VENDORVIEW
W
hat has been learnt from past experience is that relying on
customary encapsulants for protecting thin-film cells is simply not enough. This becomes particularly significant when observing the long term effects on modules.
The introduction of butyl as desiccated edge sealant has shown immense benefits compared with traditional module assembly. But what are the benefits that justify this additional process step? There are several points that are interconnected. The overall objective is better encapsulation properties of the module. This brings about improved cell protection, prevention of corrosion thanks to prevention of moisture vapor ingress. It may be stressed that butyl has a very low water vapor and gas permeability, significantly more favourable than with EVA or PVB.
Most welcome side-effects of improved encapsulation are improved product safety and increased module performance. Naturally, the edge-sealant reduces encapsulant size and thus material use.
All these points add up to extended module life. The TFPV process chain
Edge-sealant can be applied onto the substrate or a top glass, if applicable. The surface must be properly cleaned. Field experience has shown that substrates that underwent edge deletion by laser have excellent properties for superb edge- sealing with butyl which leads to outstanding adhesion.
Put in specific work sequences, this calls for an individual station prior to module marriage with back glass or back sheet, respectively.
First introduced had been butyl tapes. Customary approaches are workstations for manual tape application or some sort of automated tape applicators (e.g. end-of-arm robot tools). However, certain pitfalls cannot be neglected.
Among those drawbacks are labour-intensity, small lots, preliminary stage preparation (i.e. extruding and liner application), complex storage, and frequent changeovers, to name the most obvious.
This is what has led to promote bulk butyl for automated edge-sealing. This is based on using ready-to-use bulk material that is dispensed onto a substrate or top glass.
There are a few global vendors that have brought bulk butyl to market. Typical lot sizes are drums of some 200l [55 gal.]. The bulk material is melted at a temperature level of 140-150°C [284-302°F] and continuously fed to a dispenser.
Bulk butyl benefit
Bulk butyl in drum packaging yields better butyl utilization and allows more economic storage. On the one hand, is slashes one preparatory production step for extruding and tailoring butyl tape. On the other hand, it results in less butyl and liner scrap. The material cost savings are obvious. One credible industry source stated that the cost savings for edge-sealant on each module can
The
introduction of butyl as desiccated edge sealant has shown immense benefits compared with
traditional module assembly
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www.solar-pv-management.com Issue IV 2011
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