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This work has been realised during my time as a PhD researcher at the High-Temperature Processes Unit at IMDEA Energy Institute. The research leading to these results has received funding from the European Union's Seventh Framework Programme(FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement nº 256755 of project ADEL "Advanced Electrolyser for Hydrogen Production with Renewable Energy Sources". I would like to thank all the people that contributed directly or indirectly to this work and without whom this time at IMDEA Energy would have been not by far as gratifying. Thanks to Manuel Romero and Javier Muñoz, and also to José Gonzalez, for their support and supervision, and to the tribunal for assisting to my defence, to the high-temperature processes group Sandra, Elisa, Aurelio, Fabri, Carlos, Selvan, and people from the whole IMDEA Energy Institute, specially to Laura, Jens, Tokhir, Prabhas... for the happy and cheerful atmosphere that surround every day of this period. I truly appreciate the help from my companion, Sandra Álvarez, and my little boy, Leo. Without her presence and support, and his hugs and smiles, the completion of this work would have been more difficult. Finally, I would like to thank my family for their understanding and eternal encouragement.

This work proposes and analyses several integration schemes specially conceived for direct steam generation (DSG) in megawatt (MW) range central receiver solar thermal power plants. It is focused on the optical performance related to the heliostat field and the arrangement of receiver absorbers, and the management of steam within a Rankine cycle in the range between 40–160 bar and 400–550 °C at design point. The solar receiver is composed of one single element for saturated steam systems or two vertically aligned separated units, which correspond to the boiler and the superheater (dual-receiver concept), for superheated steam solar thermal power plants. From a fixed heliostat field obtained after layout optimization for the saturated steam solar plant the heliostat field is divided in two concentric circular trapezoids where each of them independently supplies the solar energy required by the boiler and the superheater for the different steam conditions. It has been observed that the arrangement locating the boiler above the superheater provides a slightly higher optical efficiency of the collector system, formed by the solar field and the receiver, compared with the reverse option with superheater above boiler. Besides, two-zone solar fields provide lower performances than the entire heliostat layout aiming at one absorber (saturation systems). Optical efficiency of two-zone solar fields decreases almost linearly with the increment of superheater heat demand. Concerning the whole solar collector, heliostat field plus receiver, the performance decreases with temperature and almost linearly with the steam pressure. For the intervals of steam pressure and temperature under analysis, solar collector of saturated steam plant achieves an optical efficiency 3.2% points higher than the superheated steam system at 40 bar and 400 °C, and the difference increases up to 9.3% points when compared with superheated system at 160 bar and 550 °C. On the other hand, superheated steam systems at 550 °C and pressure between 60 and 80 bar provide the highest overall efficiency, and it is 2.3% points higher than performance of a saturated steam solar plant at 69 bar. However, if saturated steam cycle integrates an intermediate reheat process, both would provide similar performances. Finally, it has been observed that central receiver systems (CRS) producing saturated steam and superheated steam at 500 °C operating at 40 bar provide similar performances.

(2016). Exergetic analysis of hybrid power plants with biomass and photovoltaics coupled with a solid-oxide electrolysis system. Energy, 94, p.304-315. irradiation drops to 36-46 %. This is a direct result of the lower operational efficiency of the solar panels versus the biomass plant.

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This work presents a comparative study between direct steam generation central receiver solar power plants working at live steam conditions similar to those found in commercial plants. PS10 and PS20 by Abengoa Solar use a single-receiver, producing saturated steam, whereas Sierra SunTower by e-Solar and Ivanpah Solar Electric Generating System (ISEGS) by BrightSource use dual-receiver technology producing superheated steam. The system analysis includes individual studies for each subsystem: solar field, receiver and Rankine power block; as well as the overall-analysis of a 66.7 MWth plant. PS10 working conditions were analysed with and without intermediate reheat step. It was assumed that Sierra SunTower-configuration has non-reheat turbine and Ivanpah-cycle includes an intermediate reheat step. The reheat process in PS10 configuration was performed using a fraction of live steam coming from the receiver; while for Ivanpah-configuration exhaust steam from high pressure turbine stage was sent back to the superheated steam section of the dual-receiver. These concepts make possible to avoid hybridisation and assure special regimes (such as Spanish feed-in tariff). The analysis of the heliostat field for dual-receiver concepts reveals that the aiming strategy on the absorbers has not relevant influence on optical performances. However, receiver efficiency decreased from 91.9%, working with saturated steam, to 87.86–84.14% working with superheated steam related to operating temperatures and heat exchange surface area. This study reveals that the improvement achieved in the power block under Ivanpah configuration was able to compensate higher thermal losses at the receiver, increasing net power production by 25.5% compared with saturated steam conditions.

La identificabilidad es una propiedad esencial de los modelos dinámicos cuyo estudio debe ser abordado antes de iniciar cualquier procedimiento de estimación paramétrica. Sin embargo, este análisis generalmente ha sido ignorado en la literatura con unas pocas excepciones, como por ejemplo en el estudio de los sistemas biológicos. En este trabajo, se estudia la identificabilidad estructural de un sistema de transferencia de calor, con el fin de destacar la importancia de este análisis y animar a los investigadores a tenerlo en cuenta. Con este propósito, primero se presenta un modelo de parámetros concentrados basado en la analogía térmica-eléctrica. Después, se analiza la identificabilidad del modelo haciendo uso del teorema del isomorfismo local. A continuación, se presenta el análisis correspondiente a dos posibles escenarios distintos, en uno de ellos el estado se mide completamente mientras que en el otro sólo se dispone de medidas parciales. En el primer escenario se demuestra que la estructura paramétrica propuesta es identificable, lo que permite estimar los parámetros del sistema empleando datos xperimentales. El segundo escenario se corresponde con una situación no identificable, y sirve de ejemplo de lo que podría ocurrir si esta propiedad no es analizada.