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TechWaTch Material Trends for BIPV Glass By Robert Nolan
n order to move beyond a niche product, building-integrated pho- tovoltaics (BIPV) will need to demonstrate both improved efficien- cy and lower cost. NanoMarkets be- lieves that BIPV should be able to benefit from the growth that we ex- pect to see in the PV market as a whole, but the degree to which it suc- ceeds will likely depend on advances in technology and choice of PV mate- rials. This may require switching to improved or completely different ma- terials than what is commonly used today.
I Our latest report on BIPV glass,
“BIPV Glass Markets — 2014 and Be- yond,” describes PV technologies being used for this application today and an- alyzes which materials are likely to gain market share in the future.
Crystalline Silicon PV The dominant form of BIPV
glass consists of walls of window panes, some of which are crystalline silicon (c-Si) PV panels, and some of which are transparent glass. Be- cause c-Si panels are not transpar- ent, this is really the only way to in- corporate it into BIPV glass today. This is a very low form of integration,
but c-Si continues to dominate the BIPV market.
NanoMarkets believes that de-
spite the drawbacks of c-Si, it will re- main dominant through the end of the decade. It remains the incumbent PV technology for all applications and has the highest efficiency. Mod- ule prices have fallen, spurring growth in all sectors that use c-Si panels. Improvements in c-Si tech- nology will also support its continued use in BIPV glass. According to the forecasts in our recent report, c-Si is expected to lose market share over the forecast period but still retain 75 percent of the addressable market. Despite advances in c-Si tech-
nology, it still has some significant drawbacks as a BIPV material that go beyond the lack of transparency. One issue is esthetics; many people believe that c-Si panels are ugly, and they often don’t blend in well with the rest of the building. Performance in situations of in-
direct or diffuse light is a serious problem because c-Si modules show limited capacity in converting dif- fused solar irradiation to energy. Shadows naturally fall onto building walls throughout the day, which can
lead to loss of power in a shaded c-Si module that extends to all modules connected in series within the same circuit.
Thin Film PV Options Thin film PV technologies may
be able to pave the way toward cheaper BIPV glass, which will be needed in order for BIPV to break in- to the growing market for zero net energy buildings. TFPV cells offer lighter weight compared to c-Si and many have the advantage of per- forming equally well in direct sun- light and in shaded environments. This is especially important for ap- plications where BIPV is integrated into building walls rather than sky- lights.
TFPV technologies are for the
most part not mature today, but as the solar sector starts to offer sus- tained growth, NanoMarkets sees po- tential for BIPV glass firms to move away from c-Si. They have several options that are compelling, but all have their inherent risks as well. CIGS. Many CIGS (Copper indi-
um gallium selenide) firms disap- peared during the solar bust, but some of those who remain are specif- ically targeting BIPV glass. For ex- ample, Manz is involved with BIPV glass and has produced specialty modules with flexibility, color, and design meant to suit the tastes of ar- chitects. CIGS is flexible, which al- lows it to be used on curved building facades, and its high efficiency makes it attractive. NanoMarkets expects CIGS firms to edge their way into the BIPV glass space over the next few years. CdTe. The CdTe market re-
mains dominated by First Solar who hasn’t expressed interest in BIPV. That said, CdTe has good efficiency, and third parties use CdTe cells from First Solar in BIPV applications, which should help speed up commer- cialization. CdTe is the only thin-film photovoltaic technology that has sur- passed c-Si PV in terms of overall low system cost in multi-kilowatt sys- tems, which gives it a major advan- tage for BIPV. It does, however, have disadvantages in terms of trans- parency and the toxicity of cadmium. NanoMarkets believes that these limitations will mean a delay of sev- eral years before CdTe emerges as a competitive technology for BIPV glass applications.l DSC. Dye-Sensitized cells (DSC)
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can be solution processed on a glass substrate, making them very suit- able for BIPV glass. In addition, they are quite good when it comes to per- formance in environments with indi- rect or diffuse light, and DSC glass can vary in color and transparency, making it very attractive for the BIPV market. Several firms are pur- suing DSC for BIPV applications, but currently high prices and limited long-term stability are bottlenecks that make large-scale commercializa-
tion a challenge. Current use is lim- ited to trials and pilot production. Until price and reliability improve, that is unlikely to change, but ongo- ing research and recent investments in this area may yield results that can accelerate commercialization. OPV. The properties of DSC
that make it appealing for BIPV glass also apply to organic PV. Com- pared to technologies such as CdTe, it is a much “greener” option, which should appeal to those aiming for ze- ro net energy buildings. OPV cells contain no toxic compounds and are potentially disposable and recycla- ble. Efficiency is currently not great, but it is improving, and will need to continue to do so in order to gain more widespread interest. Heliatek is on the forefront of improving OPV efficiency, and its joint development agreement with AGC Glass Europe is encouraging. Still, OPV is unlikely to resolve efficiency and product dura- bility issues quickly, making it more of a long-term option. Amorphous silicon. Amor-
phous silicon (a-Si) was the original TFPV and is a lower cost alternative to c-Si. It is flexible, which is an ad- vantage for curved glass structures. Still, other technologies, such as CIGS, can also claim this benefit and may be more compelling because of higher efficiency. Low performance would appear to make a-Si less desir- able than other options, but many Chinese companies are still in this market, keeping it alive, and future product evolution is likely to spur modest growth in the coming years.
Challenges for Metal Mesh One of the selling points of
BIPV compared to traditional rooftop PV panels is esthetics, so adding col- or to the glass — so long as it doesn’t adversely affect transparency — is one way BIPV glass suppliers can differentiate themselves in the mar- ket and make their products more appealing to building designers. This feature is especially compelling for BIPV glass facades in buildings and may be able to expand the address- able market.
NanoMarkets expects the BIPV
glass market to grow over the next eight years, from just over $800 mil- lion in 2014 to around $4.6 billion by 2021. This growth assumes advances in all types of BIPV glass and price reductions that make it appealing to the mass market. This will allow BIPV glass to be used not only in prestige buildings, which currently constitute the largest sources of rev- enue for BIPV glass, but also in net zero energy buildings, which is a much larger market and should pro- vide a greater source of revenue in
the long term. Contact: NanoMarkets,
PO Box 3840, Glen Allen, VA 23058 % 804-938-0030 E-mail:
sales@nanomarkets.net Web:
www.nanomarkets.net r
July, 2014
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