Photovoltaic glass and the opportunity to create solar buildings

We all know what a solar panel looks like. And in cities they are usually placed on rooftops. However, photovoltaic glass can change everything.

When we see a skyscraper, so common nowadays, several questions arise. The first is what it must be like to climb up all those floors on the stairs. The second, how much work it will be to clean all those windows that cover practically all the facade. And the third, how much electrical energy will this giant of steel and glass spend.

It is clear that electricity consumption is higher in a building of fifteen or twenty floors than in one of five or less. And although in recent times improvements have been incorporated in favor of energy efficiency, such as optimized ventilation and insulation systems or solar panels on rooftops, there is still a long way to go.

And this is where the question arises, what if we could fill the facades of skyscrapers or any building with photovoltaic glass? Windows that, in addition to facilitating the entry of sunlight and isolating us from temperature and external noise, convert solar energy into electrical energy. All of this by taking advantage of the enormous surface area that a facade represents instead of a smaller rooftop.

A technology in constant evolution

Although there are patents on solar panels as early as the late 19th century, it is not until the second half of the 20th century that solar energy begins to be taken seriously. In part, thanks to the space race. This is precisely the first purpose of Bell Labs' research.

The first problem that the first solar panels will encounter will be their efficiency in converting solar energy to electricity. In 1959, Hoffman Electronics created solar panels with 10% efficiency. And the next year it will go up to 14%. Only two years earlier, the United States had launched the fourth artificial satellite in history and the first to have a solar panel that converted at 9% efficiency.

Thus, although their external appearance is usually very similar, and we are all familiar with dark blue solar panels, the changes over all these years have been aimed at obtaining greater conversion efficiency by combining new elements.

The most promising projects, for example, have reached percentages of 37% using polycrystalline photovoltaic panels by 2018 or 47% with the help of solar panels using technologies such as concentrators or multi-junction solar cells. This last record was achieved at the National Renewable Energy Laboratory in Colorado, USA, last year.

This same 2020, the most promising research is focused on the search for efficient and cheap solar panels. Using perovskite solar cells, efficiency rates of 25% have been achieved at a lower cost than classic silicon solar panels.

Photovoltaic glass

But on the path of the search for conversion efficiency, research related to solar energy has managed to find alternatives to the current solar panels in order to better integrate them where they are needed. One example is photovoltaic glass.

Photovoltaic glass has an obvious advantage. You can place it anywhere, since it is transparent and can be integrated into any surface. To begin with, on windows and glass facades of buildings of considerable size, as I mentioned at the beginning. But photovoltaic glass could also be integrated into vehicles with a solar roof or smart phones. Can you imagine being able to charge your iPhone while leaving it on the table for a few minutes?

One of the most important examples of the technology known as photovoltaic glass was born in 2014 in the facilities of Michigan State University. Using an invisible polymer film, it converted ordinary glass into a transparent solar panel. Its technical name, transparent luminescent solar concentrator.

El vidrio fotovoltaico y la oportunidad de crear edificios solares

As the university itself explains in its official online media, since it is a thin and transparent film, it could be integrated into any surface.

The discovery was based on research into luminescent plastic materials. The objective, to find economic alternatives to convert the sun's rays into electricity beyond the current solar panels. The problem they encountered so far was that the elements tested were inefficient and not very transparent.

In fact, the Japanese company Sharp had already presented photovoltaic glass in 2012, although its level of transparency could be improved. However, it could be used on surfaces where a completely transparent glass is not required, such as balconies or windows where direct light is not interested.

Present and future of photovoltaic glass

Jumping to the present time, companies like Onyx Solar already commercialize this type of technology. As it says in its official website, it offers "transparent architectural glass for buildings". In addition to "generating photovoltaic energy, it filters heat from entering the building". In its catalog, depending on the level of transparency of the photovoltaic glass, we can obtain between 28 and 58 watts peak per square metre. The more transparent it is, the less efficient it is.

The efficiency of photovoltaic glass technology is still lower than that of classic panels in terms of surface area, between 7% and 10%, but its advantage lies precisely in the fact that we can install it on a larger surface area, thus reducing the difference between one and the other.

El vidrio fotovoltaico y la oportunidad de crear edificios solares

But there are more private projects that already market solutions related to photovoltaic glass, such as the Greek Brite Solar or the American Ubiquitous Energy. Precisely the latter is a company born at the well-known MIT and co-founded by Richard Lunt, a member of the Michigan State University team that achieved the first completely transparent photovoltaic glass.

The future of photovoltaic glass lies in improving the combination of efficiency and transparency. The greater the transparency, the less energy is generated, something that will have to be improved in the future in order to fully integrate this technology into homes and all kinds of buildings with windows.