Abstrict The present invention provides a method and apparatus for extracting
liquid water from moist air using minimal energy input. The method
can be considered as four phases: (1) adsorbing water from air into
a desiccant, (2) isolating the water-laden desiccant from the air
source, (3) desorbing water as vapor from the desiccant into a chamber,
and (4) isolating the desiccant from the chamber, and compressing
the vapor in the chamber to form liquid condensate. The liquid condensate
can be removed for use. Careful design of the dead volumes and pressure
balances can minimize the energy required. The dried air can be
exchanged for fresh moist air and the process repeated. An apparatus
comprises a first chamber in fluid communication with a desiccant,
and having ports to intake moist air and exhaust dried air. The
apparatus also comprises a second chamber in fluid communication
with the desiccant. The second chamber allows variable internal
pressure, and has a port for removal of liquid condensate. Each
chamber can be configured to be isolated or in communication with
the desiccant. The first chamber can be configured to be isolated
or in communication with a course of moist air. Various arrangements
of valves, pistons, and chambers are described.
Claims We claim:
1. A method of extracting water from a quantity of moist air, comprising:
a) exposing a desiccant to moist air under pressure and temperature
conditions that encourage adsorption of water by the desiccant from
the moist air, producing a moisture-laden desiccant and dried air;
b) separating the moisture-laden desiccant from a portion of the
dried air; c) exposing the moisture-laden desiccant to pressure
and temperature conditions that encourage desorption of water vapor
from the moisture-laden desiccant, producing desorbed water vapor
and a dried desiccant; d) collecting a portion of the desorbed water
vapor in a condensation chamber and isolating the condensation chamber
from the dried desiccant; e) increasing the pressure in the condensation
chamber to a pressure that encourages condensation of liquid water
from the desorbed water vapor; f) collecting a portion of the condensation
from the condensation chamber.
2. A method of extracting water from a quantity of moist air, comprising:
a) exposing a desiccant to moist air under substantially atmospheric
temperature and pressure, producing a moisture-laden desiccant and
dried air; b) isolating the moisture-laden desiccant from a portion
of the dried air; c) reducing the pressure surrounding the moisture-laden
desiccant to a pressure that encourages desorption of water vapor
from the moisture-laden desiccant, producing water vapor and a dried
desiccant; d) collecting a portion of the desorbed water vapor in
a condensation chamber and isolating the condensation chamber from
the dried desiccant; e) increasing the pressure in the condensation
chamber to a pressure that encourages condensation of liquid water
from the desorbed water vapor; f) collecting water from the condensation
in the condensation chamber.
3. A method of extracting water from a quantity of moist air, comprising:
a) configuring a first chamber containing moisture-adsorbing desiccant
in fluid communication with a source of moist air; b) after the
desiccant has adsorbed water from the moist air, exhausting dried
air from the first chamber; c) configuring a second chamber in fluid
communication with the desiccant; d) reducing the pressure in the
second chamber, encouraging water vapor from the desiccant into
the second chamber; e) configuring a third chamber containing water
vapor and substantially not in fluid communication with the desiccant;
f) increasing the pressure in the third chamber sufficient to cause
water vapor to condense to liquid water; g) collecting liquid water
from the third chamber.
4. A method of extracting water from moist air using an apparatus
comprising a first chamber defined by first walls and a first piston,
a second chamber defined by second walls and a second piston, and
a desiccant, where the first and second chambers are configurable
to be in either fluid communication or fluid isolation relative
to the desiccant, said method comprising: a) configuring the first
chamber to be in fluid communication with the desiccant, and introducing
a quantity of moist air; b) after the desiccant has adsorbed water
from the moist air, exhausting air from the first chamber; c) configuring
the second chamber to be in fluid communication with the desiccant;
d) expanding the second chamber to desorb water from the desiccant
into water vapor in the second chamber; e) configuring the second
chamber to be in fluid isolation relative to the desiccant; f) compressing
the water vapor in the second chamber to form liquid condensate.
5. An apparatus for the extraction of water from air, comprising:
a) a desiccant; b) a first chamber defining an air path from an
air intake port over the desiccant to an air exhaust port; c) an
intake valve mounted with the first chamber to control flow through
the intake port; d) an exhaust valve mounted with the first chamber
to control flow through the exhaust port; e) a second chamber f)
an interchamber valve mounted between the first and second chambers
to control flow between the desiccant and the second chamber and
to isolate the desiccant from the second chamber; g) means for varying
the pressure in the second chamber; and h) means for removing condensate
from the second chamber.
6. The apparatus of claim 5 wherein the means for varying the
pressure in the second chamber comprises a piston moveable within
the second chamber to vary the volume of the second chamber.
7. The apparatus of claim 5 wherein the means for removing condensate
from the second chamber comprises a valve controlling water flow
through a condensate port from the second chamber.
8. An apparatus for the extraction of water from air, comprising:
a) a desiccant; b) a first chamber defining an air path from an
air intake port over the desiccant to an air exhaust port; c) a
first piston mounted with the first chamber, moveable between first
and second positions, where in the first position the first piston
substantially prevents fluid communication between the air intake
port and the first chamber, and substantially prevents fluid communication
between the air exhaust port and the first chamber; and where in
the second position the first piston does not prevent fluid communication
between the air intake port, the air exhaust port, and the first
chamber; d) a second chamber, divided into a compression portion
and a vacuum portion by a second piston moveable within the second
chamber; e) an interchamber valve controlling fluid flow between
the first chamber and the compression portion of the second chamber;
f) means for collecting condensate from the compression portion
of the second chamber.
9. The apparatus of claim 8 wherein the means for collecting condensate
from the compression portion of the second chamber comprises a valve
controlling fluid flow from the compression portion of the second
chamber.
10. The apparatus of claim 8 wherein the first piston comprises
a first surface facing the first chamber and a second surface facing
away from the first chamber, and wherein fluid at substantially
the same pressure as air at the air intake port contacts the second
surface.
11. The apparatus of claim 8 wherein when the first piston is in
the first position the first piston causes the volume of the first
chamber to be not more than twice the volume required to accommodate
the desiccant.
12. The apparatus of claim 8 wherein when the first piston is in
the first position the first piston causes the volume of the first
chamber to be not more than 10% more than the volume required to
accommodate the desiccant.
13. The apparatus of claim 8 wherein the vacuum portion of the
second chamber is maintained at a pressure lower than the pressure
of air in the air path.
14. The apparatus of claim 8 wherein the vacuum portion of the
second chamber is maintained at a pressure not more than the vapor
pressure of the water in the desiccant.
15. The apparatus of claim 8 wherein the pressure in the vacuum
portion of the second chamber is maintained by a liquid-vapor pressurization
system.
16. The apparatus of claim 8 wherein the second piston has a lapped
sealing relationship with the second chamber.
17. The apparatus of claim 8 wherein the second piston comprises
a rolling diaphragm piston.
18. The apparatus of claim 8 wherein the means for collecting condensate
comprises a condensate trap and a relief valve.
19. An apparatus for the extraction of water from air, comprising:
a) first and second desiccant adsorption units, where each desiccant
adsorption unit comprises: i) a desiccant; ii) a first chamber defining
an air path from an air intake port over the desiccant to an air
exhaust port; iii) a first piston mounted with the first chamber,
moveable between first and second positions, where in the first
position the first piston substantially prevents fluid communication
between the air intake port and the first chamber, and substantially
prevents fluid communication between the air exhaust port and the
first chamber; and where in the second position the first piston
does not prevent fluid communication between the air intake port,
the air exhaust port, and the first chamber; b) a second chamber,
divided into a first compression portion and a second compression
portion by a compression piston moveable within the second chamber;
c) a first interchamber valve controlling fluid flow between the
first chamber of the first desiccant adsorption unit and the first
compression portion of the second chamber; d) a second interchamber
valve controlling fluid flow between the first chamber of the second
desiccant adsorption unit and the second compression portion of
the second chamber; e) means for collecting condensate from the
first compression portion of the second chamber; f) means for collecting
condensate from the second compression portion of the second chamber.
20. The apparatus of claim 19 wherein the first piston of each
desiccant adsorption unit comprises a first surface facing the first
chamber of the desiccant adsorption unit and a second surface facing
away from the first chamber of the desiccant adsorption unit, and
wherein fluid at substantially the same pressure as air in the air
path of the desiccant adsorption unit contacts the second surface.
21. The apparatus of claim 19 wherein when the first piston of
each desiccant adsorption unit is in the first position the first
piston of the desiccant adsorption unit causes the volume of the
first chamber of the desiccant adsorption unit to be not more than
twice the volume required to accommodate the desiccant of the desiccant
adsorption unit.
22. The apparatus of claim 19 wherein when the first piston of
each desiccant adsorption unit is in the first position the first
piston of the desiccant adsorption unit causes the volume of the
first chamber of the desiccant adsorption unit to be not more than
10% more than the volume required to accommodate the desiccant of
the desiccant adsorption unit.
23. The apparatus of claim 19 wherein the second piston has a lapped
sealing relationship with the second chamber.
24. The apparatus of claim 19 wherein the second piston comprises
a rolling diaphragm piston.
Description BACKGROUND OF THE INVENTION
This invention relates to the field of water-air interactions,
specifically the extraction of water from moist air (a mixture of
air and water vapor).
Water, especially potable water, is a constant need. Obtaining
water is a threshold requirement for most human and animal activity.
Obtaining water can be especially problematic in arid areas. Tremendous
effort and expense currently go to drilling wells, building water
transport systems, and purifying and desalinating water.
Water is conventionally obtained by purifying existing liquid water.
Reverse osmosis, distillation, and filtration are used to purify
contaminated water. Desalination is used to produce potable water
from sea water. These approaches can be energy-intensive, and require
the presence of liquid water as the starting material.
If liquid water is not available, then purification processes are
not applicable. Dehumidification by refrigeration can be used to
produce liquid water from moist air. Conventional refrigeration
processes are very energy-intensive, however. Further, conventional
refrigeration processes can involve large and complex machines.
Consequently, conventional refrigeration processes are generally
not economical for production of potable water.
Accordingly, there is a need for a method and apparatus for obtaining
potable water from moist air that does not require the expense or
complexity of conventional refrigeration processes.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for extracting
liquid water from moist air using minimal energy input. The method
can be considered as four phases: (1) adsorbing water from air into
a desiccant, (2) isolating the water-laden desiccant from the air
source, (3) desorbing water as vapor from the desiccant into a chamber,
and (4) isolating the desiccant from the chamber, and compressing
the vapor in the chamber to form liquid condensate. The liquid condensate
can be removed for use. Careful design of the dead volumes and pressure
balances can minimize the energy required. The dried air can be
exchanged for fresh moist air and the process repeated.
The apparatus comprises a first chamber in fluid communication
with a desiccant, and having ports to intake moist air and exhaust
dried air. The apparatus also comprises a second chamber in fluid
communication with the desiccant. The second chamber allows variable
internal pressure, and has a port for removal of liquid condensate.
Each chamber can be configured to be isolated or in communication
with the desiccant. The first chamber can be configured to be isolated
or in communication with a course of moist air. Various arrangements
of valves, pistons, and chambers are described.
Advantages and novel features will become apparent to those skilled
in the art upon examination of the following description or may
be learned by practice of the invention. The objects and advantages
of the invention may be realized and attained by means of the instrumentalities
and combinations particularly pointed out in the appended claims.
DESCRIPTION OF THE FIGURES
The accompanying drawings, which are incorporated into and form
part of the specification, illustrate embodiments of the invention
and, together with the description, serve to explain the principles
of the invention.
FIG. 1 is a schematic representation of an apparatus according
to the present invention.
FIG. 2 is a schematic representation of an apparatus according
to the present invention.
FIG. 3(a,b,c,d,e,f) is a schematic representation of the apparatus
of FIG. 2 in operation.
FIG. 4 is a schematic representation of an apparatus according
to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method and apparatus for extracting
liquid water from moist air using minimal energy input. The method
can be considered as four phases: (1) adsorbing water from air into
a desiccant, (2) isolating the water-laden desiccant from the air
source, (3) desorbing water as vapor from the desiccant into a chamber,
and (4) isolating the desiccant from the chamber, and compressing
the vapor in the chamber to form liquid condensate. The liquid condensate
can be removed for use. Careful design of the dead volumes and pressure
balances can minimize the energy required. The dried air can be
exchanged for fresh moist air and the process repeated.
The apparatus comprises a first chamber in fluid communication
with a desiccant, and having ports to intake moist air and exhaust
dried air. The apparatus also comprises a second chamber in fluid
communication with the desiccant. The second chamber allows variable
internal pressure, and has a port for removal of liquid condensate.
Each chamber can be configured to be isolated or in communication
with the desiccant. The first chamber can be configured to be isolated
or in communication with a course of moist air. Various arrangements
of valves, pistons, and chambers are described. The method of the
present invention can be understood from the description of the
operation of the various embodiments described.
Example Embodiment
FIG. 1 is a schematic diagram of an embodiment of the present invention.
Walls 110 define a flow path 102 from a valve-controlled air intake
103 to a valve-controlled air exhaust 104 (where "valve"
includes any device, structure, or material interaction that controls
flow of a fluid). Desiccant 101 is situated so as to be exposed
to moist air in the flow path 102. Valve 105 controls fluid communication
between desiccant 101 and chamber 106 defined by walls 109 and piston
107 moveable relative thereto. Condensate from chamber 106 can be
removed via valve-controlled water port 111.
In operation, intake 103 and exhaust 104 valves are open, and inter-chamber
valve 105 is closed. Air flows in flow path 102 over desiccant 101
allowing desiccant 101 to adsorb water from the air. After desiccant
101 has adsorbed sufficient water, then intake 103 and exhaust 104
valves can be closed, and inter-chamber valve 105 opened. Piston
107 begins at a position minimizing the volume of chamber 106. After
inter-chamber valve 105 is opened, piston 107 can be moved to increase
the volume of chamber 106 decreasing the pressure surrounding desiccant
101 and encouraging desorption of water vapor from desiccant 101
into chamber 106. After sufficient water vapor has desorbed into
chamber 106 inter-chamber valve 105 can be closed, isolating chamber
106 from desiccant 101. Piston 107 can then be moved to reduce the
volume of chamber 106 compressing the water vapor therein and fostering
condensation. Condensation can then be drawn from chamber 106 as
liquid water through water port 111.
Example Embodiment
Varying the design of the previous example embodiment can reduce
the energy required to extract water. FIG. 2 is a schematic diagram
of an embodiment of the present invention considering the energy
required. Walls 210 and an air piston 212 define a flow path 202
from an air intake 203 to an air exhaust 204. A desiccant 201 is
situated so as to be exposed to moist air in the flow path 202.
An air piston 212 is moveable between a first position, where the
intake 203 and exhaust 204 ports are open, and a second position,
where the intake 203 and exhaust 204 ports are closed and the air
space adjacent the desiccant 201 is minimized (e.g., less than twice
the desiccant volume, or less than 10% more than the desiccant volume).
Walls 209 define a volume separated into two chambers, a vacuum
chamber 208 and a compression chamber 206 by a vacuum piston 207.
The vacuum piston 207 is moveable within the volume, changing the
volumes of the two chambers 208 206. The vacuum piston can, for
example, have a lapped sealing relationship with the walls, and
can comprise a rolling diaphragm piston. An interchamber valve 205
controls fluid communication between the desiccant 201 and the compression
chamber 206. A water collection valve 211 allows liquid water to
be extracted from the compression chamber 206.
FIG. 3(a,b,c,d,e,f) illustrate the operation of the apparatus of
FIG. 2. In FIG. 3a, air (e.g., atmospheric air) is passed over a
desiccant 201 through intake 203 and exhaust 204 ports. The desiccant
201 adsorbs water from the air. Once the desiccant 201 has adsorbed
sufficient water (e.g., reached saturation), an air piston 212 moves
toward the desiccant 201 until it has expelled the remaining air
from the flow path 202 and closed both ports 203 204. The air piston
212 itself closes the ports 203 204 in the embodiment illustrated,
obviating separate intake and exhaust valves. The air piston 212
can move toward the desiccant 201 until it is in contact with the
desiccant 201 as in FIG. 3b, leaving a minimum dead volume. If
both sides of the air piston 212 are exposed to the same air source
(e.g., atmospheric), the pressure differential across the air piston
212 is substantially zero, and the work required to move the air
piston 212 is minimal. Minimizing the dead volume, around the desiccant
201 and in any valves, can be important for efficiency. Additional
dead volume requires additional work in later phases of the operation.
After the air piston 212 is moved toward the desiccant 201 an
interchamber valve 205 can be opened to allow fluid communication
from the desiccant 201 to the compression chamber 206. The vacuum
piston 207 can move to increase the volume of the compression chamber
206 (move to the right in the figure). If the vacuum chamber 208
is maintained at roughly a vacuum, little energy is required to
move the vacuum piston 207 since the pressure differential across
the vacuum piston 207 is roughly zero. As the vacuum piston 207
moves, the pressure in the compression chamber 206 drops until it
reaches the vapor pressure of the water in the desiccant 201. At
this point water begins to be desorbed from the desiccant 201 as
in FIG. 3c. After sufficient water has desorbed from the desiccant
201 into water vapor in the compression chamber 206 the interchamber
valve 205 can be closed, isolating the desiccant 201 from the compression
chamber 206 and the water capture valve 211 can be opened, allowing
liquid water to leave the compression chamber 206 as shown in FIG.
3d. After the desiccant 201 is isolated from the compression chamber
206 the air piston 212 can move away from the desiccant 201 and
allow air to flow over the desiccant 201 repeating the initial
adsorption phase.
The vacuum piston 207 can then move to compress the water vapor
in the compression chamber 206 (move to the left in FIG. 3e). When
the pressure in the compression chamber 206 exceeds the saturation
pressure of the water vapor, condensation occurs. As before, minimizing
dead volume can reduce the amount of energy required to achieve
sufficient compression. Also, using a liquid-vapor pressurization
system in the vacuum chamber 208 can minimize the pressure differential
across the vacuum piston 207 minimizing the energy required to
expand and the compress compression chamber 206. Maintaining the
vacuum chamber 208 at a pressure less than the pressure of the air
flowing over the desiccant can allow for lower required energy;
maintaining at a pressure not more than the vapor pressure of water
in the desiccant can be suitable. The absolute pressure required
to foster condensation can be several times the water saturation
pressure (on the order of 50 Pa-10000 Pa depending on the temperature)
since there is very little air in the compression chamber 206. As
the water condensed it can drain through the water collection valve
211. Vacuum piston movement can also collect condensation from the
walls 209 and guide it to the water collection valve 211. When the
vacuum piston 207 returns to its initial position as illustrated
in FIG. 3f, the water collection valve 211 can be closed and the
expansion/compression phases repeated once the desiccant 201 has
again adsorbed sufficient water from the air.
Example Embodiment
A second desiccant adsorption subsystem can be added to the previous
example embodiment. FIG. 4 is a schematic diagram of such an embodiment.
Two desiccant adsorption subsystems 421 423 mount and operate with
two compression chambers 406 and 408 defined by vacuum piston 407.
Compression chamber 406 operates with one desiccant adsorption subsystem
421 and compression chamber 408 operates with the other desiccant
adsorption subsystem 423. Subsystem 421 is comprised of walls 410
air piston 412 desiccant 401 walls 409 compression chamber 406
vacuum piston 407 interchamber valve 405 and water collection valve
411. The air piston 412 defines a flow path 402 from an air intake
403 to an air exhaust 404. Subsystem 423 is comprised of walls 410b,
air piston 412b, desiccant 401b, walls 409 compression chamber
408 vacuum piston 407 interchamber valve 405b and water collection
valve 411b. The air piston 412b defines a flow path 402b from an
air intake 403b to an air exhaust 404b. Each desiccant adsorption
subsystem operates with its compression chamber substantially as
described above. Each compression chamber operates as the vacuum
chamber described above for the other compression chamber. A single
piston can therefore serve as a compression piston for roughly twice
the processing capacity of the previous embodiment. Each compression
chamber is exposed to a pressure of approximately the water vapor
pressure in the corresponding desiccant, so the pressure differential
across the piston between the chambers is very low. Consequently,
the energy required to move the piston can be very low. Further,
the size of the overall two desiccant apparatus can be smaller than
would be required for two of the previous single desiccant apparatus.
The particular sizes and equipment discussed above are cited merely
to illustrate particular embodiments of the invention. It is contemplated
that the use of the invention may involve components having different
sizes and characteristics. It is intended that the scope of the
invention be defined by the claims appended hereto. |