Optimum power analysis of a self-reactive wave energy point absorber with mechanically-driven power take-offs

Journal Article · Fri Jan 17 00:00:00 EST 2020 · Energy (Oxford)

DOI:https://doi.org/10.1016/j.energy.2020.116927· OSTI ID:1659132

Li, Xiaofan ^[1]; Liang, Changwei ^[2]; Chen, Chien-An ^[3]; Xiong, Qiuchi ^[3]; Parker, Robert G. ^[4]; Zuo, Lei ^[3]

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1. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Virginia Tech
2. Stony Brook Univ., NY (United States)
3. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
4. Univ. of Utah, Salt Lake City, UT (United States)

This paper studies a self-reactive ocean wave energy converter (WEC) where energy is absorbed through the relative motion between a floating buoy on the ocean surface and a submerged body. Two types of direct-drive power take off (PTO) systems are examined. One adopts a ball screw system in inverse driving mode with mechanical motion rectifier (MMR) that converts the oscillating bi-directional input heave motion into unidirectional rotation to drive an electromagnetic generator, and another one uses a ball screw system to directly drive the generator (called non-MMR). Dynamic models for both types of PTOs are established and integrated with the overall WEC system model in both the time and frequency domains. Numerical simulation is used to investigate the dynamic performance of both PTOs. The influences of the PTO inerter, which is from the rotational inertia of the flywheel and generator, and the WEC drag damping coefficient are discussed and explored. The analytical closed-form solution for the optimum condition of the non-MMR system is derived based on the criterion of maximum power absorption, and numerical simulation yields the optimum condition for the MMR system. Overall, the results under regular and irregular waves show that the PTO inerter in the MMR system can improve the power absorption for small wave periods and maintain the same performance for large wave periods. The PTO inerter in the non-MMR system shifts the peak frequency. The WEC drag damping negatively influences the power absorption in both PTO systems, especially at large wave periods.

• Research Organization: Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE; USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Water Power Technologies Office
• Grant/Contract Number: EE0007174
• OSTI ID: 1659132
• Alternate ID(s): OSTI ID: 1598373
• Journal Information: Energy (Oxford), Journal Name: Energy (Oxford) Vol. 195; ISSN 0360-5442
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

16 TIDAL AND WAVE POWER
Energy optimization
Ocean wave energy
Power take-off