Energy storage considerations for a stand-alone wave energy plant

Despite several wave energy plants based on oscillating water column concept having been tested worldwide, wave energy has not yet gained popularity as a renewable energy source because of highly intermittent nature of available wave power. Still maintaining a constant voltage and frequency at the output, requires embedding of energy storage devices of sufficient capacity into the system. As the first stage, an impulse turbine is used to convert differential air pressure due to the oscillating water column into mechanical shaft power. A permanent magnet based alternator driven by this turbine generates variable voltage variable frequency AC, which is rectified to DC by a diode bridge. At the second stage, a DC motor - alternator set converts this into fixed frequency, fixed voltage AC acceptable as a utility AC supply. Employing MATLAB-Simulink based steady-state model of the plant and assuming an adjustable load, PID control of the output load is carried out in order to estimate the energy storage requirement especially under different climatic conditions