Wave energy converter

A wave energy converter comprising:

• a. a positively buoyant axi-symmetric vessel fully submerged in an ocean;
• b. said vessel being moored to a reaction mass by a vertical mooring line;
• c. said reaction mass being selected from the group consisting of:
• a seabed;
• a submerged floating platform, whereby said vessel can react directly with said seabed at depths of said ocean that characterize a continental shelf and can react with said platform at depths of said ocean greater than depths that characterize said continental shelf;
• d. said vessel being tethered axi-symmetrically to said reaction mass by at least three non-vertical tethers;
• e. said tethers being held under tension by tensioning means and connected to a power take off system whereby orbital and omnidirectional motion of said vessel driven by orbital and omnidirectional motion of swell can be converted to useful power;
• f. a control system comprising radio input of predicted wave height and swell period, radio input of a required depth of submersion of said vessel, input from local sensors measuring wave height and swell oscillation period and input from local sensors measuring motion and depth of submersion of said vessel, said inputs being applied to means for control of said depth of submersion of said vessel and to means for control of said vessel's natural period of oscillation, outputs of said means for control being said depth of submersion this being varable according to said wave height and said natural period of oscillation, this being variable according to said swell oscillation period;
• g. said mooring line having at least one elastically extensible section enabling said vessel to follow an orbital path, responding to both heave and surge vectors of said swell from any direction;
• h. said mooring line being connected to a lower locking winch, whereby said depth of submersion of said vessel can be varied dynamically between a near-surface position and a position in quiet water in response to varying wave heights so that high energy conversion rates can be sustained in differing wave climates and so that storm damage can be avoided;
• i. said vessel being connected by a non-slidable connection to an upper line that is attached to a surface-piercing float of positive buoyancy;
• j. said upper line having at least one elastically extensible section enabling said vessel to follow an orbital path responding to both heave and surge vectors of said swell from any direction;
• k. said upper line being connected to an upper locking winch, whereby said depth of-submersion of said vessel can be varied and tension of said upper line and of said mooring line can be varied so that said vessel's natural period of oscillation can be dynamically varied to match said swell oscillation period over a range that characterizes energetic ocean swell;
• l. said tethers having means for said tethers to be neutrally buoyant uniformly along the length of said tethers, whereby gravitational flexing can be made insignificant over depths that characterize the continental shelf and so power losses from gravitational flexing can be made insignificant.