成果報告書詳細
管理番号20130000000657
タイトル*平成24年度中間年報 太陽エネルギー技術研究開発 太陽光発電システム次世代高性能技術の開発 次世代長寿命太陽電池モジュールの研究開発(1)
公開日2014/5/9
報告書年度2012 - 2012
委託先名日清紡ホールディングス株式会社
プロジェクト番号P07015
部署名新エネルギー部
和文要約
英文要約Title: Research and Development for Next Generation Long-life PV Modules, Capable of Withstanding Extreme Environmental Stresses (FY2012-FY2013) FY2012 Annual Report

Construction of solar power generation stations is gaining momentum due to the FIT Program that started on July 1st, 2012. On the other hand, stations in the EU have reported PID (Potential Induced Degradation) phenomenon that significantly lowers output in only a few years. One way to evade the PID phenomenon is to use transformer-based inverters, but they cause a drop in efficiency and are expensive, thus a solution at the source is being sought. This is a project for module materials more resistant to PID even in high system voltage environments such as large scale facilities using transformer-less inverters. The R&D of casing technology that lasts more than 20 years without the occurrence of PID will be used to realize next generation long-lasting PV modules. We also investigate the mechanism behind PID, acceleration test conditions for high accuracy PID prediction, and use of those conditions for verifying the performance of these modules. In designing olefinic rubber as an encapsulant, the optimal amount of fine grained silica, organic peroxide crosslinking agent and silane coupling agent added to olefinic rubber was investigated. Transparent olefinic rubber with a sheet hardness of (JIS A) 56, crosslinking density of 8.4×10^19 links/cc, and 88% transparency (2mm sheet of olefinic rubber) was achieved. It was bonded to a 1mm sheet of COC resin, and processed at 150°C for 5, 10 and 15 minutes. A warm water immersion test was performed, as well as an adhesion test that resulted in the destruction of base material that was processed for 10 minutes or more. Using the above material as a base and combining it with a UV protection agent, phenol inhibitor, and phosphorus inhibitor, the establishment of a formula with more than 20 years of light resistance is being reviewed. An investigation of the use of a rubber calendar to laminate it with 75μm PET release sheets resulted in olefinic rubber with a 4.6×10^3 Pa*sec melt viscosity. It was possible to produce a uniform sheet, but sheet making is not possible at lower viscosities. Using the laminated sheet, we developed a process for layering the transparent olefinic rubber sheet on top of the COC resin sheet during the layup process by peeling off the double sided release sheet. We investigated the following module structures in response to penetration of moisture and salts to silicon cell surroundings and release of sodium ions from glass, considered the cause of the PID phenomenon; Transparent olefinic material, highly resistant to moisture and salt penetration, to encapsulate silicon cells; COC resin sheet for isolation, to prevent dispersion of sodium ions from soda-lime glass to the cell surface; chemically tempered glass, which releases very few sodium ions. To verify the proposed structure, a PID test was performed on a 32 cell module was prototype, passing conditions set by the Fraunhofer Institute. Polycrystalline modules that developed symptoms of PID in the field were destructively analyzed. Affected cells had significantly smaller fingers than unaffected by PID, and particles were found dispersed over the cell surface. A correlation was found between output drops of aged modules (3-23 years) and amount of acetic acid from EVA encapsulant degradation. We hypothesized that bonds of fingers and tab ribbons to cells are broken by the acid, and increased area is related to output degradation. Using the amount of acetic aced from EVA encapsulant degradation as an index, we are considering laboratory accelerated ageing test conditions that correspond to 20 years in the field.
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