Due to the wide usability of thermoelectric generators (TEG) in the industry and research fields, it is plausible that mismatching conditions are present on the thermal surfaces of a TEG device, which induces negative-performance effects due to uneven surface temperature distributions. For this reason, the objective of this study is to characterize numerically the open-circuit electric output voltage of a TEG device when a mismatching condition is applied to both the cold and hot sides of the selected N and P-type semiconductor material ${\mathrm{Bi}}_{0.4}{\mathrm{Sb}}_{1.6}{\mathrm{Te}}_3$. A validated numerical simulation paired with a parametric study is conducted using the Thermal-Electric module of ANSYS 2020 R1, for which different thermal boundary and mismatching conditions are applied while considering the temperature-dependent thermoelectrical properties of the N and P-type material. The results show an inverse relationship between the open-circuit voltage and the mismatching temperature difference. When a mismatching condition is applied on the hot side of the TEG device, the temperature-dependent electrical resistance has lower values, deriving in higher voltage results (linear tendency) compared to a mismatching condition applied to the cold side (non-linear tendency).

Thermoelectric generators are devices that transform thermal energy into electric energy. These devices play an influential role in our constantly developing civilization due to their energy conversion capabilities and advantages over other conventional methods. The material properties and thermoelectric phenomena are paramount to the design process of such devices. The design process must have a complex tool to model all the thermoelectric phenomena, such as, for example, the commercial numerical code of Ansys Mechanical. However, these numerical tools can be methodologically and computationally demanding. Thus, this study aims to develop a methodology through which to characterize thermoelectric generators by using a simplified one-dimensional numerical model that considers temperature-dependent N- and P-type material properties and convective heat losses. The proposed model’s results are compared and validated to a single thermoelectric leg and a complete thermoelectric commercial module, both modeled in Ansys Thermal-Electric. These results consider the different values for electric and thermal loads as current densities, electric resistivities, and heat transfer coefficients. The main result of this study is the correct prediction of the output voltage and output power given by the one-dimensional proposed model, which was validated against a comprehensive model and the commercial thermoelectric module’s information. Therefore, the proposed methodology of this study provides a deeper understanding of the thermoelectric energy conversion process, and it can guide the design and optimization of thermoelectric generators for practical applications.

Hydraulic turbines have become indispensable for harnessing renewable energy sources, particularly in-pipe hydraulic turbine technology, which leverages excess energy within pipeline systems like drinking water distribution pipes to produce electrical power. Among these turbines, the propeller-type axial turbine with circular blades stands out for its efficiency. However, there is a notable lack of literature on fluid dynamics and structural behavior under various operational conditions. This study introduces a comprehensive methodology to numerically investigate the hydraulic and structural responses of turbines designed for in-pipe installation. The methodology encompasses the design of circular blades, followed by parametric studies on fluid dynamics and structural analysis. The circular blade’s performance was evaluated across different materials, incorporating static, modal, and harmonic response analyses. Results showed that the circular blade achieved a peak hydraulic efficiency of 75.5% at a flow rate of 10 l/s, generating 1.86 m of head pressure drop and 138 W of mechanical power. Structurally, it demonstrated a safety factor exceeding 1 across the entire hydraulic range without encountering resonance or fatigue issues. This research and its methodology significantly contribute to advancing the understanding of designing and assessing the fluid dynamic behavior and structural integrity of circular blades in axial propeller-type turbines for in-pipe installations, serving as a valuable resource for future studies in similar domains.

In-pipe hydraulic turbines are a promising energy-harvesting technology. Recent studies have demonstrated a strong influence of the turbine blade number on the performance of an axial propeller-type turbine. However, limited research has been dedicated to turbine diameters less than 100 mm. Therefore, this research aimed to determine the effect of the number of blades on the hydrodynamic performance of a 75.3 mm diameter axial propeller turbine for in-pipe installation. A parametric numerical study was performed by varying the angular velocity from 1600 to 3800 rpm and the number of blades from 2 to 6. Results identified an inverse correlation between the hydraulic efficiency of the turbine and its blade number and a direct correlation between the pressure head and the turbine torque. Furthermore, the performance showed hydraulic behavior comparable to those found in literature, confirming a similar hydraulic behavior as turbines with diameters exceeding 100 mm. Additionally, the turbine’s internal flow behavior was analyzed by visualizing the vortex structure using the Q-criterion. Lastly, this study provides a deeper understanding of the effect of the number of blades on the hydrodynamic performance of an axial turbine for in-pipe installation.

This paper presents the mathematical modeling, fluid dynamic analysis, and experimental analysis of a spiral case without guide vanes. Using a specific case of the Archimedes spiral, the model eliminates the need for fixed or moving blades to simplify the design, manufacturing, and maintenance process of the turbomachine by reducing the number of system components while preserving the fluid dynamic performance of a turbomachine operating in turbine mode. The potential flow theory is used as a mathematical basis for developing a computational code that allows the automatic generation of the curves that define the geometry of the spiral chamber, simplifying the CAD modeling process. Finally, the process is validated numerically and experimentally under different operating conditions, reaching an average error percentage between numerical and experimental analysis of 5.893% of speed and 11.089% of pressure, guaranteeing the accuracy of the model.

This study numerically evaluated the effect of internal structural optimization on the moment of inertia and self-starting behavior of an H-Darrieus hydrokinetic turbine with a NACA 0018 blade profile. A one-way fluid--structure interaction (FSI) methodology based on CFD--FEA coupling was implemented under transient operating conditions representative of hydrokinetic systems. Pressure contours obtained from CFD simulations were transferred to structural analyses to determine the critical loading condition and perform topology optimization of the blade internal structure. The optimization process preserved the external hydrodynamic profile while redistributing internal material through a rib-based reinforcement strategy derived from cooperating-section analysis. The optimized configuration achieved safety factors above 1.3 while reducing blade mass by 81.71\% and total turbine mass by 39\%. Consequently, the rotor moment of inertia decreased from 25.5858 to 7.7831 $kg\cdot m^{2}$, reducing the estimated self-starting time from 1.8 s to 0.55 s. Modal and harmonic analyses confirmed the absence of critical resonance conditions under the evaluated operating range. Additionally, the optimized design reduced embodied energy and greenhouse gas emissions associated with turbine manufacturing. The results demonstrate that internal structural optimization is an effective strategy for improving the dynamic and sustainable performance of H-Darrieus hydrokinetic turbines.