US20090188488A1

US20090188488A1 - Wireless mesh networking of solar tracking devices

Info

Publication number: US20090188488A1
Application number: US12/021,040
Authority: US
Inventors: Steven Michael Kraft; Jason Charles Jones
Original assignee: TILT SOLAR LLC
Current assignee: SunPower Corp
Priority date: 2008-01-28
Filing date: 2008-01-28
Publication date: 2009-07-30

Abstract

An apparatus for networking solar tracking devices 32. The system includes one or more solar tracking devices 32, each comprising tracking controller 16. Tracking controllers 16 form wireless mesh communications network 18 managed by network manager 14. Tracking controller 16 receives operating data from and sends monitoring data to host computer 10. This operation and monitoring data travels across wireless communications network 18. Host computer 10 connects to wireless mesh communications network 18 either directly or via any communication channel 12 connected to any node on wireless mesh communications network 18.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates in general to the field of solar tracking, more particularly to the operation and monitoring of the control systems that orient objects (e.g. solar cells and solar concentrators) with respect to the sun.
2. Prior Art
Companies and municipalities have for many years been burdened with the expensive and cumbersome task of operating and monitoring control systems for solar tracking devices. Solar tracking devices are used to orient solar cells, solar concentrators, or other devices such as testing apparatuses with respect to the sun. The control systems for these solar tracking devices comprise a significant number of sensors, actuators, and algorithms, along with associated wiring, enclosure(s), and power transforming devices. In order to effectively and efficiently operate and maintain a facility containing controlled solar tracking devices, the facility operator must send information to and receive information from the control systems for the tracking devices. This has traditionally been done manually, and more recently been improved with both point to point and multi-drop wired networks. These historical approaches are becoming less viable as more facilities contain solar tracking devices, as larger facilities containing solar tracking devices are built, and as these facilities are built in more remote locations.
The traditional method for monitoring and operating control systems for solar tracking devices has been to have a human operator go to the location of the control system. Many systems are still monitored and operated in this fashion, including the Wattsun products manufactured by Array Technologies Inc. (www.wattsun.con), the SunDog controller manufactured by InSpira S.L. (www.inspira.es), and the SolarTrak from Enhancement Electronics, Inc. (www.tapthesun.com). In all of these solar tracking controllers, and in other competing products, the operator must go to the location of the control system to determine the state of some sensor, actuator, or algorithm. This process is costly, time consuming, and error prone. It also can involve various risks to the operator through exposure to weather, dangerous voltages and currents both inside and outside of the control system enclosure, and other environmental exposures. Further, if these manually obtained readings are to be stored in a database, they must be manually transferred, a process highly susceptible to error.
Recently, wired network systems to monitor and operate control systems for solar tracking devices have been developed. Controllers for solar tracking devices using wired networks are provided by Solon AG (www.solonmover.com) and Soltec Renewable Energy (www.soltec-renovables.coa), among others. These wired networks reduce personnel exposure and manual entry of data associated with manual operation and monitoring. However, these wired networks suffer from other problems. They require cables that connect the tracking controllers to one or more operation and monitoring computers, and in daisy-chain topology networks these cables connect the control systems together, as well. These cables bring with them cost (e.g. cost of the cables themselves and the cost of burial and/or conduit) and reliability problems (e.g. when the cables are disrupted) associated with field wiring. Disadvantageously, these network systems in most cases electrically connect the tracking controllers with other electronics, making them more susceptible to grounding problems and lightning strikes. These cost and reliability problems worsen as more tracking controllers are located on a single site, as with a solar electric power plant comprising a plurality of solar collectors.
A variation of this wired networking topology includes using the power line as a carrier medium. This approach connects the control systems to one or more operation and monitoring computers through the power lines and transmits the sensor, actuator, and algorithm information across these power lines. This removes the cost of separate network cables across which the control systems send and receive data. This approach, however, can require a complicated infrastructure to be installed. Power lines operate as very large antennas and can receive a large amount of noise. Therefore, signal-cleaning filters must be installed periodically along the power lines to attenuate the noise. These filters can be very expensive. Also, the connections often are at line voltage, making it more dangerous and time consuming to install, as well as more difficult to certify with agencies such as CE and UL. Finally, power line communication is blocked by transformers, so use of this communication technology complicates the power distribution design at facilities such as solar electric power plants.
More recently, wireless networks to monitor and operate control systems for solar tracking devices have been developed. These networks are typically installed in a star topology. In these conventional wireless networks using a star topology, each control system in an installation must communicate with a base station (a.k.a. access point). This becomes problematic on all but the smallest installations, because the range of conventional wireless data networks of this type is highly limited. This causes systems to require repeaters to be placed within an installation to extend the communication range of the control systems. This problem is exacerbated by systems placed in a landscape that is not flat or has obstructions like trees or buildings.
Yet another communication methodology for monitoring and operating control systems for solar tracking devices includes the use of small radio frequency (RF) transmitters. Because systems having sufficient range normally are subject to regulations and licensing requirements that are prohibitively expensive, centralized wireless control systems for locally distributed devices using RF transmitters have not been widely utilized. Also, systems that are sufficiently powerful to be used in widely distributed installations are unnecessarily expensive in smaller installations. Additionally, there is limited availability of RF carrier frequencies and potential interference with other nearby systems that might be operational.
Lack of a network for solar tracking controllers with suitable characteristics (e.g. inexpensive to install, inexpensive to maintain, reliable) has caused secondary disadvantages, as well. Following are descriptions of some of these disadvantages.

- 1) It is well know that in order to calculate the position of the sun in the sky, it is necessary to know the date and time at the site where the observer is located. Hence, at installations comprising a plurality of tracking controllers, it would be advantageous to determine the date and time of day from a single GPS unit or other source for this information (for instance the Internet's Network Time Protocol, NTP), and propagate this information over a network, reducing the number of sensors at an installation. Lacking suitable network technology, recent art advocates placing a GPS in each tracking controller (reference U.S. Pat. No. 6,680,693). Installation of these devices in each tracking controller increases the cost and decreases the reliability of the entire installation.
- 2) It is well know that in order to calculate the position of the sun in the sky, it is necessary to know the latitude and longitude at the site where the observer is located. Hence, at installations comprising a plurality of tracking controllers, it would be advantageous to determine the absolute latitude and longitude at some single point at an installation, then combine this absolute location information with relative latitude and longitude information for each tracking controller (obtained, for example, from as-built drawings), and propagate this information over a network, reducing the number of sensors at an installation. Lacking suitable network technology, recent art advocates the more expensive and less reliable solution of placing a GPS in each tracking controller (again, reference U.S. Pat. No. 6,680,693) for this purpose.
- 3) Site environmental conditions are often used in the control of solar tracking devices. For instance, solar tracking devices often have features that allow them to orient their payloads to positions that reduce wind loads on the structure when high winds are detected. Lack of suitable network technology causes recent art to advocate placement of environmental monitoring sensors (e.g. wind sensors or temperature sensors) at each tracking controller, increasing cost and decreasing reliability.
- 4) Communication between tracking controllers would be useful in many instances to optimize operation of an entire facility. For instance, inter-device shading might be used as a factor in the control of solar tracking devices if suitable network technology existed.
- 5) Modern tracking controllers are complicated, computer controlled devices comprising a significant amount of control software. Bug fixes or feature upgrades require manual software upgrade in systems currently considered state of the art (e.g. reference page 26 in http://www.tapthesun.com/PDF/SolarTrak-PCInterface Software Manual Rev 01.pdf). This manual software upgrade can be very error prone and labor intensive on large installations, when significant numbers of tracking controllers located significant distances apart are involved.

In view of the foregoing, Applicant has recognized a need to transform the process of monitoring and operating control systems for solar tracking devices, while reducing costs, adding value, and enhancing service. Additionally, Applicant has recognized a need for technology to reduce costs and improve reliability in systems containing two or more solar tracking controllers by removing redundant sensors and algorithms.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, embodiments of the present invention advantageously provide an apparatus for wireless mesh networking of solar tracking devices. These embodiments provide bi-directional communication from a host computer to solar tracking controllers that allows control and status information to be exchanged between the host and the solar tracking controllers. This bi-directional communication allows status information from actuators, sensors, and algorithms located in a plurality of solar tracking controllers to be available to the operator of the system at a single host computer. In addition, this bi-directional communication provides the operator functional control over the solar tracking devices from this same host computer. Embodiments of the present invention advantageously provide a distributed network system that allow status from a plurality of tracking controllers to be monitored and analyzed, and also advantageously allows site specific information (e.g. date and time) to be propagated to all or some plurality of the tracking controllers.
The foregoing summary is not intended to summarize each potential embodiment, or every aspect of the invention disclosed herein, but merely to summarize some aspects of the present invention, among others.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

So that the manner in which the features and advantages of the invention, as well as others which will become apparent are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only an embodiment of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.

FIG. 1 illustrates a site comprising a plurality of solar tracking devices;

FIG. 2 illustrates a solar tracking device in accordance with the present invention;

FIG. 3 illustrates the communication paths available in the first embodiment of the present invention;

FIG. 4 is a representational view of the first embodiment of the present invention;

FIG. 5 schematically illustrates components of the first embodiment;

FIG. 6 illustrates a form of the wireless mesh communications network of the present invention;

FIG. 7 is a representational view of the second embodiment of the present invention; and

FIG. 8 schematically illustrates components of the second embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which illustrate embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. The prime notation, if used, indicates similar elements in alternative embodiments.
Referring to FIG. 1, a site is shown that would be suitable for use of the wireless mesh communications network of this invention. This site contains more than one of a solar tracking device 32. Tracking device 32 comprises actuators, sensors, mechanisms, and computing. Tracking device 32 is used to orient a tracking payload 30 with respect to the sun 70 (and hence the electromagnetic radiation 72 incident from sun 70).
Referring to FIG. 2, solar tracking device 32 is shown, on which is mounted a tracking controller 16. Tracking controller 16 is responsible for computing both the position of sun 70 and the desired orientation of tracking payload 30 based on variables such as date, time, latitude, and longitude. Based on the results of these calculations, tracking controller 16 can control actuators of tracking device 32 (possibly using sensors of tracking device 32 for this task). In this first embodiment, tracking payload 30 is shown as an array of solar panels.
Referring to FIG. 3, the data communication paths available in the first embodiment are shown. A host computer 10 communicates via communication channel 12 to host gateway 58. Host gateway 58 in turn communicates with network manager 14. Finally, network manager 14 communicates with tracking controller 16 via a wireless mesh communications network 18. In this first embodiment, base station 56 houses both host gateway 58 and network manager 14.
Referring to FIG. 4, representational view of the first embodiment of the present invention is shown. The site comprises a plurality of tracking devices 32. In this embodiment of the invention, host computer 10 is located within an operation and monitoring center 64. A base station 56 provides both host gateway 58 and network manager 14. Base station 56 is housed at an equipment shed 62. A plurality of tracking controller 16 are in communication with host computer 10, with the communicated information traveling across wireless mesh communications network 18. In the first embodiment, the communication path from tracking controller 16 to host computer 10 will pass over zero or more of a wireless hop 74. Communication channel 12 between a host gateway 58 and host computer 10 may be any suitable communication mechanism, or combination of communication mechanisms, either wired or wireless. The only limitation on the location of base station 56 in this embodiment is that it must be in radio transmission range of at least one, but preferably more than one, tracking controller 16. There is no limitation on the location of operation and monitoring center 64.
Referring to FIG. 5, components of the first embodiment are schematically illustrated. Operation and monitoring center 64 contains host computer 10. Host computer 10 contains a processor 54 that provides the computing services for an operator interface program 50 and a database 52. As shown in this embodiment, operator interface program 50 and database 52 are executing on processor 54, which is a single CPU. Alternative embodiments may have multiple CPUs, in multiple physical locations, each providing some of the compute service required of processor 54. Alternative embodiments may have operator interface program 50 and/or database 52 spread across different physical locations. For instance, at a solar electric plant operated by one organization and maintained by another, parts of database 52 and parts of operator interface program 50 could run at two different sites.
In the first embodiment of the invention, base station 56 comprises network manager 14 and host gateway 58. Host gateway 58 comprises a processor 68 and a transceiver 48 that is compatible with communication channel 12. Network manager comprises a processor 66 and a wireless network transceiver 46 compatible with wireless mesh communications network 18.
Tracking device 32 comprises tracking controller 16 that is connected to wireless mesh communications network 18, organized and maintained by network manager 14. Tracking controller 16 contains a processor 44 and a wireless network transceiver 42. Processor 44 has two main functions; first to control the orientation of tracker payload 30 with respect to sun 70, and second to send status to and receive operation input from host computer 10. The embodiment shown details the sensors and actuators of a motor 34, an encoder 36, a limit switch 38, and a DC-AC inverter 40. These sensors and actuators are used in a simple single axis tracking device 32. Other embodiments of tracking device 32 and tracking controller 16 will orient tracking payload 30 in two axes with respect to sun 70. In a general sense, there are many other embodiments of tracking device 32 and tracking controller 16 with more or fewer actuators and sensors that can be used to orient tracking payload 30 in an arbitrary number of axes that fall within the scope of this invention.
Referring to FIG. 6, a view of how wireless mesh communications network 18 can be formed from overlapping radio ranges of tracking controller 16 and network manager 14 according to the first embodiment of the present invention apparatus is shown. Network manager 14 has wireless network transceiver 46 and each tracking controller 16 has wireless network transceiver 42. These wireless network transceivers have a transmission range 60. Each transmission range 60 shown in this embodiment is circular and identical, but in other embodiments can be non-circular and not identical. In order to form mesh communications network 18, each tracking controller 16 must reside within transmission range 60 of at least one tracking controller 16 or network manager 14. Also, network manager 14 must fall in transmission range 60 of at least one tracking controller 16. Note that wireless mesh communications network 18 encompasses each tracking controller 16 and network manager 14. This gives wireless mesh communications network 18 a larger physical span than the transmission range 60 of a any single wireless transceiver 42, 46.
Referring to FIG. 7, a view is shown of the physical path a single data packet takes from host computer 10 to tracking controller 16 marked as L according to the first embodiment. The packet first is sent from host computer 10 via communications channel 12 to host gateway 58. Host gateway 58 handles the packet received from communications channel 12, and retransmits it via network manager 14 across wireless mesh network 18. The packet may traverse many hops 74 before finally reaching its destination tracking controller 16. In this particular figure, the communication packet being sent from host computer 10 to tracking controller 16 traverses wireless hops 74 in turn from network manager 14 to tracking controllers 16 B, C, F, J, and L.
Referring to FIG. 8, a representative view of the second embodiment of the wireless mesh communications network of this invention is shown. In this embodiment, one of tracking controller 16 provides network manager 14 and host gateway 58.
Referring to FIG. 9, components of the second embodiment are schematically illustrated. Identical to FIG. 5, communication channel 12 represents the path from host computer 10 to host gateway 58. Network manager 14 and host gateway 58 have identical functions here as in FIG. 5. However, in this second embodiment, base station 56 is not necessary, as tracking device 32′ provides network manager 14 and host gateway 58.
Operation—First Embodiment (FIGS. 1, 2, 3, 4, 5, 6, 7)
The apparatus for wireless mesh networking of solar tracking devices 32 of this invention is used in this embodiment to improve aspects of a site that contains a plurality of solar tracking devices 32. Tracking device 32 in this embodiment of the invention comprises senors, actuators, mechanisms, and controls suitable for orienting tracking payload 30 in two axes with respect to sun 70. In this embodiment, tracking payload 30 comprises flat plate solar panels that point directly at sun 70 when this is possible given the mechanism of tracking device 32. This is a common configuration of solar tracking device 32. However, there are many other configurations of tracking device 32 that can be used in other embodiments of this invention. For instance, single axis tracking devices 32 are common that orient tracking payload 30 (again flat plat solar panels) in one axis with respect to sun 70. This type of tracking device 32 does not point directly at sun 70, but instead orients tracking payload 30 with respect to sun 70 to optimize system power output. In another embodiment, where tracking payload 30 is one or more of some type of reflective devices used to direct electromagnetic radiation 72 incident from sun 70 onto a solar thermal device, tracking payload 30 will not point directly at sun 70, tracking payload 30 will instead be oriented to maximize the amount of reflected electromagnetic radiation 72 from sun 70 falling on the solar thermal device. Additionally, other tracking device 32 configurations, including those with more or fewer than two actuators for controlling the orientation of tracking payload 30, are anticipated.
Tracking controller 16 is a machine controller that in different embodiments could be any apparatus capable of monitoring and controlling a mechanical system such as that comprised by tracking device 32. For example, tracking controller 16 could comprise a programmable logic controller (PLC) or other industrial control computer(s) in different embodiments of the invention. The first embodiment of the invention includes tracking controller 16 with interfaces for the following sensors and actuators:

- Two electric motors 34 used for orienting tracking device 32 in two degrees of freedom with respect to sun 70.
- 8 digital inputs and 4 digital outputs allowing connection of auxiliary sensors and actuators, for instance a latch used when stowing the mechanism in high wind conditions.
- 4 analog inputs and 2 analog outputs allowing connection of auxiliary sensors and actuators, for instance a solar radiation measurement sensor or a potentiometer measuring the position of an actuator.
- 2 serial ports allowing connection of auxiliary sensors and actuators, for instance a DC-AC inverter that measures the amount of solar power being generated.

The first embodiment of the invention allows in a general sense connection to tracking controller 16 of sensors of many different types, both for controlling tracking device 32 as well as sensors for monitoring tracking payload 30. For example, if tracking payload 30 comprises solar panels, then relevant sensors would include sensors for measuring DC and/or AC currents, DC and/or AC voltages, and DC and/or AC power. The sensors could make measurements for one entire tracking payload 30 (for example, to measure the DC power produced by a collection of solar panels). The sensors could also make measurements for some portion of tracking payload 30 (for example, to measure the DC current produced by some subset of the solar panels comprising tracking payload 30).
Each tracking controller 16 includes radio frequency transceiver 42 allowing it to participate in wireless mesh communications network 18. Correspondingly, each tracking controller 16 can be positioned spaced apart from and in radio frequency communication with at least one other tracking controller 16 to define and form wireless mesh communications network 18. Tracking controller 16 can act as a repeater as well as a collection unit creating a communications network with self-healing and self-determining characteristics. Advantageously, this network configuration can create its own infrastructure as additional tracking controllers 16 are added to wireless mesh communications network 18.
The wireless mesh network of this invention advantageously allows tracking controllers 16 to be operated and monitored from a convenient (possibly remote) location while allowing those tracking controllers 16 to be physically located nearby to the tracking devices 32. Tracking controllers 16, for example, may be mounted immediately to some part of the structure of tracking device 32, as shown in FIG. 2. Tracking controller 16 can communicate with host computer 10 via wireless mesh communications network 18 (and hence zero or more wireless network hop 74). The wireless network frequency range used in this first embodiment of the invention is within the Ultra High Frequency (UHF) band, preferably 902-928 mega-hertz and/or 2.4 gigahertz radio frequency (RF). Other embodiments of this invention can use other RF ranges, for example in the Very High Frequency (VHF) band or the Super High Frequency (SHF) band. Wireless mesh communications network 18 in this first embodiment uses modulation technology in order to make the system more robust to radio frequency interference (RFI). In the first embodiment of this invention this technology is direct-sequence spread spectrum (DSSS), but in other embodiments can be similar technologies, for instance Frequency-hopping spread spectrum (FHSS). Tracking controller 16 and network manager 14 can use a medium to high range RF transceiver (capable of communications of up to approximately one mile in open air) to allow formation of wireless mesh communications network 18. Host gateway 58 in turn communicates with host computer 10 via some communication channel 12. Communication channel 12 may be accomplished, for example, with WAN, LAN, Internet, satellite, serial bus, or other appropriate communication technology, or combination of such technologies. It would not be unusual, for instance at a small solar electric power plant, for host gateway 58 to be plugged into a communication bus available on host computer 10 (e.g. USB or PCI). At a large solar electric power plant, it would be possible to connect host gateway 58 to host computer 10 via wireless LAN technology, for instance 802.11g, Zigbee, WiMax, or cell phone standards (e.g. 3G). This allows location of host gateway 58 to be somewhat flexible, the only constraint that network manager 14 (included in base station 56 in this embodiment) must be within radio reception range of at least one tracking controller 16. Host gateway 58 collects information from tracking controller 16 and can transmit that information, preferably in batch format, to host computer 10 either when requested or at some interval. Host gateway 58 can also determine that unsolicited communication is necessary, and can initiate communication with host computer 10 based on some event detected by network manager 14 or tracking controller 16. For example, network manager 14 may detect some systemic network problem that requires immediate attention or tracking controller 16 may detect some problem with tracking device 32 that requires immediate attention. In these examples, host gateway 58 may asynchronously initiate communications with host computer 10, and these communications may generate arbitrary actions on host computer 10, for example database entries or emails/pages to maintenance personnel. Finally, host gateway 58 collects control information from host computer 10 and controls at a top level its transmission over wireless mesh communications network 18 to tracking controller 16.
More specifically, an embodiment of the present invention provides wireless mesh communications network 18 for tracking controllers 16 including at least one but preferably a plurality of tracking controllers 16. A plurality of sensors and actuators are interfaced with each tracking controller 16, and these sensors and actuators are used to orient some tracking payload 30 with respect to sun 70. All status information provided by tracking controller 16 over wireless mesh communications network 18 can be time and date stamped, providing an accurate operating history of tracking controller 16.
This first embodiment of the invention also includes one network manager 14, in radio frequency communication with at least one but preferably a plurality of tracking controllers 16. Network manager 14 has as major functions of (a) managing the formation of and (b) managing the operation of wireless mesh communications network 18. The combination of network manager 14 and tracking controllers 16 further define and form wireless mesh communications network 18. As such, each wireless mesh communications network 18 has network manager 14 and tracking controllers 16 forming an array of communication nodes each which fall within transmission range 60 of at least one other node. This network configuration helps reduce line-of-site communication problems and overall hop 74 distance problems associated with other wireless networking technologies, thereby improving the effective range of the radio frequency transceivers. This first embodiment of the invention comprises a separate base station 56 that provides both network manager 14 and host gateway 58. However, in alternate embodiments both tracking controller 16 and host computer 10 can be network manager 14. In such alternative embodiments (including the one shown in FIG. 8), that function could be integrated into, for instance, a single circuit board that can perform the functions of both network manager 14 and tracking controller 16. Another embodiment of the present invention would have one tracking controller 16 provide network manager 14, and another tracking controller 16 provide host gateway 58.
In the first embodiment, base station 56 provides network manager 14 and host gateway 58. Base station 56 comprises two communication transceivers; one is wireless network transceiver 46 and the other is transceiver 48 suitable for connection to communication channel 12. Host gateway 58 must provide a buffering capability for messages to and from host computer 10 and tracker controllers 16. This buffering capability might be used, for instance, when a relatively slow and high latency WAN is used for communication channel 12. In this case, status information from tracker controller 16 will sometimes need to be buffered on host gateway 58 until communication channel 12 is able to transmit this information to host computer 10. Host gateway 58 software will also route at an application level messages to be transmitted from host computer 10 to tracking controller 16. Buffering of messages in host gateway 58 will also be required, for instance in the case where wideband RF noise intermittently disrupts wireless mesh communications network 18 but does not disrupt communication channel 12.
Tracking controller 16 can monitor the performance of tracking device 32 and tracking payload 30 through any input means, including digital inputs, analog inputs, or inputs otherwise encoded (e.g. a DC-AC inverter connected via a communications port). Many different measurements of the performance of tracking device 32 can be made. For instance, the efficiency of an actuator could be determined using measurements of (a) the amount of energy used to drive the actuator and (b) the resulting motion of the actuator. Similarly, measurements of the performance of tracking payload 30 can be made, such as measuring both the illumination condition and the amount of electricity generated by an array of solar panel, and using the result to determine the efficiency of the entire solar energy collection system.
Host computer 10 used for system control and monitoring is in the first embodiment located indoors and remote from base station 56. Host computer 10 receives status information from tracking controller 16 (via wireless mesh communications network 18 and host gateway 58). In addition, host computer 10 provides operation data (for instance time and date) to tracking controller 16. This allows redundant sensors to be removed from individual tracking controllers 16. Host computer 10 can analyze the status information received from tracking controller 16 to provide services, for example detecting a failure in tracking device 32 based on some measurement available from tracking device 32 or tracking payload 30 (for instance, of the power output by an array of solar panels). Other services that can be provided by analysis of this status information would include predictive and preventative maintenance, for instance predicting the future failure of a bearing in tracking device 32 based on changes in the amount of actuator force required for performing a particular function. Advantageously, host computer 10 can provide the operator a wide range of both tracking controller 16 specific information and system wide information, allowing system efficiency to be increased and mean time to repair to be decreased. Advantageously, host computer 10 can also provide the operator a means to perform both tracking controller 16 specific and system wide functional control, for instance command one single tracking controller 16 to perform self diagnostics or command all tracking controllers 16 in a system to return to a stow position in the case of high winds.
Executing on host computer 10 is operator interface program 50. This program facilitates operation of all tracking controllers 16 on a site. Operator interface program 50 interacts with database 52 and allows any combination of real-time or historical system information to be shown to the operator. In addition, the operator can command a one or more of tracking controller 16 from this interface. In the embodiments shown, host computer 10 is a single computer comprising operator interface program 50 as well as database 52. Alternative embodiments can have the functions of host computer 10, operator interface program 50, and database 52 each split across one or several computers, connected via any suitable communication technology (e.g. WAN, LAN, local bus).
Operation—Second Embodiment (FIGS. 8, 9)
In this second embodiment of the invention, network manager 14 and host gateway 58 are provided by one of tracking device 32. This allows a system with identical function to the first embodiment to be constructed, but with lower cost because a separate base station 56 is not required.

Other Embodiments

Other embodiments of the invention are possible depending on the particular constraints of an installation. Because the functions of network manager 14 and host gateway 58 are distinct, other embodiments include:

- Separating network manager 14 and host gateway 58 between two tracking devices 32 could provide a better functioning system by allowing host gateway 58 to be provided by tracking device 32 that is closest to host computer 10 and allowing network manager 14 to be provided by tracking device 32 that is most centrally located (giving wireless mesh communications network 18 better operating properties).
- In some situations, it may be advantageous for host computer 10 to comprise network manager 14 and host gateway 58. This configuration would require no infrastructure for communication channel 12. However, this configuration is limited because host computer 10 (which now comprises network manager 14) must be in radio communication with at least one of tracking controller 16.
- Combining on a single printed circuit board host gateway 58 and one tracking controller 32. This would allow cost reduction by allowing these elements to share a single RF transceiver.
- Combining on a single printed circuit board network manager 14, host gateway 58, and one tracking controller 32. This would allow cost reduction by allowing these elements to share a single RF transceiver.

Advantages
The invention described herein, for an apparatus for networking solar tracking devices, has many advantages over prior art. These advantages include:

- The capability to provide a reliable and cost effective remote control and monitoring of tracking controllers 16, particularly valuable on installations comprising a large number of tracking controllers 16.
- Sensors applicable to an installation comprising more than one solar tracking controller 16 do not need to be duplicated at each tracking controller 16; they may be installed in a single place and their readings propagated over wireless mesh communications network 18 of this invention.
- Enabling combinations of information to be used for operating tracking controllers 16 that are not anticipated by prior art.
- Enabling reliable remote upgrade of operating software in solar tracking controllers 16.
- Enabling remote monitoring of the performance of tracking devices 32.
- Enabling remote monitoring of the performance of tracking payloads 30 on the same apparatus as the monitoring of tracking devices 32.
- Eliminating the need for costly and cumbersome wired network infrastructure such as would be needed if the above mentioned benefits were provided by, for example, an Ethernet network.

Claims

1. An apparatus for wireless mesh networking of solar tracking devices, the apparatus comprising:

a plurality of solar tracking devices, each comprising a tracking controller;

each of said tracking controllers comprising a radio frequency transceiver module and having a radio communications link with at least one other of said tracking controllers;

a network manager comprising a radio frequency transceiver module, having a radio communications link with at least one of said tracking controllers, said network manager serving to organize and maintain a wireless mesh communication network comprising said network manager and said tracking controllers;

a host computer responsible for operating said tracking controllers;

a communication channel connecting said host computer to one device of said wireless mesh communication network;

wherein operation data sent by said host computer to said tracking controller travels across said wireless mesh communication network.

2. The apparatus of claim 1, wherein said operation data comprises the absolute latitude and longitude of said tracking controller.

3. The apparatus of claim 1, wherein said operation data comprises the absolute latitude and longitude of the site in combination with the relative latitude and longitude of said tracking controller.

4. The apparatus of claim 1, wherein said operation data comprises the date and time.

5. The apparatus of claim 1, wherein said operation data comprises environmental conditions relevant to said solar tracking devices.

6. The apparatus of claim 1, wherein said operation data comprise an executable program for said tracking controllers.

7. An apparatus for wireless mesh networking of solar tracking devices, the apparatus comprising:

a plurality of solar tracking devices, each comprising a tracking controller;

a host computer responsible for monitoring said tracking controllers;

wherein monitoring data sent by said tracking controllers to said host computer travels across said wireless mesh communication network.

8. The apparatus of claim 7, wherein said monitoring data comprises measurements of the performance of said tracking devices.

9. The apparatus of claim 7, wherein said monitoring data comprises measurements of the performance of said tracking payloads.

10. The apparatus of claim 7, wherein said monitoring data comprises status information for any combination of actuators, sensors, and algorithms comprising said tracking devices.