Photovoltaic Glass

Photovoltaic glass is a special glass with integrated solar cells that convert solar energy into electricity. This means that the power for an entire building can be produced within the roof and façade areas. The solar cells are embedded between two glass panes and a special resin is filled between the panes, securely wrapping the solar cells on all sides. Each individual cell has two electrical connections, which are linked to other cells in the module, to form a system which generates a direct electrical current.

Need for Photovoltaic Glass

Apart from providing privacy and protection from noise and rain, other features such as thermal insulation and shading are becoming increasingly desirable. All of these functionalities can be obtained simply by installing photovoltaic glass to the shell of a building.

How does it work?

As seen in the science behind PV, a photovoltaic cell is created when a positively charged (P-type) layer of silicon is placed against a negatively charged (N-type) layer of silicon to create a diode and this diode is connected in a circuit via metal conductors on the top and bottom of the silicon sandwich. Though different types of photovoltaics vary in their structure, they generally include the following elements:

1. The cell or multiple cells are the core of the photovoltaic panel.
2. A glass cover is placed over the photovoltaic cell to protect it from the elements while allowing sunlight to pass through to the cell.
3. An additional plastic anti-reflective sheet is often used to enhance the effect of the glass cover and anti-reflective coating of the cell to block reflection.
4. A panel backing (typically plastic) and frame complete the photovoltaic panel, holding all the pieces together and protecting it from damage during installation.
   

Production

The solar cells are embedded between two glass panes, and a special resin fills between the panes, securely wrapping the solar cells on all sides. Each individual cell has two electrical photovoltaic modules (PVs).

A photovoltaic module or photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. The photovoltaic module, known more commonly as the solar panel, is then used as a component in a larger photovoltaic system to offer electricity for commercial and residential applications.

Photovoltaic modules enable the active use of solar radiation by turning it into electrical energy; in addition, they can also represent a form of passive solar protection. The most well known PV products are silicon solar cells, available in three types:

1. Monocrystalline:

The monocrystalline solar cells are opaque, blue, or dark grey to black, and they have a high efficiency (14% to 16%). They are expensive because they are made from silicon crystals in a complicated manufacturing process.

2. Poly- or multicrystaffine:

The polycrystalline solar cells are mostly blue or opaque. These are cheaper because they are made from poured silicon blocks, but they have a lower efficiency (14%). Crystalline solar cells are produced as 0.4mm thick discs in sizes from 10 x 10cm to 15 x 15cm. These discs are then put together to form modules and embedded with resin in the cavity in a laminated glass unit. According to composition, the result can be either a transparent, translucent or a non-transparent module.

Light transmission through transparent and translucent modules can be set from 4% to 30% according to the choice of spacing. Special light-scattering and insulating glass elements have been developed to meet both the needs in terms of lighting and insulation as well as the desire to maintain and exploit the corporate image as protected through the façade. In the exterior laminated glass, PV cells have a 5mm gap between them. On the inside, a laminated glass with an opaque interlayer is used.

3. Amorphous:

Amorphous is a non-crystalline solar cells. Amorphous modules are transparent, can be used as window glazing in usual windows, sunspaces, they can be integrated into roofs etc. Transparent modules can be also part of energy efficient glazing, where they are used instead of usual glass.

Optimized exploitation of solar energy can be achieved by combining several thin film layers with different spectral responses. So-called tandem cells have reached up to 12% efficiency under laboratory conditions, slightly higher values seem possible. Further possibilities are offered by triple cells which consist of a succession of three thin film layers Efficiencies of 10% in production quantities are becoming realistic.