Abstract: Apparatus for converting energy contained in surface waves on a body of water to useful energy comprises a float from which is suspended a fully or effectively fully submerged inverted cup-shaped member having a closed top end and an open bottom end. Disposed within the top space is a compressible fluid separated by a flexible membrane from a column of water filling the bottom open end of the submerged member. Passing surface waves cause pressure variations at the bottom end of the member causing changes in the water column height and corresponding changes in the buoyancy of the member. The buoyancy changes induce vertical oscillations of the member relative to the float and known means are used for converting the relative movements of the float and submerged member to useful energy. Preferably, the float vertically oscillates in synchronization with the passing waves, and the vertical movements of the float increase the relative movements between the float and the submerged member.

Abstract: An elongated cylinder is fully submerged, in vertical orientation, just below the mean water level of, e.g., and ocean, and of a length, dependent upon surface waves of preselected wavelength, such that the top of the cylinder experiences relatively large pressure variations in response to over passing waves while the bottom of the cylinder experiences an almost steady pressure substantially independent of the over passing waves. The pressure differential over the length of the cylinder is used for causing relative movements between the cylinder and adjoining water, and such relative movements are used for driving a piston of an energy converter. The cylinder can be hollow and in fixed location for causing water movements through the cylinder, or the cylinder can move through the water relative to a fixed transducer. In one version of the movable cylinder, the transducer is fixedly mounted on a fixed in place float disposed within the movable cylinder.

Abstract: A known type of surface wave energy converter comprises a submerged elongated tube supported by, but being vertically movable relative to, an anchored float. The tube vertically reciprocates in response to overpassing surface waves and drives a transducer for generating useful energy. Improvements include: a motion translator between the tube and the transducer for reducing the stroke length of the transducer and magnifying the force transmitted to the transducer; an energy buffer system for limiting the travel of the tube in response to excessively large surface waves; a gravity anchor for the system for absorbing energy from even greater amplitude waves; means for adjusting buoyancy in response to changing conditions, and pressure relief valves for automatically reducing excessive tube driving pressures caused by excessively large overpassing waves. Energy present in tilting movements of the apparatus are optionally captured in horizontally disposed transducers.

Abstract: A wave energy converter (WEC) including an electric generator for capturing energy contained in ocean waves and converting it to electrical energy at the output of the electric generator may be characterized as an effective capacitive (or inductive) element. Systems embodying the invention include an inductive (or capacitive) element inserted in the circuit between the output of the electric generator and a load in order to achieve resonance with the effective capacitance (inductance) of the WEC and so as to increase the efficiency of the power transfer to the load. In certain embodiments the load coupled to the system has an optimum value which is made a function of the frequency of the ocean waves and the effective capacitance (or inductance). The effective capacitance (inductance) of the converter varies as a function of the frequency of the ocean waves.

Abstract: Protection against damage caused by excessively high input energies, e.g., from ocean storms, is provided in energy converting systems by, in response to the detection of excessively high input energies, changing the electrical impedance of the electrical load to which power from an electrical generator is being delivered for increasing the generator output current for reducing the power converting efficiency of the generator. This increases the mechanical impedance presented by the generator to the source of input energy for reducing the motion producing effect of the input energy.

Abstract: A transducer operated as power generating device is driven at a low frequency and collects energy at the low frequency rate. The collected energy is extracted at a much higher frequency. Extracting the energy at a higher frequency enables the use of components, such as inductors, having reasonable values and sizes. In one embodiment, a power extracting circuit which includes elements designed to resonate with the transducer at a higher frequency than the frequency at which the transducer is being driven is periodically switched in circuit with the transducer. Thus, the electric power generator device operated and controlled by a slowly changing source of energy (e.g., ocean waves, wind, eddies of water) may develop energy at one frequency and may be operated to transfer the energy at another frequency.

Abstract: Systems and circuits embodying the invention include means for sensing at least one of the peaks, amplitude and frequency of an oscillatory input force impinging on a power generating device for controlling the turn-on of a switch used to transfer energy collected by the power generating device to an associated load. The power generator may be a transducer such as a piezoelectric device or a wave energy converter (WEC). Sensors and sensing means embodying the invention are used to control the point in time at which power extracting circuits are switched in circuit with the power generating device. The power extracting circuit may include components which can resonate with the power generating circuit at a higher frequency than, and independent of, the frequency at which the power generating device is being operated. Thus, an electric power generator device operated and controlled by a slowly changing source of energy (e.g.

Abstract: A piezoelectric power generator, particularly for use in a flowing fluid stream, comprises an elongated, flexible central layer of a dielectric material having, spaced axially along opposite sides thereof, a plurality of separate piezoelectric elements each formed from a portion of a continuous layer of a piezoelectric layer extending along each opposite side of the central layer sandwiched between a pair of electrodes unique to each piezoelectric element.

Abstract: An electrical energy generator relying upon piezoelectricity includes electrical generating elements comprising electroded bodies of an electrostrictive material, e.g., polyurethane, having inherent but weak piezoelectric characteristics. A d.c. bias is applied between the electrodes for field-inducing a larger piezoelectric characteristic whereby, upon applying mechanical energy to the element, in known manner, for alternately straining and destraining the body, electrical charge is generated on the electrodes with a high mechanical energy to electrical energy conversion efficiency.

Abstract: Energy from a naturally recurring source of variable mechanical energy is captured and transmitted to an electrical generator causing it to rotate at speeds proportional to the amount of energy captured. The output voltage produced by the generator is a function of the rotational speed imparted to the generator and a load impedance which is coupled via controllable switching circuitry to the generator output. The effective load impedance is varied and controlled by means of a control mechanism responsive to the rotational speed of the generator and the output voltage of the generator which selectively turns the controllable switching circuitry on and off.

Abstract: An open ended tube is mounted in fixed, vertical orientation within a body of water with the top and bottom ends of the tube at preselected depths relative to a mean water level when preselected waves with which the invention is designed for use are present. The tube top open end is disposed at a first depth approximately equal to but not less than the maximum preselected wave amplituded so that the top end is always submerged. The tube bottom open end is disposed at a depth where the energy level associated with preselected waves of maximum wavelength is small. In response to pressure variations caused by passing waves, water flows into and out of the tube, and energy capturing means, e.g., a piston or turbine, is disposed within the tube for converting the water flow to useful energy.

Abstract: For capturing energy contained in surface waves on a body of water while protecting the system from damage against conditions on the water surface, a transducer for converting wave energy to useful, e.g., electrical, energy is anchored to the water bed. A float is connected to the transducer by a rigid connector for transmitting variable forces against the float caused by wave induced circulatory water movements against the float. The connector is of such length that the float is always fully submerged (but within the energy zone of the waves) thus displacing a fixed volume of water and providing an essentially constant upward force on the transducer. The constant upward force is modified by the moving water induced variable forces against the float. The float can be a sphere, but the float is preferably of a shape including laterally extending panels providing a ratio of area to volume larger than that provided by a sphere.

Abstract: A d.c. bias arrangement for increasing the efficiency of electrical power extraction from a piezoelectric transducer comprising a piezoelectric material, particularly of the electrostrictive type, contacted by first and second electrodes. The first electrode is connected directly to an electrical load connected directly to ground potential. The second electrode is connected by two in-parallel paths to the ground potential, one of the paths comprising a d.c. voltage source in series with a large bias resistor, and the other of the paths comprising a large a.c. power bypassing capacitor.

Abstract: A piezoelectric generator comprises one or more inner hubs, an outer, stationary support, and a plurality of strap-like piezoelectric power generating elements mounted between the hubs and the outer support. The hubs are mounted for relative rotation on a first shaft mounted eccentrically on a second shaft having an axis of rotation coincident with central axis of the outer support. Rotation of the eccentric first shaft causes the hubs to follow a circular path around the outer support axis but without rotation of the hub around its own axis. The movements of the hubs cause alternate straining and destraining of the piezoelectric elements for generating electrical energy. For obtaining high energy conversion efficiency, the elements are arranged in groups of three or more substantially identical elements which are identically strained but symmetrically out-of-phase with one another.

Abstract: Piezoelectric electrical generators comprise cantilevered beams of piezoelectric material, cross sections of the beams preferably being triangular and of increasing area from free end to fixed end. Arrays of spaced apart beams are disposed in overlapping, interdigitated relationships with arrays of cams, and the cam arrays are moved relative to the beam arrays for causing engagement and deflection of the beams by the cams for the generation of electrical energy. One system comprises a raft floating on the surface of an ocean. Cam arrays are suspended from the raft for interaction with vertically extending beam arrays mounted on the ocean floor beneath the raft. Relative vertical movements are caused by passing surface waves. In another system, beam arrays are suspended from an above surface structure, e.g., an oil drilling ocean platform, and the beam arrays extend towards and interact with cam arrays mounted on the upper surface of a floating raft.

Abstract: A flexible layer of piezoelectric material, e.g., a known PVDF polymer, is used for generating electrical energy for use on a water craft. In one arrangement, the sheet is laminated within a craft hull of fiberglass. Electrodes are provided for the major opposite surfaces of the layer, and an encapsulating material, e.g., fiberglass or a layer of the polymer itself, comprises the water contacting, exterior surface of the hull. In salt water, the water is one electrode, and an outer encapsulating layer is omitted. Spaced apart air pockets are optionally provided along the polymer sheet for increasing the flexing thereof in response to passing water and for inducing turbulence in the passing water. Elongated, flexible and electroded sheets, optionally including air pockets, are towed behind or beneath the craft, or are flown from a mast on the craft.

Abstract: A system for converting the mechanical energy of ocean waves to electrical energy comprises a weighted member supported from a piezoelectric element for applying a preselected strain to the element. In one embodiment, the element is supported by a float floating on the surface of the water. In another embodiment, the element is supported above the surface of the water and the weighted member, of negative buoyancy, is immersed in the water. The system functions, in use, as an oscillating, weighted spring and, for tuning the system to cause it to enter into mechanical resonance in response to passing waves, means are provided for tuning the natural frequency of the oscillating system.

Abstract: Disposed within a float on the surface of a body of water is a vertically suspended, resilient piezoelectric element provided with a preselected strain by a hanging weight. The piezoelectric system functions as a weighted coiled spring which is driven into oscillation in response to movements of the float in response to passing surface waves. Preferably, the natural frequency of the system is selected in correspondence with the frequency of the passing waves for causing the system to oscillate in resonance with the passing waves. Additionally, a mechanism is provided for automatically adjusting the natural frequency of the system in response to changing wave conditions for maintaining the system in resonance with the waves.

Abstract: An anti-fouling device comprises a layer of piezoelectric material, preferably a poled plastic material such as a PVDF polymer, for mounting on the hull of a watercraft. The layer has electrodes on opposite major surfaces thereof, and the layers are connected to a power supply comprising a battery and a d.c. to a.c. converter. The converter generates an a.c. voltage at a frequency, e.g., 20 KHz, for causing vibrations of the layer, such vibrations serving to retard the growth of water dwelling organisms in the craft. The layer electrodes are also connected to an a.c. to d.c. converter for converting a.c. energy to d.c. energy suitable for trickle charging the power supply battery. Accordingly, during transit of the craft through the water, water induced hull vibrations cause vibrations of the layer for generating a.c. energy for storage in the battery, which stored energy is used for causing anti-fouling vibrations of the energy generating layer.

Abstract: A known type of piezoelectric power generating system for converting the mechanical energy of waves on a body of water comprises a float and a piezoelectric power generating element suspended, under tension, between the float and a bottom anchor. For preventing excessive vertical stretching of the piezoelectric element in response to the presence of excessively high waves, a protective element is coupled between the float and the bottom anchor for effectively limiting the rise of the float above a preselected height corresponding to the maximum straining desired for the piezoelectric element. The coupling is automatic and occurs only at those instances when the piezoelectric element elongation is approaching its maximum amount, and automatic decoupling occurs immediately upon the float falling to a height where non-excessive straining occurs.