BIPV: The Future of Solar and Flexible Substrates?
For now, a much better candidate for the attentions of flexible substrate providers lies in the building integrated PV (BIPV) sector. It is true that 2011 into 2012 seems like it will be a relatively weak period for the solar industry, whose subsidies are under threat in several important markets. However, we think that BIPV has a strong future because:
• BIPV can potentially introduce a new aesthetic that will translate into larger addressable markets and;
• BIPV can share the cost of the PV functionality and roofing/siding functionality on a common substrate.
What is important from the point of view of the flexible substrate market is that:
• BIPV substrates must often be conformable and may have to be actually flexible. This feature helps them with aesthetics, but also helps with installation, since building fabrics are generally not square nor do they present even surfaces (especially not in older buildings) and may be flexible themselves.
• Flexible solar panels could be easier to transport and install, particularly in building integrated PV applications such as roofing and window laminates.
• Perhaps the biggest advantage of the BIPV sector from the perspective of the flexible substrates business is that, however bad the next 12 months may be for solar, flexible BIPV is a here-and-now product. Flexible BIPV may be a niche-like product, but it is real. The same cannot be said about flexible displays.
The bottom line here is that for years to come, PV will represent by far the largest potential flexible substrate market by volume and one of the most demanding. PV devices are used outdoors, often in extreme climates, and are expected to last for 20 years or more. While crystalline silicon is a robust material in itself, thin film and organic PV technologies are especially dependent on substrate quality.
Of course, it is only certain kinds of PV that can ever be flexible:
• The PV industry remains dominated by the conventional technology which uses crystalline silicon as both an absorber layer and a substrate. Although there are some R&D efforts directed towards creating flexible silicon substrates, none of them have made their mark on the conventional PV industry as yet, and there are few materials that are less flexible than crystalline silicon.
• With this situation in mind, flexible BIPV mostly involves either (inorganic) thin-film PV (TFPV), organic PV (OPV) or dye-sensitized cells (DSC).
• However, OPV and DSC have arguably been the two PV technologies that have had the most difficulty in developing high-volume commercial markets. They simply can’t match the conversion efficiency and durability of crystalline silicon or inorganic thin-film PV; although there is still a large community of interest that thinks these PV technologies will in time. But for now, this sector of the PV/BIPV market would seem to offer limited opportunities for flexible substrates, although from a technical point of view the OPV/DSC absorber layer is inherently flexible.
• Within the TFPV space, the conversion efficiencies are much better than for OPV/DSC, and the thin-film nature of TFPV implies flexibility to a large degree. CIGS appears to be the TFPV material with the greatest potential for flexible BIPV. Nonetheless, glass remains by far the most frequently used substrate material for TFPV in general.