Testing and control of a power take-off system for an oscillating-water-column wave energy converter

Henriques, J.C.C.; Gomes, R.P.F.; Gato, L.M.C.; Falcão, A.F.O.; Robles, Eider; Ceballos, Salvador

doi:10.1016/j.renene.2015.07.015

Cited by 146 publications

(39 citation statements)

References 25 publications

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“…As it has been suggested, for wave energy converters, their capacity of PTO and generator will be limited for both the cost of the components and the energy conversion efficiency. Babarit et al [51] proposed that the maximal PTO power (PTO rated power) can be set to 20 times the mean annual absorbed power, and Henriques et al [52] indicated that to reduce the losses of the PTO system at partial load, the recommended generator with a rated power is twice the maximal expected average power conversion. All these have suggested that limited maximal PTO power and generator must be applied for practical purposes.…”

Section: Discussionmentioning

confidence: 99%

Energy Conversion: A Comparison of Fix- and Self-Referenced Wave Energy Converters

Sheng

Lewis

2016

Energies

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Abstract:The paper presents an investigation of fix-referenced and self-referenced wave energy converters and a comparison of their corresponding wave energy conversion capacities from real seas. For conducting the comparisons, two popular wave energy converters, point absorber and oscillating water column, and their power conversion capacities in the fixed-referenced and self-referenced forms have been numerically studied and compared. In the numerical models, the device's power extractions from seas are maximized using the correspondingly optimized power take-offs in different sea states, thus their power conversion capacities can be calculated and compared. From the comparisons and analyses, it is shown that the energy conversion capacities of the self-referenced devices can be significantly increased if the motions of the device itself can be utilized for wave energy conversion; and the self-referenced devices can be possibly designed to be compliant in long waves, which could be a very beneficial factor for device survivability in the extreme wave conditions (normally long waves). In this regards, the self-referenced WECs (wave energy converters) may be better options in terms of wave energy conversion from the targeted waves in seas (frequently the most occurred), and in terms of the device survivability, especially in the extreme waves when compared to the fix-referenced counterparts.

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Section: Discussionmentioning

confidence: 99%

Energy Conversion: A Comparison of Fix- and Self-Referenced Wave Energy Converters

Sheng

Lewis

2016

Energies

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“…This power law has been proposed in Falcão (2002) and adopted as a rotational speed control law in other papers (e.g. Falcão and Henriques 2014a; Falcão et al 2014b;Henriques et al 2016). The constants of the straight lines in Fig.…”

Section: Power Performancementioning

confidence: 97%

Air turbine optimization for a bottom-standing oscillating-water-column wave energy converter

Falcão

Henriques

Gato

2016

J. Ocean Eng. Mar. Energy

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The oscillating-water-column wave energy device equipped with an air turbine is widely regarded as the simplest and most reliable, and the one that was object of the most extensive development effort. The aerodynamic performance of the air turbine plays a major role in the success of the technology. A case study was selected to investigate these issues: the existing bottom-standing plant on the shoreline of the island of Pico, in Azores Archipelago. The overall performance of the OWC plant was modelled as an integrated hydrodynamic and aerodynamic process. The hydrodynamic modelling was based on linear water wave theory. Published results from model testing of Wells and biradial turbines, together with well-known tools from dimensional analysis, were employed to determine the aerodynamic performance, and to optimize the turbine size and rotational speed. Singleand two-stage Wells turbines were considered. Unlike the biradial turbine, the performance of the Wells turbine, especially the single-stage version, was found to be severely affected by the constraints on rotor-blade tip speed (to avoid excessive centrifugal stresses and shock waves in the more energetic sea states). A power law, relating instantaneous values of the electromagnetic torque and the rotational speed, was found to apply to both types of turbines as a rotational speed control algorithm. The large runaway speed of the Wells turbine was found to be a risk to turbine integrity by excessive centrifugal stresses that requires safety measures. The much lower runaway speed of the biradial turbine is not expected to be a major problem.

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“…For example, J.C.C. Henriques et al developed a PTO control of an oscillating-water-column spar-buoy wave energy converter, and hardware-in-the-loop simulation is used in experiments to characterise the proposed control algorithms [25]; Jorgen Hals et al proposed model-predictive controller to exploit the full absorption potential of wave-energy converters; N.M. Tom et al used the Pseudo-spectral control which allows optimising the controller design to achieve the optimisation of the output power of an oscillating surge WEC. Other exploration of control strategy could be seen in [26] electrical control, adaptive control in [27], phase control in [28].…”

Section: Figure 3 Ocean Energy Technology International Patent Coopermentioning

confidence: 99%

An innovative generic platform to simulate real-time PTO damping forces for ocean energy converters based on SIL method

2018

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This paper proposes a generic PTO (power-takeoff) simulation platform which can be used to predict how devices perform in wave conditions when a simulated real-time linear or non-linear PTO damping forces is employed. The experimental platform could be used to investigate the maximum power output of wave converters(WECs) without constructing a physical PTO system and complex control strategies at the design stage of a WEC, thus making it efficient and inexpensive to explore different PTO solutions. For this purpose, a software-in-the-loop (SIL) simulation method is adopted which uses an innovative control loop running on an inexpensive real-time controller coupled to a DC motor which simulates the PTO damping torque. To calibrate the proposed PTO simulation platform, 1349 drop tests are carried out. A series of relationship curves and corresponding equations are drawn for both the linear and non-linear PTO cases. Moreover, correlation curves for input gains and the produced damping force coefficients are provided. The correlation indicates the PTO simulation platform's capacity of simulating linear PTO can reach 40-220 and can reach 10-70 for quadratic damping in terms of damping force coefficient. To investigate the accuracy of the platform, uncertainty analyses are also carried out in good details. The calibrating tests and uncertainty analyses indicate that the proposed experimental platform can be used to overcome many of the limitations in modelling PTO systems at laboratory scale to simulate both real-time linear and quadratic PTO damping forces.

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Testing and control of a power take-off system for an oscillating-water-column wave energy converter

Cited by 146 publications

References 25 publications

Energy Conversion: A Comparison of Fix- and Self-Referenced Wave Energy Converters

Energy Conversion: A Comparison of Fix- and Self-Referenced Wave Energy Converters

Air turbine optimization for a bottom-standing oscillating-water-column wave energy converter

An innovative generic platform to simulate real-time PTO damping forces for ocean energy converters based on SIL method

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