WO2022203514A1

WO2022203514A1 - Bifacial solar panel, solar module and method for installation

Info

Publication number: WO2022203514A1
Application number: PCT/NO2022/050068
Authority: WO
Inventors: Trygve MONGSTAD
Original assignee: Over Easy Solar As
Priority date: 2021-03-24
Filing date: 2022-03-18
Publication date: 2022-09-29
Also published as: NO20210379A1; NO20211187A1

Abstract

There is disclosed a bifacial solar panel including a plurality of photovoltaic elements, wherein the photovoltaic elements are arranged in a row with a total height of 30 centimetres or less. There is also disclosed a solar module including a plurality of such solar panels as well as a method for installing the solar module.

Description

BIFACIAL SOLAR PANEL, SOLAR MODULE AND METHOD FOR INSTALLATION

The present invention relates to a bifacial solar panel. More specifically the invention re lates to bifacial solar panel including a plurality of photovoltaic elements. The invention also relates to a solar module including several such solar panels as well as to a method for installing the solar module.

Solar panels for roof top installations have usually been installed substantially in the plane of the roof or, for flat rooftops, obliquely in a scaffold for optimized power generation and self-cleaning by rainfall. The solar panels are adapted to receive incoming light on one side and to convert the solar irradiance to power, often via a DC-AC inverter. A drawback with horizontal or partially horizontal installations is that the solar panels are prone to shading effects due to falling dust, sand, leaves, snow etc. Shading, even if only of one panel, can drastically reduce the output of an entire solar module system. Another draw back of solar panels when used in conventional rooftop modules, is that they are exposed to significant wind forces that need to be taken into account when dimensioning and in stalling the modules and mounting systems. Even further, and partially because of the need to take wind forces into account, installation of such solar modules on rooftops has been complicated and time-consuming. At locations where snow loads have to be taken into consideration, the systems must also be designed to withstand these loads, often resulting in even more complex mounting and use of additional material in the mounting systems. At locations with much sand and dust, typically dry locations, solar panels need to be frequently cleaned to maintain power production at an acceptable level.

Lately, bifacial solar panels have gained larger market shares due to lower production cost with modern solar cell technology. It has been suggested to take advantage of the bifaciality of solar panels by placing them in flat rooftop installations, where the oblique angle of the panel permits light partly also to hit the solar panel from the back side. Some solutions have also been suggested where the solar panels have been installed vertically in a scaffolding, but with a vertical gap between the rooftop and the solar panel to so that the panels can be used in combination with vegetation on the rooftop. The suggested so lutions for vertical installation with panels above vegetation on the rooftop have the draw back that they are complicated to mount, as the structure is partly placed below the vege tation. The suggested solutions also have the drawback that their high mounting height above the surface disturbs the architecture of the building and make the solutions less viable in cities where there are strict height limitations on buildings.

Solar panels for rooftop installations usually come in the dimensions of approximately 1 m x 1 .7 m. Vertical installations of regular bifacial solar panels have been suggested, where the panels have been installed in the “landscape” mode, with a height of the instal lation of at least one metre including the scaffolding. Increasing the height of a solar panel increases the area that is adapted to receive incoming light, and hence the total power generation of the panel. On the other hand, increasing the height also increases the shad ing effect on the “next” module and increases horizontal wind drag on the module. Optimized panel heights have usually been considered to be in the order of 1 meter as e.g. disclosed in various scientific articles, such as in

DOI: 10.1016/j.apenergy.2017.08.042 and 001:10.1016/j.apenergy.2017.12.041 .

Regular solar panels include several rows of solar cells, normally 6 rows in the shortest dimension of the panel. When vertically mounted such panels may suffer significantly from internal mismatch losses as the cells at different height in the module are exposed to dif ferent direct light component and different diffuse light component.

Installation work tasks for installing solar modules are today performed by workers doing manual operations such as mounting system placement, lifting of parts, assembly of mounting system, lifting and placement of solar panels, and fixation of the solar panels to the mounting structure. The nature of these tasks in today’s solution makes them hard to automate, as there are many different operations requiring different skills and many differ ent coarse and fine mechanical tasks. Also, the physical dimensions of today’s solar mod ules make this difficult, especially concerning automation involving aerial vehicles, be cause of the bulky nature and large planar surface that may create disruption of air flow used to maneuver the aerial vehicle. The large, planar surface of today’s modules also make them prone to high wind loads under lifting operations, making flight control and exact placement, even at low wind speeds, a challenging task.

The invention has for its object to remedy or to reduce at least one of the drawbacks of the prior art, or at least provide a useful alternative to prior art.

The object is achieved through features, which are specified in the description below and in the claims that follow.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect, the invention relates to a bifacial solar panel including a plurality of pho tovoltaic elements, wherein the photovoltaic elements are arranged in a row with a total height of 30 centimetres or less.

In one embodiment, the total height of the row of photovoltaic elements may be 25 centi metres or less.

The very low height of the photovoltaic elements, and hence the solar panel, may in many aspects be regarded as counter-intuitive, as the total surface area per solar panel is re duced and therefore requires more solar panels to obtain a target output power.

The panel as such will usually be around 2-5 centimetres higher than that of the photovol taic elements as glass and a potential surrounding frame adds in the order of 1-2 centime tres height on each side. In addition to the glass laminating the photovoltaic elements in place, the panel may or may not be provided with a surrounding frame. The frame, if pre sent, may be made from aluminium or another light-weight metal, and may protect and add mechanical stability to the panels.

In one embodiment, the solar cells may be laminated between two glasses, each with a thickness in the range of 1 .5-5 mm. The glasses themselves may give the necessary structural strength and/or it may be supported by a strengthening frame. The edge of the panel may be protected by a soft polymer and/or a stiff frame as to avoid damages during handling, mounting and operation.

The bifacial solar panels are particularly suited for placement on a substantially flat sur face. By “substantially” flat is meant that the surface may have a certain and natural une venness or slope. E.g. a “flat” rooftop will also be made with a certain slope, usually in the order of 6° or less, to allow rain and melted snow to run off. The solar panels may also be intended to be placed on the ground, such as on a pergola over parking lots etc., in agri- voltaics, i.e. over agricultural areas, or even as integrated in facades. Bifacial solar panels will usually be mounted substantially vertically to optimise solar irradiance on both sides of the panel. However, variations up to 10°, and in certain application even up to 25°, from vertical installation may be used while still taking advantage the bifaciality of the panels.

In one embodiment the photovoltaic elements may be bifacial silicon solar cells. As an alternative, the photovoltaic elements may be single-sided solar cells arranged back-to- back to obtain a bifacial panel.

In one embodiment, the height of each photovoltaic element may be defined by that of a single silicon wafer from which each of the bifacial silicon solar cells is made.

The cells of the solar panel may be of high bifaciality, preferably of the heterojunction technology (HJT) cell type or “Topcon”, or any other high-efficiency solar cell technology with high bifaciality, i.e. the ratio of the nominal efficiency at the rear side, with respect to the nominal efficiency of the front side.

In one embodiment, the length of the solar panel may be in the order of 1 to 2 metres, preferably around 1.25 metres. In certain embodiments, depending on the size of each photovoltaic element, this may include 6-12 solar cells / photovoltaic elements of “stand ard” wafer size arranged in a row. As will be understood by a person skilled in the art, wa fers for silicon solar cells are usually provided with a size of 150-210 mm in one dimension and 150-210 mm or cut in two or more equally sized pieces in the other dimension.

In a second aspect, the invention relates to a solar module including a plurality of bifacial solar panels according to the first aspect of the invention, the solar module comprising first and second horizontal profile members arranged in parallel and wherein the plurality of bifacial solar panels are arranged substantially vertically with a horizontal distance there between in a length direction of the horizontal profile members and wherein the solar pan els are connected to the first and second horizontal profile members.

By “horizontal” and “vertical” should be understood that the profile members and the solar panels are substantially horizonal and vertical, respectively, when placed on an even and perfectly horizontal surface. In use, the surface on which the solar module is installed may be uneven and/or sloping, implying the length direction of the “horizontal” profile members may not be fully horizontal and that the solar panels, connected to the profile members, may not be fully vertically arranged.

In one embodiment, the solar panels may be connected to inner side portions of the hori zontal profile members. This may be very useful for enabling stacking such solar modules on top of each other for easy storage and transport. The solar panels may be connected to the inner side portions through brackets, in the form of profiles or clamps with screws, glued in place or pressed into a profile or clamp with friction rubber, or any combination of these.

The invention also relates to a stack including a plurality of solar modules according to the second aspect of the invention. The configuration where the solar panels are connected to the inner side of the horizontal profile members of the solar modules allow for compact storage and transport while the modules are arranged in the stack.

The stack may be supported under transport by a pallet or specialised support that ena bles easy handling and lifting. The top of the stack may also be protected by a specialised support that allows another stack to be placed on top of the first under transport.

In one embodiment, each solar panel may be provided with one or more support members adapted to support the weight of the solar panel on a rooftop or another surface. Advanta geously each solar panel may rest with its own weight on the roof top, or other surface, via the support members. The support members may be a pair of legs and/or brazing mem bers provided at side portions of the solar module and being adapted to support each so lar panel on the roof top. Even though the horizontal profile members connect the solar panels into a module, it may be an advantage that each panel is separately supported on the rooftop. This may reduce the load on the panels, dampen vibrations from wind and improve run-off of leaves, dust, sand, snow etc. under the modules. As such, in a position of use, the horizontal profile members, may be connected to the solar panels at a vertical distance above the rooftop.

The support members will also allow the panels and the horizontal profile members to be suspended at a certain distance above the rooftop, the distance being in the range of 5-50 cm. This may be beneficial to allow for dirt and leaves to flow away from the installation. The distance may also permit combination with roofs covered in vegetation and may give increased energy production yield in the winter as snow will accumulate below the panels and not obstruct light hitting the modules.

The support members may be adapted to different kind of surfaces as to optimize for best friction and to reduce wear on the surface on which the module is mounted. As examples, for bitumen surfaces a rubber granulate mat may be used, and for green roofs a struc tured profile or sole for adhesion to the vegetation and underlying mats may be adopted. In one embodiment the horizontal profiles members may also be guides for cables and wires connecting the solar panels electrically to each other and/or to an external power output. This means that the profile may have the double-function of mechanically connect ing and positioning the solar panels relative to each other, as well as to be a guide and protection for the necessary cables and wires.

In one embodiment, the support members of the module may be of adjustable length to better adapt to uneven and/sloping surfaces. In one embodiment an inner or outer portion of the support member may be telescopically arranged relative to the remainder of the support member, whereby its length may be adjusted relative to a neighbouring support member. It may be possible to lock the telescopic portion for support member at different lengths whereby the support member may also be adapted to support the weight of the solar module when extended or shortened.

In one embodiment, the horizontal distance between each bifacial solar panel in the length direction of the profile members may in the order of 20-60 centimetres, preferably 30-50 centimetres. A person skilled in the art will understand that the distance may be an optimi zation based on the height and orientation of the panels and the solar conditions at the location on which they are installed.

In one embodiment the solar module may include 2-6 bifacial solar panels, preferably 4 bifacial solar panels. The low height, and thereby low weight, of the solar panels, enables the combination of several solar panels into a readily assembled module, where the whole module may be installed as one unit, including by means of an unmanned surface or aeri al vehicle as will be discussed briefly below.

The invention also relates to a string including a plurality of solar modules according to the second aspect of the invention. The string includes plurality of solar modules connected in series via an external connector to provide an output voltage that may typically be in the range of 100 V to 1500 V, depending on the maximum power point tracker of the inverter, as will understood by a person skilled in the art.

In one embodiment, solar modules in an installation including one or more strings of solar modules may also be mechanically connected to each other (otherwise than through the electrical connection), which may offer better resistance against wind loads. The mechan ical connection may be enabled by connecting the horizontal profile member and/or sup port member and/or a solar panel in one solar module to that of an adjacent solar module. The mechanical connection may be done by connecting the parts directly to each other or via a bracket or similar. One or more modules may additionally, or as an alternative, be mechanically connected or ballasted to the surface, such as to the roof, on which it is placed.

Junction boxes, including power electronics and bypass diodes, may be connected at one or both sides of the solar panels. The junction boxes are preferably provided at the lower parts of the panels (in a position of use). The junction boxes will preferably be placed on the edge/frame of the panels, allowing for the panels to be connected without preparing holes in the glass of the modules. In one embodiment, each panel could be provided with two junctions boxes; one for each of the positive and negative sides. The current may be returned via a neighboring panel. The current may also be returned through an external conductor to the other junction box. In an embodiment where each panel is provided with a single junction box, the current from the row of cells/photovoltaic elements in each panel may be led back using a return ribbon laminated into the lower part of the panel. In anoth er alternative, the current may be returned by splitting each photovoltaic element in two equal parts and letting either the lower or the upper part be the return string.

The invention also relates to stack including a plurality of solar modules according to the second aspect of the invention. As explained herein, certain configurations of the solar modules according to the second aspect of the invention allow for compact storage and transport while the modules are arranged in a stack.

The stack may be supported under transport by a pallet or specialised support that ena bles easy handling and lifting. The top of the stack may also be protected by a specialised support that allows another stack to be placed on top of the first under transport. The spe cialised top support may rest on the horizontal profile member of the topmost module in the stack and protect the topmost solar panels from mechanical impacts. When another stack or any other weight is placed on top of the specialised top support, the support may ensure that the weight is well supported without causing damage to the panels or modules in the lower stack.

In order to increase energy yield where the mounting surface has low reflection or albedo, the module may include reflectors, substantially vertically mounted, with highly reflective materials or coatings midway between the panels along the horizontal profile. The height of the reflectors will typically be half of the height of the solar panels. In a third aspect, the invention relates to a method for installing a solar module according to the second aspect of the invention, the method including the steps of:

- lifting the solar module as a whole; - placing the solar module on surface, such as on a rooftop; and

- connecting the solar module to a solar power inverter.

The method may, prior to the step of lifting the solar module as a whole, include the step of lifting a stack of such solar modules a whole.

The method may also include the additional step of connecting the solar module electrical- ly to another solar module in series to define a string of solar modules.

In one embodiment, the method may be fully or partially implemented by means of an unmanned surface or aerial vehicle. To further reduce cost of installation of rooftop solar plants in the future, it may be beneficial to automate work tasks. The invention in the sec ond aspect entails a module which includes both the mounting structure and the solar panels in the same device. Placement and installation of the panels will be more efficient than for today’s solutions. It also creates an opportunity for automating the installation work tasks, as fewer and more similar operations may be needed, mainly, lifting the stack and modules and placing them in the right location. The automation may be performed by a worker, a surface vehicle, or an aerial vehicle. Concerning lifting and maneuvering tasks performed by aerial vehicle, the invention in the second aspect gives an advantage com pared to today’s solar modules, in that the modules with the low panels have a very low weight, air flow is less disrupted and the wind loads during lifting operations are lower.

In the following are described examples of preferred embodiments illustrated in the ac companying drawings, wherein: Fig. 1 shows a solar panel according to the invention;

Fig. 2 shows first embodiment of a solar module including a plurality of solar pan- els according to invention;

Fig. 3 shows a second embodiment of solar module according to the invention;

Fig. 4 shows a third embodiment of a solar module according to the invention;

Fig. 5 shows an enlarged detail of the solar module from Fig. 3; Fig. 6 shows a stack of solar modules according to the invention;

Fig. 7 shows a string of solar modules according to the invention; and

Fig. 8 shows a fourth embodiment of a solar module according to the invention.

In the following reference numeral 1 will be used to denote a solar panel according to the first aspect of the invention, while reference numeral 10 will be used to denote a solar module according to the second aspect of the invention. Reference numeral 100 will be used to denote a stack of such modules, while reference numeral 1000 is used to denote a string of modules. Identical reference numerals refer to identical or similar features in the drawings. The drawings are shown schematically and simplified, and various features therein are not necessarily drawn to scale.

Fig. 1 shows a solar panel 1 according to the first aspect of the invention. In the shown embodiment, the panel includes seven bifacial silicon solar cells 3 arranged in a row of which only one of the sides is visible in the perspective view. The solar cells 3 are electri cally connected in series, laminated by glass plates 5 and surrounded by a thin frame 7. Internal and external electrical connections are not shown in the figure. The shown solar panel 1 has a length L of about 125 cm, while the height FI is approximately 19 cm. The solar cells are squares with rounded corners and a length of approximately 17 cm, imply ing that lamination and frame adds about 1 cm height on each side and 3 cm on each side in the length direction. In Fig. 2 a first embodiment of a solar module 10 according to the second aspect of the invention is shown. The shown module includes four solar panels 1 according to the first aspect of the invention. The panels are connected to a horizontal profile member 9 on each side, and they are arranged substantially vertically equidistantly along the horizontal profile members 9. In the shown embodiment, the length L2 of each horizontal profile member is 1 .01 m, whereby the distance D between the solar panels along the horizontal profile members is approximately 33 cm. The panels 1 are connected to inner side por tions 11 of the horizontal profile members 9. In the shown embodiment, the horizontal profile members 9 are resting on a surface 15 on which the solar module 1 is placed.

Fig. 3 shows a second embodiment of solar module 10 according to the invention. Each solar panel 1 is provided with support members, here in the form of a pair of legs 13, sup porting the weight of the solar module 10 on the surface 15, while the horizonal profile members 9 are positioned a vertical distance above the surface 15. In this embodiment, the role of the profile members 9 is to connect the solar panels 1 mechanically together and to keep them in a correct position and orientation relative to each other, while at the same time functioning as a cable tray for not shown electrical connections between the solar panels and/or between adjacent solar modules 10. Fig. 4 shows a third embodiment of a solar module 10 according to the invention. The solar module resembles the one from the second embodiment as shown in Fig. 3 but with the difference that each horizontal profile member 9 is provided with a hinge 17, substan tially in the middle in the length direction, allowing a first portion 19 of the horizontal profile member 9 to rotate relative to a second portion 21 of the horizontal profile member 9 around an axis A substantially perpendicular to the length direction of the horizontal profile member 9. This allows the whole solar module 10 to rotate so that the two solar panels 1 connected to the first portion 19 of the horizontal profile members 9 may rotate relative to the two solar panels 1 that are connected to the second portion 21 of the horizontal profile members 9. This may be particularly useful if the solar module 10 is to be placed on a sloped or uneven surface, such as over a ridge on a substantially flat rooftop. The hori zontal profile members 9 may be provided with additional, not shown hinges for increased flexibility.

Fig. 5 shows an enlarged detail of the embodiment from Fig. 3. It can be seen how the solar panels 1 are connected to the inner side portion 11 of the horizontal profile member 9, while the solar panels 1 as such are supported by the legs 13. The horizontal profile member 9 is, in the shown embodiment, welded or otherwise connected to a reinforced brazing portion 23 in a lower corner 25 of each of the solar panels 1 and extending about 1/3 of the height of the solar panel 1. The reinforced brazing portion 23 also forms the connection to the legs 13, whereby the laminated glass and the solar cells 3 as such are protected. The configuration where the horizontal profile members 9 are arranged on the sides of the solar panels 1 allow the solar modules 10 to be arranged in a stack 100, as shown in Fig. 6, which significantly simplifies storage and transport of the solar modules 10.

Fig. 7 shows a plurality of solar modules 10. The modules are electrically connected to define strings 1000 of solar modules 10 as described herein. Internal and external electri cal connections are not shown in the figure. The modules may also be mechanically con nected to each other to make the installation more robust against wind lift forces.

Fig. 8 shows a fourth embodiment of a solar module 10 according to the invention. In the shown embodiment, the solar module 10 is provided with reflectors 30 positioned substan tially midway between the solar panels 1 along the horizontal profile members 9. Similarly to the solar panels 1 , the solar reflectors 30 are connected to one horizontal profile mem ber 9 on each side on the inside of the horizontal profile members 9 substantially vertically and equidistantly along the horizontal profile members 9. In the shown embodiment, the reflectors 30 have the same length L as the solar panels, while their height H’ is substan tially half of the height H of the solar panels 1. In the shown embodiment, both the solar panels 1 and the solar reflectors 30 are connected to the horizontal profile members 30 by means of (upside-down) T-shaped brackets 31. The solar panels 1 are additionally sup- ported by legs 13 on the ground / roof top as explained above, implying that the reflectors, in the shown embodiment are only support by the horizonal profile members 9. In an al ternative embodiment, also the solar reflectors 30 may be supported directly on the ground.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodi ments without departing from the scope of the appended claims. In the claims, any refer ence signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

C l a i m s

1 . Bifacial solar panel including a plurality of photovoltaic elements c h a r a c t e r i s e d i n that the photovoltaic elements are arranged in a row with a total height of 30 centimetres or less.

2. Bifacial solar panel according to claim 1 , wherein the total height of the row of photovoltaic elements is 25 centimetres or less.

3. Bifacial solar panel according to claim 1 or 2, wherein the photovoltaic elements are bifacial silicon solar cells.

4. Bifacial solar panel according to claim 3, wherein the height of each photovoltaic element is defined by that of a single silicon wafer from which each of the bifacial silicon solar cells is made.

5. Bifacial solar panel according to any one of the preceding claims, wherein the length of the solar panel is in the order of 1 to 2 metres, preferably around 1 .25 metres.

6. Solar module including a plurality of bifacial solar panels according to any one of the preceding claims, the solar module comprising first and second horizontal profile members arranged in parallel and wherein the plurality of bifacial solar panels are arranged substantially vertically with a horizontal distance there between in a length direction of the horizontal profile members and wherein the solar panels are connected to the first and second horizontal profile members.

7. Solar module according to claim 6, wherein each solar panel is provided with one or more support members adapted to support the weight of the solar panel.

8. Solar module according to claim 7, wherein the length of one or more support members is adjustable.

9. Solar module according to any one of the claims 6-8, wherein the solar panels are connected to inner side portions of the horizontal profile members.

10. Solar module according to any one of the claims 6-9, wherein the horizontal dis tance between each bifacial solar panel in the length direction of the profile members is in the order of 20-60 centimetres, preferably 30-50 centimetres.

11. Solar module according to any one of the claims 6-10, wherein the solar module includes 2-6 bifacial solar panels, preferably 4 bifacial solar panels.

12. Solar module according to any one of the claims 6-11 , wherein the horizontal pro files members are also guides for cables and wires connecting the solar panels to each other and/or to an external power output.

13. Solar module according to any one of the claims 6-12, wherein the horizontal pro file members, in a position of use, are connected to the solar panels at a vertical distance above the surface on which the solar module is placed.

14. Solar module according to any one of the preceding claims, wherein the solar module includes a substantially vertical reflector connected to the first and sec ond profile members midway between solar panels.

15. String including a plurality of solar modules according to any one of the claims 6- 14.

16. String according to claim 15, wherein two or more solar modules are mechanical ly connected to each other.

17. Stack including a plurality of solar modules according to any one of the claims 6- 14.

18. Stack according to claim 16, wherein the stack is provided with a bottom and/or top support to be used during transport.

19. Method for installing a solar module according to any one of the claims preceding claims on surface, the method including the steps of:

- lifting the solar module as a whole;

- placing the solar module on the surface, such as a rooftop; and

- connecting the solar modules to a solar power inverter.

20. Method according to claim 19, where method, prior to the step of lifting the solar module as a whole, includes the step of lifting a stack of such modules as a whole.