2. Background Art Fresh water is a precious commodity in many areas of the world.

Fresh water is extremely scarce in certain arid regions of the world. Additionally, population growth, food production and expansion of industrial economies are depleting the world's supply of fresh water.

Methods of desalinating salt water have been proposed in order to replenish the world's supply of fresh water. It should be understood that salt water refers to a water solution that contains an amount of dissolved salt. Examples of salt water include, but are not limited to, sea water, brackish water, and treated waste water. Desalination is a process that removes salt, among other dissolved minerals, from salt water. Numerous technologies have been developed for desalination,

including thermal desalination, membrane desalination, and solar humidification.

Existing desalination techniques have significant limitations.

Thermal desalination techniques apply heat to distill fresh water from salt water. A significant amount of the world's desalination plants use thermal desalination techniques. Thermal desalination is commonly carried out using multi- stage flash distillation, multiple-effect distillation, or vapor compression. Thermal desalination generally consumes a relatively high amount of energy. In addition, thermal desalination techniques typically convert less than 100 % of the salt water input into fresh water output. Moreover, the equipment in thermal desalination units are commonly cleaned and ultimately replaced due to the effects of scaling and mineral build-up. Building thermal desalination units also commonly require a tremendous capital investment.

Membrane desalination employs energy or pressure to salt water to facilitate selective passage of fresh water or salt water through a membrane.

Membrane desalination is commonly carried out using reverse osmosis. Membrane desalination commonly necessitates high amounts of energy and large capital expenditures. Additionally, membrane desalination units commonly require relatively high maintenance costs associated with waste (or concentrate) handling and membrane servicing. Moreover, these units suffer from relatively low efficiency.

Solar humidification techniques commonly employ a solar house to use the sun to evaporate sea water and collect fresh water. The solar house generally requires a very large area to generate a relatively small volume of fresh water. As is true with most membrane desalination and thermal desalination, solar humidification commonly requires a relatively high amount of investment capital.

U. S. Patent No. 6,001, 222 discloses another type of solar humidification unit that employs an evaporation plant for distilling potable water from salt water. The plant includes a plurality of substantially equally spaced solar stills mounted on a black-colored solid metallic heat conducting plate. Each solar

still includes: (a) a vertically cylindrical container for holding a body of salt water and thin side walls with the inside and outside black-colored faces; (b) a floating cover layer of black-colored floating perforate plate or black colored floating particles; (c) an annular trough surrounding the top periphery of the cylindrical container and holding a transparent cover for the container that collects condensed water; and (d) a transparent plastic cover including a lower vertical cylindrical portion which merges into a semi-spherical top portion. The transparent plastic cover causes the condensed water to flow down the vertical cylindrical portion for collection in the annular trough.

U. S. Patent No. 5, 053, 110 discloses a solar humidification system utilizing a domed design for the evaporation chamber. The dome is designed to permit maximum collection of the distillate which has condensed on the dome's inner wall surface. Further, the same uniquely configured structure effectively limits re-evaporation of the condensate. The system provides a means of preheating the load prior to entry into the evaporation chamber. Several designs are included for such preheating, depending on geographic location and its exposure to the sun's rays.

Discharges from desalination plants using current methods produce several negative effects. Current methods produce a waste brine solution with salt concentrations above those of the salt water received by the system. Typically, these systems produce about 15 to 50 gallons of fresh water per about 100 gallons of sea water input. The other 50 to 85 gallons is the waste brine solution. The high salt concentration of the waste brine solution and fluctuations in salinity levels may kill organisms near the discharge region since the organisms cannot tolerate the magnitude or fluctuation of the salinity levels. Similarly, if a temporary desalination plant is shut down, the organisms that have become accustomed to high salinity levels and/or salinity fluctuations may be killed. In addition, discharges from desalination plants will be more dense than salt water and could sink to the bottom, potentially causing adverse effects on the benthic communities.

Many current desalination systems release unwanted chemical pollutants into the aquatic environment. Chemicals from pre-treatment of feed water may contaminate the environment. These chemicals may include biocides, sulfur dioxide, coagulants, carbon dioxide, polyelectrolytes, anti-scalants, sodium bisulfite, and anti-foam agents. In certain reverse osmosis plants, chemicals used in flushing pipelines and cleaning members may detrimentally affect the environment once released. These chemicals include sodium compounds, hydrochloric acid, citric acid, alkalines, polyphosphates, biocides, copper sulfate, and acrolein. In addition, certain chemicals used to preserve the reverse osmosis membranes in some reverse osmosis desalination systems may detrimentally affect the environment, once discharged. These chemicals include propylene glycol, glycerine, and sodium bisulfite.

It is therefore desirable to devise a method of desalinating salt water with solar energy that is economically viable and does not pose environmental concerns.

SUMMARY OF THE INVENTION According to a first embodiment of the present invention, a method for desalinating salt water with solar energy is disclosed. The method includes providing a transport for receiving a thin film of salt water, evaporating the salt water contained in at least a portion of the thin film by directing a concentrated sunlight beam at the portion of the thin film or a portion of the transport, and providing a vapor hood positioned above and spaced apart from the transport for collecting the evaporated fresh water. The salt water of the portion of the thin film is evaporated to produce evaporated fresh water. The evaporated fresh water is condensed to provide potable water.

In certain implementations of the first embodiment, the evaporating step can include the following sub-steps: reflecting a plurality of sunlight beams from a plurality of solar collectors onto at least one focusing mirror, focusing the plurality of sunlight beams via the at least one focusing mirror to produce a focused

sunlight beam, reflecting the focused sunlight beam from the at least one focusing mirror to a solar concentrator to concentrate the focused sunlight beam into concentrated sunlight, reflecting the concentrated sunlight from the solar concentrator to a beam shaping mirror to produce a concentrated sunlight beam, and directing the concentrated sunlight beam at about the portion of the thin film or a portion of the transport.

Each of the plurality of solar collectors can include a solar collector backing plate and one or more mirrors secured to the solar collector backing plate.

The one or more mirrors can be constructed of a single, substantially flat mirror.

Alternatively, the one or more mirrors can be constructed of a plurality of substantially flat mirrors arranged to form a substantially planar surface when secured to the solar collector backing plate. Moreover, the one or more mirrors is treated with an anti-oxidant coating material.

The first embodiment can further include recovering minerals produced as a by-product of the evaporation step. The first embodiment can also include providing a vapor condenser that is connected to the vapor hood, and condenses the evaporated fresh water. Moreover, the method of the first embodiment can include generating electricity for converting the evaporated fresh water into electricity. The transport can be a conveyer belt or a drum. The salt water can be sea water.

According to a second embodiment of the present invention, an apparatus for desalinating salt water with solar energy is disclosed. The apparatus includes a transport for receiving a thin film of salt water, an evaporator for evaporating the salt water contained in at least a portion of the thin film by directing a concentrated sunlight beam at the portion of the thin film or a portion of the transport, and a vapor hood positioned above and spaced apart from the transport for collecting the evaporated fresh water. The salt water of the portion of the thin film is evaporated to produce evaporated fresh water. The evaporated fresh water is condensed to provide potable water.

In certain implementations of the second embodiment, the evaporator can include a means for collecting and reflecting a plurality of sunlight beams, a means for collecting and focusing the plurality of collected sunlight beams to produce a focused sunlight beam and for reflecting the focused sunlight beam, a means for collecting and concentrating the focused sunlight beam to produce a concentrated and focused sunlight beam and for reflecting the concentrated and focused sunlight beam, and a means for collecting and shaping the concentrated and focused sunlight beam to produce a concentrated and shaped sunlight beam and for directing the concentrated and shaped sunlight beam at the portion of the thin film or a portion of the transport.

Each of the plurality of solar collectors can include a solar collector backing plate and one or more mirrors secured to the solar collector backing plate.

The one or more mirrors can be constructed of a single, substantially flat mirror.

Alternatively, the one or more mirrors can be constructed of a plurality of substantially flat mirrors arranged to form a substantially planar surface when secured to the solar collector backing plate. Moreover, the one or more mirrors is treated with an anti-oxidant coating material.

The second embodiment can further include a means for recovering minerals produced as a by-product of the evaporation step. The first embodiment can also include a vapor condenser that is connected to the vapor hood, and condenses the evaporated fresh water. Moreover, the apparatus of the first embodiment can include a means for generating electricity for converting the evaporated fresh water into electricity. The transport can be a conveyer belt or a drum. The salt water can be sea water.

According to a third embodiment of the present invention, an apparatus for desalinating salt water with solar energy is disclosed. The apparatus includes a transport for receiving a thin film of salt water, an evaporator for evaporating the salt water contained in at least a portion of the thin film by directing a concentrated sunlight beam at the portion of the thin film or a portion of the transport, and a vapor hood positioned above and spaced apart from the transport

for collecting the evaporated fresh water. The evaporator can include a plurality of solar collectors, an at least one focusing mirror, an at least one solar concentrator, and an at least one beam shaping mirror. The plurality of solar collectors reflect a plurality of sunlight beams to the at least one focusing mirror. The at least one focusing mirror reflects a focused sunlight beam to the at least one solar concentrator. The at least one solar concentrator concentrates the focused sunlight beam to produce concentrated sunlight and directs the concentrated sunlight to the at least one beam shaping mirror, which shapes the concentrated sunlight to produce a concentrated sunlight beam for directing to the portion of the thin film of sea water or a portion of the transport. The salt water of the portion of the thin film is evaporated to produce evaporated fresh water. The evaporated fresh water is condensed to provide potable water.

These and other embodiments of the present invention will be more clearly understood and appreciated from a review of the following detailed description of embodiments, independent claims, and by reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily apparent from the following detailed description, particularly when considered in conjunction with the following drawings: Figure 1 schematically illustrates the overall system of solar powered desalination of the present invention; Figure 2 schematically illustrates a top view of a plurality of solar collectors configured in a grid configuration for collecting sunlight in accordance with one embodiment of the present invention; and

Figure 3 schematically illustrates a top view of a plurality of grid configurations for collecting sunlight in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figure is not necessarily to scale, some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.

Accordingly, one embodiment of the invention is a solar-powered desalination system. Fig. 1 illustrates a plurality of solar collectors 10 for collecting sunlight 12 generated by sun 14. In other embodiments, one solar collector may be suitable for practicing the present invention. In certain embodiments, each solar collector 10 includes a solar backing plate and a reflective surface. The solar backing plate can be constructed of a metal alloy, ceramic or polymer material. The reflective surface functions to collect sunlight 12. The reflective surface can be deposited on the solar backing plate through a process of vapor deposition or can be a piece of polished metal. Alternatively, the reflective surface can be a mirror or mirrors that are secured to the backing plate using, for example, fasteners joining the perimeters of the mirror (single mirror configuration) and backing plate or a self-adhesive backing (single or multiple mirror configuration). It should be understood that the mirrors themselves can be constructed by using a vapor deposition process. The reflective surface can be treated with an anti-oxidant coating material that maintains the bright surface of the solar collector and inhibits oxidation. VitriSeal, Inc. of Commerce Township, Michigan offers an anti-oxidant

coating that is suitable for use in the present invention. The anti-oxidant coating is sold under the trade name VitriSeal (TM). VitriSeal (TM) can be applied to the reflective surface via dipping the surface into an aqueous alkali silicate to electrophoretically coat the reflective surface. In certain embodiments, the reflective surface is substantially flat so that the collected sunlight can be directed at focusing mirror 16. However, it is also envisioned that the reflective surface of each solar collector 12 can be parabolic to account for natural dispersion by providing a converging element.

According to this embodiment of the present invention, sunlight 12 is collected on a substantially flat reflective surface of each solar collector 10, which, in turn, directs the collected sunlight to an at least one focusing mirror 16.

The focusing mirror can have a parabolic shape. The reflective surface of the focusing mirror can be constructed of a single or multi-piece parabolic mirror that is secured to a focusing mirror backing plate. In a certain embodiment, a fly-eye surface with hexagonal plates can be used for constructing a multi-piece parabolic mirror. The hexagonal plates can be secured to the backing plate in order to form a parabolic surface. Advantageously, the hexagonal plates can be less expensive to manufacture and transport than the single-piece parabolic mirrors. However, the single-piece parabolic mirror may be more suitable for certain applications.

Focusing mirror 16 focuses the collected sunlight and reflects it to solar concentrator 17. The solar concentrator can have a parabolic shape constructed of a single or multi-piece parabolic mirror as discussed in detail above. Accordingly, solar concentrator 17 reflects the focused, concentrated sunlight onto beam shaping mirror 20 to produce a focused, concentrated and shaped beam of sunlight 22, otherwise referred to as a concentrated sunlight beam.

U. S. Patent No. 5,005, 958 ("the'958 patent") entitled"High Flux Solar Energy Transformation", which is incorporated herein by reference, discloses an example of a system utilizing a primary focusing mirror and a secondary solar concentrator. One of the systems disclosed in the'958 patent employs a focusing mirror as a primary concentrative device and a non-imaging concentrator as a secondary concentrative device with concentrative capabilities of primary and

secondary stages selected to provide for net solar flux intensification of greater than 2,000 or 95% of the concentration area.

Fig. 2 schematically illustrates a top view of a plurality of solar collectors 24 configured in grid configuration 26 for collecting sunlight in accordance with another embodiment of the present invention. Sun 28 produces sunlight (not shown for the sake of clarity) that is collected by the plurality of solar collectors 24, which, in turn, reflects the sunlight to focusing mirror 30. In certain embodiments, focusing mirror is mounted about 80 feet to about 100 feet above the ground, and in other embodiments about 90 feet above the ground. The mounting for the focusing mirror can be constructed of a variety of materials, including, but not limited to, a wooden post or metal girder. In certain embodiments, the first row of solar collectors 32 is between about 30 feet to about 40 feet away from the base of the focusing mirror mounting and the last row of solar collectors 34 is between about 220 feet and about 240 feet away from the base of the focusing mirror.

Focusing mirror 30 directs a sunlight collected from the plurality of solar collectors 24 to solar concentrator 36, which, in turn, directs the focused, concentrated sunlight to beam shaping mirror 38. Beam shaping mirror 38 is situated above and spaced apart from transport 40, which are discussed in more detail below.

According to yet another embodiment of the present invention, Fig.

3 schematically illustrates a top view of a plurality of grid configurations 42 for collecting sunlight. Although three spaced apart grid configurations 42 are depicted in Fig. 3, it should be understood that other grid configurations can be used based on the terrain of the solar collector site. In certain embodiments, grid configurations of six or thirteen placed to form a shape similar to the three grid configuration have been found suitable. However, it should be understood that other numbers of grids, as well as partial grids, can be utilized in accordance with the present invention.

With respect to Fig. 3, each grid configuration collects sunlight 44 from sun 46 and directs it at one of the plurality of focusing mirrors 48. Each focusing mirror 48 focuses and directs the collected sunlight to solar concentrator

50, as represented by arrows 52. In turn, solar concentrator 50 directs the focused and concentrated sunlight to beam shaping mirror 53, as represented by arrow 54.

Beam shaping mirror 53 is situated above and spaced apart from transport 56, which are discussed in more detail below.

Shifting focus back to the embodiment depicted in Fig. 1, a thin film 58 of sea water 60 is provided over a transport. According to Fig. 1, the transport utilized is conveyor belt 62, although a drum may also be utilized according to particular embodiments. Sea water 60 can be drawn from reservoir 64 and distributed onto conveyer belt 58 through piping system 66. It is understood that sea water 60 can be drawn directly from a body of sea water. The focused, concentrated, and shaped beam of sunlight 22 can be applied to the thin film 58 of sea water 60, evaporating sea water contained in the thin film 58. The evaporated fresh water 68 can be collected in vapor hood 70 and condensed by vapor condenser 72, which can be connected to vapor hood 70. Condensed potable water 74 can be collected in pool retention unit 76. The process of the present invention generates an economical, continuous supply of potable water during daylight hours.

The desalination process of the present invention also generates a supply of minerals. After evaporation of thin film 58 of sea water 60, minerals 78 remain on conveyer belt 58 or drum. Minerals 78 continue to travel down conveyer belt 58 or drum. Conveyor belt 58 or, in certain embodiments, a drum, can be cleaned by cleaning unit 80, which can be a scrubber, for example. Once cleaned, minerals 78 drop onto secondary conveyer belt 82 for further processing.

The desalination process of the present invention also provides a source of electricity via a means for generating electricity. The flow of condensed fresh water 74 can be regulated to a turbine for the production of electricity.

Moreover, evaporated fresh water 68, as a source of steam, can be regulated for the production of electricity. Depending on the application of the present invention, a power generator offered by Siemens AG of Germany can be used to generate electricity. Siemens AG offers a wide selection of electricity production systems, including, but not limited to, high-pressure turbines, intermediate-pressure turbines,

low pressure turbines, combined high pressure/intermediate pressure turbines, combined intermediate-pressure/low-pressure turbines, and compact intermediate- pressure turbines for supplying power in the range of about 1 to 1200 MW depending on the type of turbine.

While embodiments of this invention have been illustrated and described, it is not intended that these embodiments illustrate or describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.