Rigid Module Encapsulation Opportunities
The near-term market for rigid BIPV encapsulation will be dominated by the same materials as many rigid modules of today, namely glass. Glass will continue to be the king for the foreseeable future. Compared to other options, it is inexpensive, provides a hermetic seal and thick tempered modules are robust to weather and wear.
Current rigid module encapsulation comes in two flavors.
• The first is very similar to rigid panels for rooftop or solar farm applications. These modules, in many cases, amount to more robust adaptations of current module designs with heavier glass and more robust edge seal designs to meet 20-30 year lifetime specs for BIPV applications.
• The second is transparent a-Si modules that have had some penetration in skylight and window applications, but have been hampered by the low efficiency of a-Si absorbers.
Rigid BIPV modules in general have been limited by several constraints.
• For façade applications, the rigid nature limits their use to flat surfaces.
• The weight of rigid tempered glass-based cells can be up to 30 kg/m2. Extra weight equals extra cost for integrating such modules.
• Less of a factor is the uniform rectangular module size and framing, which limits their ability to cover a surface in an inconspicuous manner.
• Efficiency can also be an issue with c-Si and polysilicon based modules. While such modules are very efficient in solar farm applications with direct sunlight, the efficiency drops off precipitously in BIPV applications when the majority of incoming light is reflected.
While current semi-transparent a-Si BIPV modules are of low efficiency, there may be an opportunity for growth for encapsulation and substrate providers if a suitable transparent substrate and rear conductor can be found that would allow the transition of BIPV transparent modules from a-Si to CIGS.
Currently, most CIGS modules have molybdenum as the back conductor. Highly conducting optically transparent films containing carbon nanotubes, metal dispersions and extremely narrow metal grids have been explored for such applications, and may represent significant opportunities going forward if they can be integrated into transparent BIPV CIGS modules.