ABSTRACT

The present study investigates the hydrodynamic performance of an onshore land-based OWC-WEC device by analyzing its annual averaged efficiency in a random wave environment. To analyze the hydrodynamic efficiency of the wave energy converter device in a real marine environment, two different sea bed configurations, namely sloping and multi-stepped bottom, are taken into consideration. Moreover, the Pierson-Moskowitz sea spectrum, accompanied by suitable sea states, is considered to model the irregular water wave interaction with the OWC device. A major emphasis has been given to analyzing the impact of various structural configurations, on the hydrodynamic efficiency of the OWC-WEC device. The findings suggest that the local wave climate, accompanied by the suitable structural configuration, enhances the hydrodynamic performance of the U-shaped OWC device over the standard OWC device by 0.573% in 0 < Λ < 0.015..

INTRODUCTION

With the rapid growth of human civilization, the demand for energy on a global scale has increased over the last decade. In this context, harnessing energy from renewable sources has proven a significant breakthrough as an alternative to the depletion of limited sources of non-renewable energy. Out of all such renewable energy sources, the concept of harnessing energy from ocean waves has become prominent in the coastal belt and nearshore systems to transfer global energy to coastline countries (Quan et al. 2024). In this realm, there has been a growing interest in the study and utilization of wave energy through the advancement and optimization of various wave energy converter devices (Delmonte et al. 2015; Falcão and Henriques (2016)). Among such wave energy converter devices, the oscillating water column OWC device appears to be one of the prominent successful commercialized wave energy technology that basically, transforms the captured kinetic energy from the ocean waves into a usable form of energy (Heath (2012)). The mathematical modelling associated with this particular kind of WEC device has been started since 1980 (Evans (1978, 1982)), and since then, significant progress has been made by several researchers to enhance the hydrodynamic efficiency of the OWC device by considering novel structural configurations (Evans and Porter (1995); Boccotti (2003); Malara and Arena (2013); Falcão and Henriques (2016); Narendran and Vijay (2025)), incorporating different sea bed configurations such as slanted, uniform, undulated, stepped (Rezanejad et al. 2013; Ashlin et al. 2016; Vyzikas et al. 2017; Koley and Trivedi (2020); Mohapatra and Sahoo (2020); Srinu et al. 2024), increasing chambers of the device (Rezanejad et al. 2015; Ning et al. (2017); Trivedi and Koley (2022); Trivedi and Koley (2022); Trivedi and Koley (2023); Trivedi et al. (2023);). The motivation behind these aforementioned novel approaches is to enhance the performance of the OWC-WEC device in the nearshore regions by minimizing the construction cost. The ideas like changing the seabed configuration and construction of integrated structure with the breakwaters minimize the construction cost and provide improved efficiency of the OWC device due to the occurrence of various resonance phenomena (Evans and Porter (1995); Rezanejad et al. 2015; Koley and Trivedi (2020)). Further, the introduction of a multi-chamber configuration enhances the capture rate of the wave energy in the nearshore regions for a wide range of natural wave climates, which considerably enhances the energy production rate of the OWC device. Additionally, the novel idea of introducing U-shaped, L-shaped OWC devices in the nearshore marine environment has proven to enhance the hydrodynamic performance in compared to standard OWC devices (Boccotti (2007); Srinu et al. 2024). In most of the aforementioned literature, the hydrodynamic performance of the OWC device was carried out by considering the regular and oblique waves. However, a real marine environment is highly unpredictable in nature, and therefore, it is of utmost importance to investigate the hydrodynamic performance of the OWC device when the ocean waves are irregular in nature. De O Falcão and Rodrigues (2002) initially proposed a stochastic model to estimate the annual average efficiency of the OWC device in the case of random waves. Using this process, Gomes et al. (2012) analyzed the impact of geometry optimization of a floating-type OWC device under the action of irregular waves. The power extraction for both the aforementioned investigations was simulated for the wave climate conditions of the western coast of Portugal. It was reported that with the proper optimized turbine size, rotational speed, and structural configurations the annual average efficiency of the OWC device can be enhanced which can deliberately maximize the wave power extraction. Josset and Clément (2007); Koo and Kim (2010, 2012) investigated the hydrodynamic performance of a land-based OWC device using the time-domain numerical simulation. Further, Rezanejad et al. (2017, 2019) and Zabihi et al. (2019) experimentally investigated the performance of an OWC device placed over a stepped bottom for both regular and irregular waves. It was found that incident wave frequency and the turbine damping coefficients strongly influence the efficiency of the device. The Pierson-Moskowitz and JONSWAP spectrums were considered for the experimental investigations. Recently, Trivedi and Koley (2022); Trivedi and Koley (2022); Trivedi and Koley (2023), Zabihi et al. (2021) investigated the hydrodynamic performance of an OWC device under the action of random waves. To analyze the same, different structural configurations such as the breakwater-integrated structure comprising LIMPET and quarter circle structured OWC device, multi-stepped bottom profile and undulated seabed configuration are considered. Further, to investigate the irregular waves, the well-known Brettschneider spectrum is taken into consideration. It is reported that with the adoption of suitable structural and turbine configurations, the hydrodynamic performance of the OWC device can be significantly enhanced.

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