Glass-glass PV modules are becoming increasingly common in the solar marketplace. With longer lifetimes provided by the robust glass encapsulation on front and back, longer warranties are being provided and producers claim that BoS costs can been reduced. The development of cost-competitive thin solar glass for encapsulation is one of the factors facilitating the rollout of glass-glass modules.
But while this is the case, dual-glass modules still remain in the minority and somewhat of a niche product. Chinese firm BYD plans to turn this situation on its head, claiming that the cost reduction potential of its 430 silica gel glass-glass module means that it is likely to do away with conventional module production in the future.
I dont want to produce traditional modules anymore, BYDs Tom Zhao told pv magazine. This is because with traditional modules there is no further chance for cost reductions. Zhao says that cost reductions can be achieved because its 430 silica gel module is frameless, that one process step and material cost can be removed. Reducing silver usage is also a cost reduction lever targeted by BYD production of the module.
Additionally to the cost reduction advantages, Zhao says that improvement in module performance, reduced PID and improved BoS costs all result in a reduced cost/Watt of the glass-glass product.
The most important thing is that this module is not only reducing the cost f the module itself, but also it is the first module that reaches high voltage to 1500V DC, and it is the first module of its type in the market now. Zhao added that the use of a silicone glue rather than EVA reduces the likelihood for PID and also helps to deliver the higher wattage performance.
With silicone glue there is no PID caused by consistent UV radiation. With EVA there is a carbon-carbon bond inside so the bond energy is about 325 EV, but the UV energy is 375 EV, so UV energy is higher than the carbon-carbon bond. So it will break the carbon, which results in the degradation of the EVA.
With silicone there is no break in the silicone/oxygen bond. The bond is 425, which is higher than the UV energy so there is no change for degradation. So we call the dual glass module BYD the full silicon module: glass is silicon, bond is silicon, cell is silicon. And the full silicon is very stable.
In terms of BYDs transition from a traditional module production to 100% glass-glass, Zhao was a little more circumspect and was unwilling to announce a timeframe for the move. The company reports a manufacturing capacity of 1 GW in 2014, doubling to 2 GW this year and then 3 GW in 2016.
We have the strong confidence to go 100% glass-glass because the cost advantage is very significant and as the volume of production goes up the cost comes down even lower, said Zhao. BYDs 430 module is currently produced with 3.2 mm front and back glass, however this can be reduced to 2mm to reduce module weight.