Abstrict A plurality of individual, isolatable storage bins carrying a desiccant
such as silicon gel are selectively placed in communication with
a heat reclaim/solar collector within a gas circulation loop to
permit the desiccant material to be dried and to store heat almost
indefinitely in its dry state. The bins may be selectively connected
within a second circulation loop, including a room to be conditioned
such that a second gas circulated over the desiccant and to the
room varies the moisture content of the desiccant to release heat
and to thereby effect controlled heating or cooling of the air within
the room, as needed, and irrespective operation of the heat reclaim/solar
collector.
Claims What is claimed is:
1. A thermal energy storage system comprising:
(a) at least three enclosed isolatable storage bins;
(b) desiccant material within said at least three storage bins
to provide for the prolonged storage of energy in the form of dryness
of the desiccant material, said energy being derived from an unreliable
or discontinuous source of heat;
(c) a charging circuit for varying the moisture content of said
desiccant material by circulating a heated, dry gas through at least
one of said bins and over said desiccant material to cause said
desiccant material to give up moisture to said charging circuit
gas and to render said desiccant material to a dry, charged state
wherein said charging circuit includes a supply duct which is open
at one end to the atmosphere and includes a heat reclaim/solar collector
therein for raising the temperature of the ambient air entering
said charging circuit supply duct, and said charging circuit includes
a return duct which discharges to the atmosphere;
(d) a withdrawal circuit connected to said at least three bins
including means for selectively varying the moisture content of
the desiccant material by circulating a moisture laden gas through
said charged desiccant material to cause said gas to reject moisture
to the desiccant material and to thereby raise the gas temperature
within said withdrawal circuit;
(e) valve means for isolating said bins from said charging and
withdrawal circuits; and
(f) means for detecting and selectively withdrawing energy from
a bin having the highest indicated charge and charging a bin having
the lowest indicated charge.
2. The thermal energy storage system as claimed in claim 1 wherein
said charging circuit return duct includes a portion mounted adjacent
to and in contact with a portion of said charging circuit supply
duct, and wherein said system further includes a regenerative heat
exchanger interposed between said duct portions such that the air
entering said charging circuit supply duct is preheated prior to
entering said heat reclaim/solar collector.
3. The thermal energy storage system as claimed in claim 1 wherein
said withdrawal circuit includes a circuit supply duct and a return
duct, said return duct having a portion which is open to the atmosphere
for supplying air to the interior of said at least three storage
bins such that passage of ambient air through said withdrawal circuit
return duct and said bins causes, by moisture release to said desiccant
material a temperature increase to create relatively hot, dry air
for passage through said withdrawal circuit supply duct, said withdrawal
circuit supply duct further includes a heat exchanger chamber downstream
of said at least three storage bins, and said heat exchanger chamber
includes a first heat exchanger coil carrying a working fluid in
thermal energy transfer relation with respect to said gas flowing
therethrough to remove heat from the gas flowing therethrough such
that the gas discharging from said withdrawal circuit supply duct
downstream of said heat exchanger chamber constitutes relatively
dry, cool air.
4. The thermal energy storage system as claimed in claim 1 further
comprising a spray chamber within said withdrawal circuit supply
duct downstream of said heat exchanger chamber, said spray chamber
including means for spraying water vapor on the gas flowing therethrough
so as to increase the humidity of said relatively cool gas discharging
from said heat exchanger chamber.
5. The thermal energy storage system as claimed in claim 4 further
comprising a room to be conditioned, a room supply duct connecting
said withdrawal circuit supply duct to said room and intersecting
said room supply duct downstream of said spray chamber, and selectively
operable valve means at said intersection for selectively effecting
discharge of cool air from said spray chamber through the outlet
end of said supply duct or through said room supply duct leading
to said space to be conditioned.
6. The thermal energy storage system as claimed in claim 5 further
comprising a second exchange coil operatively coupled to said room
supply duct connecting said space to be conditioned to said withdrawal
circuit supply duct, and means for circulating a working fluid between
first and second heat exchanger coils within said heat exchanger
chamber and said room supply duct, respectively, for causing the
air circulating within said duct leading to said space to be conditioned,
to be heated in response to cooling of the air flowing through said
withdrawal circuit supply duct and said heat exchanger chamber.
7. The thermal energy storage system as claimed in claim 6 wherein
said withdrawal circuit return duct comprises a water spray intermediate
of the end of that duct open to the atmosphere, and said at least
three storage bins for humidifying the ambient air prior to entering
said storage bin.
8. The thermal energy storage system as claimed in claim 7 further
comprising a third heat exchanger coil positioned within said withdrawal
circuit return duct between the inlet opening to said atmosphere
and said at least three storage bin and downstream of said water
spray, and being fluid connected in series with said heat exchanger
chamber and said room heat exchanger coil to form a closed series
loop in that order, and pump means within the series loop for pumping
a working fluid through said first, second and third heat exchanger
coils to cause said working fluid to absorb heat from the air flowing
through said withdrawal circuit supply duct and within said heat
exchanger chamber, and to dissipate heat to the air passing over
said second and third heat exchanger coils.
9. The thermal energy storage system as claimed in claim 8 wherein
said withdrawal circuit return duct comprises intersecting portions
connected to said room to be conditioned and to the discharge end
of the return duct housing said third heat exchanger coil, and a
valve means within said withdrawal circuit return duct for selectively
effecting fluid communication between said storage bins and the
atmosphere while blocking fluid communication between said storage
bin and said room to be conditioned, and vice versa.
10. The thermal energy storage system as claimed in claim 1 further
comprising blower means within said charging and withdrawal circuits
for effecting forced circulation of air, at least through said heat
reclaim/solar collector and said heat exchanger chamber.
Description BACKGROUND OF THE INVENTION
Field Of The Invention
This invention relates to heating, cooling and air conditioning
systems, and more broadly to systems supplying a source of hot,
dry gas available upon demand and irrespective of availability of
conventional energy heat sources.
Nominally free energy sources such as the sun, waste heat from
commercial buildings and industrial operations by way of heat reclaim
can augment and supplement conventional heating and cooling systems
or systems designed to provide hot, dry gas, such as air, to dry
hay, seeds, clothes, lumber, various paint finishes, etc. at a steady
rate or when needed, particularly where the original source of heat
is not available when and at the time the energy is needed.
Conventionally, solar systems have employed water, rocks, earth,
etc., as means to store heat for future use, but such storage systems
are highly inefficient and are rather massive in size.
Desiccants constitute materials which attract moisture to their
surfaces. Practical desiccants constitute generally granular material
having many openings and pores such that the surface area exposed
to the gas or air inside the grain is many times the area of the
grain exterior or what appears to be the surface of the grain. Given
some time, water molecules can occupy all of the outside and inside
surfaces allowing the material to hold large quantities of water
and surface bondage without showing wetness and before loosing its
attraction for additional moisture.
For instance, a pound of silica gel can absorb 50% of its dry weight
in water without becoming damp to the feel and before loosing all
of its attraction for moisture. Activated aluminate can hold 30%
of its dry weight in water in a similar manner. These figures are
directed only to the moisture which may be held to the surfaces
of these elements by an attraction known as surface absorption.
This attraction is greatest when the material is dried of all attached
moisture, and such desiccants readily attract water from the humidity
of the gas, such as air, until the gas is at least as dry as the
desiccant. This application is directed to the employment of a readily
available gas, such as air, as the circulation media, and it is
intended that reference to air within this application infers that
the air may be readily substituted by other gases. Likewise, dry
gases will evaporate water from that held by the surface of the
desiccants until the desiccant is as dry as the gas. Large beds
of desiccants are often used for exact humidity control because
these characteristics can stabilize the moisture in air passing
over them.
The measure of dryness that most closely parallels in desiccants
and in gases is the psychometric depression, with a number of degrees
that the wet bulb of a thermometer drops below the dry bulb of another
when the wet bulb is wetted with distilled water and a gas is circulated
over both bulbs. From this, the dryness of both air and desiccant
may be stated in comparable terms. When a desiccant and a gas are
in equilibrium, they are said to have the same depression.
Water vapor, when attracted to the surface of a desiccant, takes
on liquid form or state, and the heat of vaporization is released,
plus a 20% wetting factor, amounting to about 1200 BTU's per pound
of water condensed. Thus, one pound of a very dry silica gel (having
a depression of 60.degree. F.) will release 600 BTU's from saturated
air where all of the attraction for water is used. Likewise, the
same amount of heat is absorbed by the water vapor when spent desiccant
(wet) is dried by air having a depression of 60.degree. or better,
causing the air and the desiccant to be cooled according to the
heat so removed. The sensible heat goes into the vaporization of
water, and in separating the water from the desiccant, the reverse
of the wetting process.
This principle works as well when the material is only partially
cycled, either taking on or giving up moisture--that is, is neither
completely dry nor completely wet. The amount of heat released or
absorbed by these processes is reduced by the portion that the full
cycle is not used. The full cycle value for activated aluminate
is approximately 360 BTU's.
The present invention, therefore, is directed to the utilization
of desiccants to store energy from inadequate, periodic or undependable
sources of heat for delivery in the amount needed and as the need
arises, permitting a storage system due to the characteristics of
the desiccants which is of reduced size, weight with a high percentage
of recovery, even after long storage.
It is an object of the present invention to provide a heating and/or
cooling system of this type in which energy may be supplied to the
system and the desiccant dried by solar heat, the waste heat from
a refrigeration condensor, waste heat from a stove functioning in
cooking and heating processes, waste heat from industrial processes
and by drying gases from whatever source, even if the gases are
not hot. Desiccant material so dried may be stored almost indefinitely
in its dry state with little loss of potential energy return, and
the energy may be used at any time desired to produce drying air,
heat or cooling for room conditioning of living space, as well as
for various other purposes.
SUMMARY OF THE INVENTION
In one form, the present invention constitutes a controlled heating
and cooling system for conditioning a room or the like, the system
comprising at least one isolatable desiccant storage bin containing
desiccant material, charging circuit means for varying the moisture
content of the desiccant within the bin, and withdrawal circuit
means to selectively effect circulation of a gas over said desiccant
and to the room to be conditioned and to thereby vary its moisture
content and temperature to selectively effect heating or cooling
of the room.
Preferably, a plurality of separate desiccant storage bins are
provided, and the charging circuit means to selectively vary the
moisture content of the desiccant comprises a first duct means connected
to said storage bins and being open to a source of gas, a blower
means mounted to said first duct means for forcing gas through said
first duct means and said bin, valve means for selectively closing
off said bins to said first duct means, and heating means for heating
said gas within said first duct means upstream of said bins. Said
first duct means further provides for discharging said gas passing
through said bins, said first duct means includes a duct means portion
leading from said storage bins for discharging said gas after passing
over said desiccant, and wherein said system further includes a
regenerative heat exchanger within said first duct means upstream
of said heating means and another portion. Further, valve means
are provided to close off said second duct means to said bins.
Further, preferably, second duct means are provided for connecting
said storage bins to said room to be conditioned, said second duct
means including valve means for selectively closing off said bins
to said second duct means, such that those storage bins having highly
dry desiccant may be selectively communicated to said room to be
conditioned for absorbing moisture of the gas circulating over the
desiccant to raise the temperature of the gas passing to the room.
Said second duct means may include a first heat exchange chamber
for removing thermal energy of the heated gas discharging from the
storage bins and isolated from the portion of the second means in
communication with said room to be conditioned. Said second duct
means may further comprise a bypass portion for circulating gas
to and from said room, with said bypass portion further comprising
a room heat exchange coil connected to the heat exchange coil of
said first heat exchange chamber, whereby the gas within said room
to be conditioned is indirectly heated by the air circulated from
said storage bins through said second duct means.
BRIEF DESCRIPTION OF THE DRAWING
The single FIGURE is a schematic diagram of a preferred embodiment
of the compact desiccant heat storage system of the present invention
for selective heating and cooling.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The system of the present invention, as illustrated in the FIGURE,
is designed preferably to supply either heat or cool to a room or
other space to be conditioned as at R, from desiccant materials
indicated generally at M constituting silica gel or the like carried
by individual trays 1 with the desiccant M being selectively, intermittently
and randomly dried by means of a heat reclaim/solar collector indicated
generally at 49 and responsive, for instance, for direct solar radiation
as provided by arrows S. The room R, the heat reclaim/solar collector
49 and the storage bins indicated generally at 10 20 and 30 carrying
the silica gel desiccant material are suitably connected by a duct
work. The storage bins each comprise rectangular containers having
laterally opposed side walls 2 and top and bottom walls, 3 and 4
respectively. Mounted within upper wall 3 are gate valves 11 and
14 for bin 10 and within lower wall 4 are gates valves 12 and 13.
Bin 20 includes gate valves 21 and 24 within its upper wall, and
gate valves 22 and 23 within its lower wall, while bin 30 is provided
with gate valves 31 and 34 within its upper wall and valves 32 and
33 within its lower wall. The gate valves permit the storage bins
to be under selective communication alternately to either the duct
means of the charging circuit or to the duct means of the withdrawal
circuit, respectively. The charging circuit includes a supply duct
40 and return duct 45 while the withdrawal circuit includes supply
duct 53 and return duct 52. The charging circuit supply duct indicated
generally at 40 comprises a duct portion 40a open at one end to
receive a charging gas, such as air, as indicated by arrow 48. The
duct portion 40a carries the heat reclaim/solar collector 49 permitting
the air to be heated. The air is moved by a blower 41 at the discharge
end of the heat reclaim/solar collector 49 to a charging circuit
supply duct portion 40b which opens through valves 11 21 and 31
within branch ducts to storage bins 10 20 and 30 respectively.
The charging system return duct indicated generally at 45 includes
a portion 45c which, by way of suitable branch ducts, connects to
the storage bins 10 20 and 30 by way of their lower walls 4 and
through gate valves 12 22 and 32. The charging system return duct
45 further includes a portion 45b which extends parallel, and in
contact with the charging system supply duct portion 40a, and within
which is incorporated a regenerative heat exchanger 47 such that
the inlet air as at 48 is preheated prior to entering the heat reclaim/solar
collector 49. The regenerative heat exchange results from the return
air discharging up some of its retained heat to the atmosphere,
as indicated at 46 at the terminal end of the charging circuit return
duct portion 45b. Under charging conditions, one or more of the
bins 10 20 or 30 would have their charging circuit supply duct
and return duct valves open, while the gate valves leading to the
withdrawal circuit would be closed for all storage bins being charged
at that time.
In this respect, assuming that gate valves 11 and 12 are open and
all other gate valves for the storage bins 10 20 and 30 are closed,
charging air represented by arrow 42 and having a relatively low
humidity such as coming from a dry source or after being heated
by the heat reclaim/solar collector 49 which may, for instance,
be any source of heat at around 60.degree. F. above the intake temperature
of the charging air as at 48 is directed to storage bin 10 under
pressure by operation of blower 41. The gate valves, as well as
system blowers, are automatically controlled whenever the temperature
and humidity of the charging air, as evidence by arrow 42 is suitable
for drying the material in any one of the bins 10 20 30 etc.
The hot, low humidity air 42 passes through the supply duct portion
40b, gate valve 11 storage bin 10 and over the desiccant material,
such as silica gel M, and exits through gate valve 12 through charging
circuit return duct 45 for discharge as at 46. While passing through
the silica gel desiccant material M in bin 10 it picks up moisture
from the storage material and becomes cooler and retains more water
vapor than when it enters the bin. Since water vapor would deter
the process if circulated back through the heat source 49 it is
discharged to the atmosphere at 46. However, some of the retained
heat is preferably recovered by use of the regenerative heat exchanger
47 which couples supply duct portion 40a and return duct portion
45b of the charging circuit.
When the charge in bin 10 has reached its highest practical value
for current conditions in supply duct 40 the gate valves 11 and
12 are closed to seal the dry material for storage within storage
bin 10 without further losses until the stored energy is needed
under demand as determined by the withdrawal circuit. The withdrawal
circuit includes means for selectively withdrawing energy from the
bin having the highest indicated charge, with the bin having the
lowest indicated charge being selected for charging; for instance,
bin 20 in which case, gate valves 21 and 22 are open with gate
valves 23 and 24 closed and permitting dry air from the heat reclaim/solar
collector 49 to dry the silica gel stored within storage bin 20.
The system is said to operate such that heat is charged within the
bins having the lowest charge at the time, and heat is delivered
from the one having the highest charge. Turning to the withdrawal
circuit, its principal duct components are the withdrawal circuit
supply duct 53 and the withdrawal circuit return duct 52. The withdrawal
circuit return duct 52 is provided with a first duct portion 52a
which includes a branch portion opening to the storage bins through
the lower walls 4 and carrying withdrawal circuit return duct gate
valves: 13 for storage bin 10 23 for storage bin 20 and 33 for
storage bin 30. Further, the return duct 52 of the withdrawal circuit
is provided with a second duct portion 52b which is open at one
end 103 to the outside with air as a source of gas to be directed
under pressure through the storage bin for heating by way of giving
off its moisture to the very dry desiccant material M with a selected
storage bin which has been previously charged. Thus, when energy
is to be withdrawn, depending on whether hot, cool or dry air is
desired at the output, air from a suitable source, such as outside
air via opening 103 of return duct section 52b is drawn into duct
52 by a blower 51 which forms a portion of the withdrawal circuit
supply duct 53 and the given bin that is open for energy withdraw.
For instance, if bin 30 which is fully charged, is to supply thermal
energy, it is necessary that valves 31 and 32 be closed for that
bin and that valves 33 and 34 be open to permit the air to pass
from duct 52 to duct 53. The air gives up some of its moisture to
the dry storage material M within bin 30 becoming hotter and dryer,
while the storage material M becomes wetting in giving up some of
its stored energy. The air, in giving up moisture, becomes hotter,
and as long as the material in the bin 30 is dry enough for the
purpose at hand, withdraw continues from that bin. Another bin,
such as bin 10 or 20 having the next highest charge at the time,
will be switched in when bin 30 is exhausted. The employment of
more than two bins is advantageous in flexibility while storing,
charging or withdrawing.
When the object of heat withdrawal is for drying, such as for drying
clothes, paint finishes, hay, seeds or any other similar process,
the hot, dry air may be withdrawn from duct 53 through inclined
duct 55 as evidenced by arrow 56 by selective control of a flap
or gate valve as at 55a.
The system of the present invention, in the illustrated embodiment,
is directed primarily to maintaining desired temperature conditions
within the room R. In this case, the withdrawal circuit further
comprises a supply duct 54 at the discharge side of blower 51 which
opens to a heat exchange chamber 63. Chamber 63 carries a counterflow
heat exchange coil 61 such that where the dryness of the air is
not a factor and it is preferred simply to extract free heat from
the storage and to supply it to the room being conditioned, the
coil 61 is employed. In this respect, the room R is connected by
way of ducts 104 and 105 to bypass duct 106 the duct 106 incorporating
a heat exchange coil 64a within the same. The heat exchange coil
64a is pipe connected to heat exchange coil 61. Coils 61 and 64a
are directly connected such that the heat extracted from the air
flow within duct 54 leading from the storage bin is transmitted
to the air circulated to and from the room R through duct 106. Pipe
108 leads from the counterflow heat exchange coil 61 to the room
heat exchange coil 64a via pipe 109 within which a control valve
110 is located for controlling the flow of a working fluid between
these heat exchange coils. Alternatively, a second valve 111 within
pipe or line 108 downstream of line 109 may be open while valve
110 is closed to permit the hot working fluid to be delivered to
some other end-use device or processing equipment, as indicated
by arrow 94. A pipe or line 112 leads from the room heat exchange
coil 64a to the hot end of a third counterflow air preheat exchange
coil 68 mounted within the withdrawal circuit return duct portion
52b upstream of the air inlet 103. Line or pipe 113 leads from the
cold end of that counterflow heat exchange coil to the cold end
of the counterflow heat exchange coil 61 of heat exchange chamber
60 with coils 61 64a and 68 being in a closed series loop. A pump
66 may be incorporated within line 113 to effect positive pressure
flow of the working fluid within that closed loop. Thus, after most
of the heat is depleted from the working fluid within the room heat
exchanger, heat exchange coil 64a, the still warm fluid passes through
pipe 112 to the heat exchange coil 68 and thereby extracts as much
heat as possible from the hot air within the supply duct 53 of the
withdrawal circuit.
When the outside air humidity is not high enough to extract sufficient
heat from the desiccant to carry the thermal demand, it is preferred
that environmentally warm water is sprayed into the input air before
it passes over heat exchange coil 68. In that regard, a spray nozzle
indicated at 99 effects the spraying of water on the incoming outside
air, as indicated by arrows 114. Up to 500 BTU's may be extracted
from a fully charged storage bin for each pound of desiccant material
within that storage bin.
The illustrated embodiment permits selective cooling to be achieved
for the space to be conditioned or for other space at the same time
that heat is being withdrawn for a useful purpose. In that respect,
in duct 54 downstream of the heat exchange chamber, the water spray
71 sprays water as at W onto the air flowing from the heat exchange
coil 61 and towards the discharge end 115 of duct 54. Duct 105 intersects
duct 54 and is provided with a flap valve 98 which is maintained
either in the dotted-line or full-line position. When in the full-line
position, the cool air is discharged from end 115 of duct 54 as
indicated by arrow 6 and may be employed for refrigeration purposes,
for booster cooling of a mechanical absorption refrigeration condensor
to take some of the load off the compressor during peak load period
on the utility line, or for any process needing cooling below ambient
temperature.
When the flap valve 98 is in the dotted-line position, the cool
air may be directed to the room or space R to be conditioned. Under
such conditions, it is preferred that valve 110 is closed and valve
111 open so that there is no simultaneous heating and cooling of
the room, heat exchange having been terminated within the room heat
exchange coil 64a by closure of valve 110. Under such conditions,
the hot working fluid within line 108 passes to an end-use device
and fresh make-up water must be provided, as indicated by arrow
95 to pipe 113 at point 116 for passage to the counterflow heat
exchange coil 61 within heat exchange chamber 62.
During those periods when heat from the withdrawal circuit is not
needed, the heat may be dissipated to the environment as when valve
98 is closed, arrow 6 to passage 105.
The withdrawal circuit is further provided with a return duct portion
52c which constitutes an extension of the duct 104 leading from
the room to duct 106 duct portion 52c intersecting duct portion
52a commonly with duct portion 52b. At this point, there is provided
a flap valve 91 which may take the full-line or dotted-line position.
In the dotted-line position, outside air is cut off to the withdrawal
circuit, and air returning from cooling of the room R which has
an advantage over temperature and humidity of the outside air is
returned to the bins, whereby a portion of its moisture is given
up to the charged desiccant material, with the air being heated
and returned to the heat exchange chamber 62. No water spray or
vapor need be added to this recirculated air because of the humidity
provided to the same during evaporative cooling within the spray
chamber 70.
The system is highly versatile and permits refrigeration down to
the near freezing point with little additional loss in efficiency
of withdrawal because the return air will be boosted each time it
passes through the desiccant, cooling and humidifying cycle. Such
moist storage, resulting from psychometric cooling will be far better
for refrigeration and storage of lettuce and other vegetables because
it would have no tendency to dry out leaves and delicate skins of
sensitive plants, such as normally occurs by air cooled by evaporative
coils or mechanical refrigeration. Cut flowers would fair much better
in such refrigerated air whose humidity may be maintained near the
100% level.
From the above, it is readily apparent that the thermal energy
storage heating and cooling system of the present invention is of
a simplified and compact nature. In addition to returning heat as
desired, dry air may be provided for various processes, and conversion
of the heated air to cooling can be achieved with little additional
equipment and with minimal loss of energy as compared to common
conversion methods. Small volume storage may hold many times as
much energy as thermal storage using water, and the weight compared
to water is almost as favorable as its volume ratio. One cubic foot
of activated aluminate weighs only about 50 pounds compared to 64
pounds for water, and it holds roughly 18000 BTU's. The temperature
of water correspondingly would have to be raised to around 300.degree.
F. to match the properties of activated aluminate. Loose stones
would have to be heated to at least 600.degree. F. to store a comparable
amount of heat. Where the desiccant comprises silica gel which weighs
about 40 pounds per cubic foot and can hold up to 24000 BTU's,
the advantages of the present system can be readily appreciated,
particularly since the silica gel may be stored in a charged condition
without thermal insulation at any temperature without loss.
Additional advantages reside for thermal energy storage during
cold whether since the desiccants can collect energy at any temperature,
and once dried can translate that advantage to an entirely different
range of temperatures to release their stored energy. As an example,
on a day when it is only moderately sunny and where the outside
temperature is about 0.degree. F. and the collector 49 can only
get a rise of 90.degree. without operating inefficiently, it has
little advantage for storing usable heat in conventional thermal
storage. However, with the desiccant system of the present invention,
the collector can be run at a somewhat more efficient temperature
of around 60.degree. and still dry the desiccant material M to its
maximum. After a storage bin is charged by drying and is sealed
by closure of the gate valves, the cold outside temperature does
not deplete the charge because it is not in the form of sensible
heat. At the time of withdrawal of energy, the outside air is drawn
in, is sprayed with the warmest environmental water available and
the moistened air with possible ice crystals is passed over a heat
exchanger to warm it to near room conditions as by heat exchange
coil 68 and then it is passed into the storage bin to give up its
moisture and to be heated. The heating from the storage starts from
the temperature of the input air so it is relatively easy to obtain
temperatures above 100.degree. F. Further, almost the full charge
of any one of the bins may be withdrawn within the temperature range
of the space or device to be heated, such as room R.
Temperatures below ambient may be developed down to near the depression
of the desiccant by cooling the gas coming out of storage to the
ambient temperature with one heat exchanger, exposing the partially
cooled gas to evaporative cooling and passing the spent cooling
back into storage for drying and heating again through a second
heat exchanger.
While the illustrated embodiment employs blowers for the forced
circulation of a gas, such as air, through both the charging and
withdrawal circuit, it is obvious that such positive flow devices
may be replaced by thermal siphon means or the like. Further, while
gate valves are employed for selectively closing off and sealing
the storage bins to respective supply and return ducts for the charging
and withdrawal circuits, alternative devices may be employed.
While the invention has been described with reference to a preferred
embodiment thereof, it will be understood by those skilled in the
art that various changes in form and details may be made therein
without departing from the spirit and scope of the invention. |