Tesla filed a patent 'External electrical contact for solar roof tiles'

During the earning call for 4Q 2019, Tesla CEO Elon Musk said that Solar Roof will be a major product of the company.

"We see a lot of interest and it's just a question of refining the installation process."
"It's a question of if people want a live roof. It's the future we want." 

The seriousness of the company's intentions is evidenced by its actions. Tesla filed a patent 'External electrical contact for solar roof tiles.'

International Filing Date: 31.07.2019
Publication Date: 06.02.2020

This disclosure is generally related to photovoltaic (or“PV”) roof tile modules. More specifically, this disclosure is related to roof tile modules with external electrical connectors.

In residential and commercial solar energy installations, a building’s roof typically is installed with photovoltaic (PV) modules, also called PV or solar panels, that can include a two-dimensional array of solar cells. 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. The 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 encloses fewer solar cells than a conventional solar panel.

The front and back covers can be fortified glass or other material that can protect the PV cells from the weather elements. Similar to a conventional PV panel, the PV roof tile can include an encapsulating layer, such as an organic polymer. A lamination process can seal the solar cells between the front and back covers.

To facilitate scalable production and easy installation of PV roof tiles, a group of tiles can be fabricated together as a single module. Like conventional PV panels, electrical interconnections among PV modules are needed.

One embodiment can provide a photovoltaic roof tile module. The photovoltaic roof tile module can include a front glass cover, a back glass cover, a plurality of photovoltaic structures positioned between the front and back glass covers, and an internal circuit component electrically coupled to the plurality of photovoltaic structures. The internal circuit component is positioned between the front and back glass covers. The back glass cover can include at least one through hole and a metallic plug inserted inside the through hole. A first surface of the metallic plug can electrically couple to the internal circuit component, and a second opposite surface of the metallic plug can be exposed to surroundings external to the photovoltaic roof tile module, thereby facilitating electrical coupling between the photovoltaic roof tile module and another photovoltaic roof tile module.

FIG. 2 shows the perspective view of an exemplary photovoltaic roof tile, according to an embodiment.

In a variation on this embodiment, a respective photovoltaic structure can include a first edge busbar positioned near an edge of a first surface and a second edge busbar positioned near an opposite edge of a second surface. The plurality of photovoltaic structures can be arranged in such a way that the first edge busbar of a first photovoltaic structure overlaps the second edge busbar of an adjacent photovoltaic structure, thereby forming a cascaded string that includes the plurality of photovoltaic structures coupled to each other in series.

In a further variation, the internal circuit component can include one of: a standalone metallic strip electrically coupled to an edge busbar of the cascaded string, or a metallic strip pre-laid onto an interior surface of the back glass cover. The second opposite surface of the metallic plug can be flush with an exterior surface of the back glass cover. The first surface of the metallic plug can be in direct contact with the internal circuit component.

The first surface of the metallic plug can be textured to ensure a sufficient contact area between the first surface of the metallic plug and the internal circuit component. The photovoltaic roof tile module can further include a gasket inserted inside the through hole, and the metallic plug can be inserted inside a center opening of the gasket. The metallic plug can be configured in such a way that a portion of the metallic plug is slightly larger than the center opening, thus preventing the metallic plug from slipping through the center opening. The photovoltaic roof tile module can further include a junction box attached to the back glass cover. The junction box covers the through hole and includes a lead wire coupled to the second opposite surface of the metallic plug.

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.

A “cascade” is a physical arrangement of solar cells or strips that are electrically coupled via electrodes on or near their edges. There are many ways to physically connect adjacent photovoltaic structures. One way is to physically overlap them at or near the edges (e.g., one edge on the positive side and another edge on the negative side) of adjacent structures. This overlapping process is sometimes referred to as “shingling.” Two or more cascading photovoltaic structures or strips can be referred to as a “cascaded string,” or more simply as a “string.”

“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.

Embodiments of the invention solve at least the technical problem of enabling low-cost and reliable electrical interconnections among solar roof tile modules. More specifically, each solar roof tile module can include, on its back cover, two external electrical contacts, one for each polarity. In some embodiments, an external electrical contact can be in the form of a metallic plug inserted inside a through hole formed on the back cover of the tile module. In some embodiments, a surface of the metallic plug can be textured to ensure reliable electrical coupling between the metallic plug and the internal electrical contacts of the tile module. Moreover, the other surface of the metallic plug can be substantially on the same plane as the exterior surface of the back cover, thus enabling a simplified electrical coupling between the metallic plug and a junction box attached to the back cover.

FIG. 10A shows a metallic plug inserted into a gasket, according to one embodiment.
FIG. 10B shows the cross-sectional view of the metallic plug and gasket, according to one embodiment.
FIG. 10C shows the bottom view of the metallic plug and gasket, according to one embodiment.

FIG. 8A shows a specially designed attachment pad, according to one embodiment.
FIG. 8B shows the coupling between the attachment pad and the internal circuit of a solar tile module, according to one embodiment.

FIG. 11 shows the coupling between a junction box and a solar roof tile module, according to one embodiment.

Featured image: Tesla