Patent Publication Number: US-7898102-B2

Title: Hydrocratic generator

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part application of U.S. patent application Ser. No. 11/158,832 filed Jun. 21, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 11/096,981 filed Mar. 31, 2005, which is a continuation-in-part application of U.S. patent application Ser. No. 10/777,458 filed Feb. 12, 2004, which is a continuation-in-part application of U.S. patent application Ser. No. 10/357,007 filed Feb. 3, 2003 and also a continuation-in-part of U.S. patent application Ser. No. 10/404,488 filed Mar. 31, 2003. U.S. patent application Ser. No. 10/357,007 is continuation-in-part of, and U.S. patent application Ser. No. 10/404,488 is a continuation of, U.S. patent application Ser. No. 09/952,564 filed Sep. 12, 2001, now U.S. Pat. No. 6,559,554, which is a continuation-in-part of U.S. patent application Ser. No. 09/415,170 filed Oct. 8, 1999, now U.S. Pat. No. 6,313,545. U.S. patent application Ser. No. 09/415,170 itself claims the benefit of Provisional Patent Applications Nos. 60/123,596 filed Mar. 10, 1999 and 60/141,349 filed Jun. 28, 1999. All of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to hydraulic power generation systems and, in particular, to an apparatus and method for generating power using a novel pseudo-osmosis process which efficiently exploits the osmotic energy potential between two bodies of water having different salinity concentrations. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an aspect to provide an improved apparatus and method for generating power using a novel forward osmosis process which efficiently exploits the osmotic energy potential between two bodies of water having different salinity concentrations. 
     Advantageously, the method and apparatus of the present invention does not require the use of a semi-permeable membrane or other specially formulated material, nor does it require heating or cooling of the fresh water or salt water solution. Moreover, the present invention may recover energy from a wide variety of fresh water sources, including treated or untreated river run-off, treated waste-water run-off or effluent, storm-drain run-off, partly contaminated fresh water run-off, and a wide variety of other fresh water sources. Thus, the present invention is well suited to large scale power production in a wide variety of geographic locations and under a wide variety of conditions. The invention has particular advantage for use in remote regions where electrical power generation by conventional means may be commercially infeasible or impractical. 
     According to one aspect of the invention, there is provided a mixing apparatus for mixing first salinity fluid with a second salinity fluid, the mixing apparatus comprising: a down tube having a side wall, an open upper end and an open lower end, and a plurality of apertures selectively located in the side wall of the down tube, at least some of the apertures having an arm member with an opening therein about the aperture to facilitate inflow of fluid to the down tube through the openings; a fluid inlet and a fluid outlet at the open upper end and open lower end respectively of the down tube, wherein the first salinity fluid in use enters the down tube through the fluid inlet and the apertures and is discharged therefrom through the fluid outlet; and a feed tube having a first end connectable to a source of second salinity fluid having a salinity different to the first salinity fluid and a second end for introducing the second salinity fluid to the fluid inlet of the down tube to mix the first salinity fluid with the second salinity fluid to form a fluid mixture. 
     According to another aspect of the invention, there os provided a hydrocratic generator system comprising: a container having an upper chamber and a lower chamber sealed from the upper chamber, the upper chamber for accommodating a body of fluid having a first salinity; a first feed inlet in the upper chamber of the container through which the fluid having a first salinity can be discharged into the container; a down tube having an upper inlet end and a lower outlet end, the down tube being located primarily in the upper chamber of the container with the outlet end thereof discharging into the lower chamber; a second feed inlet through which fluid having a second salinity can be discharged into the upper chamber of the container such that the fluid having the second salinity mixes with the fluid having the first salinity in the down tube; and a discharge means from the lower chamber to facilitate discharge of the mixed fluids. 
     According to yet another aspect of the invention, there is provided a mixing apparatus for mixing first salinity fluid with a second salinity fluid, the mixing apparatus comprising: a down tube having a side wall and an open upper end and an open lower end, the down tube having a funnel shaped portion at the upper end, a cylindrical portion below the funnel shaped portion, a substantially square portion below the cylindrical portion and a venturi tube portion below square portion. 
     In yet another aspect of the invention, there is provided a mixing apparatus for mixing first salinity fluid with second salinity fluid, the mixing apparatus comprising: a down tube having a side wall and an open upper end and an open lower end, the side wall being comprised of a meshed screen portion and solid portion below the meshed screen portion; a fluid inlet and a fluid outlet at the open upper end and open lower end respectively of the down tube, wherein the first salinity fluid in use enters the down tube through the fluid inlet and meshed screen portion and is discharged therefrom through the fluid outlet; a feed tube having a first end connectable to a source of second salinity fluid having a salinity different to the first salinity fluid and a second end for introducing second salinity fluid to the fluid inlet of the down tube to mix the first salinity fluid with the second salinity fluid to form a fluid mixture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram representation of a conventional forward osmosis process through a semi-permeable membrane; 
         FIG. 1B  is a schematic diagram representation of a conventional reverse osmosis process through a semi-permeable membrane; 
         FIG. 2  is a schematic representation of an experimental up tube upwelling apparatus for use in accordance with the present invention; 
         FIG. 3  is a graph of theoretical power recovery for different sized down-tubes and fresh water flow rates using the experimental upwelling device of  FIG. 2 ; 
         FIG. 4  is a schematic representation of one embodiment of a hydrocratic generator having features and advantages in accordance with the present invention; 
         FIG. 5  is a schematic representation of an alternative embodiment of a hydrocratic generator having features and advantages in accordance with the present invention; 
         FIG. 6  is a schematic representation of a further alternative embodiment of a hydrocratic generator having features and advantages in accordance with the present invention; 
         FIG. 7A  is a schematic representation of a further alternative embodiment of a hydrocratic generator having features and advantages in accordance with the present invention; 
         FIG. 7B  is a side view of the up tube of  FIG. 7A , showing the slots in the side of the up tube; 
         FIG. 7C  is a sectional view from below of the shaft support of  FIG. 7A ; 
         FIG. 7D  is a sectional view from above of the vane drum of  FIG. 7A ; 
         FIG. 8A  is a schematic representation of a further alternative embodiment of a hydro-osmotic generator having features and advantages in accordance with the present invention; 
         FIG. 8B  is a side view of the up tube of  FIG. 8A  showing two sets of slots in the side of the up tube; 
         FIG. 8C  is a sectional view from below of the shaft support of  FIG. 8A ; 
         FIG. 8D  is a sectional view from above of the vane drum of  FIG. 8A ; 
         FIG. 9A  is a schematic view of an up tube with an open lower end with an alternative embodiment of a down tube having a plurality of holes in the sides and the outlet end, having features and advantages in accordance with the present invention; 
         FIG. 9B  is a sectional view from below of the up tube and the outlet end of the down tube of  FIG. 9A ; 
         FIG. 10A  is a schematic view of an up tube with an open lower end with an alternative embodiment of the down tube with a plurality of secondary down tubes having holes in the sides and the outlet end, having features and advantages in accordance with the present invention; 
         FIG. 10B  is a sectional view from below of the up tube and the outlet end of the down tube of  FIG. 10A  showing the plurality of secondary down tubes and the holes on the outlet ends of the secondary down tubes; 
         FIG. 11  is a schematic view of an up tube with an open lower end with an alternative embodiment of the down tube with a plurality of secondary down tubes, having features and advantages in accordance with the present invention; 
         FIG. 12  is a schematic view of a down tube with a rotating hub and spoke outlets with no up tube; 
         FIG. 13  is a schematic view of a down tube with a rotating hub and spoke outlets with an up tube, having features and advantages in accordance with the present invention; 
         FIG. 14  is a schematic view of a portion of an up tube comprising a plurality of concentric up tubes, having features and advantages in accordance with the present invention; 
         FIG. 15  is a schematic representation of a modified up tube having features and advantages in accordance with the present invention; 
         FIG. 16  is a schematic illustration of a possible large-scale commercial embodiment of a hydro-osmotic generator having features and advantages in accordance with the present invention; 
         FIG. 17  is a cutaway view of the turbine and generator assembly of the hydro-osmotic generator of  FIG. 12 ; 
         FIG. 18  is a schematic view of an up tube with an open lower end, with an alternative embodiment of the rotating down tube, extending substantially into the up tube, and having holes and turbines mounted thereon, having features and advantages in accordance with the present invention; 
         FIG. 19A  is a schematic view of an up tube with a closed lower end, with an alternative embodiment of the rotating down tube, extending substantially into the up tube, and having holes and turbines mounted thereon, having features and advantages in accordance with the present invention; 
         FIG. 19B  is a side view of the up tube shown in  FIG. 19A ; 
         FIG. 20  is a schematic view of an up tube with an open lower end, with an alternative embodiment of the rotating down tube, extending substantially into the up tube, and having holes and turbines mounted thereon, with rotating up tube and down tube, having features and advantages in accordance with the present invention; 
         FIG. 21  is a schematic view of an up tube upwelling apparatus in accordance with the present invention wherein a rotating helical screw is used to generate the power instead of a plurality of fan blades, having features and advantages in accordance with the present invention; 
         FIG. 22A  is a side view of an alternative embodiment of a fan blade used in accordance with the present invention; 
         FIG. 22B  is a schematic view showing the under portion of the fan blade illustrated in  FIG. 22A  of the drawings; 
         FIG. 23  is a schematic representation showing a further device of the invention, including multiple turbines; 
         FIG. 24   a  is a schematic representation of yet a further embodiment of the invention, including a wrapped tube; 
         FIG. 24   b  is a cross-section through a part of the apparatus as shown in  FIG. 24   a;    
         FIG. 25  is a schematic representation showing yet a further embodiment of the invention, including a sleeve tube; 
         FIG. 26  is a schematic representation showing yet a further embodiment of the invention including a plurality of differently located feed tubes; 
         FIG. 27   a  is a schematic representation showing a further embodiment of the invention, including feed tubes incorporating rings; 
         FIG. 27   b  is a schematic representation showing a cross-section through the device of the invention as shown in  FIG. 27   a;    
         FIG. 28  is a schematic representation of yet a further embodiment of the invention used in the context of a power generator using sewage or sanitation effluent and may use a brine line from a water desalinization plant; 
         FIG. 29  is a schematic view of a further embodiment of the hydrocratic generator of the invention; 
         FIG. 30  is a schematic view of yet a further embodiment of the hydrocratic generator of the invention; and 
         FIG. 31  is a view from the bottom of the brine line shown in  FIG. 30  of the drawings; 
         FIG. 32  is a schematic top view of a further embodiment of a hydrocratic generator in accordance with the invention; 
         FIG. 33  is a side view of the hydrocratic generator shown in  FIG. 32  of the drawings; 
         FIG. 34  is a top view of a further embodiment of a hydrocratic generator in accordance with the principles of the invention; 
         FIG. 35  is a side view of the hydrocratic generator shown in  FIG. 34  of the drawings; 
         FIG. 36  is a schematic side view of a hydrocratic generator in accordance with another embodiment of the invention; 
         FIG. 37  is a schematic side view of a still further embodiment of a hydrocratic generator in accordance with the present invention; 
         FIG. 38  is a schematic side view of still a further embodiment of the hydrocratic generator of the invention; 
         FIG. 39  is a schematic view of a tube with substantially uniform diameter; 
         FIG. 40  is a schematic view of a tube having a tapering diameter; 
         FIG. 41  is another schematic view of a tube having a tapering diameter and a series of successively wider tubes; 
         FIG. 42  is a schematic representation of yet another embodiment of the invention; 
         FIG. 43  is a schematic view of a hydrocratic generator in accordance with another embodiment of the invention, contained in a reservoir; 
         FIG. 44  is a schematic view of a hydrocratic generator in accordance with another embodiment of the invention, when constructed in the ocean; 
         FIG. 45  is a schematic illustration of a hydrocratic engine with features and structure in accordance with yet a further embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     When solvent fluids having differing osmotic potentials are contacted and mixed with each other energy is released. This released energy results from an increase in entropy of water (or other solvent) when it is transformed from its pure (fresh-water) state to its diluted (salt-water) state. Thus, an entropy gradient is created whenever two bodies of water or other solvents having differing solute concentrations are brought into contact with one another and begin to mix. This entropy gradient can be physically observed and measured in the well-known phenomena known as osmosis. 
     Because the term “osmosis” is associated with a membrane, the term “hydrocrasis” is used as a term for the situation when solvent fluids having differing osmotic potentials are contacted and mixed with each other in the absence of a membrane. 
       FIG. 1A  schematically illustrates conventional forward osmosis through a semi-permeable membrane. Forward osmosis results in the flow of water  10  (or other solvent) through a selectively permeable membrane  12  from a lower concentration of solute  14  to a higher concentration of solute  14 . 
       FIG. 1B  illustrates the condition of reverse osmosis whereby water (or other solvent)  10  under the influence of external pressure is forced through a selectively permeable membrane  12  from a higher concentration of solute  14  to a lower concentration of solute  14 , thus squeezing out or extracting the pure solvent  10  from the solute  14 . Reverse osmosis is widely used in water purification and desalinization plants throughout the world. Reverse osmosis consumes work energy. 
     The osmotic energy potential to be gained from remixing fresh water into saline ocean water is significant—about 1.4 kJ/kg of fresh water, or the equivalent of about 290 m-head of water for a conventional hydropower system. If this source of stored energy could somehow be efficiently exploited, it could result in the production of enormous amounts of inexpensive electrical power from a heretofore untapped and continually renewable energy resource. 
     During recent prototype testing of a similar upwelling device it was discovered, surprisingly, that the amount of upwelling flow achieved in terms of kinetic energy of the overall mass flow was in excess of the input energy into the system in terms of the buoyancy effect and kinetic energy resulting from the fresh water introduced into the up tube. Subsequent experiments using a modified upwelling device have confirmed that the total hydraulic energy output of such system significantly exceeds the total hydraulic energy input. 
     While an exact explanation for this observed phenomena is not fully appreciated at this time, it is believed that the excess energy output is somehow attributable to the release of osmotic energy potential upon remixing of the fresh water and the salt water in the up tube. 
     Example 1 
     The apparatus shown in  FIG. 2  was used to measure observed flow rates in the up tube  40  with different fresh water flow rates introduced into the down tube  20 . Table 1 is a compilation of the results for flow rates at various points in the up tube  40  with two different flow rates of fresh water in the down tube  20 . The flow rate at Point 1, the flow rate of fresh water from the reservoir, and the salinity at Point 2 at the outlet end  44  of the up tube  40  were measured parameters. The flow rate at Point 3, the outlet end  24  of the down tube  20 , was the same as the flow rate at Point 1. The remaining flow rates were calculated using the equations discussed above. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Flow Rates at Various Locations in the Up Tube 
               
            
           
           
               
               
               
            
               
                 Height of 
                 Salinity 
                   
               
               
                 Reservoir 
                 at Point 2 
                 Flow (10 −4  m 3 /sec) 
               
            
           
           
               
               
               
               
               
               
            
               
                 (meters) 
                 (ppt) 
                 Point 1 
                 Point 2 
                 Point 3  
                 Point 4 
               
               
                   
               
               
                 0.23 
                 34 
                 1.3 
                 45.5 
                 1.3 
                 44.2 
               
               
                 0.55 
                 34 
                 2.4 
                 84.0 
                 2.4 
                 81.6 
               
               
                   
               
            
           
         
       
     
     The results indicate that the flow rate of the mixed salt-water/fresh-water solution at Point 2 at the outlet end  44  of the up tube  40  far exceeded the flow rate of fresh water at Point 1 and Point 3. Introducing fresh water into the down tube  20  and allowing the salt water to flow into the up tube  40  therefore generated higher flow rates at Point 2, at the top of the up tube  40 . 
     In order to demonstrate that this higher flow rate at Point 4 was not due to transfer of kinetic energy from the fresh water flow coming from the down tube  20 , the following experiment was performed. 
     Example 2 
     Flow Rates Through the Up Tube with Salt Water vs. Fresh Water Introduced into the Down Tube 
     For this experiment, a 6″ turbine roof vent was attached to the outlet end  44  of the up tube  40 . One of the vanes was painted to allow for the counting of rotations. The reservoir was filled with fresh water having a salinity of 300 ppm in one experiment and with salt water having a salinity of 36,000 ppm in a second experiment. The reservoir was placed at a height of 0.55 meters above the water level of the salt water in the pool. The fresh water was then allowed to flow through the down tube  20 , and the rate at which the turbine rotated was determined. Then, salt water from the salt water pool was allowed to flow through the down tube  20 , and the rate at which the turbine rotated was again determined. The results are shown in Table 2 below 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Turbine Speed with Fresh Water vs. Salt Water in Down Tube 
               
            
           
           
               
               
               
            
               
                   
                 Down Tube Water 
                   
               
               
                   
                 Flow 
                 Turbine Speed 
               
               
                   
                 (10 −4  m 3 /sec) 
                 (rpm) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Fresh Water (0.3 ppt) 
                 2.4 
                 5.6 
               
               
                   
                 Salt Water (36 ppt) 
                 2.3 
                 2.3 
               
               
                   
                   
               
            
           
         
       
     
     As illustrated in Table 2, above, the turbine rotated 2.4 times more rapidly when fresh water was introduced into the down tube  20  than when salt water was used. The higher turbine speed when fresh water was introduced into the down tube  20  is a direct indication that the water flow in the up tube  40  was higher when fresh water rather than salt water was introduced into the down tube  20  and that the higher observed water flow rates from the top of the up tube  40  in Example 1 were not due solely to kinetic energy transfer from the fresh water flow out of the down tube  20 . 
     The kinetic energy transferred from the salt water in the down tube  20  to the salt water in the up tube  40  would be at least as great (if not slightly greater due to increased density of salt water) as the kinetic energy transferred from the fresh water in the down tube  20 . The results shown in Table 2 indicate that some, but not all, of the upwelling of water in the up tube  40  is due to kinetic energy transfer from the water introduced into the down tube  20 . 
     Example 3 
     A series of experiments were carried out using the experimental design described above and as illustrated in  FIG. 2 , but with down tubes  20  having different diameters. With each down tube  20 , the flow rates of the fresh water in the down tube  20  were varied to determine the effect of different fresh water flow rates on available power. The salinity at the outlet end  44  of the up tube  40  was measured, and the water flow rates were calculated from the salinity as before. The water flow rates were used to calculate the available power at Point 2, the outlet end  44  of the up tube  40 . The available power was then normalized by dividing the available power by the fresh water flow rate in the down tube  20 . The results are shown in Table 4 below. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Normalized Power Production vs. Diameter of Up Tube 
               
               
                 and Fresh Water Flow Rates 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 Down 
                 Ratio of Up 
                 Power/Fresh 
               
               
                 Salinity 
                 Flow (×0.0001 m 3 ) 
                 Tube 
                 Tube Area to 
                 Water 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 at Point 
                   
                 Point 
                 Point 
                 Area 
                 Down Tube 
                 Flow 
               
               
                 2 (ppt) 
                 Point 1 
                 4 
                 2 
                 (m 2 ) 
                 Area 
                 (Watts/m 3 ) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 31.8 
                 22 
                 259 
                 281 
                 0.000254 
                 69.7 
                 1312 
               
               
                 32.6 
                 18 
                 309 
                 327 
                 0.000071 
                 249 
                 2715 
               
               
                 33.4 
                 5.2 
                 158 
                 163 
                 0.000018 
                 983 
                 1256 
               
               
                 31.4 
                 33 
                 334 
                 367 
                 0.000254 
                 69.7 
                 1877 
               
               
                 32.6 
                 26 
                 446 
                 472 
                 0.000071 
                 249 
                 5664 
               
               
                 33.3 
                 7.6 
                 211 
                 218 
                 0.000018 
                 983 
                 2047 
               
               
                 35.0 
                 5 
                 168 
                 173 
                 0.000010 
                 1770 
                 1559 
               
               
                   
               
            
           
         
       
     
     In all cases, the power per unit volume of fresh water introduced into a down tube  20  of a given diameter increased as the flow rate of fresh water through the down tube  20  increased. Thus, for the down tube  20  with an area of 0.000254 m 2 , the power/m 3  of fresh water flow increased from 1312 watts/m 3  with a fresh water flow rate of 22×10 −4  m 3  to 1877 watts/m 3  with a fresh water flow rate of 33×10 −4  m 3 . The same trend was maintained for the down tubes having areas of 0.000071 and 0.000018 m 2 . Thus, the data illustrates that increasing the fresh water flow rate in a down tube  20  having a given area increased the normalized available power output of the device. 
     Second, although the power per unit volume of fresh water introduced into the down tube  20  increased with increased volume of fresh water introduced into the down tube  20  in all cases, the percent increase in the power with increase in fresh water flow rate was less for the largest down tube  20  (0.000254 m 2  area) than for the other down tubes  20 . When the fresh water flow rate increased from 22×10 −4  m 3 /sec to 33×10 −4  m 3 /sec, or by 50%, with the largest down tube  20 , the power/fresh water flow rate increased from 1312 watts/m 3  to 1877 watts/m 3 , or 40%. By comparison, when the fresh water flow rate for the down tube  20  with an area of 0.000018 m 2 /sec was increased from 5.2 to 7.6×10 −4  m 3 /sec, or 46%, the power/fresh water flow rate increased from 1256 watts/m 3  to 2047 watts/m 3 , or 62%, more than 1.5 times as much as for a comparable percent change in the fresh water flow rate with the larger down tube  20 . 
     Similarly, when the fresh water flow rate for the down tube  20  with an area of 0.000071 m 3  increased from 18 to 26×10 −4  m 3 /sec, or 44%, the power/fresh water flow rate increased from 2715 watts/m 3  to 5664 watts/m 3  or 108%, more than 2.5 times as much as for the largest down tube  20 . The efficiency of power production declined with the largest diameter down tube  20 . 
     These results are shown graphically in  FIG. 3 . The graphs depicted therein appear to show that there is an optimum ratio (about 250:1) of the area of the up tube  40  relative to the area of the down tube  20  that maximizes normalized power production. At ratios higher or lower than about 250 the normalized power per unit volume of fresh water declines. 
     Although a ratio of the area of the up tube  40  relative to the area of the down tube  20  of approximately 250 appears to be optimal, the ratio may range from approximately 5 to 50,000, more preferably from 50 to 2000. 
     The previous examples and discussions illustrate that a suitably constructed upwelling apparatus as illustrated in  FIG. 2  has the potential of generating useful power by mixing aqueous liquids having different osmotic potentials. 
       FIG. 4  is a simple schematic illustration of one possible embodiment of a hydrocratic generator  100  utilizing the principles discussed above and having features and advantages in accordance with the present invention. The device  100  generally comprises a down tube  20 , an up tube  40 , and a power plant generator  60 . The particular device illustrated in  FIG. 4  may be adapted for either large-scale deep water applications or for relatively small-scale or intermediate-scale power generation facilities in shallow coastal waters, as desired. For example, the depth of water illustrated in  FIG. 4  may be 10 to 50 meters or more, with the up tube  40  being 1-5 meters in diameter. 
     In a preferred embodiment, fresh water is introduced into the down tube  20  in order to power the device. The term “fresh” water as used herein is to be interpreted in a broad sense as water having an osmotic potential relative to sea water. Thus, it may be used to describe the input stream a river discharge, a mountain run-off, a treated sewage discharge, a melting iceberg, or even runoff from a city storm drainage system. 
     The fresh-water input stream may be conducted though the down tube  20  by applying pressure at the inlet end  22  of the down tube  20 . The pressure may be provided by a pumping station or with a hydrostatic head pressure resulting from a fluid reservoir at a higher elevation. The pressure applied at the inlet end  22  of the down tube  20  need only be high enough to overcome the hydrostatic head at the outlet end  24  of the down tube  20 . 
     It has been found that, when fresh water is introduced into the down tube  20 , sea water flows into the up tube  40 , causing upwelling in the up tube  40  that can be used to generate power with the power generator  60 . Some of this upwelling effect is due to the increased buoyancy of the mixed water in the up tube  20 , because fresh water has a lower density than sea water. However, far more upwelling of sea water is observed than would be expected from this phenomenon alone. It is believed that the apparatus and the method is able to harness the energy available from the different osmotic potentials of fresh water and sea water. The amount of upwelling and the amount of power that is generated in the device depend in part on the particular dimensions of the up tube  40  and the down tube  20  and the flow rate of fresh water in the down tube  20 . 
     As shown in  FIG. 4 , the down tube  20  has an inlet end  22  and an outlet end  24 . The inlet end  22  is connected to a supply  25  of relatively fresh water. For example, this fresh water supply  25  may comprise a reservoir, pump or other source as desired or expedient. The outlet end  24  of the down tube  20  is open such that the fresh water discharges through the outlet end  24  of the down tube  20  into the up tube  40 . In alternative embodiments the outlet end  24  of the down tube  20  may be connected to an intermediate mixing chamber (not shown) which then discharges into the up tube  40 . 
     Although the down tube  20  may be any of a variety of diameters, one criterion is to choose a diameter for the down tube  20  which minimizes the resistance to fluid flow through the down tube  20 . Resistance to flow through a tube decreases as the diameter of the tube increases. Choosing a large diameter for the down tube  20  therefore minimizes the resistance of the tube for a given flow rate. 
     Another criterion in choosing the diameter of the down tube  20  is to maximize the amount and efficiency of power generated by the power generator  60 . When the diameter of the down tube  20  exceeds a certain value relative to the up tube  40 , it has been discovered that the efficiency of power generation declines as the diameter of the down tube  20  is increased further. There is therefore an optimum in the ratio of the diameter of the down tube  20  relative to the diameter of the up tube  40 , and therefore the ratio of the area of the down tube  20  relative to the area up tube  40 , in order to maximize the efficiency of power generation. When the ratio of the area of the down tube  20  to the up tube  40  increases beyond the optimal value, the increase in efficiency of power generation with increased fresh water flow in the down tube  20  is less than with a down tube  20  having a smaller area relative to the up tube  40  area. Choosing the diameter of the down tube  20  to maximize power production therefore involves tradeoffs to choose the maximum diameter possible without losing power efficiency. 
     In the embodiment of the apparatus shown in  FIG. 4 , the outlet end  24  of the down tube  20  is located inside the up tube  40 . In this embodiment, the outlet end  24  of the down tube  20  is preferably oriented so that the outlet end  24  of the down tube  20  points upward. 
     The up tube  40  has an lower end  42  and an outlet end  44 . In the embodiment of  FIG. 4  both the lower end  42  and the outlet end  44  of the up tube  40  are open. In other embodiments, the lower end  42  of the up tube  40  may contain vanes or other means of directing water flow. Some of these alternative embodiments of the up tube  40  are illustrated in other figures herein. 
     Although the diameters of the lower end  42  and the outlet end  44  of the embodiment of the up tube  40  shown in  FIG. 4  are equal, the lower end  42  and the outlet end  44  of the up tube  40  may have different diameters in other embodiments. For example, the up tube may be positively or negatively tapered to form a nozzle or diffuser. Alternatively, the up tube  40  can have a necked-down portion to form an accelerated flow there-through. 
     In the embodiment of  FIG. 4  the outlet end  44  of the up tube  40  is attached to a flotation system for locating the up tube  40  at a predetermined depth. Other means of locating the up tube  40  at a predetermined depth may also used in place of the flotation system, and the invention is not limited to the embodiment shown in  FIG. 4 . The flotation system shown in  FIG. 4  comprises one or more floats  48  and one or more support cables  50 . The float  48  may be formed of Styrofoam, or it may comprise a plurality of individual air bags, drums, or any other suitable material capable of producing buoyancy. 
     In some embodiments, the lower end  42  of the up tube  40  is attached to mooring cables  52 . The mooring cables  52  extend from the lower end  42  of the up tube  40  to anchors  56  fixed on the sea floor. The mooring cables  52  and the anchors  56  retain the up tube  40  in a predetermined location on the sea floor. The lifting force of the float  48  transmitted through support cables  50  retains the up tube  40  at a desired predetermined vertical orientation. 
     In the embodiment shown in  FIG. 4 , the down tube  20  is also attached to mooring cables  52  which extend to anchors  56  on the ocean floor. The mooring cables  52  and anchors  56  hold the down tube  20  in place. The down tube  20  is arranged so that it discharges the fresh water into the up tube  40 . 
     Just as choosing an optimal diameter for the down tube  20  involves tradeoffs, choosing the diameter of the up tube  40  also involves optimization. Increasing the diameter of the up tube  40  increases the amount of upwelling in the up tube  40  and therefore increases power production. However, increasing the diameter of the up tube  40  increases both the size and the cost of the apparatus. Further, increasing the area of the up tube  40  allows the use of a down tube  20  with a greater area without losing efficiency in generating power. The ratio of the area of the down tube  20  to the area of the up tube  40  is therefore the parameter which is to be optimized rather than the diameter of either the up tube  40  or the down tube  20  alone The optimal diameters for the up tube  40  and the down tube  20  are interdependent on one another, because the ratio of the areas of the two tubes is a more important parameter in optimizing power production than the area, and therefore the diameter, or either the up tube  40  or the down tube  20  alone. 
     Advantageously the down tube  20  and the up tube  40  are not subjected to excessively high pressures. In the embodiment shown in  FIG. 4 , the up tube  40  contains the sea water entering from the lower end  42  of the up tube  40  and the fresh water coming out of the outlet end  24  of the down tube  20 . Because the up tube  40  is operated at low pressures, the up tube  40  can be constructed of relatively inexpensive and lightweight materials such as plastic, PVC, lightweight concrete, and the like. 
     Although the down tube  20  is subjected to higher pressures than the up tube  40 , the pressures in the down tube  20  are typically small. Thus, inexpensive materials can therefore generally be used for both the up tube  40  and the down tube  20 . Suitable materials for constructing the down tube  20  and the up tube  40  include, but are not limited to, polyvinyl chloride (PVC), fiberglass, polyethylene (PE), polypropylene (PP), concrete, gunite, and the like. Alternatively, other materials such as stainless steel or titanium may also be used. Because the up tube  20  and the down tube  40  are generally exposed to water of relatively high salinity, it is preferable to form the down tube  20  and the up tube  40  from materials which are resistant to corrosion from salt water. Although the materials listed above are, in general, resistant to corrosion, some alloys of stainless steel are not suitable for extended use in salt water. If stainless steel is chosen as a material of construction, it is preferable to select an alloy of stainless steel which is resistant to corrosion by salt water. 
     The outlet end  44  of the up tube  40  may extend to or above the surface of the sea or may be located at any depth beneath the surface of the sea. In one embodiment, the outlet end  44  of the up tube  40  is located in the photic zone so as to bring nutrient-rich deep-sea water to the photic zone to enhance growth of the organisms in the photic zone through mariculture. 
     The length of the up tube  40  may vary, depending on a variety of factors. The length of the up tube is preferably sufficient to allow complete mixing of the fresh water with the salt water, but not so long as to cause unnecessary drag on the water flow. The optimal length will be determined as that which allows maximum output flow rate and power production for a given range of input fresh-water flow rates. The length of the up tube  40  may also be chosen based on a desire to facilitate mariculture, the promotion of growth of organisms in the sea by transfer of nutrients from nutrient-rich depths to the nutrient-poor water at lesser depths. If mariculture is practiced, the lower end  42  of the up tube  40  is preferably located at a depth of the sea where large concentrations of nutrients are available, and the outlet end  44  of the up tube  40  is preferably located in the photic zone. In this embodiment, the up tube  40  carries nutrient-rich water from the depth of the lower end  42  of the up tube  40  to the outlet end  44  of the up tube  40  in the photic zone, where few nutrients are available, thereby enhancing growth of the organisms in the photic zone. The length of the down tube  20  is relatively unimportant, provided that it is long enough to deliver the fresh water into the up tube. 
     The power generator  60  generates electricity from the water flow inside the up tube  40 .  FIG. 4  shows one simplified form of a power generator  60  suitable for use with the present invention. The power generator  60  comprises one or more turbines or propellers  62  attached to a shaft  64 . In a preferred embodiment, there are a plurality of propellers  62  attached to the shaft  64 . The shaft  64  is connected to an electrical generator  66 . When water upwells in the up tube  40 , the upwelling water turns the propellers  62 , which in turn rotate the shaft  64 . The rotating shaft  64  drives the electrical generator  66 , thereby generating power. 
     Preferably, one or more shaft supports  68  are provided to support the shaft  64  to minimize wobbling of the shaft  64  while the upwelling water turns the one or more propellers  62  attached to the shaft  64 . In a preferred embodiment, a plurality of shaft supports  68  engage the shaft  64  to support the shaft  64  to minimize wobbling. In the embodiment shown in  FIG. 4 , three shaft supports  68  are present to support the shaft  64 , a lower shaft support  68 , a middle shaft support  68 , and an upper shaft support  68 . Further details on the shaft supports  68  are given in  FIG. 7C , described later. 
     The propellers  62  on the shaft  64  may be inside the up tube  40 , above the outlet end  44  of the up tube  40 , or both inside the up tube  40  and above the outlet end  44  of the up tube  40 . The propellers  62  on the shaft  64  may be located above the middle shaft support  68 , below the middle shaft support  68 , or both above and below the middle shaft support  68 . In the embodiment of  FIG. 4 , the propellers  62  are located inside the up tube  40  below the middle shaft support  68 . Similarly, the electrical generator  66  may be conveniently located above or below the surface of the water in which the up tube  40  is located. In the embodiment shown in  FIG. 4 , the electrical generator  66  is located above the surface of the water in order to minimize maintenance expense. 
       FIG. 5  shows an alternative embodiment of a power generator  60 . In this case, the power generator  60  comprises propellers  62  attached to the shaft  64  both above and below the middle shaft support  68 . The shaft  64  is attached to the electrical generator  66 , which generates electrical power when the shaft  64  rotates due to the water flow in the up tube  40 . Again, the electrical generator  66  of  FIG. 5  is located above the surface of the water. In alternative embodiments, the electrical generator  66  may be located below the surface of the water, if desired. 
       FIG. 6  shows a further alternative embodiment of a power generator  60  in which one or more spiral fans  70  are mounted on the shaft  64 . Shaft supports  68  may optionally be provided to minimize wobbling of the shaft  64 . The one or more spiral fans  70  may be attached to the shaft  64  above the middle shaft support  68 , below the middle shaft support  68 , or both above and below the middle shaft support  68 . One or more spiral fans  70  may be mounted on the shaft  64  on the outlet end  44  of the up tube  40 . In an alternative embodiment, one or more spiral fans  70  may be mounted both inside the up tube  40  and on the outlet end  44  of the up tube  40 . In the embodiment of  FIG. 6 , the spiral fan  70  is attached to the outlet end  44  of the up tube  40 . 
     The spiral fan  70  comprises a plurality of spiral vanes  72 . The water flow up the up tube  40  contacts the plurality of spiral vanes  72 , turning the one or more spiral fans  70  mounted on the shaft  64 . Turning the one or more spiral fans  70  rotates the shaft  64 . The rotating shaft  64  drives the electrical generator  66 , generating electrical power. Again, the electrical generator  66  may be conveniently located above or below the surface of the water, as desired. 
     In the embodiment of the power generator  60  shown in  FIG. 6 , both propellers  62  and one spiral fan  70  are mounted on the shaft  64 . The propellers  62  and spiral fans  70  may be mounted on the shaft  64  in any order, above, below, or both above and below the middle shaft support  68 . The propellers  62  and spiral fans  70  may also be mounted on the shaft  64  inside the up tube  40  and/or above the outlet end  44  of the up tube  40 . In  FIG. 6 , propellers  62  are mounted on the shaft  64  inside the up tube  40  below the middle shaft support  68 , and the single spiral fan  70  is mounted on the outlet end  44  of the up tube  40 . The electrical generator  66  is located above the water. 
       FIG. 7A  shows a further alternative embodiment of the up tube  40  in which the lower end  42  of the up tube  40  is closed. The down tube  20  passes through the closed lower end  42  of the up tube  40 . Although  FIG. 7A  shows that the down tube  20  is attached to one or more mooring cables  52  which are attached to anchors  56  on the ocean floor, the down tube  20  may also be supported by the closed lower end  42  of the up tube  40 . The closed lower end  42  of the up tube  40  of  FIG. 7A  helps to keep the down tube  20  in position without the need for mooring cables  52  and anchors  56 . 
     The up tube  40  of the embodiment of  FIG. 7A  comprises a plurality of slots  76 , as shown in  FIG. 7B . The plurality of slots  76  are open to the surrounding sea and allow the sea water to enter the up tube  40 . One or more shaft supports  68  are attached to the up tube  40 ; One possible embodiment of a suitable shaft support  68  is shown in  FIG. 7C . The shaft support  68  comprises one or more hydrodynamic cross members  78  and a bearing  80 . The cross members  78  are attached to the up tube  40  at a first end and to the bearing  80  at a second end, thereby suspending the bearing  80  inside the up tube  40 . The bearing  80  can have a variety of designs such as ball bearings, compression bearings, and the like. The cross members  78  are preferably hydro-dynamically shaped so as to not slow down water flow in the up tube  40 . The shaft support  68  supports the shaft  64 , minimizing the wobbling of the shaft  64  when the shaft  64  rotates. 
     The power generator  60  of the embodiment shown in  FIG. 7A  comprises a vane drum  90  inside the up tube  40 . The vane drum  90  comprises a plurality of rings  92  connected by a plurality of curved vanes  94 .  FIG. 7D  shows a sectional view of the vane drum  90 . Each curved vane  94  is attached by a first edge  96  to each of the plurality of rings  92 . The curved vanes  94  are attached to the plurality of rings  92  in a manner so that the curved vanes  94  form a helical curve when viewed from the side, as shown in  FIG. 7A . The helical curved shape of the curved vanes  94  improve the efficiency of energy transfer from the water flow through the slots  76  on the up tube  40  compared to the efficiency of curved vanes  94  which are not oriented with a helical curve.  FIG. 7D  shows the curved vanes  94  attached to the ring  92  from above as illustrated in  FIG. 7A .  FIG. 7D  also shows the preferred curved surface of the curved vanes  94  as well as the helical orientation of the curved vanes  94  as viewed from above. 
     In one preferred embodiment, the vane drum  90  is attached to the shaft  64 . When the sea water is drawn into the up tube  40  through the slots  76 , the incoming water contacts the curved vanes  94 , rotating the vane drum  90 , which in turn rotates the shaft  64 . The rotating shaft  64  turns the electrical generator  66 , generating power from the upwelling water in the up tube  40 . 
       FIG. 8A  illustrates a further alternative embodiment of the power generator  60  comprising two vane drums  90 , a first vane drum  90  below the middle shaft support  68  and a second vane drum  90  above the middle shaft support  68 . In a preferred embodiment, both the first vane drum  90  and the second vane drum  90  are attached to the shaft  64  so that the shaft  64  rotates when the vane drums  90  rotate due to the flow of water through the slots  76  into the up tube  40 . The rotating shaft  64  rotates the shaft of the electrical generator  66 , generating electrical power. 
     In the embodiment of the up tube  40  shown in  FIG. 8B , there are preferably two sets of slots  76  in the up tube  40  and two vane drums  90 . In another embodiment, there are two vane drums  90  as in the embodiment shown in  FIG. 8A , but the up tube  40  comprises only a single set of slots  76  in the up tube  40 , as in the embodiment of the up tube  40  shown in  FIG. 7B . 
       FIG. 9A  shows an alternative embodiment of the down tube  20  in which a plurality of holes  110  are present in the side of the down tube  20 .  FIG. 9B  shows a view of the outlet end  24  of the down tube  20  of  FIG. 9A . The outlet end  24  of the down tube  20  of  FIG. 9A  is sealed except for a single hole  110 . In alternative embodiments, a plurality of holes  110  may be provided in the outlet end  24  of the down tube  20 . The fresh water flowing through the down tube  20  of  FIG. 9A  flows out of the plurality of holes  110  and into the up tube  40 . Although the embodiment of the apparatus shown in  FIG. 9A  shows the alternative down tube  20  with the embodiment of the up tube  40  of  FIGS. 4-6  with an open lower end  42 , the down tube  20  of  FIG. 9A  may also be used with the embodiment of the up tube  40  such as shown in  FIG. 7A  or  8 A with a closed lower end  42 . 
       FIGS. 10A and 10B  show another embodiment of the down tube  20  in which the down tube  20  separates into a plurality of secondary down tubes  120  In the embodiment shown in  FIG. 1A , there are a plurality of holes  110  in the secondary down tubes  120 , similar to the embodiment of the down tube  20  shown in  FIG. 9A .  FIG. 10B  shows a sectional view of the down tube  20  of the embodiment of  FIG. 10A  from below. In the embodiment shown in  FIG. 10B  the outlet end  24  of each of the five secondary down tubes  120  is closed except for a single hole  110 . In the embodiment of the down tube  20  of  FIGS. 10A and 10B , the fresh water that is introduced into the down tube  20  exits the holes  110  to enter the up tube  40 . 
     In other embodiments the down tube  20  may separate into a plurality of secondary down tubes  120 , as in the embodiment of the down tube  20  of  FIG. 10A , but there are no holes  110  in the secondary down tubes  120 , and the outlet ends  24  of the secondary down tubes  120  are open. In this embodiment of the down tube  20  (not shown), the fresh water which is introduced into the down tube  20  exits the open outlet ends  24  of the secondary down tubes  120  to enter the up tube  40 . 
       FIG. 11  shows an alternative embodiment of the down tube  20  in which the down tube separates into a plurality of secondary down tubes  120 . In the embodiment shown in  FIG. 11 , the down tube  20  separates into a plurality of secondary down tubes  120  outside of the up tube  40 . In the embodiment shown in  FIG. 11 , there are no holes in the secondary down tubes  120 , as in the embodiments shown in  FIGS. 9A and 10A . In other embodiments there are a plurality of holes  110  in the secondary down tubes  120 . 
     Although the embodiment of the apparatus shown in  FIG. 11  shows the alternative down tube  20  with the embodiment of the up tube  40  of  FIGS. 4-6  with an open lower end  42 , the alternative down tube  20  of  FIG. 11  may also be used with the embodiment of the up tube  40  such as shown in  FIG. 7A  or  8 A with a closed lower end  42 . 
       FIG. 12  shows another embodiment of the down tube  20  in which the down tube  20  terminates in a hub  122 . The hub  122  forms a cap on the down tube  20  and rotates freely on the down tube  20 . A plurality of spoke outlets  124  are fluidly connected to the hub  122 . The plurality of spoke outlets  124  emerge at approximately a right angle from the hub  124  and then bend at a second angle before terminating in a spoke discharge  126 . The spoke discharge  126  may have an open end or a partially closed end where the water from the down tube  20  discharges. The embodiment of the down tube  20  shown in  FIG. 12  is similar to a rotating lawn sprinkler. The hub  122  is attached to the shaft  64 , which is in turn connected with the electrical generator  66 . In the embodiment shown in  FIG. 12 , there is no up tube  40 . 
     When fresh water flows through the down tube  20  and is discharged out of the spoke outlets  124 , the hub  122 , shaft  64 , and electrical generator  66  rotate, generating electrical power. In the embodiment shown in  FIG. 12 , the energy generated by the electrical generator  66  comes almost exclusively from the kinetic energy from the water emerging from the plurality of spoke discharges  126 , because there is no up tube  40  or means of generating power from hydrocratic energy generated from the mixing of fresh water from the down tube  20  with water of high salinity. 
       FIG. 13  shows another embodiment of the down tube  20  similar to the embodiment of  FIG. 12 , with a hub  122 , a plurality of spoke outlets  124 , and a plurality of spoke discharges  126  at the ends of the spoke outlets  124 . The embodiment of  FIG. 13  differs from the embodiment of  FIG. 12  in that the spoke discharges  126  discharge the fresh water from the down tube  20  into an up tube  40  with an open lower end  42  and a plurality of propellers  62  attached to the shaft  64 . The fresh water which exits the spoke discharges  126  into the up tube  40  causes upwelling in the up tube  40 , rotating the propellers, which in turn drive the shaft  64 . The shaft  64  drives a electrical generator  66  (not shown), generating electrical power. 
     In the embodiment of the apparatus shown in  FIG. 13 , the shaft  64  is rotated both by the discharge of water from the spoke discharges  126  rotating the hub  122  and by the upwelling in the up tube  40  turning the propellers  62 , which in turn rotate the shaft  64 . The energy generated in the embodiment of the apparatus shown in  FIG. 13  is therefore a combination of kinetic energy from the rotation of the hub  122 , shaft  64 , and electrical generator (not shown) from the fresh water ejected from the spoke discharges  126  and from hydrocratic energy generated from the upwelling in the up tube  40  from the mixing of fresh water from the spoke discharges  126  mixing with the water of high salinity entering the up tube  40  from the lower end  42 . 
       FIG. 14  illustrates another embodiment of the up tube  40  in which there are a plurality of nested up tubes  40  having increasing diameters. The lower end  42  of each of the plurality of nested up tubes  40  is open. Fresh water is introduced into the down tube  20  causing upwelling in the plurality of up tubes  40  when the water of high salinity enters the open lower ends  42  of the nested up tubes  40 . 
     Any of the embodiments of power generators  60  can be combined with the embodiment of the nested up tubes  40  of  FIG. 14 . For example, in one embodiment, the propellers  62  of  FIGS. 4 and 5  may be used as a power generator  60  in combination with the nested up tubes  40  of  FIG. 14 . In another embodiment, the power generator  60  may comprise one or more spiral fans  70 , as shown in  FIG. 6 . 
       FIG. 15  shows another embodiment of the up tube  40  and power generator  60 . In the embodiment of  FIG. 15 , a plurality of turbines  130  are mounted on a shaft  64  inter-spaced between a plurality of stators  132 . The stators  132  direct the water flow into the turbine blades of the turbines  130  to increase the efficiency thereof. The shaft  64  is connected to an electrical generator  66  (not shown). When water upwells in the up tube  40 , the upwelling water turns the turbines  130 , which in turn rotate the shaft  64  and the electrical generator  66 , generating power. 
     In the embodiment shown in  FIG. 15 , the portion of the up tube  40  surrounding the turbines  130  and stators  132  comprises a nozzle  134  and an expander  136 . The nozzle  134  reduces the diameter of the up tube  40  in the portion of the up tube  40  around the turbines  130  and stators  132  from the diameter of the remainder of the up tube  40 . By reducing the diameter of the up tube  40  with the nozzle  134  in the portion of the up tube  40  surrounding the turbines  130 , the upwelling water is forced into a smaller area and is accelerated to a higher velocity water flow that can be harnessed more efficiently by the turbines  130 . Nozzles  134  and stators  132  can also be used with other embodiments of the power generator  60  illustrated herein. 
       FIG. 16  is a schematic illustration of a possible large-scale commercial embodiment of a hydrocratic generator having features and advantages of the present invention. While a particular scale is not illustrated, those skilled in the art will recognize that the device  200  is advantageously suited for large-scale deep-water use 100-500 meters or more beneath sea level. The up tube  240  extends upward and terminates at any convenient point beneath sea level. The diameter of the up tube may be 3-20 meters or more, depending upon the desired capacity of the hydrocratic generator  200 . This particular design is preferably adapted to minimize environmental impact and, therefore, does not result in upwelling of nutrient rich water from the ocean depths. 
     Sea water is admitted into the device from an elevated inlet tube  215  through a filter screen or grate  245 . The filter removes sea life and/or other unwanted objects or debris that could otherwise adversely impact the operation of generator  200  or result in injury to local sea life population. If desired, the inlet tube  215  may be insulated in order to minimize heat loss of the siphoned-off surface waters to colder water at or near full ocean depth. Advantageously, this ensures that the temperature and, therefore, the density of the sea water drawn into the generator  200  is not too cold and dense to prevent or inhibit upwelling in the up tube  240 . 
     The sea water is passed through a hydraulic turbine power plant  260  of the type used to generate hydraulic power at a typical hydro-electric facility. The turbine and generator assembly is illustrated in more detail in the cutaway view of  FIG. 16 . Water enters the turbine  261  through a series of louvers  262 , called wicket gates, which are arranged in a ring around the turbine inlet. The amount of water entering the turbine  261  can be regulated by opening or closing the wicket gates  262  as required. This allows the operators to keep the turbine turning at a constant speed even under widely varying electrical loads and/or hydraulic flow rates. Maintaining precise speed is desirable since it is the rate of rotation which determines the frequency of the electricity produced. 
     As illustrated in  FIG. 16 , the turbine is coupled to an electric generator  266  by a long shaft  264 . The generator  266  comprises a large, spinning “rotor”  267  and a stationary “stator”  268 . The outer ring of the rotor  267  is made up of a series of copper wound iron cells or “poles” each of which acts as an electromagnet. The stator  268  is similarly comprised of a series of vertically oriented copper coils disposed in the slots of an iron core. As the rotor  267  spins, its magnetic field induces a current in the stator&#39;s windings thereby generating alternating current (AC) electricity. 
     Referring again to  FIG. 16 , the sea water is discharged from the turbine into the up tube  240 . Fresh water is introduced into the base of the up tube  240  by down tube  220 . The mixing of fresh water into saline sea water releases the hydrocratic or osmotic energy potential of the fresh water in accordance with the principles discussed above, resulting in a concomitant pressure drop (up to 190 meters of head) across the hydraulic turbine  260 . This pressure drop in conjunction with the induced water flow upwelling through the up tube  240  allows for generation of significant hydropower for commercial power production applications without adversely affecting surrounding marine culture. 
     With reference to  FIG. 18  of the drawings, this embodiment shows an up tube  40  having an open lower end  42  and an open outlet end  44 . A down tube  20  is provided which enters the up tube  40  through the lower end  42 , and extends to a point approximately midway along the length of the up tube, where it is sealed by a cap  302 . A shaft  64  extends upwardly from the cap  302 , extending to a generator, not shown in  FIG. 18 , but substantially similar to generators shown in some of the Figures described above. 
     Although in the embodiment shown in  FIG. 18 , the down tube  20  is shown as extending to a point approximately midway up the length of the up tube  40 , this construction may, in practice, vary widely according to the conditions, length of the up tube  40 , and other apparatus parameters. Thus, the down tube  20  may extend only a short distance into the up tube  40 , or it may extend well beyond the midpoint thereof, to a selected height. 
     The down tube  20  comprises an outside portion  304 , located outside of the up tube  40 , and an inside portion  306 , located within the up tube  40 . The outside portion  304  and inside portion  306  of the down tube  20  are connected to each other by a rotational connector  308 , which, in the embodiment shown in  FIG. 18  is at the level of the open lower end  42 . However, this rotational connector  308  could be configured on the down tube  20  at any appropriate vertical position of the down tube  20 . 
     The rotational connector  308  permits rotation of the inside portion  306  relative to the outside portion  304 , as will be described. 
     The inside portion  306  has a plurality of radial apertures  310 , which may be randomly disposed on the inside portion  306 , or specifically located, such as beneath a turbine  62 , according to the selected configuration of the generator. Fresh water entering the down tube  20  from a supply source or reservoir passes through the rotational connector  308 , and into the inside portion  306 , where it must exit through one of the radial apertures. The cap  302  mounted at the top end of the inside portion  306  prevents any water or liquid from the down tube  20  from exiting the inside portion  306 , except through the radial apertures  310 . 
     The inside portion  306  and shaft  64  are secured appropriately in position by shaft supports  68  to prevent wobbling or axial displacement thereof, as has already been described above in other embodiments. 
     In operation, fresh water exiting the down pipe  20  through the radial apertures  310  is mixed with water of higher salinity entering the lower end  42  of the upper tube  40 . The energy produced by the mixing of the water of higher salinity and lower salinity drives turbine  62 , which in turn rotates the inside portion  306 , the cap  302 , and the shaft  64 . This embodiment permits accurate selection of apertures  310  for releasing of the fresh water into the up tube  40 , in a manner that is fixed with respect to the turbines  62 . Since the radial apertures  310  and turbines  62  are both rotating, the precise location of mixing, and the optimal effect thereof of driving the turbine  62 , can be exploited to improve the efficiency and hence the energy produced by the apparatus of the invention. This is achieved by the use of the rotational connector  308  which allows relative rotation of the inside portion  306 , but ensures no leakage or fresh water escape from the down tube  20  at the position of the rotational connector  308 . 
       FIG. 19  shows a variation of the apparatus shown in  FIG. 18 , including the up tube  40 , the down tube  20  having an outside portion  304 , and an inside portion  306 , the outside and inside portions  304  and  306  respectively being connected by the rotational connector  308 . A cap  302  is provided at the top end of the inside portion  306 , and a series of turbines  62  are mounted on the inside portion  306 , which has a plurality of selectively placed radial apertures  310 . The apparatus in  FIG. 19  differs from the embodiment shown in  FIG. 18  by the existence of a closure piece  320  over the lower end  42  of the up tube  40 . Since the closure piece  320  prevents sea water from entering the lower end  42  of the up tube  40 , a plurality of holes  322  are provided at locations in the wall of the up tube  40 , as shown in  FIG. 19B , through which the sea water is introduced to the interior of the up tube  40 . One advantage of the embodiment shown in  FIGS. 19A and 19B  is that the sea water can be introduced at the most efficient point, thereby facilitating control of the precise points or areas at which the sea water as well as the fresh water are first introduced and allowed to mix. This factor, coupled with the orientation of turbines  62  on the inside portion  306 , can be used to streamline the efficiency of the apparatus. As was the case with respect to  FIG. 18 , the fresh water is only allowed to exit through the radial apertures between the rotational connector  308  and the cap  302 , at a position, flow-rate and orientation which can be controlled and manipulated to advantage. 
     In  FIG. 20  of the drawings, a further embodiment showing a variation of those illustrated in  FIGS. 18 and 19  of the drawings is illustrated. In this embodiment, an up tube  40  is provided, as well as a down tube  20  including an outside portion  304 , an inside portion  306  having a plurality of radial apertures  310 , and a cap  302 . At the lower end  42 , a closure piece  320  is provided. In the embodiment shown in  FIG. 20 , the rotational device  308  is positioned outside of the up tube  40  and closure piece  320  so as to permit rotation of both the inside portion  306  of the down tube  40 , and the up tube  20 , in response to energy production which causes rotation of the turbine  62 . Thus, rotation about the connector  308  as a result of forces on the turbines  62  thereby rotates the closure piece  320 , up tube  40  and the inside portion  306  of the down tube  20 . 
     As was the case in the embodiment shown in  FIGS. 19A and 19B , sea water will enter the up tube  40 , not through the lower end  42 , but through a series of holes  322  of the type shown in  FIG. 19B . Alternatively, instead of having a plurality of holes  322 , one or more slits may be provided in the wall of the up tube  40 , such as those shown in  FIG. 7B  or  8 B of the drawings. 
     The embodiment of  FIG. 20  is yet another variation by means of which the precise location of entry of the fresh water and sea water respectively into the up tube  40  can be controlled and exploited to derive maximum energy and power following hydrocrasis and the energy released thereby. 
       FIG. 21  of the drawings shows a variation of the hydrocratic generator of the invention which uses neither vanes nor turbines on the shaft  64 , but rather a helical screw  330  mounted on the shaft, and which is caused to rotate in response to the energy released by mixing of the water with different salinities. Such forces acting on the helical screw  330  rotate the shaft  64 , which in turn transmits rotational forces to the generator for use as described above. 
       FIG. 22A  of the drawings shows an alternative embodiment for delivering fresh water from the down tube  20  to a precise location with respect to the fan blades. As shown in  FIG. 22A , an inside portion  306  of the down tube  20  has a plurality of fan blades  62 , also referred to as turbines, mounted thereon Instead of exiting the inside portion  306  through a plurality of apertures, the fresh water in the inside portion  306  is fed through a fan tube  336  which is mounted on the underside  338  of the fan blade  62 . Towards the outer extremity  340  of the fan blade  62 , the fan tube  336  includes a U-shaped section  342 , terminating in an outlet  344 . Thus, fresh water enters through the inside portion  306 , flows along the fan tube  336 , into the U-shaped section  342 , and exits through outlet  344 . In the embodiment shown in  FIGS. 22A and 22B , the fresh water thus flows from the interior pipe through a series of smaller pipes located under the fan blades  62  (or helical screw, if this embodiment is used), to the outer edge of the fan blades  62 . The direction of flow is reversed so the fresh water exits in a flow direction which is towards the center of the up tube  40 . 
     The embodiment shown in  FIGS. 22A and 22B  allows the apparatus to take advantage, once more, of controlling the exit areas for the saline and fresh water, thereby pinpointing the reaction location for maximum energy production and/or use of such energy in a manner which rotates the fan blades optimally. As with the other embodiments, the inside portion  306  of the down tube  20  is attached to a rotating shaft, which in turn attaches to a generator or power mechanism which uses or stores the energy so produced. 
     Reference is now made to  FIG. 23  of the drawings showing yet a further schematic representation of an embodiment of the invention.  FIG. 23  shows some of the basic components only, and is mainly intended to illustrate the various locations and multiple turbines which may be used with the system. As such, only the basic apparatus is shown, but it may of course incorporate features and components as described in any one or more of the previous embodiments This also applies to all embodiments described below. 
     In  FIG. 23 , the up tube  400  is positioned within a body of water  402 , the up tube  400  having an upper end  404  and a lower end  406 . Typically, the body of water  402  is the ocean, and water of relatively high humidity will enter the up-tube  400  through the lower end  406 , and move towards the upper end  404 . However, other models and variations are of course within the scope of this invention. 
     A down tube  408  is provided, and extends from a reservoir  410  at one end, with the other end  412  of the down pipe/tube discharging into the up tube  400  at or near the lower end  406 . As has been described above, water from the reservoir  410  will have relatively low salinity, and mix with the relatively high salinity water entering through the lower end  406  of the up tube  400 . As has already been described, the mixing of the relatively low and relatively high salinity water produces energy, and power generators are positioned to capture this energy. In  FIG. 23 , a first turbine  414  is provided near the upper end  404  of the up tube  400  to capture the energy and therefore generate power. It is to be noted that a second turbine  416  is positioned near the reservoir  410 , along the down tube  408 . Note that the second turbine  416  is shown near the reservoir  410  in  FIG. 23 , but it may be placed at other locations along the down tube  408 . The flow of water through the down tube  408  drives the second turbine  412  and energy derived therefrom is used to produce power. 
     Additionally, a third turbine  418  is provided near the lower end  406  of the up tube  400 . The third turbine  418  is positioned so as to take advantage of flow of water from the body of water  402  into the up tube  400 , and capture and produce power. 
     Thus, it will be seen from  FIG. 23  that various turbines may be placed around the system to take advantage of water flow not only as the result of the mixing of the relatively low and relatively high salinity water, but also to place turbines in other positions where they may be driven by the flow of water, either through the down tube  408 , or upon entering or being driven through the up tube  400 . Note that in  FIG. 23 , the second turbine  416  is shown outside of the body of water  402 , although of course it can be placed at a lower level along the down tube  408 , and may additionally or alternatively be located in the body of water  402 . 
     In  FIG. 24   a  of the drawings, another mechanism whereby water may be introduced from a source of low salinity into the up tube is illustrated. Thus, in very schematic form,  FIG. 24   a  shows an up tube  430 , positioned substantially vertically, with an upper end  432  and a lower end  434 , as has already been described. Water of relatively high salinity enters the lower end  434 , passes into the up tube  430 , and eventually is discharged through the upper end  432 . While in the up tube  432 , the relatively high salinity water is mixed with a relatively low salinity water delivered by a down pipe or tube  436 . The down pipe  436  is connected to a source of relatively low salinity water, and extends to the lower end  434  of the up tube  430 , and has a discharge opening  438  through which the relatively low salinity water is introduced into the up tube  430 . 
     Further, the down pipe  436  has attached thereto a secondary down pipe  440  which leads off the down pipe  436  and is spirally or helically wrapped around the up tube  430 . The secondary down pipe  440  has a plurality of holes  442  arranged along its length, and these holes register with corresponding holes in the up tube to permit water to pass from the secondary down pipe  440 , through the up tube  430  and into the interior thereof.  FIG. 24   b  shows a cross-section of the secondary pipe  440 , wrapped around the up-tube  430 , with the holes  442 . In this embodiment, therefore, the relatively low salinity water, or fresh water, is introduced into the up-tube  430  not only at the low end  434  thereof, but also along multiple points of entry corresponding to the holes  442 . This may facilitate mixing in a more thorough manner and may therefore also enhance the ability to capture additional power as a result thereof. 
     Reference is now made to  FIG. 25  which shows a further embodiment of the invention in schematic form. Once more, there is provided an up tube  450 , and a down pipe  452 . The up tube  450  has a lower end  454  and an upper end  456 . The up tube  450  is located in a body of water, such as the ocean, and relatively high salinity water enters through the lower end  454 , passes through the up tube  450  and is discharged through the upper end  456 . 
     The down pipe  452  conveys water from a fresh water source, or water of relatively low salinity, or waste water which has been, or is to be treated, therethrough, and comprises the discharge opening  458  near the low end  454  of the up tube  450 . Additionally, a sleeve  460  is formed around the up tube  450 , and is supplied with water from the down pipe  452  through a branch pipe  462 . The branch pipe  462  conveys water from the down pipe  452  to the inside of the sleeve  460 , and holes in the up tube  450  allow water introduced into the sleeve  460  to enter the up tube  450  for mixing with the relatively high salinity water entering through the lower end  454 . It will be appreciated that this embodiment shows a variation of that shown in  FIG. 24   a , providing additional points of entry of fresh water, or relatively low salinity water, to enhance mixing over a wider volume. 
       FIG. 26  illustrates a further embodiment of the invention in schematic form, and shows an up tube  470  having an upper end  472  and a lower end  474 . A down pipe  476  conveys fluid of relatively low salinity into the lower end  474  of the up tube  470 . Additionally, a first branch pipe  478  and a second branch pipe  480  branch from the down pipe  476 , and have discharge outlets  482  and  484  respectively within the up tube  470 . The down pipe  476  itself continues and has a discharge outlet  486  near the lower end  474  of the up tube  470 .  FIG. 26  illustrates an embodiment where fluid is delivered to the up tube  470  at several locations, once more, to facilitate mixing and to enhance the ability to capture additional power from the mixing process. 
     In  FIG. 27 , an up tube  490  has an upper end  492  and a lower end  494 . A down tube  496  extends from a source of relatively low salinity water, and has a discharge outlet  498  near the lower end  494  of the up tube  40 . The down tube  496  also has a first branch pipe  497  and s second branch pipe  500  which respectively connect to a ring  502  and a ring  504  which circumnavigates the up tube  490  at various locations along its length. The first and second branch pipes  497  and  500  respectively deliver water or fluid to the rings  502  and  504  respectively, and the rings  502  and  504  have multiple holes therein through which water can pass to enter the up tube  490 .  FIG. 27   b  is cross-section through the up tube at the location of a ring, providing a further detail as to the configuration. Once more, this particular form of the invention allows a more diverse delivery of low salinity fluid into the up tube  490  to provide a more broad-based and effective mixing mechanism which in turn facilitates capturing of additional power from the mixing process. 
     Reference is now made to  FIG. 28  of the drawings showing in schematic form yet another embodiment of the invention. In this particular embodiment, the hydrocratic generator of the invention is intended for use in conjunction with, for example, a sanitation district which may optionally incorporate a desalination plant. In  FIG. 28 , there is shown a body of water  520  having a water surface  522 . Within the body of water  520 , there is located a vertical or up tube  524  having an open upper end  526  and an open lower end  528 . The up tube  524  is preferably located adjacent a land mass  530 , which has built thereon various structures, including a sanitation district plant  532  and a desalination plant  534 . These two plants provide, respectively, fluid of relatively high salinity, and fluid of relatively low salinity, so that the mixing thereof within the vertical tube  524 , along the lines described in the several embodiments above, produce energy which can be captured by a power generator for storage and subsequent use. 
     A sewer line  538  extends from the sanitation district plant  532 , and has a discharge outlet  540  at or near the lower end  528  of the vertical tube  524 . There is also a pipe or brine line  542  for transmitting fluid from the desalination plant to the inside of the up tube  524 . Within the tube, the discharge contents from the sewer line  538 , and the brine line  542 , each of which has different relative salinity levels, results in a mixture which produces energy. A power generator, which may be in the form of a turbine, is not shown in  FIG. 28  of the drawings, but may be positioned at or near the upper end  526  of the vertical tube  524 , so as to capture the energy of the mixture. Additionally, turbines or power generators may be placed at other locations, such as in either one of the sewer line  538  or brine line  542 . 
     As an alternative, the brine line  542  and sewer line  538  may be juxtaposed so that each discharges into the vertical tube in the reverse form as shown in  FIG. 28 . The lower end  528  of the vertical tube  524  is open, so that water from the body of water  520 , such as an ocean, also enters the vertical tube. 
     In  FIG. 28 , the turbine or power generator may be above the upper end  526 , outside of the vertical or up tube  524 , or it may be at the level of the upper end  526  or even below it within the tube. Further, there may be more than one turbine or power generators arranged relative to the tube  524  so as to maximize the capture power in the most efficient manner to optimize energy produced by the mixing of the various fluids. 
     It should be noted that in all of the embodiments above, the relatively low salinity fluids and the relatively high salinity fluids may comprise fresh water and ocean water respectively, but the invention is certainly not limited to such an arrangement. In fact, the hydrocratic generator of the invention may be used in any situation which can exploit the energy produced by the mixing of relatively low salinity fluid and relatively high salinity fluid, irrespective of their nature. Thus, the fluid may be fresh water, ocean water, desalinated water, sanitation or waste water, or any other fluid, without limitation, the combination of which with one other such fluid will produce the necessary energy by virtue of mixing. 
       FIG. 29  shows a further embodiment of the invention. The hydrocratic generator  560  comprises a top tube  562  and an lower tube  564 . The top tube  562  has open upper and lower ends  566  and  568 . The lower tube  564  also has open upper and lower ends  570  and  572 . The top tube  562  has a turbine  574  at or near its lower end  568 . The top tube  562  is of smaller dimension than the lower tube  564  so that the lower end  568  of the top tube  562  is received with in the upper open end  570  of the lower tube  564 . A brine line  576  feeds the top tube  562 . There is a gap between the lower tube  564  and the lower end  568  of the top tube  562 . This gap is preferably sufficiently large so that the percentage at the bottom of the lower tube will about 36% ppt or less. 
       FIG. 30  shows a hydrocratic generator  580  having a top tube  582  and a lower tube  584 . These tubes are arranged more or less as the top tube  562  and lower tube  564  are shown in  FIG. 29  of the drawings. There may of course be dimensional variations in the sizes and relative sizes of the top and lower tubes. In  FIG. 30 , there is a first portion  586  of a brine line  588 , and second portion  590  of the brine line  588 . These portions are demarcated generally by a head  592 . The second portion  590  of the brine line  588  extends into the top tube  582  and has a plurality of holes  594  along its length. The head is shown in a different view in  FIG. 31  of the drawings. A turbine  596  is located at or near the lower end of the top tube  582 . 
     In the embodiments shown in  FIGS. 29 and 30  of the drawings, the lower end of the top tube preferably extends a short distance downwardly of the upper end of the bottom tube and a gap is provided therebetween. 
     Reference is now made to  FIG. 34  of the drawings, which shows a hydrocratic generator contained in a pool  600 . The pool  600  comprises a chamber  602  defined by side walls  604 . A hydrocratic generator  606  is shown in schematic form, and is located within the chamber  602  of the pool  600 . As seen in  FIG. 35  of the drawings, the hydrocratic generator  606  is mounted on a supporting structure  608 , which may be adjustable, and which places the hydrocratic generator  606  in a predetermined and preselected space within the pool, as may be determined to be an optimal position. 
     A cooling water/waste water discharge inlet  610  conveys the cooling water/waste water into the chamber  602 , and, as best seen in  FIG. 35 . The inlet  610  comprises an end  614 . The end  614  is approximately at the open end of the inlet  616  of the hydrocratic generator. The discharge  612  passes through the inlet  610 , and exits the inlet  610  at the open ended inlet  616  of the hydrocratic generator. 
     A separate brine conduit  620  conveys brine therethrough from a source and into the pool  600 . The brine fills the chamber  602 , and rises to a level which is above that of the hydrocratic generator  606 . The level of the discharge  612  is such that the hydrocratic generator  606  is located completely within the discharge  612 . 
     It will therefore be appreciated that the pool is essentially filled with the brine conveyed from a source. Cooling water/waste water discharge passes through the inlet  610 , and exits therefrom near the open-ended inlet  616  of the hydrocratic generator. As the cooling water/waste water exits the inlet  610 , it draws in brine from the pool surrounding the hydrocratic generator  606 , as indicated by arrows  622  and  624 . AS such, a mixture of cooling water/waster water discharge and brine enters the hydrocratic generator  606 , and the difference in osmotic potential, as already described in detail above, is used to drive a turbine  626 . The turbine is connected to a generator  630  where the power may be stored, channeled or otherwise disposed of in a large number of different ways. 
       FIG. 34  shows a side view of the hydrocratic generator illustrated in  FIG. 34  of the drawings. As will be seen in both FIGS.  34  and  35  of the drawings, the brine in the pool, as well as the mixture exiting the hydrocratic generator at end  632 , eventually exits the pool  600 , and is discharged to the ocean through discharge pipe  634 . 
     Reference is now made to  FIGS. 32 and 33  of the drawings which show a system somewhat similar to that illustrated and described in  FIGS. 34 and 35 , where the various structures are essentially the same, except as will be described below. In  FIG. 34 , the pool is filled with brine, and the cooling water/waste water discharge exits the inlet  610  at the open-ended inlet  616  of the hydrocratic generator  606 . In contrast, the embodiment shown in  FIGS. 32 and 33  of the drawings show a pool  600  which is filled with cooling water/waste water discharge which enters through the pipe  610 , and fills the pool to a level above the position of the hydrocratic generator. In  FIGS. 32 and 33 , the brine conduit  620  discharges the brine at the open end  615  of the hydrocratic generator  606 . In the hydrocratic generator, a mixture of both brine and the cooling water/waste water discharge travel, and provide the necessary osmotic potential to drive the turbine  626 , which produces power stored in the generator  630 . 
     In the embodiments shown in  FIGS. 32 and 33  on the one hand, and  FIGS. 34 and 35  on the other, it will be appreciated that the relative proportions of cooling water/waste water discharge and brine respectively in the hydrocratic generator  606  will differ. Furthermore, the size, diameter, dimensions and other physical attributes of the inlet  610  in  FIG. 34  of the drawings may be varied, and the same dimensions and the like of the brine inlet  620  in  FIG. 32  may be varied, so that a desired relative proportion of cooling water/waste water discharge and brine is obtained. 
     In the embodiment shown in  FIG. 32  of the drawings, the open end  616  of the hydrocratic generator may be somewhat flared with a frusto-conical wall  638 , best seen in  FIG. 32  of the drawings. 
       FIG. 36  of the drawings shows another embodiment, in this case with the hydrocratic generator arranged vertically, as compared with  FIGS. 32 to 35 , where the hydrocratic generator is mounted in a horizontal or substantially horizontal position. It will be appreciated that mounting of the hydrocratic generator may also be at any suitable angle between vertical and horizontal, as may best be calculated to produce an optimum amount of osmotic potential, and therefore drive the turbine for maximum power output. 
     In  FIG. 36 , there is illustrated a closed tank  646 , in which is contained a hydrocratic generator  648 . The hydrocratic generator has an open lower end  650 , and an open upper end  652 . Near the open upper end  652 , there is mounted a turbine  654 , connected to a generator  656 , for capturing and storing energy, and has been described previously in this specification, and will not be repeated at this point. 
     The closed tank  646  is fed by a brine line  658 , from which brine from a source is discharged into the closed tank  646 . The closed tank  646  is also fed by a cooling water or effluent line  660 , which enters through the base of the closed tank  646  and discharges at approximately the level of the lower open end  650  of the hydrocratic generator  648 . Both cooling water or effluent discharged through the pipe  660 , and brine contained within the closed tank, enter the hydrocratic generator  648 , and the osmotic potential produced by the mixing of these two fluids will drive the turbine  654 , to provide energy to generator  656  as has been described. The mixture exiting through the upper open end  652  of the hydrocratic generator  648 , as well as brine contained within the closed tank, but surrounding the hydrocratic generator  648 , are permitted to exit through the overflow or outflow pipe  662 . 
     The closed tank  646  illustrated in  FIG. 36  of the drawings may be located on land, or it may be located under water, either fully of partially. 
     Reference is now made to  FIG. 37  of the drawings, which shows an embodiment similar to, but not identical with, that shown in  FIG. 36  of the drawings. The structure of the closed tank  646  (reference numerals in  FIG. 37  will be the same as those used in  FIG. 36 , since the structure is essentially identical) is fed with a pipe  658  that injects cooling water or effluent into the close tank. In this embodiment, the pipe  660  feeds brine to the lower open end of the hydrocratic generator  648 . The embodiment in  FIG. 37  thus shows the reverse use of the cooling water or effluent on the one hand, and the brine on the other, both of which, however, are introduced into the hydrocratic generator to create the osmotic potential for driving the turbine  654 . Once more, different proportions or relative amounts of the cooling water or effluence/effluent and brine respectively, may be introduced into the hydrocratic generator depending upon the dimensions, sizes, etc. of the open ends of the hydrocratic generator, as well as the line  660 . 
     Reference is now made to  FIG. 38  of the drawings which shows an alternate underwater configuration of the hydrocratic generator illustrated in  FIGS. 36 and 37  of the drawings. In  FIG. 38 , there is shown a tank  678 , but with an open top  680 . The tank itself may be located either above the ocean, or below the ocean surface. Within the tank there is formed a hydrocratic generator  648 , having the turbine  654  and generator  656 . In the embodiment shown in  FIG. 38 , brine is introduced through the pipe  658 , while cooling water or effluent is introduced through the pipe  660 . However, this could be reversed so that the opposite situation would prevail. 
     The embodiment shown in  FIGS. 32 to 38  may, for example, be optimally used where a desalination plant and a power plant or a sanitation district may be working together. Thus, the sanitation district would pipe the effluent over to the desalination plant, so that at least a portion of effluent from the sanitation runs through the tank, and thereafter becomes incorporated into the overflow which is sent out to sea with the rest of the effluent. The mixture of brine and waste water, as already described with respect to these Figures, drive the hydrocratic generator to generate power. 
     In one embodiment, a power plant pipes over a portion of the sea water that was used for cooling purposes, to be run through the tank. The overflow then goes back into the outflow line, where it will be run through a desalination device to bring the salinity within less than 4% of the ambient salinity of the sea water and, possibly, generate more power. 
     More than one such hydrocratic generator of the type described in  FIGS. 32 to 38  may be used in combination, wherein, for example only, one hydrocratic generator is formed within a pool on land, and a second hydrocratic generator is formed in the ocean, that generates power from the combined desalination and effluent and/or waste water. 
     Reference is now made to  FIG. 39  of the drawings which shows a down tube  702  having an upper end  704  and a lower end  706 , the down tube  702  being hollow and open at each of its ends  704  and  706 . A turbine or propeller  708  is shown near the lower end  706  of the down tube  702 . The turbine  708  can be of many different configurations, formats and embodiments as has been discussed with respect to other Figures in this application and specification. 
     Above the down tube  702  there is shown schematically a brine line  710 . 
     At selected points along the down tube  702  there are formed at least one, but preferably a plurality, of openings  712 , with each of the openings having adjacent thereto a cup or scoop  714 . The cup  714  has an open upper end  716 , so that fluid can flow from the ambient, or area surrounding the down tube, through the open end  716 , in the opening  712 , and into the interior of the down tube  702 . 
     The down tube  702  is typically located in an ambient solution  718 , and typically the salinity of the ambient solution  718  will be less than the salinity of the brine entering through the brine line  710 . 
     In  FIG. 40  of the drawings, a down tube  720  is schematically illustrated, with similar components and structure to that in  FIG. 39 . To the extent possible, the same reference numerals have been used to describe the same features and elements. The down tube  720  illustrated in  FIG. 40  of the drawings has, as will be observed, a tapering effect, wherein the diameter of the down tube  720  at the lower end  706  is less than the diameter of the down tube at the upper end  704 . In this particular embodiment shown in  FIG. 40  there is a fairly consistent taper from the upper end  704  to the lower end  706 , but it is within the scope of the invention that the degree or extent of tapering may vary along the length of the down tube, and, further, that the tapering may occur only along certain sections, while other sections may be of substantially consistent diameter. 
       FIG. 41  of the drawings shows yet a further embodiment of a down tube which may be constructed in accordance with the present invention.  FIG. 41  shows a down tube  722 , and once more, to the extent possible, corresponding reference numbers for corresponding components will be used, as was done in  FIGS. 39 and 40 . 
     In  FIG. 41 , the down tube  722  tapers from a wider diameter upper end  704  to a lesser diameter lower end  706 , and the plurality of cups or scoops  704  are distributed at selected locations on the outer side of the down tube  722 . 
     In  FIG. 41 , there is also shown a series of successively wider down tube elements  724 , comprising an upper down tube element  726  and a lower down tube element  728 , the lower down tube element  728  being of substantially consistent diameter, but of greater diameter than the upper down tube element  726 , also of fairly consistent diameter. Note that the upper and lower down tube elements  726  and  728  may also be tapered, and may either increase in diameter from upper end to lower end, or decrease in diameter from upper end to lower end. 
     Note that the down tube elements  724  shown in  FIG. 41  of the drawings are used with a down tube  722  of decreasing diameter, as shown also in  FIG. 40 , but it is important to note that the down tube element  724  may also be used with the down tube  702  which has a diameter of substantially consistent size over its length. 
     As illustrated in  FIGS. 39 ,  40  and  41 , the down tubes have openings or perforations  712  at various locations with the cup or scoops  714  optionally located over the openings  712 . Some or all of the openings  712  may be present without the cup  714 . The cup  714  and opening  712  arrangement is constructed for the purpose of increasing the volume of ambient solution  718  which enters the down tubes  702 ,  720  and  722 . 
     With respect to these Figures, each hydrocratic engine may typically have fixed interior dimensions. Thus, as the water traveling through the hydrocratic engine, or down tube, increases, the velocity of the water will also increase. As such, the tapering designs of the down tube(s) may have the desired effect of increasing the volume of water passing through the down tube over a given period of time, at the same time increasing the velocity of the water and the amount of power produced by the hydrocratic engine. It will be appreciated of course, that increase of volume and velocity of water passing over the turbine or generator  708  will drive the turbine  708  with increased energy so that more power can be produced. 
     Reference is now made to  FIG. 42  of the drawings showing a further embodiment of a hydrocratic generator, constructed in accordance with one aspect of the invention. As will be seen in the drawing, the hydrocratic generator comprises a chamber  730  defining an upper space  732  and a lower space  734 . The upper and lower spaces  732  and  734  being separated by wall  736 . A down tube  738  is located within the upper space  732 , and comprises a tapering configuration with an upper end  740  having a larger diameter than the lower end  742 . The wall of the down tube  738  has at least one and preferably a plurality of openings  744 . 
     The wall  736  has an opening  746 , and the lower end  742  of the down tube  738  has a portion which extends through this opening  746 , in a manner such that a seal is formed between the wall of the down tube  738  and the wall  736 . As will be described below, any fluid contained in the space  732  will not be able to move or pass through the opening  746 , which will be sealed in an appropriate manner with the down tube  738 . 
     The upper space  732  of the chamber  730  has a brine inlet  748  and a fresh water inlet  750 . The brine inlet has a discharge nozzle  752  which is located immediately above the upper end  740  of the down tube  738 . The upper space  732  also has an overflow outlet  754  near the upper end thereof. 
     In the lower space  734  of the chamber  730 , there is constructed an impeller  756  which is attached to a drive shaft  758 , the drive shaft itself being attached to a generator  760 . The drive shaft  758  extends through the wall of the chamber  730 , since, as will be seen in  FIG. 42 , the generator  760  is located outside of the chamber. 
     The lower space  734  has a drain outlet  762 , and may in one embodiment connect to the overflow outlet  754 , which may have a larger diameter, so that either overflow from chamber  730 , or discharge from lower space  734  are conveniently removed through the same structure. It will, however, be appreciated that the drain outlet  762  may discharge independently of the overflow outlet  754 . 
     In operation, the hydrocratic generator as shown in  FIG. 42  operates when fresh water is introduced into the upper space  732  through the fresh water inlet  750 . Eventually, the upper space  732  fills with fresh water, and may fill up to level  764 , after which excess fresh water overflows into the overflow outlet  754  for discharge into the ocean. At the same time, brined fluid is introduced through the brine inlet  748 , and the nozzle  752  is below level  764 . The brine discharged through the nozzle  752  enters into the down tube  738 . As the brine fluid moves down through the down tube  738  it is mixed with fresh water which enters the down tube either through the open upper end  740  of the down tube, and/or through one of the plurality of openings  744 . The mixing has the effect already described in previous embodiments of the invention, and the mixture is discharged through a nozzle  766  located at the very lower end of the down tube  738 , into the lower space  734 . As the mixture exits the nozzle  766 , the mixture drives the propeller  756  which in turn, through the drive shaft  758 , powers the generator  760 , which in turn is able to store and thereafter transmit power in the usual way as described. The mixture of fluid entering the lower space  734  ultimately drains through the drain outlet  762  located in the floor of the chamber  730 , and is discharged to the ocean either through a separate outlet, or by joining with the overflow outlet  754 , as already described. 
     Note that the down tube  738  in  FIG. 42  is shown in a tapered configuration, but this down tube  738  may be of fairly uniform diameter in other configurations, or tapered in the opposite direction. Further, the existence of the opening  744  as well as their number, shape and size, can vary in accordance with the invention. Furthermore, at least some of the openings  744  may have attached thereabout the cup or scoop as has been described and illustrated with respect to  FIGS. 39 ,  40  and  41  of the drawings. It should also be noted that the down tube  738  in  FIG. 42  is not to scale, and the Figure is schematic for the purposes of illustrating the components and overall structure of the invention. 
     Reference is now made to  FIG. 43  of the drawings showing a further aspect of the invention. The hydrocratic generator shown in  FIGS. 43 and 44  are for most purposes the same, except for the location thereof.  FIG. 43  shows a hydrocratic generator of the invention when mounted or contained within a substantially closed reservoir, while  FIG. 44  shows the hydrocratic generator of generally the same structure when located in the ocean. 
     In  FIGS. 43 and 44  there is shown a hydrocratic generator including a down tube, generally designated with the reference numeral  770 . The down tube  770  is generally in a substantially vertical orientation. The down tube  770  has a number of portions, as will now be described. 
     The down tube  770  has a funnel portion  772  at the top thereof, with a wider diameter open end  774 , tapering down to a narrower lower end  776 . At the lower end, the funnel portion  772  transitions with a circular tube portion  778 . The generally round or circular tube portion  778  transitions to a square tube portion  780 , with a transition  782  therebetween. At the lower end of the square portion  780 , there is formed a venturi tube portion  784 , with a transition  786  formed there between. The venturi tube portion  784  tapers from a wide diameter end  788  to a narrow diameter end  790 , the venturi tube portion  784  having a discharge opening  792  at its narrow end  790 . 
     A brine inlet line  794  transmits brine to the down tube  770  and has a discharge opening  796  just above the open end  774  of the funnel portion  772 . 
     It will be noted that the square tube  780  has at least one, and preferably a plurality of openings  798  through which water from the ambient area around the down tube  770  can be drawn into the down tube  770 . 
     With specific reference to  FIG. 43 , the down tube  770  as described above is formed within a reservoir  800 , having side walls and at least a base wall. There is a fresh water inlet  802  for allowing fresh water into the reservoir  800 , and an overflow outlet  804  for overflow. A portion of the venturi tube  784  portion extends through an opening  806  in the lower wall of the reservoir  800 , and the mixture of liquids discharged from the opening  792  is used to drive an impeller, turbine or the like, as has been described with reference to other embodiments. 
     In  FIG. 44  of the drawings, the down tube  770  is formed within the ocean  808 , but is otherwise of fairly similar construction to that shown in  FIG. 43 . 
     In the down tube illustrated in both  FIGS. 43 and 44 , brine enters the funnel portion  772  of the down tube  770 , and flows through the down tube towards the discharge opening  792 . The brine liquid is mixed with fresh water, or ocean water, as the case may be, the mixture driving the liquid outwardly form the discharge opening for the purposes of powering a turbine or other appropriate device, as has been described. 
     Reference is now made to  FIG. 45  of the drawings. In  FIG. 45 , a hydrocratic generator  814  is shown including a down tube indicated generally by the reference numeral  816 . In  FIG. 45  the down tube  816  is generally cylindrical and of fairly consistent diameter along its length. However, it may be tapering of the down tube  816  along its length, or a portion thereof. 
     The down tube  816  has a meshed screen portion  818 , and a substantially solid portion  820 . At the lower end of the solid portion there is formed a turbine  822 , impeller or other device by means of which the energy produced within the down tube can be harnessed. 
     It will be seen that the down tube  816  shown in  FIG. 45  is formed in the ocean  824 , below the surface  826  thereof. However, it should also be understood that a down tube  816  having the construction and configuration of that as illustrated in  FIG. 45  may also be formed in a body of fresh water. 
     At the upper end of the down tube there is provided a brine line  828  having a discharge opening  830  which discharges brine immediately above the upper end of the down tube. Thus, brine enters the down tube  816  at the top thereof and through the open end, the brine water in the down tube thus having a higher concentration of solutes than in the surrounding ocean water  824 . As such, hydrocratic forces cause water from the ocean  824  to pass through the meshed screen portion  818  into the down tube  816 , such movement being facilitated by the lower concentration of solute to the higher concentration solute respectively. In  FIG. 45 , the down tube  816  has a fixed diameter and the additional water passing through the mesh screen portion  818 , introduced into the down tube, results in an increasing velocity of the water passing and moving through the down tube  816 , thereby increasing the kinetic energy of the water in the hydrocratic engine. These hydrocratic forces will, at least to a large extent, prevent interior water, or water mixture flowing within the down tube  816 , from exiting the down tube  816  through the meshed screen portion  818 , and into the ocean. Such prevention of flow will occur up to a back pressure point, and this point may be selected and determined based on various parameters including, but not limited to sizes and dimensions of the down tube  816 , respective concentrations of the brine and ocean water respectively, as well as such other determining factors. 
     Other Applications/Embodiments 
     In the preferred embodiments discussed above, the up tube  40  is located in a body of water of high salinity and high negative osmotic potential such as an ocean or a sea. The water of high salinity and high negative osmotic potential enters the up tube  40  in a ratio of greater than 8:1 salt water to fresh water, more preferably 30:1 salt water to fresh water, and most preferably about 34:1 or higher. The mixing of the fresh water of low negative osmotic potential with the sea water of high negative osmotic potential in the up tube  40  causes upwelling and draws sea water into the up tube  40  through the openings. The upwelling water in the up tube  40  rotates propellers  62 , spiral fans  70  or turbines  130 ,  261 , which are attached to a drive shaft  64 ,  264 . The rotating shaft  64 ,  264  turns the electrical generator  66 ,  266  generating electrical power from the difference in osmotic potential between the fresh water introduced into the down tube  20  and the water of high salinity which enters the up tube  40  through the openings in the up tube  40 . 
     Because the method depends on having solutions of different osmotic potentials exiting the down tube  20  and entering the up tube  40 , it is preferable that the source of fresh water exiting the down tube  20  and the source of the water of high salinity entering the up tube  40  continue to have different osmotic potentials over time so that power generation continues over a long period of time. For example, if the body of water of high salinity surrounding the up tube  40  is small, the fresh water exiting the down tube  20  can dilute the water of high salinity after exiting the up tube  40 , reducing the difference in osmotic potential between the fresh water and the water of high salinity. Reducing the difference in osmotic potential between the fresh water exiting the down tube  20  and the water of high salinity entering the up tube  40  reduces the amount of energy available. It is therefore generally advantageous that the body of water of high salinity have a large volume. Locating the up tube  40  in a large body of water having high salinity such as the ocean or the Great Salt Lake is therefore a preferred embodiment. 
     Alternatively, the invention can be operated between bodies of salt water having different salinity or between waters at different depths of the same body of water. For example, the salinity and temperature of sea water is known to vary with depth and location. In the Hawaiian islands, at a depth of 1000 meters, the ambient water temperature is approximately 35° F., with a salinity of approximately 34.6 ppt. The surface temperature is approximately 80° F. with a salinity of approximately 35.5 ppt. Thus, an osmotic energy potential (albeit small) exists between the surface waters and the waters at 100 meters depth. 
     While the present invention is disclosed in the context of generating power by directly contacting and mixing fresh water with sea water in an apparatus located in the ocean, it is to be understood that the apparatus and method are not limited to this embodiment. The techniques and concepts taught herein are also applicable to a variety of other situations where aqueous solutions having differing osmotic potentials are available. For example, in one embodiment, the apparatus and method may be applied to a concentrated brine from a desalinization plant being mixed with the less-concentrated brine in sea water. In another embodiment, a treated sewage effluent, a fresh water stream, can be mixed with sea water. If desired, an osmotic membrane or osmotic water exchange plenum may be provided at the outlet end of the down tube and/or at the outlet (top) of the up tube in order to increase the efficiency of energy production. The apparatus and method may thus be applied to a wide range of applications in which two solutions of differing osmotic potential are available. 
     The various embodiments of the invention disclosed and described herein are exemplary only. As such, these example embodiments are not intended to be exhaustive of all possible ways of carrying out the invention or even the most economical or cost-efficient ways of carrying out the invention on a commercial scale. Accordingly, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.