Wave energy production by a maritime natural cave equipped with Wells turbine

• Published in: Journal of ocean engineering and marine energy Vol. 8; no. 3; pp. 457 - 467
• Main Authors: Monteiro, Wilson Madaleno Léger, Sarmento, António, Monteiro, Jakson Augusto Léger, Monteiro, Clarice Pires
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.08.2022; Springer Nature B.V
• Subjects: Acceleration; Air flow; Case Study; Coastal Sciences; Coefficients; Deceleration; Efficiency; Engineering; Engineering Fluid Dynamics; Excavation; Flow coefficients; Flow rates; Flow velocity; Mechanical Engineering; Oceanography; Offshore Engineering; Renewable and Green Energy; Shafts (machine elements); Torque; Turbine engines; Turbines; Wave energy; Wave power; Wells turbines; Maritime natural cave; Wells turbine; Wave energy; Hysteresis; Cidade-Velha
• ISSN: 2198-6444; 2198-6452
• DOI: 10.1007/s40722-022-00234-1

This paper is the continuation of the work developed by Monteiro et al. (J Ocean Eng Mar Energy, 2021). It analyzes the scenario of the energy production by the same natural cave, this time, equipped with Wells turbine. In addition to the energy production by the cave and the turbine behaviour analysis in a real environment of its operation, it is considered subjects such as the selection of the best material and the procedures followed for the turbine construction. The characteristic curve of the turbine is obtained and the results show that both the pneumatic and the turbine shaft power are very affected by the tidal states. The best values of the turbine shaft power P ( 798 – 1030.0 W) is achieved for flow coefficients φ ranging from 0.20 to 0.34 . However, the best turbine efficiency η ( 81 % ) is obtained when φ = 1.12 . The maximum turbine shafts power, 1.03 kW, occurs when the flow coefficient is 0.46 . In this case, the turbine efficiency is 20.3 % . This last parameter rises rapidly when 0.46 < φ < 1.12 and decreases for φ > 1.12 . The high pneumatic power condition is always associated with low turbine efficiency. Over the turbine operation, it is noticed, the hysteresis phenomenon which is geometrically described by a loop. During the accelerated airflow, the dimensionless torque exhibits, as a function of the flow rate coefficient, an anti-clockwise hysterical loop, with lower values obtained for the acceleration process. However, the turbine efficiency shows an opposite behaviour. The hydraulic and the turbine shaft powers are clockwise loop curves, presenting higher values during the acceleration, than those ones achieved for the deceleration process.