Photovoltaic cell modules encapsulation materials

Most of the chapters in the third section are concerned with photovoltaic (PV) applications (conversion of light into electrical energy). Because of the diffuse nature of solar energy, the photovoltaic collection devices must be very large or else the light that strikes them must be concentrated. The first chapter in this section gives an overview of luminescent solar concentrators that can be used with the PV collectors. Most PV collectors or modules are multilayered systems containing a photovoltaic cell element. The next four chapters consider the use of various plastics as encapsulant or pottant materials in the PV modules. 

One important application of EVA (Ethylene Vinyl Acetate) material is the encapsulation of solar cells in photovoltaic (PV) modules, where the material has to fulfill several basic functions. Unfortunately, the lEC standard does not provide any information on the changes in the internal stmcture of the EVA encapsulant material as a consequence of encapsulation process or environmental exposure. 

Encapsulants are necessary for electrical Isolation of the photovoltaic circuit. They also provide mechanical protection for the solar cell wafers and corrosion protection for the metal contacts and circuit interconnect system over the 20-year design life of a photovoltaic array. The required components Include the solar cell circuit, the rigid or structural member, the pottant, and the outer cover/insulator. Surface modifications may be needed to develop strong, stable bonds at the Interfaces in the composite. If the module is to be framed, edge sealants may also be required. The functions of the Individual components and the performance requirements as they are now known are described. Costs are ccmipared where possible and candidate materials identified. 

A few years ago, most terrestrial photovoltaic (PV) modules were assembled by casting the cells in a transparent silicone substance, using a metal substrate for support. When this approach was reviewed by the Flat-Plate Solar Array Project (FSA), development was begun on new materials that would reduce the cost and quantity of material required for encapsulation. 

So far the physical realization of the heterojunction and its optimization in photovoltaic efficiency have been discussed. The production process of a photovoltaic generator and its economical use have to satisfy a momber of additional criteria which involve a) technological procedures for economic cell and module fabrication allowing large scale production and b) material evaluation for substrates, contacts and encapsulation. These criteria result in a variety of fabrication methods, structures of cells and modules, and materials. 

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