Abstract:
A solar panel array is formed of a plurality of solar panels juxtaposed with one another along an array axis, and has a support element having first and second support terminations disposed substantially orthogonal to the array axis, with an unobstructed spatial region intermediate of the first and second support terminations. A vehicle transports the solar panels and has wheels arranged on opposing sides thereof. First and second track structures extend along the array axis and are coupled to respective ones of the first and second support terminations. The track structures each have an elongated portion for engaging and supporting respective ones of the vehicle wheels, whereby the vehicle travels along the tracks while carrying a solar panel, and at least a portion of the vehicle is disposed within the unobstructed spatial region. One of the tracks accommodates the wiring for the solar panel array.

Description:
RELATIONSHIP TO OTHER APPLICATION 
     This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 61/509,471 filed Jul. 19, 2011, Conf. No. 3965 (Foreign Filing License Granted) in the names of the same inventors as herein. The disclosure in the identified United States Patent Application is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates generally to systems for transporting and installing large photovoltaic modules, and more particularly, to a photovoltaic module handling system that does not require a conveyance vehicle to travel along the ground and that enables substantially automated and rapid replenishment of photovoltaic modules in a solar panel array. 
     Description of the Prior Art 
     Conventional solar panels typically are constructed using a plurality of photovoltaic cells that are electrically connected to one another in a series arrangement to form a large module. A typical solar panel of the type that is used industrially will weigh on the order of 120 kg, or more. Such large and heavy structures are heavier than a human individual alone can handle, requiring large equipment that travels back and forth in the array to replenish the supply of photovoltaic solar panels. This use of heavy equipment, however, damages the surface of the unprotected ground, requiring that grading and other procedures be employed to place the ground in condition for further use of the heavy equipment. The damage to the ground surface, coupled with rain and accumulated ground water, can easily increase the cost of operations and electrical production, and bring the project to a halt. 
     There is a need, therefore, for a system for installing, maintaining, and replacing solar panels that does not damage the ground surface. 
     There is additionally a need for a system for installing, maintaining, and replacing solar panels that does not require ongoing procedures that employ heavy equipment. 
     It is another problem with the state of the art that the population of racks with solar panels is a long and arduous process, causing inherent delays in bringing the solar panels on line. Delays in commencing the delivery of electrical power readily translate into lost revenue. 
     There is, therefore, a need for a system of bringing one or more arrays of solar panels quickly and efficiently into production. 
     Yet another problem with the current state of the art is that, since large and heavy equipment is required in the assembly of a solar panel array, the spacing between rows of such arrays must be large. Since space is generally at a premium in most solar farms, output power density, per unit of farm area, is unnecessarily low. Again, this underutilization of the solar farm land adversely affects the financial productivity of the project. 
     It is still another problem in the current state of the art that the use of heavy equipment requires associated workers to load and off-load the delicate solar panels. However, the solar panels are not only heavy, illustratively on the order of 250 lbs, they also are large, sometimes exceeding 3 m in length with a surface area approaching 6 m 2 . The result is inefficiency and an unacceptable amount of module breakage. 
     The heavy equipment that typically is employed in the installation of a solar panel array includes cranes, boom trucks, and the like, as well as excavation equipment that is used to repair the ground to a condition in which such heavy equipment can be operated. Oftentimes, the crane will be operated blindly, wherein the operator receives direction from an observer by radio. Damage to the delicate solar panels is unacceptably common. 
     There is, therefore, a need for a system that safely handles and transports solar panels without the need for large equipment and that does not unduly tax the capabilities of human labor. 
     There is additionally a need for a system that does not require large equipment for replenishment of the solar modules, whereby the spacing between adjacent rows in a solar panel array is reduced, thereby increasing the power output density of the solar project. 
     SUMMARY OF THE INVENTION 
     The foregoing and other deficiencies in the current state of the art are addressed and overcome by this invention, which provides a solar panel array support system formed of a plurality of solar panels supported juxtaposed with one another along an array axis. In accordance with the invention, the solar panel array support system is provided with a support element having first and second support terminations disposed substantially orthogonal to the array axis. An unobstructed spatial region is formed intermediate of the first and second support terminations. In addition, a vehicle is provided for transporting the solar panels, the vehicle having first and second wheels arranged on opposing sides thereof. First and second track structures, each extend substantially parallel to the array axis and are coupled to a respective one of the first and second support terminations. The first and second track structures have a first elongated portion for engaging and supporting respectively associated ones of the first and second wheels. 
     In one embodiment, the vehicle is arranged to travel along the first elongated portions of the first and second track structures, at least a portion of the vehicle is disposed within the unobstructed spatial region intermediate of the first and second support terminations of the support element. 
     The vehicle is configured on a portion thereof distal from the portion of the vehicle that is disposed within the unobstructed spatial region intermediate of the first and second support terminations of the support element, to engage a solar panel and to transport same along the first and second track structures. The first and second track structures each have a second elongated portion for engaging and supporting the solar panel array. 
     There is further provided a latching arrangement on the vehicle for selectably grasping and releasing the solar panel. In one embodiment, the latch arrangement includes a solar panel lift arrangement. In a further embodiment, the vehicle is a motorized vehicle. At least one of the first and second track structures is provided with a third elongated portion for accommodating wiring of the solar panel array. 
     In accordance with a further embodiment, the solar panel array is formed of a plurality of solar panels supported juxtaposed with one another along an array axis, the solar panel array support system includes a support element having first and second support terminations disposed substantially orthogonal to the array axis, there is provided an unobstructed spatial region intermediate of the first and second support terminations. A vehicle transports the solar panels, the vehicle having first and second wheels arranged on opposing sides thereof. The wheels of the vehicle, in this embodiment, engage respective ones of the first and second track structures, each track structure extending substantially parallel to the array axis and being coupled to a respective one of the first and second support terminations, for engaging and supporting the solar panel array. 
     In accordance with a method aspect of the invention, there are provided the steps of: 
     installing an array support having first and second contact ends with an unobstructed spatial region therebetween; 
     installing an elongated support structure on each of the first and second contact ends; 
     mounting a solar panel on a vehicle; 
     urging the vehicle through the unobstructed spatial region; and 
     depositing the solar panel on the elongated support structure. 
     In one embodiment of this method aspect of the invention, the step of mounting a solar panel on a vehicle includes the further step of actuating a gripper on the vehicle. 
     In a further embodiment, there is provided the step of entering into the vehicle information about the solar panel array. 
     In accordance with the invention, an inventive rack arrangement enables the carrying and transportation of an automated solar panel installation and removal system in the form of an automated drone. The rack arrangement is supported above ground by posts that are embedded in the ground using any conventional post embedment means. In a solar panel embodiment of the invention, a pair of east-west rails are supported in parallel relationship and at an angle that is at least in part responsive to the geographical location of the solar panel array. There is provided an arrangement that enables the east-west rails to be oriented at a desired angle relative to the southern horizon. The east-west rails are supported by frame elements that are configured to enable the passage of a solar panel carrier in the region between the frame elements and the east-west rails. 
     In an advantageous embodiment of the invention, there is provided a solar panel installation and removal system that in some embodiments of the invention collects the solar panels from a solar panel repository and conveys same to the location on the rack arrangement where the respective solar panel is to be installed. The solar panel installation and removal system includes, in some embodiments, an automated drone that effects the conveyance of the solar panels. In other embodiments, however, a manually operated dolly is employed. As is the case with the automated drone, the manually operated dolly will convey solar panel along the east-west rails of the rack arrangement. In addition, both forms of conveyances can be configured to carry accessories depending therefrom, such as cabling reels, maintenance supplies, tools, and the like. 
     There is additionally provided a subsystem within the automated solar panel installation and removal system for enabling automated or semi-automated pick-up of the solar panels by the automated drone at a source of solar panels. Of course, such a system facilitates automated or semi-automated removal of the solar panels from the automated drone. 
     As stated, the rack arrangement is configured to permit travel along the east-west rails by an automated drone or a manually operated drone, with or without a solar panel thereon, and in some instances, with an accessory depending therefrom. In a highly advantageous embodiment of the invention the supporting structure for the east-west rails has a semicircular configuration. In other embodiments, however, such supporting structure is configured as a shallow arc, or other geometric configuration, such as a rectilinear arrangement in which the east-west rails are supported on respective stanchions, or purlins, or a triangular configuration, in which the east-west rails are supported on respective ones of two of the legs of the triangle. 
     In practical embodiments of the invention, the east-west rails are permitted to tilt between 5° and 35° in predetermined angular increments, illustratively 5°. The rack arrangement in some embodiments will support loads of typically 1800 Pa (37.6 psf), and higher. 
     In operation, the following steps are followed in some embodiments of the invention: 
     solar panels are assembled at a stacker station; 
     the next solar panel to be installed (the ready panel) is moved to a dock station; 
     the automated drone arrives at the dock station, raises the solar panel to a lift position, and engages solar panel grippers; 
     the automated drone computes the distance to the next installation location; 
     the automated drone accelerates to cruising speed and travels to a computed deceleration point; 
     while the automated drone is traveling and is away from the docking station, a subsequent ready solar panel is moved into the docking station; 
     the automated drone decelerates to the installation location; 
     servos on the automated drone, with the use of fine datum, causes the automated drone to park at the installation location; 
     the automated drone lowers the solar panel to a lock position; 
     the solar panel is held securely in the lock position and is fastened to the rack arrangement; 
     the automated drone disengages the solar panel grippers and lowers the lift to a release position; 
     the automated drone computes the distance to the dock station; 
     the automated drone accelerates to cruising speed and travels to a determined deceleration point; 
     the automated drone decelerates to the dock station; 
     the servos on the automated drone, with the use of fine datum, cause the automated drone to park at the dock station; and 
     the sequence is repeated. 
     In some embodiments of the invention, a solar panel farm is populated from one end of each row of solar panels. Delivery of the solar panels is powered by the automated drone, which in some embodiments is fully electric, and in other embodiments, employs gas-electric propulsion. In small installations, a manually operated dolly is used for conveying the solar panels. However, in some large installations, the automated drone serves as a locomotive that propels one or more manually operated dollies in train-like fashion as non-powered carriers of solar panels. 
     In a practicable embodiment of the invention, the automated drone weighs ˜30 kg and is able to carry a load of ˜120 kg. The automated drone has two or more drive wheels that have associated brakes. The drive system that is employed in the practice of the invention will depend on a variety of factors, such as system cost, availability of fuel, terrain, etc. Generally, the various embodiments of the system are driven either directly, using on-board electric or internal combustion drive, or indirectly, using a cable or the like, wherein a motor is installed at one or both ends of the rack. 
     The automated drone has a lift system having, in some embodiments of the invention, three functional positions, specifically release, lock, and lift. In the lift mode, the solar panel is lifted to facilitate travel along the rack arrangement. The lock mode is applied to bring the solar panel into position for securement thereof onto the rack arrangement. Additionally, the release mode serves to remove the solar panel carrier from communicating with the solar panel. 
     The automated drone is, in some embodiments, protected by a bumper, and is additionally provided with a plurality of safety and collision avoidance systems with respectively associated sensors. In some embodiments, the automated drone has human accessible controls thereon that enable an operator to control various aspects of the operation of the system. Other features that are included in some embodiments of the invention include a connection panel for accessing and delivering data, a user-accessible battery compartment, and an audible warning (sound emitting) device. 
     In embodiments of the invention where an automated drone is applied as a solar panel installation robot, the automated drone&#39;s operation is in some embodiments, manually programmed with a set of parameters that include direction of travel (i.e., origin east or west), solar panel pitch, number of solar panels, and the location and distance of dead spaces where no solar panels are to be installed (e.g., temporary bridges between rows of the array). This manner of programming an automated drone can be time consuming and error prone. 
     In other embodiments, however, the automated drone is self-teaching, as follows: 
     the automated drone is placed on the rack arrangement at the end thereof where the load station is located (i.e., several inches past the first relative solar panel position from the side of the solar panel loader; 
     end stops are placed at each end of the east-west rails of the rack arrangement; 
     the automated drone then is activated so as to function as a transport; 
     the automated drone is initialized with the use of a push button on the mechanical interface of the automated drone; 
     the automated drone then: 
     checks the east and west optical sensors to determine the location of the load station; 
     moves toward the end station until the south facing optical sensor detects the datum mark for the first solar panel; and 
     records the position of the first solar panel location as zero; 
     the automated drone commences motion away from the load station; 
     as the south sensor is triggered by a datum mark on the south purlin, the location of the datum mark is recorded, and the total number of datum marks are recorded. 
     The automated drone continues until one of the following conditions is met: 
     when the end mark at the opposite side of the rack arrangement is encountered and detected by an east/west optical sensor, the automated drone slows and executes a stop at the end of the rack arrangement, while continuing to record datum mark locations and increment the total number of datum marks; 
     when a solar panel is detected by an upward facing sensor in combination with the detection of a datum mark by a south sensor, the automated drone comes to a halt, and does not record the last datum mark (for use in mapping a partially populated array). 
     The automated drone then returns to the load station with the location of all of the solar panels that will be mounted onto the rack arrangement, the total length of the rack arrangement, and the total number of solar panels that are to be installed. 
     In some embodiments of the invention, the automated drone functions as a transport and contains the following features: 
     a programmable CPU; 
     a mechanical interface consisting of pushbuttons, indicator lights, and a power switch; 
     optical sensors installed on the east and west sides of the automated drone; 
     a motor encoder or optical encoder for providing closed-loop information that enables accurate location information to be monitored and recorded; 
     an optical sensor on the south side of the automated drone for determining the location of periodically disposed datum marks (typically in the form of slots); and 
     an upward facing optical sensor on the top of the automated drone for determining whether a panel location is occupied by a solar panel. 
     In some embodiments, a rack arrangement is provided for mounting the solar panels, the rack arrangement having the following features: 
     a track in which the automated drone rides in the east/west direction; 
     removable end stops on which are mounted reflectors for the optical sensors that are mounted on the east and west sides of the automated drone; and 
     registration marks on the south purlin indicating locations of the solar panels; 
     a load station disposed on the east or west sides of the rack arrangement, the load station having a means for placing the solar panels on the rack arrangement; 
     a program for operating the automated drone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which: 
         FIG. 1  is a simplified perspective representation of a rack arrangement that is useful in the practice of a specific illustrative embodiment of the invention; 
         FIG. 2  is a simplified side plan representation of the embodiment of  FIG. 1 ; 
         FIG. 3  is a simplified side plan representation of a prior art rack arrangement; 
         FIG. 4  is a simplified perspective representation of a manually operated dolly that is useful in the conveyance of solar panels in one embodiment of the invention; 
         FIG. 5  is a simplified side plan representation of a rack arrangement constructed in accordance with the principles of the invention and showing an advantageous feature of the invention in that a dolly is able to transport accessories along the rack in addition to a solar panel, specifically in this embodiment, a cable reel; 
         FIG. 6  is an enlarged representation of an identified portion of the embodiment of  FIG. 5 , showing certain features related to the mounting of the dolly on the rack arrangement; 
         FIG. 7  is an enlarged representation of a further portion of the embodiment of  FIG. 5 , distal from the identified portion of  FIG. 6 , showing certain features related to the mounting of the dolly on the rack arrangement as well as an advantageous feature of the invention relating to the location of system cabling; 
         FIG. 8  is a simplified perspective schematic representation of a rack arrangement constructed in accordance with the principles of the invention showing a powered drone transporting a solar panel along the rack arrangement; 
         FIG. 9  is a simplified perspective representation of the drone that is shown in simplified form in  FIG. 8 ; 
         FIG. 10  is a simplified perspective representation of the drone that is shown in  FIG. 9 ; 
         FIG. 11  is a simplified side plan representation of the drone of  FIGS. 9 and 10  installed on a rack arrangement; 
         FIG. 12  is a simplified partially fragmented perspective representation of an embodiment of a drone, the figure illustrating the manner in which the drone engages with the rack arrangement; 
         FIG. 13  is a simplified schematic representation of a vertical stack loader arrangement that employs a pusher bar and that feeds solar panels, in this specific illustrative embodiment of the invention, from beneath; 
         FIG. 14  is a simplified schematic representation of a vertical stack loader arrangement that employs a pusher bar and that feeds solar panels, in this specific illustrative embodiment of the invention, from above; 
         FIG. 15  is a simplified schematic representation of a vertical stack loader arrangement that feeds solar panels, in this specific illustrative embodiment of the invention, with the use of a gripper from above; 
         FIG. 16  is a simplified schematic representation of a specific illustrative embodiment of a vertical stack of solar panels; 
         FIG. 17  is a simplified schematic representation of a specific illustrative embodiment of a stack of solar panels that has been tilted to facilitate the installation of the solar panels onto, or removal of the solar panels from, the rack arrangement; 
         FIG. 18  is a graphical representation that illustrates an advantage that is obtained by the use of the present invention, the advantage being presented in terms of solar panels per hour per drone; 
         FIG. 19  is a graphical representation that illustrates an advantage that is obtained by the use of the present invention, the advantage being presented in terms of kilowatts per hour per drone, when used on solar panel modules that have 500 Watt electrical production capacity; 
         FIG. 20  is simplified schematic plan representation of a lift arrangement that is useful for inclusion as a carrier for installing solar panels; and 
         FIGS. 21( a ), 21( b ), 21( c ), and 21( d )  show respective illustrative 180° arc, shallow arc, raised purlins, and triangular configurations that can be used in respective embodiments of top portions of the rack arrangement of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a simplified perspective representation of a rack arrangement  100  that is useful in the practice of a specific illustrative embodiment of the invention. As shown in this figure, rack arrangement  100  is formed of a plurality of aligned support stanchions  102 ,  103 , and  104  in this embodiment of the invention. The support stanchions are firmly embedded in the ground (not specifically designated) so as to maintain a fixed spatial relation relative to each other. 
     Referring to support stanchion  102 , which is in large measure identical to the others, there is seen in the figure an upper portion  110 , which in this specific illustrative embodiment of the invention has a semicircular configuration with substantially 180° of arc. It is to be understood, however, that the practice of the invention is not limited to this semicircular configuration of the top portion. Other configurations, such as a shallow arc (not shown), a rectilinear arrangement of support purlins (not shown), or a triangular configuration (not shown), can be used in the practice of the invention. As a result of the configuration of upper portion  110 , support element  105  has first and second support terminations. An unobstructed spatial region  108  is formed between the first and second support terminations. 
     The distal ends  106  and  107  of the first and second support terminations comprising upper portion  110  are coupled to respective ones of longitudinal tracks  112  and  114  that, in the installation of a practical embodiment, are arranged to extend in the east/west direction. The distal ends of upper portion  110 , in such a practical embodiment, are directed generally south. 
     As shown in  FIG. 1 , rack arrangement  100  comprises a plurality of support elements that have first and second track structures  112  and  114  attached to the distal ends of the upper Portions  110  of successive support stanchions  102 - 104  to form a frame for engaging and supporting the solar panel array. The figure shows that there are in this specific illustrative embodiment of the invention a plurality of solar panels  121 - 126  installed on longitudinal tracks  112  and  114 . 
       FIG. 2  is a simplified side plan representation of the embodiment of  FIG. 1 . As shown in this figure, upper portion  110  is oriented so as to form a 35° angle relative to a ground plane  130 . As previously noted, upper portion  110  and rails  112  and  114  are permitted to tilt between 5° and 35° in predetermined angular increments, illustratively 5° . This is achieved, in this embodiment by modifying the geometry of coupler  132 , which connects upper portion  110  to support stanchion  102 . 
       FIG. 3  is a simplified side plan representation of a prior art rack arrangement  300 . As seen in this figure, support stanchion  302  is coupled to upper portion  310  by fasteners (not specifically designated) that engage arcuate apertures (not specifically designated). This combination of fasteners and arcuate apertures enables a limited amount of adjustment of the tilt of upper portion  310 . As will become evident hereinbelow, this prior art arrangement is incapable of utilizing the automated drone of the present invention. 
       FIG. 4  is a simplified perspective representation of a manually operated dolly  400  that is useful in the conveyance of solar panels (not shown in this figure) in one embodiment of the invention. Manually operated dolly  400  is shown to have a plurality of wheels  402  that travel along respective ones of longitudinal tracks  112  and  114  (not shown in this figure). There are additionally provided anti-derailment wheel arrangements  404  that prevent the manually operated dolly from leaving the longitudinal tracks, as will be described below. 
       FIG. 5  is a simplified side plan representation of the rack arrangement constructed in accordance with the principles of the invention and showing an advantageous feature of the invention in that manually operated dolly  400 , or an automated drone (not shown in this figure), is able to transport accessories along the rack through unobstructed spatial region  508 , specifically in this embodiment, a cable reel  502 , in addition to a solar panel. The engagement between manually operated dolly  400  and longitudinal track  112  is shown in greater detail in  FIG. 6 . 
       FIG. 6  is an enlarged representation of the identified portion of the embodiment of  FIG. 5 , showing certain features related to the mounting of manually operated dolly  400  on longitudinal track  112  of the rack arrangement. As shown in this figure, wheel  402  communicates with an interior surface of a first elongated portion  116  of track  112 . Anti-derailment wheel  404  communicates with an outside surface of longitudinal track  112  and counteracts any force that would tend to separate the dolly from the longitudinal track. A solar panel (e.g., solar panel  121 ) engages and is supported on a second elongated portion  119  of longitudinal track  112 . As shown best in  FIG. 5 , the dolly, as well as any accessories, can easily travel on track  112  underneath pre-installed panels. 
       FIG. 7  is an enlarged representation of a further portion of the embodiment of  FIG. 5 , distal from the identified portion of  FIG. 6 , showing certain features related to the mounting of the dolly on the rack arrangement as well as an advantageous feature of the invention relating to the location of system cabling  702 . This arrangement enables system cabling or re-cabling to be performed at any time irrespective of whether the array has or has not been populated. 
       FIG. 8  is a simplified perspective schematic representation of a rack arrangement constructed in accordance with the principles of the invention showing a powered drone  802  transporting a solar panel  804  (shown in phantom) along longitudinal tracks  812  and  814  of a rack arrangement  800 . The longitudinal tracks extend parallel to the axis of the elongated array (not specifically designated). Rack arrangement  800  is unlike rack arrangement  100  in that rack arrangement  800  has upper portions  810  that are configure as shallow arcs, rather than complete semicircles. In this embodiment, powered drone  802  travels along longitudinal tracks  812  and  814 , and is engaged therewith, as will be described below. Powered drone  802  of this embodiment is not necessarily fully automated as previously described, and in such embodiments, serves as an assistant to human labor (not shown). 
       FIG. 9  is a simplified perspective representation of the drone  902  that is shown in simplified form in  FIG. 8 . Elements of structure that have previously been discussed are similarly designated. In the embodiment of  FIG. 9 , drone  902  is provided with features of automation that need not be present in every embodiment of the invention. More specifically, drone  902  is an embodiment that is provided with two wheel drive (not shown) that exerts propulsion via selected ones of wheels  903 . Derailment is avoided with the use of an anti-derailment wheel  907 . 
     The drone is shown to have a protective bumper  904  that additionally provides handling points (not specifically designated). In this embodiment, drone  902  has incorporated therein a solar panel lift system  910  that has three positions of actuation, specifically release, lock, and lift. As noted above, in the lift mode, the solar panel (not shown in this figure) is lifted to facilitate travel along the rack arrangement. The lock mode is applied to bring the solar panel into position for securement thereof onto the rack arrangement. The release mode serves to remove the solar panel carrier from engagement with the solar panel. 
     Drone  902  is provided in this embodiment with a docking sensor  915  that serves to avoid collisions. A plurality of other sensors are provided for reading datum marks, and determining the presence of objects or persons in the path of travel. In some embodiments, the sensors are a vision system that has an on board camera (not shown) that collects real time images of the drone&#39;s area of operation. In some embodiments, the image is filtered so as to highlight potential collision objects. Stored within drone  902  are procedures that are effective to stop the travel of drone  902  in response to signals from the sensors or the vision system. 
     It is to be noted that the determination of drone position along the rack is not limited to the reading of datum marks. In some embodiments, GPS or a localized radio beacon are useful in determining the drone&#39;s location. 
     Collisions are avoided in some embodiments of the invention with the use of the vision system. However, other systems and strategies can be used in the practice of the invention. One such system is in the form of a light curtain that consists of a plurality of overlapping lasers and sensors that are placed on both sides of the track (not shown in this figure) to provide a signal responsive to entry into the area of interest by objects or persons. The use of lasers enables detection of objects having dimensions less than 30 mm, resulting in immediate execution of the emergency stop procedures. In addition, in some embodiments, the loss of communication between the light curtain and the drone will trigger the execution of the emergency stop procedures. Emergency stopping requires that the drone be equipped with a braking system, that in its various implementation includes drum brakes, disc brakes, or an other braking arrangement, such as reversing or back driving an electric motor. 
     In some embodiments, safety is enhanced by an ultrasonic sensor, or other form of ranging sensor, that is useful to determine the distance between the drone and interfering objects. When objects are identified to be present in the path of the drone, or within a predetermined distance, the emergency stop procedures are initiated. However, the use of symmetrically disposed sensors reduces incidences of false positives. For example, symmetrical obstructions that trigger the symmetrical sensors simultaneously are ignored, as they represent structural elements of the rack arrangement. Instead, such simultaneous triggering events are counted, in some embodiments, for drone positioning purposes. 
       FIG. 10  is a simplified perspective representation of drone  902  that is shown in  FIG. 9 . Elements of structure that have previously been discussed are similarly designated. This figure depicts the location of collision avoidance ultrasonic sensors  1002 ,  1004 , and  1006 . An upward looking sensor  1008  determines whether a solar panel is present on the drone. In this embodiment, there is additionally provided a sound emitting device  1010  that provides audible warning of the proximity of the drone. 
     The figure additionally shows manually operable operator controls  1015  by which an operator can enter commands manually. These human accessible controls enable an operator (not shown) to control various aspects of the operation of the system. Commands can also be entered in this embodiment with the use of a computer connection panel  1017  that includes USB and other forms of computer interconnection. 
     One or more batteries are stored in this embodiment of the invention behind a battery compartment door  1020 . In some embodiments, there is provided a battery charging system (not shown) that includes any of an internal gas powered DC generator (not shown), or an AC generator (not shown) with an AC to DC converter (not shown). Some embodiments utilize an uninterruptible power supply (UPS) (not shown) that provides continuous power to a control system (not shown). A UPS ensures that stored information is not lost when power is lost, and reduces the start-up time. In some embodiments, power can be delivered via hardwired electrical connection that is deployed as the drone is moved. 
       FIG. 11  is a simplified side plan representation of the drone of  FIGS. 9 and 10  installed on a rack arrangement. Elements of structure that have previously been discussed are similarly designated. In this figure, drone  902  is shown installed on a shallow arc rack arrangement, as described above in connection with  FIG. 8 . 
       FIG. 12  is a simplified partially fragmented perspective representation of an embodiment of a drone  1202 , the figure illustrating the manner in which the drone engages with rack arrangement  1210 . Wheel  1204  of drone  1202  rolls on upper track surface  1212  of rack arrangement  1210 . While wheel  1204  communicates with upper track surface  1212 , an anti-derailment wheel  1206  communicates with the underside (not shown in this figure) of rack arrangement  1210 . A lateral wheel  1208  communicates with the upstanding interior surface (not shown in this figure) of rack arrangement  1210 . The lateral wheel prevents lateral scraping of drone  1202  as it travels along the interior of the rack arrangement. 
       FIG. 12  additionally shows the manner by which some information is transferred from rack arrangement  1210  to drone  1202 . In this specific illustrative embodiment of the invention, rack arrangement  1210  has a datum mark  1214  thereon that is recognized by a sensor  1216  on drone  1202 . 
       FIG. 13  is a simplified schematic representation of a vertical stack loader arrangement  1300  that employs a pusher bar  1302  that feeds solar panels  1310 , in this specific illustrative embodiment of the invention, from beneath. A solar panel  1312  is shown to have been deposited onto the rails  1320  of the rack arrangement (not shown in this figure), which is disposed immediately superior to drone  1325 . The arrow shows that drone  1325  will approach docking station region  1330 , and will then return in the reverse direction to deliver or pick-up a solar panel. 
     Fundamentally, a stack loader arrangement aggregates the solar panels in a form that facilitates loading thereof onto the drone. As such, therefore, it avoids excessive time being spent of the solar panel hand-off, since the next solar panel to be delivered is deposited on the docking station while the drone is installing (deploying) or removing a solar panel from the array (not shown). 
       FIG. 14  is a simplified schematic representation of a vertical stack loader arrangement  1400  that employs a pusher bar  1402  and that feeds solar panels  1410 , in this specific illustrative embodiment of the invention, from above. A solar panel  1312  is shown to have been deposited onto the rails  1420  of the rack arrangement (not shown in this figure), which is disposed immediately superior to drone  1425 . The arrow shows that drone  1425  will approach docking station region  1430 , and will then return in the reverse direction to deliver or pick-up a solar panel. 
       FIG. 15  is a simplified schematic representation of a vertical stack loader arrangement  1500  that feeds solar panels  1510 , in this specific illustrative embodiment of the invention, with the use of a gripper  1502  from above. Gripper  1502  moves up and down to pick up a solar panel, and laterally to deposit solar panel  1512  onto rails  1520  of the rack arrangement (not shown in this figure). When it is desired to depopulate a solar panel array, gripper  1502  pick up solar panel  1512  at docking station region  1530  and deposits it onto the stack  1510 . 
     This figure additionally shows that gripper  1592  will rotate so as to pick up or deposit the solar panels on or from a tilted stack of solar panels, as will be discussed in relation to  FIG. 17 , below. 
       FIG. 16  is a simplified schematic representation of a specific illustrative embodiment of a vertical stack of solar panels  1601 . 
       FIG. 17  is a simplified schematic representation of a specific illustrative embodiment of a stack of solar panels  1701  that has been tilted to facilitate the installation of the solar panels onto, or removal of the solar panels from, the rack arrangement. The angle of the tilt of stack of solar panels  1701  corresponds in some embodiments to the angle of tilt of the solar panels in the solar panel array. 
       FIG. 18  is a graphical representation that illustrates an advantage that is obtained by the use of the present invention, the advantage being presented in terms of solar panels per hour per drone. 
       FIG. 19  is a graphical representation that illustrates an advantage that is obtained by the use of the present invention, the advantage being presented in terms of kilowatts per hour per drone, when used on solar panel modules that have 500 Watt electrical production capacity. 
     In the operation of an embodiment of the invention, certain use assumptions are made. These are: 
     Continuous array (rack) length: 99.125 m 
     Solar panel spacing: 1.625 m 
     Power per solar panel: 500 W (4 each at 125 W assembled) 
     Max drone speed: 4 m/s 
     The following is an analysis of the throughput advantage obtained from the use of the present invention on the installation of N solar panels of width w in an array that is L meters long in a time T. The number of runs corresponding to a trip from the repository of solar panels to the installation point and back that must be made by the drone to populate an array of length L with a panel width w is: 
     
       
         
           
             R 
             = 
             
               L 
               w 
             
           
         
       
     
     The total distance D traveled by the drone in the process of installing the entire array is: 
     
       
         
           
             D 
             = 
             
               
                 L 
                 ⁡ 
                 
                   ( 
                   
                     L 
                     - 
                     w 
                   
                   ) 
                 
               
               w 
             
           
         
       
     
     The total time for the installation T, assuming a panel locking time of t 0 , which constitutes the time required to pick up and unload a solar panel, an acceleration/deceleration time i, and a travel velocity V, is: 
     
       
         
           
             T 
             = 
             
               Rt 
               + 
               
                 Rt 
                 0 
               
               + 
               
                 D 
                 V 
               
             
           
         
       
     
     Solving for V, one obtains: 
     
       
         
           
             V 
             = 
             
               D 
               
                 T 
                 - 
                 Rt 
                 - 
                 
                   R 
                   
                     l 
                     0 
                   
                 
               
             
           
         
       
     
     Finally, the acceleration/deceleration α is derived to be: 
     
       
         
           
             α 
             = 
             
               V 
               t 
             
           
         
       
     
     In the practice of a practicable embodiment of the invention L=99.125 m; w=1.625 m; T=3600 s, and employing reasonable values of 30 seconds to load and unload a solar panel (i.e., t=15 s pickup and 15 s drop-off), and 3 s to achieve maximum velocity (t), one obtains:
         R=61   V=3.75 m/s   D=5947.5 m   α=1.25 m/s 2          

       FIG. 20  is simplified schematic plan representation of a lift arrangement  2000  that is useful for inclusion as a carrier for installing solar panels (not shown in this figure). Lift arrangement  2000  is shown to have a chassis  2002  that in this embodiment is fixedly supported by the drone (not shown in this figure). Lifting is performed by urging lifting element  2004  when it is desired to raise the solar panel (not shown in this figure). Lifting element  2004  is raised in response to urging by lift actuator  2006 , which receives its actuation energy from a drive arrangement  2010 . As lifting element is raised and lowered, it maintains a substantially parallel relation to the chassis by operation of guides  2011 . 
     In this embodiment, rain that might enter drive arrangement  2010  is allowed to drain through drain pipe  2012 . 
     There is additionally shown in this figure a pair of grippers  2015  and  2017  that function to lock, hold and release the solar panel in response to actuation. 
       FIGS. 21( a ), 21( b ), 21( c ), and 21( d )  show respective illustrative 180° arc, shallow arc, raised purlins, and triangular configurations that can be used in respective embodiments of top portions of the rack arrangement of the present invention. In light of the teaching herein, persons of skill in the art can configure the dimensions of these illustrative configurations to accommodate the passage of a drone therewithin, as well as accessories that would depend from the drone. 
     Although the invention has been described in terms of specific embodiments and applications, persons skilled in the art can, in light of this teaching, generate additional embodiments without exceeding the scope or departing from the spirit of the invention described and claimed herein. Accordingly, it is to be understood that the drawing and description in this disclosure are proffered to facilitate comprehension of the invention, and should not be construed to limit the scope thereof.