Simulations and field tests of pneumatic power regulation by valve control using short-term forecasting at the Pico OWC

Power production at the Pico OWC WEC has fallen significantly short of early theoretical projections. The main reasons for this that have been identified are: the collection of boulders in the chamber has reduced the water depth promoting wave asymmetry, a defect in the chamber front lip makes a pneumatic connection to the atmosphere at times resulting in pressure loss, and the maximum turbine rotational speed has been limited to below the optimum. In addition the turbulent flow shed from the Wells turbine under stall conditions causes significant stress in the mechanical system components resulting in accelerated fatigue and excessive noise emission. The constant need to maintain and recover fatigued components is an unsustainable drain on financial and human resources. In order to improve power production and reduce fatigue rate by minimising stall frequency and severity, a control strategy is considered to improve pneumatic power exposure to the turbine through relief valve control, using the existing infrastructure. Control decisions are made using the information obtained through short-term wave forecasting using an autoregressive model. Simulations of control are in good agreement with field test results obtained at Pico