embodiment
of the present invention.
[0026] FIG. 11 is a perspective view of a flat panel array
according to another embodiment of the present invention.
[0027] FIG. 12 is a perspective view of several gantry robot
configurations according to an embodiment of the present
invention.
[0028] FIG. 13 is a cutaway view of a multi track robot according
to an embodiment of the present invention.
[0029] FIG. 14 is a cutaway view of a multi-track robot according
to another embodiment of the present invention.
[0030] FIG. 15 is a perspective view of optional hose or cable
feeder/tensioner assemblies for use in cleaning operations
according to embodiments of the present invention.
[0031] FIG. 16 is a top view of a robot tracking on a hybrid
tracking system 1600 according to an embodiment of the present
invention.
[0032] FIG. 17 is a top view of a robot tracking on a hybrid
tracking system according to another embodiment of the present
invention.
[0033] FIG. 18 is a top view of a robot tracking on a tracking
system according to a further embodiment of the present
invention.
[0034] FIG. 19 is a logical block diagram illustrating angle of
incidence (AOI) of the sun against a solar array.
[0035] FIG. 20 is a block diagram illustrating an angular range of
motion (AROM) for a solar panel according to an embodiment of the
present invention.
[0036] FIG. 21 is an elevation view of a modular device
illustrating inter-array spacing or separation.
[0037] FIG. 22 is a chart illustrating retrograde tracking
according to an embodiment of the present invention.
[0038] FIG. 23 through FIG. 27 are block diagrams illustrating two
solar units in various states of solar tracking in unison.
[0039] FIG. 28 is a perspective view illustrating two array
configuration options according to an embodiment of the present
invention.
[0040] FIG. 29 is a perspective view of a single sub-frame section
of linkable frame component of FIG. 28.
[0041] FIG. 30 is a partial view of a frame member according to an
embodiment of the present invention.
[0042] FIG. 31 is a perspective view of frame member of FIG. 30
showing outer skin and multiple tilt mechanisms.
[0043] FIG. 32 is a block diagram illustrating basic tracking
module components of a tracking module.
[0044] FIG. 33 is a partial view of a frame member of the modular
solar collecting system of the present invention.
DETAILED DESCRIPTION
[0045] The inventor provides a modular solar collector system that
has dual sun-tracking capabilities, self-inspection and
self-cleaning maintenance capabilities, and other general
improvements over standard art systems for residential and
commercial use. The present invention is described in enabling
detail using the following examples, of which may show more than
one useful embodiment of the present invention.
[0046] The terms solar panel and solar module are commonly used
interchangeably in documents that describe conventional solar
collecting systems. However, in this specification, and to avoid
confusion, the terms modular solar collecting device or simply
modular device shall be used to reference a fully-functioning solar
collecting unit enclosed in a rigid sub-structure with full
electrical and/or thermal connections. The modular device of the
present invention two or more such devices comprising a modular
solar collecting system, may be functionally similar to solar
panels/modules in the conventional system with respect to solar
collecting technologies and may encompass, but may not be limited
to, mono or poly-crystalline silicon photovoltaic (PV),
thin-film-based PV, concentrator PV (CPV) and concentrating solar
thermal (CST) technologies.
Modular Solar Collecting System with Linking Hardware and Device
Tilting Capability
[0047] Modular devices of the present invention may or may not be
longer in length than conventional solar panels, but are likely to
be narrower in width compared to their conventional counterparts.
Wider devices have larger axial tilting radii requiring greater
mounting heights for ground clearance, which is a problem in the
art that the present invention is designed to overcome. For the
purposes of this specification, an integrated group of modular
devices comprises a modular subsystem and one or more of installed
modular subsystems comprise a modular sub-system array. A typical
solar installation, whether commercial or residential, has one or
more arrays.
[0048] FIG. 1 is a block diagram illustrating tilt capabilities of
a solar collection device for maximizing exposure to the sun. To
attain the maximum efficiency in collecting solar rays, the
surfaces of solar collecting devices should be orthogonal to the
sun at noon when its intensity peaks. In reality however, the
orientations of installation surfaces of solar systems are rarely
optimal. Tilting compensates for poor device orientation
(steep/shallow sloping surface or offset from true south in the
northern hemisphere). Therefore a capability of tilting the devices
can work to correct offset angles (.theta.).
[0049] A solar collecting device 101 has panels 104 that tilt
horizontally to optimize the exposure to sun 103. A solar
collecting device 102 has solar panels 105 that compensate or
adjust for meridian of sun 103. Therefore a modular solar device
has panels that may tilt horizontally and vertically to optimize
exposure to the sun thus maximizing the efficiency of the unit.
[0050] FIG. 2 is a perspective view of a modular solar device
including brackets for installation. FIG. 3 is a perspective view
of a modular solar device having slot adapters for installation.
Referring now to FIG. 2, a modular device 201 may be manufactured
of 2.times.12 silicon-based PV cells 205. Device 201 includes
mounting brackets (202), one per side. Mounting brackets 202
include upper and lower pivot points 203 and 204 respectively. A
dashed line is illustrated in this example and represents the tilt
axis of the device.
[0051] Referring now to FIG. 3, a modular solar collecting device
301 is illustrated and includes a uniform coating 303 of thin-film
PV. Device 301 includes slot adapters 302, one at each end in this
example. Slot adapters 302 may be of various shapes and sizes. The
slot adapters are mated to slot receptacles, (not illustrated) on a
frame component to establish mechanical connection. Carbon
composites or other light weight materials may be used in
manufacture of the modular device's sub-structure. Individual
modular devices may or may not be equipped with dedicated
micro-inverters (not illustrated) that convert DC modular devices
into AC modular devices.
[0052] In one embodiment a modular device with tilting capability
comprises a section of extruded rectangular tubing having a top
surface, a bottom surface and two side surfaces. Photovoltaic or
other types of solar cells, PV coatings or a combination may be
applied to the top surface, the bottom surface, and the side
surfaces in order to improve overall efficiency by harvesting power
from indirect light either reflected or refracted to the bottom and
side surfaces of the device. In one aspect of this configuration
thin film PV coatings may be used on the sides and bottom surface
of the modular device. As costs continue to come down for thin film
coatings, the practicality of employing them to enhance efficiency
by applying them on secondary device surfaces may become more
practical.
[0053] In one embodiment a modular subsystem includes multiple
modular solar collecting devices, a frame that holds the modular
devices and hardware that connect individual modular devices
together and provides pivot points. A frame (not illustrated here)
may be as simple as a rectangular box with angled cutouts for
"hanging" modular devices at a desired angle. In another embodiment
a frame may include pivot points and a tilting mechanism
incorporated within the thickness of its wall. In a "plug and play"
embodiment, modular devices may be pushed into slotted and pivoted
receptacles built into the sides of a frame. The simple insertion
may lock the devices in place and establish both mechanical and
electrical connections.
[0054] Frames provided to contain modular devices may be made of
any one of a number of hard man-made/synthetic materials such as
steel, aluminum, fiberglass, carbon composite, or plastics,
depending in part on cost, weight and durability. Frames may or may
not be manufactured using molding or extrusion method. Pre-drilled
holes, notches and other provisions may facilitate easy fastening
to various types of installation surfaces. Pre-fabricated frames
may be available in different lengths to hold fixed numbers of
modular devices, but two end plates may be identical. Made-to-order
frames, however, may accommodate any number of modular devices as
required by end-user.
[0055] In a conventional system solar collectors or cells, for
example, are directly installed on a simple rack structure. In the
modular system of the present invention, it is preferable to first
mount a number of modular devices in a rigid rectangular frame that
mechanically connects them together in a parallel "louver-like"
arrangement. The mechanical connections allow them to tilt in sync
as a single integrated unit. Electrical and thermal integration may
be also made at this point. The framing and the interconnections
transform these modular devices into a modular subsystem that is
ready to be installed. The modular subsystem is comprised of
modular solar collecting devices, a frame that holds the modular
devices and hardware that connect individual modular devices
together and provides pivot points.
[0056] FIG. 4 is a side view of a modular solar device 401
illustrating horizontal tilt capability described further above
according to an embodiment of the present invention. Modular solar
device 401 contains multiple modular solar collecting devices 405,
which may be analogous to solar devices 201 described further above
in this specification.
[0057] In this example, devices are mounted on a frame 402 by the
upper pivot points allowing the devices to tilt axially
(lengthwise). The lower pivot points may be connected to a tilt bar
or device connection bar 403. The device connection bar 403 enables
a synchronized tilt of the installed devices to an angle that is
appropriate for maximizing energy collection according to position
of the sun.
[0058] FIG. 5 is a perspective view of a standard solar panel
installation. FIG. 6 is a perspective view of a modular device
according to an embodiment of the present invention. Referring now
to FIG. 5 and to FIG. 6, the two arrays illustrated underscore the
difference between the conventional and modular systems. Referring
now to FIG. 5, a conventional solar array 501 is illustrated. Solar
array 501 comprises an aggregation of panels 503 onto a racking
structure 502. Racking structure 502 is provided at a fixed
elevation in order to orientate the array toward the sun. However,
this tilting method is only practical for installations on flat
surfaces. For sloped rooftop installations where solar arrays need
to be "flush" with the roof, such elevation is usually not an
option. As a result, a majority of conventional rooftop
installations face less than ideal angles and therefore are less
efficient in collecting energy.
[0059] Referring now to FIG. 6, a modular solar array 601 is
provided and may be installed directly on the installation surface
without any racking structure like racking structure 502. To
install a modular array, blank frames such as a frame 602 may be
first positioned, shimmed and fastened to the installation surface.
Then modular devices such as devices 201 may be installed inside
one-by-one until the frames are filled. Finally, the tilt
adjustment may be made within the frames. This installation process
may reduce labor cost. The low-profile mounting and tilting means
superior installation flexibility.
[0060] So far in this specification tilting of solar collection
devices has been illustrated as a way to optimize the angle of
incidence in contact with the solar rays. While tilt adjustments
may be sufficient for some solar installations, a much greater
level of efficiency may be obtained through passive and or active
tracking of the Sun. Tracking for the purposes of this
specification shall mean the continuous following of the sun to
maintain the optimal angle of the suns rays against a modular
device as long as possible. The modular subsystem of the present
invention includes a built-in synchronized tilting capability that
make solar tracking easily attainable. For example, a tracking
module (not illustrated) installed over one of the end plates of
the system may convert any modular subsystem into a low-profile
tracking system that is practical even for small rooftop
installations.
[0061] In such a system, inside the tracking module, tracking
motion may be attained in a number of ways including but not
limited to using an in-line actuator or motor and screw set, or
perhaps a transverse-mounted motor and hinged arm set. Such a
tracking module may also house motion control electronics as well
as a wired or wireless network adapter card allowing its status to
be viewed by a remote computer. The maximum length of tracking
modular subsystem should be limited only by the size/power of the
actuator or motor used.
[0062] To install a solar array using the system described here, an
installer may first select different combinations of frames
(various types and sizes including custom sizes) that best suits
system requirements or needs and then populates those frames with a
like different combination of modular devices of his/her choosing.
Later, a tracking module may be added to the system by plugging it
into the system. Such plug and play installation allows the module
to function seamlessly and harmoniously with the rest of the system
qualifying the system as a true modular system.
[0063] FIG. 7 is a perspective view of a modular solar array 701
according to an embodiment of the present invention. In one
embodiment, modularity of the system may extend beyond the
boundaries of subsystem frames. Array 701 has mechanical linkages
(not illustrated) established between modular subsystems that allow
all of the modular devices such as devices 702 and 703 in the array
to tilt together in unison. Devices 702 are thin film-based while
devices 703 are silicon-based. Other types may also be added into
the installation without departing from the spirit and scope of the
present invention.
[0064] In one embodiment the linkage may be serially connected
(lengthwise as shown below). In another embodiment the linkage may
be parallel (side to side). A combination of the two may also be
implemented without departing from the spirit and scope of the
present invention. A tracking module 704 is provided at one end of
one modular subsystem. Tracking module 704 enables the entire array
to track the sun. Although not specifically illustrated here, the
physical connection among the modular subsystems may be
accomplished in multitudes of ways. For example, in one embodiment
is a metal extension strip that clips on between two adjacent
device connection bars that control tilt angles through cutouts on
end-plates. In another embodiment, electrical and other types of
linkages between modular subsystems may be simultaneously
established.
[0065] It will be apparent to a skilled artisan that the
embodiments described above are exemplary of inventions that may
have greater scope than any of the singular descriptions. There may
be many alterations made in these examples without departing from
the spirit and scope of the invention. For example, different
modular subsystems may have modular solar collecting devices of
different lengths and widths. One or more mounting brackets of many
shapes, sizes and materials may be implemented at various
positions. Tilting of modular arrays can be achieved in a variety
of ways within a frame. Motors or actuators for tracking may be
integrated with modular subsystems. A tracking drive may have an
in-line actuator or AC/DC motor and may also use components such as
gears, screws, levers, pulleys, belts, chains, or cords for power
transmission without departing from the spirit and scope of the
present invention.
Self-Monitoring, Cleaning, and Maintenance
[0066] In addition to the useful embodiments describing a modular
solar array above, the inventor further provides a system and
methods for automated self-monitoring and cleaning and provision of
other maintenance needs for a solar array or for another type of
flat panel array such as glass or other hard and smooth surfaces
not necessarily limiting to modular solar arrays. The present
invention is described in enabling detail using the following
examples, which may include descriptions of more than one
embodiment of the invention. In this specification, a flat panel
shall mean a large flat surface of various dimensions made of
glass, metal, or any other hard and smooth substances. Examples of
flat panels include, but are not limited to solar panels and glass
panels. An array shall mean a cluster of flat panels laid side by
side that is physically separated from other clusters.
Installations such as solar farms and glass facades of buildings
may have any number of arrays greater than or equal to one.
[0067] FIG. 8 is an architectural overview of an integrated network
800 for remote access and maintenance of a system of flat-panel
arrays. Network 800 includes an installation of multiple
photovoltaic flat-panel arrays 805 (a-n). Each array 805 (a-n)
includes a robot 812 and a sensor unit 806. A robot 806 may be a
cleaning robot equipped with delivery hoses for delivering a
cleaning solution to the flat-panels, which are solar panels in
this example. Modular solar devices may be substituted therefor in
one embodiment of the invention. Robot 8121 may also include an
optical component such as a camera eye for enabling a visual
inspection of the surfaces of the flat panels in each array. Each
device array 805 (a-n) is accessible through a switching facility
808.
[0068] The multiple device arrays share a single hardware component
group 810 in this example. Hardware component group 810 includes a
compressor, a number of valves and manifolds, and a water pump. It
is noted that group 810 may include other shared components without
departing from the spirit and scope of the present invention. The
maintenance activity is controlled by a single intelligent
controller 807. All communications to and from each array 805 (a-n)
are routed through switching facility 808 as described above.
Ethernet cables might be used form the single integrated network
800 to monitor, inspect, analyze, and maintain the entire
installation in the optimal operating condition.
[0069] As described above, each array 805 represents a network node
on network 800. Each array may have a network identification and
network address. Each array 805 may include multiple solar panels
813, a dedicated robot 812, and a sensor unit 806. Sensor unit 806
may include a digital surface temperature probe for calibration and
a current/voltage meter for performance metrics (sub-devices not
illustrated). The measurements may be made for the array as a whole
or on a panel-by-panel basis. The sensor unit may be replaced by
certain smart micro-inverters that facilitate real-time data
output.
[0070] Shared hardware 810 may include an air compressor, water
pump and a system of digitally-controlled valves and manifolds that
delivers air and liquid to robots 812 as directed by the controller
via a hardware interface 809. Although not specifically required to
practice the present invention, a firewall-equipped router and
modem 804 may be provided and then connected to the Internet
illustrated herein as Internet cloud 801 to enable an administrator
to monitor and control the network remotely via a computer 802 or a
smart phone. An optional wired/wireless wall-mounted display
console or display monitor 811 may be used locally for similar
purposes.
[0071] Although not required, controller 807 may serve as the brain
for the entire distributed network. It may be equipped with an
embedded single board computer, flash drive for data storage, and
intelligent digital servo-drive for each axis of motion in the
network. Controller 807 may be in constant communication with
individual robots 812, sensors and shared hardware system 810,
sending commands and receiving data. Smart network configuration
software (SW) 814 may be provided on a suitable digital medium to
be executed there from to auto-detect a new robot or axis and
launch a SW configuration wizard. In this example the SW is
implemented on the controller unit 807.
[0072] In one embodiment network 800 includes remote access
capability through the Internet 801. In this case a GUI 803 may be
accessed from a Website (not illustrated) using a remote computing
appliance such as Laptop computer 802. GUI 803 may be provided so
that a user may configure the maintenance of the system remotely
through the Internet or some other digital network accessible to
the World Wide Web (WWW). A suite of applications and widgets (not
illustrated) may be available via Web-based GUI for functions such
as real-time condition/power monitoring, surface inspection, trend
analysis, and other types of user queries and/or inputs.
[0073] In one embodiment of the invention controller 807 may
monitor real-time data from the sensor units 806 to gauge the
health and performance of each panel in each array. The controller
may also splice together strips of thermal images taken from the
imaging module of robot 812 (more detail latter in this
specification), assign a cleanliness index, and make
interpretations of any anomalies or potential issues relative to
each inspected panel. Problems may be identified and possible
remedies suggested by the controller with the aid of the ability to
cross-reference and analyze two sets of real-time data with
previously stored calibration and mined historical data.
[0074] The outcome of the analysis as suggested immediately above
may result in an immediate initiation of an automated response such
as "blow away the leaves on Panel #7" or "wash the entire array").
In one embodiment a report is generated and sent to an
administrator that summarizes the maintenance problems and
suggestions. This option may be pre-determined by the user. Time
stamp and the associated parametric values may be logged and
reported to the administrator for each automated response.
[0075] Cleaning and surface inspections may be scheduled in a
number of different ways. In one embodiment a network administrator
of the networked system may set a default maintenance frequency
using a computer (802), a smart phone, or a wall-mount console 811.
Such a setting may such as a command for cleaning, for example, dry
clean panels two times per week and wet clean the panels once per
month. Many other examples are possible. In one embodiment
controller 807 may devise and implement its own flexible cleaning
schedule on an "as needed" basis. Such a decision may be determined
by real-time sensor data, image data, equipment status, and other
performance metrics, as well as the weather forecast retrieved from
the Internet.
[0076] In an embodiment utilizing intelligent digital servo drives,
the system may be enabled to monitor the state and performance of
each motor. Such information, in conjunction with encoder data and
other sensor data may be used to predict problems that may arise in
robot 812 or that might arise in other hardware before an actual
failure event materializes. Such predictive maintenance capability
could render routine scheduled robot maintenance obsolete.
[0077] FIG. 9 is a perspective view of a modular device array 900
according to an embodiment of the present invention. Modular device
array 900 may be networked with other similar or dissimilar arrays.
In this example the flat panels in array 900 are modular solar
collecting devices. In one embodiment of the present invention,
array 900 includes a robot system 901 including a gantry 902 that
glides on two parallel but opposing tracks 905 situated at opposite
ends of array 900. Gantry 902 serves as a platform supporting a
cleaning module 903 analogous to module 812 described previously.
Gantry 903 also supports an imaging module 904.
[0078] Cleaning module 903 is enabled to track back and forth over
the width of array 900 along the direction of the double arrow
along side gantry 902. Hoses and/or cables (not illustrated) may
enter cleaning module 903 or robot 901 from one end of gantry 902
or they may be tucked underneath the gantry along its entire
length. Gantry 902 may track back and forth over the entire length
of array 900 supported on tracks 905.
[0079] In use the system divides work into manageable portions
corresponding to the functional width of the modules. Cleaning
module or robot 903 may continuously sweep over a strip of
contiguous panels horizontally or vertically without stopping at
the edge of each panel. At the edge of an array, the
cleaning/imaging modules slide along Gantry 902 while the rest of
the robot stays stationery before the sweeping motion resumes in
the reverse direction. The bi-directional movement of the platform
is coordinated with the side-to-side sliding movement of the
modules until the compound motions sweep over the entire surface of
an array. It is important to note herein that the mechanical reach
of the robotic imaging and cleaning modules are such that full
side-to-side travel and full front to rear travel is available to
cover an entire modular device array.
[0080] FIG. 10 is a perspective view of a modular device array 1000
including a lateral transfer system according to another embodiment
of the present invention. Device array 1000 include multiple flat
panels orientated in a lengthwise direction instead of along the
width of the array as previously illustrated above with respect to
FIG. 9. In this example, a robot 1001 includes a gantry 1002 that
has the same or similar width as the flat panels, which are modular
solar collecting devices in this case. This particular
configuration may be useful in situations where the span of the
array is very wide. A lateral transfer system (LTS) 1003 is
provided at one end of array 1000. LTS 1003 consists of a lateral
transfer vehicle (LTV) 1004, a guide channel 1005, and additional
gantry tracks 1006 located under the gaps between panels.
[0081] LTS 1003 enables lateral robot movement along guide channel
1005 perpendicular to the direction of travel over panels to
adjacent rows. The width of gantry 1002 may also be any multiple of
the width of the flat panels. LTV 1004 may have built-in track
extensions (1007) that are designed to line up with the main tracks
to allow robot 1001 to roll on or to roll off of a next array track
without a pause or a transitional step. LTV 1004 may be a
self-propelled vehicle with an onboard motor. LTV 1004 may move
along its own track on a side of guide channel 1005, or may be a
passive vehicle pulled by a fixed motor mounted at the end of the
guide channel. A reel 1008 may be provided and attached to LTV 1004
to ensure automatic alignment and release of supply hoses to the
robot through a feeder/tensioner (not illustrated) mounted on robot
1001. In this example, the cleaning module and camera travels
laterally back and forth over the width of the panels and
lengthwise along the entire array.
[0082] FIG. 11 is a perspective view of a flat panel array 1100
according to another embodiment of the present invention. Array
1100 has very narrow panels and includes a gantry robot 1101 that
does not require any sliding modules. Array 1100 includes a lateral
transfer system (LTS) 1102 located at one end of the array. LTS
1102 enables lateral robot transfer between rows and columns of the
array depending on the orientation of the panels. This
configuration may be suitable for arrays of long and narrow panels
with gaps in between. The networked system may be configured in
multitudes of different manners, depending at least in part on the
size, shape and underlying support structure of the array.
[0083] FIG. 12 is a perspective view of several gantry robot
configurations according to an embodiment of the present invention.
A gantry robot configuration 1200 includes a gantry robot 1201 with
a cleaning module 1203 and an imaging module 1204. Other
illustrated configurations include gantry robot configuration 1208
and gantry robot configuration 1209. All of these configurations
are possible variations of gantry platform 902 described further
above with respect to FIG. 9. Each platform has a payload that
slides side-to-side along the gantry span. Common payloads may
include a cleaning module 1203 and an imaging module 1204.
Configuration 1208 does not include an imaging module.
[0084] Gantry robot 1200 includes flanges 1205 located at the ends
of the gantry. These flanges may be utilized to mount motors and
wheel assemblies (not illustrated). Although the robots may have
sophisticated onboard sensors and data gathering capabilities,
intelligence does not have to reside within the robots in the
networked system, but in a remote controller elsewhere in the
network.
[0085] One of the most critical goals for the networked system may
be a long-term unmanned operational capability. To achieve such a
goal, the cleaning module may or may not use supplies or
consumables such as mopping pads, wiping pads, or cleaning
solutions that have to be manually replaced or replenished at each
array or robot end. At least two separate cleaning modes might be
required to achieve efficient cleaning. For example, a dry cleaning
mode and a wet cleaning mode may be provided. The cleaning module
may also use a special cleaning solution with active enzymes to
breakdown chemical bonds and dissolve "baked-in" bird droppings and
the like.
[0086] In one embodiment of the invention an air knife 1206 is
provided and adapted to lay down a laminar air flow for blowing off
debris from an array. In another embodiment multiple spray nozzles
1207 are provided and adapted for wet cleaning by spraying a
cleaning solution onto the target areas of an array. A combination
of the two may provide non-contact cleaning using an uninterrupted
supply of air and liquid from a central supply system. Air knife
1206 uses a high intensity, uniform sheet of laminar airflow to
blow off liquid or debris. Cleaning module 1203 may deploy
different tools for different cleaning situations. Air knife 1206
may be sufficient for dry cleaning. In one embodiment nozzles 1207
may first spray liquid solution on the target area. Then the liquid
may be allowed to sit or soak for a period of time. Air knife 1206
may be used to blow off the remaining debris after the cleaning
solution has broken it up.
[0087] In one embodiment, cleaning module 1203 may include a
built-in steam generator that ejects stream through the nozzles to
remove oil-based particulates and other sticky particulates. In an
alternate embodiment the cleaning module may utilize a rotating
cleaning head with wiping blades or brushes (not illustrated) in
place of air knife 1206. After spraying and soaking, rotating heads
may have to be lowered to make a physical contact with the panel
surface. Blades or brushes may be made of rubber, plastics or other
durable man-made materials.
[0088] In one embodiment of the present invention, an imaging
module such as module 1204, for example, may play a critical role
in panel inspection, performance monitoring and condition-based
cleaning. For example, it may scan panel surfaces in infrared or
other bands of electromagnetic spectrum to identify anomalies,
check for cleanliness state and to characterize panels. Thermal
images may be highly useful in identifying and diagnosing problems
and may assist the system in solution recommendation. The scanned
strips of images may be sent to controller for analysis and
storage.
[0089] It will be apparent to the skilled artisan that the
apparatus for cleaning and inspecting panel surfaces termed a robot
cleaning module or payload may vary in length, shape, and
capability without departing from the spirit and scope of the
present invention. For example, cleaning module 1203 may be annular
or rectangular. Gantry 1202 may be rectangular or annular. Many
differing configurations are possible. The key aspect is the
capability of the robotic component to inspect, report findings,
and then to clean the flat panel surfaces accordingly.
[0090] FIG. 13 is a cutaway view of a multi track robot 1300
according to an embodiment of the present invention. Multi-track
robot 1300 includes a gantry platform 1302. Payloads provided in
this example include a cleaning module 1303 with cleaning nozzles
and or an air knife, and an imaging module 1304. The wheels of
gantry platform 1302 run on tracks 1313 situated below panels 1314.
In this embodiment the width of gantry platform 1302 matches the
spacing between each row or column of supported flat panels
1316.
[0091] Flat panels 1314 are supported by support beams 1315 and by
cross beams 1316 situated underneath the panels and comprising the
framing structure for the array. In this embodiment robot 1300 is
suitable for modular solar arrays. In one embodiment robot 1300 is
driven along track 1313 by a main motor 1305 attached to a pinion
gear 1306. Pinion gear 1306 together with guide wheels on the
opposite side of the track and their housing, forms a driving wheel
assembly 1307. An auxiliary motor 1308 is provided in this example
and is adapted to power a linear drive mechanism 1309. Linear drive
1309 slides the gantry payloads along the span of the gantry. On
the left leg of gantry 1300, a non-driving wheel assembly 1310 is
provided and is adapted to guide the robot along the track.
[0092] The wheel assemblies are mounted perpendicularly to the
gantry legs to fit in the limited space between the panels and the
cross-beams. The entire drive mechanism is hidden under the panels.
A feeder/tensioner 1311 is provided and adapted to assist robot
pull hoses and/or cables 1312 from a reel underneath each array. A
hose guide 1317 aids in changing the direction of the hoses.
[0093] FIG. 14 is a cutaway view of a multi-track robot 1400
according to another embodiment of the present invention. Robot
1400 includes a cleaning module 1403 and a gantry platform 1402. In
one embodiment gantry robot 1400 does not include gantry legs.
Instead the wheels and motors thereof are mounted on flanges
extending perpendicularly from the lengthy of the gantry. The
wheels are positioned to run on the inside of the channels
extending through the system at either end of each array. The
cleaning module and a feeder tensioner for hose/cable assistance
share the same axis. This present configuration is useful for a
building having long vertical glass flat panels, for example.
[0094] FIG. 15 is a perspective view of optional hose or cable
feeder/tensioner assemblies for use in cleaning operations
according to embodiments of the present invention. A feeder/tension
assembly 1501 is provided and is illustrated as an optional
assembly for supporting hose/cable management during a cleaning
operation.
[0095] Assembly 1501 may be used for under-the-panel routing, where
hoses or cables are routed from a reel 1502 attached to the system,
through a hose guide 1503, and then through a feeder/tensioner 1504
installed on one of the gantry legs. The routed hoses enter the
cleaning module 1505 on one of the gantry legs, before entering a
cleaning module 1505.
[0096] A feeder/tension assembly 1506 is provided and is
illustrated as an optional assembly for supporting hose/cable
management during a cleaning operation. Assembly 1506 illustrated
on the right hand side as viewed may be suited for over-the-panel
routing.
Hose or cable travel from a reel 1507 to a swiveling
feeder/tensioner 1508, then directed to a cleaning module 1509.
Swiveling feeder/tensioner assembly 1508 may sit on its own track
at the top of an array allowing a robot to simultaneously tow and
draw hoses from it over the flat panels.
[0097] In a preferred use embodiment, as a robot scans and or
cleans a flat panel surface of an array, a spring-loaded rotary
hose feeder/tensioner with an auxiliary hose reel such as those
illustrated and described in this example, draws hoses/cables from
a main reel and maintains them in uniform tension while dampening
stress and time lag as it overcomes inertia. A right amount of
tension may prevent snag, tangle or kink of the hoses. A built-in
tension sensor (not illustrated) may be provided trigger an
emergency stop if the tension on hoses and/or cabling exceeds a
preset limit. An external hose guide orientates hoses toward the
feeder/tensioner at all times. It is noted herein that tracks may
be of various shapes and sizes. Tracks may be manufactured of any
one of a number of hard man-made or synthetic materials such as
steel, aluminum, or plastics, depending in part on cost and
durability. Tracks may be laid under, between, or on the sides of
flat panels.
[0098] FIG. 16 is a top view of a robot tracking on a hybrid
tracking system 1600 according to an embodiment of the present
invention. Hybrid tracking system 1600 includes a deviation
tolerant non-driving wheels assembly 1604 and a driving anti-torque
wheel assembly 1609. Annular inset 1601 illustrates a double-sided
hybrid track made of a gear rack sandwiched between two flat
plates. This track embodiment includes a toothed rack side 1602 and
a flat rail side 1603. The particular configuration allows for a
pinion gear such as pinion gear 1611 on one side and wheels/rollers
1612 on the other. The hybrid tracks are mounted here on their
sides directly on the cross-beams that run below panel support
beams.
[0099] Because the robots ride on rigid tracks, it is important
that the tracks are substantially parallel with spacing sufficient
to prevent the robot's wheels from getting jammed between them.
However, when the tracks are installed in the field, some
deviations (.theta.) should be expected. One of the methods to
compensate for the lack of precision and make the drive system more
robust may be to make at least one of the two wheel assemblies
"deviation-tolerant" such as assembly 1604 above.
[0100] On the non-driving side, the entire wheel assembly 1604 is
mounted on the flange of the gantry 1605. The assembly includes two
articulated links 1606. A coil spring (not illustrated) occupies
the wheel housing along a common pivot axis 1607. The torsion of
the spring pushes two wheels/rollers 1608 against the flat side of
the track. When narrowing of the track occurs, the housing pivots
and the angle between the links also narrow and vice versa. Such
scissor-like action maintains constant traction on the wheels.
[0101] On the driving side, anti-torque driving wheel assembly 1609
includes a motor 1610. Motor 1610 is adapted to turn pinion gear
1611 against the rack side of the track. Twin wheels/rollers 1612
make intimate contact with the track from the rail side and
counter-balance the momentum produced by motor 1610. A
triple-pronged wheel housing 1613 is provided that bounds pinion
gear 1611, motor 1610, and wheels 1612 together on a flange 1614
extending from one of the gantry legs. The robot tracks in the
direction of
[0102] FIG. 17 is a top view of a robot tracking on a hybrid
tracking system 1700 according to another embodiment of the present
invention. In this example a left wheel assembly 1701 is provided
as a non-driving wheel assembly. Wheel assembly 1701 includes a
boomerang-shaped wheel housing 1702. Wheel housing 1702 has a pivot
point at center 1703. Wheel housing 1702 pivots at center point
1703 and may move freely along slot 1704. Slot 1704 is cut into
flange 1712 extending out from one of the gantry legs.
[0103] In use, a tension/compression spring (not illustrated)
installed between wheel housing 1702 and the flange pushes the
housing and its twin wheels/rollers 1705 outward against the flat
side of the track, continuously adjusting to narrowing or widening
of the track spacing in a deviant tolerant manner as described
further above.
[0104] On a right wheel assembly 1706, a boomerang shaped wheel
housing 1707 holds one large pinion gear 1710 and two small pinion
gears 1711 together in mounted position on flange 1708 extending
from the gantry. A motor 1709 mounted on flange 1708 turns large
pinion gear 1710 to move the robot relative to the rack side of the
track in the direction of the directional arrow.
[0105] FIG. 18 is a top view of a robot tracking on a tracking
system 1800 according to a further embodiment of the present
invention. In this embodiment the hybrid tracks utilized in the
previous examples are replaced by a C-shaped channel 1801 as shown
in the annular inset taken from or expanded from section line 1801.
A driving wheel assembly 1806 is provided and includes two small
wheels 1807, and a large wheel 1809 held together in mounted
position by a boomerang-shaped wheel housing 1808 and a flange
1811.
[0106] A non-driving wheel assembly 1802 is provided and includes a
butterfly-shaped wheel housing 1803. Wheel housing 1803 has two
links joined and pivoted at the center where it mounts to flange
1804. A torsion spring (not illustrated) installed between them
pushes two of the wheels 1805 against the inside wall of the
channel and the other two wheels 1805 against the opposite wall of
the channel. The asymmetric shape of the links allows the wheel
assembly to expand and fold to match the width of the channel while
avoiding any contact between them.
[0107] Driving wheel assembly 1806 works in a manner similar to the
non-driving wheel assembly except that it has three wheels instead
of four wheels. The torsion spring on the common axis pushes twin
wheels/rollers 1807 at the end of an articulated housing 1808
toward the inner wall of the C-shaped channel while the larger main
wheel 1809 at the center pushes outward as well. This particular
wheel assembly configuration may also be able to adjust itself to
different channel widths, but in order to resist the moment
produced by a motor 1810 mounted on flange 1811, the torsion spring
may have to be fairly stiff. The motor urges the robot along the
channel in the direction of the arrow. To remove either wheel
assembly 1802 or 1806 from the respective channel, it has to be
folded using a tool and a pin inserted through a hole (not
illustrated) to lock the position before removal.
[0108] It will be apparent to a skilled artisan that the
embodiments described above are exemplary of inventions that may
have greater scope than any of the singular descriptions. There may
be many alterations made in these examples without departing from
the spirit and scope of the invention. For example, each robot may
have an on-board controller. Robots of many different shape, sizes
and configurations may be made of many different materials.
Different versions of cleaning modules may have varying widths and
effective coverage areas that may alter the number of passes and
sweep sequence required to cover a whole panel or array. Certain
embodiments of cleaning modules may utilize other contact and
non-contact cleaning methods such as acoustic technologies. Imaging
modules may adapt an alternate surface scanning technologies such
as laser or electromagnetic bandwidths other than infrared. Sensor
modules and other additional modules may be added on the payload
list without departing from the spirit and scope of the invention.
Different configurations of wheels may run on tracks of many
shapes, sizes and materials. Air and liquid supplies and delivery
systems may be installed at each array instead of at a central
location. There are many possibilities.
Retrograde Tracking for Solar Panels
[0109] In this specification a solar device refers to a discrete
solar energy collection component. A solar device may be a solar
photovoltaic (PV) cell, a chemical coated/treated substrate or
heat-absorbing surface and may use crystalline silicon PV, thin
film, concentrating solar, solar thermal or any other solar
technology. The terms solar panel (a.k.a. solar module) is defined
as a collection of one or more solar devices that are mounted
together on a common base with built-in conduits for transferring
energy to a larger energy storing/transmitting system or network.
Solar array means a group or cluster of solar panels. Tracking
panel, tracking array or more generic tracking unit refers to one
or more of solar panels moving in unison on a common tilting
plane.
[0110] FIG. 19 is a logical block diagram illustrating angle of
incidence (AOI) of the sun against a solar array. Regardless of the
technology used, solar panels are most efficient when the angle of
incident (AOI) is minimized as is illustrated herein. That is to
say when the rays of the sun come in at an angle that is normal to
the energy absorbing/converting surface then the angle is
minimized. The general rule is that the larger the deviation from
zero AOI, the smaller the amount of energy is available to the
solar collection process. Therefore, it is a desire that solar
tracking systems have minimal AOI as long as possible to maximize
energy conversion efficiency.
[0111] Further to the above, commercial tracking systems may be
either single axis or double axes systems. In a single axis system,
panels face the sun and follow it as it rises from the east and
sets in the west. This axis (FIG. 19) running north-south is often
referred to as the primary axis. In addition to this daily
east-west motion, a double-axes tracking system has a secondary
axis that is used to adjust its tilt angle over a one year cycle to
adapt to the seasonal variations of the sun resulting in higher
elevation in the summer and lower in the winter.
[0112] FIG. 20 is a block diagram illustrating an angular range of
motion (AROM) for a solar panel according to an embodiment of the
present invention. Tracking systems have angular range of motion
(AROM). In this example, AROM equals to two times .theta.
representing the tilt limit of the panel in either direction
measured from the horizontal plane (broken rectangular boundary) in
the east-west direction. Cross-shading, a term commonly used in
solar jargon, refers to a condition that causes systemic shading of
adjacent tracking units. It usually occurs at low sun angles due to
insufficient inter-array spacing.
[0113] A typical tracking system known in the art uses synchronous
motion (SM) where the panels always face the sun and tilt at the
same constant rate in sync with the sun. In contrast to this
standard method, the term counter-synchronous motion (CSM) coined
by the inventor refers to a unique tilt motion activated in the
opposite direction relative to the sun either toward or away from
the sun. The angular trajectory is still, however, dependant on the
position of the sun during tracking.
[0114] FIG. 21 is an elevation view of a modular device
illustrating inter-array spacing or separation. The width of
tracking unit is defined as the width seen along the direction of
the primary axis. The distance between adjacent primary axes
defines inter-array spacing or separation as shown in FIG. 21.
Limitations of Conventional Tracking Systems
[0115] It is a well established fact that tracking solar arrays can
produce substantially more energy (watts/panel) compared to fixed
arrays of the same type and capacity. This difference is most
pronounced for those using crystalline silicon PV technologies,
where a single-axis tracking systems could add up to 30% more
energy. However, there is a penalty involved. When one side of
array is raised at low sun angles, the arrays cast larger shadows
and require greater separation compared to their fixed
counterparts. Again, this penalty is costliest for crystalline PV
systems because relatively small shading may result in a
disproportionate power reduction.
[0116] The overriding objective of a typical commercial rooftop
installation is to achieve the highest energy density within a
confined rooftop space. Obviously, the extra spacing lowers
installation density in terms of the number of panels/unit of area.
Because of the space, weight and other constraints, the
fast-growing commercial segment has been largely bypassing the
conventional tracking option.
[0117] Today, practically all rooftop-based commercial solar
installations are fixed and most of the tracking systems can be
found in large utility-scale ground-based installations in remote
areas where space is relatively inexpensive and abundantly
available. The tracking method described below addresses these
shortcomings and may enable practical rooftop-based tracking
solutions in the future.
Retrograde Tracking
[0118] Unlike the conventional tracking systems that track the sun
from horizon to horizon exclusively using synchronous motion (SM),
retrograde tracking is a hybrid strategy incorporating a second
element, a variable speed counter synchronous motion (CSM), in a
seamless manner.
[0119] FIG. 22 is a chart illustrating retrograde tracking
according to an embodiment of the present invention. In retrograde
tracking, SM is used when the sun is within the system AROM (center
region in FIG. 22) and CSM is used when the sun is outside of it
(regions adjacent to center region in FIG. 22). Retrograde tracking
requires a single-axis east-west retrograde motion, but a secondary
axis may be combined to provide seasonal tilt adjustments in the
north-south direction.
[0120] Successful implementation of retrograde tracking requires a
proper inter-panel/array spacing that is a function of the
panel/array width and their AROM. In an optimized embodiment, this
is the minimum distance at which no cross-shading is possible when
the sun is within the AROM. This arrangement creates an
interference-free zone for SM (the center wedge).
[0121] Over the 12-hour span, the vector normal to the panel
surface (dashed-line) sweeps the center AROM region twice (swings
right, left, and then back to right) without crossing into the
adjacent regions. That is to say both SM and CSM tracking take
place within this center region. This pendulum-like motion is
traced using a timeline at the top of the chart. The numbers on top
of the chart represent hours in a 24-hour time period. The order of
steps is as follows: [0122] 1) Panels are in the horizontal standby
position as the sun rises from the east. [0123] 2) Panels gradually
tilt east toward the sun until it reaches their tilt limit. (CSM
tracking) [0124] 3) When the tilt limit is reached at the border,
AOI is zero and panels reverse direction and start tilting in sync
with the sun. (SM tracking) [0125] 4) When the tilt limit is
reached again on the opposite side, the panels decouple from the
sun and reverse direction once again to move away from the sun.
(CSM Tracking) [0126] 5) Panels eventually return to the horizontal
standby position.
[0127] The following several examples illustrate SM and CSM
tracking and the tracking functions illustrated in FIGS. 23 through
28 and Table 1 assume 90 degree AROM, sunrise at 6:00, sunset at
18:00 (equinox) and tracking conditions that allow 12 hours of
continuous tracking Panel angles in Table 1 below are measured
relative to the horizontal plane in each example. At the start of
tracking, the time is 6:00, the sun angle is 0, and the panel angle
is 0. The panel remains in the horizontal position as the sun
begins to rise.
[0128] Referring now to FIG. 23, the time is 7:00, the sun angle on
the panels is 15 degrees, the panel angle is 7 degrees, and the
panels are turning slowly and simultaneously toward the sun (CSM
tracking). Proper spacing prevents shadow cast onto the farthest
panel from the sun. Referring now to FIG. 24, the time is 8:00, the
sun angle on the panels is 30 degrees, the panel angle is 16
degrees, the tracking process picks up speed as the panels surfaces
face the sun. Referring now to FIG. 25, the time is 9:00, the sun
angle on the panels is 45 degrees, and the panel angle is also 45
degrees. The position is referred to as normal to the sun and the
position minimizes the AOI. At this point the panels stop and begin
to reverse direction (SM tracking). Referring now to FIG. 26, the
time is 12:00, the sun angle on the panels is 90 degrees, and the
angle of the panels is 0 representing the half way mark of the 12
hour tracking sequence. Referring now to FIG. 27, the time is
15:00, the sun angle on the panels is 135 degrees, and angle of the
panels is -45 degrees.
[0129] At this point the CSM returns with another reversal in
direction of movement. The remainder of table 1 describes the
return movement back to an idle horizontal position sampled at time
16:00, 17:00, and finally at 18:00. The sampled angles of the sun
on the panels is 150 degrees, 165 degrees, and 180 degrees
respectively. The panel angles on the sampled points are -16
degrees, -7 degrees, and 0 degrees where the panels have returned
to a horizontal position to wait for the next tracking sequence at
6:00 the following day.
TABLE-US-00001 SUN PANEL TIME ANGLE ANGLE* EVENTS 6:00 0 0 As the
sun starts ascent, the panel is in the horizontal starting
position. 7:00 15 7 Panels turning toward the sun (CSM) slowly to
avoid shading. (FIG. 5) 8:00 30 16 Panels pick up speed at it nears
the encounter with the sun (FIG. 6) 9:00 45 45 When panel surfaces
become 12:00 90 0 normal to the sun at 9:00 (FIG. 7), 15:00 135 -45
they reverse direction and SM begins. The half-way point is reached
at 12:00 (FIG. 8). At 15:00 (FIG. 9), CSM returns with another
reversal. 16:00 150 -16 Panels are moving rapidly away from the sun
to escape cross- shading. 17:00 165 -7 The speed has slowed
substantially as they near the "home" position. 18:00 180 0 Panels
are back in the horizontal position and ready for the next day.
[0130] Retrograde tracking using hybrid SM/CSM can be achieved with
relatively small AROM and inter-panel/inter-array spacing compared
to the conventional full-time SM tracking systems. These attributes
are advantageous wherever the tracking units have to be placed in a
relatively close proximity of each other, especially for, but not
limited to rooftops. A method for tracking solar panels can be
characterized by beginning a tracking cycle substantially at
sunrise with adjacent tilting panels all horizontal; tilting the
adjacent panels in unison in a first angular direction toward the
rising sun at a tilt rate that just avoids shading of adjacent
panels; reversing direction of panel tilt at a point that the
panels reach either a maximum tilt limited by mechanical design, or
the panel surfaces are orthogonal to the rising sun; tilting the
adjacent panels in a second angular direction, following movement
of the sun and keeping the surface of the panels at right angles to
the sun's position, until a point is reached that shadowing is
imminent from the angle of the setting sun and then reversing
direction of panel tilt again to the first angular direction,
adjusting tilt as the sun sets to avoid shading until the panels
are again horizontal. Small spacing requirement is also conducive
for small-scale light-weight systems that can track at the device,
panel/module level, in addition to larger array/cluster level. The
tracking system may minimize shading on adjacent panels in a
pre-programmed way such that the amount of shading is pre-known and
controlled by varying the tilt angle and speed of tilt. In one
embodiment the shading varies according to the tilt angle.
[0131] One disadvantage of the retrograde tracking may be that the
lower energy generation efficiency of CSM tracking relative to SM
tracking. However, the actual difference between full-time SM
tracking and retrograde tracking should be relatively minor due to
the fact that CSM portion takes place during early-morning and late
afternoon hours when the solar radiation is weak. The higher energy
density of the retrograde tracking method may more than compensate
for the slightly lower overall efficiency.
[0132] The ultimate choice of the tracking system may come down to
the objective of individual installations. If it is to simply
maximize energy production (total watts/installation) with no space
constraint, a full-time SM tracking system should be employed.
However, if the goal is to attain the highest energy producing
capacity for a given installation space (watts/m2 or watts/ft2),
retrograde tracking may be a better option. Development of a
low-profile space-saving retrograde tracking hardware system may
usher in a new era of rooftop-based tracking PV systems in the
future.
Modular Architecture
[0133] The inventor provides a unique low-profile modular
architecture for rooftop and commercial solar panel arrays.
[0134] FIG. 28 is a perspective view illustrating two array
configuration options according to an embodiment of the present
invention. A solar panel array 2800 comprises adjacent modular
solar collection devices 2802 installed in a linkable frame
sub-system 2803. Devices 2802 are arrayed in a row and tilt along
the length of the row in either direction. Array 2800 includes
adjustable frame legs 2804 for adjusting the fixed angle of tilt to
the slope of the roof. The individual solar devices or panels 2802
are linked to a tilting mechanism that provides SM and CSM tracking
for all of the devices in unison.
[0135] A solar panel array 2801 comprises adjacent modular solar
collection devices 2805 installed in a linkable frame sub-system
2806. Modular devices 2805 are arrayed in adjacent columns, each 4
panels or devices deep the devices in each column tilting along the
height of the column in either direction.
[0136] FIG. 29 is a perspective view of a single sub-frame section
of linkable frame component 2806 of FIG. 28. All of the modular
devices are linkable through tilt mechanism to enable tracking in
unison with each modular device of a linked sub-frame tilting in
unison in the same direction.
[0137] FIG. 30 is a partial view of a frame member 3000 according
to an embodiment of the present invention. Frame member 3000
includes a plurality of tilt mechanisms 3002 installed on a
tilt-bar (one shown). Each tilt mechanism supports a single modular
solar collection device. A tilt bar linking clip 3001 is provided
in this example to enable tilt-bar linking through multiple
adjacent-system frames. In this way all of the modular devices in a
device array can be linked to tilt in unison during SM and CSM
tracking of the sun. A low-cost plain bearing is provided behind
the linking clip to reduce tilt bar friction through the frame wall
as it moves back and forth during tracking. The internal structure
3003 of frame member 3000 is honeycombed to increase strength while
maintaining a light weight.
[0138] FIG. 31 is a perspective view of frame member 3000 of FIG.
30 showing outer skin and multiple tilt mechanisms. Frame member
3000 is a right side frame member. A left side frame member would
support the other side of installed modular solar devices. Multiple
tilt mechanisms 3002 are visible on the inside wall of the frame.
The outer skin covers the internal honeycombed structure.
[0139] FIG. 32 is a block diagram illustrating basic tracking
module components of a tracking module 3200. Tracking module 3200
is adapted to enable the system to perform both SM and CSM tracking
as described previously. One tracking module may control tracking
for multiple linked solar device arrays. Tracking module 3200
includes a rack and pinion 3201 installed on a linear guide. The
rack slides on the linear guide and converts torque into precision
linear motion.
[0140] Module 3200 includes one or more magnetic limit sensors
3200. Sensors 3200 enable calibration and validation of motor
position in absence of an encoder. Tracking module 3200 includes a
power supply 3203 that is adapted to store electricity collected
from the PV modules in capacitors and for charging the battery.
Tracking module 3200 includes a motor and reduction gear 3204
comprising a low cost and reliable stepper motor and a planetary
gear head that is adapted to reduce speed and to boost torque.
Tracking module 3200 includes a logic/controller 3205 which
comprises the brain of the system and communication center for the
system.
[0141] The tracking module may in one embodiment include USB ports
for enabling diagnostic access to the device. The tracking module
includes a battery service hatch for replacing rechargeable
batteries, which may be a small swap of small lithium batteries
(about once every 3 years.)
[0142] FIG. 33 is a partial view of a frame member 3300 of the
modular solar collecting system of the present invention. Frame
member 3300 has a low-set cross member. The frame sides that are
parallel to PV panels are lowered and inside edges are rounded.
This effectively increases the level of shade avoidance while
tracking by the reduction in the minimum gap between the frame wall
and first/last PV panel.
[0143] Frame member 3300 includes a push-on frame locking clip 3302
adapted to restrain movement between adjacent frames. In one
embodiment, a bolt can be inserted through the clip for
reinforcement. Frame member 3200 has overlapping joints 3304
including adjacent walls that fit inside channels and guides. The
system also includes tight low-tolerance fit reinforced by studs.
Outer coverings in the frame conceal a honeycombed internal
structure that provides reinforcing strength but remains relatively
light weight.
[0144] It will be apparent to one with skill in the art that the
modular solar system of the invention may be provided using some or
all of the mentioned features and components without departing from
the spirit and scope of the present invention. It will also be
apparent to the skilled artisan that the embodiments described
above are specific examples of a single broader invention which may
have greater scope than any of the singular descriptions taught.
There may be many alterations made in the descriptions without
departing from the spirit and scope of the present invention.
* * * * *