• Energy Research

Studies regarding renewable energy sources have gained attention over recent years. One example is wave energy converters, which harvest energy from sea waves using different operational principles such as oscillating water columns, oscillating bodies, and overtopping devices. In the present paper, a numerical study is carried out, and a geometrical investigation of a full-scale overtopping device with a coupled structure mounted on the seabed is performed using the Constructal Design method. The main purpose is to investigate the influence of the design over the available power of the device. The areas of the overtopping ramp (Ar) and the trapezoidal seabed structure (At) are the problem constraints. Two degrees of freedom are studied, the ratio between the height and length of the ramp (H3/L3) and the ratio between the upper and lower basis of the trapezoidal obstacle (L1/L2). The device submersion is kept constant (H1 = 3.5 m). The equations of continuity, momentum, and the transport of volume fraction are solved with the Finite Volume Method, while the water–air mixture is treated with the multiphase model Volume of Fluid. Results showed that the ratio H3/L3 presented a higher sensibility than the ratio L1/L2 over the accumulated water in the reservoir. Despite that, the association of a structure coupled to the ramp of an overtopping device improved the performance of the converter by 30% compared to a conventional condition without the structure.

Évaluation numérique de l'efficacité du convertisseur d'énergie des vagues de type à plaques horizontales immergéesLa haute disponibilité de l'énergie dans les vagues océaniques est considérée comme une alternative importante et abondante en tant que source d'énergie renouvelable. Cet article présente une étude numérique du convertisseur d'énergie des vagues de type à plaques horizontales immergées, évaluant son efficacité théorique pour plusieurs hauteurs de plaques relatives. La propagation et l'incidence de périodes de vagues distinctes à travers la structure du dispositif ont été simulées, et l'efficacité du dispositif a été évaluée sans tenir compte de la présence de la turbine sous la plaque.Un total de six périodes d'onde entre 1,25 et 3,50 s avec une hauteur d'onde de 0,06 m ont été considérées pour six hauteurs de plaque différentes.Les résultats permettent de faire des recommandations théoriques sur les performances du convertisseur.Le modèle de volume de fluide polyphasique a été utilisé par une approche bidimensionnelle pour l'interaction air-eau et les équations de conservation du transport de masse, de quantité de mouvement et de fraction de volume ont été résolues par la méthode du volume fini.Les résultats de l'analyse ont permis d'observer que la hauteur de plaque relative la plus élevée conduit à des efficacités de plaque horizontale immergée améliorées parmi les périodes d'onde simulées, ainsi qu'à l'identification d'une efficacité théorique du dispositif jusqu'à trois fois plus élevée pour des périodes d'onde plus grandes que pour des périodes d'onde plus courtes. Evaluación numérica de la eficiencia del convertidor de energía de las olas del tipo de placa horizontal sumergidaLa alta disponibilidad de energía dentro de las olas del océano se considera una alternativa importante y abundante como fuente de energía renovable. Este documento presenta un estudio numérico del convertidor de energía de las olas del tipo de placa horizontal sumergida, evaluando su eficiencia teórica para varias alturas relativas de las placas. Se simularon la propagación y la incidencia de distintos períodos de las olas a través de la estructura del dispositivo. y se evaluó la eficiencia del dispositivo sin tener en cuenta la presencia de la turbina debajo de la placa. Se consideraron un total de seis períodos de onda entre 1.25 y 3.50 s con una altura de onda de 0.06 m para seis alturas de placa diferentes. Los resultados permiten hacer recomendaciones teóricas sobre el rendimiento del convertidor. El modelo de volumen de fluido multifásico se utilizó a través de un enfoque bidimensional para la interacción aire-agua y las ecuaciones de conservación de transporte de masa, momento y fracción de volumen se resolvieron mediante el método de volumen finito. Los resultados del análisis permitieron observar que la altura de placa relativa más alta conduce a eficiencias de placa horizontal sumergida mejoradas entre los periodos de onda simulados, así como a la identificación de una eficiencia teórica del dispositivo hasta tres veces mayor para periodos de onda más grandes que para periodos de onda más cortos. Numerical Evaluation on the Efficiency of the Submerged Horizontal Plate Type Wave Energy ConverterThe high availability of energy within ocean waves is seen as an important and abundant alternative as a renewable energy source.This paper presents a numerical study of the submerged horizontal plate type wave energy converter, assessing its theoretical efficiency for several relative plate heights.The propagation and incidence of distinct wave periods through the device structure were simulated, and the device efficiency was evaluated disregarding the presence of the turbine under the plate.A total of six wave periods between 1.25 and 3.50 s with wave height of 0.06 m were considered for six different plate heights.The results allow to make theoretical recommendations on the converter performance.The multiphase Volume of Fluid model was used through a two-dimensional approach for air-water interaction and the conservation equations of mass, momentum and volume fraction transport were solved by the Finite Volume Method.The results of analysis allowed to observe that the highest relative plate height leads to enhanced submerged horizontal plate efficiencies among the simulated wave periods, as well as to identification of a theoretical device efficiency up to three times higher for larger wave periods than for shorter wave periods. التقييم العددي لكفاءة محول الطاقة الموجية من النوع الأفقي المغمور يُنظر إلى التوافر العالي للطاقة داخل موجات المحيط على أنه بديل مهم ووفير كمصدر للطاقة المتجددة. تقدم هذه الورقة دراسة عددية لمحول الطاقة الموجية من النوع الأفقي المغمور، وتقييم كفاءته النظرية لعدة ارتفاعات نسبية للصفائح. تم محاكاة انتشار وحدوث فترات موجية متميزة من خلال بنية الجهاز، وتم تقييم كفاءة الجهاز بغض النظر عن وجود التوربين تحت اللوحة. تم اعتبار ما مجموعه ست فترات موجية بين 1.25 و 3.50 ثانية بارتفاع موجة 0.06 متر لستة ارتفاعات مختلفة للوحة. تسمح النتائج بتقديم توصيات نظرية حول أداء المحول. تم استخدام حجم متعدد الأطوار لنموذج السوائل من خلال نهج ثنائي الأبعاد لتفاعل الهواء والماء وتم حل معادلات الحفظ لنقل الكتلة والزخم والحجم بواسطة طريقة الحجم المحدود. سمحت نتائج التحليل بملاحظة أن أعلى ارتفاع نسبي للوحة يؤدي إلى تعزيز كفاءة اللوحة الأفقية المغمورة بين محاكاة فترات الموجة، بالإضافة إلى تحديد كفاءة الجهاز النظري بما يصل إلى ثلاثة أضعاف لفترات الموجة الأكبر مقارنة بفترات الموجة الأقصر.

Global electric energy demand is constantly growing, consequently leading towards the usage of renewable energy sources reducing pollution and increasing sustainability. The ocean is a poorly explored renewable energy source; thus, to evaluate the Brazilian wave energy budget, this study investigated the mean behaviour of the wave power rate on the south-southeastern Brazilian Shelf as well as analysed the temporal variability of the wave power rate at the most energetic locations near the coast. Three locations were examined, namely Laguna, Ilhabela and Farol Island, based on the criteria of high means and small standard deviations. The mean wave power rate was approximately 9.08 kW / m on Laguna, 10.01 kW / m on Ilhabela and 15.93 kW / m on Farol Island. The standard deviation identified in the three locations reached values of 6.47 kW / m on Laguna, 7.59 kW / m on Ilhabela and 13.51 kW / m on Farol Island. Temporal variability analysis was conducted through wavelet analysis. The results show a dominant yearly cycle with a background presence of synoptic cycles, with little deviation between the locations. The El Niño southern oscillation plays a minor role on the energy spectrum of Laguna and does not have a significant influence on Ilhabela and Farol Island.

This paper postulates that the effect of e-commerce on firm performance is not direct and needs to be examined using mediating factors. The Ordinary Least-Squares (OLS) model was employed with the data of the Flash Eurobarometer 439 Survey entitled The Use of Online Marketplaces and Search Engines by small and medium enterprises. The obtained findings provide support for the mediating hypothesis. To be more precise, while the relationship between e-commerce and firm performance is negative, it is positively mediated by certain types of internet sales channels. In particular, the benefits of e-commerce in terms of higher sales are more pronounced when firms use commercial websites and online marketplaces. On the other hand, the interaction between e-commerce and search engines has an insignificant effect on firm performance. This study advances research on e-commerce by emphasizing the importance of mediating effect.

AbstractThe present work performs a numerical analysis of the geometrical investigation of a two-dimensional channel with two alternated isothermal rectangular blocks subjected to turbulent forced convective flows. Constructal Design associated with Exhaustive Search is used to investigate the influence of the geometry of the isothermal blocks over the performance of the cooling convective flows in a multi-objective viewpoint, i.e., considering the pressure drop and heat transfer rate. The time-averaged equations of continuity, momentum, and energy conservation are solved with the finite volume method. The k–$$\omega $$ ω shear stress transport model is used for the closure of turbulence. The effect of the two proposed degrees of freedom, the height/length ratio of the two blocks ($$H_{1}/L_{1}$$ H 1 / L 1 and $$H_{2}/L_{2})$$ H 2 / L 2 ) , is analyzed in relation to the proposed objectives. Regarding the thermal purpose, the geometry with the highest insertion into the channel led to the best performance, while the opposite configuration led to the best fluid dynamic performance. This behavior was similar to that previously found in the literature for forced convective laminar flows. For a multi-objective perspective, the use of technique for order preference by similarity to ideal solution indicated that asymmetric blocks led to the best multi-objective performance when both performance indicators had the same weight.

With the growing concerns over environmental degradation and the increasing demand for sustainable materials, eco-friendly composites have gained considerable attention in recent years. This review paper delves into the promising realm of seed-based fillers, reinforcements and polysaccharidic matrices in the production of biocomposites that are yet focusing on those seeds, which can be considered industrial process waste. Seeds, with their inherent mechanical properties and biodegradability, which are often the waste of production systems, offer a compelling solution to reduce the environmental impact of composite materials. This paper explores the properties of various seeds considered for composite applications and investigates the processing techniques used to incorporate them into composite matrices. Furthermore, it critically analyzes the influence of seed fillers on the mechanical and physical properties of these eco-friendly composites, comparing their performance with traditional counterparts. The environmental benefits, challenges, and limitations associated with seed-based composites from waste seeds are also discussed, as well as their potential applications in diverse industries. Through an assessment of relevant case studies and research findings, this review provides valuable insights into the outlook of seed-based composites as a sustainable alternative in the composite materials landscape, emphasizing their role in promoting a greener and more responsible approach to materials engineering.