Abstract:
A pump uses solar energy to heat bimetals and other materials with high expansion coefficients to create movement that is coupled to pistons or impellers resulting in a fluid pumping action. The moving pistons or impellers are used to push salt water (or any fluid) through a membrane for filtration. Furthermore, the mechanical movement, powered by solar energy can be used for a variety of applications including pumps to move liquids or gases.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the use of solar energy to desalinate sea water. 
       BACKGROUND OF THE INVENTION 
       [0002]    Global fresh water shortages are affecting not only people&#39;s health, but regional economies and politics. Nearly two million children die annually from lack of access to fresh drinking water and it is estimated that by 2025 almost two billion people will live in areas where water is scarce. Although the Earth&#39;s seawater is abundant, freshwater represents less than 3% of the Earth&#39;s total water. Several processes are available to filter seawater in order to obtain freshwater. In one such process salt water is forced through a semi-permeable filter (e.g., a polymer membrane), which results in freshwater exiting the filter, leaving behind the salt and impurities. This process is called reverse osmosis, and it requires significant energy. Reverse osmosis is used by large-scale desalination facilities around the world that rely on nuclear power to provide the energy. 
         [0003]    Solar energy is usually abundant in climates that are very dry and lack water. Therefore, using the sun&#39;s energy to effect desalination would be very efficient. 
         [0004]    Most materials expand when they are heated and contract when they are cooled. However, there are materials that do the opposite and contract in certain directions as they heated and expand when they are cooled. These are called negative thermal expansion materials and include such materials as graphene, beta-quarts and some zeolites. During daylight the sun can heat most materials causing them to expand and at night when the temperatures are lower they contract. The opposite occurs with negative thermal expansion materials. With the heating during the day and the cooling at night the types of materials will continuously cycle between expanding and contracting. Expanding or contracting materials can also be cooled by a variety of methods for example artificial shade provided by canopies or cooling fluids. When materials are cooled artificially they increase the rate of the expanding or contracting cycle that now does not have to depend on only the natural cooling during nighttime. 
         [0005]    When two metals having dissimilar thermal expansion coefficients are bound together, they result in a bi-metal strip that bends in one direction with heat and straightens or bends in the other direction as it cools. The bending of strips of brass and steel are used to measure temperature in thermostats. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention relates to the use of solar energy to heat bi-metals and other materials with high absolute or differential heat expansion coefficients that are coupled to pistons or impellers that in turn are used to force sea water through semipermeable (filtration) membranes to achieve desalinization. 
         [0007]    In accordance with the invention a piston or impeller is moved by a mechanical coupling connected to a material that expands (or contracts) when exposed to radiant heat from sunlight. Various materials, metals and alloys have different expansion rates depending on their internal properties. With this invention solar energy is used to heat a conventional material structure resulting in an expansion of the structure. The expanding structure results in movement. This movement can be coupled to one or more pistons (or impellers) that are used to pump fresh or salt water as well as pressurize a container of saltwater or contaminated water in order to push the saltwater or contaminated water through a semipermeable membrane to desalinate or clean it. 
         [0008]    In the evening the metal cools and the expansion of the metal is replaced with a contraction. During this period the desalination can be stopped. However, in an alternative design the contracting metal also pushes salt water through a second membrane. 
         [0009]    The invention can be used for desalination of saltwater as well as filtration of any type of fluid. In addition the same process of moving pistons or impellers by thermal expansion of metals or other materials by using solar energy can be used to pump saltwater and fresh water to and from the desalination plant. Furthermore, the use of this process can be the basis of pumps used to move any type of liquid or gas. For example, oil refineries may use solar pumps for moving crude oil or refined petroleum products. In addition the mechanical movement necessary to power a generator that procures electricity can be provided by the expansion and contraction of materials with high thermal expansion rates and sunlight. In order to produce sufficient movement the actual motion may need to be amplified, e.g., with a gear chain. 
         [0010]    When the present invention is used with single structure metals, the expansion and contraction is along the axis of the metal. However, an additional feature of the invention is to use bimetals or a series of metals that have different coefficients of thermal expansion. If such metals are bonded together, when they expand at different rates, the structure tends to bend away from the axis. This bending is an indication of temperature when bi-metals are used in a thermostat. 
         [0011]    The deformation of materials by positive or negative thermal expansion along the axis of the metal or by differential thermal expansion at an angle provides a mechanical force. This force can be connected to pistons or impellers and used to ultimately pump fresh or salt water through pipes and/or force the fluid through a filter. 
         [0012]    The metals will deform during the day when sunlight is abundant and at night the metals will cool and returned to their original shape. The movement of pistons is coupled to the (movement) expansion of the metals during heating and (movement) contraction of the metals during cooling. This provides a continuous cycle of pumping water through filters. 
         [0013]    Cooling is required to contract materials that expand when heated (or in special cases expand materials that enlarge during cooling). The cooling can be provided by lack of sunlight at night or an artificial shade provided by a movable canopy. In addition cooling can be provided by fluids that are pumped on to or around the heated elements. For example, heated, expanded bimetal discs can be cooled by fluid, which will result in the contraction of the bimetal discs at a faster rate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The foregoing and other objects and advantage of the present invention will become more readily apparent upon reference to the following specification and annexed drawings in which: 
           [0015]      FIG. 1A  is an elevation view of a solar desalinization system according to the present invention with a piston against a container wall and bimetal discs contracted in the cold position,  FIG. 1B  is a view with the piston pushed all the way into the chamber next to a filter and with the bimetal discs expanded in the heated position, and  FIG. 1C  is a view similar to that of  FIG. 1A , but with the bimetal discs replaced with an axially expandable thermal expansion material structure; 
           [0016]      FIG. 2  is an elevation view of an alternative arrangement of the solar desalinization system with a second filter so that desalinization occurs both when the piston is pushed all the way in and when it is withdrawn; 
           [0017]      FIG. 3  is an elevation view of a solar pump according to the present invention, which has the structure of  FIG. 1 , but without the filter so that it operates simply as a pump and not a desalinization system; 
           [0018]      FIG. 4  is an elevation view of a solar pump as shown in  FIG. 3 , but with a channel to divert fluid from chamber to cool the expanded bimetal discs; 
           [0019]      FIG. 5  is a plan view of a solar pump wherein a single set of bimetallic discs drives a plurality of pumps; 
           [0020]      FIG. 6  is a perspective view showing an arrangement in which the linear movement of heated and cooled bi-metallic discs is converted into rotary movement to drive an impeller; 
           [0021]      FIG. 7  is a perspective view showing an arrangement in which rotary motion as a result of the linear movement generates electricity; 
           [0022]      FIG. 8  illustrates an alternative arrangement for the solar desalinization system of  FIG. 1  wherein the filter is in the form of a semipermeable cylinder; and 
           [0023]      FIG. 9  shows an arrangement in which linear motion of the bi-metallic structure results in the generation of electricity. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]      FIG. 1  shows an example of a bimetal configuration that is constructed from a series of bimetal discs  16 ,  18 ,  20 , and  21 . The bimetal discs are made of two metals  4  and  5  that have substantially different thermal expansion rates. Although the diagram illustrates bimetal discs, any shape that maximizes movement in the linear or rotational direction can be used in the bimetal configuration. As an alternative, a single metal bar with a high coefficient of expansion can be used in place of the discs, but it would likely have a much smaller and slower displacement. A metallic structure thermal expansion material  14 ′ is shown in  FIG. 1C  substituted for the bi-metallic discs. The tapered nature of the structure caused the pointed end to move more in the axial direction than would a straight bar. 
         [0025]    The bimetal discs are connected to each other and to a piston  12  by shaft  14 . When valve  25  is open fluid can enter a portion  30  of the interior of chamber  3  through pipe  10 . After the portion  30  of the chamber is filled with fluid, valve  25  can be closed and the bimetal discs  16 ,  18 ,  20 , and  21 , can be exposed to sunlight and expand, thereby pushing shaft  14  and piston  12  to the left in  FIG. 1A . As piston  12  is moving it is pushing fluid through a semipermeable membrane  6 . As this occurs, valve  24  must be open in order to allow filtered fluid to exit through pipe  9 . The expansion of the discs and movement of the piston are relatively slow, but they can have great force. If the structures in  FIG. 1  are relatively large, even with the slow movement of the piston, a large quantity of salt water can be desalinated.  FIG. 1B  shows the discs in their fully expanded condition and with the piston  12  pushed against the membrane  6 . 
         [0026]      FIG. 1  shows one possible configuration with the semipermeable membrane  6  being removable from chamber  3 . As a result, semi permeable membrane  6  can be replaced with a new membrane when required. However any possible configuration of having a piston or pistons pushed by bi-metals can be implemented. For example as shown in  FIG. 8 , bimetal structures can push a piston  12 ′ into a cylindrical permeable membrane  6 ″ where the entire cylinder is made of semipermeable membrane. The cylindrical semi permeable membrane can then be located in an appropriate housing or chamber  3 ′. With this arrangement a large surface of the membrane is exposed and used in the desalinization process. In particular, salt water can enter the interior of the cylinder  6 ″ through pipe  10 ″ as piston  12 ″ is withdrawn to the right in  FIG. 8 . After being fully retracted, a valve on pipe  10 ″ is closed and the piston is pushed into the cylinder due to some form of thermal expansion. As this occurs, the salt water is forced through the cylinder in all directions. The fresh or filter water exits the housing  3 ′ through pipe  9 ″. 
         [0027]    Although  FIG. 1  shows a pump using at least one piston to pump fluid or gas, the thermal expansion and movement of shaft  14  can also be coupled to an impeller type of mechanism (or any mechanism that is designed to move fluids or gases and requires a mechanical force) as shown in  FIG. 6 , and is not limited to moving fluids or gases by pistons. For the impeller to operate a mechanism is required that converts linear movement into rotary movement.  FIG. 6  shows such an arrangement using a rack-and-pinion mechanism to generate the rotary motion. As the shaft  14  moves, the teeth  15  on the rack move. This movement causes pinion  17  to turn, which results in the turning of a shaft  19  that drives impeller  23 . The rotating blades of the impeller  23  can provide the fluid to the portion  30  of the chamber  3  shown in  FIG. 1 . The force of this fluid can cause it to move against and through the membrane  6  in the chamber  3 , even without the aid of the moving piston  12 . 
         [0028]      FIG. 1B  shows the bimetal discs  16 ,  18 ,  20 , and  21 , expanded by heat from sunlight so that shaft  14  and piston  12  are pushed all the way into container  3 . This results in the fluid contents being forced through the semi permeable membrane  6  and filtered fluid passing out of open valve  24  and pipe  9 . As daylight ends the discs begin to cool and contract. At that point the desalinization could stop for the day. However, if chamber  3  is provided with another membrane  6 ′ as shown in  FIG. 2 , the contraction of the discs and movement of the piston back to its original position could force fluid through it into a portion  90  within chamber  3 . This could create fresh water that could enter tube  9 ′ if valve  24 ′ is opened and thus continue the process at night. In such a case the fluid enters a region  60  which is behind the piston. Note that the portion  30  of the chamber has been reduced to the area between the front of the piston and the membrane  6 . 
         [0029]    With the arrangement in  FIG. 2 , a valve  25 ′ is opened as the piston moves to the left in  FIG. 2  to fill the portion  60  with salt water. As the piston moves back, that valve is closed and valve  24 ′ is opened to remove the fresh water from portion  90 . At the same time valve  25  is opened to allow salt water to enter the portion  30  at the front of the piston as it moves to the right. The valve  24  would then be closed. 
         [0030]    It should be noted that with this arrangement the shaft  14  passes through the membrane  6 ′. This needs to occur through a water tight passage  32  in order to prevent the mixing of the salt and fresh water. 
         [0031]      FIG. 3  shows a bimetal configuration of a pump that can be used to pump fluids or gases. Note that as compared to  FIGS. 1 and 2 , the membrane  6  has been removed. In  FIG. 3 , chamber  3  is filled with a fluid or a gas entering through pipe  10  when valve  25  is open and valve  24  is closed. The fluid or gas can now be pushed out of the chamber  3  when valve  25  is closed through open valve  24  and pipe  9 , when the bimetal discs are exposed to sunlight. The expansion of the bimetal discs and movement of shaft  14  and piston  12  will push out the gas or fluid from the portion  30  of the chamber  3  through valve  24  into pipe  9 . 
         [0032]    When all the fluids or gas are pushed out of portion  30  in container  3 , the bimetal discs can be cooled and shaft  14  and piston  12  can then pull gases or fluids from pipe  10  when valve  25  is open and valve  24  is closed, thus refilling the portion  30  with fluid or gas. This repetitive cycle results in a pumping action for fluids and gases. Valve  25  is closed when portion  30  is filled and valve  24  can be opened and the bimetal disc can be exposed to heat to pump out the contents. 
         [0033]      FIG. 3  shows a pump using a single piston to pump fluid or gas. However, a single set discs driving shaft  14  can be used to power a series of parallel pumps  3 A,  3 B, and  3 C as shown in  FIG. 5 . In addition the multiple pumps can have a series configuration. 
         [0034]    The pump described in  FIG. 3  (non-filtering) can be used to pump fluid (saltwater) to another filtering pump such as that shown in  FIG. 3 . Also, the pump can be sued to distribute fresh or filtered water from chamber  3  to where it is needed. 
         [0035]    In addition to providing fluid (that requires filtration) to the filtering pump, a pump described and shown in  FIG. 3  can be used to provide cooling fluid to a filtering pump that will cool the expanded elements and bring them to the contracted position. 
         [0036]    The filtering pump in  FIG. 2  has the bimetals expanded and the fluids pushed out of portion  30  in container  3 . This means that the bimetal discs need to be cooled in order to retract shaft  14  and piston  12 . The cooling can be done by decreasing the sunlight at night or artificially shading the bimetal discs or using fluid to cool the bimetal discs. Fluid used to cool the bimetal discs can be provided by the pump described and shown in  FIG. 3 . 
         [0037]      FIG. 4  illustrates such a cooling mechanism as an integral part of the pump. Piston  12  is shown against the wall of container  3  and in position to push the fluid or gas in portion  30  out of container  3  when the bimetal discs are expanded by exposure to sunlight. As the bimetal discs are approaching maximum expansion, valve  55  can be open so fluid can enter pipe  50  and pass into chamber  65 . Chamber  65  can not only act as a cooling fluid provider for the discs, but also as a movable shade for the discs. Thus the fluid released from chamber  65  and the shade it provides can cool down the bimetal discs. However, fluid can be provided only while the piston is still moving in the heat expansion direction. As contraction begins as a result of the fluid and shade from chamber  65 , shaft  14  and piston  12  will move towards the bimetal discs and as a result piston  12  will stop providing fluid to chamber  65  and will start drawing fluid or gas from pipe  10  when valve  25  is open and valves  24  and  55  are closed. If the shaft  14  moves fast enough that the piston is near the end of its travel away from the discs during only a part of the day and the contraction is due to the fluid and shade from chamber  65 , as opposed to sunset, the pumping cycle can then begin again by exposing the bimetal discs to the sun again so they expand. Thus a pumping cycle that is more frequent than the sun cycle is possible. 
         [0038]    Although  FIGS. 1A, 1B, 2, 3, 4 and 5 , illustrate expansion due to bimetals, any type of material that has a high thermal expansion rate, whether due to heating or cooling, can be used to power shaft  14  and piston  12  in order to filter or pump fluids and gases. See for example  FIG. 1C . 
         [0039]    The amount of sunlight (and heat) provided to expanding materials can be amplified by using reflective surfaces, e.g., reflector  28  in  FIG. 4 , that focus and concentrate sunlight on materials (e.g., the discs) that expand when heated. Parabolic reflective surfaces on structure  28  focus sunlight on the discs to maximize the heat transfer that expands the discs. If structure  28  is made movable, it can move the focal point on the discs during part of the cycle and can move the focused beam away from the discs during a cooling cycle, which would result in efficiently cycling of the expansion and contraction of the materials that provide movement to the solar pump. 
         [0040]    Electrical generators can produce electricity by converting mechanical energy into electrical energy. The source of mechanical energy for an electric generator can be the motion of a shaft or connecting rod that is connected to a thermal expansive structure or bimetal structure designed to expand when heated by sunlight as shown in  FIG. 7 . The movement resulting from expansion ultimately moves the shaft or connecting rod  14  that provides the mechanical energy required by electric generators to produce electricity. However, in order to generate electricity, typically a faster speed is required than the expansion speed of the present invention. Also, typically a rotary motion is needed, but linear generators as shown in  FIG. 9  can also be used. 
         [0041]    As shown in  FIG. 7  a higher speed rotary motion is accomplished by a rack-and-pinion arrangement  35 , which is similar to that in  FIG. 6 . However, the pinion  17 ′ in this arrangement has a step up gear ratio so that the slow movement of the shaft  14  is converted into a much faster rotation of shaft  19 ′. The shaft  19 ′ drives an electrical generator  37  that produces electricity. This electricity can be used to power the opening and closing of values in the desalinization plant or if there is excess electricity, it can be provided to the power grid. 
         [0042]    In  FIG. 9  a linear electrical generator is shown. It includes a tightly wound coil  40  and a shaft  41  with a series of magnets. As the magnets are moved through the coil, electricity is generated in the coils. In order to move the shaft  41 , the bi-metallic discs  16 ,  18 ,  20  and  21  are connected to shaft  14  as shown in  FIG. 1 . However, in generating electricity, it is helpful to have more speed than is produced by the discs. The extra speed is provided by a transmission  43  that amplifies the rate of motion of shaft  14  and applies it to shaft  41 . 
         [0043]    The elements of the embodiments described above can be combined to provide further embodiments. These and other changes can be made to the system in light of the above detailed description. While the invention has been particularly shown and described herein, with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.