NON-FLAT SOLAR ROOF TILES

US 2019 245 478 A1

One embodiment can provide a non-flat photovoltaic roof tile. The non-flat photovoltaic roof tile can include a transparent front cover, a back cover, and a plurality of Si-based photovoltaic structures. The transparent front cover can include a first side and a second side, with the first side comprising at least one non-flat portion and the second side comprising a plurality of flat facets. The flat facets are arranged to follow the contour of the at least one non-flat portion. A respective Si-based photovoltaic structure is positioned between a flat facet of the transparent front cover and the back cover.

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Claims

1. A non-flat photovoltaic roof tile, comprising:
a transparent front cover having a first surface and a second surface, wherein the first surface comprises at least one portion that is convexly curved, wherein the second surface comprises a plurality of flat facets, and wherein the flat facets are arranged to follow the contour of the at least one convexly curved portion of the first surface;
a back cover; and
a plurality of Si-based photovoltaic structures, wherein a respective Si-based photovoltaic structure is positioned between a flat facet of the transparent front cover and the back cover.

Show 12 dependent claims

14-20. (canceled)

Description

BACKGROUND
Field

This disclosure is generally related to the design of photovoltaic (or PV) modules. More specifically, this disclosure is related to the design and manufacture of curved photovoltaic roof tiles.

Advances in photovoltaic technology have helped solar energy gain mass appeal among those wishing to reduce their carbon footprint and decrease their monthly energy costs. In residential and commercial solar installations, a building's roof can be covered by photovoltaic (PV) modules, also called PV or solar panels, that can include a two-dimensional array (e.g., 6×12) of solar cells. However, conventional solar panels can leave a portion of the roof uncovered, and can lack aesthetic appeal. A PV roof tile (or solar roof tile) can be a particular type of PV module offering weather protection for the home and a pleasing aesthetic appearance, while also functioning as a PV module to convert solar energy to electricity. A PV roof tile can be shaped like a conventional roof tile and can include one or more solar cells encapsulated between a front cover and a back cover, but typically enclose fewer solar cells than a conventional solar panel.

SUMMARY

One embodiment described herein provides a non-flat photovoltaic roof tile. The non-flat photovoltaic roof tile can include a transparent front cover, a back cover, and a plurality of Si-based photovoltaic structures. The transparent front cover can include a first side and a second side, with the first side comprising at least one non-flat portion and the second side comprising a plurality of flat facets. The flat facets are arranged to follow the contour of the at least one non-flat portion. A respective Si-based photovoltaic structure is positioned between a flat facet of the transparent front cover and the back cover.

In a variation on this embodiment, the transparent front cover can include glass.

In a variation on this embodiment, the back cover can include a photovoltaic backsheet or a rigid back cover comprising a second set of flat facets.

In a variation on this embodiment, adjacent photovoltaic structures positioned on a same flat facet are electrically coupled to each other in series.

In a further variation, the adjacent photovoltaic structures positioned on the same flat facet are coupled in such a way that a first edge busbar positioned on a first photovoltaic structure overlaps a second edge busbar positioned on a second photovoltaic structure.

In a variation on this embodiment, adjacent photovoltaic structures positioned on different flat facets are electrically coupled to each other in parallel.

In a variation on this embodiment, a respective photovoltaic structure can be obtained by dividing a 6-inch by 6-inch square solar cell into three strips.

In a variation on this embodiment, the transparent front cover has a shape similar to that of a conventional roof tile, and the at least one non-flat portion can include a partial-cylindrical surface.

In a variation on this embodiment, the non-flat photovoltaic roof tile can include at least a pair of external electrical connectors for electrical coupling with adjacent roof tiles.

In a variation on this embodiment, the adjacent roof tiles are arranged side by side along a latitudinal axis of the non-flat portion, and the external electrical connectors are configured to couple the adjacent roof tiles in parallel.

In a variation on this embodiment, the adjacent roof tiles are arranged up and down along a longitudinal axis of the non-flat portion, and the external electrical connectors are configured to couple the adjacent roof tiles in series.

In a variation on this embodiment, the flat facets are configured in such a way that they are out of sight when viewed from a side angle.

In a further variation, a respective flat facet can include a flat bottom surface of a pocket formed on the second side of the non-flat photovoltaic roof tile.

A solar cell or cell is a photovoltaic structure capable of converting light into electricity. A cell may have any size and any shape, and may be created from a variety of materials. For example, a solar cell may be a photovoltaic structure fabricated on a silicon wafer or one or more thin films on a substrate material (e.g., glass, plastic, or any other material capable of supporting the photovoltaic structure), or a combination thereof.

A solar cell strip, photovoltaic strip, smaller cell, or strip is a portion or segment of a photovoltaic structure, such as a solar cell. A photovoltaic structure may be divided into a number of strips. A strip may have any shape and any size. The width and length of a strip may be the same or different from each other. Strips may be formed by further dividing a previously divided strip.

Finger lines, finger electrodes, and fingers refer to elongated, electrically conductive (e.g., metallic) electrodes of a photovoltaic structure for collecting carriers.

Busbar, bus line, or bus electrode refer to elongated, electrically conductive (e.g., metallic) electrodes of a photovoltaic structure for aggregating current collected by two or more finger lines. A busbar is usually wider than a finger line, and can be deposited or otherwise positioned anywhere on or within the photovoltaic structure. A single photovoltaic structure may have one or more busbars.

A photovoltaic structure can refer to a solar cell, a segment, or a solar cell strip. A photovoltaic structure is not limited to a device fabricated by a particular method. For example, a photovoltaic structure can be a crystalline silicon-based solar cell, a thin film solar cell, an amorphous silicon-based solar cell, a polycrystalline silicon-based solar cell, or a strip thereof.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary terracotta-barrel roof.

FIG. 2 shows an exemplary configuration of photovoltaic roof tiles on a house.

FIG. 3 shows a perspective view of the configuration of a photovoltaic roof tile.

FIG. 4 shows a cross-section of an exemplary photovoltaic module or roof tile.

FIG. 5 illustrates an exemplary configuration of a multi-unit group of photovoltaic roof tiles.

FIG. 6A illustrates an exemplary curved photovoltaic roof tile, according to an embodiment.

FIG. 6B shows the side and bottom views of a curved photovoltaic tile, according to one embodiment.

FIG. 6C shows the partial view of the barrel of a curved photovoltaic tile, according to one embodiment.

FIG. 6D illustrates an exemplary curved photovoltaic roof tile, according to an embodiment.

FIG. 6E illustrates an exemplary photovoltaic roof tile, according to an embodiment.

FIG. 6F illustrates a perspective view of a curved photovoltaic roof tile, according to an embodiment.

FIG. 7A illustrates self-shading in a curved photovoltaic roof tile.

FIG. 7B illustrates a situation where sunlight is incident vertically on a flat photovoltaic roof tile.

FIG. 7C illustrates a situation where sunlight is incident vertically on a curved photovoltaic roof tile.

FIG. 7D illustrates a situation where sunlight is incident on a curved photovoltaic roof tile at a shallow angle.

FIG. 7E illustrates exemplary electrical coupling among photovoltaic structures in curved photovoltaic roof tiles, according to an embodiment.

FIG. 8A illustrates side-by-side interlocking of adjacent curved photovoltaic roof tiles, according to an embodiment.

FIG. 8B illustrates the partial overlapping of adjacent curved photovoltaic roof tiles in the Y-direction, according to an embodiment.

FIG. 8C illustrates a top view of curved photovoltaic roof tiles partially overlapped along the Y-direction, according to an embodiment.

FIG. 9A illustrates a side view of a string of cascaded strips.

FIG. 9B illustrates cascaded strips in curved photovoltaic roof tiles, according to an embodiment.

FIG. 9C illustrates cascaded strips in adjacent curved photovoltaic roof tiles, according to an embodiment.

FIG. 10 shows a flowchart illustrating an exemplary process for fabricating a curved photovoltaic roof tile, according to an embodiment.

In the figures, like reference numerals refer to the same figure elements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the disclosed system is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Overview

Embodiments of the disclosed system solve the problem of providing curved photovoltaic (PV) roof tiles by using a curved transparent enclosure structure with multiple flat facets capable of accommodating flat PV structures. The light-facing (top) side of the enclosure structure can have a curved surface, and the opposite (bottom) side of the enclosure structure can have flat facets for accommodating flat PV structures. The flat facets can follow the contour of the curved surface.

The PV structures can be electrically connected in series or parallel. In particular, parallel electrical connections can aggregate the current produced by multiple PV structures, even if shading and different angles of incident sunlight result in differences among the individual currents.

While PV roof tiles offer solar power generation in an aesthetic and weather-protective design, it is desirable to extend these benefits to a broader variety of roofing materials, including ones with curved surfaces. For example, due to aesthetic preferences or climate, consumers may prefer terracotta-barrel tiles or other curved roof tiles. In addition to the curved tile, architectural features such as spires or the roofing surface may be curved (e.g., domed or conical roofs). Designing solar tiles with curved surfaces can be challenging. One possible solution is to design PV cells that are curved or flexible. However, such approaches would require elaborate changes in device structure, materials, and interconnection.

FIG. 1 illustrates an exemplary roof with terracotta-barrel tiles. A typical terracotta-barrel roof is covered by curved roof tiles 102, which can include a curved portion 104 and an optional flat portion 106. In some cases, the tile may include only the curved portion without a flat portion. In the example shown in FIG. 1, the curved portion of a tile can have a substantially cylindrical shape, with a longitudinal axis Y pointing toward a ridge or pinnacle of the roof. Other curved shapes are also possible.

Adjacent roof tiles can be arranged so that their curved portions align along the Y-direction. The flat portion of a tile can contact the curved portion of an adjacent tile along a latitudinal X-direction, which may correspond to the axis of the roof's ridge or another surface of constant height along the roof. In some cases, the roof may be flat or level, or may slope along both axes, as in a hip or tented roof. Other shapes and configurations of curved roofs (such as domed or conical roofs) and/or curved roof tiles are possible.

The disclosed system and methods can fit multiple PV structures onto a curved PV roof tile such as roof tile 102, thereby allowing a curved roof or a roof with curved tiles to produce solar power. The disclosed curved enclosure structure's flat facets can approximate a curved surface, such as curved portion 104, while accommodating flat PV structures. The curved enclosure structure may include a top portion and a bottom portion that can be fastened together to enclose the PV structures. Alternatively, the enclosure structure can include a single top portion and a backsheet, which can jointly enclose the PV structures. In some embodiments, PV structures within a curved PV roof tile can be coupled in parallel to aggregate their output currents, which can differ from each other due to different incident angles of sunlight on the curved surface. At the same time, the tiles can be coupled in parallel in each row along the X-direction, and rows can be coupled in series in the Y-direction. In this way, the disclosed system can optimize the amount of solar power produced.

PV Modules and Roof Tiles

The disclosed system and methods may be used to form PV modules or rooftop tiles with curved surfaces. In general, a PV module (or panel) can include one or more solar cells encapsulated between a top glass cover and a backsheet or back glass cover. A PV roof tile (or solar roof tile) is a type of PV module shaped like a roof tile and typically enclosing fewer solar cells than a conventional solar panel. Note that such PV roof tiles can function as both PV modules and roof tiles at the same time. PV roof tiles and modules are described in more detail in U.S. Provisional Patent Application No. 62/465,694, Attorney Docket Number P357-1PUS, entitled SYSTEM AND METHOD FOR PACKAGING PHOTOVOLTAIC ROOF TILES, filed Mar. 1, 2017, which is incorporated herein by reference. In some embodiments, the system disclosed herein can be applied to PV roof tiles and/or PV modules.

FIG. 2 shows an exemplary configuration of photovoltaic roof tiles on a house. PV roof tiles 200 can be installed on a house like conventional roof tiles or shingles. Particularly, a PV roof tile can be placed with other tiles in such a way as to prevent water from entering the building.

A respective PV structure (also referred to as PV cell or solar cell) in a PV roof tile can include one or more electrodes such as busbars and finger lines, and can connect mechanically and electrically to other cells. The finger lines can collect carriers from the cell, while the busbars can aggregate current from several finger lines. Separate PV cells within a tile can be electrically coupled by a tab, via their respective busbars, to create in-series or parallel connections. For example, a tabbing strip can substantially cover a respective busbar (which aggregates current from the finger lines) on the front side of a PV cell, and couple the PV cell to the back side of an adjacent PV cell. Moreover, electrical connections can be made between adjacent tiles, so that a number of PV roof tiles can jointly provide electrical power.

FIG. 3 shows a perspective view of the configuration of a photovoltaic roof tile. In this view, PV cells 304 and 306 can be hermetically sealed between top glass cover 302 and backsheet 308, which jointly can protect the PV cells from the weather elements. Tabbing strips 312 can be in contact with front-side busbar electrodes of PV cell 304 (e.g., by covering the busbars) and extend beyond the left edge of glass 302, thereby serving as contact electrodes of a first polarity of the PV roof tile. Tabbing strips 312 can also be in contact with the back side of PV cell 306, creating an in-series connection between PV cell 304 and PV cell 306. Tabbing strips 314 can be in contact with front-side busbar electrodes of PV cell 306 and extend beyond the right-side edge of glass cover 302. Using long tabbing strips covering a substantial portion of a front-side electrode can ensure sufficient electrical contact, reducing the likelihood of detachment.

The foregoing descriptions of various embodiments have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present system to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present system.

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