In the last decades component synthesis has become a critical issue in the research field about new highly integrated energy conversion systems. Several heuristic methodologies following experience-based guidelines have been proposed to simplify the problem of synthesis optimization. This paper describes an application of the HEATSEP method, which consists in the isolation of all the heat transfer processes of an energy system in an undefined "black-box". Then, synthesis optimization can be split in two subproblems, the first about the synthesis/design optimization of the basic plant configuration (which is made up of all the components but heat transfer devices) and the other about the synthesis of the heat exchanger network inside the black-box. The chosen test case is the design optimization of the basic plant configuration of an S-Graz cycle based power plant, as it is suitable to show the potentialities of the method. (C) 2009 Elsevier Ltd. All rights reserved.