scholarly journals Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter

2016 ◽  
Author(s):  
Nathan M. Tom ◽  
Yi-Hsiang Yu ◽  
Alan D. Wright ◽  
Michael Lawson
Keyword(s):  
Wave Energy ◽  
Reactive Power ◽  
Load Ratio ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
The Novel ◽  
Energy Converter ◽  
Power Requirement ◽  
Power Absorption ◽  
Structural Loading

The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of the controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.

Dynamics and Power Absorption of a Self-React Wave Energy Converter With Mechanical Power Takeoff System

2017 ◽  
Author(s):  
Changwei Liang ◽  
Xiaofan Li ◽  
Dillon Martin ◽  
Adam Wise ◽  
Robert Parker ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Ball Screw ◽  
Regular Waves ◽  
Energy Converter ◽  
Power Absorption ◽  
Optimal Power ◽  
Submerged Body ◽  
Equivalent Mass

A self-react wave energy converter which consists of a floating buoy and a submerged body is studied in this paper. The energy is extracted through the relative motion of the floating buoy and submerged body. Two kinds of power takeoff (PTO) system, which is the technique approaches to extract energy from the ocean, are considered for the proposed wave energy converter. One is a ball screw system with mechanical motion rectifier gearbox (which is called MMR system) and another one is solely a ball screw system (which is called non-MMR system as a comparison). The design of the proposed wave energy converter is presented and the model for both power takeoff systems are established based on their mechanisms. A time domain method is adopted to investigate the dynamics and power absorption for the proposed wave energy converter. The effect of equivalent mass on the optimal power and corresponding optimal power takeoff damping are studied both in regular and irregular waves. It is found that the equivalent mass plays different roles in the MMR system and non-MMR system. Due to the disengagement in MMR system, the equivalent mass helps to increase the power absorption at small wave 1periods, both in regular waves and irregular waves. The uncertainty of the drag coefficient on the power absorption of MMR system and non-MMR system is also investigated.

scholarly journals Experimental Analysis of a Novel Adaptively Counter-Rotating Wave Energy Converter for Powering Drifters

2019 ◽  
Vol 7 (6) ◽  
pp. 171 ◽  
Author(s):  
Guoheng Wu ◽  
Zhongyue Lu ◽  
Zirong Luo ◽  
Jianzhong Shang ◽  
Chongfei Sun ◽  
...  
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Surface Velocity ◽  
Small Scale ◽  
Power Constraint ◽  
Energy Converter ◽  
Wave Tank ◽  
Wide Range ◽  
Rotating Wave

Nowadays, drifters are used for a wide range of applications for researching and exploring the sea. However, the power constraint makes it difficult for their sampling intervals to be smaller, meaning that drifters cannot transmit more accurate measurement data to satellites. Furthermore, due to the power constraint, a modern Surface Velocity Program (SVP) drifter lives an average of 400 days before ceasing transmission. To overcome the power constraint of SVP drifters, this article proposes an adaptively counter-rotating wave energy converter (ACWEC) to supply power for drifters. The ACWEC has the advantages of convenient modular integration, simple conversion process, and minimal affection by the crucial sea environment. This article details the design concept and working principle, and the interaction between the wave energy converter (WEC) and wave is presented based on plane wave theory. To verify the feasibility of the WEC, the research team carried out a series of experiments in a wave tank with regular and irregular waves. Through experiments, it was found that the power and efficiency of the ACWEC are greatly influenced by parameters such as wave height and wave frequency. The maximum output power of the small scale WEC in a wave tank is 6.36 W, which allows drifters to detect ocean data more frequently and continuously.

Sign in / Sign up

Export Citation Format

Share Document