Wide optimum design

Figure 7-8 Narrow Optimum Design Figure 7-9 Wide Optimum Design...

Thin solar cells are therefore much more stable than thick ones. On the other hand the initial efficiency of the thicker cells is larger because more of the solar spectrum is absorbed. The optimum design is a compromise between these two effects and the typical thickness used is about 0.5 pm. Tandem or triple cells are more efficient at absorbing over a wide spectral range because each cell is designed to cover a... 

Although rigorous computer methods are available for solving multicomponent separation problems, approximate methods continue to be used in practice for various purposes, including preliminary design, parametric studies to establish optimum design conditions, and process synthesis studies to determine optimal separation sequences (Seader and Henley, 2006). A widely used approximate method is commonly referred to as the Fenske-Underwood-Gilliland (FUG) method. 

Figure 4.9 Comparison of average thickness (solid lines) and buckling strains (dashed) for straight fibre optimum designs and variable fibre angle designs obtained using continuous tow shearing and automated fibre placement. In all cases, the panels are 250 mm wide and 750 mm long with simple supports.

The final section discusses a generalization of the theory to encompass models of distributed rather than point systems, to include the usual models of nuclear reactor statics. Besides the attraction of providing a more general (if correspondingly weaker) theory, this enables us to specialize the theory to obtain some results in reactor statics on the optimum design of systems. Where these results are already known, they illustrate the wide power of the optimum control theorem in encompassing a range of problems in a consistent, unified way. 

In summary, therefore, perturbation theory has shown some interesting advances in recent years and offers prospects of even further useful development in the realm of nonlinear theory and optimum design. Coupled with this, one would plead for a closer integration of perturbation methods in reactor computations. It cannot be doubted that perturbation theory offers powerful methods in a wide range of problems and that future years will see equally interesting advances. 

Second law analysis has been widely used in the last several decades by many researchers. Exergy analysis usually predicts the thermodynamic performance of an energy system and the efficiency of the system components by accurately quantifying the entropy generation of the components [1]. Furthermore, exergoeconomic analysis estimates the unit cost of products such as electricity, steam and quantifies monetary loss due to irreversibility. Also, this analysis provides a tool for the optimum design and operation of complex thermal systems [1], [2], [3]. 

When such a map has been constructed, it can be used to select semiconductors of different bandgap, but the same lattice constant, so that the lattice matching which is so desirable in a heterojunction can be made between a specified wide bandgap window semiconductor and a series of photovoltaically active alloy semiconductors. For example. Fig. 10 shows the iso-lattice constant line with a lattice constant value equal to that of CdS (5.82 eV). The bandgaps of semiconductors which have this lattice constant range from about 1.06 eV to 1.80 eV this range makes the Cu-Ag-In-S-Se alloy system an attractive possible source of materials to be used in solar cells of tandem systems. A description of experiments on this and other ternary alloy systems is the subject of another section of this chapter. However, before we return to that matter we shall first consider optimum design of individual cells for incorporation into the system. 

Since the first commercial application of the Haber process for ammonia production in 1913, a wide variety of synthesis loop designs have been developed. A history of the early developments is given in Chapter 1, and has also been reviewed elsewhere. However, by the 1950s and early 1960s, a broad consensus about the optimum design conditions for an ammonia synthesis loop had been reached. A typical design from this period will be described. This will be used to demonstrate how the elements of the synthesis loop are applied to produce a practical design, and will also serve as a base case for the discussion of modern developments. A flowsheet for this type of synthesis loop is shown in Fig. 7.4. 

The process gas of ethylene plants and methyl tertiary butyl ether plants is normally a hydrogen/ methane mixture. The molecular weight of the gas in such processes ranges from 3.5 to 14. The tliermodynamic behavior of hydrogen/methane mixtures has been and continues to be extensively researched. The gas dynamic design of turboexpanders, which are extensively used in such plants, depends on the equations of state of the process gas. Optimum performance of the turboexpander and associated equipment demands accurate thermodynamic properties for a wide range of process gas conditions. 

Due to the wide variety of filter media, filter designs, suspension properties, conditions for separation and cost, selection of the optimum filter medium is complex. Filter media selection should be guided by the following rule a filter medium must incorporate a maximum size of pores while at the same time providing a sufficiently pure filtrate. Fulfilment of this rule invokes difficulties because the increase or decrease in pore size acts in opposite ways on the filtration rate and solids retention capacity. 

Method development is important. LC-MS performance, probably more than any other technique involving organic mass spectrometry, is dependent upon a range of experimental parameters, the relationship between which is often complex. While it is possible (but not always so) that conditions may be chosen fairly readily to allow the analysis of simple mixtures to be carried out successfully, the widely variable ionization efficiency of compounds with differing structures often makes obtaining optimum performance for the study of all components of a complex mixture difficult. In such cases, the use of experimental design should be seriously considered. 

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