ITAN20130094A1 - SOLAR TRACKING DEVICE AND CONCENTRATION FOR PHOTOVOLTAIC CELLS - Google Patents

Description

DESCRIPTION

SOLAR TRACKING DEVICE E

CONCENTRATION FOR PHOTOVOLTAIC CELLS.

The present invention relates to the technology relating to photovoltaic power systems, concentrating photovoltaic modules, solar tracking systems and the related manufacturing methods. More particularly, the invention relates to a solar tracking and concentration device for photovoltaic cells.

It is well known that solar trackers are made up of mechanical structures, of different design and construction typology, having the task of supporting a surface for receiving solar radiation, orienting and aligning it optically with the position of the sun during the day.

To date, tracking systems are conceived according to one of the two typical approaches that distinguish the technologies on the market.

The first is the one that foresees the presence of single elements, generally of medium-large dimensions, with a central pillar on the top of which there is a large absorbing surface.

The pillar is able to rotate around its main axis, while the absorbing surface can rotate around an axis perpendicular to the previous one, exploiting different types of motion actuation and transmission mechanisms.

The second approach, on the other hand, presents a multiplicity of small-sized picking elements, they are installed on an articulated frame that moves them simultaneously, having the ability to adjust the inclination of the receiving surfaces by placing them in rotation around one or two axes, to depending on the type of construction.

Both solutions suffer from considerable limitations, including poor installation simplicity and flexibility, limited tracking accuracy, as well as economic limits.

More specifically, the first type of construction suffers the limitation of being only suitable for hosting receiving surfaces of high extension, with consequent considerable dimensions and masses involved: which involves difficulties related to transport and installation, intense structural stresses caused by wind; and, in general, this typology is unsuitable for architectural integrations and â € œrooftopâ € installations.

Furthermore, special equipment (articulated transport vehicles, cranes, etc.) are often required for transport and installation, as well as the presence of a considerable workforce: this translates into correspondingly high costs that discourage the installation of this type in small plants.

The second type, characterized by less installation difficulties, is however less flexible and precise.

In fact, the presence of an articulated frame, although it leads to a decrease in the number of motors necessary for movement, implies a reduced tracking precision, as the rotating axes are not directly coupled to the motors, but are indirectly coupled with the interposition of indispensable drive mechanisms. motion transmission which inevitably introduce backlash and inaccuracies, which lead to a reduction in tracking precision.

Furthermore, the frame constrains the number of elements that can be installed, as well as their arrangement, not allowing in general to modify the configuration of the array of modules during or after installation. To all this is added the fact that, in general, the frames impose a physical limit on the angle that the absorbing surfaces can sweep around the rotation axes. From this it follows that the frames, due to their intrinsic presence, penalize the flexibility of installation, for example excluding the possibility of applications on vertical or inclined surfaces, if not following a targeted design.

Concentrating solar photovoltaic technology, as known, cannot ignore the use of tracking systems as the precise optical alignment with the sun is the prerequisite for the concentration of radiation on the converter element, generally consisting of a photovoltaic cell .

In this regard, it is essential to specify how the amount of electrical power produced increases proportionally with the ability to precisely concentrate the radiation on the cell, maintaining a distribution as homogeneous as possible on the cell surface and avoiding that part of the radiation escapes from the cell and results hopelessly wasted. In particular, this last aspect highlights how the accuracy of the pointing system is fundamental, in the concentration photovoltaic technology, to obtain an efficient and high performance system.

As regards the concentration optics, the first photovoltaic systems were oriented towards two different construction types.

In the first case, a large orientable reflective surface, or a series of articulated mirrors, are directed towards a single point, where the radiation is concentrated and converted.

In the second case, on the other hand, groups of lenses are used, rigidly connected to form extended panels, which focus the solar radiation, each on the reciprocal cell below.

A new approach has recently emerged which aims to combine concentration technology with the reduced size of the more classic silicon panels.

This third type of system, like the previous one, uses groups of lenses, which however are connected in groups of lesser number and extension, such as to allow the formation of smaller, manageable modules, of a size comparable to traditional photovoltaic panels.

However, the solutions proposed so far are linked to the traditional tracking systems described above, therefore they have the same limitations that have been analyzed previously, in particular the limited possibility of architectural integration.

The aim of the present invention is therefore to obviate these drawbacks by means of a tracking system specially designed for application to concentration photovoltaics.

In particular, it is proposed to create an extremely precise modular system in pointing, which is at the same time economical, small in size, and particularly suitable for architectural integrations, which allows flexible installation on any surface, be it horizontal, vertical or in any case. inclined.

According to the present invention, this object is achieved by a solar tracking and concentration device, the characteristics of which can be clearly found in any one of the attached claims, and the advantages of which will become more evident in the detailed description that follows, made with reference to the accompanying drawings. which represent an exemplary embodiment thereof, but not for this limiting of the invention, in which:

- figure 1 is an overall perspective view of the solar tracking and concentration device conforming to the invention;

Figure 2 is a perspective view of a receiver module of the device of Figure 1;

- figure 3 is a perspective view of a module represented with some parts removed to better highlight the others;

- figure 4 is a top plan view of the receiver module of figure 3; - figure 5 is a perspective view of a central base which equips the device of figure 1;

- figure 6 is a perspective view of the base of figure 5 shown with parts removed to better highlight the others;

- figure 7 is a perspective view of a fork with an interconnected secondary shaft equipping the device of figure 1;

- figure 8 is a side view of the fork of figure 7 shown with parts removed to better highlight the others;

- figure 9 is a perspective view of the fork of figure 8;

- figure 10 is a perspective view of an overall configuration of a plurality of devices mounted in pairs and combined in the form of a linear array. In accordance with the attached drawings, figure 1 shows a solar tracking and concentration device for concentrating photovoltaic cells which is indicated as a whole with the number 100.

The concentration of solar radiation by means of lenses, as well as the homogenization of its distribution on the device 100 are not the subject of the present invention, therefore the detailed description of the same will not be the subject of this discussion.

The same applies to the types of photovoltaic cells used and the related assembly and production technologies. For both, known technologies in the field of multi-junction photovoltaic cells are used, which therefore fall outside the scope of the present invention.

The device 100 comprises a central articulated body, configured in such a way as to be able to host, peripherally and preferably four modules 200 collectors and concentrators of the solar radiation coupled in pairs.

More specifically, the following are part of the articulated body: a central base 300, which supports and moves a primary shaft 301; and a pair of forks 400, positioned at the ends of the shaft 301, which in turn support and move two secondary shafts 401, transversal to the primary shaft 301.

As a result of this configuration and arrangement, the articulated body is able to simultaneously rotate all the modules 200 around a primary axis A, identified by the primary shaft 301, while each fork 400 is able to rotation of a pair of modules 200 about a secondary axis B, identified by each of the secondary shafts 401, substantially perpendicular to the primary shaft 301.

As a result of this arrangement, the modules 200 are arranged so that, in each pair, each module 200 is symmetrical to the other with respect to a plane passing through the A axis and perpendicular to each plane identified by one of the B axes and from the same axis A.

The two pairs of modules 200 are also arranged equidistant with respect to the plane of symmetry of the primary shaft 301, perpendicular to the A axis.

The embodiment just described allows a balanced spatial arrangement of the masses around the central base 300. This feature allows the use of small size and power stepper motors with considerable advantage, with evident benefits in terms of reduction of the general construction and component costs, as well as to the advantage of a better overall energy balance of the device 100. Figure 2 shows the external structure of the collector and concentrator module 200 presented according to a first configuration. At the base of the module 200 there is a metal plate 201 which has the function of hosting the multi-junction photovoltaic cells 205 on its own upper surface, inside the module 200 (Figure 3). At the top of module 200 there is a 206 lens plane, or more generally an equivalent pick-up organ exposed directly to solar radiation.

In the example of embodiment of the invention described here, the pick-up organ 206 is identified as a plane of shaped lenses which are formed on a plastic or glass surface. The lower surface of the top has particular grooves designed to form concentric annular sections whose purpose is to concentrate the light radiation captured according to the well-known Fresnel principle.

A plastic casing 204 is interposed between the metallic base 201 and the lens plane 206 which identifies an external closed surface preferably shaped complementarily with the contour geometry of the lens plate 201 and the plane 206. Said casing 204 starts perpendicularly from the opposite surface to the capturing surface of the lens plane 206, projecting in cantilever towards the underlying metal plate 201.

From the assembly of the three elements previously described, a closed volume is defined, inside the module 200 which allows to house the multi-junction cells 205 and the relative wiring.

It is also clearly visible in figure 2 and even better in figure 3 that one of the two vertical surfaces corresponding to the longer side of the plane 206 has a circular hole that allows the secondary shaft 401 to pass through for coupling inside the module with a rigidly connected tubular sleeve 203; tubular sleeve 203 which is coaxial with the rotation axis B and which allows one of the two movements necessary to orient the modules 200 in space to be carried out (as will become clearer below).

The position of the hole on the casing 204, from which the distance of the tubular sleeve 203 from the base plate 201 derives, is preferably conceived in such a way that the axis of rotation B passes through the center of gravity of the module 200. it allows to minimize the driving torque of the rotation of a pair of modules 200 and of the relative tubular sleeve 203, substantially reducing it to the driving torque necessary to overcome the mechanical frictions that oppose the rotation.

This feature, together with what has been previously described with regard to the spatial arrangement of the modules 200, contributes to obtaining the significant benefit of reducing the size of the necessary motors, with the undoubted advantages described above.

However, it should be noted that said module 200 can also assume forms other than the one exemplified, being able to be equipped for example with a plane 206 of spherical, conventional lenses, replacing the plane 206 of Fresnel lenses, or being able to assume different geometric shapes, without for this is beyond the technical scope of the present invention.

Figure 3 allows, in particular, to identify the components housed entirely in the closed volume of the module 200, i.e. a pair of vertical uprights 202, arranged close to the external casing 204 which structurally connect the lens top 206 and the underlying plate 201, and which are preferably made of a material with high inherent rigidity.

Perpendicularly to the main dimension of the uprights 202, arranged in a substantially intermediate position between the plate 201 and the lens plane 206, there is - as said - the tubular sleeve 203. This is preferably equipped therein with a cylindrical tubular shape, flanged at the ends, which lends itself well to being firmly fixed to the two uprights 202, helping to give adequate stiffness to the module 200 as well as to transmit to it the rigid rotation around the B axis received from the secondary 401 tree.

From Figure 3, and even better from Figure 4, it can be seen that the sets of photovoltaic cells 205 are arranged on the upper face of the plate 201. The cells 205 are preferably arranged according to an array of two rows of four elements each, for a total of eight cells 205 per module 200. This arrangement is congruent with the position of the overlying lenses of the plane 206 lenses, so that the beam of light deflected by the lens accurately hits the corresponding cell 205.

It clearly emerges that this arrangement is entirely exemplary and non-limiting as there are various possibilities regarding both the arrangement of the cells 205 and their number per module 200, depending on the shape and size of the lens plane 206.

The base 300 central to the modules 200 sensors and concentrators - represented in figure 5 - is made up, externally, of a base plate 302, of two pairs of side walls 303 and 304 two by two opposite each other, as well as transversal and longitudinal respectively. primary A axis; of an upper cover 305, and of two support elements 306 and 307 for the relative electric stepper motor 309.

The side walls 303 and 304 are made of rigid and resistant material, preferably metal, as they must support two motor shafts 301 and 308, whose axes are identified with the letters A and C. In particular, the pair of side walls 303 must support shaft 301, on the ends of which the two forks 400 and the relative modules 200 are housed. Therefore, the side walls 303 are required to support the weight of the entire device 100. The side walls 303 and 304 have holes 500a and 500b which allow the fixing of ball bearings, flanged, housed inside the base 300. In this exemplary form the holes 500a are smooth and through, that is, they pass through the respective walls 303 and 304. The holes 500b, obtained on the respective walls 303 and 304, are instead threaded for the insertion of clamping screws of the bearings to the respective walls 303 and 304.

In this configuration, as can be clearly seen in Figure 6, the walls 303 and 304 have excavations which together define a seat 501 intended to house the upper lid 305. The support for the stepping motor 309 is made by means of two of the aforementioned metal elements 306 and 307 specially coupled.

More specifically, element 306 is made up of an elongated sheet metal, bent at an elbow. Its shape allows: on the one hand, the coupling with the plate 307 for fixing the motor, on the other hand, the insertion in a special slot obtained between the base plate 302 and the side wall 304 for fixing with the rest of the base.

In fact, from the combined observation of figures 5 and 6 it is possible to note that the rigid plate 307 is shaped in such a way as to allow the housing of the stepper motor 309 and the coupling of the relative shaft pin 308 motor which is substantially perpendicular to the primary shaft 301. In particular, the motor shaft pin 308 penetrates inside the crankcase 300 crossing the side wall 304; it is made to rotate about its axis C by the motor 309; and rotates shaft 301 around axis A by means of an interposed motion transmission system.

The transmission system includes, in particular, a worm screw mechanism identified by a pair of elements: a screw 311, integral with the shaft 309, and a screw wheel 312, bound to the primary shaft 301.

By means of the motion transmission system housed inside the crankcase 300 and the components described above, it is possible to use the stepping motor 309 to rotate the primary shaft 301 around its A axis.

Figure 6 also allows the four ball bearings 310 to be viewed. They are arranged in symmetrical pairs on the internal faces of the walls 303 and 304. The bearings 310, with their position, uniquely identify the axes A and C, allowing the shafts 301 and 308 to rotate freely around the axes A and C themselves.

An important aspect of the present configuration is that, since it does not have any physical limit that constrains the possibility of rotation, the shaft 301 is able to rotate for 360 ° around its axis A, being able to assume all the desired orientations without no limit on the resulting position of the modules 200 around axis A.

However, it should be noted that said elements can also assume shapes other than those exemplified, for example they can have geometries of various kinds or present different solutions belonging to the known techniques for reciprocal fixing and bearings, as well as for the transmission of motion. Figure 7 shows the entire fork 400 coupled with the secondary shaft 401 which rotates around the B axis.

The fork 400 is presented as a closed central body, under which an electric step-by-step motor 410 is installed, supported by a support completely similar to that described in the base 300.

The central body of the 400 fork is made up of a first rigid member 402 which allows the connection with the primary shaft 301, and to which two further rigid members 403 and 404 are connected, which make up the side faces of the 400 true and own.

The central body is closed by an upper lid 406 and a lower lid 407. Both are suitably shaped around the profile identified by the elements 402, 403 and 404.

The assembly of the three rigid members 402,403 and 404 and of the two lids 406 and 407 identifies a closed space inside the central body and of adequate volume, in which the components for the transmission of motion are housed.

The 410 stepper motor is housed under the central body of the fork 400 in such a way that the motor pin 502 (figure 8) of said 410 motor is oriented perpendicularly to the B axis and enters the body center of the fork 400 by means of two suitable holes made respectively on a relative support plate 409 and on the lower cover 407.

The external structure of the fork 400 is completed by a pair of flanged ball bearings 405, mounted on the external faces of members 403 and 404. They have the task of supporting the secondary shaft 401, together with the pair of associated modules 200, allowing its free rotation around the B axis.

The three rigid members mentioned above, that is the rigid bodies 402, 403 and 404, are preferably made of metallic material, or in any case of rigid and resistant material, as they have the task of supporting the weight of the shaft 401 and the pair of 200 modules placed at the end of the shaft 401 itself, unloading it on the central shaft 301.

On the contrary, the two covers 406 and 407, which have the sole function of protecting the components for the transmission of motion housed inside the fork 400, can be made of less valuable materials, such as plastics and polymers of various kinds.

The elements suitable for transmitting the motion from the engine 410 to the shaft 401 are housed inside the closed volume. As can be clearly seen in figure 8, it is a pair of toothed wheels 411 and 412 with perpendicular axes. In this representation, helical toothed wheels 411 and 412 are preferably considered. However, they could be replaced, for example, by a pair of bevel wheels or equivalent components of another kind belonging to the known techniques for transmitting the rotary motion between two perpendicular axes.

The smaller sprocket 412 is rigidly connected to the pin 502 of the 410 stepper motor. The coupling is made at the upper end of its internal portion to the body of the fork 400. The second toothed wheel 411, which has larger dimensions, is coupled with the secondary shaft 401, the orientation of its axis is therefore substantially perpendicular: both, to the pin 502 of the motor 410, and to the main shaft 301.

Figure 9 highlights the motion transmission mechanism with greater descriptive efficacy. The 410 stepper motor is equipped with a pin 502 which, extending in the form of a shaft entering the body of the fork 400, and rotating around the axis D, rotates the toothed wheel 412.

The toothed wheel 412, meshing with the toothed wheel 411 coupled to it, causes the latter wheel 411 to rotate around the axis B. By means of the rigid connection of this last wheel 411 with the shaft 401, the The entire shaft 401 is therefore dragged in rotation around its main axis B, substantially perpendicular to axis D.

From the configuration just described, like what has been described for the base 300 and the shaft 301, the significant advantage emerges that, thanks to the absence of physical constraints, also the shaft 401 is able to rotate for 360 ° around its own B axis, without any limit on the resulting position of the modules around the B axis itself.

This configuration, in which each receiver module 200 is arranged at the end of a shaft 401, also makes it possible to facilitate assembly and maintenance operations, allowing at least the replacement of any damaged or malfunctioning modules 200, while keeping the rest of the structure.

As far as the embodiment of the gearmotors is concerned, 7.5 ° stepping motors are preferably used, coupled with gearboxes with a high reduction ratio, for example 1500: 1 which, combined with each other, allow to obtain extremely high angular resolutions, of the order of 0.005 ° at each step.

The possibility of handling with such a high degree of angular resolution guarantees maximum pointing precision, with obvious benefits compared to the production of electrical power. In fact, as previously mentioned, the electric power produced is a direct consequence of the ability of the concentrated light beam to precisely invest the cell 205 in its entirety and with homogeneous distribution, and in particular to prevent part of the light beam from escaping from the cell 205, i.e. that part of the radiation is irretrievably wasted. A further advantage of the present invention is precisely that of being able to use stepper motors as moving members of the primary and secondary shafts 301 which allow the spatial orientation of the modules 200, being able to manage them with simple action control means. This allows, for example with respect to feedback controls, to greatly simplify the control system, without however renouncing to have a high pointing precision.

The embodiment of the device 100 just described is easy and inexpensive to produce. This aspect, combined with the extremely limited masses and overall dimensions, makes it particularly suitable for the constitution of batteries of devices 110 (Figure 10). This means that a multiplicity of devices 100 can be arranged together among them, according to the most suitable spatial location to adapt to the actually available support surface and to minimize the mutual shading between the modules 200 of the different devices 100. In this way it is possible to create collection systems of various size and power, scalable in an economic way and also susceptible of relatively simple and reliable management of their control.

In this regard, Figure 10 shows an installation of four devices 100 arranged according to a linear array. In this arrangement, to be considered only as an example and in no way binding, they are fixed on a pair of standard metal profiles 500 housed parallel to axis B, below the central base 300 of the various devices 100.

The 500 metal profiles are standardized components available on the market in many sizes. They range over extremely variable lengths and dimensions of the section, they also have numerous solutions for fixing on surfaces of any type and in any case oriented, aspects that allow them to adapt to any application and that make this technology the most widespread in the sector of supports for standard solar panels. The possibility of applying the device 100 object of the present invention on this type of profiles represents an undoubted advantage in terms of flexibility of installation and the possibility of modifications or replacements, an aspect which makes it extremely suitable for architectural integrations with existing buildings or buildings under construction. This aspect also makes it possible to use the devices 100 in question in all cases in which you want to replace a photovoltaic system already present on the building but near the end of its life cycle with a more modern and efficient solution. In this case, in fact, it is possible to reuse the support structure already present, at the limit re-adapting it to the desired geometry, with a considerable cost saving and reduction of the investment payback times.

A further advantage deriving from this aspect, combined with the reduced dimensions and weight of the device 100, the attractive design, as well as the possibility of the shafts 301 and 401 to rotate completely around their axes, is to allow installations on vertical surfaces or in any case. oriented. A further consequence of the possibility of the shafts 301 and 401 to rotate completely around their own axes is that, contrary to most of the known technologies which must be oriented according to a prevailing direction (typically north-south), the device 100 does not require any details. spatial orientations, it can therefore be installed with the axes arranged in any direction. This aspect further underlines its strong vocation for architectural integrations, presenting the undisputed benefit of adapting to those surfaces (such as vertical walls facing south, edges and thin-geometry pylons) that could not accommodate traditional photovoltaic systems, nor concentration plants of different nature.

The invention thus conceived is susceptible of evident industrial application; it can also be subject to numerous modifications and variations, all of which are within the scope of the inventive concept; all the details can also be modified by replacing them with technically equivalent elements.

The invention thus conceived is susceptible of evident industrial application; it can also be subject to numerous modifications and variations, equivalent, all falling within the scope of the present invention.

Furthermore, the materials used to manufacture the device according to the present invention, as well as the individual shapes and dimensions of the component parts, can be chosen in such a way as to appropriately achieve each specific requirement of the invention without thereby departing from the scope of the present invention. .

Claims (8)

CLAIMS 1. Solar tracking and concentration device for photovoltaic cells, comprising at least one organ (200) collecting and concentrating solar radiation, characterized in that it comprises at least one central base (300) which supports said one or each sensor member (200) of long cantilever, and rotatably around at least one of, distinct directions of two axes (A, B), said two axes (A, B) defining a plane of lying which can be freely orientated in space around one (A) of said two axes (A, B), which axis (A) is fixed with respect to the base (300), further said base (300) comprising a base plate (302) which is substantially parallel to said fixed axis (A); angular rigid connection means (400) binding said axes (A, B) to remain in said lying plane; and motorization means (309,311,312; 410,412,411) which independently rotate said one or each sensor member (200) around one or the other of said axes (A, B), to correspondingly vary their orientation with respect to the sun. 2. Device, according to claim 1, characterized in that it comprises at least one pair of motorized shafts (301,401), one of which is primary and one secondary, which are coaxial with, and rotatable about, said directions of said axes ( A, B). 3. Device, according to claim 2, characterized in that said angular rigid connection means include a fork (400) interposed to the primary and secondary shafts (301,401) of said at least one pair, which are carried by said base (300) in mutual continuation. 4. Device according to one of the preceding claims, characterized in that said base (300) supports at least two pairs of said primary and secondary shafts (301,401) supporting at least one said picking member (200), which pairs are supported bilaterally to said base (300). 5. Device, according to claim 3, characterized in that said base (300) supports two pairs of said pickup and concentrator members (200) located bilaterally to the base (300), each member (200) of said pair being provided with a own secondary shaft (401) connected with a common primary shaft (301). 6. Device, according to one of claims 3 to 5, characterized in that said motorization means include gearmotors (309,311,312; 410,412,411) respectively independently activating the rotation of said primary and secondary shafts (301,401) of said at least one pair around the respective rotation axes (A, B). 7. Device according to claim 6, characterized in that said gearmotors include electric stepper motors (309,410). 8. Device, according to claim 6 or 7, characterized in that said gearmotors include a gear (311,312; 412,411) which receives motion from said stepper motor (309,410) and transmits it to a corresponding said primary shaft (301) or secondary (410). Device according to one of the preceding claims, characterized in that said one or each picking member (200) supports multi-junction photovoltaic cells (250).