The project

Solar Spline: Lightweight architectural construction uses printed organic photovoltaic modules

Following the successful integration of OPV modules in the glass façade of the exterior elevator shaft of the Sun Pharmacy in Marburg in 2016, ARMOR solar power films GmbH (formerly OPVIUS) and Timo Carl of AiD Architecture decided to carry out a second joint project in Kassel. This time the project took place in an interdisciplinary, university context, as a cooperation between the Department of Experimental Design and Construction (EEK in its German acronym) run by Prof. Frank Stepper, Timo Carl at the University of Kassel on the architectural side, and Dr. Markus Schein, leader of the academic workshop for Digital Design and Production Techniques at the School of Art Kassel. Students from the fields of architecture, design, environmental engineering, and information technology were all involved in the project.

The experimental prototype “Solar Spline” was presented at the Art School’s yearly exhibition, which is also the site of Documenta 14, and will be displayed there until the beginning of October.

The structure is made up of 300 printed organic photovoltaic modules that are integrated into an ultra-lightweight construction that appears to be suspended in the air. A mesh of cable carriers made of thin aluminium tubes are stretched between main cables, and serve both as a cable route and to hold the modules in place. The modules themselves are integrated into a sandwich solution made of a transparent, highly-taught carrier-surface with a reflective film coating that was developed especially for this project.

All in lightness

The low weight and ease of integration of the OPV modules play an important role here. With a surface area of 30 m² and a total installation area of 100 m², the "Solar Spline" weighs less than 120 kg in total, which not only facilitated installation, but also kept the static load low. The lightweight construction principle particularly benefits the topics of energy production and shading in urban spaces, and creates a flexible, seemingly light and mobile structure.

The resulting Solar Cloud is supported by a three dimensional cable structure, and more than 10 anchor points. The anchor cables and suspended cables were provided by Carl Stahl Architektur from Süßen, who also reviewed the structure of the digital model. A motor pulls on two cables which moves the solar cells, allowing them to follow the sunlight during the day, and bringing them to a resting position when the light is low which opens up the space beneath the cells to the sky.

As part of the installation, and in order to draw attention to the energy output generated by the organic photovoltaics, every eighth module drives a ventilator, which gets faster and louder with increased energy input, so that those standing close-by can perceive a “swarm of ventilators”.


The Solar Spline, which we developed using products from ARMOR solar power films and Carl Stahl Architektur, not only influences the function of energy extraction, but also the quality of its environment through the creation of shade and through a lively show of light reflection, triggered by the movement of the Solar Cloud in the wind. Rather than understanding architecture as a conventional mass-produced product, we want to develop it as three-dimensional experience space.

Timo Carl, research associate at EEK
Solar Spline: Lightweight architectural construction uses printed organic photovoltaic modules