FIELD OF INVENTIONThe present field of invention generally relates to extraction of atmospheric water. More particularly, it relates to a system and a method for obtaining potable water from extracting atmospheric water.
BACKGROUNDThe earth consists mainly of water and water exists on the earth's surface, in aquifers in the soil as groundwater, and in the atmosphere as water vapour. Of all the water on earth, only less than 3 percent is fresh water. However, as majority of fresh water is trapped in ice caps, glaciers and aquifers, only less than 1 percent of the water supply on earth is portable and available for drinking purposes.
In recent years, global concerns regarding insufficient fresh water sources have increased greatly. Currently, sources of fresh water include water provided by lakes, rivers, and artesian wells. Unfortunately, these fresh water sources are not sustainable because of decline both in capacity and purity at alarming rates due to expansion of deserts. Furthermore, factors such as climate changes, environmental pollution, as well as population growth further threaten existing fresh water sources.
Besides having insufficient fresh water sources, there are also problems associated with provision of potable water. The provision of potable water is a serious problem in areas where rainfall is scarce, seasonal, or where there are relatively small water catchment areas and little natural local water storage. Additionally, as fresh water sources are not evenly distributed globally, some geographical locations do not have ready access to fresh water. Constructing reservoirs and water desalination plants usually alleviates this problem. However, many countries are unable to afford water desalination plants due to the relatively high capital investment and operational costs required.
Another problem associated with the provision of potable water relates to the setting up and maintenance of potable water distribution networks, such as water piping networks, which require significant efforts and resources. Further, water piping networks have limited lifespan and are frequently associated with water leakage and contamination problems. Water piping networks typically use water pipes made from metal ducts, concrete ducts or polyvinyl chloride (PVC) pipes. Metal and concrete ducts are vulnerable to corrosion by inorganic acid and alkaline contaminants, whereas organic solvents present in soil and building materials can be absorbed by and permeated through PVC pipes.
One way to overcome the aforementioned problems is by extracting water from the atmosphere. Approximately 577,000 km3of water evaporates into the atmosphere from water bodies, such as seas and rivers, and the earth's surface each year, with air remaining close to the earth's surface containing the greatest percentage of water. Commercial water production systems capable of extracting atmospheric water have made it possible to supply potable water without the need for tapping on a central water source via complex water distribution networks. Such water production systems are therefore an attractive alternative to conventional ways of deriving and distributing potable water.
In principle, these commercial water production systems collect water droplets formed by condensation of water vapour present in the atmosphere on cold surfaces cooled by refrigeration means. The working principle is similar to the disclosure in patents filed to Ehrlich in 1978 (U.S. Pat. No. 4,255,937), Reidy (U.S. Pat. No. 5,106,512, U.S. Pat. No. 5,149,446, U.S. Pat. No. 5,203,989) and Morgen et al. in 2002 (U.S. Pat. No. 6,931,756B2). With the advent of more efficient refrigeration techniques, the cost of electricity needed for extracting an amount of water from the atmosphere can be lower than the price of a bottled water of equivalent volume, or that of the utility charge of obtaining an equivalent volume of water from the tap with the additional cost for boiling or purifying water using mechanical and chemical filtering means.
However, the cost of hardware of a commercial water production system comprising compressor, condenser, evaporator and filtration means remains relatively high leading to unattractive return of investment. Additionally, for climates with low ambient temperature levels or where temperature fluctuates significantly, atmospheric water extraction becomes difficult. Typically, these commercial water production systems for water vapour extraction operate above 20° C. and above a relative humidity of 35%.
U.S. Pat. No. 3,675,442 to Swanson discloses an atmospheric water collector, which employs a cooling coil immersed in a fresh water bath that cools the bath. The cooled water is pumped through a conduit and condensing frame. Water vapour present in winds that pass over the condensing frame is condensed and drained into a collector. However, the cooled water is periodically mixed with the condensed water subjecting the condensed water to contamination.
U.S. Pat. No. 5,056,593 to Hull discloses, in several variations, the use of electrostatic and magnetic fields to substantially enhance water product extraction yields in a dehumidifying heat exchanger apparatus. Liquid water droplets are electrostatically collected on grounded or charged heat transfer tubes in the heat exchanger apparatus. In one variation, charged or grounded horizontally-declined heat transfer tubes with attached drainage wicks attract liquid droplets and accelerate condensing heat transfer by continuous absorption and transfer of condensate. The use of drainage wicks to absorb and confine condensate collected on the surfaces of the heat transfer tubes may result in the loss of water extracted and advance the growth of fungi and bacteria on the drainage wicks. Additionally, the heat exchanger apparatus may be electrically unsafe with charged electrode wires entrenched between the tubes of the heat exchange unit.
U.S. Pat. No. 7,000,410 to Hutchinson discloses a device that utilizes a condenser type refrigerant system with multiple fans and two air chambers to produce water from the air. The apparatus further deploys a stainless steel ioniser to charge the ambient air to maximise extraction of moisture from the air. The two air chambers operate in tandem to mix desiccated ionised air that exited from the evaporator plates with fresh incoming air drawn through a compressor, a condenser and the ioniser. This causes partial drying of the newly formed condensation, which results in loss of condensation leading to reduced output and efficiency.
JP Pat. No. 02,172,587 to Katsumi and U.S. Pat. No. 5,435,151 to Han disclose water making apparatus for use on vehicles. U.S. Pat. App. No. 20040040322 filed by Engel et al. discloses a similar water extraction device for vehicles, together with some applications including central air system and mobile unit. All the disclosed devices tap on existing or external air conditioning systems to simplify system design and lower device cost. However, conventional designs fail to function properly in many temperate areas where ambient temperature drops below 20° C. during the night or during cold spells and storms. This problem accentuates for water extraction devices installed on vessels and ships, on caravans and emergency vehicles.
Therefore, there is a need for a system and a method for obtaining potable water from extracting atmospheric water, which at least addresses one of the aforementioned disadvantages.
SUMMARYThe present embodiment of the invention disclosed herein provides an atmospheric water extraction system and a method for extracting atmospheric water for obtaining potable water.
In accordance with a first aspect of the invention, there is disclosed an atmospheric water extraction system comprising a passage, a cooling unit and an ioniser. The passage comprises a condenser portion and a cooling portion inter-configured for cyclical passage of fluid therethrough. The cooling unit is in thermal communication with the cooling portion and is for extracting heat from liquid passaging through the cooling portion to thereby cool the liquid, in which the liquid is transportable to the condenser portion subsequent to passaging through the cooling portion. The ioniser is for ionising ambient air into ionised air, in which the ionised air is charged for enhancing adhesion of water vapour thereto. The ionised air is transportable for thermal interaction with the condenser portion of the passage for condensing the water vapour into water droplets, and the liquid passaging through the condenser portion receives heat from the ionised air during thermal interaction of the ionised air with the condenser portion. The liquid is then transportable to the cooling portion of the passage for re-cooling thereby subsequent to passaging through the condenser portion.
In accordance with a second aspect of the invention, there is disclosed an atmospheric water extraction method. The method comprises providing a passage having a condenser portion and a cooling portion inter-configured for cyclical passage of fluid therethrough. The method also comprises extracting heat from liquid passaging through a cooling portion to thereby cool the liquid using a cooling unit, whereby the cooling unit is in thermal communication with the cooling portion. The liquid is then transportable to the condenser portion subsequent to passaging through the cooling portion. The method further comprises ionising ambient air into ionised air using an ioniser, in which the ionised air is charged for enhancing adhesion of water vapour thereto. The ionised air is transportable for thermal interaction with the condenser portion of the passage for condensing the water vapour into water droplets, and the liquid passaging through the condenser receives heat from the ionised air during thermal interaction of the ionised air with the condenser portion. The liquid is then transportable to the cooling portion of the passage for re-cooling thereby subsequent to passaging through the condenser portion.
In accordance with a third aspect of the invention, there is disclosed an atmospheric water extraction system comprising an ioniser and a condenser portion. The ioniser ionises ambient air for obtaining ionised air therefrom, in which the ionised air is charged for enhancing adhesion of water vapour thereto. The condenser portion is disposed alongside the ioniser for condensing water vapour in the ionised air into water droplets.
BRIEF DESCRIPTION OF THE DRAWINGSAn embodiment of the invention is described hereinafter with reference to the following drawings, in which:
FIG. 1 shows a partial schematic diagram of an atmospheric water extraction system according to an embodiment of the invention; and
FIG. 2 shows an operational flow of the atmospheric water extraction system ofFIG. 1.
DETAILED DESCRIPTIONAn atmospheric water extraction system and a method for extracting atmospheric water are described hereinafter for addressing at least one of the aforementioned disadvantages.
For purposes of brevity and clarity, the description of the invention is limited hereinafter to applications relating to atmospheric water extraction. This however does not preclude various embodiments of the invention from other applications. The fundamental inventive principles of the embodiments of the invention shall remain common throughout the various embodiments.
An embodiment of the invention described in the detailed description provided hereinafter is in accordance withFIG. 1 andFIG. 2 of the drawings, in which like elements are numbered with like reference numerals.
With reference toFIG. 1, an atmospheric water extraction system100 (hereinafter known as system100) for extracting atmospheric water is described according to an embodiment of the invention. Thesystem100 generally comprises anextraction unit110, apassage111, awater collection unit112 and acooling unit113.
Theextraction unit110 is for extracting water vapour in ambient air and theextraction unit110 has anintake114 and anexhaust116 formed therein for allowing flow of the ambient air therethrough. Theextraction unit110 comprises anioniser118 and acondenser portion120, in which thecondenser portion120 is disposed alongside theioniser118. Theextraction unit110 further comprises anair filter122, aventilator124 and awater collection tray126.
Theioniser118 is for ionising the ambient air into ionised air. When theioniser118 ionises the ambient air, air particles present in the ambient air become positively or negatively charged, although negative charging is preferable in most uses. The charged air particles (ionised air) enhance adhesion of water vapour thereto for extracting atmospheric water over varying ambient temperatures and humidity. Due to the polar nature of water, each water molecule has an electric dipole moment. The oxygen atom in each water molecule has a partial negative charge while each hydrogen atom in each water molecule has a partial positive charge. As such, the difference in charge causes water molecules to be attracted to each other and to other polar molecules. Since the ionised air comprises charged particles, adhesion of water vapour thereto is enhanced due to the partial negative and positive charges present on water molecules. Theioniser118 is also for sterilising the ambient air and for inhibiting growth of fungi and bacteria when thesystem100 is in use.
Thecondenser portion120 is for condensing water vapour in the ionised air to obtain water droplets. The ionised air is transportable for thermal interaction with thecondenser portion120 for condensation of water vapour to take place. Condensation of water vapour occurs when a surface is colder than the dew point temperature (condensation threshold temperature) of the air surrounding the surface. At this temperature, the air has a relative humidity of equivalent to 100 percent and the air becomes saturated with water. The dew point temperature of the air is dependent on both air temperature and humidity. Therefore, surfaces of thecondenser portion120 over which the ionised air flows must have a temperature that is lower than the dew point of the ionised air.
Thepassage111 is inter-configured for cyclical passage of fluid therethrough. Thepassage111 comprises a firstfluid channel128 and a secondfluid channel130 for interconnecting theextraction unit110 and thecooling unit113. The firstfluid channel128 is for receiving liquid from thecooling unit113 and a secondfluid channel130 for returning the liquid to thecooling unit113. Thecooling unit113 is in thermal communication with a coolingportion132 for extracting heat from the liquid passaging through the coolingportion132 to thereby cool the liquid. The liquid is then transportable to thecondenser portion120 subsequent to passaging through the coolingportion132 for cooling the surfaces of thecondenser portion120 to a temperature that is lower than the dew point temperature of the air surrounding the surfaces for condensation of water vapour to occur. The surfaces of thecondenser portion120 can be made of any material of which water vapour condensation can occur in response to cooling of the material in a given environment. For instance, the material can comprise of metal, glass, plastic, or the like.
Additionally, the surfaces of thecondenser portion120 are film-coated with food-grade materials, such as, gold, tin, Teflon or the like in compliance with public health requirements governing use of materials in contact with drinking water. The surfaces of thecondenser portion120 are preferably plated with gold or any material of which enhances the rate of heat transfer. Thecondenser portion120 is preferably designed for optimising air circulation, velocity and distribution of air on the surfaces for achieving an optimal rate of water vapour extraction.
Thecooling unit113 comprises adrive assembly136 for displacing the liquid from thecooling unit113 to thecondenser portion120 via the firstfluid channel128. Thedrive assembly136 comprises anactuator valve138 and afluid pump140. Thefluid pump140 is one of a centrifugal pump and a displacement pump. Further, thecooling unit113 is couplable to an external cooling source (not shown) for extracting heat from the liquid to cool liquid. The external cooling source can comprise a refrigerant, such as Freon, for extracting heat from the liquid. As such, instead of relying on the coolingportion132 for extracting heat from the liquid, thecooling unit113 can tap on the external cooling source for cooling the liquid. The liquid is one of water and alcohol, or the like. Thecooling unit113 further comprises atemperature measurement device142 for measuring the temperature of the liquid passing therethrough. The temperature of the liquid is preferably in the range of 5° C. to 15° C.
Prior to ionisation of the ambient air by theioniser118, the ambient air is passed through theair filter122 of theextraction unit110. Theair filter122 is for filtering the ambient air and is disposed in the vicinity of theioniser118. Theair filter122 can also be disposed in theintake114 or in the vicinity of theintake114. Furthermore, theair filter122 is replaceable and therefore can be replaced when necessary.
Theventilator124, on the other hand, is disposed in the vicinity of thecondenser portion120 and is for displacing and directing the ambient air into theextraction unit110. Theventilator124 is preferably a form or the like impeller-based air mover controllable to vary flow rate of the ambient air. By varying the flow rate of the ambient air, convecting air currents necessary for obtaining sufficient water vapour condensation on the surfaces of thecondenser portion120 is generatable. Theventilator124 can also be disposed at or adjacent theexhaust116. Theair filter122 and theventilator124 are orientable or disposed as readily recognised by those skilled in the art to achieve effectively clean or dust-controlled airflow or circulation inside theextraction unit110.
Thewater collection tray126 of theextraction unit110 is for receiving the water droplets from thecondenser portion120. Thewater collection tray126 is disposed in theextraction unit110 such that the water droplets received are directed to thewater collection unit112. Thewater collection unit112 of thesystem100 comprises awater collection tank144, adrive assembly146 and awater purifier148.
Thewater collection tank144 is for receiving the water droplets from thewater collection tray126. Thewater collection tank144 preferably comprises a sediment filter (not shown) for filtering the water droplets received. Thewater collection tank144 further comprises a waterlevel measurement device150 for measuring the water level present in thewater collection tank144 and awater purifier152 for purifying the water droplets received. The waterlevel measurement device150 is an optical or a float switch type while thewater purifier152 preferably comprises an ultra-violet light or an ozone generator. Further, thewater purifier152 may incorporate other filtration means including any mechanical, chemical or biological filtering systems suitable for purifying water for drinking purposes.
Thedrive assembly146 is for transporting water collected in thewater collection tank144 to thewater purifier148 of thewater collection unit112. Thedrive assembly146 is one of a fluid pump, a centrifugal pump and a displacement pump. Thedrive assembly146 provides additional gravitational pressure to extract the water collected out of thewater collection tank144 and displace the water through thewater purifier148. Thewater purifier148 comprises any suitable device capable of sterilising water, for instance, suitable chemical means, heating elements, ultra-violet radiation emitters, or the like. The water after passing through thewater purifier148 is suitable for drinking and can be transported through afluid duct153 to external appliances or any storage.
Thesystem100 further comprises atemperature measurement device154 for measuring ambient air temperature and a relativehumidity measurement device156 for measuring relative humidity of the ambient air. Additionally, thesystem100 further comprises acontroller158 for controlling thesystem100. Thecontroller158 is couplable to a signalling interface module for relaying any control signals for operating any electrically driven parts and components of thesystem100 that require instructions, signalling and/or electricity supply.
Thecontroller158 preferably comprises a microprocessor (not shown) for storing and executing software applications or embedded codes capable of generating appropriate control signals in accordance with a set of pre-programmed instructions. Measured data is further processable in thecontroller158 in which the processes include logging, reading and writing, storing and backing-up, analysing and displaying of measured and/or control data. Further, thecontroller158 is coupled to external computing equipment via a wired or wireless data exchange interface (not shown). Finally, electrical power supplied to thecontroller158 and thesystem100 may be single-phase or multi-phase alternating current tapped from power grids or mobile electricity generators such as those used on vessels, cruises, caravans, oil rigs, construction sites and other similar facilities. Alternatively, electrical power can be supplied as direct current.
FIG. 2 illustrates theoperational flow200 of thesystem100. Upon supplying electrical power to thesystem100, in astep210, thecontroller158 activates theioniser118 and theventilator124. Further, thecontroller158 samples data measured by thetemperature measurement device142 of thecooling unit113, the waterlevel measurement device150, thetemperature measurement device154 of thesystem100 and the relativehumidity measurement device156 at a predetermined regular interval to obtain measured data therefrom. Thecontroller158 then analyses the measured data and determines the mode of operation, and may display the measured data for visual monitoring by an operator of thesystem100 in astep212.
Next in astep214, thecontroller158 retrieves the required controls according to the mode of operation that is determined in thestep212. Further, in a step216, thecontroller158 looks up required controls for required parts of thesystem100 based on the measured data. Finally, in astep218, corresponding control signals provided by thesteps214 and216 are sent to the corresponding elements of thesystem100.
An example of operating thesystem100 is provided hereinafter.
Thecontroller158 selects a first mode of operation denoted as a NORMAL mode when (a) the ambient temperature measured by thetemperature measurement device154 is greater than a first predetermined threshold TLA01, (b) the ambient relative humidity measured by the relativehumidity measurement device156 is greater than a first predetermined level RHL01, (c) the temperature of the liquid from the coolingportion132 measured by thetemperature measurement device142 is lower than a predetermined threshold of TLCHI, (d) the water level in thewater collection tank144 detected by the waterlevel measurement device150 does not exceed a predetermined level WLCHI, and (e) if an external water storage tank is present (coupled to the system100) and the external water storage tank does not indicate FULL state (not shown).
If the above conditions are met, thecontroller158 opens theactuator valve138 to allow the liquid from the coolingportion132 to flow into the firstfluid channel128. Further, thecontroller158 activates thefluid pump140 to convey the liquid to thecondenser portion120 via the firstfluid channel128. The liquid is then circulated from thecondenser portion120 back to the coolingportion132 by means of the secondfluid channel130. The liquid passaging through thecondenser portion120 receives heat from the ionised air during thermal interaction of the ionised air with thecondenser portion120. The liquid is then transportable to the coolingportion132 of thepassage111 for re-cooling thereby subsequent to passaging through thecondenser portion120. The liquid passaging through thepassage111 is substantially isobaric.
Excessive airflow generated by theventilator124 may hamper the extraction of water vapour from the ambient air. As such, the speed of the airflow generated by theventilator124 should preferably be controlled at a predetermined optimised rate. Thecontroller158 can control theventilator124 and thecontroller158 attains a predetermined airflow by adjusting fan speed of theventilator124. In the first mode of operation, thecontroller158 sets the fan speed of theventilator124 to low or medium. The ambient air is then controllably induced into thesystem100 by theventilator124. The incoming air first passes through theair filter122 followed by an ionising field created by theioniser118. The ionised air then passes through thecondenser portion120 and surrounds the surfaces of thecondenser portion120 in which condensation of water vapour takes place. The water droplets obtained after condensation drips onto thewater collection tray126 and are directed into thewater collection tank144. The waterlevel measurement device150 measures the water level present in thewater collection tank144 to detect predetermined high (WLCHI) and low (WLCLO) water levels.
During the NORMAL mode and when the water level detected by the waterlevel measurement device150 exceeds a predetermined level low (WLCLO) level, thewater purifier152 in thewater collection tank144 is activated by thecontroller158 on either a continuous or regular basis with thewater purifier152 being periodically activated for a first duration of WPUON1and deactivated for a second duration of WPUOFF1. When the water level measured by the waterlevel measurement device150 detects a predetermined high (WLCHI) level, and if the external water storage tank is present and the external water storage tank does not indicate the FULL state, thecontroller158 activates thedrive assembly146 to transfer the water from thewater collection tank144 through thewater purifier148 of thewater collection unit112. Thecontroller158 can activate thewater purifier148 on either a continuous or regular basis.
Thecontroller158 selects a second mode of operation denoted as a COLD mode when (a) the ambient temperature measured by thetemperature measurement device154 falls between the first predetermined threshold TLA01and a second predetermined threshold TLA02, (b) the ambient relative humidity measured by the relativehumidity measurement device156 is equal to or greater than the predetermined level RHLLO, (c) the temperature of the liquid from the coolingportion132 measured by thetemperature measurement device142 equals to or lower than the predetermined threshold of TLCLO, (d) the water level in thewater collection tank144 detected by the waterlevel measurement device150 does not exceed the predetermined level WLCHI, and (e) if the external water storage tank is present (coupled to the system100) and the external water storage tank does not indicate FULL status (not shown).
If the above conditions are met, thecontroller158 operates thesystem100 through the same control and decision-making steps as performed for the NORMAL mode. The only exception is that the fan speed of theventilator124 is set to high for increasing the air circulation in the vicinity of thecondenser portion120, leading to higher water vapour condensation efficiency when the ambient air temperature is low.
Thecontroller158 selects a third mode of operation denoted as a SUSPEND mode when (a) the ambient temperature measured by thetemperature measurement device154 falls below the second predetermined threshold TLA02, or (b) the ambient relative humidity measured by the relativehumidity measurement device156 falls below a second predetermined level RHL02, or (c) the temperature of the liquid from the coolingportion132 measured by thetemperature measurement device142 is higher than a predetermined threshold of TLCHI, or (d) the water level in thewater collection tank144 detected by the waterlevel measurement device150 equals or exceeds the predetermined level WLCHI, or (e) if the external water storage tank is present (coupled to the system100) and the external water storage tank indicates FULL state (not shown).
If any of the above conditions is met, thecontroller158 stops all the steps required to extract water vapour. However, theioniser118 and theventilator124 can continue to operate controllably by thecontroller158. Thecontroller158 may also continue to monitor all measurement means if any. Further, should the water level in thewater collection tank144 is above WLCLO, thecontroller158 may continue to activate thewater purifier152 of thewater collection tank144 on a continuous or periodic basis.
Exemplary parameters that are preferably used in thesystem100 for extracting atmospheric water are as follows:
1) TLA01=25° C. and TLA02=15° C., as temperature threshold values used for classifying the modes of operation;
2) RHL01=50% and RHL02=25%, as relative humidity threshold values used for classifying the modes of operation;
3) TLCLO=5° C. and TLCHI=15° C., as temperature threshold values of the liquid being cooled by the coolingportion132 used for activation and deactivation of theactuator valve138 and driveassembly146; and
4) WPUON=30 seconds and WPUOFF1=45 minutes, for periodic activation and cut off durations of thewater purifier152 of thewater collection tank144.
Thesystem100 for extracting water vapour from the ambient air for obtaining potable water provides a solution to water harvesting without the need for extensive water distribution networks. Hence, thesystem100 is well suited for indoor, outdoor, fixed and mobile applications. Further, as thesystem100 is able to ride on external cooling sources such as existing refrigeration and central air system for extracting heat from the liquid for cooling the liquid, thesystem100 offers a cost-effective water making system with relatively low equipment, operational and maintenance costs.
Furthermore, thesystem100 is able to operate at an ambient air temperature of as low as 15° C., thus making thesystem100 well suited for many indoor and outdoor, fixed and mobile applications not only in tropical regions, but also in temperate areas with ambient air temperatures well below what conventional systems are designed to operate at.
In the foregoing manner, an atmospheric water extraction system and a method for extracting atmospheric water are described according to one embodiment of the invention for addressing at least one of the foregoing disadvantages. Although only one embodiment of the invention is disclosed, the invention is not to be limited to specific forms or arrangements of parts so described and it will be apparent to one skilled in the art in view of this disclosure that numerous changes and/or modification can be made without departing from the scope and spirit of the invention.