In recent years, many legal dispositions have come into force, with the goal of increasing the share of renewable energies in buildings. Despite this, neither the European directives, nor the national programs for climate protection, have substantially contributed to improving the acceptance of photovoltaic (PV) installations specifically conceived for historical monuments and traditional buildings. The lack of suitable PV products on the market to bridge the gap between technology and tradition is another obstacle: the solar module manufacturers have not yet succeeded in offering visually and economically sound solutions to replace the traditional terracotta roofs with acceptable PV systems dedicated to traditional architecture. Since these buildings represent around 10 percent of the built environment, a considerable segment of the population is excluded from producing its own electricity using PV, often on grounds of national heritage legislation.
To respond to this situation, physicists, engineers and historians of architecture at CSEM have developed – in close cooperation with specialized Belgian PV manufacturer Issol – a PV module combining the properties of a high-standard PV-unit based on c-Si technology with a semi-matt and close to terracotta appearance. This was achieved by applying a layer of color onto the inner face of the front glass by means of an ultra-reliable printing process, both perfectly homogenous and highly translucent, with losses in efficiency in a range of 22 percent. An anodized aluminum peripheral frame of the same color guarantees an installation that is both simple and robust.
Apart from testing up to the marketability stage, the second issue was to demonstrate the convincing architectural features of the new PV-system. A mid-19th century farmhouse in Ecuvillens (FR) was identified as the ideal property to serve as a pilot project: the building itself is not listed as part of the national heritage, but rather the overall ensemble of the central village road where it is situated. The first terracotta-colored, fully integrated 30kWc PV roof of its kind was installed onsite in August 2017 and inaugurated the following October. The new terracotta-colored PV module has meanwhile been commercialized, and is available under the trade name “Solar-Terra”. The project has since then achieved worldwide press coverage, and has gained an overwhelmingly positive reaction and reputation. Despite that fact, there are still open questions in terms of the marketability of such a product due to financial reasons. Without a clear reduction in production costs, the market is not willing to accept such a product over a wider base. Therefore, further R&D is required to bring color to high-performance PV systems in a more cost-effective way.