Solar heat collection and storage system

A closed solar energy collection and storage system comprising one or more solar heat collector units in parallel, feed and return headers at lower and upper levels at the opposite ends thereof, a liquid storage tank at a level below said units, a circulating pump connected to said tank, a first conduit between said pump and the lower feed header, a second conduit extending downward from said upper return header into said tank, a return vent extending from said upper return header to the top of said tank for passage of air or gas or steam thereto from said collector or tank to receive and condense steam or vapor received therefrom and return the condensate to said tank.

BACKGROUND OF THE INVENTION 
The present invention primarily is concerned with providing a solar heat 
collection and storage system which is closed and is provided with means 
to effectively deal with various conditions of the liquid which primarily 
is stored in a storage tank and which is also heated by one or more solar 
heat collecting units interconnected with said storage tank. On occasions, 
particularly when the system for heating the interior of a closed space, 
such as a dwelling or otherwise, does not lower the temperature of the 
liquid in the storage tank to such extent that it requires additional 
heating by the solar collecting units, said units, in the meantime, will 
be exposed to substantial solar heat. Under such conditions, liquid from 
the storage tank, upon passing to such heating solar heat collecting 
units, frequently is at least partially transformed into steam and said 
steam, together with heated liquid is circulated through the system and is 
transmitted back to the storage tank by appropriate conduits. 
At least a few previous attempts have been made to transmit steam from 
solar heat collector units back to a storage tank, one such example being 
illustrated in U.S. Pat. No. 4,044,949 to Morawetz, dated Aug. 30, 1977. 
Said system is a so-called closed system and several examples of closed 
systems per se are illustrated in applicant's prior U.S. Pat. No. 
2,342,211, dated Feb. 22, 1944, and his more recent U.S. Pat. No. 
4,114,600, dated Sept. 19, 1978. In the latter patent, there is a 
disclosure of means to handle inert gas developed in the system and passed 
from the solar heat collectors to the storage tank but neither this patent 
nor the Morawetz patent include any means for specifically and effectively 
condensing steam or vapor developed in the system under the 
above-described circumstances and it is the principal purpose of the 
present invention to provide an effective means for condensing such steam 
or vapor and otherwise providing improvements over the systems found in 
said aforementioned patents, as well as other similar art. 
SUMMARY OF THE INVENTION 
It is among the principal objects of the present invention to provide a 
closed solar energy collection and storage system in which one or more 
collector units are provided at opposite ends with feed and return headers 
respectively connected to lower and upper levels of said collector units 
and in particular provide a return conduit extending downwardly from the 
upper return header primarily for delivering heated liquid into said tank 
and, in addition, provide a return vent also extending from the upper 
return header to the top of the storage tank for passing air and/or steam, 
as well as any other vapor separately to the upper portion of the storage 
tank and delivering it preferably above the liquid level therein, whereby 
the liquid and air or steam are delivered separately to the upper portion 
of the storage tank from the upper return header of the solar heat 
collector units. 
Another object of the invention is to provide an improved separator unit in 
conjunction with said upper return header and downwardly extending return 
conduit and said return vent to facilitate the separation of air and steam 
from the liquid. 
A further object of the invention is to provide condensating means operable 
relative to the upper portion of the storage tank to receive concdensable 
gaseous matter, including steam, and condense the same for return to the 
liquid in the tank. 
Still another object of the invention is to provide in the upper portion of 
the storage tank a spray device connected by suitable conduit means to the 
main body of liquid in the storage tank and including a pump operable to 
deliver liquid from said tank to the spray device in the upper portion 
thereof and thus facilitate the cooling of gases and air delivered thereto 
from the upper return header of the solar heat collecting units, said pump 
being in addition to the primary circulating pump which forces liquid from 
the storage tank to the feed header connected to the solar storage 
collector units. 
Still further improvements comprise the provision of various sensing 
controls for initiating operation of the aforementioned spray device 
and/or the condensing system, whereby operation of such closed system is 
rendered automatic and foolproof. 
One further object of the invention is to provide a breather conduit 
connected to the top of a storage tank for passage of air or other gases 
to and from said tank above the liquid level therein as the volume of air 
or other gases varies and said breather conduit being connected to a 
collector which is operable to receive any liquid passing through said 
breather conduit and including means to return said liquid to the tank and 
said breather conduit also being associated with means to prevent the 
inlet of ambient air or atmosphere to the system. 
Still another important object of the invention is to provide a liquid and 
gaseous separator between the return conduit and the downwardly extending 
liquid return conduit and vent for gas and steam, said separator being so 
constructed as to initially separate steam and gaseous matter from the 
liquid but, when said steam and any other gaseous matter has been 
exhausted from the return header, liquid may thereafter pass through the 
vent and be delivered thereby into the upper part of the storage tank, 
together with other liquid delivered thereto by the liquid conduit, 
thereby imposing a pull by gravity upon such discharging liquid to 
facilitate the operation of the circulating pump which delivers liquid 
from the tank to the feed header for the solar collector unit. 
One further object ancillary to the foregoing object is forming said 
separator from relatively simple means comprising a tee in which the stem 
is disposed horizontally and the head is vertical, said stem being 
connected to the delivery end of the return header from the solar 
collector units and the liquid discharge pipe being connected to the lower 
end of the vertically disposed head of the tee, the upper end of the vent 
for gas and steam also extending upward through said vertical head of the 
tee and terminating at a level above the inlet of the stem of the tee, 
said upper end of the tee also being closed but spaced from the upper end 
of said vent. 
Still another object of the invention is to provide a modified circuit for 
the return of gas or air to the upper return header from a receiving 
compartment connected with the condensing unit rather than from the space 
above the liquid level in the storage tank and thereby minimize the 
inclusion of any appreciable amount of steam or water in such returning 
gas or air which could be frozen in the collector in freezing temperature 
conditions. 
One further object of the invention is to provide a second embodiment of 
fitting for said separator which facilitates the connection of conduits 
thereto. 
Details of the foregoing objects and other objects, as well as the 
invention, are set forth in the following specification and illustrated in 
the accompanying drawings comprising a part thereof:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The closed solar energy collection and storage system comprising the 
present invention is illustrated primarily in FIG. 1. In said figure, 
there is illustrated a plurality of solar heat collector unit 10, which 
respectively include sinuous coils 12, through which fluid, and 
particularly water, for example, circulates for purposes of being heated 
by solar energy. Said units include a frame 14 within which the coils 12 
are mounted and, as seen from FIG. 2, it is conventional to mount said 
units at an angle to the horizontal and one such exemplary angle is shown 
in said figure. 
The system also includes a storage tank 16 of substantial volume, which is 
shown in vertical section in FIG. 1, and it will be understood in view of 
the break-away regions shown in FIG. 1 that the preferred arrangement of 
the system includes the positioning of the solar heat collector units 10 
mounted in vertically spaced relationship with respect to the tank 16, and 
usually at a very substantial distance above said tank. Said tank contains 
the liquid 18 that is heated by solar energy passing through the coils 12 
of the units 10. For purposes of such circulation, the lower ends of the 
coils 12 are connected commonly to a horizontal feed header 20 and the 
upper ends thereof are connected commonly to a return header 22. For 
purposes of effecting substantially even flow from the various units 10 to 
these headers, the same are provided with appropriate reducing steps 24 
adjacent the connection of the coils 12 of the left-hand collector unit 10 
to said headers. Outlet conduit 26 communicates at one end with the lower 
portion of tank 16 and leads to a first pump 28, said pump having a first 
delivery conduit 30 extending therefrom to the feed header 20 for purposes 
of delivering liquid 18 from the storage tank 16 to said feed header. 
The return header 22 communicates with a fitting 32 which actually 
comprises a tee, the stem 34 of said tee 32 being connected to the 
discharge end of return header 22, while the head 36 of the tee 32 extends 
vertically and the lower end 38 of the head 36 is connected to the upper 
end of a second conduit 40, the lower end of said conduit being connected 
to the upper end of a Z-shaped fitting 42. The upper end of the head 35 of 
tee 32 extends to a level above the return header 22 and is closed by a 
suitable closure 44 which preferably is dome-like. 
Within the upper portion of the head 36 of tee 32, a spider 46 is fixedly 
connected for purposes of supporting the upper end of a vent tube 48 which 
extends vertically downward through the second conduit 40 and also passes 
in sealed relationship through an opening 50 in the fitting 42. The upper 
end 52 of the vent tube 48 comprises the inlet end of said vent tube and 
said vent tube extends downward, alongside an extension return conduit 54, 
the lower end portion of said extension return conduit 54 passing through 
an appropriate opening in the top 56 of tank 16, the lower end of vent 
tube 48 also extending through an appropriate opening in said top 56 of 
the tank, preferably in close proximity to the conduit 54. Conduit 54 also 
is known in the art as a downcomer and the conduit 54, as well as vent 
tube 48 are disposed within an enclosure 58, which is filled with heat 
insulating material 60, the enclosure 58 preferably resting at its lower 
end upon the top 56 of tank 16, as clearly shown in FIG. 1. 
Control of the circulation of liquid 18 within the system primarily is 
effected by differential temperature control unit 62, which is illustrated 
adjacent the left-hand heat collector unit 10 and a sensing element 64 is 
disposed within said left-hand unit 10 and is also connected to the 
control unit 62, as clearly shown diagrammatically. An additional sensing 
unit 66 is disposed in the upper portion of tank 16 and it also is 
connected to control unit 62, as shown diagrammatically in FIG. 1. A still 
further sensing element 68 is mounted within the interior of tank 16 and 
extends to an additional control unit 70 exteriorly of said tank and the 
same also is connected by a circuit to the differential temperature 
control unit 62, as likewise is shown in FIG. 1. 
In the preferred operation of the system, the level of liquid 18 in tank 10 
is below the top 56 of the tank, whereby a space 72 is present in the tank 
above the liquid level. The circuit between the additional control units 
70 and first pump 28 includes a timer 74 having adjustable settings, the 
purpose of which is described hereinafter. 
Operation of the pump 28 is controlled by the differential control unit 62, 
operation of the pump occurring when the sensor 64 in the heat collector 
unit 10 is at a predetermined amount above the temperature of the liquid 
in storage tank 16, as determined by sensor 66. Pump 28 is stopped 
whenever the differential temperature falls below a predetermined minimum 
as measured by the sensors 64 and 66 which cause the control unit 62 to 
operate. Pump 28 also is prevented from operating whenever the storage 
temperature exceeds a predetermined maximum, such as, for example, 
203.degree. F. (95.degree. C.), as determined by still further sensing 
element 68, mounted within tank 16 and connected to an additional control 
unit 70 which also is connected to the differential temperature control 
unit 62 and measures storage temperature by means of said sensing element 
68. 
When pump 28 stops, liquid returns through the pump to drain the upper 
return header 22, as well as the collectors 10 and feed header 20 and the 
first delivery conduit 30. During this time, the space 72 above the fluid 
18 in storage tank 16 is vented by tube 48 to header 22, whereby rapid 
draining of the aforementioned connected elements can occur, due to air or 
gas from space 72 filling the headers 20 and 22 and collectors 10. 
From FIG. 1, it also will be seen that vent line 48 is in close proximity 
or actually may be in contact with extension return conduit 54, which, 
incidentally, is known in the art as a downcomer. 
Upon re-starting pump 28, following the draining of the system as described 
immediately above, sufficient head must be developed by the pump to fill 
the delivery conduit 30, feed header 20, the collectors 10 and return 
header 22, and this may be accomplished either by choosing a pump with a 
steep curve of head vs. flow or by running the pump 28 at a high speed for 
the required fill time, as determined, for example, by aforementioned 
timer 74, which is connected in the control circuit for the pump as shown 
in FIG. 1 and then reverting to normal speed of the pump. During such 
refilling of the system, air is vented from all of the connected elements 
recited above through the vent tube 48 and into the space 72 in tank 16. 
If, before refilling the system, the collectors 10 have stagnated and are 
sufficiently hot from absorbed solar heat that steam is generated incident 
to passing liquid through said collectors, said steam passes through 
return header 22 through the vent tube 48 and into space 72 above the 
liquid in tank 16. The differential control unit 90 senses the steam 
temperature above some predetermined minimum amount in vent tube 48, such 
as 203.degree. F. (95.degree. C.), and starts operation of a second pump 
76, which communicates with the lower portion of tank 16, as shown in FIG. 
1 and forces said cooler liquid through delivery conduit 78 to a 
temperature-reducing device 80, which is in the form of a perforated tube 
82 and comprises a spray which tends to condense the steam and the 
condensate falls into the liquid 18 in tank 16. If the steam is not 
entirely condensed, any excess is vented from space 72 through conduit 84 
to a condensing unit 86, which, as illustrated in FIG. 1, comprises a 
finned coil, for example, and an additional sensor 88, which is connected 
to a further temperature-responsive control unit 90, initiates operation 
of a cooling fan 92 to blow cooling air over the finned coil of condensing 
unit 86 and thereby, condensing steam passing therethrogh, the condensate 
from said unit 82 passing to an appropriate separator 94, which, in turn, 
is connected to downwardly extending conduit 96 for discharge of the 
condensate into the upper part of tank 16. 
The above-described condensing mechanism also is provided with a breather 
pipe 98 into which air from space 72 in tank 16 may pass by also moving 
through separator 94 as the volume of air in the space 72 changes. A 
closed receiving compartment 100 is connected to the discharge end of 
breather pipe 98 and any liquid which might accompany the air is permitted 
to be received in the compartment 100 and, by means of a return conduit 
102, passes back to the upper part of tank 16. Further, an appropriate 
means for preventing any intake of atmospheric air to the compartment 100 
is provided in the form of an exemplary expansible member, such as an 
appropriate balloon 104, or other suitable means, thereby insuring that 
the entire system is closed from beginning to end. 
Under the foregoing circumstances, after all steam has ceased to be 
generated, such as following a refilling of the collector units 10, as 
described above, and passes from the return header 22 and down the vent 
tube 48 into space 72 in the upper part of tank 16, the return system to 
tank 16 will be drained of steam, whereby continued flow of liquid from 
the return header 22 will fill the fitting 32 with liquid to such an 
extent that it will overflow into the upper end 52 of vent tube 48, 
whereby vent tube 48 also will carry liquid from the return header 22 in 
addition to the return conduit 54, thereby subjecting such returning 
liquid to the influence of gravity that places a pull upon such returning 
liquid incident to entering tank 16 and thus, facilitating the movement of 
such liquid in such manner that the operation of pump 28 may operate at 
its normal lower head circulation rate. Simultaneously, such returning of 
the liquid through the vent tube 48 and return conduit 54 causes the 
control unit 90 to stop the pump 76 and cooling fan 92. 
The general tapering of the feed and return headers 20 and 22, coupled with 
the reducing steps 24 limits the changes in velocity head to values in 
each section which prevent major differences in flow rate in individual 
collectors and also to retain similar velocity pressure ranges in each of 
the feed and return conduits. 
As indicated above, it is preferred that the collector units 10 be disposed 
at any angle, as indicated in exemplary manner in FIG. 2, in order to 
produce a head "h" and the feed header 20 is at the lower elevation, while 
the return header 22 is at the upper or higher elevation, as also shown in 
FIG. 1. If, during the filling of the collector units 10 in the manner 
described above, pressure drop and normal flow in the system is not equal 
to or greater than the head "h", additional resistance may be provided in 
the connectors 106 through which the coils 12 in the units 10 communicate 
with the feed header 20 in order to provide the required head to fill all 
headers simultaneously. Also, as a safety precaution, the lower end of 
return conduit 54 may be provided with a suitable vent hole 108 within the 
space 72 in the upper portion of the tank 16 to prevent trapping the flow 
of liquid through return conduit or downcomer 54 into tank 16. 
Referring to FIG. 1, it will be seen that vent tube 48 extends into space 
72 above the liquid level in tank 16, whereby when air or gas is vented 
through vent tube 48 to the headers 20 and 22 and collectors 10, it is 
conceivable that some water vapor can be entrained in the air or gas thus 
vented and when said headers and collectors are exposed to freezing 
temperatures, freezing of such vapor in this portion of the system can 
occur. Hence, to at least minimize but preferably prevent such occurrence, 
attention is directed to FIG. 3 in which additional passage and control 
means are illustrated for the following purposes. 
In FIGS. 3 and 4, it will be seen the lower end of vent tube 48 has been 
arranged to be subjected to control by a check valve 110 which has been 
illustrated as a simple resilient leaf spring, to represent any suitable 
type of check valve, which will normally be closed but readily capable of 
being opened to permit passage of air or gas into space 72 of tank 16, as 
when the collectors 10 are being filled by pump 28, see FIG. 1, drawing 
liquid from tank 16 for that purpose. Similarly, liquid flowing from the 
return header 22 into fitting 32 until it fills it will discharge liquid 
down vent tube 48 into tank 16 in a manner to hold said check valve open. 
Under neither of these situations, however, will backflow occur through 
the check valve 110. 
In order that venting of air or gas to the headers 20 and 22 and collectors 
10 can occur when necessary, the modified arrangement illustrated in FIG. 
3 includes an additional bypass vent tube 112 which extends between 
receiving compartment 100 and vent tube 48 midway of its length, as 
clearly shown in FIG. 3. Due to the fact that compartment 100 normally is 
colder than tank 16, it contains minimum water vapor because of free 
drainage of condensate through return conduit 102 to tank 16 and 
therefore, air or gas drawn from compartment 100 will have a minimum of 
water vapor in it, if any at all, and the air therefrom when in the 
headers 20 and 22 or collectors 10, will present no freezing problems of 
the type referred to hereinabove. The temperature of the liquid in tank 16 
in winter will vary during the season and with geographic location but, 
for example, it normally will be substantially greater than room or 
ambient outdoor temperatures. In typical installations, the maximum 
temperature of liquid in tank 16 during winter will range, for example, 
from 130.degree. F. to 185.degree. F. among various installations. 
The operation of the system as just described results in much less water 
vapor entering the collectors than if the gases to refill them are drawn 
from the space above the water within the main storage tank 16. This is 
illustrated by the following table which shows the weight in pounds of 
water vapor in saturated air per cubic foot at various temperatures: 
______________________________________ 
Temperature Lbs. Water Vapor/cu. ft. 
______________________________________ 
80F 0.00124 
120F 0.00412 
140F 0.00678 
155F 0.01038 
186F 0.021429 
______________________________________ 
Thus, in geographic areas in which freezing temperatures occur, and if the 
storage temperatures during freezing conditions are likely to go above 
155.degree. F., for example, the arrangement in FIG. 3 is preferable since 
the temperature in compartment 100 is usually approximately the same as 
room temperature, and hence, will be close to 80.degree. F. Normally, the 
time interval between drainage of the collectors and a re-start of the 
system is usually several hours, and therefore, even if compartment 100 
shoud be warmed during drainage, its temperature would, nevertheless, 
approach room temperature before re-starting. Additional check valve 128, 
shown in FIG. 3, prevents backflow and is optional. 
Referring to FIG. 4, an alternative type fitting for the fitting 32 in 
FIGS. 1 and 3 is shown for purposes of eliminating the second conduit 40 
and Z-shaped fitting 42. The alternative fitting 114 is a casting 
comprising a modified tee in which the stem 116 is horizontal to 
connectably receive one end of return header 22. The head 118 is vertical 
and the upper end has a cap 120 threaded thereinto, the lower end of the 
cap having a spider 122 which receives and supports the upper end of vent 
tube 48 at a level above stem 116 and header 22. The lower end of the head 
118 has a pair of suitable outlet ports, the port 124 connectably 
receiving the upper end of vent tube 48 and the port 126 threadably 
receiving the upper end of extension return conduit 54, whereby the second 
conduit 40 and Z-shaped fitting 42 are eliminated. 
The foregoing description illustrates preferred embodiments of the 
invention. However, concepts employed may, based upon such description, be 
employed in other embodiments without departing from the scope of the 
invention. Accordingly, the following claims are intended to protect the 
invention broadly, as well as in the specific forms shown herein.