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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