A Theoretical and Experimental Investigation of Non-Linear Vibration Energy Harvesting from Broadband Excitations in Nigerian Oil Production Platform Environments

Offshore oil production platforms operated by international oil companies in the Nigerian Deep Offshore present a mechanically rich vibration environment generated by machinery, wave loading, and structural resonances, creating a potential ambient energy source for powering wireless sensor networks used in platform structural health and process monitoring applications. Linear resonant vibration energy harvesters are known to exhibit severely reduced power output under the broadband and non-stationary excitation spectra characteristic of offshore platform environments. This dissertation presents a theoretical and experimental investigation of non-linear vibration energy harvesting architectures, specifically bistable and hardening Duffing oscillator configurations, for maximizing power extraction from broadband offshore platform excitations. A non-linear stochastic dynamics framework is developed for analysing harvester response to offshore platform vibration modelled as non-stationary coloured Gaussian noise with spectral parameters derived from accelerometer measurements on an FPSO vessel operating on the Agbami deepwater field. Fokker-Planck equation analysis and Monte Carlo simulation are combined to characterize the probability density of harvested power for various harvester non-linearity parameters. Experimental harvester prototypes are fabricated using piezoelectric bimorphs with tunable magnetic non-linearity mechanisms and subjected to laboratory vibration excitation reproduced from the measured FPSO acceleration data. The bistable harvester achieves 3.4 times higher average power output than a tuned linear harvester under realistic broadband FPSO excitation at the same proof mass and piezoelectric volume. A multi-harvester array topology is proposed and theoretically analysed for improved power extraction robustness across a wider excitation intensity range. Keywords: vibration energy harvesting, non-linear dynamics, offshore platform, broadband excitation, wireless sensor network