Solar Roof Tiles

There has been long-held interest in solar roof shingles or tiles that provide complete solar roofing integrated in the building roof. Today, BIPV only claims about a 1 percent share of total PV installations worldwide, but several analysts foresee good times ahead for this niche technology. Here you will find a discussion of why solar roof tiles, solar shingles and integrated solar roofing does NOT yet match the price or performance of traditional rack-mounted solar panels.

About Solar Roof Shingles

Also commonly known as BIPV, for building integrated photovoltaic, this kind of solar roofing comprises a group of solar PV technologies that are built into (instead of installed onto) the host structure and may actually replace some building materials. BIPVs potential to seamlessly integrate into the building to create a solar roof holds aesthetic appeal for homeowners, architects, builders and real estate holders.

There are some important performance variables to consider when calculating energy costs of a BIPV system. For starters, BIPV modules may experience higher operating temperatures because, unlike rack-mounted PV, they are flush with the building surface and do not permit airflow between module and host structure. Higher temperatures may degrade the semiconducting material of the module, which could decrease the conversion efficiency more quickly and precipitate early failure.

Some PV materials used in solar roof tiles, like amorphous silicon, which has a flexible form factor and hence a potentially greater integration potential are more susceptible to thermally accelerated degradation than others. Also, PV materials with greater integration potential, such as thin films and flexible PV technologies, generally have lower efficiencies to begin with, and this may contribute to higher energy costs with solar roof tiles.

Finally, because BIPV modules typically contain less semiconducting material than traditional PV modules, a BIPV system will likely produce less electricity than a flat-panel system of the same size. And even though BIPV can increase the PV-suitable space of a building (i.e., more than just the roof is eligible for installation), the sub-optimal angle of irradiation on these non-horizontal surfaces, combined with the obstructions posed by surrounding buildings, create diminished returns.

Several companies have been testing integrated solar roof tiles, but with limited availability and disappointing results. The most promising may be the Dow PowerHouse solar shingles currently being tested in California, Colorado and Texas. But there is no reason to wait for low cost solar panels with today's PV solar panels available for under $1 per watt and proven to last 25 years or more.