Review of world experience and properties of materials for encapsulation of terrestrial photovoltaic arrays. Final report

Abstract

Available information defining the state of the art of encapsulation materials and processes for terrestrial photovoltaic devices and related applications were collected and analyzed. Based on criteria of properties, processability, availability, and cost, candidate materials were identified which have potential for use in encapsulation systems for low-cost, long-life terrestrial photovoltaic arrays manufactured by automated, high-volume processes. The study was in support of the Encapsulation Task of the ERDA Low-Cost Silicon Solar Array (LSSA) Project, managed by JPL. The criteria for consideration of the encapsulation systems were based on the LSSA goals for arrays with a lifetime of over 20 years high reliability, an efficiency greater than 10 percent, a total array price less than $500/kW, and a production capacity of 5 x 10-> kW/yr. Published and unpublished information relating to encapsulation systems and materials properties was collected by searching the literature and appropriate data bases (over 1300 documents were selected and reviewed) and by personal contacts including site and company visits. A data tabulation summarizing World experience with terrestrial photovoltaic arrays (50 installations) is presented in the report. None of the encapsulation materials used meets all of the LSSA criteria (particularly cost), but some have performed well. R. B. Bennett. F. A. Sliemers led the polymer-chemist effort with contributions from R. E. Sharpe, G. P. Nance, and A. R. Bunk. R. D. Igou led the information searching and retrieval efforts. E. L. Briich managed the information system for the study and J. J. Breslin helped with the reporting; their assistance is certainly appreciated.

Reactions at the silver/polymer interface: A review

“…Accelerated expasure tests at Phoenix also gave negligible degradation. However, similar tests at St Experience with polymers in this application has been quite varied and delamination and moisture permeation have been major sources of failure [11]. Similarly, materials for spac&-flight application are potentially useful in solar applications.…”

“…of synthesis methods is avaiiable•[47] • A.summary. [ll] of the mate-Although TFE is not of direct interest because of the present difficulty of processing, a data summary is included as a guide to the behavior of the other materials.In contrast to the dearth of scientific papers, there is considerable practical literature, particularly regarding encapsulating solar cells[11]. Because these materials have such outstanding qualities, the emphasis has been on the processing and particularly the bonding of the materials to substrates.…”

Reactions at the Silver/Polymer Interface: A Review

“…Experience with polymers in this application has been quite varied and delamination and moisture permeation have been major sources of failure [11]. Similarly, materials for spac&-flight application are potentially useful in solar applications.…”

“…Two alternatives have been documented. First, it has been observed that the permeability of Teflon-FEP can increase forty-fold during processing .subsequent to manufacture [11]. For some polymers, weathering can cause surface microcracks which, as they propagate into the bulk, could increase permeability.…”

“…In contrast to the dearth of scientific papers, there is considerable practical literature, particularly regarding encapsulating solar cells [11]. Because these materials have such outstanding qualities, the emphasis has been on the processing and particularly the bonding of the materials to substrates.…”