Airborne wind energy (AWE) has attracted increasing attention because it can access stronger and more consistent winds at higher altitudes, offering high power density with reduced material consumption. Among various AWE technologies, the parafoil-based kite power generation system is a promising option because of its lightweight structure, operational flexibility, and suitability for pumping-cycle electricity generation. However, its practical application is constrained by the difficulty of maintaining stable cyclic operation under realistic turbulent wind conditions. Existing studies have mainly focused on steady inflow conditions or limited turbulence scenarios, and the combined effects of turbulence intensity and control parameter settings on system stability remain insufficiently understood. Therefore, this study investigated the stability of a parafoil-based kite power generation system under turbulent wind fields and explored effective control parameter adjustment strategies to improve operational stability.

A coupled numerical framework was established for a pumping-cycle parafoil-based kite power generation system, incorporating parafoil aerodynamics, tether dynamics, atmospheric modeling, and dual closed-loop proportional–integral–derivative (PID) control. Parafoil aerodynamics were described using a segmented aerodynamic analysis method, the tether was modeled by the lumped-mass method, and the atmospheric model accounted for variations in wind speed and air density with altitude. Three-dimensional turbulent wind fields generated by TurbSim were imposed as inflow conditions to represent realistic atmospheric disturbances. Different turbulence intensities and target-attractor elevation angles were examined to assess their coupled effects on system stability. For each operating condition, multiple independent turbulent wind fields were simulated, yielding a total simulation time of 20 000 s. Under noncrash conditions, more than 80 complete power-generation cycles were achieved, ensuring that the conclusions were supported by sufficient statistical samples. System stability was evaluated using two indicators: the average operating duration and the average crash probability per power-generation cycle.

For all target-attractor elevation-angle settings, the average operating duration decreased progressively with increasing turbulence intensity, whereas the average crash probability per power-generation cycle increased continuously, indicating that strong turbulence significantly weakens system stability. Moreover, when the turbulence intensity reached a certain range, both the indicators exhibited accelerated deterioration, suggesting threshold-like behavior. Statistical analysis revealed that the transition stage between the power-generation phase and the recovery phase was the most vulnerable part of the pumping cycle. During this stage, the parafoil was more sensitive to aerodynamic disturbances, and lateral and vertical wind fluctuations could drive local angle-of-attack excursions beyond the normal operating range, leading to rapid aerodynamic degradation, trajectory deviation, and ultimately a crash. When fluctuations in lateral and vertical wind speeds within a 1 s timescale exceeded approximately 2.5 m/s, the system faced a pronounced crash risk. At turbulence intensities of approximately 15%–18%, such fluctuations became considerably more frequent, and the crash probability increased sharply. Under the same turbulence intensity, a higher target-attractor elevation angle generally yielded a longer operating duration and a lower crash probability, and this stabilizing effect became more pronounced under high-turbulence conditions.

The findings indicated that the stability degradation of the parafoil-based kite power generation system in turbulent wind fields is not caused by a single factor but results from the coupled interaction among parafoil aerodynamic characteristics, transient flight states, turbulent disturbances, and the limited compensation capability of a fixed-parameter PID controller. Under low to moderate turbulence, the system maintained stable pumping-cycle operation, whereas under strong turbulence, the stability deteriorated rapidly in a threshold-like manner. Appropriately increasing the target-attractor elevation angle can enlarge the flight-envelope safety margin and improve the system's tolerance to disturbance, delaying stability degradation and enhancing operational robustness. These findings offer practical guidance for control parameter selection and stable operation of parafoil-based kite power generation systems in complex wind environments.

The Manila subduction zone is the primary source of potential large tsunamis in the South China Sea, which may result in severe coastal disasters. This study aims to evaluate the tsunami hazards faced by South China Sea Islands caused by earthquakes with maximum magnitudes through assessing the earthquake with maximum possible magnitude in the Manila subduction zone and simulating the process of induced tsunamis.

The seismic potential was evaluated using the negative dislocation inversion model TDEFNODE based on GPS horizontal velocity field data. The acquired distribution of the locking and slip deficit along the Manila subduction zone was first used to assess the seismic potential. The earthquakes with a magnitude of 8.9 and a 500-year return period were selected as the maximum possible earthquake to design extreme earthquake tsunami events. This study comprehensively considered the impact of the epicenter, focal depth, and heterogeneity in the fault slip on tsunamis, and about 700 000 tsunami events under the condition of magnitude 8.9 were simulated for further evaluation. Both uniform and heterogeneous slip models were adopted to describe fault slips in the tsunami events. Considering that a larger fault slip is more likely to occur in areas with a higher degree of fault locking, the distribution of fault locking was also introduced into the heterogeneous slip model as a constraint for the random slip distribution. The tsunami events were simulated by the unit-source superposition method proposed by our group previously, which could efficiently simulate the propagation of tsunami waves based on a precomputed database and provided the offshore tsunami wave heights of major islands with small computational cost.

The findings revealed that even under the same magnitude, the height of tsunami waves exhibited significant randomness. The tsunami wave height in Dongsha Island varied between 1.8 m and 6.2 m during 8.9-magnitude earthquake tsunami events. The heterogeneity of fault slip had a significant impact on tsunami wave height, and conventional models that neglected heterogeneous slip distribution would underestimate the tsunami wave height by approximately 20%-50%. In terms of spatial distribution, with tsunami wave heights exceeding 4 m, Nanshazhou, Nandao, and Beidao in the Xuande Islands and Dongsha Islands were worst affected, while the tsunami hazard in the Nansha Islands was much smaller.

This work enhances the tsunami hazard assessment model by introducing fault locking into the random slip model as a constraint, enabling the description of the fault slip to be more realistic than the conventional uniform slip assumption. The maximum possible tsunami hazard faced by major islands in the South China Sea has been quantified, which offers effective support for tsunami hazard prevention and reduction in these islands.