Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body

Abstract

Citation for the original published paper (version of record):Engström, J., Eriksson, M., Isberg, J., Leijon, M. (2009) Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body. Physics, 106(6) The full-scale direct-driven wave energy converter developed at Uppsala University has been in offshore operation at the Swedish west coast since 2006. Earlier simulations have now been validated by full-scale experiment with good agreement. Based on that, a theoretical model for a passive system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions has been developed. The amplitude response is increased by adding supplementary inertia by use of the additional mass from a submerged body. A sphere with neutral buoyancy is chosen as the submerged body and modeled as being below the motion of the waves. The model is based on potential linear wave theory and the power capture ratio is studied for real ocean wave data collected at the research test site. It is found that the power capture ratio for the two body system can be increased from 30% to 60% compared to a single body system. Increased velocity in the system also decreases the value for optimal load damping from the generator, opening up the possibility to design smaller units. Journal of Applied

A resonant two body system for a point absorbing wave energy converter with direct-driven linear generator

“…This have led to the idea of a point absorber system with two bodies, one acting as a surface buoy, extracting energy, while the lower is passive and adds the desired inertia. [10][11][12][13] It is important to have the two bodies a sufficient distance apart so as not to get destructive interference. All tests on the two body system (TBS) thus far have shown promising results on a theoretical level with a 60% absorption in irregular waves and a significant decrease in optimal load damping.…”

“…All tests on the two body system (TBS) thus far have shown promising results on a theoretical level with a 60% absorption in irregular waves and a significant decrease in optimal load damping. 12 Laboratory experiments with adjustable inertia have shown to give a 60% power capture ratio in irregular waves. 2 The wave energy converter (WEC) concept named the Lysekil Project that is being developed at Uppsala University is a point absorber system with a direct-driven linear generator connected to a semi-submerged buoy.…”

Negative Effective Gravity in Water Waves by Periodic Resonator Arrays

“…This gives rise to a low-frequency resonant bandgap in which water waves are strongly reflected by the resonator array. Although the results are demonstrated using resonators of vertical bottom-mounted split tubes, they can be realized by other resonators such as damping buoys for ocean wave energy conversion [19][20][21][22][23]. For damping resonator arrays, it is found that the resonant bandgap can dramatically modify the absorption efficiency of water waves.…”

“…Damping resonators, such as heaving buoys, can be applied to extract the ocean wave energy [19][20][21] and an array of damping resonators is regarded as a key part of future ocean wave power plants [22,23]. Here, we investigate the influence of the above resonant gap on the absorption spectrum of damping resonator arrays.…”

Nonlinear Passive Control of a Wave Energy Converter Subject to Constraints in Irregular Waves

“…Its value has a significant influence on the performance of the WEC. As shown in Figure 9a, the CWR is a function of the damping coefficient [35]. The peak value of CWR for the WEC under this sea state is approximately 26.6% when the damping coefficient is 290.0 kN·s/m.…”