Harnessing Ocean Wave Energy—Flow Rectifications

India can harness 40 GW of ocean energy from its 7500 km long coast. There are several devices to harness such power. One commonly researched device is an oscillating water column (OWC). One end of the duct faces the water, while the other is open to the atmosphere. When the wave enters the duct, the air is pushed out; when the wave recedes, the air gets sucked in. It uses an air duct, which contains a single turbine or two turbines. The conventional turbines face difficulty in harnessing this pneumatic energy as air direction changes with wave action in OWC. A bidirectional turbine can work in this situation without additional units. However, because of their symmetrical aerofoil geometry construction, these turbines have poorer efficiency than conventional air turbines. A pair of conventional turbines can be used with OWC such that one works as a power producer and another as a flow blocker. This turbine action reverses for the opposite wave cycle. However, the flow blocker turbine cannot block the airflow completely, causing poor performance at the power producer turbine. Mechanical valves can be placed along with the turbine to improve flow blockage, but this may be unreliable considering the ocean’s dynamic nature. A fluidic diode (FD), similar to an electrical diode, offers variable resistance based on flow direction. This can be used with OWC to improve the performance of the air turbines. This article discusses various FDs used for engineering applications and a detailed numerical study on the FD used for wave energy applications.