WO1980001301A1 - Systeme de conversion d'energie pour obtenir de l'energie utilisable a partir de sources a bas niveau de chaleur - Google Patents

Systeme de conversion d'energie pour obtenir de l'energie utilisable a partir de sources a bas niveau de chaleur Download PDF

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Publication number
WO1980001301A1
WO1980001301A1 PCT/US1978/000204 US7800204W WO8001301A1 WO 1980001301 A1 WO1980001301 A1 WO 1980001301A1 US 7800204 W US7800204 W US 7800204W WO 8001301 A1 WO8001301 A1 WO 8001301A1
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WIPO (PCT)
Prior art keywords
water
gas
warm
energy conversion
work
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Application number
PCT/US1978/000204
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English (en)
Inventor
C Jahnig
Original Assignee
C Jahnig
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Publication date
Application filed by C Jahnig filed Critical C Jahnig
Priority to PCT/US1978/000204 priority Critical patent/WO1980001301A1/fr
Publication of WO1980001301A1 publication Critical patent/WO1980001301A1/fr

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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
    • 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
    • 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
    • Y02E10/10—Geothermal energy
    • 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

  • the present invention relates to energy conversion systems for deriving useful power from sources of low level heat such as thermal gradients in the ocean, or from solar, geothermal or other sources of low level heat and more particularly by using warm water to heat a gas, expanding the gas to extract power and then cooling and compressing the gas with cooler water back to initial conditions.
  • sources of low level heat such as thermal gradients in the ocean, or from solar, geothermal or other sources of low level heat and more particularly by using warm water to heat a gas, expanding the gas to extract power and then cooling and compressing the gas with cooler water back to initial conditions.
  • Titanium tubing has been proposed, using a wal thickness of only 0.03 inches to avoid intolerable cost, bu this poses a major risk as regards mechanical integrity of equipment in such a hostile environment as the ocean.
  • E fractional efficiency
  • T is temperature of the warm source
  • 2 is temperature of the cold receiver.
  • E fractional efficiency
  • Actual designs can achieve only 2.5% to 3% efficiency, allowing for practi ⁇ cal heat exchangers and "parasitic" power losses for water pumps and other auxiliaries.
  • the present invention provides a practical method to obtain useful energy from the warm and cold ocean water by • directly contacting warm water with a gas such as air in a confined zone to cause an increase in pressure, then expand ⁇ ing the gas while continuing to supply heat from the warm water, and extracting power from the expansion by means of a piston or other device.
  • the gas is then cooled and recompressed in direct contact with cold water through part or all of the compression cycle, so that the cycle can be repeated.
  • One piston can serve two chambers of confined working gas connecting to opposite sides of the piston, whereby much of the work for compression is supplied directly from expansion so as to minimize the amount of power that is handled via auxiliary facilities.
  • the invention is also useful to derive energy from solar collectors, geothermal sources, etc., and for "bottoming" to make use of low level heat rejected from power stations using nuclear or fossil fuel. It is an object of this invention to provide improvements by making basic modifications to the system design which eliminate the use of indirect exchangers, and allow using air as the working fluid instead of ammonia, propane, or fluorinated compounds, while at the same time providing a more effective and practical way to recover
  • One application of my invention employs direct contact of water with air as the working gas, to provide heat exchange together with effective countercurrent staging.
  • the temperature range over which the working fluid operates is increased along with efficiency.
  • 80° warm water and 40° cool water it becomes practical to operate over a range of 30° - 40° (75° to 45°) giving a max ⁇ imum efficiency of 5.7% according to the previous equation, compared to the range of only 20° and an efficiency of 3.7% in some comparable designs using indirect heat exchange with ammonia.
  • a further advantage for the new system is that it becomes practical to superheat the warm water by solar radia- tion in a confined zone at the surface. This may not be practical in alternative systems such as the ammonia type.
  • my invention avoids losses due to latent heat, and introduces the capability for effective use of countercurrent and crossflow heat exchange and staging where applicable.
  • Direct contact between air and water provides surface for heat transfer at relatively low cost, so a large surface area can be justified. This can allow heating or cooling the water over a greater temperature range, e.g., 5° to 10°F. compared to the usual 2° to 5°, to thereby decrease the water flow rate required. Since flow rates of both warm and cool water are very large, the resulting savings can be considerable in costs and pumping power.
  • FIGURE 1 is a schematic side view of an OTEC plant constructed in accordance with the present invention and designed for mid-depth ocean operation;
  • FIGURE 2 is a schematic side view of a modification of the OTEC plant of FIGURE 1 adapted to employ superheating by using solar collectors on the surface;
  • FIGURE 3 is a schematic side view of an OTEC plant constructed in accordance with the present invention and designed for ocean bottom location operation
  • FIGURE 4 is a schematic side view of an OTEC plant constructed in accordance with the present invention and designed for ocean surface location operation;
  • FIGURE 5 is a schematic side view of a modification of the OTEC plant of FIGURE 4 in which the free piston system of FIGURE 4 is replaced with a floating piston.
  • FIGURE 6 is a schematic side view of an OTEC plant constructed in accordance with the present invention in which a compressible packing is used in conjunction with a floating piston.
  • FIGURE 7 is a schematic side view of a novel design of a cold water pipe used in the present invention.
  • FIGURE 8 is a block diagram of a system combining an OTEC system of the present invention with a mariculture system.
  • OTEC plants may be classed into three broad groups: an ocean surface or near ocean surface location, mid-depth ocean location at 200 to 600 feet, for example, and an ocean bottom location that may be 1000 feet deep or more.
  • the surface location is easily accessible to ships and lends itself to industrial manufacturing and a "floating city" as part of the OTEC complex.
  • Solar collectors can be incorpor ⁇ ated to superheat the warm water.
  • Mid-depth location avoids the major wave action associated with the surface, and the design pressures are moderate, while access to the surface
  • the bottom location eliminates the long heavy moori cables, or alternative powered position-holding system nee in the two preceding cases, but is subject to very high pressures and decreased accessibility. It is also subject fouling due to benthic marine life.
  • the surface location also subject to fouling from algae, barnacles, etc., while the mid-depth location should be less susceptible to fouli Therefore, the primary description that follows will be gi for a mid-depth ocean location by way of example, but it should be clearly understood that the new improved system intended equally for use at the surface or on the bottom, with suitable modifications in design for adaption to the considerable change in environment.
  • the specific elements of my system include a tank or vessel containing a working fluid such as a gas or air. T air is alternately warmed and cooled, whereby the expansio and contractions move a piston, bellows, diaphragm, or oth device to develop power output.
  • the power can appear as shaft work driving a flywheel, while the net work output c be used as such or to drive an electrical generator, or fo other purposes.
  • heat is supplied during the warm part of the cycle by direct contact of the gas with warm water, for example by spraying the water through the tank or cylinder.
  • Spraying down through the tank tends to give countercurrent heat transfer as well as staging, thereby minimizing the water flow rate required, and increasing the temperature change on the water flowing through.
  • Open mesh packing, low pressure drop trays, etc. can be used to improve contacting
  • the ideal is to first heat the gas to warm water temperature at constant volume to generate maximum pressure, and then maintain this temperature during expansion. In practical systems this ideal can be approached but not attained.
  • the gas is cooled, again by direct contact with a spray using cool water, and the gas is then compressed while cold water sprays maintain the gas at minimum practical temperature.
  • the water sprays may be shut off part way through the expansion or contraction,
  • W is the work in Btu/mol of gas
  • R is the gas constant 1.99
  • V 2 /V is the natural logarithm of the ratio of final to initial gas volume.
  • Net work output is the work of expansion minus that of compression, which values are in the ratio of the corresponding absolute temperatures.
  • Heat input during expansion ideally is equal to the wor output plus the sensible heat added to warm the gas up to the higher temperature. Efficiency is then the net work output divided by the heat input. For various cases of interest on OTEC this ideal efficiency is 4 to 8% without superheat, and 5 to 15% or more when providing solar collectors to superheat the warm water. Practical systems can have about 80% of these ideal efficiencies.
  • An excellent prospect is to use the system in combina- tion with solar collectors to provide shaft work or electri ⁇ city.
  • a warm fluid temperature of 190°F. can be obtained, which is much higher than available from warm ocean water and more than compensates for the loss of a low temperature ocean heat sink.
  • One of the limitations of solar energy today is the need for a new engine to use low level heat effectively, and it appears that OTEC technology will be useful here.
  • Geothermal heat is another good application, since it usually provides heat at 150° to 300°F.
  • the working gas is cooled to pull the free piston down ⁇ ward.
  • a valve opens to allow water from a low pressure source to flow in above the piston to fill the space and generate a hydraulic head or pressure which helps to compress the cooled gas as the piston moves down to its lowermost position.
  • the working gas is heated using warm water so that the pressure increases and it tends to expand, moving the piston upward.
  • Water valves are switched at this time so as to discharge the water above the piston to a high pressure reservoir as the piston moves up. Water from the high pressure reservoir flows through a turbine and is returned to the low pressure reservoir that supplies water as described above.
  • This arrangement provides a thermodynam- ically "reversible" operation, and is therefore highly efficient.
  • a temperature change of 30°F. can provide 37 feet water head on the turbine at a nominal 20 atm. operating pressure. ⁇ BURE ⁇ /
  • a Vbm WIP In the first case (Column 1) , water is superheated to 95°, which is well within the capability of solar collectors, but also below the lethal temperature of warm water life. Net work per mol of gas and thermal efficiency are both higher with superheating than without. Also, it becomes practical to use a greater temperature change on the warm and cold water flows. Parasitic power losses are lower with superheat, and as a percent on net power output the advantag is even more significant. Both cases use the same equipment volume at expanded conditions. This example illustrates the large advantage obtained by moderate superheat. In this example, the solar collection can be simply a confined layer of surface water that is drawn in for use. A depth of 10 feet supplies day to day storage.
  • inven ⁇ tion a preferred embodiment of the inven ⁇ tion will be described for application at mid-depth in the ocean at about 400 feet deep - below the level of wave disturbance but still with access to the surface by way of a vertical conduit.
  • the system, operation, and parameters are as described in Table 1.
  • Cycle length is about .002 hours (7.6 seconds) and water flows are maintained throughout most of the cycle but are shut off 1/2 to 1 second before expan ⁇ sion or compression is completed at the extremes of volume, in order to allow water drainage.
  • Contacting of water and air is carried out using an open mesh or pads as packing to improve contacting and also to provide very desirable staging which minimizes water con ⁇ sumption.
  • Water flows downward and air upward through the packing which may, for example, extend through a height of 10 to 20 feet.
  • Work for pumping the water is minimized by filling warm or cold water reservoirs while they are at a convenient low pressure level, and then pressure balancing the reservoir to the working chamber while the water is flow ⁇ ing to the appropriate contacting zone.
  • a single contacting zone can be used to which warm or cold water is supplied alternatel .
  • a double-acting piston is used, with gas expanded on one side, while gas is being compressed on the other side of the piston. Net work output is that from expansion at the higher temperature, minus the work needed for compression at the lower temperature.
  • a flywheel or other device is used to balance the amount and timing of wor input and output, connected to multiple cylinders.
  • a 10° increase in the warm water temperatuer allows a corresponding 10° increase in the operating temperature for the warm part of the cycle. As a result, efficiency increases to 7.4% instead of 5.7%, according to the previous equation.
  • a second advantageous factor results from the water vapor pressure, which increases rapidly with temperature. Since direct contacting is used, the air will be approximate ⁇ ly saturated with water at the higher temperature, thereby increasing its volume. Upon cooling, water vapor will condense. The effect then is to accentuate the change in volume and increase the net work output, especially at low operating pressures. For example, at 90°f. the water vapor will add about 5% to the gas volume. ,
  • the first column in Table 3 shows the new case at higher pressure, while the second column is the same case as in the second column of Table 2 using full sprays. Again, the volume of tanks at maximum expansion has been kept unchanged. Although the losses- are somewhat higher than the best case with partial sprays or with superheat, they can be further decreased by optimizing the design.
  • the water reservoir is "pressure balanced" : to the working gas zone or tank by opening a valve in connecting piping, whereby the water can now be fed to the contacting zone while requiring a pumping pressure build-up to overcome only the differential pressure across the sprays or other contacting devices, rather than the full system pressure.
  • the reservoir is filled while connected to the main tank to thereby return the gas to the working zone.
  • the reservoir can be a suitable confined zone within the main tank, since the volume of water used per cycle is only a small fraction of the tank volume.
  • Buoyance in tons per kilowatt output is a major consid- eration in that it reflects the relative size of equipment, as well as to some extent the cost.
  • a representative value for alternative designs is about 1.0 tons/KW when using indirect heat exchangers and ammonia as the working fluid.
  • cost per ton for the latter can be expected to be higher since the equipment is more complicated and requires more fabrication, and more labor to assemble.
  • the heat exchangers on warm and cold water may each have 120,000 tubes to be mounted in tube sheets and carefully sealed against leaks.
  • reference numeral 10 desig ⁇ nates an OTEC plant disposed at a mid-depth location below ocean surface 12.
  • OTEC plant 10 includes a double acting piston 14 operatively disposed in cylinder 16.
  • Piston 16 is
  • -BU connected to piston rods 18 and 20 which in turn are opera- tively connected to flywheel 22 disposed in housing 24.
  • Tower 26 communicates with OTEC plant 10 via housing 24 to provide access to the surface.
  • Cylinder 16 communicates at its left end with tank 28 which contains fan 30 and baffles 32 mounted in cylindrical housing 34.
  • Tank 28 is provided with a bottom drain line 36 which has a check valve 38 disposed therein.
  • Cylinder 16 also communicates at its right end with tank 40 which con- tains fan 42 and baffles 44 mounted in cylindrical housing 46.
  • Tank 40 is provided with a bottom drain line 48 which has a check valve 50 disposed therein.
  • Each of tanks 28 and 40 is equipped with means to spray alternately warm water and cold water therein as follows.
  • Tank 28 is provided with warm water supply line 52 which has a valve 54 and spray nozzle 56 therein.
  • Tank 28 is also provided with cold water supply line 58 which has a valve 60 and spray nozzle 62 therein.
  • Tank 40 is provided with warm water supply line 64 which has valve 66 and spray nozzle 68 therein.
  • Tank 40 is also provided with cold water supply line 70 which has a valve 72 and a spray nozzle 74 therein.
  • Flywheel 22 is operatively connected to a power input device, turbine 76, by means of a common drive shaft 78.
  • the method of operation of OTEC plant 10 is as follows, selecting as a starting point a condition wherein the piston 14 is at the extreme right in cylinder 16 and wherein tank 28 is in its maximum warm condition and tank 40 is at its maxi ⁇ mum cold condition.
  • warm water obtained by pumping from an upper location in the ocean is sprayed into tank 40 through v/arm water supply line 64 and spray nozzle 68 by opening valve 66 (which had been closed) .
  • Fan 42 recircu ⁇ lates air upward through baffles 44 countercurrent to the warm water, and downward around the outside of cylindrical housing 46.
  • cold water obtained by pumping from a lower location in the ocean is sprayed into tank 28 through cold water supply line 58 and spray nozzle 62 by opening valve 60 (which had been closed).
  • Fan 30 recirulates - 22 -
  • reference numeral 12 again refers to the ocean surface and reference numeral 26 refers to access tower 26 for OTEC plant 10.
  • Reference numerals 80 designate a series of solar collectors which may be con ⁇ structed of plastic, having an upper transparent portion 82 serving as a solar window and a lower portion 84 serving as a trough.
  • the solar collectors 80 are connected together in pairs by means of inlet manifold 86 and in alternating pairs by means of outlet manifold 88 as shown in FIGURE 2.
  • Inlet manifold 86 is connected to inlet line 90 and outlet manifold 88 is connected to outlet line 92.
  • the solar collectors 80 are operated in combination with OTEC plant 10 as follows.
  • Used warm water discharged alter ⁇ natively from tanks 28 to 40 via drain lines 36 and 48 is fed to inlet line 90 and then via inlet manifold 86 to the individual solar collectors 80 wherein the water is warmed as a result of sunlight through upper transparent portion 82 while the water passes through troughs 84.
  • the warmed water is then collected from the solar collectors 80 through outlet manifold 88 and returned to OTEC plant 10 where it is fed alternatively into tanks 28 and 40 via warm water supply lines 52 and 64 respectively as described in detail in connection with FIGURE 1.
  • Net Thermal Efficiency % 2.80 3.5 Buoyancy is quite low as a result of the relatively high pressure, meaning that the equipment size is small. It will be designed to stand the differential pressure encountered, but not the full operating pressure as would be necessary for surface equipment at the same high pressure. A cycle length of 0.002 hours has been used to allow comparison with pre ⁇ vious examples, but this could easily be increased to 0.004 or more while still maintaining a very favorable low buoy ⁇ ancy. Increased pressure level, and higher pressure ratios are thus useful ways to minimize buoyancy and equipment size. As mentioned before, air solubility in water at these high pressures should be taken into consideration.
  • air solubility is controlled by using a form of indirect heat exchange, but one that does not transfer heat through a costly metal surface, as in a tubular exchange, which would be seriously affected by fouling. Instead, water is flowed through a packed bed to warm the packing. Water flow is then stopped, and after draining, the working gas is circulated through the warm bed. In this particular design, separate beds are provided for warm and cold operations. A large surface area can be provided at low cost, and fouling does not seriously impair heat transfer to the gas. Solu ⁇ bility of air in the water is not a problem since there is only minor direct contact between water and air.
  • reference numeral 100 desig ⁇ nates an OTEC plant constructed in accordance with the present invention and designed to operate on the ocean bottom 112.
  • OTEC plant 100 is provided with a double acting piston 114 which is operatively disposed in cylinder 116.
  • Piston 114 is operatively connected by means of connecting rods 118 and 120 to flywheel 122 disposed in housing 124.
  • Flywheel 122 is operatively connected to a turbine 126 by means of common drive shaft 128.
  • Cylinder 116 communicates at its right end with the top of tank 130 which is provided with a plurality of baffles 132 designed to give staging and limit mixing between water and air.
  • Tank 130 is supported on the ocean bottom 112.
  • Cylinder 116 communicates at its left end with the top tank 134 which is provided with a plurality of baffles 136 designed similar to baffles 132.
  • Tank 134 also is supported on oceam bottom 112.
  • OTEC plant 100 also includes a cold water contacting chamber 140 which contains therein a bed of conventional packing material 142 and a circulating fan 144 in its upper, inner portion.
  • Chamber 140 is provided at its upper portion with a cold water inlet line 146 and with a cold water outle line 148 at its bottom containing check valve 149.
  • OTEC plant 100 also .includes a warm water contacting chamber 150 which contains therein a bed of conventional packing materia 152, similar to that contained in chamber 140, and a circu ⁇ lating fan 154 in its upper, inner portion.
  • Chamber 150 is provided at its upper portion with a warm water inlet line 156 and with a warm water outlet line 158 at its bottom containing check valve 159.
  • Chamber 140 is provided at its top with a gas outlet line 160 and its bottom with a gas inlet line 162.
  • Chamber 150 is provided at its top with a gas outlet line 164 and at its bottom with a gas inlet line 166.
  • Tank 130 is provided at its top with a gas inlet line 168 and at its bottom with gas outlet line 170 having valve 171 therein.
  • Tank 134 is provided at its top with a gas inlet line 172 and at its bottom with a gas outlet line 174 having valve 175 therein.
  • Gas outlet line 160 is provided with a three-way valve 176 which communicates with gas outlet line 168 and with lin 178 which in turn communicates with gas inlet line 172 havin a valve 173 therein..
  • Gas outlet line 164 is provided with a three-way valve 180 which communicates with gas inlet line 172 and also with line 182 which in turn communicates with gas inlet line 168 having valve 169 therein.
  • Gas outlet lin 170 is provided with three-way valve 184 which communicates with gas inlet line 162 and with line 186 which in turn communicates with gas inlet line 166.
  • Gas outlet line 174 i provided with three-way valve 188 which communicates with ga inlet line 166 and with line 190 which in turn communicates with gas inlet line 162.
  • Oirt OTEC plant 100 operates as follows, commencing with piston 114 at its far right position in cylinder 116.
  • Tank 130 and chamber 140 at this point are each in their cold condition and tank 134 and chamber 150 at this point are each in their warm condition.
  • chamber 140 will always be in a cold condition by reason of cold water being introduced through inlet line 146 to the top of the bed of packing material 142 and withdrawn through outlet line 148.
  • chamber 150 will always be in a warm condition by reason of warm water being introduced through inlet line 156 to the top of the bed of packing material 152 and withdrawn through outlet line 158.
  • valves 169 and 171 are open and three-way valves 176 and 184 are set to circulate air through chamber 140 and tank 130 by means of fan 144.
  • valves 173 and 175 are open and three-way valves 180 and 188 are set to circulate air through chamber 150 and tank 134.
  • valves 169, 171, 173. and 175 are shut off and warm water is passed through chamber 150 to warm the bed 152 to substantially warm water temperature. Similarly, cold water is passed through chamber 140 to cool the bed 142 to substantially cold water temperature. " The valves 169, 171, 173 and 175 are now opened and three-way valves 176 and 188 are set to circulate air through chamber 140 and tank 134 by means of fan 144 to warm tank 130. Likewise, three-way valves 180 and 184 are set to circulate air through chamber 150 and tank 130 by means of fan 154 to cool tank 134.
  • piston 114 moves to the left in chamber 116, driving flywheel 122 by means of connecting rods 118 and 120. A part of the energy so produced is stored in flywheel 122 with a portion of the energy being taken out in the form of useful work by driving turbine 126 by means of drive shaft 128.
  • the valves 169, 171, 173 and 175 are shut off to stop circulation of air through the beds.
  • cold water is circulated by pumping through chamber 140 by means of lines 146 and 148 to cool bed 142 and warm water is circula ⁇ ted by pumping through chamber 150 by means of lines 156 and 158 to warm bed 152.
  • Bed 142 is then drained through line 148 and check valve 149 and bed 152 is drained through line 158 and check valve 159.
  • valves 169, 171, 173 and 175 are opened and three- way valves 176 and 184 are set to circulate the warm air in tank 130 through chamber 140 and tank 130 by means of fan 14 to thereby cool the air.
  • three-way valves 180 and 188 are set to circulate the cold air in tank 134 through chamber 150 and tank 134 by means of fan 154 to thereby heat the air.
  • heating the air in tank 134 and its expansion and cooling the air in tank 130 and its contractio piston 114 moves to the right in chamber 116, driving flywhe 122 by means of connecting rods 118 and 120.
  • piston 114 At full travel, piston 114 is at the far right and is a the starting position described above. The above process is then continued until flywheel 122 reaches its designed speed at which point the energy output of the otec plant 100 is taken essentially completely by turbine 126.
  • FIGURE 4 The system arrangement using a "free piston”/water turbine is illustrated in FIGURE 4.
  • the lower side of the piston connects to the air working chamber, while the zone above the piston is kept filled with water supplied from a low pressure reservoir.
  • the piston moves through the cylind er and is sealed at its edges to prevent substantially leak ⁇ age.
  • At the top of the cylinder are connections to low and high pressure water reservoirs or manifolds, each connection provided with a suitable check valve which allows flow in only one direction.
  • this system can be combined with a single or double-acting gas piston.
  • the gas piston can be ' used to drive a water piston of smaller diameter to give increased pressure differential and thereby permit using a smaller and less costly water turbine-.
  • reference numeral 300 desig ⁇ nates an OTEC plant designed to operate at a location at the ocean surface 312.
  • OTEC plant 300 includes a free piston 314 which is operatively disposed in vertical cylinder 316.
  • At its upper end cylinder 316 communicates with a high pressure water line 318 provided with a check valve 320 and with a lo 'pressure water line 322 provided with a check valve 324.
  • High pressure water line 318 communicates with the high pressure side of turbine- 326 and low pressure wat r line 322 communicates with the ' low pres ' sure ' side ' of turbine.326.
  • cylinder 316 ' communicates via conduit 327 with ' a. tank .328 which ' ' is provided in its upper portion 5 with a plurality of vertically spaced baffles ' 330.
  • tank 328 is provided' ith a " contacting chamber .332 which contains a plurality o .vertically spaced gas- liquid contacting trays 334.
  • chamber 332 is provided with " a fan 336 and communicates with a
  • OTEC plant 300 The " operation of OTEC plant 300 is as follows, starting at the point where "piston 314 is at its lowermost position in cylinder 316 and where cylinder 316 is. filled with water above " piston 314.. At this condition, tank 328 is at its
  • Fan 336 is operating continuously and is circulating air up through conduit 338 to the top of tank 328 and then downwardly around the " outside ' of conduit 338 and chamber 332
  • gas within the tank is alternately warmed and cooled by water sprays causing the gas to expand and then contract, thereby moving a floating piston at the bottom of the tank.
  • the arrangement allows the piston to drive the flywheel while minimizing friction.
  • This particu ⁇ lar example operates with a relatively low pressure ratio between maximum and minimum pressures, resulting in a relatively high proportion of the heat load being as sensibl heat for warming or for cooling the gas.
  • the water streams can then be cooled or warmed over a greater temperature range since greater countercurrent contacting becomes practical. Flow rates of water are thereby decreased.
  • a variation is to flow the gas from a tank at higher pressure (warm) to one at lower pressure (and cold) through a turbine which recovers energy.
  • reference numeral 400 desig ⁇ nates an OTEC plant designed in accordance with the present invention for operating at a location at the ocean surface.
  • OTEC plant 400 is provided with a floating piston 414 opera ⁇ tionally disposed in vertically aligned cylinder 416.
  • Piston 414 is operatively connected by means of connecting rods 418 and 420 to flywheel 422 which in turn is operatively connected to turbine 424 by means of drive shaft 426.
  • Flywheel 422 and turbine 424 are disposed in the bottom portion of tank 430 which is provided in its upper portion with a plurality of vertically spaced horizontal contacting devices 432 such as baffles, trays or the like. Flywheel' 422 and turbine 424 have a shield 426 disposed above them to pro ⁇ tect them against water passing downwardly in tank 430. At the uppermost part of tank 430, there is provided a manifold 434 having a plurality of water sprays 436. Manifold 434 communicates with conduit 438 which in turn communicates with cold water supply line 440 having valve 442 and warm water supply line 444 having valve 446.
  • OTEC plant 400 operates as follows starting with piston 414 at its top position. At this point, tank 430 is in its cold condition with valve 442 open and cold water being sprayed into the top of tank 430 through lines 440 and 438, manifold 434 and sprays 436. Valve 442 is then closed to shut off the supply of cold water and the water is drained out of tank 430 and cylinder 416 around piston 414 which is loose fitting.
  • FIGURE 6 illustrates an OTEC plant comprising a U-shape OTEC plant vessel ' 500 having legs 502 and 504.
  • Floating pistons 505 and 506- are disposed respectively in legs 502 an 504 of the vessel 500 and are supported by water " therein.
  • Compressible packing 508 is disposed in the upper part of le 502 above floating piston 504 and compressible packing 510 i disposed in the upper part of leg 504 above floating piston 506.
  • the " compressible packing may comprise a foamed plastic having a .density of 1 to 10 lb./cubic ft. " , for example, or may comprise horizontal layers of screens spring mounted.
  • a water spray head 512 is disposed in leg 502 in the upper portion thereof above compressible packing 508.
  • a water spray head is disposed in leg 504 in the uppe portion thereof above compressible packing 510.
  • Vessel 500 is provided with sources of cold and warm water which may be alternatively introduced into leg 502 through spray head 512 by means of conduit 514 containing valve 516 and into leg 50 through"spray head 518 by means of conduit 520 containing valve 522.
  • Leg 502 is provided at its top with a conduit 524 havin a valve . 526, which ' communicates with a turbine (not shown).
  • leg 504 is provided at its top with a conduit 528 having a valve 530, which communicates " with said turbine.
  • OTEC plant 500 operates in the same basic manner as do the " other " OTEC plants described hereinbefore. " Thus, - 35 -
  • warm water may be introduced into leg.502 and cold water ' may be introduced into leg “ 504 to move-the " OTEC system into the position shown in FIGURE 7 wherein packing 508 is in its expanded position and packing 510 is in its compressed 5 position.
  • the spongelike " packing is added within the cylin ⁇ der to fill the entire ' cylinder ' ' and provide temperature control and good heat transfer so that the gas can be kept • ' captive.
  • the sponge " is wet with cold water before
  • a preferred" alternative is to have both warm and cold packings always within the ' cylinder, each maintained at its temperature " so that the " packing does ' not have " to be heated or
  • Net power is withdrawn as follows. At the point of maximum pressure a" small portion of high pressure gas is taken " out (e:g., 5%) and passed through ' the turbine and then returned to another cylinder that is at its minimum pressure.
  • 35 can be " held by a brake " when ' it stops, with no loss in efficiency. It then ' reverses ' direction each time it stops.
  • OTEC plant 500 may be provided optionally with valve 532 which can be closed at the end of each stroke to slow down the cycle and allow more time to adjust the temperature of the packing when switching between hot and cold.
  • valve 532 will be wide open.
  • the length of the liquid legs may be set to control the cycle length. Thus, for example, a longer length gives more inertia and therefore a longer cycle.
  • excess water may be drained out at a proper point in the cycle through conduit 534 having valve 536.
  • FIGURE 7 shows an improvement on the cold water pipe design for OTEC plants.
  • Such plants have manageable mechan ⁇ ical design problems in still water but in most practical cases there are variable water currents at different levels that impact on the pipe. Designing for these forces results in very high costs.
  • the present invention overcomes these forces by placing "thrusters" at spaced points vertically to offset the currents.
  • the thrusters can use propellors, moto driven, or a jet of water directed downstream.
  • the water ca come from OTEC discharge.
  • OTEC plant 600 which is disposed toward the surface 602 of the ocean is connected to cold water pipe 604 having an upper end 606 and a lower end 608 which is disposed above ocean bottom 610.
  • Cold water pipe 604 is at least partially supported by a plurality of buoyancy rings 612 and 614 disposed about the outside surfac thereof at spaced points.
  • Thruster 616 is also disposed on the outersurface of cold water pipe 604 and includes rotatable rings 618 and 620 motor 622 which drives propellor 624, and rudder 626.
  • Cold water pipe 604 is also provided with a second propellor 628 driven by motor 630 so as to maintain a slight positive pres sure inside cold water pipe 604 to thereby maintain the wall thereof in tension rather than compression to avoid their collapse due to water pressure.
  • the propellor 624 pulls the cold water pipe 604 upstream and the rudder 626 provides a self-aligning mechanism to maintain the thruster system in the proper orientation.
  • other 5 equivalent mechanisms may be used such as a water jet, for example.
  • FIGURE 8 shows a combination of an OTEC plant 700 and a mariculture system 702 which includes a plurality of culture vessels 704, 706" and 708 designed to produce different types of sea food at different' temperatures.
  • culture vessel 704 may be " a solar pond designed to operate at a tem ⁇ perature of 80° to 90°F. to raise shrimp, kelp, mullet and other fish.
  • culture vessel 706 may be designed to operate at a temperature of 80°F. to raise shrimp at an optimum temperature for their culture.
  • culture vessel 708 may be designed to operate at a temperature of 60 to 65° to raise lobster at an optimum temperature for their culture. In this operation of the system shown in FIGURE 7, water at a temperature of about 90°F.
  • OTEC plant 700 is introduced into OTEC plant 700 by means of warm water conduit 710. Water from the OTEC plant may be withdrawn through conduit 712 at a ' temperature of about 80°F. and introduced into culture " vessel 706 through conduit 714. The water from culture vessel 706 (including waste products and .unused food) exits therefore through con- duit '716 and is then passed through conduit 718 to culture vessel 704.
  • ' vessel 702 may be a solar pond which is designed to increase the temperature of the water as it passes therethrough from 80° to 90°F.
  • Water removed from OTEC plant 700 may also be passed through conduit 720 into culture vessel 708.
  • Cold water from the ocean may then be introduced through conduit 722 into vessel 708 in a - proportion sufficient to reduce the overall temperature to about 60 ° to 65°F.
  • Water exiting from vessel 708 may then be passed through conduits 724 and 718 to culture vessel 704.
  • the water has absorbed oxygen from the high pressure gas to several times that of normal seawater (dissolved oxygen is a major limiting factor in setting the growing capacity of mariculture systems) , and
  • the mariculture tank • are located at sufficient depth to avoid this; water from OTEC may or may be fully saturated. Wastes are returned to surface pond in sunlight where algae grow to feed oysters, etc., along with kelp which calms the water and is harvested Wastes provide nutrients along with other sources such as nutrients in water from the bottom. In case of storm, the •facilities may be lowered to 30-100 feet for protection. It will be attractive " to operate mariculture, or more broadl aquaculture, at pressures such as 2-20 atmospheres and add air or oxygen " to increase solubility of oxygen in the water. This will allow higher production rate or yield per acre per year, which is needed for best economics. It also applies t all OTEC systems but is especially desirable in the case of the present invention as loss of air due to solubility is inherent in the present invention and is a debit for OTEC, but is more than offset by the credit in aquaculture.
  • Nitrogen also dissolves in the water and if aquaculture is at too low a pressure then nitrogen bubbles are released within the animals, causing the well-known divers "bends", as referred to above. Therefore, the pressure should not be much below that corresponding to nitrogen saturation. Nitro gen is less soluble in water than oxygen, and the contacting may not achieve saturation. The main point is to avoid supersaturation of water with nitrogen.
  • Part or all of the facilities may be located on land, and solar heating is particularly effective for heating whil using cool ocean water for cooling.
  • the following three ⁇ zr types of solar heating may be considered for use in ' these systems of the present invention:
  • the solar collectors can concentrate or focus the . sun to give a temperature of up to 200-500°F. Vapor pressure of water adds to the work output, but oil or other liquid with low vapor pressure improves efficiency and may be preferred to cut the area of solar collectors which may take 100-500 acres for a plant sized to produce 30 megawatts of electri ⁇ city.
  • Fresh water can be recovered in the cooling part of the cycle by having a closed system on the cool water. This requires indirect cooling of this water as by heat exchange with cool ocean water.
  • the warm water can be ocean water heated in solar collectors, and directly contacts the gas.
  • the system is also good, for pumping water. By flowing more water in at low pressure and out at high, the system gives pumping without additional mechanical pumps.
  • An improved use of solar collectors is to operate them in reverse at night to further cool the cold stream, by radiation to the sky. Normally, they are used only in the daytime and not at night. Some storage of cold and/or warm water may be desirable. The principle is similar to frost forming on a still night when the temperature is well above freezing.
  • Mariculture can operate once-through on the water so that it does not have to be cleaned up, or it can be recycled in a closed circuit, in which case heat must be added to maintain the temperature. Solar heating then cooperates well with mariculture in the solar pond. If a conventional OTEC

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Abstract

Systeme de conversion d'energie pour obtenir de l'energie utilisable a partir des gradients thermiques de l'ocean (12) ou de sources a bas niveau de chaleur tels que solaires, geothermiques ou autres, en utilisant de l'eau chaude pour rechauffer un gaz de travail, confine tel que de l'air, de maniere telle qu'une augmentation de pression resulte du rechauffement du gaz en s'arrangeant pour que cette expansion deplace un piston (14) ou autre dispositif d'extraction d'energie et puis en refroidissant le gaz et en le comprimant en retour vers ses conditions initiales, tout en le mettant en contact directement ou indirectement avec de l'eau plus froide pour ainsi reduire le travail necessaire a la recompression. Un travail utile net resulte de la difference entre le travail d'expansion a plus haute temperature et le travail de recompression a plus basse temperature.
PCT/US1978/000204 1978-12-12 1978-12-12 Systeme de conversion d'energie pour obtenir de l'energie utilisable a partir de sources a bas niveau de chaleur WO1980001301A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US1978/000204 WO1980001301A1 (fr) 1978-12-12 1978-12-12 Systeme de conversion d'energie pour obtenir de l'energie utilisable a partir de sources a bas niveau de chaleur

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WOUS78/00204 1978-12-12
PCT/US1978/000204 WO1980001301A1 (fr) 1978-12-12 1978-12-12 Systeme de conversion d'energie pour obtenir de l'energie utilisable a partir de sources a bas niveau de chaleur

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO20081742L (no) * 2008-04-10 2009-10-12 Energreen As Framgangsmåte og apparat for å frambringe væskestrømning i en rørledning
US8037679B2 (en) 2009-06-29 2011-10-18 Lightsail Energy, Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
US8191361B2 (en) 2009-06-29 2012-06-05 Lightsail Energy, Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
EP3783222A1 (fr) * 2019-08-21 2021-02-24 Taiwan Happy Energy Co., Ltd. Dispositifs, systèmes et procédés pour générer de l'énergie
WO2021146181A1 (fr) * 2020-01-16 2021-07-22 Innovator Energy, LLC Production d'énergie à l'aide de glace ou d'autres fluides congelés en tant que source de chaleur

Citations (5)

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Publication number Priority date Publication date Assignee Title
US3995160A (en) * 1975-05-06 1976-11-30 Carnegie-Mellon University Method and apparatus for obtaining electrical power from sea water
US4014279A (en) * 1976-04-28 1977-03-29 Trw Inc. Dynamic positioning system for a vessel containing an ocean thermal energy conversion system
US4055145A (en) * 1976-09-29 1977-10-25 David Mager System and method of ocean thermal energy conversion and mariculture
US4134265A (en) * 1977-04-26 1979-01-16 Schlueter William Bryan Method and system for developing gas pressure to drive piston members
US4170878A (en) * 1976-10-13 1979-10-16 Jahnig Charles E Energy conversion system for deriving useful power from sources of low level heat

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3995160A (en) * 1975-05-06 1976-11-30 Carnegie-Mellon University Method and apparatus for obtaining electrical power from sea water
US4014279A (en) * 1976-04-28 1977-03-29 Trw Inc. Dynamic positioning system for a vessel containing an ocean thermal energy conversion system
US4055145A (en) * 1976-09-29 1977-10-25 David Mager System and method of ocean thermal energy conversion and mariculture
US4170878A (en) * 1976-10-13 1979-10-16 Jahnig Charles E Energy conversion system for deriving useful power from sources of low level heat
US4134265A (en) * 1977-04-26 1979-01-16 Schlueter William Bryan Method and system for developing gas pressure to drive piston members

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO20081742L (no) * 2008-04-10 2009-10-12 Energreen As Framgangsmåte og apparat for å frambringe væskestrømning i en rørledning
US8037679B2 (en) 2009-06-29 2011-10-18 Lightsail Energy, Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
US8087241B2 (en) 2009-06-29 2012-01-03 Lightsail Energy, Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
US8191361B2 (en) 2009-06-29 2012-06-05 Lightsail Energy, Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
US8201402B2 (en) 2009-06-29 2012-06-19 Lightsail Energy, Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
US8201403B2 (en) 2009-06-29 2012-06-19 Lightsail Energy Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
US8215105B2 (en) 2009-06-29 2012-07-10 Lightsail Energy Inc. Compressed air energy storage system utilizing two-phase flow to facilitate heat exchange
EP3783222A1 (fr) * 2019-08-21 2021-02-24 Taiwan Happy Energy Co., Ltd. Dispositifs, systèmes et procédés pour générer de l'énergie
WO2021146181A1 (fr) * 2020-01-16 2021-07-22 Innovator Energy, LLC Production d'énergie à l'aide de glace ou d'autres fluides congelés en tant que source de chaleur
US11118846B2 (en) 2020-01-16 2021-09-14 Innovator Energy, LLC Power generation using ice or other frozen fluids as a heat source

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