Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
  • F03G7/00—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for
  • F03G7/04—Mechanical-power-producing mechanisms, not otherwise provided for or using energy sources not otherwise provided for using pressure differences or thermal differences occurring in nature
  • F03G7/05—Ocean thermal energy conversion, i.e. OTEC
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/0011—Heating features
  • B01D1/0041—Use of fluids
  • B01D1/0047—Use of fluids in a closed circuit
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D1/00—Evaporating
  • B01D1/26—Multiple-effect evaporating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/10—Vacuum distillation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
  • B01D5/0033—Other features
  • B01D5/0036—Multiple-effect condensation; Fractional condensation
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
  • C02F1/046—Treatment of water, waste water, or sewage by heating by distillation or evaporation under vacuum produced by a barometric column
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F1/00—Treatment of water, waste water, or sewage
  • C02F1/02—Treatment of water, waste water, or sewage by heating
  • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
  • C02F1/048—Purification of waste water by evaporation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
  • Y02A20/124—Water desalination
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient

Definitions

• OTEC Ocean Thermal Energy Conversion plants have been used to produce electric power and to desalinate seawater.
• the warm water flashes to water vapor.
• the water vapor can drive a turbine and then is condensed to produce fresh water.
• the warm water is used to boil the working fluid in a heat exchanger or by allowing the warm water to flash to vapor, which then condenses on the boiler surfaces to release the heat of condensation of the water vapor, as presented in U.S. Patents 5,513,494 and 4,324,983.
• the condensed water is fresh water that can be used by nearby communities.
• the working fluid is normally condensed in a heat exchanger by the flow of cold water through the condenser.
• This invention provides a method of causing the cold water to evaporate and provide another source of fresh water, almost doubling the amount of desalinated water from the OTEC plant. For additional fresh water production, this invention provides a method of using the warm-water discharge and the cold-water discharge in a desalination unit.
• This invention can not only be used in an OTEC plant, but it can also be used in other power generation systems.
• a geothermal power generation plant if superheated water is available from underground, it can be evaporated under pressure. The vapor would flow to a boiler, where it would condense on the boiler to boil a working fluid. The condensed water would be clean, distilled water.
• OTEC is usually used to refer to the power plant, but it should be kept in mind that this invention can be used in other types of power plants.
• the preferred embodiment of the present invention does not flash the warm water but rather allows warm water to run down a surface and absorb heat from the incoming warm ocean water as it vaporizes.
• the vapor flows to the surface of a boiler where it deposits heat as it condenses.
• the heat boils a working fluid to drive a turbine.
• the condensed water runs down and is collected for potable uses. This is somewhat similar to prior art that uses the flash method of producing vapor from the warm water.
• this system Rather than having a pre-deaerator to remove dissolved air in the incoming water, this system prevents the buildup of the air entrapped in the vapor flow and removes the air continually from the system.
• Previous designs of OTEC plants with desalination used the warm water to produce the desalinated water on the boiler side of the system, but the cold side of the rankine cycle engine was not used for water production.
• the cold side also produces fresh water.
• the condensation of the working fluid in the condenser provides heat to vaporize the water, and the water vapor condenses on the surface of a cold-water heat exchanger. It is then collected for potable uses.
• the entrapped air in the cold-water side of the system is treated like that of the warm-water side.
• Figure 1 is a schematic cross section for a system that produces fresh water from the warm-water side of an OTEC plant as it transfers heat from the warm ocean water to the boiler, and produces fresh water from the cold-water side of an OTEC plant as it transfers heat from the condenser to the cold seawater.
• Figure 2 is a schematic cross section end-view of one design of the cold-water side of an OTEC plant showing a condenser pipe containing a number of working-fluid condenser tubes where cold seawater is evaporated from the outside of the tubes and a heat exchanger pipe in which the water vapor condenses as it transfers heat to incoming cold water.
• Figure 3 is a schematic cross section side view of one design of the warm-water side of an OTEC plant showing a number of slanted parallel plates on which warm ocean water flows down as a film and evaporates as it picks up heat from warm ocean water that flows below the slanted surface, and the warm vapor flows to a boiler (not shown) to provide heat to boil a working fluid.
• Figure 4 is a schematic of a multi-stage desalination system that uses warm-water discharge and cold-water discharge from the OTEC plant of Figure 1.
• Figure 1 shows schematically an embodiment of the present invention of an OTEC plant that uses water vapor as the heat transfer medium to move heat from the warm ocean water to the working fluid vapor, and uses water vapor as a heat transfer medium to transport heat from the condenser to the cold ocean water. It also shows the collection of fresh water from the warm and cold sides of the OTEC plant,
• the warm ocean water As the warm ocean water enters through pipe 1 to a heat exchanger 2, it provides heat through a heat exchanger wall to a film of seawater 4 that is flowing down the other side of the wall in an evacuated chamber 3.
• the warm water cools as it flows upward through the heat exchanger channel 25, because it is releasing heat to the water film 4.
• part of it When it gets to the top of the channel 25, part of it then flows down as a film of water 4 on the right wall of the evacuated chamber 3.
• the rest of the water flows out the discharge pipe 27. Since the water flowing down as a film 4 has a temperature near equilibrium with the water vapor in chamber 3, it does not flash. It absorbs heat as it evaporates at constant temperature.
• the seawater from the flowing film flows out the warm- water discharge pipe 10.
• Heat exchanger 2 should be tall enough so that the pressure created by the column of water will prevent the warm water at the bottom of channel 25 from flashing. It would be appropriate to have the whole unit high enough above the ocean surface so that the pressure is low in the water.
• the water vapor flows down in chamber 3 and condenses as a fresh-water film 5 on the wall of the boiler 6. which contains a low-boiling-point working fluid 7.
• the vapor channel 26 beside the boiler 6 is designed so that the vapor flows continuously downward as the channel becomes narrower. That keeps the vapor flowing downward, and it carries any entrapped air that was previously dissolved in the water down to the bottom of the channel. As water vapor moves toward the boiler wall, the entrapped air tends to collect next to the film of condensed water 5. Since the water film 5 is flowing downward by gravity, it tends to drag the air with it.
• a bleed pipe 9 allows the air (along with some water vapor) to be drawn off to a vacuum pump. This is the method of deaeration of the water.
• the advantage of using the water vapor as a heat transfer medium is that the condensing water surface 5 is almost the same temperature as the evaporating surface 4. It is similar to a heat pipe, which is a far better heat conductor than any metal. If a regular heat exchanger is used to transfer the energy of the water to the working fluid, there is a larger temperature differential between the water and the working fluid, because the water is a poor heat conductor.
• Another advantage of using water vapor as the heat transfer medium, rather than using an ordinary heat exchanger is the seawater does not touch the boiler and provide corrosion and scaling problems on the boiler.
• the heat supplied by the condensing water 5 boils the working fluid 7.
• the working fluid vapor then flows to a superheater 11 (if any) and then to a turbine 12, which extracts mechanical energy.
• Heat for the superheater can be supplied by solar energy, bio-fuel, fossil fuel, and/or a separate stream of warm ocean water.
• the vapor leaves the turbine, it is cold. It flows to the condenser 13, where it condenses as a liquid film 14 on a wall that is cooled by the evaporation of a cold-water film 18 on the opposite side of the wall.
• the condensed working fluid 14 flows down to the bottom and is pumped by pump 23 back to the boiler 6 to repeat the cycle.
• the water film 18 flows down and is discharged through the cold-water discharge pipe 22.
• the water vapor that leaves the cold-water film 18 flows down to the cold-water heat exchanger 16. It condenses on the wall of the heat exchanger as fresh water film 19 and then flows down to the fresh water outlet pipe 20. Entrapped air in the vapor is carried down and is drawn off to a vacuum pump through pipe 21. This provides a deaeration system similar to that of the warm water side.
• This system provides a method of producing fresh water on both the warm- water side and the cold-water side.
• the water vapor is also used as a heat transfer medium to move the heat from the warm water to the boiler and the heat from the condenser to the cold water heat exchanger.
• the warm water and the cold water should start flowing first so that the water films are formed.
• the cold-water film 18 on the condenser will cause condensation of the working fluid vapor and cause vapor to flow from the boiler 6 through the turbine 12 and to the condenser 13. That will start to cool the boiler 6, and water will start to evaporate from the warm-water film 4 and condense on the boiler.
• Another embodiment of the present invention would have sprayers that spray water onto the surfaces that produce evaporation.
• the water droplets would tend to flash as they move toward the surfaces, and they would flash more after striking the surfaces.
• Figure 1 shows simple surfaces, but in actuality they would be multi-plate heat exchangers with films flowing down in alternate chambers while warm water flows up the other channels. Another way would be to have vertical pipes that the warm water flows up through and then part of it flows back down as a film on the outside. The evaporated vapor from the film could then flow to the outside of a boiler pipe and condense there as the working fluid boils inside the pipe.
• the working fluid could condense inside vertical pipes while cold water flows down the outside. Vapor from the cold water could flow to the outside of cold-water pipes and condense there.
• Figure 2 shows one embodiment of the present invention that describes the flow of water and water vapor on the cold side of the OTEC plant. It shows an end view of the condenser enclosure pipe 50 and the heat exchanger enclosure pipe 57. After the working fluid vapor leaves the turbine, it flows into condenser tubes 51, which are shown in end view in Figure 2. Cold seawater flowing down the outside the condenser tubes 51 absorbs heat from the condenser tubes and evaporates. This removal of heat causes the working fluid vapor to condense inside the condenser tubes. The working fluid liquid is then pumped back to the boiler. The connecting pipes and pump for the working fluid liquid are not shown.
• These can be tubes or chambers with rectangular cross-section that are formed by flat plates on all four sides.
• Water vapor that evaporates from the condenser tubes 52 in the condenser enclosure pipe 50 flows into the heat exchanger enclosure pipe 57 and condenses on the cold-water heat exchangers 56.
• the condensed water drips down to the bottom of the heat exchanger pipe 57 and flows out pipe 60 as fresh water.
• the cold seawater flows up through the cold-water heat exchangers 56, it becomes warmer by absorbing heat from the condensing water on the outside surfaces of the cold water heat exchangers. Most of the up flowing water flows out the discharge pipe 61, but some of the water flows through regulator valve 58, through pipe 59, and through water distributors 53, which distribute the water along the top condenser tubes. After the water runs around the top condenser tubes, it flows down to the next lower condenser tubes, etc. Metal strips 52 between the condenser tubes help to provide even flow of the water from tube to tube.
• the condenser tubes 51 could be vertical, and the water could start at the top of each tube and flow as a film down each tube.
• the temperatures shown at various points of the device represent ideal water temperatures in degrees C as an example of one set of conditions. Their purpose is help the reader understand what is happening.
• FIG 3 is a schematic diagram of one arrangement of the heat and vapor transfer mechanism on the warm side of the OTEC power plant.
• Warm seawater enters pipe 77 and is distributed into warm water channels 75 and flows to the right. Most of this water is collected and discharged through discharge pipe 73.
• a small amount of the water flowing in the channels 75 passes through water distributors 74 and then flows as a film 71 down the sloping upper surfaces of the channels 75. As the water films 71 flow down, part of it evaporates as it absorbs heat from the water flowing in channels 75. The water flowing to the right in channels 75 becomes cooler as it releases heat to the water film 71.
• the water vapor that evaporates from the films 71 flows out pipe 70 and flows to the working fluid boiler where it condenses and releases the heat of condensation into the boiler.
• the water flowing in the water films 71 that does not evaporate falls to the bottom of container 72 and is pumped by pump 76 to the discharge pipe 73.
• the warm- water discharge is at 22° C in the example of Figure 1, while the cold- water discharge is at 10° C. This temperature differential can be used to produce more fresh water.
• Figure 4 shows one example of a multi-stage desalination unit that can do that.
• the warm-water discharge from the OTEC plant flows through pipe 30 into and through the warm seawater chamber 31, and some of it flows through water distributor 32 and flows as a water film 33 down the wall of the next chamber 39 to the left.
• the cold-water discharge from the OTEC plant flows through pipe 36 into and through the cold-water chamber 38 and flows as water films 37 down the right wall of some of the evacuated chambers 39.
• Heat from the warm seawater evaporates water from the film 33 flowing down the wall next to the warm seawater chamber. That water vapor passes around the baffle 35 and condenses on the left wall of its chamber 39 and passes heat to the flowing water film 37 through the wall. This process continues through each stage until the heat flows into the cold-water chamber 38.
• Each chamber from right to left is cooler than the chamber to its right.
• the seawater is discharged through pipe 41, while fresh water flows out pipe 42.
• Figure 4 shows three evacuated chambers, which represents three stages of the desalination unit, but there can be more or fewer evacuated chambers, depending on the available temperature difference between the warm water and cold-water input temperatures.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
• Combustion & Propulsion (AREA)
• Water Supply & Treatment (AREA)
• Organic Chemistry (AREA)
• Environmental & Geological Engineering (AREA)
• Hydrology & Water Resources (AREA)
• Biodiversity & Conservation Biology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Oceanography (AREA)
• Sustainable Development (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Heat Treatment Of Water, Waste Water Or Sewage (AREA)
• Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)

Priority Applications (3)

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Cited By (12)

Citations (3)

• 2007
  • 2007-10-02 EP EP07843671A patent/EP2076320A2/en not_active Withdrawn
  • 2007-10-02 AU AU2007303213A patent/AU2007303213B2/en not_active Ceased
  • 2007-10-02 MX MX2009003513A patent/MX2009003513A/es unknown
  • 2007-10-02 WO PCT/US2007/080178 patent/WO2008042893A2/en active Application Filing

Patent Citations (3)

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