4 COMPARATIVE ANALYSIS 4.1 ASSUMPTIONS AND ALTERNATIVE FUTURES SCENARIOS 4^1.1 Assumptions of the Comparative Analysis Three levels of comparative analysis are described in the assessment framework (Sec. 2) and illustrated in Fig. 2.1. These levels are (1) comparison of characterizations, (2) side-by-side analysis, and (3) alternative futures analysis. In this section, comparisons are made, issue by issue, at each of these levels. Each level of analysis has associated assumptions, and are ordered in a hierachy: therefore, the analysis and assumptions are cumulative as one proceeds from the lowest level (characterization comparison) to the highest level (alternative futures analysis). Before proceeding to the description of these comparative analyses, it is important to delineate the assumptions used here in order to place the comparisons in proper perspective. By assumptions we mean any important information, caveats, or baseline data that affect the analysis. Many assumptions were made in the course of the comparative analyses, and to describe them all would obscure the comparisons. Therefore, the ones described here are those that most affect the perspective of the analysis. The description of these assumptions is handled sequentially (i.e., as part of the characterization, side-by-side analysis, and alternative futures analys is). Comparison of Characterizations. These comparisons are made on the basis of the parameters that define a system (e.g., capital cost, O&M cost, resource consumption, and environmental residuals). Therefore, the characterization comparison is solely dependent on the technology description. For currently utilized technologies (i.e., coal and nuclear fission) most of these parameters are fairly well-defined because advanced technologies represent extrapolations of existing systems. In the case of the newer technologies (i.e., TPV, SPS, fusion), in which similar technology is not in operation, the parameters represent estimates based on design assumptions. The technologies selected and characterized for these assessments are intended to represent electrical supply systems that could satisfy energy demand in the 2000-2030 era. Some of the advances in design are in limited operation or have been demonstrated, but for others, only design or conceptual information exists. The characterizations were carefully prepared so that the analysis of each technology is internally consistent. For example, the capital cost information presented for a technology includes the cost of environmental control systems, and the assessment of environmental performance is based on the same environmental control systems. The characterizations were developed according to an integrated procedure; therefore, characterization data reported in this assessment may be different from piecemeal information (e.g., capital cost, environmental performance) reported elsewhere .
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