U.S. patent application number 14/467179 was filed with the patent office on 2014-12-11 for direct flow solar collector.
The applicant listed for this patent is Yan Kunczynski. Invention is credited to Yan Kunczynski.
Application Number | 20140360492 14/467179 |
Document ID | / |
Family ID | 49083173 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360492 |
Kind Code |
A1 |
Kunczynski; Yan |
December 11, 2014 |
DIRECT FLOW SOLAR COLLECTOR
Abstract
A direct flow solar collector and solar hot water system are
presented wherein high pressure connections are eliminated to lower
installation costs while freeze and stagnation protection is
provided by a cooling loop and a continuous circulation protocol. A
novel fin design and a modular concept deliver manufacturing,
shipping and assembly efficiencies while providing flexibility for
customizing the collector configuration.
Inventors: |
Kunczynski; Yan; (Carson
City, NV) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kunczynski; Yan |
Carson City |
NV |
US |
|
|
Family ID: |
49083173 |
Appl. No.: |
14/467179 |
Filed: |
August 25, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US2013/065807 |
Oct 20, 2013 |
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14467179 |
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PCT/US2013/027339 |
Feb 22, 2013 |
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PCT/US2013/065807 |
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PCT/US2013/027339 |
Feb 22, 2013 |
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PCT/US2013/065807 |
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61716727 |
Oct 22, 2012 |
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61603541 |
Feb 27, 2012 |
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61660446 |
Jun 15, 2012 |
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61716727 |
Oct 22, 2012 |
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Current U.S.
Class: |
126/714 ;
126/641; 126/646; 126/663 |
Current CPC
Class: |
Y02P 90/50 20151101;
F24S 40/70 20180501; F24S 10/45 20180501; F24S 60/30 20180501; F24S
10/70 20180501; F24S 40/55 20180501; F24S 10/72 20180501; F24S
80/30 20180501; Y02E 10/44 20130101 |
Class at
Publication: |
126/714 ;
126/641; 126/646; 126/663 |
International
Class: |
F24J 2/24 20060101
F24J002/24; F24J 2/46 20060101 F24J002/46; F24J 2/34 20060101
F24J002/34 |
Claims
1. A solar collector, comprising: a manifold having an input port,
an output port and a plurality of orifices; a corresponding
plurality of solar tubes connected to the manifold through the
orifices, the plurality of solar tubes assembled in a planar array
and positioned for exposure to solar radiation; at least one liquid
channel from the input port to the output port, said liquid channel
having at least one continuous flow path there through; a means for
transferring heat absorbed from solar radiation in each solar tube
to a solar liquid flowing through the at least one continuous flow
path; a means for circulating the solar liquid through the means
for transferring heat; and is a means for cooling the solar liquid
to maintain its temperature at or below a preferred temperature;
whereby heat from solar radiation is transported for work purposes
through the solar liquid by the means for transferring heat and by
the means for circulating and the solar liquid is prevented from
overheating by the means for cooling.
2. The solar collector of claim 1, wherein the means for
transferring heat comprises a fin inserted into each solar tube and
extending the length of the tube, said fin having an integrated
U-shaped channel extending from an input end to an output end, the
input end of a first U-shaped channel in a first solar tube of the
planar array forming a fluid connection to the input port, the
output end of the first U-shaped channel of the first solar tube
forming a fluid connection in preferred configuration to the input
end of a last U-shaped channel in a last solar tube, the output end
of the last U-shaped channel in the last solar tube forming a fluid
connection to the output port, whereby at least one liquid channel
is formed for a continuous flow path through each solar tube, the
flow of solar liquid therein receiving heat by conduction from the
fin.
3. The solar collector of claim 2, wherein the preferred
configuration is a serial linkage joining a preferred number of
solar tubes and a parallel linkage joining a preferred number of
serial linkages.
4. The solar collector of claim 3, wherein the preferred number of
solar tubes in a serial linkage is ten and the preferred number of
serial linkages in a parallel linkage is four.
5. The solar collector of claim 2, wherein the integrated U-shaped
channel is formed as a part of an extrusion of the fin in a
construction eliminating air gaps in a heat conduction path while
simplifying assembly steps.
6. The solar collector of claim 5, wherein the fin extrusion is
comprised of aluminum or an alloy thereof.
7. The solar collector of claim 6, wherein the fin is formed into a
U-shape by bending a single extrusion length.
8. The solar collector of claim 7, wherein the fin is resiliently
biased to make contact with the wall of the solar tube and
essentially eliminate thereby any insulating air space there
between.
9. The solar collector of claim 1, wherein the means for cooling
comprises a cooling loop and a controller, the controller
programmed to redirect circulation of the solar liquid through the
cooling loop when the solar liquid is above a first preferred
temperature.
10. The solar collector of claim 9, wherein the first preferred
temperature is in the range of 55-60.degree. C.
11. The solar collector of claim 1, wherein the means for
circulating the solar liquid comprises a low-pressure pump in a
low-pressure loop.
12. The solar collector of claim 11, wherein the low-pressure loop
comprises flexible tubing for at least a part of the continuous
flow path.
13. The solar collector of claim 12, further comprising a means for
preventing freezing of the solar liquid.
14. The solar collector of claim 13, wherein the means for
preventing freezing comprises maintenance of low pressure
circulation below a second preferred temperature and an insulation
wrap of the flexible tubing combined with a resilient insulation
plug situated in the interstitial space of each solar tube.
15. The solar collector of claim 1, further comprising a means for
preventing freezing of the solar liquid.
16. The solar collector of claim 15, wherein the means for
preventing freezing comprises a low pressure circulation of the
solar liquid below a second preferred temperature.
17. The solar collector of claim 14, wherein the second preferred
temperature is in the range of 2-5.degree. C.
18. The solar collector of claim 16, wherein the second preferred
temperature is in the range of 2-5.degree. C.
19. The solar collector of claim 1, wherein the plurality of solar
tubes is arrayed bi-laterally from opposing sides of the
manifold.
20. The solar collector of claim 1, wherein the plurality of solar
tubes is arrayed unilaterally from one side of the manifold.
21. A solar hot water system, comprising: a solar collector having
a manifold with an input port, an output port and a plurality of
orifices; a corresponding plurality of solar tubes connected to the
manifold through the orifices, the plurality of solar tubes
assembled in a planar array and positioned for exposure to solar
radiation; at least one liquid channel from the input port to the
output port, said liquid channel having at least one continuous
flow path there through; and a means for transferring heat absorbed
from solar radiation in each solar tube to a solar liquid flowing
through the at least one continuous flow path; a storage vessel for
hot water in fluid communication with the input port and the output
port of the manifold; a means for circulating the solar liquid
through the means for transferring heat to the storage vessel; and
a means for cooling the solar liquid to maintain its temperature at
or below a preferred temperature; whereby heat from solar radiation
is used to heat the water in the storage vessel by the means for
transferring heat and by the means for circulating, and the solar
liquid is prevented from overheating by the means for cooling.
22. The solar hot water system of claim 21, wherein the solar
liquid is the water in the storage vessel and the means for
circulating comprises circulation through the storage vessel, the
water of the storage vessel having a stratification of heat therein
defining a hot section and a cold section, the input port of the
manifold in fluid connection to the cold section of the storage
vessel and the output port of the manifold in fluid connection to
the hot section.
23. The solar hot water system of claim 21, wherein the means for
transferring heat comprises a fin inserted into each solar tube and
extending the length of the tube, said fin having an integrated
U-shaped channel extending from an input end to an output end, the
input end of a first U-shaped channel in a first solar tube of the
planar array forming a fluid connection to the input port, the
output end of the first U-shaped channel of the first solar tube
forming a fluid connection in preferred configuration to the input
end of a last U-shaped channel in a last solar tube, the output end
of the last U-shaped channel in the last solar tube forming a fluid
connection to the output port, whereby at least one liquid channel
is formed for a continuous flow path through each solar tube, the
flow of solar liquid therein receiving heat by conduction from the
fin.
24. The solar hot water system of claim 23, wherein the preferred
configuration is a serial linkage joining a preferred number of
solar tubes and a parallel linkage joining a preferred number of
serial linkages.
25. The solar hot water system of claim 24, wherein the preferred
number of solar tubes in a serial linkage is ten and the preferred
number of serial linkages in a parallel linkage is four.
26. The solar hot water system of claim 23, wherein the integrated
U-shaped channel is formed as a part of an extrusion of the fin in
a construction eliminating air gaps in a heat conduction path while
simplifying assembly steps.
27. The solar hot water system of claim 22, wherein the means for
cooling comprises a cooling loop and a controller, the cooling loop
in fluid communication with the hot section, the controller
programmed to switch on circulation through the cooling loop when
the water of the storage vessel is above a first preferred
temperature.
28. The solar hot water system of claim 27, wherein the first
preferred temperature is in the range of 55-60.degree. C.
29. The solar hot water system of claim 21, wherein the means for
circulating the solar liquid comprises a low-pressure pump in a
low-pressure loop.
30. The solar hot water system of claim 29, further comprising a
means for preventing freezing of the solar liquid.
31. The solar hot water system of claim 30, wherein the means for
preventing freezing comprises a low pressure circulation of the
solar liquid below a second preferred temperature.
32. The solar hot water system of claim 31, wherein the second
preferred temperature is in the range of 2-5.degree. C.
33. The solar hot water system of claim 21, wherein heated water
for application purposes is provided by circulation through a heat
exchanger immersed in the storage vessel.
34. A method of configuring a solar collector to achieve operating
efficiency, comprising: providing a solar collector having a
manifold with an input port, an output port and a plurality of
orifices; a corresponding plurality of solar tubes connected to the
manifold through the orifices, the plurality of solar tubes
assembled in a planar array and positioned for exposure to solar
radiation; at least one liquid channel from the input port to the
output port, said liquid channel having at least one continuous
flow path there through; and a fin inserted into each solar tube
and extending the length of the tube, said fin having an integrated
U-shaped channel extending from an input end to an output end, the
input end of a first U-shaped channel in a first solar tube of the
planar array forming a fluid connection to the input port, the
output end of the first U-shaped channel in the first solar tube
forming a fluid connection in a preferred configuration to the
input end of a last U-shaped channel in a last solar tube, the
output end of the last U-shaped channel in the last solar tube
forming a fluid connection to the output port, whereby at least one
liquid channel is formed for a continuous flow path through each
solar tube, the flow of solar liquid therein receiving heat by
conduction from the fin; implementing the preferred configuration
by joining a preferred number of solar tubes in a serial linkage,
said serial linkage balancing heat transfer efficiency with
non-turbulent hydraulic flow; and implementing the preferred
configuration by joining a preferred number of serial linkages in a
parallel linkage, said parallel linkage balancing heat transfer
efficiency with hydraulic pressure; whereby the cost per BTU is
optimized by balancing pressure and flow characteristics.
35. The method of claim 34, wherein the preferred number of solar
tubes in a serial linkage is ten and the preferred number of serial
linkages in a parallel linkage is four.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuing application of co-pending International
Application PCT/US2013/065807, filed 20 Oct. 2013, and a
continuation-in-part application of co-pending International
Application PCT/US2013/027339, filed 22 Feb. 2013, with combined
priority claims to U.S. Provisional Application 61/603,541, filed
27 Feb. 2012, U.S. Provisional Application 61/660,446, filed 15
Jun. 2012 and U.S. Provisional Application 61/716,727, filed 22
Oct. 2012, the aforementioned PCT/US2013/065807 additionally with a
priority claim to the aforementioned PCT/US2013/027339, all the
foregoing of which are incorporated herein by reference in
entireties.
FIELD OF THE INVENTION
[0002] This invention relates to the harnessing of solar energy,
and more particularly to solar hot water heating.
BACKGROUND OF THE INVENTION
[0003] Concerns with the aging infrastructure of the electricity
grid in the United States, the environmental impact of carbon-based
fuels, the geo-political ramifications of crude oil supply, the
depletion of natural resources, the safety concerns related to
nuclear power, and the distribution and extraction challenges
surrounding natural gas have all brought increasing attention to
safe alternative energy sources such as Solar. Solar energy can be
captured as heat as well as converted to electricity. Next to space
heating, water heating is the most significant use of this
virtually inexhaustible and universally available resource.
[0004] Radiation from the sun is captured by a hot water solar
collector, which is generally a part of a system comprising a water
supply and/or storage means, a circulation pump, and a
heat-exchanger means. Flat-plate solar collectors are popular in
the sunny, year-around warm, climates in the United States. They
are comprised of a heat-absorption panel in contact with
circulating water and are typically housed under a transparent
covering and over an insulating bed. The flat panels absorb solar
energy in much the way photo-voltaic (PV) electric panels do. Heat
transfer efficiency is a function of reflective, conductive, and
convective heat losses, as well as the temperature differential
between the absorption panel and the incident water. While highly
efficient where optimally located, flat-plate collectors give poor
performance, nevertheless, in high temperature applications and in
cold conditions where high heat losses, due to the large surface
exposure of the panels, are experienced. Furthermore, maintenance
is cumbersome and often involves shutting the system down or
replacing the entire collector.
[0005] Evacuated tube (EVT) collectors are common in China, where
60% of global solar collector capacity is installed and where over
70% of the EVT's are manufactured. The most popular EVT type is a
double-walled glass tube having an evacuated air space between the
walls. The inside tube is coated to enhance absorption and
back-reflection of spectral infra-red (IR). Heat absorbed by the
tubes is transferred to a manifold, into which they are inserted,
by circulation of a liquid through an internal viaduct (U-tube) or
by phase change of a captive liquid in a capillary (heat pipe). The
tubular design accommodates different solar angles. The use of a
complete vacuum as an insulator makes them appropriate for cold
climates and where extremely high temperatures are required or
maintained. Maintenance is also simpler, in that individual tubes
can be replaced, often while the system is in use.
[0006] The major disadvantage of the EVT collector is the cost in
dollars per BTU. Considering the disadvantages of both the
flat-plate and EVT types of collectors, the northern climates of
the United States, where freezing temperatures are an issue for
much of the year, and low solar angles and short days are prevalent
for a portion of the year, are left under-served by solar hot
water. The same holds true for other colder locations throughout
the world where the economics of cheaper energy sources
prevail.
[0007] The object of the present invention is to enable solar hot
water heating in both cold and warm climates by making the
installation of a solar hot water system less expensive and the
operation thereof more efficient. These objects are achieved by
comprehensively addressing cost elements in the construction,
configuration and operation of the EVT collector.
SUMMARY OF THE INVENTION
[0008] The heat pipe EVT design requires a heat exchange in the
manifold, whereas the U-tube design avoids this exchange and the
energy losses attendant thereto by directly heating the solar
liquid. The disadvantages of the currently-practiced U-tube
technology, however, present opportunities for improvement. Both
freezing and overheating, also called "stagnation", become issues
with the solar liquid present in the EVT. Typically, to protect
from freezing, glycol antifreeze is used for the solar liquid in a
closed-loop circulation system. High pressure is required to
prevent the glycol from boiling during periods of stagnation. To
heat water in a storage tank, or a swimming pool, the glycol must
communicate through a heat exchanger, presenting another
opportunity for thermal loss.
[0009] The high pressure requirement drives high installation
costs. The U-tubes are typically arranged in an array and
integrated into a manifold configuration at a factory location.
Typically, 30-40 U-tubes are joined by brazing, soldering or
welding and then shipped to the installation site in an out-sized
shipping configuration. Shipping costs associated with such a
configuration can be expensive.
[0010] The substitution of water for glycol as the solar liquid
eliminates the high pressure requirement. Elimination of the high
pressure requirement means less expense in materials, shipping, and
assembly. In an alternative low pressure system, seals and flexible
tubing can be used to join components. Eliminating the factory
configuration means that modular design can be implemented and
customization facilitated. Assembly work can be done on-location
with unskilled labor. Pressure and relief tanks can be eliminated
as necessary system components, and the higher cost of
pressure-rated pumps can be avoided. System maintenance can be
achieved without bleeding and recharging lines and without
incurring the loss of a relatively expensive solar liquid, such as
glycol.
[0011] Freezing and stagnation remain as issues, however, with
water-based solar liquid. This is partially addressed in the
present art by gravity drain-back systems, which prevent freezing
by evacuating the solar liquid channels. Typically, however, some
liquid is always left fugitive in the channels, regardless of the
orientation or tilt of the collector array. These "gravity
blind-spots", or pathway low spots, can cause flash vaporization
during stagnation periods, thereby causing damage to the EVT's.
Even when drain-back systems are purged by air flushes, or other
means, the high temperatures of stagnation can cause damage to
system components. This damage can be particularly devastating to
plastic, rubber and aluminum parts used in low-pressure
systems.
[0012] The present invention presents the novel concept of "dumping
heat" by continuous circulation of the solar liquid during
non-heating periods and by the use of supplemental cooling during
over-heating periods. With a sufficiently large storage tank as a
heat repository, it has been shown that water in the tank can be
maintained in a range of 40-65.degree. C., even in a high solar
fraction climate, such as Mexico. Since the heat gained is
essentially free, the wasting of it is not an economic matter,
regardless of efficiency loss, particularly if the waste heat is
simply vented to the environment. In colder climates, the
maintenance of constant circulation between the solar collector and
an appropriately-sized storage tank can prevent freezing,
particularly where exposed plumbing is insulated.
[0013] An additional novel concept facilitates lowering pressure
and enhancing the thermal efficiency of the U-tube. The concept
addresses the fin, which is commonly attached to standard tubing
and projects arcuate "wings" there from which serve to absorb
radiant heat passing through the EVT walls. In the concept, the fin
and the water channel are combined in a single extrusion, which is
then bent into a "U" shape. The space between the upright arms of
the "U" is filled with resilient insulating material, which has the
effect of spreading the arms outwardly and urging them against the
EVT wall. The construction eliminates the insulating air gap that
results from separate components, and the curvature of the
extrusion, by closely following the wall contour, adds additional
thermal efficiency by permitting large area surface contact with
the wall.
[0014] Further, the cross-sectional area of the water channel is
enlarged by changing by changing from a circular to an ellipsoidal
shape. The enlargement, measuring almost twice that of the standard
tube, permits a larger volume of throughput resulting in lower
pressure. With system pressure reduced, not only by eliminating
glycol but also by making the channel enlargement, inexpensive and
easy-to-install flexible tubing may be used in the interconnecting
links of the U-tubes.
[0015] Still another novel concept derives from manipulation of
series and parallel connections channeling the water through the
U-tubes. U-tubes connected in series provide higher output
temperatures, but too many tubes connected in this manner produce
lower heat-transfer efficiency because successive heating causes
reduction of the temperature differential, the thermal driving
force. On the other hand, U-tubes connected in parallel have a
constant temperature differential but require a longer circulation
and pump operation time to achieve the same heating result. An
unexpected result of the parallel configuration, however, is that
the necessarily larger supply channels tend to cause a cavitation
effect in the relatively smaller tube channels; that is, air
pockets get trapped that produce an insulating layer and result
ultimately in lowered thermal efficiency. The inventive concept is
to use an optimal combination of both configurations to give an
improved result in terms of operating cost per BTU.
[0016] It is accordingly an object of the present invention to
lower the system pressure requirements by using a U-tube design in
an atmospheric system with water as the solar liquid. It is a
further object to eliminate drain-back systems by continuously
circulating the solar liquid and providing supplemental cooling. It
is a further object to prevent freezing of the solar liquid by
trickle circulation and the selective insulation of water channel
lines. It is a further object to lower assembly and material costs
by using flexible tubing connections. It is a further object to
improve thermal efficiency by integrating the water channel and the
fin in the same structure to eliminate any air gap in otherwise
separate structures. It is a further object to improve thermal
efficiency by making surface-to-surface contact between the fin and
EVT inner wall. It is a further object to enlarge the U-tube water
channel to lower the tube-to-tube pressure drop. It is a further
object to use a combination of series and parallel connections in
the water channels to optimize thermal efficiency. It is a further
object to make more efficient use of roof-top space by reducing
tube-to-tube spacing in the manifold. It is a further object to
manage roof-top space by configuring the EVT array with tubes on
either or both sides of the manifold as dictated by site layout. It
is a further object to manage roof-top space and improve appearance
by permitting low angle or horizontal installation profiles
essentially hidden from view. It is a further object to facilitate
snow removal from the collector. It is a further object to provide
a solar hot water system incorporating a hot water storage vessel.
It is a further object to provide a method of configuring a solar
collector to achieve operating efficiency.
[0017] These objects, and others to become hereinafter apparent,
are embodied in a solar collector comprising a manifold having an
input port, an output port and a plurality of orifices. The solar
collector further comprises a corresponding plurality of solar
tubes connected to the manifold through the orifices, the plurality
of solar tubes assembled in a planar array and positioned for
exposure to solar radiation. The solar collector further comprises
at least one liquid channel from the input port to the output port.
The liquid channel has at least one continuous flow path there
through. The solar collector further comprises a means for
transferring heat absorbed from solar radiation in each solar tube
to a solar liquid flowing through the at least one continuous flow
path. The solar collector further comprises a means for circulating
the solar liquid through the means for transferring heat. Finally,
the solar collector comprises a means for cooling the solar liquid
to maintain its temperature at or below a preferred temperature. So
configured, heat from solar radiation is transported for work
purposes through the solar liquid by the means for transferring
heat and by the means for circulating and the solar liquid is
prevented from overheating by the means for cooling.
[0018] In one embodiment, the means for transferring heat comprises
a fin inserted into each solar tube and extending the length of the
tube. The fin has an integrated U-shaped channel extending from an
input end to an output end. The input end of a first U-shaped
channel in a first solar tube of the planar array forms a fluid
connection to the input port while the output end of the first
U-shaped channel of the first solar tube forms a fluid connection
in preferred configuration to the input end of a last U-shaped
channel in a last solar tube. The output end of the last U-shaped
channel in the last solar tube then forms a fluid connection to the
output port. So configured, at least one liquid channel is formed
for a continuous flow path through each solar tube, the flow of
solar liquid therein receiving heat by conduction from the fin. In
a particular instance of the embodiment, the preferred
configuration is a serial linkage joining ten solar tubes and a
parallel linkage joining four serial linkages.
[0019] Also in the embodiment, the means for cooling comprises a
cooling loop and a controller. The controller is programmed to
redirect circulation of the solar liquid through the cooling loop
when the solar liquid is above a first preferred temperature. In a
particular instance of the embodiment, the first preferred
temperature is in the range of 55-60.degree. C.
[0020] In the preferred embodiment, a solar hot water system
comprises a solar collector having a manifold, a plurality of solar
tubes, at least one liquid channel, and a means for transferring
heat, as discussed above. The solar hot water system further
comprises a storage vessel for hot water in fluid communication
with the input port and the output port of the manifold. The solar
hot water system further comprises a means for circulating the
solar liquid through the means for transferring heat to the storage
vessel. Lastly, the solar hot water system comprises a means for
cooling the solar liquid to maintain its temperature at or below a
preferred temperature. So configured, the heat from solar radiation
if used to heat the water in the storage vessel by the means for
transferring heat and by the means for circulating and the solar
liquid is prevented from overheating by the means for cooling. In a
particular instance of the preferred embodiment, the solar hot
water system further comprises a means for preventing freezing of
the solar liquid.
[0021] As this is not intended to be an exhaustive recitation,
other embodiments are described in the detailed description below;
or may be learned from practicing the invention; or may otherwise
become apparent to those skilled in the art.
DESCRIPTION OF THE DRAWINGS
[0022] Various other objects, features and attendant advantages of
the present invention will become fully appreciated as the same
becomes better understood through the accompanying drawings and the
following detailed description, in which like reference characters
designate the same or similar parts throughout the several views,
and wherein:
[0023] FIG. 1 is a perspective view of a mounted solar collector of
the present invention shown in a bi-lateral configuration;
[0024] FIG. 2 is a truncated elevation view of an EVT;
[0025] FIG. 3 is a section view of the EVT taken along the lines
3-3 of FIG. 2;
[0026] FIG. 4 is a partial perspective view of two serially
connected U-tubes;
[0027] FIG. 5 is a detail view of detail 5 in FIG. 4;
[0028] FIG. 6 is a detail view of detail 6 in FIG. 4;
[0029] FIG. 7 is a partial perspective view of a 20-tube array
showing series and parallel path connections;
[0030] FIG. 8 is a partial plan view of a 20-tube array showing a
modular connection to tubes 21 and 22 in phantom line;
[0031] FIG. 9 is a side view of a 10-tube module with an eleventh
tube in phantom line;
[0032] FIG. 10 is a truncated section view taken along lines 10-10
of FIG. 9 showing solar liquid paths;
[0033] FIG. 11 is a partial exploded perspective view of three
serially-linked tubes;
[0034] FIG. 12 is a truncated perspective view of an extruded
fin;
[0035] FIG. 13 is a truncated elevation view of a U-tube
[0036] FIG. 14 is a section view taken along the lines 14-14 of
FIG. 13 showing a cross-section of the water channel;
[0037] FIG. 15 is a perspective view of the manifold;
[0038] FIG. 16 is an exploded perspective view of the manifold and
insulation;
[0039] FIG. 17 is a diagram of a solar collector system of the
present invention; and
[0040] FIG. 18 is a perspective view of the mounted solar collector
of FIG. 1 shown in a unilateral configuration.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0041] Flow paths referenced in the specification are illustrated
throughout the drawings by bolded arrows (other than those
indicating sectional cuts).
[0042] FIGS. 1 and 18 show the major components of a solar
collector 1. A solar tube planar array 12 is connected to a
manifold 20 through orifices 29. The manifold 20 has an input port
22 and an output port 23 defining there through and there between
at least one liquid channel 4 receiving circulation of a solar
liquid 3 (see FIG. 17) through at least one continuous flow path 9
(see also FIG. 10). When the planar array 12 is mounted to receive
solar radiation, such as on the roof top of a building, the solar
collector 1 may be supported by frame members 2 received in frame
slots 100 located in the middle and both ends of the solar
collector 1 (see also FIGS. 6 and 15).
[0043] As shown in FIGS. 7 and 8, the solar tube planar array 12 is
comprised of a plurality of solar tubes 7. The planar array 12 may
be arrayed from opposing sides of the manifold 20, or bi-laterally,
as shown in FIG. 1. Alternatively, the planar array 12 may be
configured only on one side, or unilaterally, as shown in FIG. 18.
The latter configuration facilitates snow removal, in addition to
accommodating site-particular space constraints. When arrayed
bi-laterally, the tubes are typically oriented east-west; when
arrayed unilaterally, the orientation is north-south. The array
should be inclined to present roughly perpendicular to the sun's
rays at the installation latitude. In most cases, the inclination
angle 106 is in the range 0-18.degree. plus the solar angle (FIG.
1). At a high solar angle, the profile elevation can be as little
as 25 cm. The frame members 2 may be directly anchored to a
supporting surface by any fastening means, or may be moveably held
in-place by a weighted base (not shown). An approximate weight for
a sufficiently-weighted base is 25 kg.
[0044] The number of solar tubes 7 in the planar array may be
limited by roof-top layout or, otherwise, by the design pressure
drop across the circulatory pathway. In the preferred embodiment,
it is desirable to maintain a low operating pressure for cost
advantage reasons. In a particular preferred embodiment, it is the
objective to maintain the operating pressure at 0.14-0.70
kgf/cm.sup.2 (2-10 psi) and a flow rate of 5.68 1 pm (1.5 gpm).
Accordingly, an optimal array would be comprised of not more than
40 tubes. Such an array has a footprint approximately 47% smaller
than a thermally-equivalent flat plate collector.
[0045] The solar tube 7 is designed to receive solar radiation
through a glass envelope and retain the energy as heat in the
interior. In the preferred embodiment, the solar tube 7 is a
double-walled EVT 8, as shown in FIGS. 2-6. There is a vacuum space
101 in EVT 8 between an inner tube 102 and an outer tube 103, the
vacuum serving as an insulator for entrapped heat. The inner tube
102 has several coating layers to enhance performance, namely an
anti-reflection layer, an absorbance-enhancing layer and an IR
reflection layer. The EVT 8 has an open end 104 and a closed end
109. When the solar tube 7 is connected to the manifold 20 through
one of the orifices 29, the open end 104 shoulders against a ledge
105 in the interior (FIG. 15). The closed end 109 is cradled in an
end cup 17, which is supported in the mounted configuration of
solar collector 1 by an end cup support 18. The end cup support 18
has an adjustment screw 107, which serves to bias the open end 104
against the ledge 105. The solar tubes 7 may be individually
removed and replaced in the array by disconnecting the end cup 17
from the end cup support 18.
[0046] The at least one liquid channel 4 is comprised of a means
for transferring heat 30, as shown in FIGS. 11-14. In the preferred
embodiment, said means comprises a fin 31. Fin 31 has an integrated
U-shaped channel 32, which forms a part of the at least one
continuous flow path 9. The integration of the U-shaped channel 32
into the fin 31 eliminates thermal losses resulting from air gaps
between otherwise separate structures. Fin 31 is inserted into the
EVT 8 to the extent of the draw therein. Fin 31 has arcuate wing
members 108 flanking the U-shaped channel 32 to form a contact
surface with the inner tube 102 through which heat is conducted to
the solar liquid 3 flowing through the U-shaped channel 32. The
arms of the "U" of the U-shaped channel 32 may be biased outwardly
by a resilient insulation plug 44 (see also FIG. 5) to make contact
with the wall of the tube and thereby eliminate another potential
air gap. Fin 31 is fabricated as an extrusion 36 and is comprised
of aluminum. Arcuate wing members 108 may be trimmed away (FIG. 12)
to form nipples 39 of U-shaped channel 32 at either end thereof.
Two such nipples 39 may be joined in a U-configuration by a
U-shaped connector 109 (not shown). The U-shaped connector 109 may
be, for example, a compression-molded piece of silicone. In the
preferred embodiment, the U-configuration is achieved by bending a
single extrusion with slotted wings into the U-shaped channel 32.
The U-shaped channel 32 maintains its throat by means of gussets 35
therein.
[0047] When fin 31 is inserted into EVT 8 (FIG. 11), two nipples 39
protrude from the open end 104 of the solar tube 7 to form an input
end 33 and an output end 34 of U-shaped channel 32, as shown in
FIG. 10. The output end 34 in one solar tube 7 may be connected to
the input end 33 in another solar tube to form a serial linkage 41.
The input end 33 in one solar tube may also be connected to the
input end in another solar tube to form a parallel linkage 42. The
input end 33 of a first U-shaped channel 37 in a first solar tube 5
of the planar array 12 is connected to the input port 22 of the
manifold 20 and the output end 34 of a last U-shaped channel 38 in
a last solar tube 6 is connected to the output port 23. The input
port 22 is connected to the output 23 in a preferred configuration
40 comprised of a preferred number of solar tubes 7 in the serial
linkage 41 and a preferred number of serial linkages 41 in a
parallel linkages 42 to form the at least one liquid channel 4
through which the solar liquid 3 may flow through each solar tube 7
in the at least one continuous flow path 9. Because the at least
one liquid channel 4 is contained within the fins 31, the solar
tubes 7 may be changed out for repair or replacement, in the manner
discussed above, without affecting the operation of the solar
collector.
[0048] One objective in the optimization of thermal efficiency is
to avoid non-turbulent flow in the at least one continuous flow
path 9. This is achieved by using serial linkage 41, wherein the
cross-sectional area of the at least one liquid channel 4 can more
closely approximate that of the cross-sectional area of the
U-shaped channel 32. Another objective in the optimization of
thermal efficiency is to maintain at least some temperature
differential across the path through serial linkage 41. This
requires limiting the number of solar tubes 7 in any one serial
linkage 41 and connecting multiple serial linkages 41 in the
parallel linkage 42. The span of the parallel linkage 42, in terms
of the number of tubes, is determined by the optimal pressure drop
across the at least one continuous flow path 9, which in turn
defines the operating pressure of the system. In the preferred
embodiment, the cross-sectional area of the U-shaped channel 32 is
approximately 72 mm.sup.2. This area compares favorably with the
approximately 36 mm.sup.2 opening of the standard tube of current
art. The preferred embodiment comprises ten solar tubes 7 to a
serial linkage 41 and four serial linkages 41 to a parallel linkage
42, optimally defining the planar array 12 as an array of 40 tubes
(the first 10 tubes only are shown in FIG. 10). It has been
discovered that optimal thermal efficiency, as measured by cost per
BTU, occurs by balancing the non-turbulent flow consideration,
having the consequence of avoiding insulating air pockets in the
channel, with the pressure consideration, having the consequence of
protecting temperature differential. The thermal performance of the
40-tube array herein described is roughly equivalent to two 1.22
m.times.3.05 m (4'.times.10') flat plate collectors. The pressure
consideration also affects other efficiencies of construction.
[0049] One of these other efficiencies afforded by low operating
pressure is the use of flexible tubing 10. Flexible tubing 10 is
inexpensive and simplifies installation. FIGS. 7 and 8 show a
network of the flexible tubing 10 in both serial and parallel
configurations. In the preferred embodiment, the flexible tubing 10
is comprised of high temperature (rated at 250.degree. C.) silicone
rubber. The flexible tubing 10 forms a seal with the nipples 39
when compressed thereon by a band, clip, or other form of
compression known in the art. As shown in solid line in FIG. 8, a
modular unit of planar array 12 is comprised of 20 solar tubes 7.
As shown in dashed line, two or more modular units may be combined
by extending parallel linkage 42 through linkage sections 13 of
flexible tubing 10. The modularity of the design facilitates
customized installation and delivers cost benefits associated with
on-site assembly.
[0050] The manifold 20 is comprised of manifold housing assembly 21
and insulation core 25, as shown in FIGS. 15 and 16. The manifold
housing assembly 21 is comprised of a housing base 26 and a housing
top 27. The housing top 27 is connected to the housing base 26 by a
manifold seal 24 at each side to form an enclosure. Each manifold
seal 24 comprises a plurality of orifices 29 to receive the solar
tubes 7 of the planar array 12. The insulation core 25 has a center
bore 28 in which the at least one liquid channel 4 is situated,
wherein the function of said insulation core is to insulate the
liquid channel 4 from heat loss. The housing base 26 and the
housing top 27 are fabricated from aluminum by extrusion means. The
manifold seal 24 is fabricated in a molding of ethylene propylene
diene monomer (EPDM) material. The insulation core 25 is fabricated
from sponge rubber material.
[0051] The solar collector 1 further comprises a means for
circulating 60 the solar liquid 3 through the means for
transferring heat 30. In the preferred embodiment, the means for
circulating 60 comprises a first low-pressure pump 61, a solar
liquid loop 74 and a holding tank 65, as shown in FIG. 17. The
holding tank 65 serves as a reservoir for the solar liquid 3, which
may be supplied to the reservoir from another source or may
circulate in a closed loop therein. The solar liquid loop 74
communicates with the holding tank 65 and includes the supply path
59 and the return path 58. The first low-pressure pump 61 is
controlled by controller 55.
[0052] The solar collector 1 further comprises a means for cooling
50 the solar liquid 3 to prevent over-heating. The means for
cooling 50 is initiated when the solar liquid 3 reaches a preferred
temperature 51. The means for cooling 50 may include refrigeration
of, or immersion of, the solar liquid loop 74 in an air stream or a
body of water, such as a pool or lake. The means for cooling 50 may
also include cycling the first low-pressure pump 61 during
nighttime or overcast days. In the preferred embodiment, the means
for cooling 50 comprises the controller 55 and a cooling loop 52,
as shown in FIG. 17. When the solar liquid 3 reaches a first
preferred temperature 53, the controller 55 initiates circulation
of the solar liquid in the holding tank 65 through the cooling loop
52 by activating a second low-pressure pump 62. In an instance of
the preferred embodiment, the first preferred temperature 53 is in
the range of 55-60.degree. C. The cooling loop 52 essentially vents
heat by convection to a relatively cooler environment, such as may
be found in an underground vault. In the preferred embodiment, the
cooling loop 52 is comprised of a serpentine configuration of
stainless steel tubes linked with silicone tubing. The controller
55 is in signal communication with one or more sensors 64
positioned at selected locations throughout the solar liquid loop
74. The sensors 64 may be transducers or thermocouples and may
measure temperature or pressure or both. In the preferred
embodiment, at least one of the sensors 64 is located in the
holding tank 65 and measures the temperature of the solar liquid
3.
[0053] The solar collector 1 further comprises a means for
preventing freezing 80 of the solar liquid 3 in the exposed portion
of the solar collector. The means for preventing freezing 80
comprises the continuous circulation of the solar liquid during low
temperatures. In the preferred embodiment, the controller 55
activates the first low-pressure pump 61 when the solar liquid 3
drops below a second preferred temperature 81. In an instance of
the preferred embodiment, the second preferred temperature 81 is in
the range of 2-5.degree. C. The means for preventing freezing 80
further comprises insulation of the exposed portions of the solar
liquid loop 74. In the preferred embodiment, an insulation wrap 82,
packed within a flexible polypropylene (PP) hose, surrounds the
flexible tubing 10 leading to and from the input and output ports
(FIG. 1). The insulation wrap 82 may be comprised of sponge rubber,
or any other known insulating material. The means for preventing
freezing 80 additionally includes the resilient insulation plugs 44
positioned inside the solar tubes 7.
[0054] In the preferred embodiment, the holding tank 65 is a hot
water storage vessel 71, as shown in FIG. 17. Hot water storage
vessel 71 is a member of a solar hot water system 70, which is also
includes solar collector 1. In an instance of the preferred
embodiment, hot water storage vessel 71 is a roto-cast tank
comprised of crossed-lined high-density polyethylene (HDPE). In
another instance, the solar liquid 3 of the solar hot water system
70 is water 73 stored in water storage vessel 71. Preferably, the
water 73 is of neutral pH and may contain stabilizing or
anti-corrosion additives. The means for circulating 60 further
comprises a circulation of water 73 from a hot zone 76 of the water
storage vessel 71 to a cold zone 77. The water storage vessel 71 is
preferably large enough in volume for a stratification to occur by
the colder, denser water gravitating downward. The water storage
vessel 71 is also preferably large enough to retain heat during
extended non-solar periods. In the preferred embodiment, the water
storage vessel 71 is jacketed with insulation. The insulation may
be comprised of polyurethane foam, or other known insulating
material. The solar liquid loop 74 fluidly connects the cold zone
77 to the input port 22 and the hot zone 76 to the output port 23.
The cooling loop 52 circulates in and out of the hot zone 62.
[0055] Hot water storage vessel 71 may further comprise submerged
heat exchanger 72. The heat exchanger 72 effectively removes heat
from the storage part of the system. In the case of swimming pool
heating, chlorinated pool water may be heated in the heat exchanger
72 without contaminating the solar liquid 3. For domestic hot water
use, the heat exchanger 72 outputs hot water on demand from a
pressurized cold water intake-line. In the preferred embodiment,
heat exchanger 72 is comprises of stainless steel tubing configured
into a spiral and is submerged in the solar liquid 3.
[0056] In an alternative embodiment, a method of configuring a
solar collector to achieve operating efficiency, as measured by
cost per BTU, comprises the steps as follows: [0057] a) providing
the solar collector 1, wherein the means for transferring heat 30
is a fin 31 inserted into each solar tube 7 and extending the
length thereof, said fin having an integrated U-shaped channel 32
extending from an input end 33 to an output end 34; the input end
33 of a first integrated U-shaped channel 37 in a first solar tube
5 of the planar array 12 forming a fluid connection to the input
port 22; the output end 23 of the first U-shaped channel 37 in the
first solar tube 5 forming a fluid connection in a preferred
configuration 40 to the input end 33 of a last U-shaped channel 38
in a last solar tube 6; and the output end 34 of the last U-shaped
channel 38 in the last solar tube 6 forming a fluid connection to
the output port 23; [0058] b) implementing the preferred
configuration 40 by joining a preferred number of solar tubes 7 in
a serial linkage 41, said serial linkage 41 balancing heat transfer
efficiency with non-turbulent hydraulic flow; [0059] c)
implementing the preferred configuration 40 by joining a preferred
number of serial linkages 41 in a parallel linkage 42, said
parallel linkage 42 balancing heat transfer efficiency with
hydraulic pressure.
[0060] It is to be understood that the invention is not limited in
its application to the details of construction, to the arrangements
of the components and to the method of using set forth in the
preceding description or illustrated in the drawings. For example,
the serial linkage count may be greater than ten to provide higher
temperatures; or the parallel linkage count may be greater than 4
to provide an increased solar fraction in colder climates. Also, it
is to be understood that the phraseology and terminology employed
herein are for the purpose of the description and should not be
regarded as limiting.
* * * * *