Advanced Reaction Systems for Hydrogen Production

[EN] This PhD work started in March 2010 with the support of the University of the Basque Country (UPV/EHU) under the program named “Formación de Personal Investigador” at the Chemical and Environmental Engineering Department in the Faculty of Engineering of Bilbao. The major part of the Thesis work was carried out in the mentioned department, as a member of the Sustainable Process Engineering (SuPrEn) research group. In addition, this PhD Thesis includes the research work developed during a period of 6 months at the Institut für Mikrotechnik Mainz GmbH, IMM, in Germany. During the four years of the Thesis, conventional and microreactor systems were tested for several feedstocks renewable and non-renewable, gases and liquids through several reforming processes in order to produce hydrogen. For this purpose, new catalytic formulations which showed high activity, selectivity and stability were design. As a consequence, the PhD work performed allowed the publication of seven scientific articles in peer-reviewed journals. This PhD Thesis is divided into the following six chapters described below. The opportunity of this work is established on the basis of the transition period needed for moving from a petroleum based energy system to a renewable based new one. Consequently, the present global energy scenario was detailed in Chapter 1, and the role of hydrogen as a real alternative in the future energy system was justified based on several outlooks. Therefore, renewable and non-renewable hydrogen production routes were presented, explaining the corresponding benefits and drawbacks. Then, the raw materials used in this Thesis work were described and the most important issues regarding the processes and the characteristics of the catalytic formulations were explained. The introduction chapter finishes by introducing the concepts of decentralized production and process intensification with the use of microreactors. In addition, a small description of these innovative reaction systems and the benefits that entailed their use were also mentioned. In Chapter 2 the main objectives of this Thesis work are summarized. The development of advanced reaction systems for hydrogen rich mixtures production is the main objective. In addition, the use and comparison between two different reaction systems, (fixed bed reactor (FBR) and microreactor), the processing of renewable raw materials, the development of new, active, selective and stable catalytic formulations, and the optimization of the operating conditions were also established as additional partial objectives. Methane and natural gas (NG) steam reforming experimental results obtained when operated with microreactor and FBR systems are presented in Chapter 3. For these experiments nickel-based (Ni/Al2O3 and Ni/MgO) and noble metal-based (Pd/Al2O3 and Pt/Al2O3) catalysts were prepared by wet impregnation and their catalytic activity was measured at several temperatures, from 973 to 1073 K, different S/C ratios, from 1.0 to 2.0, and atmospheric pressure. The Weight Hourly Space Velocity (WHSV) was maintained constant in order to compare the catalytic activity in both reaction systems. The results obtained showed a better performance of the catalysts operating in microreactors. The Ni/MgO catalyst reached the highest hydrogen production yield at 1073 K and steam-to-carbon ratio (S/C) of 1.5 under Steam methane Reforming (SMR) conditions. In addition, this catalyst also showed good activity and stability under NG reforming at S/C=1.0 and 2.0. The Ni/Al2O3 catalyst also showed high activity and good stability and it was the catalyst reaching the highest methane conversion (72.9 %) and H2out/CH4in ratio (2.4) under SMR conditions at 1073 K and S/C=1.0. However, this catalyst suffered from deactivation when it was tested under NG reforming conditions. Regarding the activity measurements carried out with the noble metal-based catalysts in the microreactor systems, they suffered a very quick deactivation, probably because of the effects attributed to carbon deposition, which was detected by Scanning Electron Microscope (SEM). When the FBR was used no catalytic activity was measured with the catalysts under investigation, probably because they were operated at the same WHSV than the microreactors and these WHSVs were too high for FBR system. In Chapter 4 biogas reforming processes were studied. This chapter starts with an introduction explaining the properties of the biogas and the main production routes. Then, the experimental procedure carried out is detailed giving concrete information about the experimental set-up, defining the parameters measured, specifying the characteristics of the reactors used and describing the characterization techniques utilized. Each following section describes the results obtained from activity testing with the different catalysts prepared, which is subsequently summarized: Section 4.3: Biogas reforming processes using γ-Al2O3 based catalysts The activity results obtained by several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on magnesia or alumina modified with oxides like CeO2 and ZrO2 are presented in this section. In addition, an alumina-based commercial catalyst was tested in order to compare the activity results measured. Four different biogas reforming processes were studied using a FBR: dry reforming (DR), biogas steam reforming (BSR), biogas oxidative reforming (BOR) and tri-reforming (TR). For the BSR process different steam to carbon ratios (S/C) from 1.0 to 3.0, were tested. In the case of BOR process the oxygen-to-methane (O2/CH4) ratio was varied from 0.125 to 0.50. Finally, for TR processes different S/C ratios from 1.0 to 3.0, and O2/CH4 ratios of 0.25 and 0.50 were studied. Then, the catalysts which achieved high activity and stability were impregnated in a microreactor to explore the viability of process intensification. The operation with microreactors was carried out under the best experimental conditions measured in the FBR. In addition, the physicochemical characterization of the fresh and spent catalysts was carried out by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), N2 physisorption, H2 chemisorption, Temperature Programmed Reduction (TPR), SEM, X-ray Photoelectron Spectroscopy (XPS) and X-ray powder Diffraction (XRD). Operating with the FBR, conversions close to the ones predicted by thermodynamic calculations were obtained by most of the catalysts tested. The Rh-Ni/Ce-Al2O3 catalyst obtained the highest hydrogen production yield in DR. In BSR process, the Ni/Ce-Al2O3 catalyst achieved the best activity results operating at S/C=1.0. In the case of BOR process, the Ni/Ce-Zr-Al2O3 catalyst showed the highest reactants conversion values operating at O2/CH4=0.25. Finally, in the TR process the Rh-Ni/Ce-Al2O3 catalyst obtained the best results operating at S/C=1.0 and O2/CH4=0.25. Therefore, these three catalysts were selected to be coated onto microchannels in order to test its performance under BOR and TR processes conditions. Although the operation using microreactors was carried out under considerably higher WHSV, similar conversions and yields as the ones measured in FBR were measured. Furthermore, attending to other measurements like Turnover Frequency (TOF) and Hydrogen Productivity (PROD), the values calculated for the catalysts tested in microreactors were one order of magnitude higher. Thus, due to the low dispersion degree measured by H2-chemisorption, the Ni/Ce-Al2O3 catalyst reached the highest TOF and PROD values. Section 4.4: Biogas reforming processes using Zeolites L based catalysts In this section three type of L zeolites, with different morphology and size, were synthesized and used as catalyst support. Then, for each type of L zeolite three nickel monometallic and their homologous Rh-Ni bimetallic catalysts were prepared by the wetness impregnation method. These catalysts were tested using the FBR under DR process and different conditions of BSR (S/C ratio of 1.0 and 2.0), BOR (O2/CH4 ratio of 0.25 and 0.50) and TR processes (at S/C=1.0 and O2/CH4=0.25). The characterization of these catalysts was also carried out by using the same techniques mentioned in the previous section. Very high methane and carbon dioxide conversion values were measured for almost all the catalysts under investigation. The experimental results evidenced the better catalytic behavior of the bimetallic catalysts as compared to the monometallic ones. Comparing the catalysts behavior with regards to their morphology, for the BSR process the Disc catalysts were the most active ones at the lowest S/C ratio tested. On the contrary, the Cylindrical (30–60 nm) catalysts were more active under BOR conditions at O2/CH4=0.25 and TR processes. By the contrary, the Cylindrical (1–3 µm) catalysts showed the worst activity results for both processes. Section 4.5: Biogas reforming processes using Na+ and Cs+ doped Zeolites LTL based catalysts A method for the synthesis of Linde Type L (LTL) zeolite under microwave-assisted hydrothermal conditions and its behavior as a support for heterogeneously catalyzed hydrogen production is described in this section. Then, rhodium and nickel-based bimetallic catalysts were prepared in order to be tested by DR process and BOR process at O2/CH4=0.25. Moreover, the characterization of the catalysts under investigation was also carried out. Higher activities were achieved by the catalysts prepared from the non-doped zeolites, Rh-Ni/D and Rh-Ni/N, as compared to the ones supported on Na+ and Cs+ exchanged supports. However, the differences between them were not very significant. In addition, the Na+ and Cs+ incorporation affected mainly to the Disc catalysts. Comparing the results obtained by these catalysts with the ones studied in the section 4.4, in general worst results were achieved under DR conditions and almost the same results when operated under BOR conditions. In Chapter 5 the ethylene glycol (EG) as feed for syngas production by steam reforming (SR) and oxidative steam reforming (OSR) was studied by using microchannel reactors. The product composition was determined at a S/C of 4.0, reaction temperatures between 625°C and 725°C, atmospheric pressure and Volume Hourly Space Velocities (VHSV) between 100 and 300 NL/(gcath). This work was divided in two sections. The first one corresponds to the introduction of the main and most promising EG production routes. Then, the new experimental procedure is detailed and the information about the experimental set-up and the measured parameters is described. The characterization was carried out using the same techniques as for the previous chapter. Then, the next sections correspond to the catalytic activity and catalysts characterization results. Section 5.3: xRh-cm and xRh-np catalysts for ethylene glycol reforming Initially, catalysts with different rhodium loading, from 1.0 to 5.0 wt. %, and supported on α-Al2O3 were prepared by two different preparation methods (conventional impregnation and separate nanoparticle synthesis). Then, the catalysts were compared regarding their measured activity and selectivity, as well as the characterization results obtained before and after the activity tests carried out. The samples prepared by a conventional impregnation method showed generally higher activity compared to catalysts prepared from Rh nanoparticles. By-product formation of species such as acetaldehyde, ethane and ethylene was detected, regardless if oxygen was added to the feed or not. Among the catalysts tested, the 2.5Rh-cm catalyst was considered the best one. Section 5.4: 2.5Rh-cm catalyst support modification with CeO2 and La2O3 In this part of the Chapter 5, the catalyst showing the best performance in the previous section, the 2.5Rh-Al2O3 catalyst, was selected in order to be improved. Therefore, new Rh based catalysts were designed using α-Al2O3 and being modified this support with different contents of CeO2 or La2O3 oxides. All the catalysts containing additives showed complete conversion and selectivities close to the equilibrium in both SR and OSR processes. In addition, for these catalysts the concentrations measured for the C2H4, CH4, CH3CHO and C2H6 by-products were very low. Finally, the 2.5Rh-20Ce catalyst was selected according to its catalytic activity and characterization results in order to run a stability test, which lasted more than 115 hours under stable operation. The last chapter, Chapter 6, summarizes the main conclusions achieved throughout this Thesis work. Although very high reactant conversions and rich hydrogen mixtures were obtained using a fixed bed reaction system, the use of microreactors improves the key issues, heat and mass transfer limitations, through which the reforming reactions are intensified. Therefore, they seem to be a very interesting and promising alternative for process intensification and decentralized production for remote application.[ES] La presente Tesis Doctoral tuvo su inicio en Marzo de 2010 gracias a la obtención de la beca perteneciente al programa de “Formación de Personal de investigación” impulsado por la Universidad del País Vasco / Euskal Herriko Unibertsitatea (UPV/EHU). Esta Tesis ha sido desarrollada prácticamente en su totalidad en el Departamento de Ingeniería Química y del Medio Ambiente de la Escuela Técnica Superior de Ingeniería de Bilbao, como miembro del grupo de investigación Sustainable Process Engineering (SuPrEn). Además, esta Tesis incluye el trabajo realizado durante el periodo de seis meses de estancia pre-doctoral en el centro Institut für Mikrotechnik Mainz GmbH, IMM, de Alemania. El trabajo llevado a cabo durante los cuatro años se centra en la obtención de hidrógeno, vector energético limpio y combustible del futuro, a partir de diversas materias primas. Sin embargo, el mayor aporte de esta Tesis a la comunidad científica viene dado por la utilización de los sistemas de reacción denominados microrreactores para la producción de hidrógeno. Este tipo de sistemas están siendo hoy en día objeto de estudio ya que son una solución viable a la producción de hidrógeno de manera descentralizada y porque además, presentan varias ventajas en comparación con los métodos actuales de producción de hidrógeno. Asimismo, la comparación entre sistemas de reacción convencionales y los microrreactores, también ha sido objeto de estudio en la presente Tesis. De igual modo, para los procesos de reformado estudiados, se han desarrollado varios sistemas catalíticos que han mostrado altas actividades en cuanto a conversión de reactivos se refiere, gran selectividad a hidrógeno y muy buena estabilidad en cuanto a operación y durabilidad se refiere. Inicialmente, se empleó metano y gas natural como fuentes de alimentación no renovables, llevando a cabo una comparativa de los dos sistemas de reacción previamente mencionados. Sin embargo, otro de los objetivos de la presente Tesis ha sido el uso de fuentes de alimentación renovables, ya que uno de los grandes retos de la comunidad científica recae en la obtención de un producto limpio, el hidrógeno, a partir de recursos renovables. De este modo, la mayor parte del trabajo se basa en el estudio de la producción de hidrógeno a partir de biogás. Este gas, procedente de la descomposición anaerobia de la materia orgánica, como puede ser la biomasa, se compone prácticamente de metano y dióxido de carbono. De esta forma, convirtiendo estos dos gases a hidrógeno, los beneficios económicos, ambientales y sociales alcanzables serían de gran relevancia dado que los dos contribuyen en gran medida al denominado efecto invernadero. Además de con biogás, también se han llevado a cabo ensayos de actividad catalítica con etilenglicol, recurso renovable mayoritario procedente de la conversión catalítica de la celulosa. Acorde a cada una de las materias primas a tratar se prepararon diferentes formulaciones catalíticas, con el objetivo de conocer el efecto de los diferentes soportes a utilizar, de sus modificaciones, de las cargas metálicas y cómo no, de las concentraciones de las propias especies metálicas presentes en los catalizadores. Con el objeto de poder interpretar los resultados obtenidos con los catalizadores utilizados en cada apartado, se llevó a cabo una exhaustiva caracterización de los mismos antes y después de haber sido probados en los ensayos de actividad catalítica, así como un estudio de la correlación entre las propiedades superficiales medidas mediante caracterización y los resultados de actividad catalítica. Para poder detallar de manera satisfactoria toda la información recabada a lo largo de los cuatro años de investigación, esta Tesis ha sido dividida en 6 capítulos independientes, los cuales se resumen a continuación: En el Capítulo 1, se justifica la necesidad de llevar a cabo este trabajo de investigación, mediante el cual se busca un cambio en el sistema energético actual basado en el petróleo. Sin duda, la creciente demanda energética existente y el agotamiento de los recursos fósiles hacen necesario la búsqueda de alternativas para poder mantener la calidad de vida actual. Además, en este apartado introductorio también se detalla el estado del arte en cuanto a los métodos de producción de hidrógeno se refiere, los reactores existentes y los catalizadores más comúnmente empleados. En el apartado siguiente, el Capítulo 2, se detalla el propósito establecido para el desarrollo de esta Tesis. Además de la producción de hidrógeno mediante sistemas de reacción convencionales y su comparación con los sistemas de reacción avanzados denominados microrreactores, el uso de diferentes fuentes de alimentación y tipos de catalizadores, también han sido metas a alcanzar en esta Tesis. Por otra parte no hay que olvidar que el propósito impulsado por la Universidad de País Vasco / Euskal Herriko Unibertsitatea, es el de formar a personas como futuros investigadores, siendo éste un objetivo alcanzado a medida que se ha desarrollado la Tesis Doctoral. El Capítulo 3, es el primero de los apartados correspondientes a la actividad experimental llevada a cabo. En él se detallan los ensayos realizados con metano y gas natural como reactivos para la obtención de hidrógeno. Además, en esta sección se hace una comparación de los dos sistemas de reacción empleados habiendo sido llevados a cabo los ensayos a iguales velocidades espaciales. Para el desarrollo de los correspondientes ensayos de actividad catalítica se prepararon cuatro catalizadores diferentes, basados en alúmina y magnesia con especies metálicas nobles (Pt y Pd) y no nobles (Ni). A lo largo de este capítulo se detalla la metodología empleada a la hora de preparar, impregnar y acondicionar los microrreactores, así como la llevada a cabo para preparar los reactores de lecho fijo empleados. También se describe el equipamiento utilizado para realizar los ensayos de reacción, así como para la identificación y cuantificación de los productos obtenidos en reacción. Entre los resultados obtenidos cabe destacar la gran estabilidad mostrada por los microrreactores y la alta actividad medida en operación para el catalizador de Ni/MgO tanto en el reformado de metano como en el de gas natural. En cuanto al catalizador de Ni/Al2O3, también se midieron altas conversiones de metano; sin embargo, sufrió una desactivación severa cuando fue utilizado para la producción de hidrógeno a partir de gas natural. En cuanto a los catalizadores basados en metales nobles y soportados sobre alúmina, éstos no mostraron actividad alguna posiblemente debido a la deposición de coque, que fue detectado por SEM. El Capítulo 4, se compone de tres secciones en función de los catalizadores empleados para el reformado de biogás, que se detallan a continuación: Sección 4.3: Estudio de los diferentes tipos de reformado de biogás con catalizadores basados en γ-Al2O3 En este apartado se prepararon 4 catalizadores basados en alúmina cuyos soportes fueron modificados con CeO2, ZrO2 o una mezcla de ambos. A uno de los catalizadores se le añadió una pequeña cantidad de Rh con el objetivo de estudiar su influencia. Además, se utilizó también un catalizador basado en MgO y otro comercial basado en alúmina con el propósito de poder comparar los resultados obtenidos. En cuanto a los procesos, cuatro fueron objeto de estudio utilizando el reactor de lecho fijo: reformado seco (dry reforming, DR), reformado de biogás con vapor de agua (biogas steam reforming, BSR), reformado oxidativo de biogás (biogas oxidative reforming, BOR) y tri-reformado (tri-reforming, TR). En ellos se probaron los catalizadores anteriormente mencionados para ratios crecientes de vapor de agua/carbono (S/C), O2/CH4 o ambos conjuntamente en el caso del proceso de tri-reformado. Una vez establecidos los parámetros de operación óptimos mediante el reactor de lecho fijo, los tres sistemas catalíticos que obtuvieron los mejores resultados se impregnaron y ensayaron en los microrreactores. De este modo, se pudo llevar a cabo una interesante comparación entre ambos sistemas de reacción. Asimismo, los sistemas catalíticos se caracterizaron antes y después de los ensayos realizados. Entre los resultados obtenidos, cabe destacar las altas conversiones alcanzadas por todos los catalizadores, cercanas a las calculadas por el equilibrio termodinámico. En el proceso de DR, el catalizador Rh-Ni/Ce-Al2O3 fue el que alcanzó el mayor rendimiento a hidrógeno. En cuanto al proceso de BSR, las mejores condiciones de operación fueron medidas para el ratio S/C=1.0 y para el catalizador Ni/Ce-Al2O3. El ratio óptimo de O2/CH4 para lograr una mayor conversión de reactivos fue de 0.

The Influence of the Chamber Configuration on the Hydrodynamic Efficiency of Oscillating Water Column Devices

Based on the two-dimensional linear wave theory, the effects of the front wall thickness and the bottom profile of an Oscillating Water Column (OWC) device on its efficiency were analyzed. Using the potential flow approach, the solution of the associated boundary value problem was obtained via the boundary element method (BEM). Numerical results for several physical parameters and configurations were obtained. The effects of the front wall thickness on the efficiency are discussed in detail, then, various configurations of the chamber bottom are presented. A wider efficiency band was obtained with a thinner front wall. In a real scenario having a thinner front wall means that such a structure could have less capacity to withstand the impact of storm waves. Applying the model for the case of the Mutriku Wave Energy Plant (MWEP), findings showed that the proposed bottom profiles alter the efficiency curve slightly; higher periods of the incoming water waves were found. This could increase the efficiency of the device in the long-wave regime. Finally, the numerical results were compared with those available in the literature, and were found to be in good agreement.The present research has been developed under the framework of CEMIE-Océano (Mexican Centre for Innovation in Ocean Energy). Project FSE-2014-06-249795 financed by CONACYT-SENER- Sustentabilidad Energética. In addition, the authors would like also to express their gratitude for the funding provided by the UPV/EHU [PPGA20/26 research group] and the Basque Government (IT1314-19 research group)

Computational Study of Overtopping Phenomenon over Cylindrical Structures Including Mitigation Structures

Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known.This work was carried out within the framework of the ITSAS-REM Research Group (IT-1514-22) funded by the Basque Government

Experimental and numerical determination of the optimum configuration of a parabolic wave extinction system for flumes

[EN]In this work the phenomenon of the wave reflection has been studied using a self-developed passive extinction system. Twenty one type of waves were generated in the laboratory using a piston-type wave maker. The variation of the reflection coefficient, Kr, was studied at several depths (h [m] of 0.3, 0.4, and 0.5), periods (0.636 < T [s] < 1.526), wave heights (0.010 < H [m] < 0.064), slopes (3 < α [°] < 17) and vertical end positions of the extinction system (y1 [m] and y2 [m] defined by y1 [m] and α [°]), covering the linear and non-linear regions of the “Le Méhauté” chart. In parallel, an unsteady numerical model based on the Eulerian multiphase VOF was designed and validated according to the free surface displacement, ɳi, and the calculation of the Kr values. Both type of validations were successful so this model was used in order to determine Kr values at slopes [°] that could not be physically reached by the extinction system. The obtained results allowed to determine the minimum Kr values for each set of experiments and finding a useful non-dimensional relationship of Kr,(h-y1)/λ and Ir as a function of the dispersion parameter, kh.The authors would like also to express their gratitude for the support provided by the Research Groups of the UPV/EHU (GIU19/029) and the Basque Government (IT1314-19) , as well as the support provided by the Joint Research Laboratory on Offshore Renewable Energy (JRL-ORE) and the Open Access funding provided by University of Basque Country

Catalyst Deactivation And Regeneration Processes In Biogas Tri-Reforming Process. The Effect Of Hydrogen Sulfide Addition

This work studies Ni-based catalyst deactivation and regeneration processes in the presence of H2S under a biogas tri-reforming process for hydrogen production, which is an energy vector of great interest. 25 ppm of hydrogen sulfide were continuously added to the system in order to provoke an observable catalyst deactivation, and once fully deactivated two different regeneration processes were studied: a self-regeneration and a regeneration by low temperature oxidation. For that purpose, several Ni-based catalysts and a bimetallic Rh-Ni catalyst supported on alumina modified with CeO2 and ZrO2 were used as well as a commercial Katalco 57-5 for comparison purposes. Ni/Ce-Al2O3 and Ni/Ce-Zr-Al2O3 catalysts almost recovered their initial activity. For these catalysts, after the regeneration under oxidative conditions at low temperature, the CO2 conversions achieved79.5% and 86.9%, respectivelywere significantly higher than the ones obtained before sulfur poisoning66.7% and 45.2%, respectively. This effect could be attributed to the support modification with CeO2 and the higher selectivity achieved for the Reverse Water-Gas-Shift (rWGS) reaction after catalysts deactivation. As expected, the bimetallic Rh-Ni/Ce-Al2O3 catalyst showed higher resistance to deactivation and its sulfur poisoning seems to be reversible. In the case of the commercial and Ni/Zr-Al2O3 catalysts, they did not recover their activity.This research was supported by the University of the Basque Country (UPV/EHU), the Central Analysis Service (SGIker) of the UPV/EHU, the Spanish Ministry of Economy and Competitiveness (ENE2014-53566-P), the European Union through the European Regional Development Fund (FEDER) and Naturgas Company (EDP group)

Olatu-kanal baten balioztatze esperimentala eta konputazionala

BiMEP-Biscay Marine Energy Platform- eta Mutriku Wave Energy Plant-eko azpiegituretan itsas energiaren inguruko ikerkuntza egiten da, itsas baldintza errealetan. Bilboko Ingeniaritza Eskolako Fluidoen Mekanikako laborategian dagoen olatu-kanala (12,5 × 0,6 × 0,7 m, luzera × zabalera × sakonera) azpiegitura horietan izaten diren baldintzak erreproduzitzeko gai da, eskala txikiago batean. Olatu-kanal horrek, pistoi motako olatu-sorgailu bat erabiliz, olatu monokromatiko eta pankromatiko mota desberdinekin lan egiteko aukera eskaintzen du. Ultrasoinuak erabiltzen dituzten zenbait zundak ur-gainazalaren desplazamendu bertikala neurtzen dute, eta tankearen amaieran kokatuta dagoen hondartzak, parabola-formadunak, olatuaren energia disipatzen du horren islapena murriztuz. "Reynolds Averaged Navier Stokes" (RANS) ekuazioetan oinarritutako zenbakizko modelo bat sortu da Star-CCM+ kode komertziala erabiliz, gainazal askean gertatzen diren fenomenoak simulatzeko. Zenbakizko modelo horren balioztatzea aurkezten da artikulu honetan, sakonera, olatu-altuera, uhin-luzera eta periodo desberdinak bateratuta eta egindako esperimentu sortarekin konparatuta. Emaitza guztiak fluxu potentzialaren teoriatik lortutako emaitza analitikoekin batera aztertu dira. Lan honetan aurkezten diren esperimentuek kanal horren eraginkortasunaren mugak ezartzen dituzte, olatuen sorkuntzari, hedapenari eta suntsipenari dagokienez. Etorkizunean egingo diren ikerkuntza-lanetako parametroak ezartzeko ere baliogarria izan da lan hau: egitura flotagarrien eta olatuen arteko interakzioa, olatu energiaren bihurgailuak eta ainguratze- eta amarradura-sistemak aztertuko dira.; A wave flume of 12.5 × 0.6 × 0.7 m (length × width × height) able to reproduce the ocean conditions of the most representative research facilities in the Basque Country (BiMEP-Biscay Marine Energy Platform and Mutriku Wave Energy Plant) has been installed at the laboratory of Fluid Mechanics of the Faculty of Engineering in Bilbao. This new facility has the capacity of producing a wide range of monochromatic and panchromatic waves by a piston-type wavemaker.Several ultrasonic wave probes measure the surface elevation, and the wave energy is dissipated in a passive parabolic beach in order to diminish significantly the reflection along the flume. A numerical model based on Reynolds Averaged Navier Stokes (RANS) equations has been developed to represent the turbulence and Eulerian Volume of Fluid (VOF) unsteady approach in STAR-CCM+ CFD code to track the evolution of the free surface. This numerical model has been validated with the corresponding experimental campaign covering a wide range of depths, wave heights, wavelengths and periods.The results are analysed together with the analytical solution coming from the potential flow theory. The experiments carried out in the present work establish the operational limits of the wave flume in terms of wave generation, propagation and extinction, defining the operational range of future experimental and computational campaigns where wave interaction with floating structures, wave energy converters and mooring systems will be studied

Aplikazio biomimetikoak itsas energien atzemate-gailuetan

The study of nature as a source of inspiration has resulted in the design of different energy harnessing devices from the sea. This article brings together the marine devices based on biomimicry, focusing on those whose behavior favors the energy capture [1]. Finally, as the skin of sharks is formed by tiny spicules that allow breaking the boundary layer of the fluid and, thus, reducing the resistance to advance of the shark [2], the application under study in wave flume energy absorption systems will be detailed, which are laboratory devices that allow wave generation phenomena to be reproduced at reduced scale.; Natura inspirazio-iturri gisa aztertzeak itsasotik datorren energiaz baliatzeko makinak diseinatzea eragin du. Dokumentu honek biomimesian oinarrituriko itsas gailuak aztertzen ditu, haien portaeraren ondorioz energia bereganatzea errazten duten horietan oinarrituz [1]. Azkenik, marrazoen larruazala jariakinaren muga-geruza apurtzea ahalbidetzen duten espikula txikiz osatuta dagoenez, haren mugimenduarekiko erresistentzia murriztuz [2], eta fenomeno horretan oinarrituz, olatuak sortzeko erabiltzen diren olatu-kanaletan (waveflumes) energia xahutzeko sistemetan aztertzen den aplikazioa zehaztuko da

A macroscale optimal substructure selection for Europe’s offshore wind farms

Considering the political decisions taken in Europe in the last year, there is a renewed interest in the offshore wind sector. A considerable growth of large-scale offshore wind farms (OWF) is noticeable in Europe mainly due to technological advances in wind turbines and foundation structures, which have reduced their costs and improved their performance, and contributed to the implementation of offshore plants. This study uses a Multi-Criterion Decision Making (MCDM) approach in a Geographic Information System (GIS) to analyze which type of foundation is more adequate according to water depth, soil, and wave conditions, as these parameters affect not only the viability of the foundation type but also on the Levelized Cost of Energy (LCoE) of wind energy of the European seas. The results highlight the importance of floating offshore wind, as 61.55% of the total area could be exploited by these means. Moreover, the current exploited power could be increased by a factor of 615. The validation of the obtained results with up-to-date empirical data confirms the accuracy of this study and shed light on the importance of offshore wind, what could encourage policymakers on their decision-making process.Authors would like to thank the University of the Basque Country (UPV/EHU) and the Basque Government through the research group (IT1514-22)

Experimental analysis and numerical simulation of wave overtopping on a fixed vertical cylinder under regular waves

Wave overtopping phenomenon affects relatively narrow offshore marine structures different from shoreline linear structures, where there is not defined a precise prediction methodology as it is the case of the behaviour at long coastal defences. In the present study a combined experimental and numerical approach has been followed to obtain an empirical relation that represents the relative overtopping discharge over a fixed vertical cylinder exposed to non-impulsive wave conditions. The phenomenon follows a Weibull type dependence on the relative freeboard in a similar way as the case of vertical walls but reporting a decreasing overtopping rate at higher freeboards. In addition, a direct linear relationship between the relative mean flow thickness computed at the centre of the circular crest of the cylinder and the relative overtopping discharge has been observed. This methodology may be used as an indirect cost-effective method to characterize experimentally the wave overtopping phenomenon in cylindrical structures of full-scale prototypes without the need of accumulating and characterising huge amounts of overtopped water volumes. The present study contains a systematic analysis of the dispersion obtained in the experimental and computational results to evaluate the performance attributed to the proposed empirical expressions.The study was conducted within the framework of the research project MATHEO (KK-2019/00085) funded by the Basque Government. The authors would like also to express their gratitude for the support provided by the Research Groups of the UPV/EHU (GIU19/029) and the Basque Government (IT1314-19), as well as the support provided by the Joint Research Laboratory on Offshore Renewable Energy (JRL-ORE). Open Access funding provided by University of Basque Country

Aprendizaje competencial efectivo mediante las prácticas del laboratorio de las asignaturas del área de Mecánica de Fluidos de los estudios de Grado y Máster de Ingeniería Industrial de la Escuela de Ingeniería de Bilbao

Resumen de los autoresUniversidad del País Vasco. Escuela Técnica Superior de Ingeniería (Bilbao)El Proyecto de Innovación Educativa FLUID-IBL surge con el propósito de conseguir un aprendizaje situacional significativo en las prácticas de laboratorio de las asignaturas del área de Mecánica de Fluidos de los estudios de grado y máster de ingeniería industrial de la Escuela de Ingeniería de Bilbao. Este proyecto desarrolla una estrategia estructurada del equipo docente para resolver las carencias encontradas en el proceso de enseñanza-aprendizaje del trabajo práctico desarrollado en el laboratorio y conseguir con éxito el desarrollo de resultados de aprendizaje por parte del alumnado. Estos resultados de aprendizaje contienen diferentes dimensiones competenciales que engloban el trabajo cooperativo, la argumentación y comunicación oral y escrita además del ámbito científico-técnico asociado al saber. El presente trabajo presenta el análisis del problema detectado y las líneas maestras de actuación propuestas para su resolución.ES