Table 1 Recently developed control strategies for the OWC device

Airflow control

i. Parallel valve set up with a turbine

ii. Series mounted valve with a turbine

Series topology is better than parallel topology. It controls unnecessary stalling behavior, which results in high output power.

Speed control

i. Stator-based velocity/hertz control

ii. Rotor-based velocity/hertz

iii. Uncontrolled structure

iv. Constant torque control scheme

v. Regular and variable speed control

vi. Speed control (within oscillation range)

In comparison with other topologies, stator control is a better optimal solution, and available numerical simulations in (vi) show that the speed control within acceptable oscillation range is a better optimal solution. Variable speed control is based on the feedback control strategy.