A lumped parameter model to explain the cause of the hysteresis in OWC-Wells turbine systems for wave energy conversion

Ghisu, Tiziano; Cambuli, Francesco; Puddu, Pierpaolo; Virdis, Irene; Carta, M.; Licheri, Fabio

doi:10.1016/j.apor.2019.101994

Cited by 16 publications

(8 citation statements)

References 47 publications

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“…The assumptions, derivation and analytical solution of the LPM by Peng and his coauthors is presented in Section 2 of [1]. The authors proposed an LPM to describe the behavior of a generic OWC system, by applying the conservation of mass to the OWC air chamber and the conservation of momentum inside the turbine duct, following the same methodology previously introduced by ourselves in [2,3]. In fact, in addition to using a schematic for the OWC system (figure 2b in [1]) that is remarkably similar to the one shown in figure 1 of [2], the model equations 6, 7 and 8 in [1] are the same as equations 4, 5 and 6 in [2].…”

Section: Similarities Between the Lpm Model Presented By Peng Hu And ...mentioning

confidence: 99%

“…In their paper [1], Peng, Hu and Yang presented a lumped parameter model (LPM) to quantify the hysteresis in Oscillating Water Column (OWC) systems. We could not avoid noticing that the assumptions at its origin, the derivation of the LPM and the methodology used to obtain an analytical solution (after linearization) are remarkably similar to the ones presented in some of our published works [2,3,4], none of which were referenced in [1]. The similarities between the model presented by Peng and his coauthors and the model published by ourselves are significant, to the point that we find hard to believe that they could have derived it authonomously.…”

Section: Introductionmentioning

confidence: 99%

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Discussion on “Influence of incoming wave conditions on the hysteretic behavior of an oscillating water column system for wave energy conversion” by J. Peng, C. Hu and C. Yang

Ghisu,

Cambuli,

Puddu

et al. 2023

Ocean Engineering

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Section: Similarities Between the Lpm Model Presented By Peng Hu And ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Discussion on “Influence of incoming wave conditions on the hysteretic behavior of an oscillating water column system for wave energy conversion” by J. Peng, C. Hu and C. Yang

Ghisu,

Cambuli,

Puddu

et al. 2023

Ocean Engineering

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“…Due to the rig structure, it was not possible to use standardized instruments to measure the flow rate, Q. This was evaluated based on the piston motion, taking into account the time delay between the piston velocity and the corresponding flow speed at the rotor inlet, due to the presence of the chamber volume [13,14,15,16].…”

Section: Owc Rig and Instrumentationmentioning

confidence: 99%

Wells turbine efficiency improvements: experimental application of a speed control strategy

Licheri¹,

Ghisu²,

Cambuli³

et al. 2022

J. Phys.: Conf. Ser.

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Systems based on the OWC principle allow to convert the sea-wave energy into electrical energy. The potential energy contained in the wave motion is first converted into the pneumatic energy of a bi-directional airflow, generated by the oscillatory displacement of a column of water inside a chamber. Then, an air turbine, such as the Wells turbine, placed at the top of the chamber, converts the pneumatic energy into mechanical energy at its shaft, which can be coupled to an electric motor to produce energy. The turbine’s performance is strongly affected by the non-stationary behavior of the airflow, which continuously changes its intensity. Control solutions based on the variation of the turbine rotational speed can overcome this limitation. This work aims to study a speed-controlled Wells turbine with an experimental approach, making use of a turbine coupled to an Oscillating Water Column (OWC) simulator. A control law for the rotational speed has been defined and applied to the turbine in order to move the turbine’s operating conditions as close as possible to its maximum efficiency point, for the majority of the piston period. The experimental results prove the effectiveness of the proposed control strategy for moving the operating conditions and for obtaining operating conditions close to the best efficiency point for the majority of the wave period.

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“…The volumetric flow rate has been calculated using the axial velocity distribution along the blade span, measured with the aerodynamic probe. Although this method is more complicated than the estimation based on piston speed, it is necessary to eliminate the delay [18] between the piston velocity and flow speed at the turbine inlet induced by the presence of the chamber volume.…”

Section: Turbine Performancementioning

confidence: 99%

Experimental analysis of the unsteady flow inside a Wells turbine

et al. 2021

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One of the most promising technologies for sea-wave energy conversion is the one based on the Oscillating Water Column (OWC) principle. The system is composed of two units, an open chamber that converts the sea water motion into an alternating air-flow, and a turbine driven by the latter. The alternating flow of air requires a turbine capable of maintaining the same direction of rotation. The Wells turbine represents the simplest and most reliable device for this purpose. It is a self-rectifying axial turbine characterized by a rotor with symmetric blades staggered at 90 degrees relative to the axis of rotation. The vast majority of experimental works on Wells turbines and OWC devices analyzed their performance from a global point of view, often under steady conditions, in order to evaluate the pressure drop through the rotor, the torque produced and thus the turbine efficiency. This paper presents an experimental analysis of the three-dimensional flow inside a Wells turbine which operates in a facility capable of reproducing the alternating air-flow typical of an OWC system. The investigation is based on local flow measurements using several probes in order to describe the non-stationary air-flow, both up- and down-stream of the rotor at different heights, along the span of the blade. The investigation, conducted on a high-solidity turbine, details the behavior of the flow field inside the machine, aiming to provide a detailed description that can guide the aerodynamic optimization of the entire system (chamber and turbine) for a better energy conversion.

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A lumped parameter model to explain the cause of the hysteresis in OWC-Wells turbine systems for wave energy conversion

Cited by 16 publications

References 47 publications

Discussion on “Influence of incoming wave conditions on the hysteretic behavior of an oscillating water column system for wave energy conversion” by J. Peng, C. Hu and C. Yang

Discussion on “Influence of incoming wave conditions on the hysteretic behavior of an oscillating water column system for wave energy conversion” by J. Peng, C. Hu and C. Yang

Wells turbine efficiency improvements: experimental application of a speed control strategy

Experimental analysis of the unsteady flow inside a Wells turbine

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