ABSTRACT
A problem is that the quantitative meaning of performance is not so welldefined. Reconsider the dashed curve in Figure 1.1 (b) for a general case. If energy efficiency is the only important criterion for you, you chose the power value at maximum efficiency, and if you do not care at all about energy efficiency, you might want to maximize the power. There may be other constraints and requirements, like small volume, weight, environmental sustainability, acoustic noise, costs, long lifetime, and others. In any case, there is a certain ambiguity in what you finally want to optimize, and what will finally be the preferable operation point, (ηopt, popt) on the efficiency-power curve. Therefore, one cannot claim a generally valid solution for how to optimize technical devices. You should again look, in Figure 1.1 (b), at the part of the dashed efficiency-power curve with negative slope, which describes a set of Pareto optimal solutions of the multi-objective optimization problem of two conflicting goals, namely, maximizing power and efficiency. A Pareto optimum is defined as a point where one cannot improve one objective without worsening the other. Multi-objective optimization theory goes, however, beyond our purpose; we will instead introduce below a simple economic figure as the main objective that should be optimized on the efficiency-power curves.
