Wave-energy point absorbers can be described as linear, under-damped oscillating systems excited by ocean waves. These devices are intended to be installed offshore and operated in a variety of wave conditions, with a view to producing energy from the oscillations they undergo. Latching control, a technique meant to improve the absorption of energy by point absorbers, has been the subject of many studies in the wave-energy literature. The present paper outlines the original principle of latching control and proceeds with a critical assessment of this control strategy and of some of its variants, from both a theoretical and a practical point of view.
The successful shift to a more sustainable energy mix requires the exploration of promising technologies in low-impact energy production. Only a fraction of this potential is likely to ever be exploited, yet parts of the world blessed with a generous wave resource (Ireland and Hawai"i, for instance) could greatly benefit from wave-energy conversion technology. The history of wave-energy research, initiated in the 1970s, is marked by a wide diversity of ideas and design concepts—some showing less promise and success than others—for producing electricity from ocean waves. Of special interest in this article are wave-energy devices that can be categorized as point absorbers. A point absorber (Budal & Falnes, 1975; Falnes, 2002) can be defined as a relatively small, damped mechanical oscillator excited by ocean surface waves. Small, here, means that the system's water-displacing element (which may consist of a floating or submerged body, or a water column oscillating within a plenum chamber) has small horizontal dimensions in comparison to the wavelength of the exciting waves. Devices of this kind are expected to be deployed offshore at the commercial stage, in arrays of several units called wave farms.
