Behind Dow Corning, Reis Robotics’ liquid PV encapsulant process

Dow Corning and Reis Robotics recently announced a jointly developed solar cell liquid encapsulation process. Eric Peeters, VP, Dow Corning Solar Business, discusses the materials properties and processing step that make this encapsulation method special.

August 30, 2011 — Dow Corning, along with Reis Robotics, recently announced a jointly developed solar cell liquid encapsulation process, which is now available for commercial use. The new technology enables solar panel manufacturers to use Dow Corning’s PV-6100 cell encapsulant series and Reis’ equipment to achieve higher production rates for crystalline and amorphous silicon thin-film modules, reducing the cost per kilowatt-hour of solar power.

According to Eric Peeters, VP, Dow Corning Solar Business, the materials series relies on the UV stability of the silicone molecule to achieve durability and increased efficiency. In a podcast interview with PVW, Peeters explained that UV-stability is an intrinsic property of silicones — preventing yellowing and cracking with age seen in some organic plastics. Additional chemicals are not needed (for protection against UV radiation) so this enables UV light to come through the silicone and reach the solar cells without inhibition, increasing efficiency.

Figure 1. The Dow Corning PV-6100 Encapsulant Series was compared to EVA encapsulant using 72-cell multicrystalline cells in damp heat aging. The Dow Corning PV-6100 Encapsulant Series and EVA compare well at the IEC-required 1000 hours damp heat. Dow Corning PV-6100 continues to meet IEC performance requirements at >8000 hours of damp heat, where EVA encapsulated cells exceed the 5% maximum degradation limit as early as 3000 hours.

Peeters describes how the liquid encapsulation process provides a clear laminate to protect each solar cell in a panel. Panel manufacturers can increase efficiency and reduce total cost-of-ownership through lower processing temperatures, and faster throughput. “Because of the chemistry of the system, the cure is very rapid — and the assembly as well — so at the end we achieve a total cycle time of <90s,” said Peeters. “That would not be possible with just the material alone — we had to fine tune, together with Reis, the different steps in that process to achieve that very low cycle time.” The process temperature used to cure the material is around 100°C. This low temperature means less stress on the cells and leads. The low temperature, together with the low cycle time (the temperature is applied for less time than in the traditional process), translates to lower capital and less factory space because of the higher throughput, explained Peeters.

Figure 2. EVA blocks more light than Dow Corning PV-6100 encapsulant, which captures up to 3% more light. Dow Corning PV-6100 Cell Encapsulant does not absorb UV light. Data from Dow Corning shows that the increase in transparency translates to an increase in efficiency and performance of monocrystalline and multicrystalline silicone modules.

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