Ocean Power Technologies, Inc.

Olean Power Technologies, Inc.

Thomas R Welsh

George W Taylor

Joseph R Burns

Paul J Smalser

James S Gerber

A wave energy converter (WEC), for use in a body of water of depth Dw, includes a tubular structure and a piston within the tubular structure where the relative motion between the piston and the tubular structure is used to generate electric power. The length (L) of the tubular structure may be selected to have a predetermined value based on the fact that: (a) the efficiency of the power generated by WEC increases as the length &ldquo;L&rdquo; of the tubular structure increases from a minimal value until L reaches an optimal value; and (b) the efficiency decreases as L is increased beyond the optimal value due to the increased mass of the water that the tubular structure and the piston have to move.

Wave energy converter (WEC)

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. Accordingly, systems embodying the invention may include a controller for varying the load and/or the inductive (capacitive) element coupled in the system to resonate with the converter for increasing the efficiency of the system.

Apparatus and method for optimizing the power transfer produced by a wave energy converter (WEC)

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. The resonating circuit is switched into circuit with the transducer on the positive and negative peaks of the force driving the transducer for a time approximately equal to Tc, where Tc is equal to approximately &frac12;fo, where fo is the resonant frequency of the circuit with the switch closed. In another embodiment the load applied to the circuit is designed to have an optimum value to optimize the power transfer. Other embodiments include circuits for reliably and accurately detecting the peak(s) of the driving input signals.

Switched resonant power conversion electronics

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., ocean waves, wind, eddies of water) may develop energy at one frequency and may be operated to transfer the energy, at a selected point in time, at another frequency.

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Princeton, NJ, United States of America

Thomas R Welsh