But the big question is whether improving BIPV glass in this way really makes that much difference in the sense that customers are really in search of transparency. If this is the case then product strategies aimed at improving transparency without too much cost in terms of either money or efficiency will be important. However, NanoMarkets believes that the jury is still out on this matter:
· On the one hand, it seems to be common sense that significantly more opportunities would arise, if BIPV glass would achieve a transparency that is much closer to that of window/vision glass, even though BIPV glass may never be chosen where one wants to provide visual access to some beautiful scene.
· On the other hand, many of the applications in which BIPV glass is currently used do not seem to be crying out for a lot more transparency. In any case, there are limits on what can be achieved in terms of transparency because PV panels are inherently absorbent. And while the sunlight could be transported from the window or other glass building material to a somewhat remote PV panel, this could not be done easily without lowering the efficiency of the panel or even maintaining a reasonable claim that the term "integrated" applies.
However, to better exploit the opportunities that do occur for BIPV glass firms to compete on transparency, we note that there currently appear to be three classes of product strategies:
· The standard strategy is to create BIPV glass panels by simply glazing together small opaque solar panels and window glass in a kind of mosaic; if the cells cover (say) 50 percent of a surface, then the BIPV glass panel will be 50 percent transparent. This has the advantage that it is a purely mechanical form of integration that can be accomplished through local glazing
· Special forms of optical devices can be deployed that enable BIPV glass panels to be built that are not blocked by PV cells. Pythagoras' prisms are the most obvious example of what could become a broader class of technologies
· Or newer, more transparent PV absorbent materials can be used. Most BIPV glass today uses crystalline silicon absorber layers which are inherently opaque. Better transparency could be achieved at a reasonable level of efficiency using other absorber layers such as very thin layers of CIGS or dye sensitive cells.