ITPD20070082A1 - METHOD AND DEVICE FOR THE ORIENTATION COMMAND OF SURFACES SURFACES OF PHOTO-VOLTAIC PANELS INTENDED FOR PLANTS FOR THE PRODUCTION OF ELECTRICITY - Google Patents

Description

DESCRIPTION

The present invention relates to a method for the operative control of orientation of the absorbing surfaces of photovoltaic panels, having the characteristics set out in the preamble of the main claim n. 1. The invention also relates to a control device operating according to the aforementioned method.

In the technical field of reference, relating to plants for the production of electrical energy by converting light radiation by photovoltaic effect, radiation-capturing elements (photovoltaic cells or photosensitive cells) made in the form of panels are notoriously used. they are mounted on support structures and are capable of being controlled in an orientation movement around one or more axes.

The movement of the panel allows to orient the capturing surface with respect to the direction of the incident light radiation, as the relative positioning between earth and sun varies during the daily hours of sunshine, in order to maximize energy production. In this regard, it is typical to provide control methods that allow the panel to be moved trying to obtain a relative positioning with the absorbing surface perpendicular to the rays of the light radiation, in order to have the maximum direct light intensity on the surface.

A first known methodology provides that the photovoltaic panel is moved, in its orientation movement, in a sequence of pre-calculated positions, and determined taking into account the geographical position of the panel (latitude and longitude), which determines a certain relative positioning with respect to the sun which varies during the solar year. In other words, by means of appropriate algorithms, the respective positioning of the panel with respect to the luminous radiation is identified for each unit of time, for example for each hour of the day of each day of the calendar year, which ensures the best angle of incidence. In this case, tracking commands are provided which allow the panel to be oriented according to the sequence of pre-calculated positions.

This method has a main limitation in the fact that, due to the variability of climatic conditions, for example linked to the different degree of cloudiness of the sky, the position of the best theoretical impact, does not often correspond to the position of maximum energy production, precisely because the conditions meteorological disturbances and can alter ideal theoretical conditions, with phenomena of reflection or refraction of luminous radiation that can determine positions of maximum efficiency different from the theoretical pre-calculated ones.

In this sense, technical solutions have been proposed that involve the use of light radiation sensors mounted on the photovoltaic panels. These sensors, by means of the rotational movements allowed to the panel, are moved along certain sequences of rotations at a preselected angular pitch, acquiring, in each angular positioning, a signal correlated to the light radiation incident on the sensor. By comparing the purchase signals, the positioning corresponding to the highest efficiency is subsequently selected and consequently the panel is oriented in this position. At certain time intervals, the known method provides for the aforementioned scans to be repeated, in a certain predetermined angular space (to explore a significant part of the celestial vault), so as to vary over time the positioning of the panel during the day.

For each orientation point of the panel the aforementioned scan is therefore preliminarily performed to allow the sensor to acquire the signals and, by comparing them, to choose the optimal positioning. This method, if on the one hand it has the advantage of allowing the choice of the orientation of the panel according to the real irradiation conditions, through the scanning carried out by the sensor, on the other hand it has the limit of having to request the movement of the entire surface. capturing the panel, in the phase of acquisition of the signals by the sensor, a penalizing aspect both for the time required, for the energy required in the movement of the entire panel, and for the stresses induced in the structure of the panel during the repeated movements of the panel. itself, which can compromise its efficiency and duration.

Furthermore, in order to increase the efficiency of the system, it is necessary to reduce as much as possible the angular step of scanning in the movement of the sensor, requiring, on the other hand, an increase in the number of movements of the panel, with an increase in the problems linked to the aforementioned limits. .

On the other hand, technical solutions are known in which the methodology of the pre-calculated positioning is integrated with the methodology of the detection sensors on board the panels, solutions which however show the limits mentioned above and do not obviate the aforementioned drawbacks.

It should also be noted that the sensor means provided on the photovoltaic panels can in turn have functional limits and therefore make the identification of the point of maximum energy production uncertain. In fact, this identification is generally based on the comparison of signals acquired by the sensor during orientation movements, for example conducted around a pair of axes (an azimuth axis and an oscillation axis around an axis perpendicular to the azimuth axis), the choice being carried out on the basis of the equality of the signals detected in the two rotations, or on a predetermined threshold value within which the difference of the signals acquired in the same positioning point must be placed, the criterion therefore, introducing a certain level of approximation and compromise in the choice of the point of maximum efficiency, it consequently determines a certain degree of uncertainty in such identification.

A main object of the present invention is to provide a method and a device for controlling the orientation of the absorbing surface of photovoltaic panels, structurally and functionally designed to overcome the limits highlighted with reference to the cited prior art.

This and other objects which will appear clearly in the following are achieved by a method and a device made in accordance with the following claims.

Further characteristics and advantages of the invention will become clearer from the detailed description which follows of a preferred example of embodiment illustrated, by way of non-limiting example, with reference to the accompanying drawings in which:

- Figures 1 to 3 are respectively perspective, front elevation and top plan views of a device operating with the method of the invention,

- Figure 2 is a partial perspective view of a photovoltaic panel designed to be oriented with a control device operating with the method of the invention,

figure 5 is a front elevation view of the panel of figure 4,

- figure 6 is a perspective view, on an enlarged scale, of a detail of the panel of figures 4 and 5,

- figure 7 is a view corresponding to that of figure 1 in a variant embodiment of the device of the invention,

Figure 8 is a schematic view of the panel orientation control system with the method of the invention,

Figure 9 is a view corresponding to that of Figure 8 in a further embodiment variant.

With reference to the aforementioned figures, 1 generally indicates a support structure (only partially represented) of a plurality of photovoltaic panels, all indicated with 2, housed in a pair of frames 3a, 3b rotatably supported on the structure, around an axis of rotation X. The support structure is shaped like a gantry with a pair of legs 1 a (only one of which is shown) between which a shaft 5 is rotatably supported, at its axial ends.

The frames 3a, 3b are solidarized to the shaft 5 from laterally opposite sides, in a configuration such that the surfaces for capturing the light radiation of the panels 2 are coplanar with each other. Furthermore, by rotation around the X axis, the overall surface of the collector of the panels 2, indicated with 2a, can be oriented with respect to the support structure 1, this orientation being required to position the absorbing surface 2a at the most appropriate angle with respect to the direction of incidence of light rays, this direction varying during the day due to the effect of the relative movement between the sun and the earth, in order to obtain the maximum energy production in the photovoltaic panels 2.

For the rotation control of the shaft 5, around the X axis, in the orientation movement of the capturing surface 2a, a kinematic transmission is provided comprising a motor 6, operatively connected to the shaft 5, a reduction gear 7, with orthogonal shafts, whose output shaft is coaxially connected to shaft 5.

To move the absorbing surface 2a in the orientation around the X axis, a control device is provided, globally indicated with 10, operating according to the method of the invention, which will be described in detail below. The device 10 comprises a stationary support 11, on which a sensor 12 of irradiation of the light radiation is rotatably supported, around an axis, indicated with X '. More specifically, the sensor 12, which is conventional per se, comprises a flat surface 12a capable of being hit by the light radiation and transducer means for transforming the amount of energy detected by the sensor into a voltage signal (mmVolt) output to terminals 13 of the sensor. Said sensor is conveniently an analog irradiation sensor, adapted to measure the quantity of energy produced by the radiation which affects the absorbing surface 12a. The sensor 12 is also operatively associated with an angular position sensor 14 capable of detecting the angle of rotation traveled following a rotation around the X axis from the surface 12a. Preferably the sensor 14 is of the analog type, for example potentiometric. 15 also indicates an electric motor, with reversible rotation, preferably in direct current, designed to control the radiation sensor 12 in rotation, with consequent orientation of the surface 12a around the X axis'.

16 indicates a circuit complex, for example made in the form of an electronic card, designed for the functions that will be clarified in detail in the description of the method given below, which is designed to control the orientation of the photovoltaic panels.

The circuit assembly is provided with circuit means 17 for acquiring signals from the device 10, with means 18 for storing signals, with means 19 for comparing signals and with means 20 for generating control signals for the motors 6 and 15. Means for the transmission of signals, in the form of electrical conductors 21, are provided between the device 10 and the electronic board 16 and between this and the motor control means of the panels 2.

The method of the invention provides a first preliminary step of so-called calibration in which the surface 12a of the sensor 12 is oriented in such a way as to be coplanar with the overall capturing surface 2a of the photovoltaic panels. In this regard, conventional equipment such as spirit levels or similar devices can be used. To properly orient the sensor 12, this can be oscillated around the X 'axis and, in addition around a Y axis, orthogonal to X', at which the sensor is mounted in an articulated manner on the support 1 1. Screw locking means are provided on this axis Y to constrain the sensor 12 relative to the support 11, once the position of coplanarity with the surface 2a has been identified.

The calibration phase is followed by a detection phase, in which the surface 12a of the sensor is oscillated, around the X 'axis, in a sequence of consecutive angular positions, angularly spaced, and in each of these positions the corresponding incident irradiation is detected. the surface 12a. The quantity of energy produced by the photovoltaic effect is proportionally correlated to the voltage signal V output at the terminals 13 of the sensor, which is sent and acquired in the electronic board 16, through the means 17. With reference to Figure 2, a preferred choice provides that the capturing surface 12a is oscillated at a constant angular pitch, for example equal to 1 °, from an angular position of -60 ° with respect to a theoretical horizontal axis, indicated with P, to an angular position of 60 ° with respect to to this and plan, as shown in the figure. In each of the angular positions included in the aforementioned angular portion, and significant for an adequate scan of the celestial vault, a signal V corresponding to the production of energy correlated to the radiation incident on the surface is therefore detected, this value depending on both the direction of incidence of the radiation and from the disturbing effects on the intensity of the radiation (weather conditions) present at the time of detection.

For the rotation command of the surface 12a, it is provided that the motor 15 is driven by a signal controlled by the angular position sensor 14, with which the motor is stopped every time the chosen angular step is covered, in the rotation around X '.

The method also provides for a comparison phase which alternates with the detection phase at each pair of consecutive detections carried out by the sensor 12. In other words, it is envisaged that for each pair of consecutive angular positioning, the acquired signals are compared with each other and the the value of the two relating to the signal with the greatest energy production is stored together with its corresponding angular position. For each subsequent detection, this comparison is made, in such a way that the storage means 18 retain in memory the largest (Vmax) of the signals V acquired in the scan. Once the scan has been completed, the angular position of the sensor 12 corresponding to the point of maximum energy production is then kept in memory. By means of this information, in a subsequent step, identified as the panel orientation control step, the motor 6 is rotated until the surface 2a is oriented with the same orientation angle of the sensor corresponding to the maximum production. energy. In other words, the surface 2a is rotated around the X axis until it reaches a coplanar configuration with the surface 12a corresponding to the point of maximum energy production. The control of the rotation around the X axis is entrusted to an angular position sensor 6a, associated with the motor 6, completely similar to the position sensor 14, by means of which the motor 6 is stopped when, with a feedback signal sent to the electronic board from the sensor 6a, the selected angular positioning is reached.

The method provides that the set of phases of detection, comparison and command in the orientation of the panels, is repeated in predetermined time intervals, during the day, for example, according to a preferred choice, with intervals of 15-20 minutes. In this way, at the end of each interval, once the detection and comparison step has been performed, the angular positioning relative to the point of maximum energy production is identified and the capturing surface 2a of the panels 2 is rotated accordingly. It follows that this surface is conveniently rotated exclusively to reach the positioning identified in each time interval, while the rotations required to scan the celestial vault, in the detection phase, are carried out by the irradiation sensor 12, which is moved independently of the photovoltaic panels. Furthermore, the control device 10, with the sensor 12, can be located in a remote position from the structure 1 of the panels 2, it being only necessary to ensure the coplanarity of the absorbing surfaces 2a of the panels and 12a of the sensor, prior to the orientation step.

In a variant embodiment of the device 10, illustrated in Figure 7, the rotation of the sensor 12 around the Y axis is also controlled by means of an angular position sensor 22, aimed at controlling the rotation command of a motor 23 adapted to to rotate the sensor around the Y axis. The angular position sensor 22 is conveniently selected of the analog type, for example potentiometric and can be completely similar to the angular position sensors 6a and 14.

In a further variant of the invention, the device 10 may be provided with a third motorized rotation axis Z, directed orthogonally to the X 'and Y axes described above, so as to form a triad of orthonormal axes. This third degree of freedom which the device can be equipped with can be controlled by a sensor measuring the corresponding angular position (similar to those described above) in order to know its orientation with respect to the aforementioned third vertical axis (azimuth ). This motorized axis allows the device described above to become a three-dimensional scanning device (scanner) of the radiation coming from the celestial vault and therefore can be used for mapping the radiation, finding the maximum of this wherever it is and allowing it to move in a completely autonomous way. any biaxial tracker systems (rotation around two orthogonal axes, the first azimuth and the second around a horizontal axis). The advantages described above for the uniaxial follower have a direct impact and equally on the biaxial followers which can be moved in a much more rational way by reducing the stresses and being able to use an inverter, as described later in more detail, for the control of their engines reducing costs.

In the diagram of figure 8 it can be seen how with a single device 10 it is possible to control the orientation of absorbing surfaces 2a belonging to a plurality of support structures 1 of panels 2.

The diagram of figure 9 illustrates a preferred configuration of the device 10 according to the invention, conceived to control the orientation of a plurality of absorbing surfaces 2a, obtained by arranging in a modular way groups of panels 2 associated with respective support structures 1 a located adjacent to each other.

For clarity, the motors 6 associated with each structure 1 a are indicated as 6 ', 6 ", 6"', .. and so on. The reference number 25 indicates an inverter device integrated in the electronic board 16 and arranged to supply the power command signal to the aforesaid motors. It is foreseen that on the power connection line of each motor 6 ', 6 ", 6"', ... with the board 16 there is a respective switch 26 ', 26 ", 26", .., of the line, which can be operated in opening / closing by a signal sent by the board. In this way, it is possible to drive the motors in sequence, closing the switches 26 ', 26 ", 26", .. one by one, for an orientation of the structures implemented in a selected time sequence. This drive is conveniently acceptable and advantageously allows the inverter 25 to be dimensioned on the power of the single motor 6, although the inverter can operate all the motors present. It is also possible to provide orientation sequences of different structures (always with drives of a single motor at a time) for specific needs related to the area covered by the panels.

The invention thus achieves the proposed purposes, achieving numerous advantages over known solutions.

A first advantage is linked to the fact that thanks to the device and method of the invention, it is first of all the certainty that the identified positioning is that of maximum energy production, due to the fact that the scanning of the celestial vault is done in real time with the actual irradiation conditions as well as with real weather conditions. Furthermore, with the method of the invention it is avoided having to move the entire capturing surface of the panels during the scanning phase, to search for the most effective positioning, this movement being performed by the remote irradiation sensor. This allows energy savings in handling, due to the reduced mass and inertia of the sensor compared to the structure of the photovoltaic panels, allows greater speed, leads to longer duration of the structure of the panels, due to the lower dynamic stresses, linked to the lower number of movements required, for greater overall plant efficiency.

Also note the advantage that with a single control device it is possible to control the orientation of a plurality of structurally independent photovoltaic panel structures. With these configurations it is also advantageously obtained that the panels of the plurality of structures are controlled in orientation by means of a device with a single irradiation sensor, according to desired and selected sequences, as well as programmable.

In addition, through the use of an inverter, as highlighted above, with which the power supply voltage of a motor is controlled in frequency, it is possible to have a very gradual starting and starting with a reduction in stress. The use of a single inverter with a switch system, designed to control the motors of a plurality of panel structures, is also advantageous as it involves significant cost reductions.

In other words, the advantage of the scanning and control device is to allow the memorization of the exact position to orient (this position being valid for all the receiving areas), to perform the scan quickly and with an independent remote structure with low inertia and mechanical criticality. Furthermore, since the command given to the sequential trackers can be advantageously provided, an inverter can be advantageously provided, this solution allowing a double reduction of the mechanical stresses, the first deriving from the fact that the tracking structures and their drives move exactly for what is needed to go into position and the second resulting from the fact that an inverter can be used.

Claims (23)

CLAIMS 1. Method for the operative command of orientation of an absorbing surface of at least one photovoltaic panel, in which it is provided to orient the at least one panel, relative to a support structure of the same, with a rotation movement around at least a first axis, and in which at least one radiation sensor means associated with said at least one panel is provided, the sensor means including a respective sensor surface capturing the luminous radiation, the sensor surface being capable of being rotated around at least a second axis, the method comprising: - a detection phase in which the sensor means is moved in a sequence of angular positions, spaced from each other, around said second axis, in each position a respective signal related to the incident irradiation being detected on the sensor surface, - a phase of comparing the signals detected in said detection phase, to identify the angular position corresponding to the signal correlated with the point of maximum energy production, - a panel orientation control step in which said at least one panel is oriented, with rotation around said first axis, to reach the angular position of maximum energy production identified in said comparison step, characterized by the fact that in said detection phase the capturing surface of the sensor means is moved in said sequence of angular positions with movement independent of the capturing surface of the photovoltaic panel, so that the panel is moved, exclusively, in the control phase, to reach the chosen orientation following the phase of detection and comparison of the signals detected by the sensor means. 2. Method according to claim 1, wherein in the detection step it is provided that the values of the signals detected in each pair of consecutive angular positioning are compared with each other, and both the value of the two relative to the signal of greater energy production than its corresponding angular position, this comparison being repeated for each subsequent angular position assumed by the sensor surface, so that, once the selected angular rotation of the sensor has been completed, the value of the relative signal is kept in memory to maximum energy production with the corresponding angular positioning of the sensor surface. Method according to claim 2, in which the signal relating to the angular positioning of the point of maximum energy production is transferred to control means of motor means arranged to control the orientation of the panel by rotation around said first axis, so that the panel is moved in the corresponding angular positioning of maximum energy production. 4. Method according to claim 3, wherein the rotation of the capturing surface of the irradiation sensor, around said second axis, is controlled by a respective first angular position sensor, said first sensor detecting the angular position reached by the capturing surface of the sensor of irradiation to stop respective first motor means for controlling rotation of the irradiation sensor in each of said angular positions. 5. Method according to claim 4, wherein said first angular position sensor is of the analog type. 6. Method according to claim 4 or 5, wherein the rotation of the panel capturing surface, around said first axis, is controlled by a respective second angular position sensor, said second sensor detecting the angular position reached by the capturing surface of the panel for stopping respective second motor means for controlling the panel in rotation, separated and distinct from said first motor means, in the preselected angular position corresponding to the maximum energy production. 7. Method according to claim 6, wherein said second angular position sensor is of the analog type. Method according to one of the preceding claims, in which, prior to the detection step, a calibration step is provided in which the spatial orientation of the sensor-picking surface is adjusted to make said sensor surface coplanar with the sensor-picking surface. photovoltaic panel. Method according to one of the preceding claims, in which said sensing surface of the sensor is orientable around a respective third axis perpendicular to the second axis. Method according to claim 9, wherein rotation about said third axis is controlled by a respective third angular position sensor. 1 1. Method according to one of claims 8 to 10, in which in the calibration step the capturing surface of the irradiation sensor is rotated around one or both of said second and third axes to reach coplanarity with the capturing surface of the panel. 12. Method according to one of the preceding claims, in which the detection step is carried out by rotating the picking surface of the sensor around the second axis for 120 ° of angular rotation with angular positions in which the detection of the spaced irradiation signal is carried out angularly to each other by 1 °. 13. Method according to one of the preceding claims, in which an electronic circuit assembly is provided in which the signals detected by the irradiation sensor are acquired, the signal values relating to each pair of consecutive angular positioning are compared, the values are stored signal of irradiation and angular positioning of the point of maximum energy production, and from which a command signal is sent to the first motor control means of the panel to rotate the same by a corresponding angle to reach the position of maximum energy production. 14. Method according to claim 13, wherein said irradiation sensor is located in a remote position from the corresponding photovoltaic panel to which it is operatively associated, signal transmission means being provided between the irradiation sensor and the circuit assembly and between this and the photovoltaic panel. 15. Device for controlling the orientation of an absorbing surface of at least one photovoltaic panel, operating according to the method of one or more of the preceding claims. 16. Device according to claim 15, wherein the at least one panel is rotatably supported, about at least a first axis, on a supporting structure, the device comprising at least one radiation sensing means operatively associated with the panel, the sensing means including a respective sensor surface capturing the light radiation, said sensor surface being rotatably supported around at least a second axis, characterized in that the sensor is arranged in a remote position from the panel and is controlled, in the orientation movement around said second axis , independently of the panel. 17. Device according to claim 15 or 16, comprising an angular position sensor operatively associated with the capturing surface of the sensor for controlling the angular positioning of said surface around said second axis. 18. Device according to claim 17, comprising motor means for rotating the picking up surface of the sensor around said second axis. Device according to one of claims 15 to 18, wherein said sensor-absorbing surface is further orientable around a third axis perpendicular to the second axis. 20. Device according to claim 19, comprising a further angular position sensor for controlling the angular positioning of the sensing surface of the sensor around the third axis. 21. Device according to claim 20, wherein said angular positioning sensors are of the analog type. 22. Device according to one of claims 15 to 21, comprising a reversible direct current electric motor for controlling the rotation of the sensor surface around said second axis. Device according to one of claims 15 to 22, in which means are provided for transferring signals between said device and an electronic circuit assembly and between the circuit assembly and respective control means for the capturing surface of the panel.