US20130000632A1

US20130000632A1 - Sun tracking solar power collection system

Info

Publication number: US20130000632A1
Application number: US13/067,862
Authority: US
Inventors: Robert D. Lundahl; Robert Cutlip
Original assignee: Advanced Technology and Research Corp
Current assignee: Advanced Technology and Research Corp
Priority date: 2011-06-29
Filing date: 2011-06-29
Publication date: 2013-01-03
Also published as: WO2013003737A3; WO2013003737A2

Abstract

This invention presents a unique design for a sun tracking, solar panel mounting system that is intended to be mounted onto utility light poles, wind turbine poles, and other pole type structures. Rings are clamped around the pole and form a structural interface to support the tracking mount assembly and allow it to rotate around the centerline of the pole. An actuator powers the tracking structure rotate right or left around the centerline of the pole. A secondary structure in the mount assembly supports solar panels on either side of the vertical mounting poll and an optional second actuator tilts the elevation solar panels up and down. A control system reads the position of each actuator and periodically adjusts them to track the motion of the sun and optimize the solar energy collection efficiency.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to solar energy electrical power collection systems and specifically to the design of a solar panel mounting system that is mounted on pole structures and tracks the movement of the sun with a single or dual axis motion and programmable control.
Utility poles for lighting, power, communications, and wind turbines are prevalent in today's landscape. They are existing industrial structures that can be utilized to support solar panels and they also provide convenient access to the local power grid. These are attractive features for solar power collection systems as part of a distributed generation system. Using existing poles for a mounting structure greatly reduces the cost to install the solar panels and no additional real estate is required. Utilizing existing poles also provides an easy access to the electrical grid so that power produced by the solar panels does not need to be stored but can be “sold” back to the grid for others to use. Utilizing wind turbine poles in particular provides a Hybrid energy collection system that utilizes both wind and solar energy and can provide power more often than either source alone.
This invention presents a detailed approach for the design of sun tracking solar panel mounting system that is easily attached to different pole including light poles, wind turbine support poles, standard utility poles. This design is unique in its ability to be mounted at an intermediate position on the pole and it can be retrofit onto a wide variety of existing poles. The design of this tracking system allows it to share a pole with a wind turbine, streetlight, or a utility pole with overhead wiring.
Powered actuator(s) and a control system are integrated within the mount structure to actively rotate the solar panels around the vertical axis of the pole to track the sun and maximize the daily power production. A simple single axis tracking system can be configured with the solar panels are held at a fixed inclination and the entire array is rotated around the vertical axis of the pole to track the sun in azimuth. An even more efficient dual axis tracking system can be configured where the inclination of the solar array is also changed during the day to track the sun in azimuth and elevation.
The principal application for this invention is to configure highly efficient power generation systems on existing light poles, wind turbine poles, utility poles, and other common outdoor pole structures. However, it should be obvious to one skilled in the art that this tracking mount system could be used on any pole type structure as well as utilized for a variety of other tracking or pointing applications of other antennas, cameras, etc.
2. Brief Description of Prior Art
Pole mounting systems are prevalent in prior art. However, most are for static mounting. U.S. Pat. No. 4,265,422 shows a widely used approach for statically mounting a solar panel onto pole type structures to power local electronic systems. The mounting technique uses “U” bolts to encircle the pole and attach the solar panel mounting structure. This mounting technique is easy to use on existing poles since it is not necessary to modify or drill into the structure of the pole and it's also not necessary to put it over the top of the pole where there could be a variety of existing power cables or other appendages. This type of mounting system is static and does not move the solar panel to track the sun. The power generated by a non-tracking panel is 30 to 40% less than what can be gained from a sun tracking panel. Most of these applications are designed simply to power a local electronic system and the loss of efficiency is addressed by over sizing the panels for the local requirement. This would not be an effective approach if the purpose was to generate excess electrical power to be fed back into the electrical grid.
Tracking pole mounted systems are also found in prior art. However, these systems are designed to be mounted on top of a pole structure. U.S. Pat. No. 1,111,111 shows a common top mounted tracking system and these are available in both single axis and dual axis tracking configuration.
These mounting systems incorporate the sun tracking function and generate more power than the non-tracking panels. However, the mechanical system to provide the 2 axis motion requires the mechanism to be mounted on top of the pole structure. This approach does not lend itself for retrofitting onto existing utility poles and it would also be impossible to use on a wind turbine pole where the top of the pole is occupied by the turbine itself. This design limits the potential installation sites.
These top mounted configurations cannot be easily mounted to the midsection of the pole where there is adequate area and access. The structure and drive mechanism of these top mounted poles systems are not designed to encircle the pole. It would be difficult or impossible to slip the mechanism over the top of the pole and slide it down into a middle position.
These types of mounting systems can only be installed on the tops of the poles and this is not a convenient location for installation or maintenance and it would be impossible to use on a pole that is supporting a wind turbine.

SUMMARY OF THE INVENTION

This invention describes a sun tracking mount for a solar power generation system designed to be mounted on vertical poles. Two rings are installed on the pole and provide upper and lower bearing races for the powered tracking module. The tracking module incorporates another bearing surface or rollers to interface with the bearing races of the rings and allow the tracking module to smoothly rotate around the center line of the pole. The tracking module is constructed in two halves so that the module can opened up, positioned around the pole, and then closed to capture the bearing races around the pole. The tracking module incorporates a horizontal structure to support an array of solar panel(s) at a on either side of the pole.
The basic tracking module can be configured as a 1 axis tracking system or a 2 axis tracking system.
For 1 axis tracking, a primary 1^staxis drive motor is positioned on the tracking module and connected by a drive chain to a sprocket that is fixed around the pole. When this motor is activated it will rotate the entire tacking module around the centerline of the mounting pole providing a single rotational axis. This is called 1 axis motion and it is used to rotate the solar array and track the sun's position in Azimuth only. For 1 axis configurations, the inclination of the solar panels is fixed.
For 2 axis tracking, a second drive motor is added to actively change the inclination of the solar panels. This motion combined with the rotational movement of the tracker module allows the complete tracking of the sun in azimuth and in elevation for the maximum power generation efficiency.
The solar panels are positioned on either side of the support pole providing them un-restricted freedom of motion to rotate around the pole and change elevation to perfectly track the suns position. The shadow from the pole is always between the panels and will not degrade their performance.
The tracking module supports the solar panels in a balanced position to minimize any moment loads to the mounting pole structure. Panels are positioned on either side of the pole as a balanced load. The panels themselves are connected to the horizontal cross arm structure close to their center of gravity so they maintain a balanced configuration regardless as they change their pointing elevation as they track the path of the sun.
The solar panels generate DC voltage. A small amount of power is used by the positioning motor(s) and some energy is stored for end-of-day repositioning. The majority of the energy produced will be converted to AC power and fed back to the utility electrical grid with a “grid tied” inverter. A grid tied inverter matches the frequency of the generated AC power with the frequency of the local electrical grid so that excess power can be fed directly to the local power grid for credit or outright sale as an independently produced power.

OBJECT OF THE INVENTION

This invention presents the design for a sun tracking solar panel mount designed to be easily installed on a variety of pole structures used for street lighting, wind turbines, power transmission, signage, and other supports.
A further object of this design is to provide mounting system that can easily accommodate different size and shaped poles.
A further object of this design is to provide mounting system that can easily be retrofitted onto existing poles.
A further object of this is to provide mounting system can be used specifically for wind turbine poles where access to the top of the poles for installation is not possible.
A further object of this invention is to provide a means for a cost effective installation solar installation.
A further object of this invention is to provide an installation location for the solar panels that is easily accessible to the existing electrical grid.
A further object of this invention is to provide an installation location for the solar panels that are easily accessible by service personnel and equipment.
A further object of this invention is to provide a pointing control system that is based on microprocessor control.
A further object of this invention is to provide an automated method to coordinate the movement of the device to correctly track the sun from any geographical location.
A further object of this invention is to provide a means to reduce the wind load from the installed PV panels.

BRIEF DESCRIPTION OF DRAWINGS

FIG. (1) Pole mounted sun tracking solar panel mount—This illustration shows an overview of the sun tracking mount installed on a light pole.

FIG. (2) Split bearing interface with the mounting pole—This illustration shows how split bearing clamps are used to attach the tracking mount to the mounting pole.

FIG. (3) Captured tracking mount—This illustration shows how the mount structure is attached to the mounting pole and captures the bearing interface.

FIG. (4) Tracking mount installed on mounting pole—This illustration shows how the tracking mount is installed on the mounting pole and how the actuators mechanically provide the axis of motion for the solar panels.

FIG. (5) Position control system—This illustration shows one embodiment of a microprocessor based position controls system for sun tracking.

FIG. (6) Utility Grid Interface—This illustration shows one embodiment of how the generated power can be interfaced with the utility grid.

FIG. (7) General daily motion profile—This illustration shows a general motion profile for the movement of the tracking mount and the solar panels.

FIG. (8) Fixed mount wind load reduction—This illustration show a method to mount the solar panels to reduce the wind loading for most wind directions.

FIG. (9) Passive compliant wind load reduction—This illustration shows how the panels can be mounted with a spring loaded pivot to allow relief for excessive wind pressure.

FIG. (10) Active wind load reduction—This illustration shows how the orientation of the solar panels can be changed to reduce the anticipated wind loading from a variety of information sources.

FIG. (11) Active wind load reduction—This illustration shows different ways that the surface area of the solar panels can be utilized for advertising graphics.

FIG. (12) Tracking mount installed on wind turbine pole—This illustrations shows an overview of the sun tracking mount installed on a wind turbine pole to form a hybrid power generation system.

DETAILED DESCRIPTION OF THE INVENTION

The following sections describe the invention where the application is for mounting a solar panel tracking system onto light poles and wind turbine support poles. It should be obvious that this invention can also be utilized as a simple and robust method for building a sun tracking solar collection system on practically any pole structure including a single purpose pole dedicated to the mounting of the solar panel. Similarly this invention could also be applied to a variety of different pointing applications for antennas or other optical systems.
FIG. (1) Pole mounted sun tracking solar panel mount—This illustration shows an the pole mounted sun tracking solar panel mount installed on a utility light pole. Using an existing light pole provides a cost effective approach for mounting the solar power collection system. The abundance of existing lighting fixtures provides immediately available installation sites. Existing utility light polls provide an easy access to the local electrical power grid since they are already connected and currently serviced by service personnel and equipment.
In this illustration the tracking mount (100) is shown mounted to the mid section of a conventional light pole (200). Connecting arms (300) on either side of the tracking mount (100) connect to solar panels (400) on either side. To track the sun, the tracking mount (100) provides the solar panels (400) with either one or two axis of motion. For East to West tracking the tracking mount (100) itself will rotate about the centerline of the light pole (200) in the horizontal plane of rotation (500) for 1 axis tracking. To track the sun in elevation above the horizon, the connecting arms (300) of the tracking mount (100) will rotate around their centerline and in the vertical plane of rotation (600) providing a 2^ndaxis of tracking.
FIG. (2) Split bearing interface with mounting pole—This illustration shows how a split clamping ring (700) can be used to encircle the pole (800) and provide a bearing surface (1000) for the tracking mount to rotate around the pole. The split clamping ring approach allows this mounting interface to be clamped around an existing pole where it may not be practical to access the top of the pole or otherwise attach a mounting structure. In the illustration the split clamping rings (700) are secured around the pole structure (800) with screws (900) or other means to clamp the sections securely around the mounting pole diameter. Some larger diameter poles may utilize several separate clamping ring (700) sections to encircle the pole. An upper and lower bearing surface (1000) would be typically installed on the pole structure to provide a structural interface. Clamping rings can be manufactured with a wide variety of bore sizes and inside diameter configurations to match the size and profile of the installation poles and still maintain a consistent bearing surface (1000) for the tracking mount interface itself. It may also be desirable to manufacture separate internal diameter inserts to further increase the adaptability of the split bearings to an even wider range of utility poles. It is also envisioned that new utility poles could be designed and constructed with attachment provisions for the split clamping rings where they could be individually attached and collectively form the bearing surface (1000) when all of the split clamping rings were installed. This would provide a “built in” feature to mount the tracking mount system.
FIG. (3) Captured tracking mount—This illustration shows how the front panel (1100) of the tracking mount (1200) is removable and installed from the opposite side of the mounting pole (1300). Rollers (1400) or other bearing features mounted on the front panel (1100) and within the tracking mount (1200) interface with the split bearings (1500) and provide the structural and rotational interface between the tracking mount (1200) and the mounting pole (1300). Many different roller and bearing configurations can be envisioned to provide the structural and rotational interfaces required within the spirit of this invention.
FIG. (4) Tracking mount installed on pole—This illustration shows the tracking mount as installed on a mounting pole. The tracking mount (1600) encircles and captures the mounting pole (1700). In this embodiment, an array of rollers (1800) mounted inside the front cover (1900) and main body of the tracking mount (1600) interfaces with the bearing surface (2000) of the split bearings (2100). If full 2 axis tracking is used, a linear actuator (2200) is installed between the structure of the tracking mount and the rotating sleeve (2300). Extension or retraction of the linear actuator (2200) will rotate the sleeve member (2300) that supports the solar panels and thereby adjust the pointing elevation of the solar panel. The conventional 1 axis tracking is performed by the azimuth drive motor (2400) which is attached to the tracking mount (1600) and powers a belt drive (2500) or other similar drive train connected to the lower split bearing (2600). Activation of the azimuth drive motor (2400) will cause the tracking mount (1600) to rotate horizontally about the mounting pole (1700). Many different actuator and drive configurations for the azimuth and elevations drives are possible and anticipated by this invention. The preferred embodiment described here is one approach that is simple and low cost using off the shelf components.
FIG. (5) Position control system—This illustration shows the position control system for the tracking panel mount show 2 axis tracking in both azimuth and elevation. Single axis tracking may be used to save cost and complexity in which case only the azimuth pointing axis would be controlled. A microprocessor (2700) is used to control the elevation motor (2800) and the azimuth motor (2900) by providing them with DC voltages through elevation relay (3000) and azimuth relay (3100) respectively. Voltages can be reversed to enable bi-directional movement. Both motors incorporate position feedback. The elevation motor encoder (3200) and the azimuth motor encoder (3300) communicate their positions to the microprocessor (2700).
A Global Position System (GPS) (3400) and GPS antenna (3500) determine the Latitude and Longitude of the current position and also communicate the current date and time.
Sun tracking is accomplished by the microprocessor (2700) calculating the relative position of the sun and coordinating the positions of both the elevation motor (2800) and the azimuth motor (2900).
The position of the solar panels is updated on a pre-set time interval. The interval is chosen to optimize the overall efficiency that is a function of pointing accuracy and the power required for the frequency of re-positioning.
Many different approaches can be used to accomplish the actual positioning function and they are anticipated by this invention. The preferred embodiment described above presents an automated solution where the sun positions are calculated based on Date, time of day, and the latitude and longitude of the installation location. However, a much simpler solution can be envisioned where the positions are “pre-programmed” and stored in a look up table for each of the update intervals.
For simplicity it is assumed that the installers would correctly orient the system North and South and this position would be used for initialization. A more automated approach can be envisioned where an electronic compass is used to determine the North and South orientation of the unit after it is installed and the internal coordinates of the control system would be updated automatically upon initialization.
The Solar panel (3600) generates DC voltage for the Grid Tie inverter (3700) that converts it to AC voltage for delivery back to the utility power grid (3800). A small portion of the power generated is used to trickle charge an on board battery or other power storage device (3900). This battery or power storage device (3900) provides power to operate the azimuth and elevation (if used) drive motors as well as the microprocessor (2700) and the GPS unit (3400) during periods of no sun or at the end of the day when the solar panels (3600) are repositioned from the direction of the setting sun to the direction of the rising sun for the following sunrise.
FIG. (6) shows how the generated power can be provided to the grid—Providing excess electrical power to the grid for others to use is the primary purpose of this invention. FIG. 6 shows one of the basic configurations for delivering electrical power to the grid. Other variations are anticipated and within the scope of this invention. The tracking solar panel system (4000) is shown attached to a utility light pole (4100) that is connected to a Utility Pole AC Power (4200) line. Generated solar panel DC power (4300) is delivered to a grid tied inverter (4400) where it is converted to AC power that is in sync with the utility pole AC power (4200).
Many different “Grid Tied” inverters are commercially available and incorporate different features. The basic functionality of an inverter is to convert DC power into AC power. The grid tied inverters are a special configuration that will “sense” the phase of the utility line and match the phase of the converted AC power so that it can be directly connected. As a safety provision grid tied inverters will stop producing AC power if the utility line loses power or frequency.
Synchronous AC power can be provided to the AC power grid through a separate metering system (4500) to log how much power has been provided to the grid for the purposes of reverse billing.
Several of the commercially available grid tie inverters (4400) also provide data over the utility AC power (4200) for a smart grid interface (4600) component to report on solar panel health, power output and other performance metrics. The smart grid interface (4600) devices can be connected to the internet (4700) to report solar performance metrics into a database that is accessible over the internet for a variety of monitoring and control functions that can be performed remotely over the world wide web. This type of utility could be used to supervise, monitor, and manage a large installed base of solar panel systems (4000) spread out over a large geographical area.
FIG. (7) shows a general daily motion profile of a 2 axis system—Many different motion profiles can be programmed for the daily sun tracking function and stow positions can be incorporated for the nighttime, high wind, snow, or other conditions. Both single and dual axis system can be configured. In the morning a dual axis system will position the solar panels to the sunrise position (4800) before the sun rises. Here the solar panels (4900) are positioned close to vertical and turned to face the sunrise position. As the sun travels along its path (5000), both the azimuth and elevation of the solar panels (4900) are periodically adjusted to face the sun. At the mid day position (5100) the solar panels (4900) have their maximum vertical elevation of the day and they are facing due south. At the end of the day position (5200) the solar panels (4900) are once again nearly vertical and facing the sunset in the West. For night time storage the panels are re-positioned to face the rising sun for the next day and then the cycle will repeat itself. Other storage positions are possible for the night time or adverse weather conditions. It may be desirable to stow the panels in the horizontal position to avoid the excess wind loading that could happen overnight.
The motion profiles for a single axis system is much simpler where the panels are at a fixed inclination and the mount is only rotated throughout the day to the azimuth of the sun.
FIG. (8) Passive wind load reduction—This illustration shows how the solar panels are mounted on the support structure with an offset pattern designed to reduce the wind loading by providing gaps between panel sections. A tubular support structure (5300) provides the mating connection to the rotating mount and supports the side frames (5400) where the solar panels (5500) are attached. The solar panels (5500) are attached to the side frames (5400) with a staggered pattern that creates open panel gaps (5600) between each of the panel sections. These gaps provide a wind relief passage to decrease the overall wind loading on the panel and mounting structure. Many different gap configurations are possible and anticipated by this invention
FIG. (9) Compliant wind load reduction—This illustration shows how a mounting structure can provide passive compliance for each of the panels to relieve over pressure and decrease the overall wind loading forces. With this approach the mounting frame (5700) supports pivot rods (5800) for each of the solar panels (5900). The hinged pivot rods (5800) are located off center on the solar panels (5900) and they are spring loaded so that they seek a center of rotation where all of the panels lay flat in a common plane with the mounting frame (5700).
Wind causes pressure on the solar panels (5900) with a center of force that is offset from the centerline of the pivot rod (5800). At low wind levels (6000) the force on the solar panels (5900) is not sufficient to cause them to rotate against the spring loaded pivot rods (5800). However, excessive wind speeds (6100) will create sufficient force to overcome the spring loaded pivot rod (5800), causing rotation about the pivot rod (6200). This rotation of the solar panel (5900) will decreasing its apparent surface area and limit the force of the wind on the panel array to an acceptable level.
FIG. (10) Active wind load reduction—This illustration shows how a 2 axis tracking mount could actively re-orient the panels to a horizontal position to reduce wind loading effects. When the solar panels are in a normal position (6300) their surface area may be perpendicular to the apparent wind direction (6400). In this position the wind forces could be significant. To reduce these forces the solar panels can be re-positioned into a horizontal stow position (6500) where there is very little surface area exposed to the apparent wind direction (6400) and the wind loading is greatly reduced. Positioning of the solar panels is performed by the microprocessor based controller and many different control inputs are possible and anticipated to signal the microprocessor to re-position the solar panels into a horizontal or “stow” position (6500). Strain gages, pressure sensors, wind speed gages, or external RF could be used to trigger the mounting system to move the panels into received to command the panels move to safe position.
FIG. (11) Utilization of available surface area for advertising—This illustration shows how the available surface area could be used for advertising to help offset the costs of the solar power generation system. Solar power generation has a marginal economic rate of return with current technology and associated costs. Utilization of the available surface area for advertising will provide an attractive source for additional revenue. The solar panels could have underside graphics (6600) applied to form an interesting visual display for a variety of commercial enterprise.
To accommodate the needs of different advertising customers, graphic panels (6700) could be inserted into holder frames (6800) that could be easily changed out for periodic updates.
Front surface graphics (6900) could also be applied directly to the face of the solar panels using standard techniques for “see through” images, however care would be required to minimize any associated decrease in solar panel's performance.
FIG. (12) Wind Turbine Pole mounted sun tracking solar panel mount—This illustration shows the sun tracking solar panel mount installed on a wind turbine pole. Co-locating a tracking solar panel on a wind turbine pole provides a cost effective “hybrid” system that can effectively harvest 2 different sources of energy, wind and solar. Power generated by both of these systems can be combined for use or storage.
In this illustration the sun tracking mount and solar panels (7000) is shown mounted to the mid section of a wind turbine mounting pole (7100). The wind turbine (7200) is positioned at the top of the support tower

Claims

1. A solar energy collection system comprised of

a mount

where said mount rotates around the centerline of the pole and,

where said mount mechanically captures said pole and does not have to be installed over either end of said pole and,

where said rotation utilizes a bearing race that is attached to the mounting pole and,

said rotation utilizes a motor,

where said motor is under numerical computer control, and

a solar panel(s)

where said solar panels are mounted to the side of said pole and

where said solar panels can be rotated vertically and,

where in said rotation is performed by a motor and,

where said motor is under numerical computer control, and

a control system

where said control system utilizes a microprocessor and software controls and,

where software controls periodically update the position of the solar panel to track the sun.

2. A Solar energy Collection system in accordance with claim 1 where the control system moves the panel based on sensor inputs.

3. A Solar energy collection system in accordance with claims 1 and 2 where excess electrical power is stored in batteries.

4. A Solar energy collection system in accordance with claims 1 and 2 where excess electrical power is converted to AC power and fed back into the electrical grid.

5. A Solar energy collection system in accordance with claims 1 and 2 where excess electrical power is provided to another energy storage device.

6. A solar energy collection system comprised of

a mount

where said mount rotates around the centerline of the pole and,

said rotation utilizes a motor,

where said motor is under numerical computer control, and

a solar panel(s)

where said solar panels are mounted to the side of said pole and

where said solar panels are mounted at a fixed elevation angle

a control system

where said control system utilizes a microprocessor and software controls and,

7. A Solar energy Collection system in accordance with claim 6 where the control system moves the panel based on sensor inputs.

8. A Solar energy collection system in accordance with claims 6 and 7 where excess electrical power is stored in batteries.

9. A Solar energy collection system in accordance with claims 6 and 7 where excess electrical power is converted to AC power and fed back into the electrical grid.

10. A Solar energy collection system in accordance with claims 6 and 7 where excess electrical power is provided to another energy storage device.

11. A Solar energy Collection system in accordance with claims 1 and 6 where the solar panels are allowed to pivot and relieve excessive wind load forces.

12. A Solar energy Collection system in accordance with claims 1 and 6 where the surface area of the solar panels and support frame are outfitted with graphics for promotional purposes.

13. A Solar Energy Collection System in accordance with claims 1 and 6 where said pole is the vertical support pole for the wind power turbine.