Desarrollo de receptores solares volumétricos activos de elevadas prestaciones para centrales termoeléctricas deconcentración en torre

Como se ha comentado previamente, en el Capítulo 4 se ha desarrollado un modelo CFD del prototipo ensayado en el banco de ensayos. El objetivo de este modelo es reproducir las condiciones de flujo y radiación otorgadas por el banco de ensayos para validar los resultados del mismo. Una vez se validó el modelo, se pudieron obtener detalles del comportamiento térmico y fluido-dinámico del receptor. Además, la validación del modelo CFD permitió durante el capítulo 6 reproducir las condiciones de radiación homogéneas presentes en una central CSP real para estimar su rendimiento térmico en condiciones nominales de trabajo y su efecto en una central CSP.Además del comportamiento térmico del receptor, es importante asegurar su integridad estructural de este ante las condiciones de trabajo a las que se podría enfrentar durante su vida útil. Para ello, a lo largo del Capítulo 5 se ha desarrollado el estudio del comportamiento termo mecánico del receptor desde el punto de vista de la mecánica de la fractura. Se ha caracterizado el carburo de silicio, material del receptor, para alimentar un modelo FEM con el que se ha estudiado la expansión de las micro-grietas debido a las tensiones inducidas por los gradientes de tensiones producidos por la temperatura. Este estudio ha arrojado resultados prometedores en cuanto a la vida útil de los discos del receptor para todos los tamaños de disco estudiados, asegurando su durabilidad en su uso en planta y demostrando la viabilidad estructural del concepto. Una vez demostrado el concepto de manera térmica (en los capítulos 3 y 4) y mecánica (en el Capítulo 5), con el fin de comprobar si este concepto mejora en algo a la tecnología actual de receptores volumétricos de aire, durante el Capítulo 6 se ha estudiado mediante el modelo CFD validado previamente, el rendimiento térmico del receptor frente a condiciones de radiación iguales a las de planta (radiación homogénea de hasta 1000 kW/m2) y su efecto en la energía producida y en el coste de la energía en dos configuraciones de central CSP de torre. Los resultados mostrados en este capítulo muestran mejoras en el rendimiento térmico del receptor de más de 0.1, es decir, un 10%, a 750°C.Por último, en el Capítulo 7 se desarrollan las conclusiones generales de la tesis, muy positivas en términos de avance de la tecnología, debido a la innovación del concepto, y en términos de comportamiento térmico de este nuevo concepto. Además, también se han desarrollado las líneas futuras necesarias hasta el desarrollo final de un receptor basado en el concepto de discos.Electricity production from solar thermal power, also called concentrated solar power (CSP), is a renewable generation technology with great potential, as it directly uses solar radiation that reaches the earth's crust. Approximately this solar power provides a total of 85 Peta Watts (85x1015 W), which can be used by terrestrial solar collectors to generate electricity or energy for high-temperature processes. This amount of power is 5000 times higher than the current global energy consumption, which is more than 15 Tera Watts (15x1012 W). In addition to this, CSP technology is able to manage the energy it generates and discharges to the grid, which is an important advantage over other renewable technologies such as wind and photovoltaics, either through thermal storage or hybridization with photovoltaics. Concentrating solar power plants collect the direct solar radiation (direct normal irradiation or DNI) that reaches the earth's surface and redirect it by concentrating it on a receiving surface through which a fluid circulates, absorbing this energy. They transform the energy from solar radiation first into thermal energy and then into mechanical work and electricity through a power cycle. As the element that transforms radiation into thermal energy, the receiver is one of the crucial elements of the plant to achieve high performance and increase the profitability of this type of technology. Moreover, the designs used today do not differ much from those used in the early days as far as air receivers are concerned. Due to the key importance of this element and the little evolution in its development, this thesis has focused on the design and characterization of an air receiver that provides an evolution in this technology. In this work we have developed the design, analysis and experimentation of an innovative receiver geometry and design with the aim that this technology achieves improvements in the thermal efficiency of the receiver as well as improvements from the point of view of durability that make solar thermal plants more competitive in the current electricity market. Thus, the work of this thesis has been structured in 4 blocks corresponding to chapters 3 to 7. The first work of this thesis, contained in Chapter 3, is focused on the explanation of the concept of rotating disks on which the receiver is based and on the experimentation, by means of a prototype at laboratory scale, of this receiver in a test bench prepared for this thesis. The results obtained from this experimentation have served to validate the results obtained from the CFD model of the receiver developed in Chapter 4. Furthermore, with this experimentation, the operation and feasibility of the concept in a controlled, small-scale environment has also been demonstrated at operating temperatures of almost 700°C. As previously mentioned, a CFD model of the prototype tested on the test bench has been developed in Chapter 4. The objective of this model is to reproduce the flow and radiation conditions provided by the test rig in order to validate the results of the model. Once the model was validated, details of the thermal and fluid-dynamic behaviour of the receiver could be obtained. In addition, the validation of the CFD model allowed during Chapter 6 to reproduce the homogeneous radiation conditions present in a real CSP plant to estimate its thermal performance under nominal working conditions and its effect on a CSP plant. In addition to the thermal performance of the receiver, it is important to ensure its structural integrity under the operating conditions that it could face during its working life. To this end, throughout Chapter 5, the study of the thermo-mechanical behaviour of the receiver from the point of view of fracture mechanics has been developed. For this purpose, silicon carbide, the receiver material, has been characterized to feed a FEM model with which the expansion of the micro-cracks due to the stresses induced by the stress gradients produced by the temperature have been studied. This study has yielded promising results in terms of the lifetime of the receiver discs for all the disc sizes studied, ensuring their durability in plant use and demonstrating the structural feasibility of the concept. After demonstrating the concept thermally (in chapters 3 and 4) and mechanically (in Chapter 5), in order to check if this concept is an improvement over current volumetric air receiver technology, during Chapter 6 the thermal performance of the receiver under plant radiation conditions (homogeneous radiation up to 1000 kW/m2) and its effect on the energy produced and the cost of energy in two tower CSP plant configurations were studied using the previously validated CFD model. The results shown in this chapter demonstrate improvements in receiver thermal performance of more than 0.1, a 10%, at 750°C. Finally, Chapter 7 develops the overall conclusions of the thesis, which are very positive in terms of technology advancement, due to the innovation of the concept, and in terms of thermal performance of this new concept. In addition, the necessary future lines have also been developed until the final development of a receiver based on the concept of disks.Gobierno de Navarra, beca obtenida para el desarrollo de la presente tesis doctoral con el número de adjudicación 0011-1408-2017-000016.Programa de Doctorado en Tecnologías de las Comunicaciones, Bioingeniería y de las Energías Renovables (RD 99/2011)Bioingeniaritzako eta Komunikazioen eta Energia Berriztagarrien Teknologietako Doktoretza Programa (ED 99/2011

Techno-economic evaluation of the performance of an innovative rotary disk receiver concept in a CSP power plant

This study evaluates the thermal performance of an innovative discs receiver and models its effect in a CSP plant. Energetic and economic results were compared with a foam receiver developed in the European project CAPTure. The study consists of two parts, on the one hand, it treats the simulation of a CFD model of the innovative disk receiver, from which the thermal efficiency versus air outlet temperature curve was obtained, necessary to feed the second part of the study. This thermal efficiency was compared with the performance of a foam receiver. On the other hand, systemlevel simulations of a CSP multi tower plant are performed in order to obtain the effect of this efficiency-air outlet temperature curve on the overall energetic and economic performance. The study compares the LCOE and the yearly generation of the plant with the innovative discs receiver with that of the foam receiver. Results show the potential in economic and energetic terms of the new receiver in comparison to conventional foam receivers.The authors would like to thank the Government of Navarre for funding this research work under the contract number 0011-1408-2017-000016