The use of solar plants as auxiliary systems in conventional power combined cycles has contributed to the evaporation process, reducing the use of fossil fuels for steam generation. The present work is focused on the analysis and design of sizing the optimum solar field for being implemented in the fourth unit of the combined cycle power plant “Valle de México” in Mexico. The software SOLEEC is used to determine the collector geometrical features based on the absorber tube external diameter; in this study, three cases have been analyzed, 2, 3, and 4 in. absorber tube diameters. The best collector's geometry depends on the steam temperature, the working pressure, and the mass flow necessary to supply the overheated steam; also, the total aperture area of the field, the total reflective surface area, and the thermal efficiency for every case have been obtained; the absorber tube is divided into three sections: preheating, evaporation, and overheating and the collector is considered in Once Trough mode. Once the geometrical and thermal characteristics are obtained for the three designing configurations, an analysis is carried out to determine the advantages of the best configuration that would be selected for this specific application. According to the results, the best geometry is the one with 2 in. in the absorber diameter, producing a fraction of 50.3 kg/s of steam.

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