Spectral: Vienna Start-Up Turns Old Facades Into Solar Power Plants
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Solar panels belong on the roof? The Vienna start-up Spectral is turning entire facades into power plants and has just unveiled its “Structural Solar Façade.” The system replaces conventional facade cladding with semi-transparent photovoltaic modules and, according to the company, can be retrofitted to existing buildings with little effort.
Power From a Cold Storage Hall
The first installation hangs on the Eisfabrik, an ice factory in Vienna’s Brigittenau district, where it has been producing electricity since September, according to Spectral’s press release. The key figures of the pilot project:
- Area: 24 square meters with 32 modules
- Output: 1,840 watts peak
- Transparency: 50 percent, allowing daylight to pass through the facade
- Technology: cadmium telluride thin-film modules measuring 60 by 120 centimeters on a lightweight steel substructure
The City of Vienna supports the project in principle as part of its solar power initiative, without direct funding. The engineering firm Bollinger + Grohmann handled the structural engineering, Werner Sobek did the detailed planning, and Montron GmbH carried out the installation.
A Facade That Provides Shade
At the heart of the system is a proprietary mounting system that allows the modules to be attached to existing buildings quickly and with minimal intervention. In addition to generating electricity, the facade is meant to act as sun protection, shading buildings during increasingly hot summers while light still reaches the interior through the semi-transparent modules. Spectral is targeting industrial, logistics and office buildings, public buildings and multistory residential buildings, both in new construction and in renovation.
Spectral was founded by the architects Zsuzsa Péter and Anna Gulinska, who set up the company as spectral design GmbH in early 2024 and each own half of it. Their approach is that solar systems should be part of the architecture and have their own aesthetic quality. The two founders say systems like this could help shape the look of buildings and cities in a more sustainable future.
The Competition in the Building Envelope
Spectral is not alone in the market for building-integrated photovoltaics. In Austria, Ertex Solar in Amstetten has been producing solar glass for facades and glass roofs for years. In Switzerland, Megasol offers colored facade modules, and the Canadian manufacturer Mitrex sells solar panels that look like brick, stone or metal. Spectral, by contrast, relies on a visible, semi-transparent structure that covers existing facades instead of imitating them.
Less Power per Square Meter
The solar facade is not a sure-fire success, however. The pilot project’s figures work out to about 77 watts peak per square meter. Conventional crystalline silicon roof modules now achieve more than 200 watts peak per square meter. One reason is the 50 percent transparency: Light that passes through the facade is not converted into electricity. In addition, vertically mounted modules capture less sunlight over the year than optimally tilted rooftop systems, although they perform comparatively well in winter when the sun is low. Spectral has not yet disclosed costs or prices.
