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Encapsulating Materials and Associated Devices

National Renewable Energy Laboratory

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Technology Marketing Summary

Encapsulant materials are used in a variety of applications to isolate components, areas, or other materials from potentially stressful conditions that can adversely affect the performance of a device. For example, the performance of photovoltaic (PV) modules may decrease over time as water penetrates the module and corrodes the metallic components essential for module function. In the absence of water, corrosion occurs relatively slowly because by-products are less able to diffuse away from a surface to allow the corrosion process to progress. Furthermore, water is known to help catalyze some oxidative reactions.

The PV industry has long-recognized the dramatic effect that corrosion has on module performance. Today, PV modules typically include a polymeric encapsulant material to isolate the silicon components from the ever-present potentially adverse conditions created by various sources of water, including rain, snow, and condensation. The isolation created by the encapsulant protects the PV components from the potential for corrosion and provides additional benefits including mechanical support, electrical insulation and protection from mechanical damage.

Polymeric encapsulants provide the desired isolation by bonding to a surface and limiting access to the protected areas and/or components. For example, encapsulants used in PV modules are typically bonded to one or more glass sheets to isolate the solar cells, or cell strings, from water in the module’s environment. The ability of a polymeric material to protect a surface is thus highly dependent on its ability to bond to a surface and limit access to corrosion sites. Therefore, a strong correlation exists between corrosion protection and adhesive strength.

The dominant encapsulant currently used in the PV industry is ethylene vinyl acetate (EVA). However, despite recent improvement, EVA still has several drawbacks that affect its performance as an encapsulant material, particularly in PV modules. For example, EVA suffers from non-ideal mechanical and thermal properties, a high diffusivity for water, and acetic acid by-product production. Furthermore, the newer thin-film technologies that are rapidly being developed in the PV industry may be more sensitive to the shortcomings of EVA. As crystalline silicon wafers become thinner, the mechanical properties of EVA may also prove insufficient. Scientists at NREL have developed a novel approach to improve efficiencies in the module manufacturing process and overall module cost.

Description

NREL scientists have developed and tested various compositions suitable for use as encapsulants. These compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as PV modules.

Benefits

·        Reduced cost

·        Increased chemical stability

·        Good electrical insulation

·        Low glass transition temperature leading to more predictable behavior under extreme conditions

·        Low moisture permeation rates leading to reduced moisture ingress in PV modules with glass on the front and back

·        Improved adhesion of the encapsulant bonding to a surface leading to better exclusion of moisture

·        Improved resistance to photooxidative degradation

·        Reduced UV degradation 

Applications and Industries

·        Devices in which a substantial blocking of moisture ingress is desired, such as PV modules

Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 8,183,329
Patent
8,183,329
Encapsulant materials and associated devices
Compositions suitable for use as encapsulants are described. The inventive compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as photovoltaic (PV) modules.
National Renewable Energy Laboratory 05/22/2012
Issued
Patent 7,902,301
Patent
7,902,301
Encapsulant materials and associated devices
Compositions suitable for use as encapsulants are described. The inventive compositions include a high molecular weight polymeric material, a curing agent, an inorganic compound, and a coupling agent. Optional elements include adhesion promoting agents, colorants, antioxidants, and UV absorbers. The compositions have desirable diffusivity properties, making them suitable for use in devices in which a substantial blocking of moisture ingress is desired, such as photovoltaic (PV) modules.
National Renewable Energy Laboratory 03/08/2011
Issued
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 06-13ProposedAvailable02/27/201502/27/2015

Contact NREL About This Technology

To: Bill Hadley<Bill.Hadley@nrel.gov>