Rapid advancements in renewable energy technologies have been primarily driven by the increasing global energy demand for energy and the growing concerns over environmental pollution. Among these technologies, tidal current energy has achieved significant attention due to its high energy density and stable energy output. Compared to other renewable energy sources, such as solar and wind power, tidal current energy is more stable and predictable, offering considerable potential for integration into future energy systems. However, despite its promise, several key technological challenges must be addressed to enable the widespread development of tidal current energy technology. To address these challenges, this paper presents a comprehensive review of recent advancements in ocean tidal current energy technology, with particular emphasis on the analysis of the main types of energy harvesting devices and support structures. Furthermore, it evaluates representative tidal current energy devices based on their operational principles, technical features, and applications. By systematically reviewing mainstream hydrodynamic analysis methods, this paper evaluates their applicability and limitations in assessing the performance of tidal current energy devices. This assessment improves the accuracy of performance predictions and offers theoretical support for the optimal design of the energy harvesting systems. In addition, the paper addresses key issues in the development of tidal current energy technology, including technological feasibility, cost management, and environmental impact. These discussions provide a foundation for identifying emerging trends and major technical challenges in the field. Finally, the development prospects of tidal current energy technology are explored from the perspectives of technological advancement, economic viability, and sustainability. It is concluded that achieving widespread adoption of tidal current energy depends on factors such as technological maturity, effective cost control, and the balanced integration of environmental and social benefits.

In the context of global carbon peaking and carbon neutrality goals, the development of clean energy technologies has become a strategic priority for the global community. As a significant source of renewable energy, tidal current energy is playing an increasingly important role in reshaping the global energy landscape. To address the critical scientific challenge presented by the wake effects induced by tidal turbines, this study introduces a high-precision Lagrangian dynamic (LD) sub-grid-scale model within the framework of large-eddy simulation (LES). By integrating the actuator-line model with the aforementioned LD–LES approach, a solver named JUST–FOAM–Turbine is developed, specifically tailored for high-fidelity wake simulations of horizontal-axis tidal turbines (HATTs). The solver's computational accuracy is validated against experimental data obtained from laboratory-scale HATT tests. Subsequently, the solver is employed to analyze the wake dynamics of the HATT under various tip speed ratios (TSRs). The findings are summarized as follows: (1) At low TSRs, the blade operates at a high angle of attack, increasing its susceptibility to stall and flow separation. At high TSRs, the blade experiences a low angle of attack, resulting in a reduced lift coefficient. In contrast, within the optimal TSR range, which corresponds to the blade's primary operational regime, the angle of attack is maintained near the critical value, thereby maximizing the turbine's power output. (2) As the TSR increases, the wake instability of the turbine intensifies, and the wake meandering phenomenon becomes more pronounced. The wake expansion downstream of the turbine is primarily driven by the blockage effect. Further downstream, the wake continues to widen laterally, resulting in an increased expansion width. (3) At a downstream distance of 6D, the wake effect begins to weaken due to momentum exchange between the low-speed region of the wake and the high-speed region of the surrounding water. The radial velocity gradient of the wake decreases significantly. When considering the turbine array layout, it is recommended to position additional turbines downstream beyond 6D. (4) As the TSR increases, the attached vortex on the turbine disk progressively disintegrates, forming small-scale, weaker vortex structures. The third-generation vortex identification method implemented in this study is threshold-independent and effectively captures both strong and weak vortex structures in the turbine wake simultaneously.

A single-phase Three-Level Split-Inductor Neutral Point Clamped Inverter-Improved (3L-SI-NPCI ² ) for transformerless photovoltaic (PV) application is proposed in this article. The proposed inverter utilizes two split inductors, which eliminate the shoot-through issue. Therefore, it is more reliable than conventional converters. Not needing dead time, achieving a high efficiency with lower current THD and low leakage current are other advantages of the proposed inverter. The operation principle, dynamic performance, output filter design and impacts of asymmetric filter inductors on leakage current are illustrated in the 3L-SI-NPCI ² . The proposed topology is compared to seven existing transformerless topologies by simulation studies and results. Finally, an experimental prototype has been developed to show the benefits of the proposed inverter.