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Abstract Technologies to enhance the survivability of wave energy converters (WECs) in harsh ocean environment and reduce the difficulty and cost of deployment and operation are important. Traditional two-body point absorber with a rigid Power Take-off (PTO) may result in two essential problems on the deployment and operation. This study proposes a novel a two-body self-reactive point absorber with a flexible tether drive PTO. This flexible PTO design can avoid the request of supporting structures on the WEC to constrain the motion and harvest energy from multiple degree of freedoms (DOFs) motion without requirement of a taut mooring. System dynamics considering 4-DOF with the proposed flexible PTO system are formulated. A scaled prototype is designed, fabricated, and tested in a wave tank. Results show that the proposed flexible PTO can greatly increase the power absorption and add a reactive peak in the frequency domain. This study reveals that the proposed PTO is desirable for the two-body point absorber and thus holding the advantages of fast and easy deployment with slack mooring and good survivability under large wave conditions.
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Optimal Constrained Control of Arrays of Wave Energy Converters
Wave Energy Converters (WECs) are designed to be deployed in arrays, usually in a limited space, to minimize the cost of installation, mooring, and maintenance. Control methods that attempt to maximize the harvested power often lead to power flow from the WEC to the ocean, at times, to maximize the overall harvested power from the ocean over a longer period. The Power Take-Off (PTO) units that can provide power to the ocean (reactive power) are usually more expensive and complex. In this work, an optimal control formulation is presented using Pontryagin’s minimum principle that aims to maximize the harvested energy subject to constraints on the maximum PTO force and power flow direction. An analytical formulation is presented for the optimal control of an array of WECs, assuming irregular wave input. Three variations of the developed control are tested: a formulation without power constraints, a formulation that only allows for positive power, and finally, a formulation that allows for finite reactive power. The control is compared with optimally tuned damping and bang–bang control.
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- Award ID(s):
- 2048413
- PAR ID:
- 10553790
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Journal of Marine Science and Engineering
- Volume:
- 12
- Issue:
- 1
- ISSN:
- 2077-1312
- Page Range / eLocation ID:
- 104
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/jmse12010104
