International. Researchers at the Fraunhofer Center for CSP Silicon Photovoltaic have found that photovoltaic elements on facades can be a useful way to supplement the power supply. If properly designed, they can be attractively integrated and deliver 50 percent more energy than existing types of wall-mounted PV elements. Even concrete walls are suitable.
Photovoltaic elements belong to the roof; after all, that's where they get the most sunlight. But that is only partially true: it makes sense to additionally install photovoltaic elements on the facades. On the one hand, they make use of space that would not otherwise be used, and on the other, the energy they collect can usefully supplement the power supply. Currently, however, little use is made of this opportunity, as the sun usually shines on the facades at an unfavorable angle, and the elements themselves tend not to be aesthetically appealing.
Attractive stylish facades
In their SOLAR.shell project, the researchers in Halle demonstrated, together with architects from the Leipzig University of Applied Sciences (HTWK Leipzig), that this is anything but a decisive factor. They presented a solar façade that remedies these problems. "The photovoltaic elements integrated into this façade deliver up to 50 percent more solar energy than modules mounted perpendicular to the walls of buildings," says Sebastian Schindler, project manager at Fraunhofer CSP. "In addition, the façade offers visual appeal." HTWK architects developed the idea and designs. How should individual PV elements be tilted to capture as much solar irradiation as possible? How big should the modules be and how many solar cells should ideally include? The team's findings were presented in a 2x3-meter demonstrator made of aluminum composite panels with a total of nine integrated solar modules. Fraunhofer experts offered their expertise, advice and assistance, and the photovoltaic elements used in the demonstrator also come from Fraunhofer CSP.
Solar modules on concrete facades
In collaboration with HTWK Leipzig and TU Dresden, Fraunhofer CSP researchers also developed suitable options for integrating photovoltaic elements into concrete facades, more specifically into facades made of carbon concrete, a material developed by a consortium of more than 150 partners in the "C3 – Carbon Concrete Composite Project".
The required stability of concrete comes from carbon fibers rather than steel cables. "At Fraunhofer CSP, we looked at how photovoltaic elements can best be mounted on this type of carbon concrete façade, i.e. how to get the optimal result by combining this novel concrete with solar energy production," explains Schindler. To this end, the researchers devised three different concepts and methods for integrating photovoltaic elements into façade sections.
Solar modules can be included directly by melting concrete sections or laminating or adhering to concrete slabs. The modules can also be attached to the concrete slabs using asparagus fasteners, screw connections or other means, making it easy to remove for maintenance or repairs. "We were able to show that all three mounting options are technically feasible," Schindler says.
One of the main challenges is to ensure that the method used to produce the concrete sections is compatible with the dimensional accuracy required of the photovoltaic modules. This is done, for example, by melting the concrete parts with a depression that is the perfect size to accommodate a module. In this way, the desired orientation with respect to solar irradiation and overall design is preserved. "Dimensional accuracy needs to be implemented directly in the concrete section," Schindler says. It should also be ensured that photovoltaic modules are not fastened where the concrete is particularly thin or where the carbon fibers are located, as this would affect the strength of the façade elements. The project has since been successfully completed.
Source: Fraunhofer.
