Note: Descriptions are shown in the official language in which they were submitted.
CA 02804887 2013-01-09
WO 2012/009470 PCT/US2011/043905
ROBOTIC HELIOSTAT SYSTEM AND METHOD OF OPERATION
INVENTORS
SALOMON TRUJILLO,
DANIEL FUKUBA,
THOMAS CURRIER,
WASIQ BOKHARI
RELATED APPLICATIONS
[0001] This application claims priority from U.S. provisional application
number
61/364,729 filed on July 15, 2010, and U.S. provisional application number
61/419,685 filed
on December 3, 2010 which are all incorporated by reference herein in their
entirety. This
application is related to US utility application 13/118,274 which is
incorporated by reference
herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to solar tracking and calibration
devices, and in
particular tracking systems for photovoltaic, concentrated photovoltaic, and
concentrated
solar thermal systems that require constant repositioning to maintain
alignment with the sun.
BACKGROUND OF THE INVENTION
[0003] In an attempt to reduce the price of solar energy, many developments
have been
made with respect to lowering the cost of precisely repositioning and
calibrating a surface
with two degrees of freedom. In concentrated solar thermal systems, heliostat
arrays utilize
dual axis repositioning mechanisms to redirect sunlight to a central tower by
making the
normal vector of the heliostat mirror bisect the angle between the current sun
position and the
target. Heat generated from the central tower can then be used to create steam
for industrial
applications or electricity for the utility grid.
[0004] Concentrated photovoltaic (CPV) systems take advantage of dual axis
mechanisms in order to achieve a position where the vector normal to the CPV
surface is
coincident with the solar position vector. When the CPV surface is aligned to
the sun, internal
optics are able to concentrate sunlight to a small, high efficiency
photovoltaic cell.
[0005] Dual axis positioning systems also enable flat plate photovoltaic (PV)
systems to
produce more power through solar tracking. Compared to fixed tilt systems,
dual axis PV
systems produce 35-40% more energy on an annualized basis. While this increase
in energy
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production may seem attractive, current technology marginalizes the value of
biaxial solar
tracking by increasing total system capital and maintenance costs by 40-50%.
[0006] Traditional solutions to the problem of controlling and calibrating an
individual
surface fall into one of three main categories: active individual actuation,
module or mirror
ganging, and passive control. In the active individual actuation model, each
dual axis system
requires two motors, a microprocessor, a backup power supply, field wiring,
and an
electronic system to control and calibrate each surface. Moreover, all
components must carry
a 20+ year lifetime and the system needs to be sealed from the harsh
installation environment.
In an attempt to spread out the fixed cost of controlling an individual
surface, conventional
engineers' thinking within the individual actuation paradigm are building 150
square meter
(m^2) heliostats and 225 square meter PV/CPV trackers. While control costs are
reduced at
this size, large trackers suffer from increased steel, foundational, and
installation
requirements.
[0007] Another approach attempts to solve the fixed controls cost problem by
ganging
together multiple surfaces with a cable or mechanical linkage. While this
effectively spreads
out motor actuation costs, it places strict requirements on land grading,
greatly complicates
the installation process, and incurs a larger steel cost due to the necessary
stiffness of the
mechanical linkages. Due to constant ground settling and imperfections in
manufacturing and
installation, heliostat and CPV systems require individual adjustments that
increase system
complexity and maintenance cost.
[0008] Passive systems utilizing hydraulic fluids, bimetallic strips, or bio-
inspired
materials to track the sun are limited to flat plate photovoltaic applications
and underperform
when compared to individually actuated or ganged systems. Moreover, these
systems are
unable to execute backtracking algorithms that optimize solar fields for
energy yield and
ground coverage ratio.
SUMMARY
[0009] A robotic controller for controlling a position of multiple solar
surfaces in
response to movement of multiple solar surface adjustment wheels, each solar
surface having
a corresponding solar surface adjustment wheel, the robotic controller
positioned on a track,
the robotic controller including a processing unit, a location determining
unit,
communicatively coupled to the processing unit, for determining a position of
the robotic
controller, a drive system, for moving the robotic controller along the track
in response to
instructions from the processing unit, an adjustment determining system for
determining first
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adjustment parameters for a first solar surface adjustment wheel of the
multiple solar surface
adjustment wheels; and an engagement system for adjusting the first solar
surface adjustment
wheel based upon the first adjustment parameters.
[0010] Particular embodiments and applications of the present invention are
illustrated
and described herein, it is to be understood that the invention is not limited
to the precise
construction and components disclosed herein and that various modifications,
changes, and
variations may be made in the arrangement, operation, and details of the
methods and
apparatuses of the present invention without departing from the spirit and
scope of the
invention which is set forth in the claims.
[0011] In an embodiment the invention can be used in conjunction with a
heliostat or
solar tracker that has its microprocessor, azimuth drive, elevation drive,
central control
system, and wiring removed. The elimination of these components allows for
extreme cost
reduction over conventional systems, and creates a fourth actuation paradigm:
passive with
active robotic control. In this model, a single robotic controller assumes the
functional duties
of calibrating and adjusting two or more solar surfaces in 3D space.
[0012] In a second embodiment of the present invention a robotic controller
can move
between passive solar surfaces and accurately control the rotation of one or
more adjustment
wheels near aforementioned surface. These adjustment wheels may be connected
to a rigid or
flexible shaft that could be routed to a gear train, lead screw assembly, or
directly to the solar
surface. The gear train, lead screw assembly, or direct drive system
transforms rotational
input motion into movement of the solar surface. If the gear train, lead screw
assembly, or
direct drive system is back drivable, additional adjustment wheels may be used
to actuate
braking mechanisms. The robotic controller is able to reposition a solar
surface in one or two
axes through control of one or more adjustment wheels and therefore replaces
100+ sets of
wiring, motors, central controllers, and calibration sensors. It also
eliminates the core
engineering assumption¨a high, relatively fixed control cost per surface¨that
drives the
development of large heliostats and solar trackers.
[0013] As an individual robot must endure 5 to 8 million adjustment cycles per
year, the
ideal adjustment interface will not use contact to control the position of the
adjustment wheel.
In a third embodiment, the invention can utilize a magnetic or electromagnetic
interface to
control the rotation of the adjustment wheels. If an axial flux motor
mechanism is utilized,
the robotic controller's adjustment wheel interface may contain no moving
parts.
[0014] In a fourth embodiment the robotic controller can sense the position of
an
adjustment wheel before, during, and after adjustment. This may be achieved
through the use
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of Hall effect sensors on the robotic controller and a distinct magnet or
piece of metal on the
adjustment wheel. Methods of metal detection include, but are not limited to:
Very Low
Frequency (VLF), Pulse Induction (PI), and Beat-Frequency Oscillation (BFO).
The robot
may also use optical, electromagnetic, or physical marking systems and sensing
methods to
determine the instantaneous position of an adjustment wheel. This interface
may also be used
to detect an individual solar surface station in order to reduce the
complexity of an individual
robot's station sensing mechanism.
[0015] In a fifth embodiment, the robotic controller is optimized for rapid
adjustment of
solar surfaces. The robotic adjustor can quickly analyze: 1) the robotic
controller's location
in 3D space, 2) Its relation to a solar surface in 3D space, 3) The current
sun position based
on time of day and location, and 4) the desired pointing position. Once these
four variables
are known, the robotic controller may calculate the necessary amount of
adjustment for an
individual solar surface. For PV and CPV applications, the solar surface may
be pointed
directly toward the sun or at an optimal angle as defined by backtracking
control algorithms.
In addition, for PV applications, the robot may utilize existing methods that
rely on the
location, date and time information to determine the position of the sun and
point the PV
panel in an open loop fashion. Heliostat power tower systems will require the
solar surface to
bisect an angle between the sun and a central target. As the solar surfaces
will not be
constantly updated, the optimal position in some applications will place the
surface such that
it will be in its best orientation midway between adjustments. For example, if
26 degrees is
the optimal elevation angle at the time of the adjustment, and 27 degrees will
be the new
maximum at the time of the subsequent adjustment, a robotic controller may
place the surface
at 26.5 degrees tilt.
[0016] Once calculated, the robotic controller may use an onboard adjustment
interface to
control the position of a solar surface. The final step in the robotic
controller's process is to
analyze the distance to an adjacent adjustment station, and utilize an onboard
or external
drive mechanism to reposition itself for a subsequent adjustment.
[0017] In a sixth embodiment two, three, or more grades of robotic controllers
can be
used to cost effectively reposition a field of solar surfaces. The top and
most expensive grade
robotic controller may include all mechanisms necessary to precisely calibrate
and adjust a
field of solar surfaces. The mid grade robotic controller may contain all
mechanisms needed
to reposition a solar surface and would be built to withstand ten or more
years of field
operation. The low-grade robotic controller may have the minimum number of
functional
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components to adjust a solar surface quickly, and may be engineered for low
cost over
longevity.
[0018] The ideal passively actuated field may utilize one top grade robotic
controller for
initial calibration and re-calibration purposes. Mid grade robotic controllers
may be used for
normal operation and would adjust the solar surfaces based on inputs from the
top grade
robotic controller. Low-grade robotic controllers may be used in emergency
situations and
would enable rapid and low cost emergency defocus and/or wind stow.
[0019] In a seventh embodiment a field of robotic controllers to communicate
with each
other and/or a central controller system via a wireless network, direct liffl(
system, external
switch, or by storing data near individual solar surfaces or groups of solar
surfaces.
[0020] In an eighth embodiment, the robotic controller includes multiple
adjustment
wheel interfaces so that a multiplicity of solar surfaces can be adjusted
simultaneously.
[0021] In a ninth embodiment the robotic controller can control the position
of an
individual adjustment wheel or wheels without stopping. This may be achieved
using a gear
rack and pinion system that uses contact, magnetism, and/or electromagnetism
to rotate an
adjustment wheel.
[0022] In a tenth embodiment the robotic controller can move between stations
through a
hermetically sealed tube to prevent large object, water, and dust ingress. It
also may be
desirable for the robotic controller to be hermetically sealed in order to add
another layer of
ingress redundancy.
[0023] In an eleventh embodiment the robot transport tube can be routed such
that the
robotic controllers can be easily returned to a central location.
[0024] In a twelfth embodiment two or more robotic controllers can adjust one
group of
solar surfaces. This enables the solar surface repositioning system to be
redundant in the case
of a single robotic failure.
[0025] In a thirteenth embodiment the robotic controller can include an
onboard climate
control system that utilizes heat sinks, active cooling/heating systems, and
moisture control
mechanisms to maintain a constant temperature and environment for internal
components.
This system is particularly useful in extending the effective life of various
onboard energy
storage mechanisms.
[0026] In a fourteenth embodiment the robotic controller can be charged
wirelessly. If
electromagnetic coils are used to control the rotation of the adjustment
wheels, this interface
could be reused to charge an onboard energy storage system inductively.
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[0027] In a fifteenth embodiment a robotic controller can include a diagnostic
system that
is able to relay the health of onboard components to other robotic controllers
and/or a central
control system. This diagnostic system may communicate a regular and periodic
message
back to the remote operator or be accessed as needed. This system may also be
used for in-
field quality assurance of passive trackers or heliostats as the robot may
actively measure the
amount of torque or energy needed to control the position of a solar surface's
adjustment
wheel. This system may also be used for defect detection in the case that a
solar surface's
adjustment wheel cannot be rotated. The robotic controller may also utilize
onboard sensors
to determine if the robot transport tube has any faults.
[0028] In a sixteenth embodiment faulty solar surfaces for PV and CPV
applications can
be detected. In this model, the robotic controller may communicate with a
central power
collection system to determine the immediate output from a field of solar
surfaces. If a single
solar surface is rotated away from the sun, and the central power collection
system detects no
change in power output, the robotic controller may deem the solar surface to
be defective. It
may also place the solar surface in a special orientation to alert field
maintenance workers
that a piece of a PV or CPV system is malfunctioning.
[0029] In a seventeenth embodiment various pre-programmed control protocols
and
algorithms can be incorporated into the robotic controller for dealing with
various field level
scenarios. These robotic control algorithms may also be updated by a field or
remote
operator.
[0030] In an eighteenth embodiment various security features in the robot can
be
incorporated to deter from reverse engineering and theft. The robot may also
include a
tracking feature to enable recovery of lost or stolen robots.
[0031] The features and advantages described in the specification are not all
inclusive
and, in particular, many additional features and advantages will be apparent
to one of
ordinary skill in the art in view of the drawings and specification. Moreover,
it should be
noted that the language used in the specification has been principally
selected for readability
and instructional purposes, and may not have been selected to delineate or
circumscribe the
inventive subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 is an illustration a passive solar surface that can be
precisely repositioned
without an individual microprocessor, azimuth drive motor, elevation drive
motor, central
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control system, backup power supply, or calibration sensor in accordance with
an
embodiment of the present invention.
[0033] Figure 2 is an illustration of a passive solar tracker or heliostat
that does not
require a gear reduction to transform rotational input motion from an
adjustment wheel or
wheels into single or dual axis control of a solar surface in accordance with
an embodiment
of the present invention.
[0034] Figure 3 is an illustration of a robotic controller in accordance with
an
embodiment of the present invention.
[0035] Figure 4 is an illustration of an embodiment of a non-contact interface
between a
robotic controller and an adjustment wheel.
[0036] Figure 5 is an illustration of various components of the robotic
controller in
accordance with an embodiment of the present invention.
[0037] Figure 6 is a flowchart of the operation of the robotic controller in
accordance
with an embodiment of the present invention.
[0038] Figure 7 is a flowchart of the operation of a mid-grade robotic
controller in
accordance with an embodiment of the present invention.
[0039] Figure 8 is a flowchart of the operation of a lower-grade robotic
controller in
accordance with an embodiment of the present invention.
[0040] Figure 9 is an illustration of some communication techniques that may
be used by
the robotic controllers in accordance with an embodiment of the present
invention.
[0041] Figure 10 is an illustration of a robotic controller with multiple
adjustment wheel
interfaces in accordance with an embodiment of the present invention.
[0042] Figure 11 is an illustration of a robotic controller that is able to
control adjustment
wheels without stopping at an adjustment station in accordance with an
embodiment of the
present invention.
[0043] Figure 12 is an illustration showing the manner in which a robot
transport tube
may be routed in a system with many solar surfaces in accordance with an
embodiment of the
present invention.
[0044] Figure 13 is an illustration of a climate control system for the
robotic controller in
accordance with an embodiment of the present invention.
[0045] Figure 14 is an illustration of a robotic controller that utilizes a
wireless power
transfer interface to charge an energy storage mechanism in accordance with an
embodiment
of the present invention.
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[0046] Figure 15 is a flowchart of an operational process of a robotic
controller's onboard
diagnostic and quality assurance system in accordance with an embodiment of
the present
invention.
[0047] The figures depict various embodiments of the present invention for
purposes of
illustration only. One skilled in the art will readily recognize from the
following discussion
that alternative embodiments of the structures and methods illustrated herein
may be
employed without departing from the principles of the invention described
herein.
DETAILED DESCRIPTION OF THE INVENTION
[0048] A preferred embodiment of the present invention is now described with
reference
to the figures where like reference numbers indicate identical or functionally
similar
elements. Also in the figures, the left most digits of each reference number
corresponds to
the figure in which the reference number is first used.
[0049] Reference in the specification to "one embodiment," "a first
embodiment," "a
second embodiment or to "an embodiment" (for example) means that a particular
feature,
structure, or characteristic described in connection with the embodiments is
included in at
least one embodiment of the invention. The appearances of the phrase "in one
embodiment,"
"a first embodiment," "a second embodiment" or "an embodiment" (for example)
in various
places in the specification are not necessarily all referring to the same
embodiment.
[0050] Some portions of the detailed description that follows are presented in
terms of
algorithms and symbolic representations of operations on data bits within a
computer
memory. These algorithmic descriptions and representations are the means used
by those
skilled in the data processing arts to most effectively convey the substance
of their work to
others skilled in the art. An algorithm is here, and generally, conceived to
be a self-consistent
sequence of steps (instructions) leading to a desired result. The steps are
those requiring
physical manipulations of physical quantities. Usually, though not
necessarily, these
quantities take the form of electrical, magnetic or optical signals capable of
being stored,
transferred, combined, compared and otherwise manipulated. It is convenient at
times,
principally for reasons of common usage, to refer to these signals as bits,
values, elements,
symbols, characters, terms, numbers, or the like. Furthermore, it is also
convenient at times,
to refer to certain arrangements of steps requiring physical manipulations or
transformation of
physical quantities or representations of physical quantities as modules or
code devices,
without loss of generality.
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[0051] However, all of these and similar terms are to be associated with the
appropriate
physical quantities and are merely convenient labels applied to these
quantities. Unless
specifically stated otherwise as apparent from the following discussion, it is
appreciated that
throughout the description, discussions utilizing terms such as "processing"
or "computing"
or "calculating" or "determining" or "displaying" or "determining" or the
like, refer to the
action and processes of a computer system, or similar electronic computing
device (such as a
specific computing machine), that manipulates and transforms data represented
as physical
(electronic) quantities within the computer system memories or registers or
other such
information storage, transmission or display devices.
[0052] Certain aspects of the present invention include process steps and
instructions
described herein in the form of an algorithm. It should be noted that the
process steps and
instructions of the present invention could be embodied in software, firmware
or hardware,
and when embodied in software, could be downloaded to reside on and be
operated from
different platforms used by a variety of operating systems. The invention can
also be in a
computer program product which can be executed on a computing system.
[0053] The present invention also relates to an apparatus for performing the
operations
herein. This apparatus may be specially constructed for the purposes, e.g., a
specific
computer, or it may comprise a general-purpose computer selectively activated
or
reconfigured by a computer program stored in the computer. Such a computer
program may
be stored in a computer readable storage medium, such as, but is not limited
to, any type of
disk including floppy disks, optical disks, CD-ROMs, magnetic-optical disks,
read-only
memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or
optical cards, application specific integrated circuits (ASICs), or any type
of media suitable
for storing electronic instructions, and each coupled to a computer system
bus. Memory can
include any of the above and/or other devices that can store
information/data/programs.
Furthermore, the computers referred to in the specification may include a
single processor or
may be architectures employing multiple processor designs for increased
computing
capability.
[0054] The algorithms and displays presented herein are not inherently
related to any
particular computer or other apparatus. Various general-purpose systems may
also be used
with programs in accordance with the teachings herein, or it may prove
convenient to
construct more specialized apparatus to perform the method steps. The
structure for a variety
of these systems will appear from the description below. In addition, the
present invention is
not described with reference to any particular programming language. It will
be appreciated
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that a variety of programming languages may be used to implement the teachings
of the
present invention as described herein, and any references below to specific
languages are
provided for disclosure of enablement and best mode of the present invention.
[0055] In addition, the language used in the specification has been
principally selected for
readability and instructional purposes, and may not have been selected to
delineate or
circumscribe the inventive subject matter. Accordingly, the disclosure of the
present
invention is intended to be illustrative, but not limiting, of the scope of
the invention.
[0056] Referring now to the drawings, Figure 1 depicts a passive surface (101)
that can
be precisely repositioned without an individual microprocessor, azimuth drive
motor,
elevation drive motor, central control system, backup power supply, or
calibration sensor.
Two adjustment wheels (102) controlled by a single robotic controller may
actuate this
system through a flexible or rigid drive shaft (103). The depicted system uses
a flexible cable
to transmit rotational motion from a fixed adjustment wheel to the azimuth
gear train (104)
and the elevation lead screw assembly (105). Fixed adjustment wheels are
desirable as they
enable a relatively simple robotic controller that can move along a track or
tube (106).
However, this design constraint is not necessary as the robotic controller
does not need to be
confined to a set path, and can move freely throughout a field of solar
surfaces.
[0057] The robot transport track may include a hollow square or circular tube
made out of
aluminum, steel, non-ferrous metals, ferrous metals, plastic, or composite
materials. The
passive solar surface may be supported by a number of foundation types
including but not
limited to: driven pier (107), ground screw, ballasted, or simply bolted to a
rigid surface. The
robot transport tube may also be used as a foundational support for individual
passive solar
surfaces.
[0058] Figure 2 demonstrates an embodiment of a passive solar tracker or
heliostat that
does not require a gear reduction to transform rotational input motion from an
adjustment
wheel (102) or wheels into single or dual axis control of a solar surface. The
system may be
actuated in a tip-tilt fashion directly by a flexible drive shaft (103). In
one embodiment, the
flexible drive shaft connects directly to a pin joint (201) that is rigidly
fixed to one rotational
axis. Rotation of the adjustment wheel therefore alters the rotation of the
solar surface in a
1:1 manner on one axis. This system may utilize friction to lock the position
of a solar surface
or other active braking mechanisms described in Patent Application No.
13/118,274,
referenced above.
[0059] Figure 3 demonstrates the present invention's core actuation paradigm
of passive
systems with active robotic control. A robotic controller (301) is able to
propel itself along a
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track (106), stop near a solar surface (101), and precisely control the
rotation of one or more
adjustment wheels (102) linked to aforementioned solar surface using an
onboard adjustment
wheel interface (302). Each adjustment wheel is connected to a rigid or
flexible shaft that can
be routed to accommodate many passive tracker designs. The present invention
focuses on
features of the robotic controller to ensure that the adjustment wheels are
reliably and
precisely repositioned.
[0060] It is desirable to provide a large amount of input torque to the
adjustment wheels
as to decrease the gear reduction needed to reposition a solar surface.
Contact based
adjustment methods may be used, but are prone to poor station alignment,
mechanical
fatigue, and are difficult to seal from the installation environment. If
necessary, the robotic
controller may use positive mechanical engagement, friction, or suction based
systems, for
example, to mechanically control the rotation of an adjustment wheel.
[0061] Figure 4 shows one embodiment of a non-contact interface between a
robotic
controller and an adjustment wheel (102). This system uses individually
controlled
electromagnets (401) to rotate a metallic adjustment wheel. The adjustment
wheel may have a
distinct metallic form (402) that enables certain electromagnetic coil firing
patterns to alter its
degree of rotation. Other systems/embodiments may utilize permanent magnets on
the
adjustment wheel and/or permanent magnets on the robotic controller (301).
Systems that
utilize a permanent magnet or contact based adjustment interface may be
connected to a
rotational drive system in order to rotate the adjustment wheel. Systems that
utilize
electromagnets on the robotic controller side may be solid state. In many
embodiments
adjustment interfaces using electricity to control the rotation of an
adjustment wheel use
electromagnets, and it is most effective from an energy usage and system
lifetime perspective
to reduce the adjustment interface to a simple axial flux or induction motor
wherein the
expensive components are contained on the robotic controller.
[0062] Figure 4 also shows that a robotic controller may contain a system to
detect the
orientation of an adjustment wheel before, after, and during adjustment. These
systems may
utilize one or more sensors (403) to detect the position of a distinct marking
(404) on the
adjustment wheel. Types of markings include, but are not limited to magnetic
or metallic
materials, physical indents, or markings that can be recognized by an optical,
electromagnetic, or electrostatic sensing mechanism. This system is useful
because it allows
the robotic controller to verify that a solar surface has been correctly
repositioned by a
distinct number of input rotations. It also allows the robot to verify that
the wheel has not
rotated between adjustments.
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[0063] Figure 5 depicts an overview of a robotic controller's components in
accordance
with an embodiment of the present invention. From this view it can be seen
that the robot has
idler (501) and drive wheels (502) that keep it aligned and propel it along an
enclosed track.
These idler wheels may be spring-loaded to index the robotic controller to one
or two sides of
the track. The robotic controller may also include a calibration camera (503)
and a structured
light emission mechanism to discover the orientation of a solar surface in 3D
space. For
systems/embodiments that utilize an enclosed track, a window(s) or other
opening transparent
to a particular frequency can be positioned in the track near a solar surface.
This window(s)
allows a calibration camera to view the underside of the solar surface.
Puncturing a hole in
the robot transport tube may create this window. To enable the track to remain
sealed, a piece
of glass, plastic, or other transparent material may cover the hole.
[0064] To reposition a solar surface, the robotic controller must be able to
control the
position of one or more adjustment wheels. This may be accomplished through
the use of an
adjustment interface that can include solid-state electromagnetic coils (401)
that may be
activated/deactivated individually. Adjustment wheel rotation sensors (403)
may enable the
robotic controller to determine the instantaneous position of the adjustment
wheel. Other
components of the robotic controller not depicted may include but are not
limited to an
individual station detection unit, global or relative location discovery unit,
internal wiring,
central processing unit, motor driver controller, drive motor encoder, onboard
climate control
system, battery management system, contact based charging system, inductive
charging
system, distance proximity sensor, data storage system, capacitor storage
system for
regenerative braking purposes, and wireless data transmitter/receiver. The
precise placement
of these components varies depending on the embodiment as they can be housed
in many
configurations within the confines of a robotic controller.
[0065] Figure 6 shows the operational process of the robotic controller in
accordance
with an embodiment of the present invention. This operational process
demonstrates how a
single robotic controller (301) may reposition a multiplicity of solar
surfaces (101). The
functional duty of this robotic controller is to work in conjunction with one
or more
adjustment wheels (102) near a solar surface to properly maintain the
orientation of an
individual solar surface.
[0066] When a robotic controller is first deployed, its initial goal is to
understand its
environment and the passive trackers/heliostats it will be controlling. This
begins with the
robotic controller moving towards an adjustment wheel (601) and continually
searching for a
braking point (602) placed near a solar surface. This point could be an actual
marking on the
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beam, a magnet, or a piece of metal, for example. If there is an actual
marking on the beam,
the robotic controller may be outfitted with a camera to detect this point. If
the braking point
is magnetic or metallic, the robotic controller may be outfitted with Hall
effect sensors or
metal detection system to discover the braking point. In one embodiment, the
adjustment
wheel or markers on the adjustment wheel used for rotational sensing may be
used as the
braking point. After the braking point has been detected, the robotic
controller may activate
its braking mechanism (603). Methods of braking may include but are not
limited to:
deactivation of the drive motor, application of a wheel brake, application of
a motor brake,
regenerative braking, or a hybrid of these braking mechanisms. While the
device is slowing
down, the robotic controller searches for the final adjustment point (604).
Once this point has
been found, it applies a full brake and brings itself to a complete stop
(605).
[0067] After properly aligning itself to one or more adjustment wheels, the
robotic
controller discovers its relative orientation to the solar surface. If it is
the first time that a
robotic controller has visited a particular solar surface adjustment station,
it may "zero" the
solar surface by adjusting it to zero degrees tilt and zero degrees of
azimuthal rotation or
another defined setting. To achieve this goal, the robotic controller may
engage an adjustment
wheel (606), and begin rotating it (607). While rotating, it may use onboard
adjustment wheel
sensors (403) to verify that the wheel is spinning properly (608). The solar
surface may have
hard calibration stops that prevent it from being rotated past the zero point.
In these systems,
the robotic controller may stop trying to adjust the system once the wheel can
no longer be
rotated (609). To prevent damage to a passive surface or a gear train attached
to a passive
surface, a robotic controller's adjustment wheel interface may include a
mechanism that
prevents the system from delivering a damaging amount of torque.
[0068] For applications that do not require much precision, the robotic
controller may use
these stops and record the number of adjustment wheel revolutions from an
initial calibration
point during daily operation to estimate the current orientation of the
surface. For more
precise applications, the robot may also use a structured or natural light
camera to analyze the
underside of a solar surface to determine its relative orientation in 3d
space. Once this
information has been obtained, it is relayed to a central processor for
analysis.
[0069] Depending on the solar application, it may also be necessary to find
the absolute
or relative location of the solar surface in X, Y, and Z coordinates. This may
be accomplished
with an onboard GPS unit with a triangulation system that utilizes three
locations in the field
of solar surfaces. In this second method, the robotic controller may emit a
signal and measure
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the time delay from each defined point in the field. Using this information,
it may determine
its relative location to other components in the field of solar surfaces.
[0070] The central processing may now analyze inputs from the calibration
camera,
location discovery unit, internal clock, and combine this with the known gear
reduction of the
passive solar tracker/heliostat, and known field geometry (610). Inputs from
the robot's
internal clock and discovered or known global location can be used to
calculate the current
solar vector (611). Inputs from the robot's calibration camera, location
discovery unit,
adjustment wheel sensing mechanism, and/or historic adjustment information
from past
adjustments can be used to approximate the orientation of a solar surface in
3D space. In one
embodiment, the passive solar tracker or heliostat driven by the adjustment
wheels has anti-
back drive properties. These systems only require a one-time calibration as
wind and other
forces are unable to move the solar surface between adjustments.
[0071] PV and CPV applications may use up to five pieces of information for
proper
repositioning. The orientation of the solar surface, the position of the sun,
the orientation of
adjacent trackers, the distance between trackers, and the pre-defined tracker
area and
dimensions of the solar surface. Standard solar tracking algorithms may only
require the first
two pieces of information, but the robot uses the other three to properly
execute backtracking
control algorithms. These algorithms optimize a solar field for minimal inter-
tracker shading,
and therefore understand the shadows that are currently being generated by
adjacent trackers,
and the shadow that an individual solar tracker will cast on its neighbors.
More details
regarding backtracking are found at Mack, Solar Engineering: http://www.rw-
energy.comlpdtlyield-of-s vvtheel-Almansa-graphics.pdf which is incorporated
by reference
herein in its entirety.
[0072] Heliostat applications require the robot to discover the vector from a
solar surface
to a solar target. This may be achieved by finding the location of both the
solar target and the
solar surface in a global or relative coordinate plane. Once the desired
change in solar surface
orientation has been calculated, the central processor analyzes a passive
system's known gear
reduction to determine how many degrees it should rotate an adjustment wheel
linked
mechanically or magnetically to the solar surface (612).
[0073] For passive trackers or heliostats that do not have inherent friction
braking or anti-
back drive properties, an active solar surface braking mechanism may be
necessary. For these
systems, the robotic controller deactivates the brake prior to rotating the
adjustment wheel or
wheels. This brake may be actuated with another adjustment wheel. The robotic
controller
may then use its adjustment wheel interface to rotate one or more adjustment
wheels. In one
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embodiment, the robotic controller has a multiplicity of electromagnetic coils
that can be
activated individually or in groups. This system is able to control the
rotation of a metal or
magnetic adjustment wheel by firing the coils as an axial flux or induction
style motor (613).
The coils may be fired blindly or may obtain feedback from an adjustment wheel
sensing
mechanism that determines the instantaneous degree of rotation of an
adjustment wheel
(614).
[0074] Once adjustment is complete, the central processor may send a signal to
actuate
the braking mechanism if necessary. This re-engages the gear braking mechanism
and
prevents outside forces from altering a solar surface's orientation until its
next adjustment
from the robotic controller. As a final step of this process, the robotic
controller may use
onboard proximity sensors or past operational history to determine if it is
currently at the end
of a row of solar surfaces (615). If yes, it may move backward until it
reaches the first solar
surface adjustment point (616). If no, the controller may repeat this
adjustment cycle (617).
Also note that it is possible to connect the ends of a robot transport tube
such that it forms a
continuous loop. In this embodiment, robotic controller would continue
circulating the robot
transport tube until nighttime or stopping for maintenance.
[0075] The processor that determines the behavior of the robotic controller
and its sub
components could be located on the robotic controller directly, at a central
processing station,
or on another robotic controller in the field of solar surfaces. If the
processor is not onboard,
the robotic controller may require a wireless or direct data liffl( to receive
operational
instructions.
[0076] After a day of adjusting solar surfaces, the robotic controller may
need to recharge
its onboard energy storage mechanism. It may also recharge this system two or
more times
throughout the day.
[0077] It may be desirable for a field of solar surfaces to be adjusted by
three or more
grades of robotic controllers. Figure 6 demonstrates the operational process
of a top grade
robotic controller. This robot may work in conjunction with less sophisticated
robotic
controllers. A purpose of the top grade robotic controller is to permit the
removal of the
location discovery unit and calibration camera from both the mid and low grade
robotic
controllers. In an embodiment, a field of solar surfaces may only use one top
grade robotic
controller (if any) and could therefore greatly reduce total system and
robotic controller
replacement costs by removing expensive components from the unit.
[0078] Figure 7 shows the operational process of a less sophisticated, mid
grade robotic
controller in accordance with an embodiment of the present invention. The main
difference
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between this unit and the top grade robotic controller described in figure 6
is that this adjustor
does not have a calibration camera or a location discovery unit. The
functional duties of the
calibration camera and the location discovery unit are assumed by a data
discovery unit that
communicates with other robots or a central control station, and a data
storage unit that stores
the last known orientation of individual solar surfaces. When a mid grade
robotic controller
first interacts with a passive solar surface and has no prior data points, it
may assume that the
top grade robotic controller has properly "zeroed" the solar surface.
[0079] Unlike a top grade robot, a mid-grade robotic controller pulls its
input for the
adjustment point's location from a data storage unit instead of a location
discovery unit (701).
It also determines the relative orientation of a solar surface from an onboard
data storage unit
and Hall effect sensors instead of a precise calibration camera. The data
storage unit stores
the number of adjustment wheel rotations from the zero point, and the
adjustment wheel
sensing mechanism is used to determine the exact degree of wheel rotation
(702). Combined
with known gear reduction information, this data may be sufficient for the mid
grade robotic
controller to approximate the orientation of a solar surface in 3D space. As
the mid grade
robotic controller does not have a method of determining the exact orientation
of a solar
surface directly, it may save the degree of adjustment wheel rotation
performed to one or
more adjustment wheels so that it may properly reorient a solar surface in
future adjustments.
[0080] After a day of adjusting solar surfaces, the robotic controller may
need to recharge
its onboard energy storage mechanism. It may also recharge this system two or
more times
throughout the day.
[0081] Figure 8 shows the operational process of a less sophisticated, low-
grade robotic
controller in accordance with an embodiment of the present invention. The
purpose of a low-
grade robotic controller is similar to a spare tire for a car¨it is to be used
only in emergency
situations. This third class of robotic controllers enables a low cost, and
rapid wind stow
procedure. It also enables a high-speed emergency defocus procedure for
heliostat
applications. This robotic controller may have a similar operational process
as the mid grade
robotic controller described in figure 7, but it may only require one
adjustment interface to
move a passive solar tracker or heliostat to its wind stow position, and would
not need to be
built for long lifetime.
[0082] During emergency procedures, the low-grade robotic controller would not
need to
know the current position of a solar surface, only that the solar surface must
be either a)
moved 2-5 degrees away from its current position or b) moved into a horizontal
wind stow
position. It may have an onboard anemometer to determine current wind speed or
may be
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connected to a central network that sends the low-grade robotic controller a
signal to initiate
an emergency wind stow procedure (801). This procedure begins with the robotic
controller
moving itself near an individual solar surface, stopping near a solar
surface's adjustment
wheel (605), and rotating the adjustment wheel a pre-defined number of
revolutions (802). It
may also use an adjustment wheel sensing mechanism (403) to determine if the
adjustment
wheel has stopped rotating (614). If it has, this may indicate that the low-
grade robotic
controller has driven the passive solar tracker or heliostat into its wind
stow hard stop.
[0083] The process for emergency defocus may be even simpler than for
emergency wind
stow. As the purpose of this procedure is to move a heliostat's image away
from a solar
target, the low-grade robotic controller only needs to be able to quickly
alter the position of
many solar surfaces.
[0084] Figure 9 demonstrates some of the methods that could be used by a field
of
robotic controllers to communicate with each other and/or with a centralized
network. These
methods include, but are not limited to: wireless data communication (901),
direct data liffl(
(902), external switches, or by storing information near individual passive
solar surfaces or
groups of passive solar surfaces (903). For wireless data communication, each
robotic
controller may be equipped with an electromagnetic frequency transmitter
and/or receiver
(904) that is able to communicate with other robots (301) or a centralized
network (905).
[0085] For direct data transfer, each robotic controller may be equipped with
contacts that
can interact with contacts on other robots or a centralized data unit. When
these systems
make physical contact, data may be transferred from one device to another.
[0086] A human or robotic field operator may activate certain features on a
top, mid, or
low-grade robot that correspond to certain pre-programmed actions. Actuating
an external,
magnetic, or electromagnetic switch may initiate these actions. For example,
if a low-grade
robot has a pre-programmed emergency defocus feature, a mid-grade robot may be
able to
activate it simply by running into it and depressing a push button switch.
[0087] It is also useful to be able to store relevant data near individual
solar surfaces or
groups of solar surfaces. In one embodiment, an RFID chip (903) placed near a
solar surface
may be used to store the information about each solar surface's absolute or
relative location
in the field and how this corresponds to the initial position of each
adjustment wheel. These
systems would require individual robotic controllers to have an RFID writer
and/or RFID
reader. Other methods of storing data locally include but are not limited to
using
semiconductor, magnetic, and/or optical based data storage technologies.
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[0088] Figure 10 shows a robotic controller (301) with multiple adjustment
wheel
interfaces (302). The purpose of adding more adjustment interfaces is to
distribute the cost of
the most expensive onboard components and to allow for more precise control of
a solar
surface (101) by permitting more frequent adjustments over the same period of
time. The
depicted embodiment is able to adjust two solar surfaces at one time; enabling
this design to
cut the number of start-stop cycles for a given field of solar surfaces in
half.
[0089] Figure 11 shows a robotic controller (301) that is able to control
adjustment
wheels without stopping at an adjustment station. This system may utilize a
contact,
magnetic, or electromagnetic based gear rack and pinion system to control the
adjustment
wheel. The robotic interface conceptually serves as the gear rack (1101) and
the adjustment
wheel (102) as the pinion (1102). As the robot drives past an adjustment
wheel, it may
actuate its conceptual gear rack interface so that it couples¨physically,
magnetically, or
electromagnetically¨with one edge of an adjustment wheel. Once coupled, the
linear motion
of the robotic controller may be turned directly into rotation of the
adjustment wheel. The
robotic controller may actuate its interface (1101) a second time to decouple
itself from the
adjustment wheel pinion (1102). The robotic controller can precisely control
the rotation of
an adjustment wheel by carefully monitoring its speed and time that its
adjustment interface
is coupled with an adjustment wheel. For example, if a robotic controller is
moving at 1 meter
per second and engages the edge of a 3.18cm diameter adjustment wheel (10cm
circumference) for 1 second, it will rotate it approximately 10 times.
[0090] The robotic controller can utilize a long strip of sensors (403) that
measure the
instantaneous degree of wheel rotation to confirm that the adjustment wheel
(102) has been
engaged and is spinning properly. A robotic controller that does not stop or
make physical
contact with individual solar surfaces may accurately reposition up to 1.2MW
of photovoltaic
modules if moving at a constant rate of 5MPH.
[0091] The robotic controller depicted in figure 11 uses a long line of
individually
actuated electromagnets (401) to control the orientation of an adjustment
wheel. When these
electromagnets are turned on in a (N-S-N-S-N-S) arrangement, they are able to
rotate 4-pole
magnetic adjustment wheel (N-S-N-S) simply by driving past the adjustment
station. This
magnetic gear rack system turns linear motion of the robot into rotational
motion of the
adjustment wheel.
[0092] Figure 12 shows how the robot transport tube (106) may be routed in a
field with a
large number of solar surfaces (101). The robot transport tube may be
hermetically sealed to
prevent large object, water, and dust ingress into the robotic controller. In
the depicted
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embodiment, each passive solar tracker or heliostat has an individual
foundation and the
robot transport tube only has to support the weight of a robotic controller or
controllers.
[0093] This figure demonstrates that while an individual robotic controller
may normally
adjust a particular row of solar surfaces, it can utilize an onboard drive
motor to return itself
to a central station for maintenance (1201). This style of track routing also
enables a field
operator easily deploy a field of robotic controllers by inserting two or more
of them into a
central station. This central station may also be used for charging or
maintenance purposes.
[0094] Figure 12 also demonstrates that excess robotic controllers (301) can
be used
redundantly. In one embodiment, one or more backup robotic controllers are
placed at the
central station. In the case of a robotic failure, a backup robotic controller
can drive itself into
the proper section of track, push the failed robot to the end of the tube and
resume adjustment
solar surfaces assigned to the failed robot. If the failed robot was not
constantly relaying the
position of its assigned solar surfaces to a central data system, it may be
necessary for the
backup robot to run an initial re-calibration process as outlined in figure 6.
If this information
was accurately relayed to a central data system, the backup robot may resume
operation
wherein the failed robot stopped adjusting.
[0095] In the case that a field of solar surfaces does not have a central
robot collection
system, two or more robots may be placed into one section of track. These two
or more
robots may establish a constant data transfer link. One robot may assume daily
operation
(1202) while the other serves as a redundant robot (1203) to prevent power
loss due to failed
controllers not being able to properly reposition a solar surface's adjustment
wheels.
[0096] Figure 13 shows one embodiment of a climate control system for the
robotic
controller (301). This system may comprise, but is not limited to including
the following
components: fan (1301), heat sink (1302), active heat pump, Peltier device,
electric heater,
ventilation system, refrigerator, humidity control system, moisture sensors,
temperature
sensors, and air filter. These climate control components may also be
offloaded onto a sealed
robot transport tube so that the system may maintain a consistent environment
that prolongs
the life of the robotic controller's key failure components.
[0097] It may be useful to use batteries, capacitors, super capacitors, or
other forms of
energy storage to reduce installation complexity and overall system cost as a
single battery
can replace one mile of electrified track. Figure 14 shows one embodiment of
the present
invention that utilizes a wireless power transfer interface to charge an
energy storage
mechanism onboard the robotic controller. Wireless charging mechanisms may be
desirable,
as they do not require exposed contacts to transmit power to a robotic
controller. It is not
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necessary, however, for the robotic controller to have an onboard source of
stored energy,
and it could be powered by an electrified rail system, or inductively by the
track.
[0098] An inductive charging station (1401) placed at any location on the
robot transport
tube is able to transfer energy to the robotic controller by generating an
oscillating
electromagnetic field. An inductive coil loop (1402) placed on the robotic
controller (301) is
able to capture this energy and store it within an onboard energy storage
mechanism. Other
forms of power transfer that could be utilized by the robotic controller
include, but are not
limited to: electrostatic induction, electromagnetic radiation, and electrical
conduction.
[0099] Figure 15 shows the operational process of a robotic controller's
onboard
diagnostic and quality assurance system. A robotic controller may continuously
perform
aspects of this process to enable a field or remote operator to determine a
field's
instantaneous health. This process in its entirety or certain aspects of this
process may also be
initiated daily, weekly, monthly, or as needed to enable field operators to
perform preventive
maintenance of the system. In particular, a robotic controller's diagnostic
system may
determine: a) the overall health of an individual robotic controller as
defined by the status of
key components (1501), b) the health of a robot transport tube (1502), c) the
health of a
passive solar tracker or heliostat (1503), and d) the health of an individual
PV or CPV surface
(1504).
[0100] This process may begin with the robotic controller relaying all saved
operational
data to a central processing system or network (1505). This data may include,
but is not
limited to: historical temperature and moisture readings on internal and
external sensors,
historic meteorological data from an on or offsite monitoring system, historic
current and
voltage readings from all onboard components, and SOC/SOS readings from an
onboard
energy storage mechanism. The diagnostic system may then compare this
information to past
operational data (1506) and to pre-defined safe ranges of operation (1507).
Analysis of
irregularities may be used to determine the current health of individual
components and/or to
perform preventative maintenance of a robotic controller (1508).
[0101] To determine the health of a robotic transport tube (1502), the robotic
controller
may access data from onboard cameras or proximity sensors that are able to
inspect the
physical features of the track (1509). If any abnormalities are discovered,
such as an object
protruding into the track, a large build up of dirt in one section of track, a
hive of insects, or a
puncturing in the track that allows foreign object ingress, the robotic
controller may send a
signal to a field or remote operator (1510). A field or remote operator may
access a live video
feed from the robotic controller's camera in order to better assess a
maintenance situation.
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[0102] To determine the health of a passive solar tracker or heliostat, a
robotic controller
may access the data log generated from adjusting an individual tracker (1511).
It may then
access the data log measuring the amount of input torque/current needed to
rotate an
adjustment wheel (1512) and understand how this metric changes over time. If
the robot uses
an electromagnetic interface, this torque metric can be determined by
recording the average
current delivered to the interface over the course of an adjustment. In one
example, if the
diagnostic system recognizes that a passive solar tracker that usually
requires 95 +/-5 amps
suddenly begins requiring 320 +/- 20amps to adjust during normal operating
conditions, it
may deem this individual passive tracker to be dysfunctional and send an alert
a field
maintenance worker (1513). The robotic controller may also use vision-based
systems to
inspect and analyze the health of an individual solar tracker or heliostat.
This video input may
be relayed directly to a field operator to assess the health of the tracking
system. If a passive
tracker's torque/current readings are within an acceptable range, this portion
of the process
(1503) may be repeated for every passive surface (101) under a robot's control
domain.
[0103] To autonomously determine the health of an individual PV or CPV surface
(1504), the robotic controller may first move an individual tracker into its
optimal orientation
(1515). It may then communicate with a device that is able to monitor the
power output of a
central inverter, combiner box, or individual string of solar modules (1516).
As it is possible
that in the robotically controlled system that only one module in a group of
modules may be
actuated at a single moment in time, the power output reading should remain
relatively
constant. Once a data link has been established, the robot may execute a
search algorithm
(1517) where it moves the passive surface in a spiral while monitoring system
output. It may
then record the maximum power point (1518) and adjust the tracker so that it
is no longer
facing the sun (1519). The diagnostic system may measure the change in central
inverter,
combiner box, or string level output (1520). This information can be used to
determine the
degradation percentage of an individual module by measuring the exact
difference in central
inverter, combiner box, or string level output and comparing this to a
module's rated output
(1521) to calculate degradation percentage (1522). If no change is detected,
this may indicate
that an individual solar surface (101) is not contributing to the PV or CPV
system's total
output. This module may be classified as defective and the robotic controller
may use its
adjustment interface to place this surface in a special configuration as to
alert field
maintenance workers of the potential problem (1523). If the degradation
percentage is within
an acceptable range, sub process 1504 may be repeated for all surfaces under a
robot's
control domain (1524).
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[0104] The robotic controller may also include pre-programmed algorithms and
security
features to protect itself from theft and/or reverse engineering. Onboard
controllers and data
storage units may be encrypted to prevent access to control protocols and data
stored on the
robot. In addition, there may be sensors that detect unauthorized access to
the robot,
including attempts to open a robotic controller. The controller may respond to
such actions by
notifying a remote operator and/or erasing the control algorithms and
operational data. At the
time of deployment, each robot may be initialized with its deployment location
and unique
identification number. If the robot, field operator, or remote operator
detects that the robot is
no longer in the assigned location, then an appropriate action may be taken to
retrieve the lost
or stolen robotic controller.
[0105] While particular embodiments and applications of the present invention
have been
illustrated and described herein, it is to be understood that the invention is
not limited to the
precise construction and components disclosed herein and that various
modifications,
changes, and variations may be made in the arrangement, operation, and details
of the
methods and apparatuses of the present invention without departing from the
spirit and scope
of the invention.
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