IL291309B2 - A method of photovoltaic module mounting - Google Patents

Description

Docket 231-002-IL - 1 - APPLICATION FOR PATENT Inventor: FINAROV, Moshe Title: A METHOD OF PHOTOVOLTAIC MODULE MOUNTING TECHNOLOGY FIELD [0001] The present disclosure relates to the mounting and operation of photovoltaic (PV) modules, particularly photovoltaic modules intended for dual use in agriculture and other areas. BACKGROUND [0002] Photovoltaic (PV) modules or panels are widely used in roof-top and ground solar power installations. Usually, the photovoltaic modules installations are rows of photovoltaic modules or panels either slightly tilted or rotated at an angle to the South with some distance between the rows or fully horizontal photovoltaic modules in dense arrangements. This type of installation of photovoltaic modules is termed a North-South or N/S mounting or installation. The installation site latitude could require adjustments in photovoltaic panel orientation and the tilt angle. Recently bifacial photovoltaic modules with high bifaciality (>80%) have become available. The additional photovoltaic efficiency gain for these panels, 5% to 15% compared to the mono facial (single side) photovoltaic modules, depends on installation arrangement and the localized albedo. [0003] Bifacial photovoltaic modules support a new type of installation of solar photovoltaic panels, namely vertical photovoltaic mounting (also termed East-West or E/W mounting). In the East-West photovoltaic panels installation, one side of the photovoltaic module collects sunlight before noon, and the other side of the photovoltaic module collects the sunlight afternoon.

Docket 231-002-IL - 2 - [0004] U.S. Patent Application Publication No. 2020/0153380 A1 to Heiko Hildebrandt, teaches "a photovoltaic system in which a plurality of bifacial photovoltaic modules can be mounted in a vertical arrangement and which satisfies the specific requirements of bifacial modules. In addition, the supporting structure is intended to have sufficient stability in typical weather conditions in particular against the wind." [0005] In a paper presented on 35th European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC 2018), Brussels, September 2018 titled "PERFORMANCE ANALYSIS OF VERTICALLY MOUNTED BIFACIAL PV MODULES ON GREEN ROOF SYSTEM" by Thomas Baumann et al., reported that "according to simulations, vertically mounted bifacial modules can have a higher electrical energy yield than standard bifacial installations depending on the location and the installation conditions." [0006] The vertical photovoltaic panels type of installation with significant distance between rows (6m -10m) of the photovoltaic panels is beneficial for dual use in agriculture because it supports a minimal photovoltaic panel footprint, leaving most of the ground area for agriculture needs between the rows. O.A.Katsikogiannis et al., in a paper titled "Integration of bifacial photovoltaics in agrivoltaic systems: A synergistic design approach", Applied Energy 309 (2022) 118475, analyzed different types of installations of bifacial PV modules. In particular, the authors emphasize that "East-West vertical topologies amplified light penetration, especially during the winter months; accordingly, they are preferable for the cultivation of permanent crops that are grown throughout the year, while South-North facing photovoltaic panels installations are more suitable for summer. [0007] Additional advantages of the vertical photovoltaic modules include: smaller shading, which is important for many crop types, e.g., for potato, and low contamination by air particles (as most of the air particles fall vertically on the ground), the vertical photovoltaic modules require less maintenance for cleaning. [0008] Traditional horizontally mounted photovoltaic panels generate the maximal electrical power at noon hours. In the case of the vertical photovoltaic panels installation, there is a significant dip in electrical power generation around the noontime. The direct sunlight does not pass through the cover glass to the photovoltaic module's silicon Docket 231-002-IL - 3 - photovoltaic cells at noontime. Only the diffused reflected from the ground and clouds light penetrates the vertical photovoltaic panel around the noontime, so the generated electrical power does not fall down to zero. [0009] Sun tracking could significantly enhance photovoltaic power generation by all types of photovoltaic modules. The theoretical basis of sun-tracking is described, e.g., in Luque and Hegedus (eds.) 2011, Handbook of photovoltaic science and engineering, pages 276-277. Currently, many industrial companies manufacture sun trackers for photovoltaic panels. The widely used type of sun tracker is a single-axis tracker, which rotates the photovoltaic panel according to the sun movement and maintains the receiving surface of the photovoltaic panel plane always perpendicular to the sun azimuth (which defines the direct sun radiation). Because of the sun-tracking, the collection of the direct sun radiation by the photovoltaic panel is maximal during the day. Collecting the diffused sunlight by both sides of bifacial photovoltaic modules with regular sun tracking is less efficient than by vertical photovoltaic modules. The sun-tracking mounts also have drawbacks for dual-use applications, such as greater shadowing of the ground nearby and higher soiling relative to the vertical photovoltaic modules mounting. DEFINITIONS [0010] As used in the current disclosure, the term "bifaciality" defines the photovoltaic panel rear side efficiency ratio to the front side efficiency, measured under standard test conditions. [0011] Albedo is a non-dimensional, unitless quantity that indicates how well the Earth surface reflects solar radiation. Albedo varies between 0 and 1. Albedo commonly refers to the "whiteness" of a surface, with 0 (zero) meaning black (e.g., asphalt) and 1 (one) meaning white (e.g., snow). [0012] The current disclosure uses the term vertical plane, that means a virtual plane perpendicular to the ground. [0013] As used in the current disclosure, a pivot is a rotation axis in the vertical plane, which is parallel to the ground, the tracking is a rotation of the PV panel plane around the Docket 231-002-IL - 4 - pivot, and a tilt angle is an angle between the photovoltaic panel plane and the vertical plane. [0014] As used in the current disclosure, a tilt angle of a PV module is 0° when the photovoltaic module’s plane is in the vertical plane, and its front side faces the East; the tilt angle is 180° when the photovoltaic module plane is in the vertical plane, and the front side faces the West. [0015] As used in the current disclosure (where a left side of the drawings is faced to the East), the photovoltaic modules rotating direction is positive when the photovoltaic module is rotated clockwise, from 0° to 180°, through 90° (which is the horizontal plane). Accordingly, the rotating direction is negative if the photovoltaic panel rotates counterclockwise. SUMMARY [0016] The present disclosure describes a Swing photovoltaic module mounting and operation, which is a method that combines the advantages of vertical photovoltaic module mounting for dual-use application and tracking mount for increasing light-harvesting throughout the daytime. LISTING OF DRAWINGS AND THEIR BRIEF DESCRIPTION [0017] A reference is made to the accompanying drawings to understand examples of the method and apparatus better and illustrate how it could be carried into effect. Referral numerals designate identical or similar elements throughout the document. [0018] FIG. 1 is a schematic view of a swing photovoltaic modules mount; [0019] FIGS. FIGS. 2A through FIG. 2C illustrate three specific angular positions of the swing photovoltaic module during rotation through a day; [0020] FIGS. 3A through 3D illustrates in more details the different angular positions of the swing photovoltaic module during the rotation sequence; Docket 231-002-IL - 5 - [0021] FIGS. 4A through 4D illustrate different angular positions of vane alarm controlled swing photovoltaic module rotation sequence in a high wind load; and [0022] FIG. 5 illustrate a comparison of the AC power generated by a Swing photovoltaic installation compared to a static vertical photovoltaic module installation. [0023] For simplicity and clarity of explanation, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements. DESCRIPTION [0024] The traditional horizontal, usually tilted towards the South, the photovoltaic panel mount occupies a relatively large (ground surface) footprint. The vertical photovoltaic module mount installations generating a similar electric power occupying a significantly smaller footprint. The ground surface available for conventional photovoltaic modules horizontally mounted installations is limited. A dual-use photovoltaic panel helps to overcome this limitation. Such installations are associated with several challenges related to sunlight shading, accessibility for modules cleaning as well as to a cost of installation and maintenance. [0025] The dual-use photovoltaic module is related mainly to agriculture (AgriPV –crops, and pasture). Installing the vertical photovoltaic modules above plants, for example, on posts, or aside garden beds or around the fields, releases the ground for agricultural use; however it is very costly both in installation and maintenance. [0026] Recently, the scope of dual-use vertical photovoltaic modules was broadened to other fields beyond arable land of field crops like pasture land, water reservoirs, and solar fences around settlements, roads, and railways. In all these applications, the vertical photovoltaic module mount, characterized by a minimal possible footprint, easy maintenance, and relatively low cost, provides significant advantages relative to other types of photovoltaic modules mounts. [0027] Solar power systems employing vertical photovoltaic modules are typically implemented as rows ("solar fences") located along the South-North direction at a Docket 231-002-IL - 6 - relatively large distance between each other (usually 6m to 10m). On one hand, such sparse installations minimize mutual shading, especially around noon, and provide sufficient space for tractors or other machines used in agriculture. On the other hand, the significant distance between the vertical photovoltaic modules causes a lower power throughput per a unit of the installation area. [0028] Therefore, there is a technical challenge – to improve power throughput of vertical photovoltaic module systems per an area unit keeping as much as possible all the advantages of the vertical photovoltaic modules mount for dual use: small footprint, low shading at around noon hours (when the sunlight radiation is the highest throughout the daytime), low soiling and possibility to work at high wind load, which is mainly related to the high wind speed. The current disclosure describes certain solutions for the above technical challenge. [0029] The present disclosure provides an efficient method of enhancing the power throughput of the vertical photovoltaic ground systems by swinging one or more bifacial photovoltaic modules in a row to a relatively small angle T relative to the vertical, at first before noon and then to a complementary angle equal to (180°-T) afternoon. The current disclosure terms such vertical photovoltaic panels mounting as a Swing vertical photovoltaic module mounting. [0030] The following description presents various aspects of the present system and method. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the present disclosure. However, it will also be apparent to one skilled in the art that the present system and method could be practiced without the specific details presented herein. Not to obscure the present disclosure, some known features have been omitted or simplified. [0031] The disclosure supports the use of swing photovoltaic panels in different dual-use applications: Agri-PV, fences around settlements, water reservoirs, fences along roads and railways, and other objects. [0032] FIG. 1 is a schematic view of a swing photovoltaic module mount. The figure illustrates one of the possible implementations of a swing photovoltaic module mount. Posts 104 could be installed directly inside ground 101, or specially constructed concrete Docket 231-002-IL - 7 - supports 208 (FIG. 2). System 100 includes at least one bifacial photovoltaic module 102. The particular system depicted in FIG. 1 includes three vertical photovoltaic modules 102. A pivot axis 103, mounted between two posts 104, connects vertical photovoltaic modules 102. Pivot axis 103 also serves as a common rotation axis for vertical photovoltaic modules 102. Each of modules 102 could be tilted or rotated around pivot axis 103 to an angle 107 measured between the photovoltaic module edge 106 and vertical 105. The angle 107 will also be called a "tilt angle T". The pivot axis 103 is located along the South-North direction. [0033] FIGS. 2A through FIG. 2C illustrate three specific angular positions of the swing photovoltaic module rotation through a day. Initial position FIG. 2A (zero degrees rotation), intermediate horizontal position FIG. 2B (ninety degrees rotation), and the final second vertical position FIG. 2C (one hundred eighty degrees rotation). [0034] FIGS.3A through 3D illustrates in more detail different angular positions of the swing photovoltaic module rotation sequence. In the figures, photovoltaic panel 1rotates in a clockwise direction. FIG. 3A shows the initial angular position of vertical photovoltaic module 102. Initially, the photovoltaic module 102 plane is vertical, a frontside 204 ( side 204 has the maximal electrical efficiency) faces the East direction, and backside 206 faces the West direction. Just after the sunrise, the vertically mounted bifacial photovoltaic module 102 rotates clockwise from the vertical position 3A towards a tilt angle 107 (or T) and discontinues the rotation of the bifacial photovoltaic module 102 at a predetermined tilt angle T. Angle T is in the range of 15 to 75 degrees. Defining an optimal T angle depends of the ground albedo of the installation site: the higher the ground albedo, the lower can be the tilt angle T. [0035] The clockwise rotation of bifacial photovoltaic module 102 towards tilt angle T (FIG. 3B) could be done in several ways: • a fast rotation from a position of FIG. 3A the position of FIG. 3 B; • a step-and-repeat incremental rotation with some delay at intermediate angles; • or by sun-tracking when the photovoltaic module plane 106 is kept perpendicular to the sun azimuth during rotation, e.g., by the input of a photosensor (not shown) Docket 231-002-IL - 8 - installed on the photovoltaic module and electrically connected to a module rotation controller. [0036] Just before noontime, the photovoltaic module 102 rotates at a maximal speed ω, through the horizontal position, to the tilt angle 110, which is equal (180° - T), which is a complementary angle to the tilt angle T (107). The beginning of vertical photovoltaic panel 102 movements from the position in FIG. 3B to the position in FIG. 3C and the movement time could be calculated according to the values of ω, T, and noontime (NT). For example, if NT is 12:00 o'clock, ω= 0.2 deg/sec, and T=30° so the rotation from the position in FIG. 3B to the position of FIG. 3C could take time 120°/0.2=600 sec or (ten) min, and the movement should start at 11:55: by this way the photovoltaic module plane 106 will be in horizontal position (FIG. 2B) exactly at the noontime 12:00. [0037] The photovoltaic module 102 remains at the position illustrated in FIG. 3C until a certain afternoon time, before sunset time SST. This "certain afternoon time" may be defined as the time when the direct sunlight direction complies with the normal to the photovoltaic module plane or, in other words, when the angle between the sun azimuth and the ground is equal to angle T. [0038] The movement from the position of FIG. 3B to the position of FIG. 3C could be performed in the same manner as the movement from the position of FIG. 3A to the position of FIG. 3B. The bifacial photovoltaic module 102 is now in another vertical position corresponding to a rotation or tilt of 180°. In this position, the front side 2faces the West direction. Following the completion of rotation of the photovoltaic module 102 in the position of FIG.3D, photovoltaic module 102 could be rotated counterclockwise as illustrated by arrow 310 back to the initial position (FIG. 3A) at any time after the sunset. The counterclockwise rotation back to the initial position could be done at the maximal rotation speed or by the described above step-and-repeat movements of the photovoltaic panel. Following the completion of the movement to the position of FIG. 3A, the photovoltaic module 102 becomes stationary during the night until the next sunrise. The photovoltaic panel daily swing movement cycle could be repeated at the following day's sunrise.

Docket 231-002-IL - 9 - [0039] One of the advantages of the Swing photovoltaic panels is an easy reduction of the wind load impact. Maintaining proper operation of a vertical photovoltaic panel mount under a high wind load is challenging. The wind load is especially high when the wind is substantially directed in parallel to the Earth's surface in the East-West direction or West-East direction. One of the advantages of the Swing photovoltaic panels is an easy reduction of the wind load impact. Rotating the photovoltaic module to a horizontal position (at the angle of 90° to the vertical) reduces the photovoltaic panel cross-section subject to the wind load. When a wind speed is greater than a predefined limit, the photovoltaic panel could rotate into a position illustrated in FIG. 4C or horizontal position. The photovoltaic module could be maintained in the horizontal position until the wind speed becomes lower than the predefined limit. When the wind speed becomes lower than the predefined limit, the photovoltaic module could continue the rotation according to a sequence described above. The described solution supports installation of constructions, which hold the photovoltaic modules, with much lower stiffness as compared to static vertical photovoltaic module mount, providing a significant cost saving. [0040] FIGS. 4A through 4D illustrate different angular positions of vane alarm controlled swing photovoltaic module rotation sequence in a high wind load. [0041] The photovoltaic panel installation 400 includes the Swing photovoltaic panel mounts illustrated in FIGS. 1 and 2 and a wind vane 402. Wind vane 402 is in electrical communication with a controller 404, controlling motor 406, which rotates the photovoltaic module around pivot 103. For illustration purposes only, let's consider that before noon (FIG. 3B) the wind vane 402 provides an alarm – an electrical signal to controller 404 indicating that the wind speed exceeds the predefined limit value that could jeopardize the Swing photovoltaic module mount construction. In such a case, controller 404 directs to motor 406, which rotates the photovoltaic module around pivot 103 to position the photovoltaic module into horizontal plane 210 (FIG. 42B). Such photovoltaic module position supports low resistance to the wind, the photovoltaic module remains in a horizontal position until the wind vane 402 provides to controller 404 a signal indicating that the wind speed is lower than the predefined limit value so the Docket 231-002-IL - 10 - photovoltaic module 102 can resume the regular Swing sequence. For example, if such a signal comes, at an early afternoon the photovoltaic module 102 rotates to the next tilt angle shown in FIG. 4C. [0042] FIG. 5 shows AC power of a photovoltaic system in two configurations: Swing photovoltaic modules with a tilt angle of 30° and static vertical photovoltaic modules. The test was conducted in Karmei Yosef location, Israel on February 18,.2022. Both test systems included six photovoltaic panels of 455W, each oriented in the South-North direction. The static vertical photovoltaic system includes two rows (top and bottom) of panels, and each row included three photovoltaic modules of about 2m x 1m in size with a long side parallel to the ground. The Swing photovoltaic system included six identical photovoltaic modules mounted in one row, with the smaller side frame parallel to the ground. These modules are rotated around the pivot located in the middle of the photovoltaic module height (similar to FIG. 1). Curve 502 relates to the Swing photovoltaic system , and curve 504 relates to the static vertical photovoltaic system . During the whole day of February 2, 2022 and despite the relatively small tilt angle of 30°, the Swing photovoltaic system produced 37% more of AC power than the static vertical photovoltaic system produced. Such tilt angle causes relatively small shadow both in size and in sunlight attenuation (due to the significant contribution of the diffused light). Remarkable power gain of Swing photovoltaic panel compared to vertical photovoltaic panel facilitates combining advantages of vertical modules and sun tracking photovoltaic modules systems for dual-use applications, especially for agriculture of field crops. [0043] The Swing photovoltaic modules mounting is handy for crops requiring maximal sun radiation since it creates minimal shadowing compared to a regular, e. g. single-axis, sun tracking. However, there are some periods in agriculture, i.e., within and between seasons, without field crop presence. During such periods it is worthwhile to replace the Swing photovoltaic panel rotation sequence with a regular sun tracking in a full angular range from 0 to 180° during the daytime. Such sun-tracking could further enhance the annual electrical power generation by the photoelectric modules. A combination of Swing Docket 231-002-IL - 11 - photovoltaic modules and full tracking is possible by simply changing the controller program, which operates the photovoltaic panel rotating mechanisms. [0044] While the apparatus and method have been described with respect to a limited number of examples, these should not be construed as limitations on the scope of the apparatus and method. Other possible variations, modifications, and applications are also within the scope of the disclosure. Accordingly, the scope of the disclosure should not be limited by what has been described, but by the appended claims and their legal equivalents.

Claims (13)

IL 291309 Response to P.Q. 27 Clean Claims - 12 - A Clean version of the amended claims The present claims will replace all earlier versions of the claims.

1. A method of angular locating of a bifacial photovoltaic module for agricultural use throughout the daytime, comprising: providing a vertically mounted bifacial photovoltaic module with a pivot parallel to the South-North direction; at sunrise, rotating the vertically mounted bifacial photovoltaic module clockwise from the vertical position towards a tilt angle of 90° and discontinue rotating the bifacial photovoltaic module at a predetermined tilt angle T, wherein the predetermined tilt angle T is an angle of less than 90°; at noontime, continue rotating the bifacial photovoltaic module towards an angle of 180° and discontinue rotating the bifacial photovoltaic module at a tilt angle of less than 180°; in the afternoon time, rotating the bifacial photovoltaic module towards the tilt angle of 180° and discontinue rotating the bifacial photovoltaic module at the vertical back position at the tilt angle of less than 180°, and wherein the rotation of the photovoltaic module from the tilt angle T to the tilt angle of less than 180° takes less than ten minutes; and wherein a setting of the tilt angle T accounts for the installation site albedo.

2. The method of claim 1, wherein selecting the tilt angle T of the photovoltaic module from a range of angles of 15° to 75°.

3. The method of claim 1, wherein setting the tilt angle T of the bifacial photovoltaic module, including minimized ground shading at noon hours.

4. The method of claim 1 further comprising orienting an initial vertical position of the front side of the bifacial photovoltaic module to the East. IL 291309 Response to P.Q. 27 Clean Claims - 13 -

5. The method of claim 1, wherein the rotation of the bifacial photovoltaic module from the tilt angle T to the tilt angle of less than 180° is done with a rotation speed of at least 0.2 deg/sec.

6. The method of claim 1, wherein rotating the bifacial photovoltaic module from an initial vertical position to the tilt angle T is done by keeping the bifacial photovoltaic module plane perpendicular to the sun azimuth.

7. The method of claim 1, wherein the afternoon time is when the direct sunlight ray is perpendicular to the front surface of the photovoltaic module and wherein the afternoon time is defined as the time when the direct sunlight direction complies with the normal to the photovoltaic module plane.

8. The method of claim 1, wherein rotating the bifacial photovoltaic module from the tilt angle of less than 180° to an initial vertical position, is done at maximal rotation speed or by step-and-repeat movement.

9. The method of claim 1 further comprising: rotating the photovoltaic module to a horizontal position at an angle of less than 90° when a wind speed is greater than a predefined limit; holding the photovoltaic module in the horizontal position until the wind speed becomes lower than the predefined limit; and continuing rotating the photovoltaic module according to a photovoltaic module rotation sequence described in claim 1.

10. A method of angular locating of a bifacial photovoltaic module throughout the daytime, comprising: installing in an agricultural area at least one vertically mounted bifacial photovoltaic module with a pivot parallel to the South-North direction; during the seasons of growing crops, angularly positioning the vertically mounted photovoltaic module according to claim 1;

11.IL 291309 Response to P.Q. 27 Clean Claims - 14 - during the seasons when crops are not present in the agricultural area, operating a regular sun-tracking arrangement throughout the full angular range of 0 to less than 180°; and wherein the angularly positioning of the vertically mounted photovoltaic module during the seasons of growing crops accounts for the installation site ground albedo. 11. A method of maintaining a proper operation of a vertically mounted bifacial photovoltaic panel under a high wind load by rotation of the vertically mounted bifacial photovoltaic panel: at sunrise rotating clockwise and locating the vertically mounted bifacial photovoltaic module at a tilt angle of less than 90° and discontinue rotating the bifacial photovoltaic module at a predetermined tilt angle T, of less than 90°; at noontime, continue rotating the bifacial photovoltaic module (102) and locating the bifacial photovoltaic module at a tilt angle of less than 180°; at the afternoon time, rotating the bifacial photovoltaic module towards the tilt angle of 180° and locating the bifacial photovoltaic module at the vertical back position at the tilt angle of less than 180°, and after the sunset, returning the bifacial photovoltaic module to initial vertical position; and wherein the tilt angles for locating the vertically mounted bifacial photovoltaic module account for the installation site ground albedo.

12. A method of angular locating of a bifacial photovoltaic module throughout the daytime, comprising: installing in an agricultural area at least one vertically mounted bifacial photovoltaic module with a pivot parallel to the South-North direction; in the daylight, tilting around the pivot of the at least one vertically mounted bifacial photovoltaic module on a tilt angle T and wherein an optimal tilt angle depends on the installation site ground albedo. IL 291309 Response to P.Q. 27 Clean Claims - 15 -

13. The method of claim 12 further comprising at any time after the sunset rotating the photovoltaic module back to its initial position, wherein the rotation back to its initial position is performed by one of a group of speeds consisting of a maximal rotation speed or by step-and-repeat movements of the photovoltaic panel. For the Applicant /Rafi Bronstein/ L.N. 2