Module encapsulation

Reliable stability data of the p-i-n solar cell itself are not easily obtained, especially for non-encapsulated cells or modules. One of these tests e.g. for EN/IEC 61646 certification of modules is the so-called damp-heat test (85°C, 85% humidity, up to lOOOh). Recent studies were performed by Stiebig et al. [50, 51] exposing different types of cells to harsh conditions. One of the most important results was the excellent stability of silicon thin film solar cells. Remarkably, this is also valid for small area modules even without encapsulation [52]. This is of high interest because costs and efforts for module encapsulation strongly depend on the inherent stability of the solar cells. As a more detailed treatment of this subject is beyond the scope of this chapter, the reader is referred to the original papers [50,51]. 

Functional vs. data abstraction Functional abstraction refers to the case where a module has some kind of transformation/coordination character. Hence, an interface resource transforms some kind of input data into corresponding output data, or the component coordinates the resources of lower components. Functional abstraction facilitates the hiding of algorithmic details of this transformation/coordination. In contrast, data abstraction is present if the module encapsulates the access to some kind of memory or state . Then, the module hides the realization of the data representation. The module s interface only shows how the data can be used, not how it is mapped onto the underlying storage. 

Photovoltaic Module Encapsulation Design and Materials Selection, prepared and edited by the FSA Environmental Isolation Task, FSA Project Report 5101-177, JPL, Pasadena, California, August 15, 1981. 

Photovoltaic Module Encapsulation Design and Material Selection, JPL Document NO. 5101-177 (in press). (JPL Publication STTro, DOE/JPL 1012-60). 

Agroui, K., Belghachi, A., Collins, G., Farenc, J. Quality control of EVA during photovoltaic module encapsulation process. Desalination 209, 1-9 (2007)... 

There is a notable difference between the results obtained with the two backseals. The modules encapsulated with silicone rubber show a constant sigma ( 0.9) independent of the bias, whiie those encapsulated with epoxy have a sigma ranging from 0.7 to 2.5, increasing as the bias falls from 20 to 5 volts so that, at low fallout, the cumulative percentage of failures is practically independent on the applied voltage. 

Thermosetting-encapsulation compounds, based on epoxy resins (qv) or, in some niche appHcations, organosiHcon polymers, are widely used to encase electronic devices. Polyurethanes, polyimides, and polyesters are used to encase modules and hybrids intended for use under low temperature, low humidity conditions. Modified polyimides have the advantages of thermal and moisture stabiHty, low coefficients of thermal expansion, and high material purity. Thermoplastics are rarely used for PEMs, because they are low in purity, requHe unacceptably high temperature and pressure processing conditions. 

Zentner and coworkers [24,26] utilized this information in their development of a system that releases this drug over a 24 hr period. The use of NaCl to modulate the release of diltiazem presents an interesting problem in that the concentration of the solubility modifier must be maintained within certain limits and below its saturation solubility within the device. To solve this problem, core formulations were developed that contained both free and encapsulated NaCl. The encapsulated NaCl was prepared by placing a microporous coating of cellulose acetate butyrate containing 20 wt% sorbitol onto sieved NaCl crystals. The coated granules released NaCl over 12-14 hr period via an osmotic mechanism into either water or the core tablet formulation. The in vitro release profile for tablets (core I devices) containing 360 mg of diltiazem HC1 and 100 mg of NaCl equally divided between the immediate release and controlled release fractions... 

In general, biomolecules such as proteins and enzymes display sophisticated recognition abilities but their commercial viability is often hampered by their fragile structure and lack of long term stability under processing conditions [69]. These problems can be partially overcome by immobilization of the biomolecules on various supports, which provide enhanced stability, repetitive and continuous use, potential modulation of catalytic properties, and prevention of microbial contaminations. Sol-gel and synthetic polymer-based routes for biomolecule encapsulation have been studied extensively and are now well established [70-72]. Current research is also concerned with improving the stability of the immobilized biomolecules, notably enzymes, to increase the scope for exploitation in various... 

Covalent attachment of antibody molecules to liposomes can provide a targeting capacity to the vesicle that can modulate its binding to specific antigenic determinants on cells or to molecules in solution. Antibody-bearing liposomes may possess encapsulated components that can be used for detection or therapy (Figure 22.17). For instance, fluorescent molecules encapsulated within antibody-targeted vesicles can be used as imaging tools or in flow cytometry... 

Cells are then individually sorted and classified according to their illuminated electrical parameters and are electrically interconnected in strings, which are then encapsulated to form a module, which is designed to be weather proof and produce electrical output for more than 25 years. 

Hollow fiber modules and the micro encapsulation of progenitor cells have been used in hematopoietic culture with less success [69, 70]. Furthermore, these approaches do not fit the chnical requirements, as the harvest of the cells is almost impossible. 

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