When designing a wind turbine, the main objective is to generate maximum effective power with the lowest possible production costs. The power of a wind turbine depends primarily on the aerodynamic properties of its blades. Moreover, the cost of making a blade for a wind turbine, and therefore also for the entire wind turbine, depends on the materials used for its production. Therefore, wind turbine blades are the most studied element of a wind turbine. By selecting the optimal material and geometric properties of the wind turbine blade, it is possible to reduce the costs of making the entire wind turbine. These rationales led the authors to investigate composite wind turbine blades. A two-criteria optimization task was formulated, which allowed for the simultaneous consideration of two criteria: minimizing the mass and minimizing the vertical deflection of the wind turbine blade. Geometric properties of the blade, influencing the considered criteria, were assumed as decision variables. The weighted sum method was used. The results obtained allowed us to determine the optimal geometric and material properties of a wind turbine blade.

Silicones have been used as protective coatings due to their resistance to hydrolytic degradation and UV (ultraviolet) degradation. There is a growing problem with managing organic waste, which can be used as fillers in composites. This research demonstrated the use of organic waste from citrus peels, including grapefruit, lime, lemon, and orange peels. Silicone-based composites were prepared by gravity-casting using 2.5, 5, and 10 wt.% waste filler. Samples made from the composite panels were subjected to static tensile, density, hardness, pin-on-disc, and Schopper–Schlobach abrasion tests. The test results showed that lower tensile strength values characterized the composite materials compared to the silicone used as a filler. All materials had greater hardness than the silicone without the addition. At the same time, composites with a mass density of the filler of 2.5 and 5 wt.% showed more excellent abrasion resistance than the silicone used as a matrix. This research showed that the samples containing 2.5 wt.% grapefruit filler had the best mechanical properties and the lowest abrasive wear.

One of the assumptions of the zero-waste economy is to reduce the amount of industrial waste produced, process it, and recover it without burning or burying it. Citrus peels are among the food wastes that are difficult to recycle. Due to the long time of decomposition and the waxes and fats in their structure, the shells rarely end up in composters and, consequently, are not included in natural fertilisers. The assumptions fit into the research described in the article.The authors investigated the possibility of using ground peels of citrus fruits: grapefruit, key lime, lemon and orange as fillers in composite materials in which the role of the matrix was played by epoxy resin. Composite materials with 2.5, 5 and 10% filler content were prepared. The materials were tested using the tensile, hardness, and abrasive tests using the pin-on-disc method.The research was to answer whether adding citrus waste can change the physicochemical properties of composite materials based on epoxy resin and native resin. Particular attention was paid to the properties that are important from the point of view of engineering applications: mechanical properties and tribological properties.In the face of challenges related to the growing amount of waste from the food industry, joint materials engineering tries to answer whether this waste can be used in the production of composite materials. In several publications from recent years, it has been postulated that used food industry products can be used as fillers for composite materials, as they can, on the one hand, improve specific physicochemical properties of new materials and manage food waste.The tests proved that composite materials with grapefruit and key lime as a filler were characterized by the best tribological properties, mechanical properties, and hardness, which were unchanged or better than the epoxy resin used as a matrix.

High-density polyethylene fuel tanks are commonly used in the automotive industry as a crucial component for transporting and storing combustible liquids. Still, predicting their dynamic behavior with high accuracy remains demanding, considering various loading conditions during a product's life. The study presented in this paper details a modal numerical analysis of the HDPE fuel tank and how different material models, rate-independent and rate-dependent, affect the final results in linear simulations. Finite Element Analysis (FEA) performed in the ANSYS software confirmed that a more detailed rate-dependent material model used during numerical analysis provides more accurate and reliable results.

At the beginning of this chapter is a brief introduction to the issue of renewable energy sources. Next, aspects that should be considered when choosing a location of both solar photovoltaics panels and wind turbines are discussed. Afterwards, there is a brief theoretical introduction to the General Morphological Analysis (GMA), followed by practical application of GMA to optimize the structure of hybrid solar-wind system, which is preceded by a description of the adopted design assumptions. At the end of the chapter is a numerical model of a hybrid solar-wind system developed in the MATLAB/Simulink environment and analysis of the results of numerical simulations.