On the efficiency of wave energy caissons in array

Abstract

A detailed experimental investigation on the efficiency of the power absorption of Multi-resonant Oscillating Water Column (MOWC) wave energy caissons in an array is reported. Regular wave measurements were conducted on an 1:50 scale model of an array of Multiresonant Oscillating Water Column (MOWC) type free standing wave energy caissons using the images method. A range of hydrodynamic parameters, with a different damping of Oscillating Water Column (OWC) chamber and various centre to centre spacings ( S) between the caissons in an array for a constant OWC width ( b), were used, i.e., experiments were conducted for different S b ratios. It is found that, hydrodynamic efficiency of MOWC for power absorption increases with increased S b value up to 3, beyond which it reduces. About 60% efficiency can be achieved with a S b ratio of 3 which is considered as optimum spacing. The efficiency decreases with increase in wave steepness ( H L ), due to a greater blow up period for higher H L values than for lower H L values during which the pressure becomes atmospheric. The percentage energy reflection decreases with increasing relative water depth. The average energy reflection is found to be 30%. Further investigation is recommended in order to enhance the efficiency considering the structure geometry as well as the damping of the air chamber.