Navegando por Autor "Alexandre, Rafael Frederico"

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A comparison between cost optimality and return on investment forenergy retrofit in buildings - a real options perspective.
(2016) Tadeu, Sérgio Fernando; Alexandre, Rafael Frederico; Tadeu, António J. B.; Antunes, Carlos Henggeler; Simões, Nuno A. V.; Silva, Patrícia Pereira da
tEuropean Union (EU) regulations aim to ensure that the energy performance of buildings meets thecost-optimality criteria for energy efficiency measures. The methodological framework proposed in EUDelegated Regulation 244 is addressed to national authorities (not investors); the optimal cost level iscalculated to develop regulations applicable at domestic level. Despite the complexity and the large num-ber of possible combinations of economically viable efficiency measures, the real options for improvingenergy performance available to decision makers in building retrofit can be established. Our study con-siders a multi-objective optimization approach to identify the minimum global cost and primary energyneeds of 154,000 combinations of energy efficiency measures. The proposed model is solved by the NSGA-II multi-objective evolutionary algorithm. As a result, the cost-optimal levels and a return on investmentapproach are compared for a set of suitable solutions for a reference building. Eighteen combinations ofretrofit measures are selected and an analysis of the influence of real options on investments is proposed.We show that a sound methodological approach to determining the advantages of this type of investmentshould be offered so that Member States can provide valuable information and ensure that the minimumrequirements are profitable to most investors.
LONSA : a labeling-oriented non-dominated sorting algorithm for evolutionary many-objective optimization.
(2018) Alexandre, Rafael Frederico; Barbosa, Carlos Henrique Nogueira de Resende; Vasconcelos, João Antônio de
Multiobjective algorithms are powerful in tackling complex optmization problems mathematically represented by two or more conflicting objective functions and their constraints. Sorting a set of current solutions across non-dominated fronts is the key step for the searching process to finally identify which ones are the best solutions. To perform that step, a high computational effort is demanded, especially if the size of the solution set is huge or the mathematical model corresponds to a many-objective problem. In order to overcome this, a new labeling-oriented algorithm is proposed in this paper to speed up the solution-to-front assignment by avoiding usual dominance tests. Along with this algorithm, called Labeling-Oriented Non-dominated Sorting Algorithm (LONSA), the associated methodology is carefully detailed to clearly explain how the classification of the solution set is successfully achieved. This work presents a comparison between LONSA and other well-known algorithms usually found in the literature. The simulation results have shown a better performance of the proposed algorithm against nine chosen strategies in terms of computational time as well as number of comparisons.
A practical codification and its analysis for the generalized reconfiguration problem.
(2013) Barbosa, Carlos Henrique Nogueira de Resende; Alexandre, Rafael Frederico; Vasconcelos, João Antônio de
Distribution network reconfiguration problem is simply aimed at finding the best set of radial configurations among a huge number of possibilities. Each solution of this set ensures optimal operation of the system without violating any prescribed constraint. To solve such problem, it is important to count on efficient procedure to enforce radiality. In this paper, we propose a reliable approach to deal properly with topology constraint enabling algorithm convergence toward optimal or quasi-optimal solutions. A simple and practical codification of individuals used in evolutionary algorithms to solve the generalized reconfiguration problem is detailed in this paper. Mathematical formulation, algorithm, and simulation results are presented for the distribution reconfiguration problem, incorporating a new representation scheme which is immune to topologically unfeasible possibilities. The individual interpretation procedure is straight and it demands no additional data structure or graph preprocessing. Comparisons are made for five well-known distribution systems to demonstrate the efficacy of the proposed methodology. It is also demonstrated that optimal configurations are properly surveyed when single or multiple sources are dealt.