Triboelectric nanogenerators high-frequency assessment for wind-generated wave spectrum by the novel four-parameter log-integral Weibull extrapolation scheme

Accurate assessment of in-situ wave Power Spectral Density (PSD) is crucial for a wide range of renewable energy engineering and sensor applications, as it provides a detailed breakdown of how wave energy is distributed across different frequencies. PSD essentially acts as a "fingerprint" of the quasi-stationary sea state, constituting vital input to the analysis of wave energy converters, dynamics of coastal structures, and planning marine operations, based on ambient spectral wave characteristics. The goal of high-frequency wave energy harvesting, e.g., powering marine sensor networks, is to capture and transform energy from ocean waves' higher frequency components, which are often more reliable and constant than lower frequency waves. This study aims to assist in finding a viable way to power small-scale applications such as maritime sensors, e.g., small-scale wave energy offshore harvesters that are built to utilize higher frequencies. At frequencies within the range f > 0.5 Hz, PSD exhibit notable deviation from the f − 5 saturation relation, derived by Phillips (Phillips, O., 1958). As earlier studies have shown, the above-mentioned deviation increases with wind speed, suggesting that the capillary range may not possess a saturation limit. Numerous experimental results support the latter inaccuracy of Phillips' spectral formulation for wave frequencies f > 0.5 Hz. In this investigation, the authors have utilized field-measured wave height data from the Datawell Directional WaveRider Mk III buoy with a measurement (sampling) frequency f s = 1.28 Hz. The current study outlines a novel nonlinear spectral extrapolation scheme, suitable for a wide range of measured wave-related processes. Four-parameter Weibull scheme has been utilized to extrapolate the PSD tail towards higher frequencies f > 0.5 Hz. The presented extrapolation scheme yielded results consistent with high-frequency resolution laboratory tests, thus providing a tool for Phillips PSD correction. In the case of ocean buoys, a potential energy harvesting opportunity is omnipresent: wave energy. Abundant, predictable, yet consistent, the ocean’s own waves can be utilized to power navigation buoys. This research shows that the advocated novel wave spectrum assessment method, applied to a single, half-hour wave elevation record, agrees qualitatively with high-frequency wave gauge measurements from (Kondo et al., 1973).