BIFACIAL PHOTOVOLTAIC MODULE, SINGLE AXIS SOLAR TRACKER AND OPERATING METHOD THEREOF

Abstract

Solar trackers are designed to withstand high wind loads, eventually by oversizing the structure and incurring in higher material cost and rendering high costs scenarios when deploying solar trackers in solar fields. A solar tracker and a method for operating the solar tracker yields a solution highly structured solar trackers by providing a single horizontal axis solar tracker associated to at least one bifacial photovoltaic module. The single horizontal axis solar tracker has a bifacial photovoltaic module associated to the torque tube using a joint fixture along one of the sides of the bifacial solar module so that the solar module jointly moves when the torque tube rotates. The single horizontal axis solar tracker may be operating according to the time of the day consequently to the available sunlight, so that a face of the bifacial photovoltaic module associated to the torque tube is facing the sun.

Claims

1.-21. (canceled)

22. A solar tracking method using a single horizontal axis solar tracker, the single horizontal axis solar tracker associated to at least one bifacial photovoltaic module, the single horizontal axis solar tracker comprising: an arrangement of bifacial photovoltaic modules fixed to a torque tube, of the solar tracker, the torque tube being supported by several posts by articulated joints and said posts fixed to the ground, and the bifacial photovoltaic module being associated to the torque tube by a joint fixture along one of the sides of the bifacial solar module in such a way that the solar module jointly moves when the torque tube rotates; the method comprising the step of: operating the torque tube for gradually positioning the bifacial photovoltaic module in such a way that either the front face or the back face of the bifacial photovoltaic module faces the sun from dawn to noon.

23. The method of claim 22, further comprising the step of: operating the torque tube for gradually positioning the bifacial photovoltaic module in such a way that either the front face or back face of the bifacial photovoltaic module faces the sun from noon to sunset.

24. The method of claim 23, further comprising the step of: operating the torque tube for arranging the bifacial photovoltaic module essentially orthogonal in respect to the post in case high-speed winds are determined.

25. The method of claim 24, further comprising the step of: operating the torque tube for positioning the bifacial photovoltaic module to an angular limit towards the east in case wind direction is determined to mainly come from east.

26. The method of claim 24, further comprising the step of: operating the torque tube for positioning the bifacial photovoltaic module to an angular limit towards the west in case wind direction is determined to mainly come from west.

Description

DESCRIPTION OF THE INVENTION

[0020] FIG. 1Shows a side view of solar tracker of the invention wherein the solar modules are in a vertical position, at a 0 degrees angle and the modules are arranged in landscape orientation.

[0021] FIG. 2Shows a front view of solar tracker of the invention wherein the solar modules are in a vertical position, at a 0 degrees angle.

[0022] FIG. 3Shows a front view of solar tracker of the invention wherein the solar modules are in a horizontal position, at a 90 degrees angle (FIG. 3a) and 90 degrees angle (FIG. 3b).

[0023] FIG. 4Shows a front view diagram depicting a standard tracking procedure for a day.

[0024] FIG. 5Shows a diagram depicting an array of solar trackers wherein the solar modules is set to a horizontal defensive position, facing the wind direction.

[0025] FIG. 6.Shows a 3D representation of the object of the invention wherein the torque tube is driven by an actuator arranged on the central post and the modules are arranged in portrait orientation.

[0026] FIG. 7.Shows a schematic representation of a preferred embodiment of a photovoltaic module according to the invention, with split cells wherein, for the sake of simplicity, a first side is shown on the left and a second side, opposite to the first side, is shown on the right.

[0027] FIG. 8.Shows a cross-section side view of the module of FIG. 1.

DETAILED DESCRIPTION

[0028] In a preferred embodiment of the object of the invention a single horizontal axis solar tracker associated to at least one bifacial photovoltaic module (1) is provided as the one shown in FIGS. 1-3. For this preferred embodiment and in a non-limiting manner, the single horizontal axis solar tracker associated to at least one bifacial photovoltaic module (1) of the invention comprises said bifacial photovoltaic module (1) attached to the torque tube (2) by articulated joints, preferably by means of bearings (5). The solar tracker of the invention comprises the torque tube (2) supported by a post (3) fixed to the ground, consequently the solar tracker is fixed to the ground by means of posts (3) holding the torque tube (2); hence, any reference to angles is to be understood as being referred to the longitudinal axis of said posts (3).

[0029] The single horizontal axis solar tracker of the invention comprises the bifacial photovoltaic modules (1), preferably rectangular, with one of its sides, preferably a long one, jointly attached to the torque tube (2) so that one of the long sides of the panel remain integral with the torque tube (2) in the longitudinal direction, wherein the bifacial photovoltaic module (1) is fixed in an unbalanced way, being at maximum torque when the bifacial photovoltaic module (1) is positioned aligned with their horizontal plane; defining a cantilever preferably equivalent to approximately to the width of the bifacial photovoltaic module (1). In other words, the bifacial photovoltaic module (1) is associated to the torque tube (2) by means of a joint fixture along one of the sides of the bifacial solar module in such way that the solar module jointly moves when the torque tube (2) rotates.

[0030] The solar tracker of the invention presents the torque tube (2) having a round section (as per FIG. 2) or a square section (as per FIG. 6) and arranged at a height above ground of around 0.5 meters or 20 inches having the bifacial photovoltaic module (1) a height of around 1 meter or 40 inches, thus rendering a total height of around 1.5 meters or 5 feet, allowing an easy deployment of the solar tracker without heavy and/or special machinery.

[0031] In a preferred embodiment of the object of the invention the torque tube (2) is driven by a motor or actuators (4) as in FIG. 6, this allows a controlled movement of the bifacial photovoltaic module (1).

[0032] The method of the invention basically comprises gradually positioning, driven by the torque tube (2), the bifacial photovoltaic module (1) in such a way that the front face (11) of the bifacial photovoltaic module (1) faces the sun from dawn to noon and that the back face (12) of the bifacial photovoltaic module (1) faces the sun from noon to sunset as per FIGS. 3a and 3b.

[0033] Using a clock hands pattern, the method of the invention may be described in view of FIG. 4 as follows: [0034] From dawn to noon, the solar tracker of the invention would start solar tracking mode in such a way that a front face (11) of the bifacial photovoltaic module (1) faces the sun, being gradually positioned at 90 with respect to the longitudinal axis of the post (3) at noon, shifting from a close to 12 h to a close to 9 h position of an hour hand in a watch. Rendering the situation depicted by FIG. 3a. [0035] After noon, it is required a movement from west to east so that the bifacial photovoltaic module (1) has a back face (12) of the bifacial photovoltaic module (1) facing the sun. With this movement the panels shift from close to 9 h to a close to 3 h position of an hour hand in a watch. [0036] Gradually positioning, from noon to sunset, the bifacial photovoltaic module (1) with its back face facing the sun to a position of 90 with respect to the longitudinal axis of the post (3), shifting from a close to 3 h to a close to 12 h position of an hour hand in a watch. Rendering the situation depicted by FIG. 3b.

[0037] Additionally, the method of the invention may comprise a backtracking operating mode, so that to avoid shadowing effects, in this preferred embodiment, the progressive movement of the bifacial photovoltaic module (1) driven by the torque tube (2) is limited by a limited angular range previously defined. This range will depend on the size and orientation of the bifacial photovoltaic module (1) over the torque tube (2) and the height of the torque tube (2) above the ground level. For a typical landscape orientation of standard modules and 20 inches or 0.5 meters of torque tube (2) height, the limited angular range would be 240 degrees or +/120 from the vertical.

[0038] In case of high-speed winds, the bifacial photovoltaic module (1) can be placed in a horizontal position, essentially orthogonal in respect to the post (3), and even exceed that position to even touch the ground, as depicted in FIG. 5.

[0039] Furthermore, the method of the invention may further envisage arranging the bifacial photovoltaic module (1) in an essentially horizontal position in case high-speed winds are determined or at a minimum angular position to reach the angular limit in case high-speed winds are determined. This positioning embraces operating the solar tracker so the bifacial photovoltaic module (1) is moved to the east in case wind direction is determined to come mainly come from east or to the west in case wind direction is determined to mainly come from west.

[0040] Thanks to the low profile of this type of solar tracker, considerable savings in the use of material (mainly steel) are estimated, mainly due to its limited exposure to the wind. A detailed structural study is necessary to be able to evaluate the potential savings in the most key elements: torque tube (2), drives and actuators.

[0041] The photovoltaic module (1) comprises, as shown on FIG. 7, a first module face (12), oriented according to a first direction and a second module face (13), opposite to the first module face (12) and, therefore, oriented according to a second direction, opposite to the first direction. A plurality of bifacial cells (4, 5) are mounted in the module (1), each of which comprises a first cell face, with a greater pick-up capacity, and a second cell face, with a lower pick-up capacity. Advantageously, the bifacial cells (14, 15) comprise first bifacial cells (14), oriented with a first cell face towards the front direction, and a second cell face towards the rear direction; and second bifacial cells (15), oriented with the second cell face towards the front direction and the first cell face towards the rear direction. One or more first internal chains connect the first bifacial cells (4) in series, while one or more second internal chains connect the second bifacial cells (5) in series, the first internal chain and the second internal chain being connected to each other in parallel, to generate the output of the photovoltaic module (1).

[0042] The first bifacial cells (14) and the second bifacial cells (15) are preferably of the type called split cells (known interchangeably in English as half-cell or half-cut). In this case, the use of several first and second internal chains is particularly advantageous. Each group of first bifacial cells (4) and second bifacial cells (5)in your case, each of the first and second internal chainscan have its bifacial cells (4, 5) grouped into one or more respective first zones and second zones, to facilitate the connections between the bifacial cells (4, 5) of each internal chain. Alternatively, the bifacial cells (4, 5) can be uniformly distributed along the module (1), to gain robustness against shadow and/or cloud situations.

[0043] The first module face (12) and the second module face (13) may incorporate a transparent cover (18, 9), such that, for example, made of tempered glass, to protect the bifacial cells (14, 15) weather conditions. For better performance, it is preferred that the covers have some anti-reflective treatment. As shown in FIG. 8, the module (1) comprises two encapsulating sheets (16, 17) so the bifacial cells (14, 15) are protected by forming an encapsulation; furthermore, the two covers (18, 19) may be provided with an antireflection treatment, between which the encapsulation is enclosed.