Subsea Power Supply

• US 20060006656A1
• Filed: 03/21/2005
• Published: 01/12/2006
• Est. Priority Date: 07/09/2004
• Status: Active Grant

• Current Assignee: Onesubsea IP UK Limited (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Smedstad, Eric
• Granted Patent: US 7,224,080 B2
• Time in Patent Office: Days
• US Class Current: 290/43
• CPC Class Codes: F03G 7/05 Ocean thermal energy conversion, i.e. OTEC
• CPC Class Codes: Y02E 10/20 Hydro energy
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient

Abstract

The present invention discloses a subsea power system for use in capturing “free” or “waste” energy (e.g., thermal, geothermal, pressurized subsurface gases or liquids, wind, wave, solar, or other free, waste, or low cost energy sources) to convert and/or store to power a subsea service or device during times when the free or waste energy supply is not as abundant, is not available, or demands require greater output than is provided at steady state. The subsea power system may include: (1) one or more energy-capturing devices—such as a turbine and/or thermoelectric generator—for harvesting free or waste energy, (2) a fuel cell, electrolyzer, and oxygen and hydrogen storage vessels for harvesting energy from the surrounding seawater, and (3) a power converter for receiving energy from the various sources and converting the energy into a useful form consumable by subsea devices.

Claims

1. A system for providing subsea power, comprising:

an energy-capturing device for harvesting free energy; and

a power converter electrically connected to the energy-capturing device, the power converter adapted to convert the free energy into useable electrical energy.

2. The system of claim 1, wherein the energy-capturing device comprises:

a conduit for holding production fluid flowing from a well;

a turbine hydraulically connected to conduit; and

a generator mechanically connected to the turbine and electrically connected to the power converter.

3. The system of claim 2, wherein the energy-capturing device further comprises:

a choke hydraulically connected to the conduit and arranged in parallel with the turbine.

4. The system of claim 2, wherein the energy-capturing device comprises:

a thermoelectric generator electrically connected to the power converter, the thermoelectric generator adapted to generate electrical energy from heat transfer across a temperature differential.

5. The system of claim 4, wherein the thermoelectric generator is arranged in a wellbore adjacent to a conduit for injecting a fluid into the wellbore, and wherein the temperature differential is between the wellbore and the fluid within the conduit.

6. The system of claim 4, wherein the thermoelectric generator is arranged in a wellbore and wherein the temperature differential comprises a vertical temperature gradient of fluid in the wellbore.

7. The system of claim 4, wherein the thermoelectric generator is arranged in seawater outside a wellbore adjacent to a conduit carrying production fluid from the wellbore, and wherein the temperature differential is between the seawater and the production fluid.

8. The system of claim 7, further comprising:

a plurality of conduit loops branching from and reconnecting to the conduit;

at least one thermoelectric generator arranged adjacent to each conduit loop; and

a valve arranged between each conduit loop and the conduit.

9. The system of claim 1, further comprising:

an energy storage device electrically connected to the power converter, the energy storage device adapted to receive electrical energy from the power converter to be delivered back to the power converter as needed.

10. The system of claim 1, further comprising:

an electrical device for performing a subsea operation, the electrical device being electrically connected to the power converter; and

a damper electrically connected between the power converter and the electrical device, the damper adapted to condition the electrical energy from the power converter for use by the electrical device.

11. The system of claim 1, further comprising:

a fuel cell electrically connected to the power converter.

12. The system of claim 11, further comprising:

an oxygen storage vessel connected to the fuel cell; and

a hydrogen storage vessel connected to the fuel cell.

13. The system of claim 12, further comprising:

an interface connected to the oxygen storage vessel and the hydrogen storage vessel; and

a subsea vehicle having separate oxygen and hydrogen storage tanks, the subsea vehicle adapted to be deployed subsea and engage the interface to deliver oxygen from the oxygen storage tank to the oxygen storage vessel and to hydrogen from the hydrogen storage tank to the hydrogen storage vessel.

14. The system of claim 12, further comprising an electrolyzer connected to the oxygen storage vessel and the hydrogen storage vessel, the electrolyzer adapted to receive seawater, break down the seawater into oxygen and hydrogen, and deliver the oxygen and hydrogen to the oxygen storage vessel and the hydrogen storage vessel respectively.

15. The system of claim 14, wherein the electrolyzer is electrically connected to the power converter.

16. A system for providing electrical energy to power a subsea device, the system comprising:

at least one energy-capturing device for harvesting free energy;

a power converter electrically connected to the energy-capturing device, the power converter adapted to convert the free energy into useable electrical energy;

a fuel cell electrically connected to power converter, the fuel cell adapted to electrochemically react oxygen and hydrogen to generate water and electrical energy;

an electrolyzer operatively connected to the fuel cell, the electrolyzer adapted to receive seawater, break down the seawater into oxygen and hydrogen, and deliver the oxygen and hydrogen for use by the fuel cell;

an energy storage device electrically connected to the power converter; and

a damper electrically connected between the power converter and the subsea device, the damper adapted to condition the electrical energy for use by the subsea device.

17. The system of claim 16, wherein each of the at least one energy-capturing device is selected from a group consisting of:

(i) a turbine and a generator;

(ii) a turbine, a generator, and a choke; and

(iii) a thermoelectric generator.

18. A method of providing subsea power, comprising:

harvesting free energy from a subsea environment;

converting the free energy to electrical energy for use in powering an electrical device.

19. The method of claim 18, further comprising:

storing any electrical energy that is above the amount required for powering the electrical device at steady-state operations.

20. The method of claim 18, wherein harvesting free energy comprises:

providing a turbine to be rotated by production fluid flowing from a well to create mechanical energy; and

providing a generator to generate electrical energy from the mechanical energy of the turbine.

21. The method of claim 18, wherein harvesting free energy comprises:

providing a thermoelectric generator to convert heat energy supplied via heat transfer across a temperature differential to electrical energy.

22. The method of claim 18, further comprising:

collecting seawater;

breaking the seawater down into oxygen and hydrogen components;

storing the oxygen component and the hydrogen component;

electrochemically reacting the oxygen and hydrogen component to produce electrical energy; and

delivering the energy to the electrical device.