AU2008221567A1 - Atmospheric water generator having a zero carbon footprint - Google Patents

Description

P001 Section 29 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Atmospheric water generator having a zero carbon footprint The following statement is a full description of this invention, including the best method of performing it known to us: P111ABAUll207 0O 0 ATMOSPHERIC WATER GENERATOR SYSTEM HAVING A ZERO CARBON

FOOTPRINT

FIELD OF THE INVENTION The present invention relates to systems for condensing water from air.

BACKGROUND TO THE INVENTION Water is essential for all life on earth. Humans can survive for several weeks without food, but only a few days without water. Thus, a constant supply of water is needed to replenish the water used for all human activity, including Odrinking, washing, landscape and farm irrigation. While potable water is typically 00 more of a problem in third world countries, some industrialized countries have experienced multi-year droughts and thus are faced with a severe shortage of portable water. This problem is typically not insurmountable in most developed countries because seawater desalination is affordable in such economies.

However, in some industrialized countries the by-product of seawater desalination, namely a concentrated brine stream. This concentrated brine stream can be a serious detriment for several reasons. For one, it can find its way into an aquifer. For another, it can be harmful to aquatic life including coral reefs, which are often tourist attractions. Also, coral reefs and aquatic life usually represent an eco region unique to those countries. Consequently, seawater desalination it not considered an eco friendly option to overcome the water shortage in such countries.

A considerable amount of work is being done to recycle waste water from domestic and industrial sources. However, this is not sufficient to overcome the severe drought conditions prevailing in come countries. Severe water shortages have a dramatic effect on industries, such as farming and mining. Further, the groundwater in such countries is becoming ever more saline as droughts continue due to the huge demands on groundwater sources.

Some such countries, particularly Australia, are surrounded by ocean and therefore much of its air is humid. One of the possible ways of producing potable water is to condense this humidity from air. While this idea has been around for many years it has only proved to be feasible for military and emergency budgets. There needs to be substantial improvements in the technology to bring costs down for such technology to be viable for the production 00 O of portable water to large communities. It is also desirable to reduce the carbon C footprint for any system that removes water from air.

0 Condensing water from air is the reverse of evaporation, and a large amount of energy is consumed during both processes. The energy consumption of conventional systems has been the primary reason for lack of acceptance. In theory, the greatest source of potable water is rain and humidity. Condensing humidity from air, without nature's help, is a much more daunting task from an energy consumption point of view. The amount of water vapor in a given volume Nof air has a specific amount of energy, called enthalpy. This balance of vapor and 00 air has to be disturbed by artificially cooling the air to a point below its dew point.

In doing so, much energy has to be expended with low conversion to chilling of air.

Various approaches have been used to extract water from air. For example, one method of extracting water from air is to compress the air to the point where water vapor condenses to form liquid water. This method requires a substantial amount of energy and thus is not a viable solution for supplying large amounts of water to residential, agricultural and industrial users.

Another approach is disclosed in U.S. Patent No. 6,960,243 which teaches a method and apparatus for extracting water from air wherein a stream of air is contacted with a porous adsorbent material having a surface modifying agent adsorbed on the surface of the porous support. The surface modifying agent creates a hydrophilic surface for the adsorption of the water. After the water is adsorbed into the pores, the surface modifying agent is selectively desorbed from the surface. The water then evaporates from the pores and is collected in a condenser.

U.S. Patent No. 6,945,063 teaches an apparatus and method for harvesting atmospheric moisture. The apparatus includes two main parts, namely 1) one or more water vapor condensation and collection members each having a surface upon which water is condensed and collected, and 2) an energy gathering member such as a photovoltaic panel that produces electricity to power condensation-driving refrigeration.

U.S. Patent No. 7,043,934 teaches a method for collecting water from air by use of a device that collects the moisture contained in the atmosphere and 00 O condenses it into high purity water. Another type of apparatus and method for C removing water from air is taught in U.S. Patent No. 7,000,410 wherein air is Sdrawn through a particle ionizer grid, evaporator plate of a refrigerant system and recirculating the ionized air with ambient air and recycling the mixed air through a the ionizer and evaporator plates to extract moisture from the air.

Also, U.S. Patent No. 6,156,102 teaches a method and apparatus for Irecovering water form air using a liquid desiccant to first withdraw water from air and treatment of the liquid desiccant to product water and regenerate the 0desiccant.

00 While various technologies exist for removing water from air there is a great need for improved methods of removing water from air in more economical and eco friendly ways.

SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention there is provided a system for condensing potable water from air. The system includes: a) an absorption chiller containing an absorbent liquid and a refrigerant liquid, the absorption chiller including a generator section, an absorption section, a condenser section and an evaporator section; b) a heated fluid loop including an alternative energy source capable of heating a fluid contained within a conduit which conduit extends from said alternative energy source to within the generator section of said absorption chiller and back to said energy source; c) a cooling fluid loop including a cooling source and containing a closed loop conduit containing a fluid, which conduit extends from within the absorber section of the absorption chiller to the condenser section of the absorption chiller and then to a heat transfer zone capable of dissipating heat; d) a condenser including an enclosure having enclosing walls that enclose a closed loop conduit system containing a fluid and which conduit system extends from within the evaporator section of said absorption chiller through a first inlet port of an enclosing wall of said condenser and which traverses multiple times within said condenser and out of a first outlet port of an enclosing wall of said condenser and back to the evaporator section of said evaporator section, 00 O which condenser also contains a second inlet port and a second and third outlet Sport; 0 e) a blower in fluid communication with said second inlet port of said condenser, said blower capable of introducing a stream of atmospheric air into said enclosure; f) a photovoltaic panel in fluid communication with said second Ioutlet port of said condenser for providing a stream of cooled dry air from said outboard condenser to said photovoltaic panels; and

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N g) a vessel for collecting condensed water from said third outlet port.

In accordance with a second aspect of the present invention there is provided a method for condensing water vapor from the air, which method includes: a) providing an absorption chiller containing an absorbent liquid and a refrigerant liquid, the absorption chiller including a generator section, an absorption section, a condenser section and an evaporator section; b) providing an alternative energy source to heat a fluid used to drive the absorption chiller; c) conducting a stream of heated fluid to the generator section of said absorption chiller thereby causing the absorbent liquid to vaporize refrigerant that is passed to the condenser section of said absorption chiller wherein it condenses back to a liquid thereby releasing heat; d) passing the condensed refrigerant from said condenser section through an expansion valve where it vaporizes into the evaporator section of said absorption chiller thereby absorbing heat from a fluid within a conduit thereby cooling said fluid and causing a portion of the vaporized refrigerant to be passed to the absorption section and absorbed into said absorbent; e) conducting at least a portion of said absorbent having refrigerant dissolved therein from the absorption section to the generator section of said absorption chiller; f) providing a cooling loop including a cooling fluid within a conduit wherein the conduit extends from within the condenser section and within said absorber section of said absorption chiller wherein it removes heat from said 00 O condenser section and said absorber section and dissipates said heat in a heat N dissipation zone; a g) providing a chilled water loop including a cooling fluid within a conduit system; h) providing a condenser including an enclosure having enclosing walls and contained therein a portion of a said chilled water loop wherein the Nsurfaces of said conduit within said enclosure are at a temperature below the dew point of said air being conducted into said condenser;

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0 i) providing a blower that introduces atmospheric air into said enclosure which air comes into contact with said surfaces of said conduit thereby causing water vapor to condense thereon; j) collecting the condensed water vapor; and k) providing a photovoltaic panel system capable of providing electricity to operate electrical components of the overall system.

In a preferred embodiment the cooling loop is a geothermal heat pump system.

In another preferred embodiment the photovoltaic panel system is cooled by use of cool dry air from the condenser.

BRIEF DESCRIPTION OF THE FIGURE The figure hereof is a schematic diagram of a preferred embodiment of an atmospheric water generation system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an improved process for condensing water vapor from air. The amount of water in the atmosphere in humid locations that can be recovered is related to both the initial relative humidity and the temperature to which this warm, moisture-laden air can be cooled so that water condenses. Where relative humidity is high, considerable amounts of water are held in the air. Although it is preferred to use the system of the present invention at a location where the relative humidity is at least about 55% and the temperature at least about 65 0 F, the present invention can be practiced at drier geographic locations.

The present process chills a volume of air solely for the purpose of condensing water vapor therefrom and not for comfort purposes. Further, the air 00 O is chilled by use of an alternative energy source, thereby providing for a more C economical and eco friendly process. The process of the present invention a leaves no carbon footprint. Carbon footprint is taken to mean the total amount of CO2 and other greenhouse gases emitted over the full life cycle of a product or service. It is typically expressed as grams of CO2 equivalents. The use of solar energy (or any other renewable energy source) for heating water as an energy source to run the absorption chiller and the use of a photovoltaic panel to generate electricity to run electrical components of the present system ensure that the system is run in substantially zero carbon footprint mode. Excess chilled 00 air can be used to cool components of the system to either neutralize waste heat or to increase efficiency of the components.

The present system is designed to use an alternative energy source, preferably solar, to heat a fluid, preferably water, to run the absorption chiller of the present invention. Non-limiting examples of alternative energy sources, other than solar, include wind, geothermal, tides, hydroelectric, and biogas. By "biogas" we mean a fuel gas, such as a hydrogen-rich gas, or a C1 to C3 alkane stream, that is produced from a biomass feedstock. Absorption chillers are well known in the art and for purposes of this invention the absorption chiller may be a single effect or multiple effect chiller. Multiple-effect absorption chillers recycle a portion of the internal heat to provide part of the energy required in the generator section of the chiller to create the high-pressure refrigerant vapor. Absorption chillers are run by use of a thermo-chemical process, as opposed to more conventional motor or engine driven vapor compression chillers. Absorption chillers utilize two different fluids, a refrigerant and an absorbent. The high affinity of the refrigerant (water) for the absorbent (lithium bromide or ammonia) causes the refrigerant to boil at a lower temperature and pressure than it normally would and transfers heat from one section of the absorption chiller to another. An absorption chiller is typically comprised of four sections, an absorber section Absorb, a generator section Gen, a condenser section Cond, and an evaporator section Evap. A water/lithium bromide system is preferred. In an absorption chiller, refrigerant vapor from the evaporator section is absorbed by a solution absorbent/refrigerant mixture, in the absorber section. This solution mixture is then pumped to the generator section where the refrigerant re-vaporizes by use 00 O of heat, typically from a waste steam heat source, but an alternative energy Ssource for purposes of this invention. The refrigerant-depleted solution then 0 returns to the absorber section via a throttling device. Compared to mechanical chillers, absorption chillers have a relatively low coefficient of performance (COP chiller load/heat input). However, absorption chillers can substantially reduce operating costs when powered by low cost and/or low-grade waste heat.

The present invention is better understood with reference to the figure hereof. This figure shows an atmospheric water generator system comprised of an absorption chiller 1, a source of heated fluid, preferably water heated by an 00 alternative energy source 2, preferably solar panels, a condenser 3 for condensing water vapor from air, a blower 4 for introducing humid atmospheric air into condenser 3, photovoltaic panels 5 for providing electrical power for running electrical components such as pumps, blowers, fans and controls; and a cooling loop 6, preferably geothermal heat pump system. Condenser 3 can be of any suitable design wherein a cooled surface if provided onto which water vapor from the air condenses. Non-limiting examples of suitable condenser designs include shell and tube, tube sheets, and waterboxes. Preferred is the shell and tube design and for purposes of the figure hereof a coiled tube arrangement is shown although the tube arrangement can be a series of parallel straight tubes fluidly connected to each other.. The tubes will generally be made of a material that is a good thermal conductor, preferably stainless steel, cooper alloys such as brass or bronze, cupro nickel, or titanium. Stainless steel tubes are more preferred.

The atmospheric water generation system of the present invention is utilized by providing heat to the generator section of the absorption chiller 1 which heats the absorbent liquid, preferably lithium bromide. The heat is provided by circulating a hot fluid, preferably water, through heating loop 10 which circulates water in tubes back and forth from the energy source 2 and the generator section.

As previously mentioned, energy source 2 is an alterative (renewable) energy source, but a solar panel system is preferred. The heating fluid (water) will be heated to a temperature from about 80 0 C to about 105 0 C, preferably from about 0 C to about 1050C. The heated absorbent liquid flows to the absorber section of the absorption chiller where is mixes with a portion of the refrigerant (water) from the evaporator section and is pumped back into the generator section. The 00 O combined generator/absorber sections are referred to as the chemical 0 C compressor of the absorption chiller. Refrigerant is released in the generator a section and flows to the condenser section of the absorption chiller where heat is released. The released heat is removed from the absorption chiller in both the condenser section and the absorption section by cooling loop 6, which is preferably a geothermal heat pump system, where waste heat is dissipated Iunderground. The refrigerant of the condenser section of the absorption chiller is passed through an expansion valve (not shown) and into the evaporator section N where heat is absorbed from chilled water loop 12. This chilled water is circulated 00 through a suitable tube, or coil, arrangement from the evaporator section to condenser 3. Condenser 3, as previously mentioned can be of any suitable design as long as it provides a cool surface onto which water vapor from the air will condense. Air containing water vapor is conduced via line 14 from the atmosphere via blower 4 and into condenser 3 where it is comes into contact with the chilled surface 14 thereby condensing at least part of its water vapor content.

The condensed potable water stream is collected via line 16.

At least a portion of the resulting dry air is put to use by conducing it via line 18 to cool one or more sides of a photovoltaic panel 5 and then via line 20 to be used as residual cooling air for absorption chiller 1.

It will be understood that a heat pipe arrangement can be used in place of the geothermal heat pump system for cooling loop 6. Heat pipes in general are well known in the art and are generally a vacuum tight tubular device having an evaporator section and a condenser section. A typical heat pipe is comprised of a working fluid and a wick structure. Heat input vaporized the liquid working fluid inside the wick in the evaporator section. The vapor, carrying the latent heat of vaporization, flows towards the cooler condenser section and gives up its latent heat. The condensed liquid returns to the evaporator through the wick structure by capillary action. The phase change process and two-phase flow circulation continue as long as the temperature gradient between the evaporator and condenser sections is maintained.

If a heat pipe is used in the practice of the present invention it is preferred that the interior wall of the heat pipe contain a layer of carbon nanofiber material.

An effective amount of graphitic nanostructures, preferably graphitic nanofibers, 00 O are added. Non-limiting examples of preferred carbon nanostructures are those c selected from carbon nanotubes, carbon fibrils, and carbon nanofibers. Typically, CD the nanostructure will be substantially graphitic, and in the case of carbon nanofibers, the most preferred nanostructure, the interstices will be the distance between graphitic platelets will be about 0.335 nm. It is to be understood that the terms "carbon filaments", "carbon whiskers", "carbon nanofibers", and "carbon I fibrils", are sometimes used interchangeably by those having ordinary skill in the art.

C For purposes of the present invention, carbon fibrils, which themselves are oO sometimes referred to as carbon nanotubes, are of the type described in U.S.

c Pat. Nos. 4,663,230 and 5,165,909. Carbon fibrils are reported to be essentially cylindrical discrete structures characterized by a substantially constant diameter between about 3.5 nm and 70 nm, a length greater than about 5, preferably 100 times the diameter, an outer region of multiple essentially continuous layers of ordered carbon atoms having c-axis that are substantially perpendicular to the cylindrical axis of the fibril, and a distinct inner core region. Each of the layers and core are reported in the above patents to be disposed substantially concentrically about the cylindrical axis of the fibril. The carbon fibrils are catalytically grown by the thermal decomposition of a gaseous carbon-containing compound.

Carbon nanotubes, other than those that are sometimes also referred to as carbon fibrils, will typically be of the fullerene type. Such structures are described in an article by M. S. Dresselhaus et. al. entitled Fullerenes, on pages 2087-2092 in Journal of Materials Research., Vol 8, No. 8, August 1993, which article is incorporated herein by reference. Fullerenes are Cn cage molecules built from a collection of hexagonal and pentagonal faces. The C60 fullerenes are typically referred to as "buckminsterfullerenes" or simply "buckyballs". C60 -derived tubules can be defined, in simplest terms by bisecting a C60 molecule at the equator and joining the two resulting hemispheres with a cylindrical tube one monolayer thick and with the same diameter as C60. Carbon nanotubes can also be defined as substantially hollow structures comprised of substantially parallel graphite layers aligned at distances of about 0.335 nm to 0.67 nm from each other.

00 O The overall shape of the carbon nanofibers will be any suitable shape.

c Non-limiting examples of suitable shapes include straight, branched, twisted, a spiral, helical, coiled, and ribbon-like. It is to be understood that the graphite platelets may have various orientations. For example, they can be aligned parallel, perpendicular, or at an angle with respect to the longitudinal axis of the nanofiber. Further, the surface area of the carbon nanofibers can be increased by IDcareful activation with a suitable etching agent, such as carbon dioxide, steam, or the use of a selected catalyst, such as an alkali or alkaline-earth metal.

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0 In addition, the carbon nanofibers of the present invention have a unique oo set of properties, that includes: a nitrogen surface area from about 40 to 300 Sm2/g; (ii) an electrical resistivity of 0.4 ohmcm to 0.1 ohmecm; (iii) a crystallinity from about 95% to 100%; and (iv) a spacing between adjacent graphite sheets of 0.335 nm to about 1.1 nm, preferably from about 0.335 nm to about 0.67 nm, and more preferably from about 0.335 to about 0.40 nm.

The more preferred carbon nanofibers of this invention are those having graphite platelets that are substantially perpendicular to the longitudinal axis of the nanofiber and those wherein the graphite platelets are aligned substantially parallel to the longitudinal axis. U.S. Patent No. 6,537,515 to Catalytic Materials, LLC, which is incorporated herein by reference, teaches a method for producing a substantially crystalline graphite nanofiber comprised of graphite platelets that are aligned substantially perpendicular to the longitudinal axis of the nanofiber.

The most preferred carbon nanofibers having their graphite platelets aligned substantially parallel to the longitudinal axis are the non-cylindrical multifaceted tubular nanofibers. Such multi-faceted tubular nanofibers can be single or multi-walled, preferably multi-walled. By multi-walled we mean that the structure can be thought of a multi-faceted tube within a multi-faceted tube, etc.

The multi-faceted tubular carbon nanostructures of the present invention are distinguished from the so-called "fibrils" or cylindrical carbon nanostructures. The multi-faceted tubular nanofibers of the present invention can also be thought of as having a structure that resembles a multi-faceted pencil or Alan key. That is, a cross section of the multifaceted nanotube would represent a polygon. A single wall of the multifaceted nanotubes of the present invention can also be thought of 11 00 O as being a single sheet folded in such a way to resemble a multifaceted tubular Sstructure the folds being the corners.

e( a While the present invention has been described with respect to a specific embodiment, it will be appreciated that various modifications and changes could be made without departing from the scope of the invention.

"Comprises/comprising" and grammatical variations thereof when used in Sthis specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the 0presence or addition of one or more other features, integers, steps, components 00 or groups thereof.

Claims (11)

1. A system for condensing potable water from air, said system including: a) an absorption chiller containing an absorbent liquid and a refrigerant liquid, said absorption chiller including a generator section, an absorption section, a condenser section and an evaporator section; Db) a heated fluid loop including an alternative energy source capable of Sheating a fluid contained within a conduit which conduit extends from said N alternative energy source to within the generator section of said absorption chiller 00 Oand back to said energy source; S 10 c) a cooling fluid loop including a cooling source and containing a closed loop conduit containing a fluid, which conduit extends from within the absorber section of the absorption chiller to the condenser section of the absorption chiller and then to a heat transfer zone capable of dissipating heat; d) a condenser including an enclosure having enclosing walls that enclose a closed loop conduit system containing a fluid and which conduit system extends from within the evaporator section of said absorption chiller through a first inlet port of an enclosing wall of said condenser and which traverses multiple times within said condenser and out of a first outlet port of an enclosing wall of said condenser and back to the evaporator section of said evaporator section, which condenser also contains a second inlet port and a second and third outlet port; e) a blower in fluid communication with said second inlet port of said condenser, said blower capable of introducing a stream of atmospheric air into said enclosure; f) a photovoltaic panel in fluid communication with said second outlet port of said condenser for providing a stream of cooled dry air from said outboard condenser to said photovoltaic panels; and g) a vessel for collecting condensed water from said third outlet port.

2. The system of claim 1 wherein the refrigerant liquid of the absorption chiller is water. 00 S3. The system of claim 1 or 2 wherein the absorbent liquid of the absorption N chiller is selected from lithium bromide and ammonia.

4. The system of any one of claims 1 to 3 wherein the fluid of the heated fluid loop is water. S 5 5. The system of any one of claims 1 to 4 wherein the fluid of the heated fluid loop is heated to a temperature from about 80 0 C to about 105 0 C. 00 6. The system of any one of claims 1 to 5 wherein the condenser is of a shell and tube type.

7. The system of any one of claims 1 to 6 wherein the alternative energy source for the heated fluid loop is selected from the group consisting of solar, wind, geothermal, oceanic tides, hydroelectric, and biogas.

8. The system of claim 7 wherein the alternative energy source is solar.

9. A method for condensing water vapor from air, said method including: a) providing an absorption chiller containing an absorbent liquid and a refrigerant liquid, said absorption chiller including of a generator section, an absorption section, a condenser section and an evaporator section; b) providing an alternative energy source to heat a fluid used to drive the absorption chiller; c) conducting a stream of heated fluid to the generator section of said absorption chiller thereby causing the absorbent liquid to vaporize refrigerant that is passed to the condenser section of said absorption chiller wherein it condenses back to a liquid thereby releasing heat; d) passing the condensed refrigerant from said condenser section through an expansion valve where it vaporizes into the evaporator section of said absorption chiller thereby absorbing heat from a fluid within a conduit thereby cooling said fluid and causing a portion of the vaporized refrigerant to be passed to the absorption section and absorbed into said absorbent; 00 O e) conducting at least a portion of said absorbent having refrigerant N dissolved therein from the absorption section to the generator section of said 0 absorption chiller; f) providing a cooling loop including a cooling fluid within a conduit wherein the conduit extends from within the condenser section and within said absorber section of said absorption chiller wherein it removes heat from said Icondenser section and said absorber section and dissipates said heat in a heat dissipation zone; (N 0 g) providing a chilled water loop including a cooling fluid within a conduit system; h) providing a condenser including an enclosure having enclosing walls and contained therein a portion of a said chilled water loop wherein the surfaces of said conduit within said enclosure are at a temperature below the dew point of said air being conducted into said condenser; i) providing a blower that introduces atmospheric air into said enclosure which air comes into contact with said surfaces of said conduit thereby causing water vapor to condense thereon; j) collecting the condensed water vapor; and k) providing a photovoltaic panel system capable of providing electricity to operate electrical components of the overall system. The method of claim 9 wherein the refrigerant liquid of the absorption chiller is water.

11. The method of claim 9 or 10 wherein the absorbent liquid of the absorption chiller is selected from lithium bromide and ammonia.

12. The method of any one of claims 9 to 11 wherein the fluid of the heated fluid loop is water.

13. The method of any one of claims 9 to 12 wherein the fluid of the heated fluid loop is heated to a temperature from about 800C to about 1050C. 00 O 14. The method of any one of claims 9 to 13 wherein the condenser is of a c shell and tube type. e( The method of any one of claims 9 to 14 wherein the alternative energy source for the heated fluid loop is selected from the group consisting of solar, wind, geothermal, oceanic tides, hydroelectric, and biogas. NO kn

16. The method of claim 15 wherein the alternative energy source is solar. 0 17. A system for condensing potable water from air substantially as herein described with reference to the embodiment illustrated in the accompanying drawing.

18. A method for condensing water vapour from air substantially as herein described with reference to the embodiment illustrated in the accompanying drawing. RG GLOBAL LIFESTYLES, INC. WATERMARK PATENT TRADE MARK ATTORNEYS