Single axis solar tracking system

[0001] The presently claimed invention relates to the production of solar energy and, more particularly, to a method and apparatus for constructing mechanically linked, single-axis solar tracking systems, for various tracking geometries for daytime motion tracking. of the sun.

Background of the technique:

[0002] The solar tracking systems used in the production of renewable energy are devices that follow the movement of the sun with respect to the earth to maximize the production of solar energy. The solar trackers move to keep the solar modules perpendicular to the sun in one or two axes. The present claimed invention applies to photovoltaic (PV) modules for generating electrical energy, but it can be applied to any solar energy collection device, such as exposure testing devices for thermal or solar materials. Solar trackers have been successfully implemented in the industry; however, prior art designs have not adequately addressed initial installation costs, flexibility to adapt to site conditions and reliability over the relatively long service life (more than 20 years) of the system. When choosing a solar tracking system, all of the following variables should be considered:

• cost of the photovoltaic module, • land cost, site geometry and availability.

• installation labor cost, • material cost, • weather data, • operation and maintenance costs, • general increase in efficiency provided by the tracker.

[0003] The state of the art approaches have not fully optimized the combination of all relevant cost issues. The energy gain provided by the trackers depends on the tracking geometry of the system and the location of the installation. A dual-axis tracker (D / A) keeps the collector perpendicular to the sun on both axes, and provides the greatest gain in energy production at any location. The single-axis followers (S / A) are fixed on one axis and usually follow the daily movement of the sun on the other axis. The geometries of the single-axis tracker include inclined, azimuth and horizontal elevation. S / A inclined elevation trackers are tilted based on the latitude of the location and track the sun's daily movement on that inclined axis. The S / A azimuth trackers are tilted at an optimal angle and follow the daily movement of the sun rotating around the vertical axis. Horizontal S / A trackers are configured parallel to the ground and revolve around a horizontal North / South axis to track the sun's daily movement. The energy obtained varies for each type of tracking geometry and depends on the latitude of the installation and the climatic conditions at the installation site. Solar tracking systems for photovoltaic modules are commercially available in single axis tilting and balancing, horizontal single axis, fixed single axis azimuth and dual axis geometries.

[0004] All trackers must be constructed strong enough to withstand wind forces in any tracking position or be stored to reduce the effect of extreme wind forces. The modules also require periodic cleaning, which in many places is mainly achieved by washing the modules with rain. Snow can affect the operations of the tracker, due to the presence of ice or the weight of the snow in the modules, or the accumulations of snow that interfere with the movement of the tracker and the collection of solar energy. In addition, building materials, electronics, engine components and engines must be able to operate within the limits of temperature and climate.

[0005] In many applications, the single horizontal axis tracker is the most cost effective tracking geometry. An S / A horizontal tracker structure can be supported at many points along the rotating axis and, therefore, requires less complexity and less construction material than other tracking geometries. The key to the successful design of a monitoring device for photovoltaic modules is to provide the maximum overall economic benefit, such as the initial cost of the device, the cost of installation, the use of the land, the cost and efficiency of the solar modules, and operation and maintenance costs, as well as the efficiency gain provided by the tracking geometry. As the cost of steel and other manufacturing materials increases, horizontal tracking geometry is increasingly desirable. Minimizes structural material requirements by keeping the modules in a relatively low profile for the foundation, and with a minimum load of

EN 2 735 546 T3 moment suspended in relation to the rotating shaft without requiring special connections to rotate the system around its center of gravity.

[0006] The prior art horizontal axis trackers have typically connected each row of modules together with a linear motion link in an effort to minimize the number of drive motors needed. The unique horizontal and mechanically linked inclined single axis tracking systems of the prior art require substantial mechanical bonds structurally capable of withstanding high force loads due to the weight of the protruding solar module and large wind-induced forces.

[0007] The drawback of this prior art system is that all wind forces are concentrated at a single point, through mechanical articulation. The embodiment of the claimed invention specifically eliminates the need for a robust mechanical joint capable of withstanding high load forces induced by wind. The design of the current embodiments eliminates the transmittance of these wind forces to the link, and counteracts the external wind forces locally, within each row or set of trackers, so that the wind force is not transmitted to the link. The prior art also requires a large separate base, or foundation, to anchor a single drive mechanism that rotates many rows of modules with a linear motion motor. One such device is a single horizontal axis tracking system described in US Pat. UU. No. 6,058,930 to Shingleton. In this system, the horizontal rows of modules are linked to each other with a linear motion link and are operated by a single linear actuator attached to a large separate base. In addition to the horizontal axis of the prior art, mechanically linked trackers require generally flat or graduated ground for proper operation. Many columns must be installed at heights of height and locations that require high tolerance within more than 100 columns, in two dimensions in a large area, so that the mechanical links between rows are aligned for operation. This often requires extensive and expensive site preparation. Some horizontal trackers linked to the prior art have embodiments that allow installation in undulating terrain, but require expensive joints that must be manufactured in situ and that must also withstand the great forces induced by the wind. These pivot joints loaded with great force are generally complicated and expensive to build. Another disadvantage of the prior art is that they are designed as large rectangles with a link that extends through the center of the matrix field. If the installation field is not suitable for the shape of a rectangle, these systems are often used in less than optimal configurations in which the link controls fewer modules. This is another factor of cost increase for the prior art in many installations. The prior art linear motion link represents an excess of material and an installation cost component that requires a lot of labor. The link must be robust to directly resist the strength of a full field of many rows of followers to a large linear drive that must be placed on a large base separated from the linear drive. The large and separate base is necessary to anchor the transmission mechanism and must withstand very high wind-induced forces throughout the tracker field. In addition, flexibility in site design is affected by the linear motion link, since the drive connection must generally be executed, centered on the rows, and installed on a perpendicular straight line. The prior art mechanical link must be fixed at right angles to the torsion tube and cannot deviate from the perpendicular, therefore, it does not allow the system to adjust to the irregular limits of the installation site.

[0008] Another linked tracking system for driving a plurality of individual solar tracker mounting with an engine described in US 2008/0308091.

[0009] Tracking geometries other than the single horizontal axis require more ground area for installation. In a tracker field, all tracker geometries, except the horizontal axis tracker, must be spaced in two dimensions, East / West and North / South, so as not to shade each other. The horizontal axis tracker only needs to be spaced in the East / West dimension to relieve shading and therefore requires much less ground for its implementation. The contour and shape of the terrain also critically control the cost of installing most of the horizontal single axis tracking systems.

[0010] Another type of horizontal axis tracker is not linked and typically includes multiple PV modules mounted on a torsion tube. These are designed as rows driven independently by motor. These horizontal trackers are individually driven by a motor / gear transmission system and the photovoltaic array revolves around the center of gravity of the photovoltaic module tracking system. The rotation of the matrix around the center of gravity eliminates the momentum loads applied to the transmission due to the outstanding weight of the solar modules. To rotate the die around the center of gravity, this type of horizontal tracker design requires more structural material and more expensive torsion tube connections and bearings than current horizontal shaft tracker embodiments. Other disadvantages of these tracker designs include a higher projected wind area that requires more structural material and large foundations to withstand larger moment loads and higher capacity units to overcome the moment load from the solar modules that are mounted to a greater distance of the torsion tube due to the higher profile of the die. They also have more complex support and support points that rotate the photovoltaic modules over the center of gravity of the tracker, and use one motor per individual tracker row, which is equivalent to an increase in cost, maintenance and reduced reliability.

EN 2 735 546 T3 [0011] A third tracker geometry is a single inclined track tracker. Often called a tilt and roll follower, it tilts in elevation and then spins around that inclined axis. This type of tracker generally offers a higher gain compared to a horizontal tracking system, but at an additional cost that must be critically analyzed before deployment. These costs include the requirement of more land due to the space needed for shading in the N / S and E / W dimensions and a more complex structure that requires more structural material due to the increase in projected height from the foundation. Nor are these systems capable of being stored automatically during high winds, since the elevation angle is fixed and, therefore, must be structurally capable of withstanding all wind forces. Another inclined single axis geometry is a fixed inclination azimuth tracker. A fixed inclination azimuth follower tilts in elevation and then rotates around a vertical axis. This design, although usually more structurally stable than a tilt and roll tracker, has the same cost drawbacks as the tilt and roll design; although, the performance gain can make the inclined single axis geometry economical for some installations.

[0012] The last tracking geometry is a dual axis tracker (D / A). D / A trackers provide the highest performance gain over all the tracking geometries mentioned, since they keep the solar modules perpendicular to the sun on both axes. Exist; however, several practical disadvantages of these systems: more land is required due to the space needed to shade in two dimensions; a more complex structure that requires more structural material is necessary as a result of the increase in the projected height from the ground and the foundations; and a second drive shaft is necessary for lifting, which increases complexity, expenses and maintenance problems. In addition, D / A systems typically use two drive motors for a relatively small surface area of ​​solar modules that increases both the initial cost and subsequent maintenance costs. Some types of solar collectors, reader concentrators, for example, require D / A tracking to function.

[0013] As indicated above, an ideal solar tracking system should operate in all types of conditions. This includes situations in which the movement of a tracker is impeded by obstructions or the like. If there are no security guards in place, the tracking system can cause permanent damage when there is an obstruction condition. In addition, human intervention may be necessary to cure the condition. Sometimes, timely human intervention is impossible if the trackers are in remote locations and, secondly, sending a technician for each obstruction condition can be very expensive.

[0014] Another need in a solar tracking system is the ability to have flexibility in the design of support systems at different lengths of transmission shafts for different terrain conditions and systems. Currently, the manufacture of specific lengths of transmission shafts requires field welding and painting. A similar problem exists for torsion tubes. A design is necessary to provide a simple method for joining torsion tube segments in the field.

SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION) [0015] The system of the present invention has an adjustable limit for the transmission torque applied by the engine to the transmission. The system controls the torque by sliding the clutch or engine power, the sensors that monitor the movement of the tracker or other monitoring methods, to determine an event that obstructs the movement of the tracker. A remote location controls the status of each tracking system and sends commands through a communication system. Once the monitors or sensors detect an obstruction event, the system enters an obstruction removal mode 1 (OCM1), which is a series of adjustable high-frequency attempts to move the obstructed tracker for an adjustable predetermined period of time. . If the tracker starts normal movement as one of the series of attempts, the system continues normally. If the obstruction condition persists after the predetermined period of time, the system enters an obstruction removal mode 2 (OCM2). This mode is an adjustable lower frequency mode for a longer and more adjustable predetermined period of time. Again, if during this mode the tracker moves normally, the system returns to normal operation. If the clogging condition persists after OCM2, remote location is recommended and maintenance personnel can be sent to the location. The remote location, throughout this process, receives information and can send commands to the tracking system. The obstruction monitoring and cleaning system may be designed to prevent damage from excessive torsion in the transmission line or other components and prevents breakers from tripping, which implies a visit by maintenance personnel to reset the circuit breaker.

[0016] Other objects, advantages and new features, and the additional scope of applicability of the presently claimed invention will be set forth in part in the detailed description below, taken together with the accompanying drawings, and in part will be apparent to those skilled in the art. matter by examining the following, or they can be learned through the practice of the claimed invention. The objects and advantages of the claimed invention can be realized and achieved by means of the instruments and combinations particularly indicated in the appended claims.

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BRIEF DESCRIPTION OF THE DRAWINGS [0017] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate several embodiments of the presently claimed invention and, together with the description, serve to explain the principles of the claimed invention. The drawings have the sole purpose of illustrating preferred embodiments of the claimed invention and should not be construed as limiting the claimed invention. The drawings are included in the description below.

Fig. 1A shows a mechanically linked horizontal tracking embodiment. Fig. 2 is a flow chart showing the realization of the adjustable limit for excess torque conditions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (BEST MODES OF EMBODIMENT OF THE INVENTION) [0018] Fig. 2 is a flow chart showing the method of incorporating an adjustable limit to the transmission torque that can be applied by the engine to a power line. transmission. In most tracker systems, when a tracker is prevented by an obstacle or a large amount of snow, the engine breaker trips, which causes a person to get out of the stuck tracker to reset the switch, even if the obstacle is removed or the jam condition disappears. For example, if a large amount of snow has fallen and temporarily prevents the movement of the tracker. The present claimed invention provides a system for temporarily withdrawing power to the engine for a predetermined time and then providing power to the engine once the prevented condition is eliminated or continuing to avoid power to the engine if the condition continues. after at least one restart cycle. The determination of the amount of torque of the transmission line or the lack of movement of the tracker can be performed in several ways. The clutch slippage can be determined, a sensor can be mounted on the tracker to detect movement, the amount of power used by the engine can be monitored for a predetermined level or any other similar method can be used, each of these methods , collectively defined, as a detection movement of the follower assembly.

[0019] With reference to Figs. 1 and 2, the system and method first calculate a position 150 in a programmable logic control (PLC) 152, as is done in most tracking systems. The system sends a message to move tracker 154, if necessary. If the tracker is in a correct position and it is not necessary to move it 156, the system recalculates the position mode 150. This information is transmitted to a remote monitoring and data acquisition (SCADA) 180, through an integrated controller 17. SCADA 180 provides communication to and from one or more tracking systems through typical communication networks 19. Yes the tracker requires movement 158, a message is sent to the tracker motor 14 to move the tracker. The position feedback of the tracker 160 is provided from the tracker motor 14 and a determination of whether the tracker is moving 162, through a motion sensor 21. If the tracker is moving 164, the system is operating normally and the system feeds back to calculate position mode 150. If the tracker is not moving 166, the system enters obstruction removal mode 1 (OCM1) 168 and PLC 152 sends a signal to SCADA 180. OCM1 168 is typically a high frequency attempt to move the tracker for an amount of predetermined time when activating 170 the tracker motor 14 and sending a signal to calculate position 150. For example, this may be once per minute for a period of thirty minutes. The frequency and time period are fully adjustable by a user. OCM1 168 is usually sufficient to compensate for a momentary wind event or temporary obstruction. If the tracker moves according to the instructions during the OCM1 period, the tracker is operating normally again and reported 172 to SCADA 180 and to calculate position 150.

[0020] After the predetermined amount of time in OCM1 168 mode is exhausted and there is still a non-movement condition, an indicator 174 is provided and the system enters a clearing obstruction mode 2 (OCM2) 176 through a SCADA 180 message. OCM2 176 is usually a less frequent attempt to move the tracker, for example, once every twenty minutes, for a longer period of time, for example, two weeks. Again, the frequency and the period of time are fully adjustable by the user. The OCM2 176 is designed for longer-term obstruction events, such as a snowstorm on the roof. If during the time period of OCM2 176, the tracker starts to move, this is reported 178 to SCADA 180 and to calculate position 150 and the system operates normally. If after the time period of OCM2 and no movement of the tracker is measured, the system ceases all attempts at movement and informs SCADA 180 that there is a malfunction condition and maintenance personnel can be sent to the site.

[0021] Although this description relates to PV modules, the presently claimed invention can also be used to track solar heat collectors, the construction of shadow systems, the light exposure test of materials, and other systems that They require sun tracking.

[0022] Although the claimed invention has been described in detail with particular reference to these previous embodiments, other embodiments may achieve the same results. Variations and modifications of this

The claimed invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all modifications and equivalents of this type.

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