Photovoltaic glass: a window on the future

The period we are living is full of challenges. Safeguarding the planet is one of them. What better way to pursue this goal than with technology that combines innovation, clean energy and functionality?  

We are talking about photovoltaic glasses: a technology that has become interesting in the last period. With them you can replace traditional glass with glazed panels capable of converting incident and/or diffused light into electricity. They integrate perfectly into the structure of a building, becoming to all intents and purposes structural elements. This feature is very important: in fact, the current trend for buildings and skyscrapers is to design the outer shell covered with glass walls. This choice, causes significant dispersion and dramatically lowers the energy efficiency of the building.

This new generation of glazing would make it possible to overcome these problems by generating electricity that can be used for air conditioning the building through reversible heat pumps in both winter and summer, as well as limiting the penetration of sunlight in summer through shading.

The size and number of photovoltaic cells present determines the different glass configurations. These can be single, so as to have a more homogeneous glass with less shading, or agglomerated with disparate geometries.

Looking to the future, glass panels are being studied that use nanoparticles to concentrate solar radiation towards the photovoltaic cells. Concentrating photovoltaic glass is glass that collects sunlight and directs it towards strips of solar cells placed at the edges of the glass. They are called "concentrating" because, like concentrating photovoltaic panels, they need a reduced surface area of photovoltaic cells compared to that of light collection, which is given by the entire extension of the glass pane. They can even achieve high concentration factors ranging from 40X to 100X, depending on the concentration technology used.

Nanoparticle technology, on the other hand, concentrates only visible and ultraviolet light but not heat (which reduces the performance of conventional cells) on thin strips of silicon cells placed at the edges of the panel, i.e. where in normal opaque solar panels there would be the aluminum frame. A combination of fluorescent pigments and nanoparticles is used to direct light to the edge of the module in this particular implementation. Compared to classic silicon panels, these do not require direct light but work with diffuse light and use only 1/5 of the silicon, even only 1/10 in models that employ high-efficiency multi-junction cells. In addition, they have a remarkable electrical power, comparable to conventional photovoltaic panels, and achieve a conversion efficiency of light into electricity of 20%, far greater than traditional technologies. In this regard, in the future we will see implemented these panels in a glass version (transparent), so as to be used instead of glass windows in large buildings.

Another perspective instead exploits the use of Fresnell lenses, with which it is possible to obtain concentration values an order of magnitude higher than traditional lenses (500X). Thanks to this ability, combined with devices that allow the panel to track the light source, high values of energy conversion efficiency can be obtained. It should be noted that in the latter case we no longer speak of solar glass but of classic panels, which, given their compactness, have the advantage of being much easier to install.

There are numerous architectural projects undertaken which integrate photovoltaic glass into the structure of the building¸ for example, the pergola of Tanjong Pagar in the financial center of Singapore and the Dubai Frame, a building with a peculiar rectangular structure which recalls a framed photograph, situated in the Zabeel Park in Dubai.

Written by Roberto del Bo from the VGen Engineering Hub

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