The year that just passed will be remembered for the World Expo in Milan, that introduced a variety of unconventional designs in the contemporary architectural scene. Among the innovative constructions, the German pavilion by Schmidhuber stood out for its tree-like structures covered by a photovoltaic membrane.
The idea of a “solar tree” is not original: some precedents are the Solar Tree by Ross Lovegrove, the Solar Forest by Neville Mars and the eTree by Sologic. What was new about the photovoltaic membrane of the German pavilion at Expo 2015 was the application at the architectural scale of custom-designed organic solar cells (OPV). According to the architects, the printed hexagonal OPV modules were designed to match their creative ideas and to be an integral part of the overall architecture. Produced by Belectric OPV GmbH and laminated between clear plastic sheets, the solar modules were attached to a light steel mesh that served as supporting structure for the electrical wires interconnecting the solar cells. The solar modules therefore composed a permeable skin rather than a continuous membrane, where interestingly the overall electric circuit was not printed like the OPV modules. The energy generated by the photovoltaic membrane contributed to powering the pavilion’s LED lighting at night, thus helping reduce the use of non-renewable sources.
I believe the German pavilion at Expo 2015 was a valuable, thought-provoking architectural experiment. It could be argued that the aesthetic performance of the solar membrane was still far from optimal and that despite the creative design to show off the photovoltaic modules were not always clearly visible from the visitors’ level, but this could not be said without the prototype being built and proves that advances in the architectural integration of photovoltaics are being made.
I am quite skeptical about the claim in the architects’ video that the organic photovoltaic modules in the pavilion’s skin “produce as much energy as conventional solar panels”. As reported by NREL in the latest solar cell efficiency chart, the efficiency of organic photovoltaic modules is still much lower than that of crystalline silicon solar panels, as is the durability.
Unfortunately, photovoltaics are often presented and mistaken by architects as “wonder materials” with some sort of “super powers”, that can replace traditional cladding materials. On the contrary, photovoltaics have considerable limitations and need to be well understood for their potential to be fully exploited.
A good architect would not expose non-ventilated natural wood to humidity, nor would he propose an aluminium sheet cladding with an inadequate supporting structure unless a crumpled effect was sought. Similarly, I think the limitations of photovoltaics for architectural applications need to be well understood for both energy generation and aesthetics to be optimal, which is why academic research in this field is still ongoing and I am fully immersed in it. I confess it annoys me when a relatively new material is presented as a “wonder material”. There are no “wonder materials”, but only materials to be understood, with their issues to be addressed. Storytelling tends to embellish and distort reality and we need to watch out for this by fighting misinformation. I believe critical thinking, rather than some naïve optimism, can stimulate positive advances in architecture as in any other aspects of our lives. My wishes for the new year are therefore for everyone to think more critically and particularly for designers to seek intelligent solutions over media attention.