What are these new invisible solar panels that blend into the environment?

They are ugly and they distort the landscape. Critics of solar panels have no shortage of arguments to criticize them. Often black or dark blue, crossed by a grid of fine white or silver stripes, they can be seen from afar, shining in the sun. They contrast with typical architecture in granite, zinc or colored bricks for example.

Christophe Ménézo, researcher at CNRS and director of the Solar Energy Research Federation, describes this strange mixture of colors: “The dark parts represent the voltaic cells made of cast silicon. If they are polycrystalline, they project bluish reflections. The lighter lines are the silver microwelds which connect the photovoltaic cells. All around, the silver frame represents the aluminum which prevents moisture from seeping into the panel.”

Problem is, despite the promise of energy savings, individuals and local authorities are refusing to install solar panels. They do not want to alter the aesthetics of the building. Owners of buildings located in classified areas or near a historic monument do not have the right. It is impossible to modify the exterior appearance of roofs and facades. The owners require the agreement of the Architects of Buildings of France. This procedure remains long and acceptances rare.

Today, researchers are developing various so-called “active” facade, glass and roof elements. Organic, camouflaged or transparent, solar panels generate just as much energy by transforming solar radiation.

Integrated solar panels, an aesthetic solution

First, technological advances now make it possible to eliminate the aluminum frame. “Polymer with a stone or wood effect can replace it”, rejoices Christophe Ménézo. The microwelds attach the photovoltaic cells to the back and are no longer visible. “A thin layer of glass protects the panel on the front. We can anneal the glass with any printed shape”, specifies the researcher. Developers can transform the solar panel into slate, Parisian-style zinc, Toulouse-style pink brick or give it a wood effect.

Solar tiles can be completely integrated into the roof. Objective, remove part of the roof to install solar panels in the form of tiles. As waterproof as a traditional roof, lighter and more robust, the photovoltaic tile heats up little and maintains the same efficiency all day long: “We have two tiles joined together. Only one of the tiles carries the wiring and electronics. Air blades separate them and shift the temperature peak. As a result, if it is very hot at 4 p.m., the panel remains at a temperature measured and continues to produce as much electricity as ever”, rejoices Christophe Ménézo. Smaller solar tiles produce less. But installed in series, they can produce the same power as a solar panel.

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A sector that continues to innovate and seek solutions

Researchers are also developing semi- or completely transparent solar panels (called biverre). They consist of two superimposed glass plates which encapsulate photovoltaic cells. This double layer increases the resistance of the panels. “Photovoltaic cells use gallium. This metal covers a slightly wider range of solar wavelength radiation than silicon. It operates with little solar intensity: it can in particular be installed in northern countries or on facades. For the moment, these panels remain very expensive and do not yet offer sufficient performance.regrets Christophe Ménézo.

Other promising photovoltaic panels: organic panels. The technology is based on the use of organic molecules (of plant or animal origin) to capture sunlight. Extremely light, they are applied like paint or wallpaper to existing roofs: “It is a photovoltaic ink printed inside a polymer under a thin, semi-transparent layer”, describes the researcher. Still being perfected, this technology does not offer sufficient performance and fears UV and humidity. “Today, you find it on gadgets such as rechargeable backpacks”specifies Christophe Ménézo.

Bifacial (or double-sided) panels allow light to pass through. Semi-transparent, they transform the sun’s rays on both sides. While one captures the light directly, the other takes advantage of the translucency of the materials to capture the rays which are reflected behind the solar panel on the ground, a wall, a tile, etc. They can produce at their full capacity even if the The sun hits them horizontally in the morning or evening.

Expensive and poorly installed technologies

Christophe Ménézo recognizes it bluntly, French architects are having difficulty getting started with these new solar panels. “Technological innovations, like micro-welds at the rear, cost more. Integration into the frame requires tailor-made.” The installation of solar tiles increases the bill: for the supply and installation, it costs between 1000 and 2000 euros per square meter. Another pitfall pointed out by the researcher: the time allocated to construction. “More and more developers are trying to include it in their construction. The problem is that between the moment they program the budget and the moment the operation starts, many years can pass. As a result, the prices of materials and real estate are evolving and to restore the accounts, these integrated solar roofs are falling by the wayside.” In terms of performance, note a slight drop of 3 to 5% depending on the technologies.

In France, few buildings have been launched. Christophe Ménézo retains the Poulains lighthouse on Belle-Île. “Italy is a leader on the subject. Even on historic buildings, like the Vatican, the Italians integrate as many roofs as possible.” In the United States, the city of San Francisco now requires that the roofs of new buildings have solar panels. Enough to promote the progression of aesthetics.