Note: Descriptions are shown in the official language in which they were submitted.
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CONDENSATION SYSTEM FOR DEHUMIDIFICATION AND DESALINATION
FIELD OF THE INVENTION
The present invention relates to condensation systems,
and more particularly to dehumidification and desalination
systems.
BACKGROUND ART
In a greenhouse, it is desirable to control the interior
environment, and in particular the humidity level, so as to
reduce energy consumption and increase productivity of plants.
Too much humidity within the greenhouse usually causes fungus
formation and/or condensation of the water vapor on the light
transmitting surfaces (e.g. translucent roof), with the
condensed water causing reduced light penetration through
these surfaces and potentially damaging dripping onto the
plants. In order to control the humidity, greenhouses are
often ventilated, which during cold weather generally wastes
energy as well as causes variations in the interior
temperature which are usually unhealthy for the plants, and
during summer usually allows the entry of pests, exterior
spores, diseases and/or unwanted pollen. Furthermore, the
amount of wasted water through the evaporation process of
healthy plants is costly; thus water recovery of pure clean
water further reduces the costs of operation.
Few systems are specifically designed to function in
today's large greenhouses. Examples of systems which may be
used in a greenhouse include systems devised to condense water
vapor found in the air of an enclosure (e.g. a greenhouse)
where the water vapor is condensed on wall and/or roof
surfaces of the enclosure and the resulting condensate is
collected. For example, it is known to have a greenhouse
enclosed by a translucent impermeable fabric shell with water
sprayed on the outside of the fabric shell to cool it such as
to enhance condensation of water vapor within the greenhouse
on the inside surface of the fabric shell. However, such a
structure generally does not efficiently condense water due to
the relatively poor conductivity of the translucent fabric,
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and the heat of the greenhouse is usually rapidly lost during
the night and during daytime periods of reduced sunlight, thus
limiting the amount of water that can be condensed. In
addition, the spraying of water on the exterior surface of the
translucent fabric or membrane usually tends to leave
evaporative marks on the fabric, thus reducing the
translucence thereof. Moreover, the water spray may
undesirably reduce the amount of light let through the
translucent fabric, thus providing unwanted shade on the
plants within the greenhouse.
Accordingly, improvements are desirable.
SUMMARY OF INVENTION
It is therefore an aim of the present invention to
provide an improved condensation system.
Therefore, in accordance with a general aspect of the
application, there is provided a condensation system
comprising: an enclosure containing humid air, the enclosure
being at least partly defined by a roof structure, the roof
structure including a covering member having two spaced apart
layers of translucent material adapted to let sunlight
therethrough and defining a sealed cavity therebetween;a
foaming system temporarily filling the cavity with foam to
increase insulating properties of the covering member and
removing the foam to let sunlight through the covering member
during given periods to heat the enclosure; an angled
condensation panel made of a heat conducting material and
exposed to the humid air in the enclosure; a coolant system
for cooling the condensation panel to a temperature lower than
a temperature of the humid air; and a collection system
collecting water condensing from the humid air on an inner
surface of the condensation panel.
In accordance with another general aspect of the
application, there is provided a condensation system
comprising: a humid air enclosure at least partly defined by a
roof structure having a portion made of translucent material
adapted to let sunlight therethrough to heat the enclosure; a
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condensation panel made of a heat conducting material, the
condensation panel being exposed to humid air contained in the
enclosure, the condensation panel being disposed such that a
flow of sunlight through the translucent material within the
enclosure is at least substantially free of obstruction from
the condensation panel; a coolant system creating a flow of
coolant over a first surface of the condensation panel to
bring the condensation panel to a temperature lower than a
temperature of the humid air; and a condensate collection
system collecting water condensing from the humid air on a
second surface of the condensation panel opposite the first
surface thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference will now be made to the accompanying drawings,
showing by way of illustration a particular embodiment of the
present invention and in which:
Fig. 1 is a front, cross-sectional view of a greenhouse
with a condensation system used as a dehumidifying system in
accordance with a particular embodiment of the present
invention;
Fig. 2 is a side, cross-sectional view of part of the
greenhouse of Fig. 1; and
Fig. 3 is a side cross-sectional view of a condensation
system used as a desalination system in accordance with an
alternate embodiment of the present invention.
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
Referring now to Figs. 1-2, a condensation system 10
according to a particular embodiment of the present invention
is shown. In this embodiment, the condensation system 10 is
used as a dehumidification system in a greenhouse 12.
The greenhouse 12 includes a enclosure or enclosure 14
for receiving plants therein and containing humid air, the
enclosure 14 being defined by a front wall (not visible in the
Figures), a rear wall 16 and opposed side walls 18 (see Fig.
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2) extending from a ground surface and sealingly
interconnected to define a perimeter, and a roof structure 20
sealingly connected to a top of the walls 16, 18.
The roof structure 20 is part of the condensation system
and comprises a plurality of spaced apart arches 22
extending between the top of the side walls 18 and
interconnected at their apex by a longitudinal top truss 24,
and a membrane or covering member 26 stretched over the arches
and truss 22, 24 and retained thereon.
The covering member 26 is made of a material permeable to
light, such as to allow solar energy to heat the enclosure
therethrough. In a particular embodiment, the covering member
26 is made of polyethylene sheet material. Alternately, the
covering member 26 can be made of glass, polycarbonate, or
another adequate type of plastic. In a particular embodiment
the walls 16, 18 are made of a similar material, supported
over an adequate framework of trusses, arches and/or posts.
In the embodiment shown, the covering member 26 comprises
two spaced apart layers 28 of material permeable to light,
defining a sealed cavity 30 therebetween, with the layers 28
being maintained in spaced apart relationship through low
pressure air received within the cavity 30. In a particular
embodiment, the cavity 30 is temporarily filled with an
appropriate type of foam 32 (only partially illustrated in the
Figures) during nighttime and/or during any other time where
heat needs to be retained within the enclosure. Examples of
appropriate foams and foaming systems are shown in U.S. Patent
No. 4,562,674 issued Jan. 7, 1986 to Nelson, U.S. Patent No.
6,575,234 issued Jun. 10, 2003 to Nelson, and PCT application
No. WO 2005/085541 from Amar et al. published Sept. 15, 2005,
the specifications of all of which are incorporated herein by
reference. Other adequate types of foams and foaming systems
can also alternately be used.
The condensation system 10 also includes a condensation
panel 34, which extends within the enclosure 14 in proximity
of the rear wall 16 but spaced apart therefrom. The
condensation panel 34 extends from the top of the side walls
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18 to the top truss 24 and is angled such that its top edge 36
extends inwardly of its bottom edge 38. Alternately the
condensation panel 34 can extend below the top of the side
walls 18 if a larger condensation surface is required. The
condensation panel 34 is made of any adequate heat conductive
material, such as for example anodized aluminum, copper, iron
or another appropriate type of metal. In a particular
embodiment, the condensation panel 34 includes an optional
enhancing surface coating increasing its conductivity. The
condensation panel 34 is also preferably corrugated with
grooves and ridges such as have an increased panel surface for
a given panel width. The size of the grooves and ridges is
preferably selected based on the conductivity of the panel
and/or on the type and flow of coolant. In a particular
embodiment, the grooves and ridges are almost parallel to the
ground, extending at a slight angle to form a descending slope
directed toward a return conduit 58 to be described further
below. The number and size of the grooves and ridges is varied
to obtain a desired condensation surface of the panel 34.
The condensation system 10 further includes a coolant
spraying assembly 40. The coolant spraying assembly 40
comprises a coolant reservoir 42, which in a particular
embodiment is located underground to maintain a low
temperature of the coolant, a main conduit 44 extending from
the coolant reservoir 42 and connected to a plurality of
secondary conduits 46 located in proximity of an outer surface
48 of the condensation panel 34, and a plurality of spraying
nozzles 50 in fluid communication with the secondary conduits
46. The coolant spraying assembly 40 also includes a pump 52,
which pumps the coolant from the coolant reservoir 42, through
the conduits 44, 46 and to the spraying nozzles 50. The
spraying nozzles 50 are located and oriented to spray the
coolant on the outer surface 48 of the condensation panel 34.
The condensation system 10 further includes a coolant
collection system 54, comprising a coolant gutter 56 (see Fig.
2) which extends along the bottom edge 38 of the condensation
panel 34 and is placed such that the coolant sprayed onto the
outer surface 48 of the condensation panel 34 and flowing
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downwardly along that surface falls within the coolant gutter
56. The coolant collection system 54 further comprises a
coolant return conduit 58 in fluid communication with the
coolant gutter 56 and returning the collected coolant to the
coolant reservoir 42 by gravity.
The condensation system 10 shown is particularly adapted
for colder climates, where the coolant, if unprotected from
the outside environment, could potentially freeze in the
spraying nozzles 50 and/or on the condensation panel 34. In an
alternate embodiment particularly suitable for warmer
climates, the condensation panel 34 defines an exterior
surface of the roof structure 20, i.e. the outer surface 48 of
the condensation panel 34 and at least the spraying nozzles 50
are located outside of the enclosure 14.
In a particular embodiment, the coolant is cool tap
water. Alternate coolants that can be used include sea, lake
or pond water (in that instance the main conduit 44 and the
coolant return conduit 58 can be in direct communication with
the sea, lake or pond and the coolant reservoir 42 can thus be
omitted), and glycol. Glycol is particularly useful in a
closed circuit system to maximize the useful time of the
coolant as well as in freezing conditions.
In a particular embodiment, the pumped coolant goes
through a refrigeration system (not shown) before being sent
to the spraying nozzles 50 in order to increase the cooling of
the condensation panel 34. Such a refrigeration system can
include for example propane or natural gas-driven chillers, or
solar powered condensers and cooling towers.
The condensation system 10 further includes a condensate
collection system 60, comprising a condensate gutter 62 which
extends along the bottom edge 38 of the condensation panel 34
and is placed such that liquid flowing downwardly along an
inner surface 64 of the condensation panel 34 falls within the
condensate gutter 62, and a condensate return conduit 66 in
fluid communication with the condensate gutter 62 and
directing the condensate to a condensate reservoir 68 by
gravity.
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In use, the coolant is sprayed onto the outer surface 48
of the condensation panel 34 such as to create a continuous
cooling film thereon, effectively cooling the condensation
panel 34 to a temperature lower, and preferably at least 5 C
lower, than the humid air within the enclosure 14. The coolant
flows along the outer surface 48 of the condensation panel 34,
into the coolant gutter 56, and returns to the coolant
reservoir 42 through the coolant return conduit 58 for
recirculation. In cases where the coolant does not circulate
through a refrigeration system between each time it is sprayed
on the condensation panel 34, the coolant is recirculated
until its temperature becomes too high to provide proper
cooling, at which point the used coolant is exchanged for
fresh coolant with an adequately low temperature. The
exhausted coolant can be cooled in a refrigeration system and
later re-used in the coolant spraying assembly 40. Sunlight
enters the enclosure 14 through the covering member 26 which
is free of foam, and heats the enclosure 14. Water from within
the enclosure 14 (e.g. plant transpiration) evaporates to
increase the vapor content of the air. A portion of the water
vapor contained in the humid air condensates on the cool inner
surface 64 of the condensation panel 34, flows along the
corrugations of the inner surface 64 into the condensate
gutter 62, and into the condensate reservoir 68 through the
condensate return conduit 66. The condensation system 10 thus
allows the reduction of the humidity content within the
enclosure 14 when necessary. In addition, the condensate can
be used in the greenhouse 12, such as for example for
cleaning, watering plants, etc.
In a particular embodiment, the outer surface 48 of the
condensation panel 34 is covered by a screen member (not
shown) or another similar structure acting to slow the flow of
coolant therealong in order to increase the heat transfer
between the coolant and the condensation panel 34.
The angle of the condensation panel 34 is selected such
as to allow the condensate to flow along the inner surface 64
(i.e. by opposition to dripping vertically therefrom), while
preferably being as close to vertical as possible to minimize
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the solar energy absorbed by the panel 34. In a particular
embodiment, the condensation panel 34 forms an angle e (see
Fig. 2) of approximately 68 with the horizontal. The possible
angle variation depends on the design of the grooves and
ridges on the condensation panel 34. In a particular
embodiment, the condensation panel 34 is retained such that
the angle thereof can be varied depending on the type of
coolant being used, taking into account relevant factors such
as the. degree of heat absorption and the viscosity of the
coolant.
In order to maximize the efficiency of the condensation
process, the rear side of the greenhouse, i.e. the
condensation panel 34, preferably faces north or north east.
In an alternate embodiment which is not shown, the
condensation panel 34 is enclosed similarly to a radiator,
with the coolant passing inside the panel within tubes instead
of being sprayed thereon. The slope of the condensation panel
34 is preferably variable depending on the type of coolant
being used and on the degree of heat absorption from the
condensate side of the panel 34. The coolant is preferably
collected after circulation through the panel 34 to be re-
chilled. The size of the tubes circulating the coolant within
the panel is selected according to the conductivity of the
panel and/or the flow and type of coolant.
During the night, the cavity 30 defined between the
layers 28 of the covering member 26 is filled with foam 32,
such as to insulate the covering member 26 and minimize the
loss of heat therethrough. As the air within the enclosure 14
is kept warm, the condensation along the inner surface 64 of
the condensation panel 34 can continue for at least part of
the night. The cavity 30 can also be filled with foam during
the day when sunlight is inadequate, when shading is desired
to reduce excessive sunlight and cool the enclosure 14, or
when the temperature within the enclosure 14 is at a maximum
desirable value.
In a particular embodiment, during the period when there
is no foam between the layers 28 of the covering member 26
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(e.g. daytime), the air located within the cavity 30 and
heated by the sunlight exits the cavity 30 through a chimney
(not shown) such as to rotate fan blades (not shown) to
generate electricity, which can be used for example to drive
the pump 52.
Referring to Fig. 3, a condensation system 110 according
to an alternate embodiment of the present invention is shown,
where the condensation system 110 is used as a water
purification system and more particularly as a desalination
system. Elements not shown in Fig. 3 are, in a particular
embodiment, similar to the corresponding elements shown in
Figs. 1-2.
The condensation system 110 includes a desalination
enclosure 114 installed such as to enclose a salt water basin
or pool ill (whether natural or artificial) and a volume of
humid air defined over the basin 111. The enclosure 114 is
defined by an angled roof structure 120 extending from the
ground and an angled condensation panel 134 extending from the
ground and connected to the roof structure 120 along an apex
of the enclosure 114. The roof structure 120 may be flat as
shown or alternately be curved from its peak to its base.
Alternately, the enclosure can include walls with the roof
structure 120 and condensation panel 134 being sealingly
received on top of the walls, the roof structure 120
preferably being inclined in at least one plane (e.g.
arcuate).
As in the previous embodiment, the condensation panel 134
is made of a heat conductive material such as for example
anodized aluminum, copper, iron or another appropriate type of
metal, and is also preferably corrugated with grooves and
ridges extending almost parallel to the ground with a small
slope to one side so as to permit the condensate to flow to
one side to a specific location. Alternately, the grooves can
extend along the height of the panel 134 as in the previous
embodiment.
The roof structure 120 can include an arch and truss
framework as in the previous embodiment, or any other type of
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adequate support structure. The roof structure includes a
covering member 126 which is made of a material permeable to
light, for example polyethylene sheet material, glass,
polycarbonate, or another adequate type of plastic. In the
embodiment shown, the covering member 126 includes two spaced
apart layers 128 of material permeable to light and defining a
sealed cavity 130 therebetween, which is preferably
temporarily filled with an appropriate type of foam 132 (only
partially shown in the Figure) during nighttime and any other
time where heat needs to be retained within the enclosure 114
or when sunlight needs to be blocked. In a particular
embodiment, the lower one of the layers 128 is maintained by
an appropriate structure (e.g. an arch and truss framework)
and the upper one of the layers 128 is maintained spaced apart
from the lower layer by the low pressure air contained within
the cavity 130.
In a particular embodiment, the angle al of the
condensation panel 134 with respect to the horizontal is
substantially greater than the angle a2 of the roof structure
120 with respect to the horizontal, such that a surface of the
roof structure 120 is substantially larger than a surface of
the condensation panel 134 in order to optimize the heating of
the enclosure 114 as well as the amount of condensate
produced.
The condensation system 110 also includes a coolant
spraying assembly 140, comprising a coolant reservoir (not
shown) or a cold water source, a main conduit (now shown)
extending from the coolant reservoir or source and connected
to a plurality of secondary conduits 146 located in proximity
of an outer surface 148 of the condensation panel 134, and a
plurality of spraying nozzles 150 in fluid communication with
the secondary conduits 146. A pump (not shown) pumps the
coolant from the reservoir or source to the spraying nozzles
150 which spray the coolant on the outer surface 148 of the
condensation panel 134.
The condensation system further includes a coolant
collection system 154 comprising a coolant gutter 158 which
extends along the bottom edge 138 of the condensation panel
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134 to collect the coolant flowing downwardly along the outer
surface 148 of the panel 134, and a coolant return conduit
(not shown) returning the collected coolant to the reservoir
by gravity.
The condensation system 110 further includes a condensate
collection system 160 comprising a condensate gutter 162 which
extends along the bottom edge 138 of the condensation panel
134 to collect the condensate flowing downwardly along an
inner surface 164 of the panel 134, and a condensate return
conduit (not shown) in fluid communication with the condensate
gutter 162 and directing the condensate to a condensate
reservoir (not shown) by gravity.
As in the previous embodiment, the coolant sprayed onto
the outer surface 148 of the condensation panel 134 cools the
condensation panel 134 to a temperature lower, and preferably
C lower, than the humid air within the enclosure 114, and is
collected in the coolant gutter 156 to be returned to the
coolant source. Sunlight goes through the covering member 126
which is free of foam, and heats the enclosure 114 and as such
the top layer of salt water within the basin 111, thus
allowing that water to evaporate. The evaporated water
contained in the air of the enclosure 114 condensates on the
cool inner surface 164 of the condensation panel 134, and is
collected in the condensate gutter 162 to then flow into the
condensate reservoir. The evaporation and condensation cycle
thus effectively desalinates the salt water from the basin 111
and eliminates any impurities that are naturally separated
from water upon vaporization. A slight amount of salt may
remain in the condensate and can be removed therefrom by known
processes, such as for example reverse osmosis.
In a particular embodiment, the coolant used is cool salt
water, e.g. from the bottom of the ocean, and is recirculated
until it is warmed to a point where the temperature difference
between the coolant and the enclosure 114 is no longer
adequate to provide proper cooling. The warmed coolant is then
added to the salt water basin 111 to replace the evaporated
water, and a new coolant supply is extracted from the cool
salt water source.
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In order to maximize the efficiency of the condensation
process, the condensation panel 134 preferably faces north or
north east.
As in the previous embodiment, the cavity 130 defined
between the layers 128 of the covering member 126 is
preferably filled with foam 132 during the night such as to
minimize heat loss through the covering member 126, allowing
the desalination process to continue into the night and as
such maximizing the amount of condensate produced within a 24
hour period.
As in the previous embodiment, the hot air contained
between the layers 127 of the covering member 126 during
daytime (i.e. when the foam is removed) can be directed to a
chimney, which may extend for example 20 or 30 feet above the
apex of the enclosure 114, and used to rotate fan blades. The
coolant can also go through a refrigeration system before
being sent to the spraying nozzles 150 to further increase the
temperature difference between the condensation panel 134 and
the air within the enclosure 114.
In an alternate embodiment which is not shown, a membrane
can be provided outwardly of the condensation panel 134 and
the coolant spraying assembly 140, to provide insulation
against cold weather conditions which could freeze the
coolant. Such a membrane is preferably in sealed engagement
with the roof structure 120.
The embodiments of the invention described above are
intended to be exemplary. Those skilled in the art will
therefore appreciate that the foregoing description is
illustrative only, and that various alternate configurations
and modifications can be devised without departing from the
spirit of the present invention. Accordingly, the present
invention is intended to embrace all such alternate
configurations, modifications and variances which fall within
the scope of the appended claims.
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