In the shift away from fossil fuel energy sources, there has been a huge expansion in solar power. We’ve seen solar thermal plants in the desert and photovoltaic panel farms covering huge areas of land, but perhaps the most potential comes from placing the panels on rooftops. In some parts of the world this is encouraged through a system of subsidies, as is the case in Italy. But what if your building is part of a protected world heritage site such as the Roman city of Pompeii? The answer comes in the form of traditional roof tiles that hide their photovoltaic elements under a polymer skin that looks for all the world like a traditional Roman pan tile. As is so often the case with such products, the manufacturer’s description page is cagey about the details in the name of protecting their invention. What they do tell us is that the tile uses conventional solar cells mounted underneath the polymer layer, which is described as “opaque at the sight but translucent to sun rays“. This sounds like an inherent contradiction, so naturally, we’re intrigued as to how it works.
A clue comes in its claimed properties, one of which is that it has photocatalytic self-cleaning. This implies the presence of a titanium dioxide film which generates oxygen free radicals from air in the presense of light. Titanium dioxide is ubiquitous as a white pigment and food colouring, but it also has interesting colour properties in thin films, being used in iridescent and reflective effects. If we wanted to make a guess as to how these work, we’d expect them to use a carefully selected dye whose spectral profile doesn’t interfere too much with that of the solar cells, along with the colour effects bestowed by a titanium dioxide thin film.
However they work, these tiles are a fascinating bit of technology and we’d love to know more. It’s certainly not the first solar roofing innovation we’ve brought you.