The Power of Many? Linked Wave Energy Point Absorbers

Ocean waves are a largely untapped source of reliable, renewable energy that could help meet the world’s demand for electricity while causing very few greenhouse gas emissions. Many distinct wave energy devices are currently under development; a large proportion of these are relatively small devices called point absorbers that are likely to need to be installed offshore in reasonably dense arrays. There has been little research published on the design of mooring structures for such arrays and the role that this could play in the performance of the system. Here we investigate a novel concept of linking point absorber devices together with flexible lines. The concept is explored using an idealised computational model of a chain of surging point absorbers with tension-only linkage forces. Nonlinear drag forces are included and the system is simulated in the time domain to accurately capture hydrodynamic “memory effects”. The system is studied for both monochromatic and polychromatic incident wave fields. Our results suggest that linking the devices does not offer potential for enhancing the maximum total power capture in a monochromatic wave field, but may yield superior performance in realistic broadband wave spectra. An additional finding is that, for certain parameter choices, individual devices in a chain achieve significantly enhanced power capture in relation to the maximum for a single isolated device. This observation suggests new possibilities for the design of wave energy systems using linked floating bodies to passively transfer power to a main device; an idea that we call “dummy devices”