Wave Interaction with a Double Chamber Oscillating Water Column Device

Abstract

The principle of oscillating water column within a chamber due to the propagating oscillatory ocean waves being converted into clean energy through wave energy convertor referred to as Oscillating water column (OWC) device is a well proven concept that still remains as one of the most promising alternate sources of energy from the Ocean. The OWC has single column of water oscillation, whereas, Double Chamber Oscillating Water Column (DCOWC) has two chambers of water oscillation. DCOWC is relatively a new concept. In this paper, the performance characteristics of a DCOWC is evaluated through a well-controlled experimental investigation in a wave flume. The conceptual design aspect of DCOWC and its uniqueness compared with the present state of art in wave energy converters (WECs) are explained. The efficiency of the system is assessed by considering the variations in the geometrical dimensions of the system along with the different characteristics of incident waves. The methodology adopted for evaluating the hydrodynamic performance in terms of energy conversion efficiency, the development of additional structural stability and the wave amplification at the mouth are discussed and its significances are highlighted by presenting the results in a dimensionless form. The analysis of the results indicates the feasibility of the DCOWC concept in harnessing energy from the waves.International Journal of Ocean and Climate Systems (DCOWC) device. A detailed literature review has revealed that a number of researchers have carried out studies on the performance characteristics of OWC, while, the literature on DCOWC is rather limited. This prompted to carry out well controlled physical model tests on the hydrodynamic performance characteristics of DCOWC exposed to the action of regular waves in the present study. EXPERIMENTAL SET-UPThe experiments were carried out in the wave flume of 72.5m long, 2m wide and 2.7m deep at the Department of Ocean Engineering, IIT Madras, India. Three smaller units of DCOWC each of 0.30m x 0.60m x 1.45m and one bigger unit, 1.0m x 0.60m x 1.45m were fabricated for simultaneous testing since the number of parameters dictating the model and the measuring parameters were more. In order to test the above stated four models simultaneously without the interference effect between the adjacent units, plywood partitioning was provided for a length of 11m in between the units. The plan and cross section of the DCOWC model adopted for the present study are shown in Fig. 1. The model parameters of interest are the bottom opening depth (O) of the oscillation chamber and the mouth clearance (h) at the entrance. The width of the front duct (b) was kept at 0.30m. The water depth (d) was maintained at 1m throughout the study. Herein, the depth of water inside the DCOWC model, d i is same as d. To simulate the damping being exerted by the turbine in prototype structure, a circular air hole having a cross sectional area equal to 0.65% of plan area of the air chamber is provided. Wang et al. (2002) have reported OW...

Oscillating Water Column Geometrical Factors and System Performance: A Review

“…Amin's study [101] also agrees to this point, suggesting that the curved frontal entrance of the OWC chamber could result in a higher hydrodynamic energy extraction performance. The OWC energy conversion capacity could achieve a maximum efficiency of 94% with an opening length -water depth ratio of 𝐻 𝑜 /ℎ = 0.80, as reported by Wilbert et al [102]. Ashlin et al [45] conducted laboratory experiments with four different chamber bottom shape configurations: a 300mm round curve radius, a flat bottom surface, a bottom slope of 1:1 and 1:5, and finally, an experiment with the findings of the best output performance obtained, which belongs to the circular curved bottom profile, compared to the rest.…”

Experimental Evaluation of the Effect of Incident Wave Frequency on the Performance of a Dual-chamber Oscillating Water Columns Considering Resonance Phenomenon Occurrence

“…The results showed that the dual-chamber OWC performed better than the single-chamber OWC. Wilbert et al [12] experimentally investigated the interaction of a wave with dual-chamber OWC, the effect of wave height on efficiency was investigated; Experiments were also performed to simulate a single-chamber OWC without a front duct and to understand the impact of the front channel. Martinelli et al [13] studied a multi-chamber OWC according to the wave characteristics of the Mediterranean Sea; The OWC was called Seabreath.…”

Comparison of the performance of oscillating water column devices based on arrangements of water columns

“…The study of device shape parameters as determinants of hydrodynamic performance has resulted in several important conclusions, including the relationship between column width and length of the front wall which submerged to water depth [6], the effect of inlet valve area on the effectiveness of wave energy absorption [7], the effect of the basic form of the column on the hydrodynamic characteristics [5,8] and the effect of column shape on pressure fluctuations [9].…”