So far I have written about solar building envelopes, solar-powered lighting and unconventional solar designs, but I have never really covered specifically what is probably the most diffused application of solar technologies in urban environments: solar roofs.
Many solar products available on the market for roof installations are not aesthetically pleasing and are often designed to be applied onto roofs rather than to be integrated into the building fabric by replacing conventional cladding components. Nonetheless, some new solar roof products are worth being mentioned, especially considering that in many cases the roof is the most suitable part of the building envelope for an efficient absorption of solar radiation.
In order to integrate solar panels seamlessly into roofs, customisation is a must. Among the factors that affect the visual impact of building-integrated solar installations, shape, material, colour and type of jointing characterising the modules play an essential role. As for the strictly functional aspects, solar roofs need to be exceptionally strong and weatherproof, while for better performance the overheating of photovoltaic modules should be prevented. Bearing this in mind, the Australian company Tractile Pty Ltd has developed a multifunctional, customisable solar roof system that combines electricity generation with solar water heating and roof insulation into tile products manufactured from composite materials for adaptable roof designs.
Associating photovoltaic and solar thermal technologies is highly advantageous, as water channels placed on the back of photovoltaic cells allow them to be cooled, while the electricity generated can power the solar heating system requiring water to be pumped to the roof. Test results on the award-winning Tractile products showed that by maintaining the photovoltaic modules at a maximum temperature of 35° C, their performance in terms of electrical output increased by up to 8% compared to that of conventional solar panels. The photovoltaic layer of Tractile modules is made of mono-crystalline silicon that generates 95Wp per tile and approximately 160Wp per square meter of solar roof. At the same time, the solar thermal panels provide a fossil-fuel-free system to supply hot water up to 75° C, that can be used for domestic hot water consumption, floor heating, pool heating or even in support to air-conditioning.
Tractile solar tiles are made of high performance composite materials that are lightweight and very strong at the same time, as they can withstand loads up to 250 kg and direct impact from flying debris. Additionally, the special interlocking system characterising Tractile products allows connections between tiles to block the penetration of water, wind and dust independently from the roof pitch which can vary from 10 to 90 degrees, meaning that Tractile solar cladding is suitable for façade applications as well.
Besides the relative freedom in designing the geometry of roofs, architects interested in including Tractile products in their projects are offered the possibility to select tiles coated in different hues to create multi-coloured designs. The coloured coatings both contribute to the aesthetics of the building and act as UV protection to preserve the tiles’ strength and durability. By inserting clear tiles, skylights can also be installed as part of the solar roofs, and the shape or size of special tile elements can be easily adapted by cutting them on site.
In conclusion, the solar roof system by Tractile Pty Ltd allows relative design freedom while integrating the production of both electricity and hot water from the sun into insulated cladding units. The combined technologies boost each other and have a great potential in improving the overall building performance towards zero-energy standards while opening up creative design possibilities.