Natural sources of green energy include sunshine, water, biomass, geothermal heat, and wind. These energies are alternate forms of electrical energy that do not rely on fossil fuels. Green energy is environmentally benign, as it avoids the generation of greenhouse gases and pollutants. Various systems and equipment have been utilized to gather natural energy. However, most technologies need a huge amount of infrastructure and expensive equipment in order to power electronic gadgets, smart sensors, and wearable devices. Nanogenerators have recently emerged as an alternative technique for collecting energy from both natural and artificial sources, with significant benefits such as light weight, low-cost production, simple operation, easy signal processing, and low-cost materials. These nanogenerators might power electronic components and wearable devices used in a variety of applications such as telecommunications, the medical sector, the military and automotive industries, and internet of things (IoT) devices. We describe new research on the performance of nanogenerators employing several green energy acquisition processes such as piezoelectric, electromagnetic, thermoelectric, and triboelectric. Furthermore, the materials, applications, challenges, and future prospects of several nanogenerators are discussed.

Structural failures in the barge midship sections can cause operational delay, sinking, cargo loss and environmental damage. These failures can be generated by the barge and cargo weights, and wave load effects on the midships sections. These load types must be considered in the design of the barge midship sections. Here, we present the structural analysis of a barge midship section that has decreased up to 36.4% of its deck thickness caused by corrosion. This analysis is developed using finite element method (FEM) models that include the barge and cargo weights, and wave load effects. The FEM models regarded three cargo tanks in the midship section, containing the main longitudinal and transverse structural elements. In addition, the hull girder section modulus and the required deck thickness of the barge were calculated using Lloyd’s Register rules. These rules were applied to estimate the permissible bending stresses at deck and bottom plates under sagging and hogging conditions, which agreed well with those of the FEM models. Based on FEM models, the maximum compressive normal stress and von Mises stress of the hull girder structure were 175.54 MPa and 215.53 MPa, respectively. These stress values do not overcome the yield strength (250 MPa) of the barge material, allowing a safe structural behavior of the barge. The structural modeling of the barge midship section can predict its structural behavior under different sagging and hogging conditions, considering the cargo, weight and wave loads.

Offshore cranes placed on the surface of Floating Production Storage and Offloading (FPSO) vessels affect the structural response of their main decks, which can alter the safe operation of the FPSO vessels. Generally, classification societies rules are used to predict the structural strength of the main deck of FPSO vessels. However, these classification societies rules are limited to estimate the variation of the structural performance of the main deck caused by the operation of offshore cranes under different hydrodynamic conditions. Here, we present a methodology to determine the alteration of the structural behavior of a main deck of FPSO vessel due to different operation conditions of a board offshore crane. This methodology considers the hydrodynamic response for two ultimate limit states: operating and storm conditions from 1000 m water depth in Gulf of Mexico with a return period of 10 and 100 years, respectively. The methodology includes finite element method (FEM) models of the main deck supporting an offshore crane to predict its structural response. The maximum von Mises stress of the main deck does not overcome its maximum permissible stress, which allows a safe operation of the FPSO crane. The proposed methodology can be used to estimate the structural behavior of main decks of FPSO vessels that are modified for supporting offshore cranes, regarding the hydrodynamic response for each FPSO under the operation and extreme conditions in its location. Thus, naval designers could select the better structural modifications of the main decks that decrease their costs of construction and maintenance.

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The sloshing effect of fluid storage tanks of a Floating Liquefied Natural Gas (FLNG) vessel causes variations in its global motion response. These acceleration and motion alterations can affect the safe performance of the FLNG vessels. The classification societies’ rules are employed to standardize the storage tanks’ configuration of FLNG vessels. Herein, we report a methodology to assess the sloshing effect on the global motion response of an FLNG vessel considering four geometrical arrangements of tanks and different fluid filling fractions. This methodology includes the hydrodynamic effect in operating and storm conditions from the Gulf of Mexico using a return period of 100 years. In addition, our methodology considers the influence of the internal fluid of each tank to estimate the accelerations and motions of the vessel. This methodology can be implemented to estimate the stability of an FLNG vessel under different environmental conditions. Thereby, the naval engineers could choose the best geometrical configuration of the storage tanks for safe behavior of a vessel under different operating and extreme environmental conditions.

Los buques de apoyo para plataformas de la industria petrolera tienen versatilidad de operación y capacidad de modificación estructural. Este artículo presenta una propuesta de instalación de una grúa sobre orugas sobre la cubierta principal de un buque de apoyo a plataformas petroleras, el cual realizará operaciones de mantenimiento en mar adentro. Esta propuesta incluye los resultados del análisis estructural de la cubierta principal, donde se considera el refuerzo con dos vigas NVA36. Este análisis estructural incorpora la integridad de la cubierta principal considerando la grúa y las cargas mediante modelos del método de elementos finitos (MEF). Los resultados obtenidos muestran que la cubierta principal requiere el refuerzo propuesto para disminuir las tensiones máximas de Von Mises hasta 218,71 MPa para la estructura de la cubierta principal y 201,67 MPa en las vigas de refuerzo. Estas tensiones máximas no superan las tensiones admisibles y de fluencia del material de la cubierta principal. El refuerzo de la cubierta principal que soporta la grúa sobre orugas permite la operación segura del buque de apoyo mar adentro.