U.S. patent application number 10/968137 was filed with the patent office on 2005-04-28 for system for heating liquid by solar radiation.
Invention is credited to Stahl, Per Ingemar.
Application Number | 20050087186 10/968137 |
Document ID | / |
Family ID | 29775108 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050087186 |
Kind Code |
A1 |
Stahl, Per Ingemar |
April 28, 2005 |
System for heating liquid by solar radiation
Abstract
A system for heating liquid using solar radiation, includes a
plurality of solar panels (1, 2, 3, 4, 5), at least one reservoir
for heated liquid and pipes for circulating liquid between the
respective solar panel and the at least one liquid reservoir, the
liquid circulating by gravity circulation. The present system is
characterised in that a non-return valve (17) for controlling the
flow of heated liquid from the respective solar panel is placed in
a portion of the circulation pipe between the upper end of the
solar panel and the at least one liquid reservoir, the non-return
valve (17) being adapted to open and close at a predetermined
pressure in the liquid flow from the solar panel.
Inventors: |
Stahl, Per Ingemar;
(Gjerdrum, NO) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET
2ND FLOOR
ARLINGTON
VA
22202
US
|
Family ID: |
29775108 |
Appl. No.: |
10/968137 |
Filed: |
October 20, 2004 |
Current U.S.
Class: |
126/640 ;
126/651 |
Current CPC
Class: |
Y02E 10/40 20130101;
F24S 60/30 20180501; Y02B 10/20 20130101; F24S 90/10 20180501 |
Class at
Publication: |
126/640 ;
126/651 |
International
Class: |
F24J 002/04 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 22, 2003 |
NO |
20034725 |
Claims
1. A system for heating liquid by solar radiation, comprising a
plurality of solar panels (1, 2, 3, 4, 5), at least one reservoir
(6) for heated liquid and pipes (7, 8; 9, 10, 11) for circulating
liquid between the respective solar panel and the at least one
liquid reservoir, the liquid circulating by gravity circulation,
characterised in that a non-return valve (17) for controlling the
flow of heated liquid from the respective solar panel is located in
a portion of the circulation pipe between the upper end of the
solar panel and the at least one liquid reservoir, the non-return
valve (17) being adapted to open and close at a predetermined
pressure in the liquid flow from the solar panel.
2. A system according to claim 1, characterised in that the
non-return valve (17) comprises a valve seat (18; 37) with a
central fluid opening, a movable float body (19; 33, 34) for
opening and closing the fluid opening and a spindle (20; 35) for
controlling the movement of the float body.
3. A system according to claim 2, characterised in that the float
body is in the form of a thin disc (33) that has an outer element
(34) of greater thickness, the thickness of the element being
variable.
4. A system according to claim 1, characterised in that the at
least one liquid reservoir (6) has a large height relative to its
dimensions in cross-section.
5. A system according to claim 1, characterised in that the
circulation pipes for the liquid form part of a flow circuit that
is open to the respective liquid reservoir, and which consists of
flow channels (21) in the respective solar panel and pipes (7, 8)
which respectively convey the liquid from the upper end of the
solar panel to the upper end of the liquid reservoir and back from
the lower end of the liquid reservoir to the lower end of the solar
panel.
6. A system according to claim 1, characterised in that the
circulation pipes for the liquid form part of a flow circuit that
is closed to the respective liquid reservoir, and which consists of
flow channels (21) in the respective solar panel and pipe sections
(9, 10, 11) which respectively convey the liquid from the upper end
of the solar panel, through the respective liquid reservoir and
back to the lower end of the solar panel.
7. A system according to claim 1, characterised in that at least
two solar panels (1, 2) are joined together along their adjacent
lateral edges (12, 14) and their outer, free lateral edges (13, 15)
are positioned in such relationship to each other that a space can
be formed between the solar panels for accommodating the at least
one liquid reservoir and the circulation pipes.
8. A system according to claim 7, characterised in that the upper
end of the solar panels (1, 2) that form the side walls of the
formed space slant downwards in the direction of the joined lateral
edges (12, 14) and are covered by a solar panel (3) placed on top
of the joined solar panels.
9. A system according to claim 1, characterised in that a solar
panel (4, 5) extends out from and is joined to the free lateral
edge (13, 15) of the respective joined solar panels (1, 2).
10. A system according to claim 1, characterised in that at least
one sunlight reflector (16) is placed directly on and/or at a
distance from the solar panel or panels in question.
Description
[0001] The present invention relates to a system for heating liquid
by solar radiation, comprising a plurality of solar panels, at
least one reservoir for the heated liquid from the solar panels and
pipes for circulating liquid between the respective solar panel and
the at least one liquid reservoir. More specifically, the invention
relates to such a system wherein the liquid circulates by gravity
circulation.
[0002] There are already many systems involving the use of one or
more solar panels to harness solar radiation for heating a liquid,
such as water for domestic use. Two different systems of this type
are taught in EP Patent No. 0114005 and U.S. Pat. No.
4,685,445.
[0003] According to EP Patent No. 0114005, the reservoir for heated
liquid is mounted at a level higher than that of the solar panel
and a pump provides circulation of the liquid between the reservoir
and the panel. Furthermore, a separate device in the form of a
tubular body, located in the flow circuit between the solar
collector and the liquid reservoir, is used for correct orientation
of the flow of liquid.
[0004] The system according to U.S. Pat. No. 4,685,445 differs from
the aforementioned solution in that it uses gravity circulation for
circulating heated liquid. This means, among other things, that the
pump is omitted and the liquid reservoir is mounted level with the
solar panel. However, the prerequisite for correct liquid flow is
that the flow circuit pipes connecting the solar panel and the
liquid reservoir are arranged in a very specific manner.
[0005] Furthermore, U.S. Pat. No. 4,782,816 and SE Patent No.
510601 disclose solutions where several solar panels are assembled
to form a closed space, e.g., for accommodating circulation pipes
and other necessary equipment.
[0006] The main object of the present invention is to provide a
system that has a compact and efficient structure and that has a
shortest possible path for the liquid circulation pipes and fewest
possible components connected thereto. This main object is obtained
by a system of the type mentioned in the opening paragraph, and
which is characterised in that a non-return valve for controlling
the flow of heated liquid from the respective solar panel is
located in a portion of the circulation pipe between the upper end
of the solar panel and the at least one liquid reservoir, the
non-return valve being adapted to open and close at a predetermined
pressure in the liquid flow from the solar panel.
[0007] Since the pressure in the system varies depending upon the
temperature reached at any given time during the solar collection,
i.e., the pressure increases when the temperature rises and vice
versa, it is the pressure difference in the liquid that the float
body in the non-return valve responds to in order to open and close
the valve respectively.
[0008] In this way, correct flow of heated liquid from the
respective solar panel is ensured by the non-return valve, which
may comprise a valve seat with a central fluid opening, a movable
float body for opening and closing the fluid opening and a spindle
for controlling the movement of the float body. In a preferred
embodiment, the float body is in the form of a thin disc which has
an outer element of greater thickness, and the thickness of the
outer element can be varied according to the liquid in the system.
Furthermore, the at least one liquid reservoir in the system
preferably has a large height relative to its dimensions in
cross-section.
[0009] The circulation pipes for the liquid in the system may be
part of a flow circuit which is open to the respective liquid
reservoir, and which consists of flow channels in the respective
solar panel and a pipe which respectively conveys the liquid from
the upper end of the solar panel to the upper end of the liquid
reservoir and back from the lower end of the liquid reservoir to
the lower end of the solar panel. This allows heated water and
make-up water respectively to be taken from and supplied directly
to the at least one liquid reservoir. Alternatively, the
circulation pipes for the heated liquid may be part of a flow
circuit that is closed to the respective liquid reservoir, and
which consists of flow channels in the respective solar panel and
pipe sections which respectively convey the liquid from the upper
end of the solar panel, through the respective liquid reservoir and
back to the lower end of the solar panel. In this alternative, the
liquid in the system may advantageously be anti-freeze solution,
oil, alcohol etc. instead of water.
[0010] In the present system at least two solar panels can be
joined to each other along their adjacent lateral edges, whilst
their outer, free edges are positioned in such relationship to each
other that a space is formed between the solar panels for
accommodating the at least one liquid reservoir and the circulation
pipes. The upper end of the solar panels that constitute the side
walls of the formed space may slant downwards in the direction of
the joined lateral edges and be covered by a solar panel placed on
top of the joined solar panels. Furthermore, the collection of
sunrays can be increased by mounting a solar panel on the upper end
edges of the solar panels that form the space for accommodating the
reservoir and circulation pipes, and/or two additional solar panels
which each extend outwards from and are connected to the free
lateral edge of the respective joined solar panels. Making the
upper end of the solar panels that constitute the side walls of the
formed space slant downwards in the direction of the joined lateral
edges will enable more of the sunlight to pass over the central
solar panels and fall onto the additional solar panels.
[0011] The efficiency of the system can be further increased by
placing at least one sunlight reflector directly on and/or at a
distance from the solar panel or panels in question.
[0012] The use of a non-return valve in at least the upper portion
of the circulation circuit close to the respective solar panel thus
ensures that only solar panels with the desired liquid temperature
deliver to the liquid reservoir and prevents solar panels with too
low a temperature from "stealing" energy from the active solar
panel in the system. The circulation and compactness of the system
is further enhanced by the use of at least one liquid reservoir
that has a large height relative to its dimensions in
cross-section, and which is located in close proximity to the solar
panels, and also by the special arrangement of the solar
panels.
[0013] In addition, as particular advantages of the present
invention, brief mention should be made of the fact that the
atmospheric pressure inside the at least one reservoir provides
rapid circulation and also stable operation during the storage of
the heated liquid. The liquid delivered always has a high
temperature, even when the system is not fully charged, and the
system is scalable through adaptation to the size and shape of
and/or the number of solar panels. Moreover, the system is
inexpensive to manufacture as it has few components and the path of
the liquid flow circuit is short.
[0014] The invention will now be described in more detail with
reference to the preferred embodiments shown in the attached
drawings, in which:
[0015] FIG. 1 is a schematic lateral elevational view of a system
including a plurality of solar panels according to the
invention;
[0016] FIG. 2 is a schematic upper end view of the system shown in
FIG. 1;
[0017] FIG. 3 is a schematic illustration of a second embodiment of
the present system supplemented with a sunlight reflector mounted
directly on the solar panel;
[0018] FIG. 4 is a schematic detailed sectional view of an
embodiment of a flow circuit for circulating liquid between a
reservoir and the solar panels in the system shown in FIG. 1;
[0019] FIG. 5 is a schematic detailed sectional view of a second
embodiment of the flow circuit;
[0020] FIG. 6 is a vertical section of a non-return valve adapted
for controlling the liquid flow in the respective flow circuit;
[0021] FIG. 7 is a schematic upper end view of the non-return valve
shown in FIG. 6;
[0022] FIG. 8 shows a second embodiment of the non-return
valve;
[0023] FIG. 9 is a schematic elevational view of an embodiment
where the system according to the invention is integrated into the
facade of a house; and
[0024] FIG. 10 is a schematic upper end view of the system shown in
FIG. 9.
[0025] The present system for heating liquid uses conventional
solar panels, and the circulation between solar panels and liquid
reservoir takes place by means of so-called gravity flow, i.e.,
without the use of a pump. Although only one reservoir for heated
liquid from the solar panels is shown in the drawings, it will be
understood that the system can, when required, comprise more than
this one reservoir. The system is intended primarily for use in
heating water for domestic purposes in, for example, individual
dwelling units such as detached houses and holiday cottages,
swimming pools etc. Furthermore, the system can be positioned as an
independent unit in the surrounding landscape or integrated in a
suitable manner into the facade of the house itself. In conditions
of little sunlight, a constant temperature can be obtained in the
system in different ways, for example, by using electricity. The
system may also be equipped with a heat pump on the solar panels in
order to obtain a higher temperature in the liquid, e.g.,
water.
[0026] As shown in FIG. 1, a preferred embodiment of the system
according to the invention comprises two main solar panels 1, 2 and
three additional solar panels 3, 4 and 5. The main solar panels
consist of two upright solar panels that are joined together along
one of their lateral edges 12, 14. At the same time, their opposite
lateral edges 13, 15 are positioned in such relationship to each
other that a space is formed for accommodating a liquid reservoir
and a flow circuit for the liquid in the system, consisting of
separate pipes or pipe sections and flow channels in the respective
solar panel, as shown in FIGS. 4 and 5. One of the additional solar
panels 3 is placed on top of the upper end edges of the main solar
panels 1, 2 whilst the two other solar panels 4, 5 extend outwards
from and are each connected to a free lateral edge of the main
solar panels 1, 2.
[0027] The two upright main solar panels 1, 2 are set at an angle
of 90.degree. in this case, but this angle may of course be varied.
The use of more upright main solar panels is also possible, for
example, three which are so positioned that the foremost panel
extends parallel to the additional solar panels 4, 5, and the two
other panels extend backwards, either at right angles from or
oblique to the foremost upright solar panel. Alternatively, the
main solar panels may be curved, with two or more placed together
to form a space having a semicircular cross-section for
accommodating the liquid reservoir and the circulation pipes.
[0028] Making the upper edge of the two upright solar panels 1, 2
slant forwards in the direction of the joined lateral edges 12, 14
will enable more sunlight to fall onto the upright additional solar
panels, thus rendering the system more efficient. The output can be
further increased by mounting one or more sunlight reflectors in
connection with the present system, i.e., by up to 30% per
reflector. Each individual reflector 16 may be placed directly on
the solar panel in question, as shown in FIG. 3, or at a suitable
distance from the panel, for example, it can be placed directly on
the ground (not shown). The reflectors may optionally be
reversible, so that they can in a suitable manner be adjusted
manually or automatically according to the varying height and/or
position of the sun. The output of an independent system may be
enhanced by mounting upright solar panels on the rear side of the
additional solar panels 4, 5 and above the opening in the space for
accommodating, inter alia, the liquid reservoir 6.
[0029] The reservoir 6 for receiving the liquid that circulates in
the present system is of the upright type, having a large height
relative to its dimensions in cross-section, and is, as already
mentioned, located in the space formed behind the two upright main
solar panels 1, 2 which are joined to each other. As shown in FIG.
4, the liquid circulates in a flow circuit that comprises the
liquid reservoir 6 itself, and which otherwise consists of flow
channels 21 in the respective main upright solar panel 1, 2 and
separate pipes 7, 8 which respectively convey the liquid from the
upper end of the solar panel to the upper end of the liquid
reservoir and back from the lower end of the liquid reservoir to
the lower end of the solar panel. The flow circuit for each one of
the upright additional solar panels 4, 5 will have a similar
structure. Furthermore, the horizontal additional solar panel 3 has
a flow circuit consisting of the flow channels 21 therein and
separate pipes 23, 24, 25 running to and from the liquid reservoir
6. The different upper pipes 7, 23 and lower pipes 8, 24 may be
passed individually into and out of the liquid reservoir 6, or may
optionally be connected for common entry and exit.
[0030] In the alternative embodiment shown in FIG. 5, the flow
circuit is closed to the liquid reservoir 6, and consists of flow
channels 21 in the respective upright main solar panel 1, 2 and
pipe sections 9, 10, 11 which respectively convey the liquid from
the upper end of the solar panel, through the liquid reservoir and
back to the lower end of the solar panel. In this embodiment, the
flow circuit for the horizontal main solar panel 3 and the two
additional solar panels 4, 5 is conveyed in the same closed manner
through the liquid reservoir 6. The liquid from the different solar
panels can be conveyed though the liquid reservoir 6 by means of
one single or several vertical pipe sections 10.
[0031] The embodiment of the flow circuit shown in FIG. 4 is
particularly favourable for direct drawing of heated water for use
from the liquid reservoir 6 and for topping the reservoir up with
fresh water. However, this does not prevent the use of a separate
heat exchanger that is placed in communication with the liquid in
the liquid reservoir, and which transfers heat energy to water
outside the reservoir. The flow circuit shown in FIG. 5 is
particularly suitable in those cases where heated water is not to
be drawn directly from the liquid reservoir 6, but heat energy is
transferred onward by a heat exchanger 22 or the like that is
arranged in a suitable manner therein. In such cases, a liquid
other than water can be used in the system, e.g., anti-freeze
solution or oil.
[0032] Correct control of the flow of heated liquid in the flow
circuit is ensured by a non-return valve 17 that is located in each
individual upper pipe 7, 23 or pipe section 9 between the
respective solar panel 1, 2, 3, 4, 5 and the liquid reservoir 6, so
that the non-return valve 17 forms the highest point in the flow
circuit. The non-return valve 17 is also adapted to open and close
at a predetermined pressure in the liquid from the solar panel.
This means that the flow circuits will be opened and closed in
pulses, so that the hottest solar panel can be tapped for heat
energy first. Consequently, the non-return valve 17 in the
respective flow circuit will open and close alternately, as the
pressure rises and falls to the required level. Each individual
non-return valve 17 is equipped with a built-in expansion chamber
29 which has a suitable air valve 30 for releasing any air bubbles
which otherwise could bring the system to a halt. The non-return
valve 17 may optionally be equipped with a large separate expansion
chamber 32, see FIG. 5. According to need, the circulation circuit
can in addition be provided with a second non-return valve 31 of a
suitable type located in the lower pipes 8, 24, 11, see FIGS. 4 and
5.
[0033] The expansion chambers 29, 32 thus deal with any foam
formation from the liquid in the circuit. Before operation is
started, the circuit is filled to a level where the liquid is above
the upper circulation pipe, and then the system is pressurised with
air. Optional compression of this air prevents the circuit from
bursting. When the reservoir and the circuit are connected, double
pressure valves (not shown) may also be mounted so that the system
can be closed at a predetermined pressure level. After such
closing, the system must be reactivated and pressurised.
[0034] As shown in FIGS. 6 and 7, one embodiment of the non-return
valve 17 comprises in addition to the parts already mentioned
above, a valve seat 18 having a central fluid opening, a movable
float body 19 for opening and closing the fluid opening and a
spindle 20 for controlling the movement of the float body. As shown
in FIG. 7, the spindle 20 is fastened to the valve housing by, for
example, three bars. The float body 19 has an inverted conical
shape. This means that the non-return valve 17 is prevented from
opening when the heated liquid comes from the "wrong" direction. To
effect opening and closing of the non-return valve 17, the float
body 19 is designed to respond to a predetermined pressure
difference in the circuit. To be more precise, the float body must
be balanced in such manner that it is lifted up from and lowered
down towards the valve seat 18 in response to the pressure
difference that occurs when the temperature in the liquid is
changed in relation to a given value. This means that the float
body 19 must be dimensioned in relation to the change in the
liquid's density during the actual temperature change either
upwards or downwards. As shown schematically in FIG. 5, each
individual circuit may also be equipped with a lower one-way valve
of the same type as the upper one-way valve 17, with the exception
of the expansion chambers and the air valve. This means that less
stringent requirements can be made with respect to the precise
dimensioning of the float body 19, as two different pressure zones
are established in the system. Suitable materials for the valve
housing are brass, steel, acrylic, composite material etc., for the
float valve, silicone, acrylic, nylon, composite material etc. and
for the seat and the controlling spindle, brass, steel etc.
[0035] As shown in FIG. 8, a second embodiment of the non-return
valve comprises a two-part valve housing 38, 39 made preferably of
a transparent material so that any bubbling and the functioning of
the valve in general can be monitored visually. The housing parts
38, 39 are connected to each other in a suitable manner using a
seal 40 in the form of, e.g., an O-ring. The valve seat 37 is
formed in the upper housing part 39. The spindle 35 for the float
body is made of steel, polished or coated, and can be inserted into
bores in the housing parts when the valve is put together.
Furthermore, the float body has a central, relatively thin portion
33 and an outer portion 34 of greater thickness, and a
sleeve-shaped guide 36. The thickness of the outer portion 34 can
be varied, so that the weight of the float body can be balanced in
relation to the liquid, e.g., water, glycol solution, alcohol and
oil, that is used in the system. The underside of the float body
can be equipped with a pattern (not shown). Thus, the float body
rotates during its movement up and down along the spindle in order
to keep this clean. Unlike the valve mentioned above, the inlet and
outlet 27, 28 are oriented in a vertical direction. Nor is there an
expansion chamber in the valve itself, which means that such a
chamber must be mounted separately, e.g., in connection to the
outlet.
[0036] As shown schematically in FIGS. 9 and 10, the present solar
collection system can preferably be integrated into the facade of a
house or other building such as a holiday home etc. In the
illustrated embodiment, the system consists of just the two main
solar panels 1, 2 that are arranged in a house corner, and which
are flush with the outside of the house facade. However, it will be
appreciated that, for example, the solar collection system shown in
FIG. 1 could just as easily be used, with the two additional
upright solar panels 4, 5 positioned at a suitable point on one of
the facades of the house and flush with its outer side. In that
case, the two upright main solar panels 1, 2 and the horizontal
additional solar panel 3 will extend outwards in relation to the
house facade.
* * * * *