U.S. patent application number 12/293576 was filed with the patent office on 2010-09-09 for flat vacuum solar collector having chamber-type heads.
This patent application is currently assigned to Instituto Tecnologico y de Estudios Superiores de Monterrey. Invention is credited to Francisco Javier Cantu Ortiz, Alejandro Garza Cordoba, Noel Leon Rovira, Jose Angel Manrique Valadez.
Application Number | 20100224183 12/293576 |
Document ID | / |
Family ID | 38981907 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100224183 |
Kind Code |
A1 |
Leon Rovira; Noel ; et
al. |
September 9, 2010 |
Flat Vacuum Solar Collector Having Chamber-Type Heads
Abstract
The invention relates to a flat solar collector comprising
individual vacuum chambers. The invention is formed by two heads
and a series of parallel tubes having high transmittance in the
solar spectrum, which is disposed between said heads. The opposite
side of the heads is provided with vacuum chambers which closure
the connections of the conducting tubes. One of the vacuum chambers
is characterized in that it is fitted with a vacuum valve at one
end thereof. In addition, conducting tubes are disposed inside the
aforementioned tubes having high transmittance in the solar
spectrum and said conducting tubes are in turn connected to
collector plates, all under vacuum conditions which minimize
convection energy losses. When the conducting tubes are configured
in series, the collector can raise the temperature of the working
fluid to above 200.degree. C. All of the above is performed in a
novel, simple and economical manner.
Inventors: |
Leon Rovira; Noel;
(Monterrey, MX) ; Garza Cordoba; Alejandro;
(Guadalupe, MX) ; Manrique Valadez; Jose Angel;
(Nuevo Leon, MX) ; Cantu Ortiz; Francisco Javier;
(Monterrey, MX) |
Correspondence
Address: |
ROYLANCE, ABRAMS, BERDO & GOODMAN, L.L.P.
1300 19TH STREET, N.W., SUITE 600
WASHINGTON,
DC
20036
US
|
Assignee: |
Instituto Tecnologico y de Estudios
Superiores de Monterrey
Monterrey, N.L.
MX
|
Family ID: |
38981907 |
Appl. No.: |
12/293576 |
Filed: |
July 23, 2007 |
PCT Filed: |
July 23, 2007 |
PCT NO: |
PCT/MX07/00087 |
371 Date: |
September 19, 2008 |
Current U.S.
Class: |
126/653 ;
126/655 |
Current CPC
Class: |
F24S 10/753 20180501;
F24S 10/45 20180501; Y02E 10/44 20130101 |
Class at
Publication: |
126/653 ;
126/655 |
International
Class: |
F24J 2/24 20060101
F24J002/24 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2006 |
MX |
NL/A/2006/000045 |
Claims
1. A flat solar collector with vacuum chambers characterized by
comprising at least two high transmittance in solar spectrum tubes,
arranged in parallel, with the same diameter and length; limited on
each end side by a plate comprising in its whole length a number of
aligned circular punctures, with a lower diameter than the high
solar spectrum transmittance pipe diameter; the plate in one of its
sides, having circular slots which diameter matches with the high
transmittance tube diameter; and in the opposite side they have
larger slots surrounding in pairs the circular punctures; a support
of low thermal conduction is located inside each high transmittance
tube with a conducting tube of lower diameter than the plate
circular punctures being arranged longitudinally thereon; passing
through them and protruding by the plate rear side; the protruding
conducting tube end sides are located in the plate rear side and
connected each other by means of elbows; at least a vacuum chamber
over which means to generate and recover vacuum and means for
measuring a pressure level are possible to be arranged, is located
in the same plate rear side matching with the larger slot.
2. A flat solar collector with vacuum chambers according to claim
1, characterized in that heads are preferably rectangular, having 2
or more circular punctures aligned along the head; a "circular
slot" surrounding each circular puncture is located in the head
front side, the number of "circular slots" is equivalent to the
amount of high transmittance in solar spectrum tubes used for the
solar collector.
3. A flat solar collector with vacuum chambers according to claim
2, characterized in that the "circular slots" have the same
diameter than the high transmittance in solar spectrum tubes and
having a depth about the same than the high transmittance tube wall
width.
4. A flat solar collector with vacuum chambers according to claim
3, characterized in that the high transmittance in solar spectrum
tubes are optionally joined with grease, silicone and structural
glue.
5. A flat solar collector with vacuum chambers according to claim
1, characterized in that the rear side heads have slots in larger
amounts equivalent to the high transmittance in solar spectrum
tubes less 1; said slots are inserted and joined with grease,
silicone or preferably structural glue, the vacuum chambers
grouping in pairs the end sides protruding from the conducting
tubes and leaving without grouping the conducting tubes wherein the
working fluid is entering and leaving; said vacuum chambers are
arranged in a position where a set of 2 consecutive conducting
tubes may be covered.
6. A flat solar collector with vacuum chambers according to claim
4, characterized in that the number of high transmittance tubes is
odd in the rear side of both heads, one of the edge bores does not
include a slot, while when the number of high transmittance tubes
is even, the edge bores in one of the heads is always framed by a
slot while in the other head, the edge bores are not framed by a
slot. Slots shall be of a similar dimension to the vacuum chambers,
and with a depth approximately the same than the chamber wall
width.
7. A flat solar collector with vacuum chambers according to claim
4, characterized in that each conducting tube is covering a
collector plate length and the conducting tubes stand on low or
null thermal transmission supports, preferably ceramics, and said
supports in turn stand on the high transmittance in solar spectrum
tubes.
8. A flat solar collector device with vacuum chambers according to
claim 6, characterized in that the collector plates are located in
parallel to the head top portion and being covered by a selective
surface in both sides, in addition the attachment means between
collector plates and conducting tubes may be of a welded, pressed,
glued base or any other attachment means which efficiently
transmits energy therein.
9. A flat solar collector with vacuum chambers according to claim
1, characterized in that the high transmittance tubes have
preferably an outer diameter of 50 mm.
10. A flat solar collector with vacuum chambers according to claim
1, characterized in that the vacuum chambers are preferably built
with glass tubes and having a bottom larger than 5 mm, with a
circular, elliptic, or polygonal cross-section, preferably
elliptic.
11. A flat solar collector with vacuum chambers according to claim
1, characterized in that when the number of high transmittance
tubes is odd, the conducting tube inlet and outlet transporting the
working fluid are located one on each head, while when the number
of high transmittance tubes is even, the conducting tube inlet and
outlet transporting the working fluid are located in the same
head.
12. A flat solar collector with vacuum chambers according to claim
1, characterized in that the high transmittance in solar spectrum
tubes form a geometric structure providing a body to the solar
collector device.
13. A flat solar collector device with vacuum chambers according to
claim 1, characterized in that the conducting tubes y and the
collector plates are coated with a high monochromatic absorptivity
selective surface and a low monochromatic emittance in solar
spectrum or they are painted with high temperature resistant
reflection preventing black paint, which allows taking advantage of
the solar energy.
14. A flat solar collector with vacuum chambers according to claim
1, characterized in that the conducting tubes are attached among
them by means of elbows, and the elbows are coated with a high
monochromatic absorptivity selective surface or they are painted
with high temperature resistant reflection preventing black paint,
which allows taking advantage of the solar energy.
15. A flat solar collector with vacuum chambers according to claim
1, characterized in that within each high transmittance in solar
spectrum tube is located a conducting tube.
16. A flat solar collector with vacuum chambers according to claim
1, characterized in that the high transmittance in solar spectrum
tubes are preferably of borosilicate glass but they may be of any
material which efficiently transmits solar energy.
17. A flat solar collector with vacuum chambers according to claim
1, characterized in that there is sufficient space within the
vacuum chamber for conducting tube thermal expansion.
18. A flat solar collector with vacuum chambers according to claim
1, characterized in that the joint within the vacuum chamber
between the conducting tubes is carried out by means of 90.degree.
or 180.degree. elbows.
19. A flat solar collector with vacuum chambers according to claim
1, characterized in that vacuum is generated by means of a vacuum
generating pump and being able to recover and control as
required.
20. A flat solar collector with vacuum chambers according to claims
1, characterized in that the collector device may increase the
working fluid temperature up to more than 200.degree. C.
21. A flat solar collector system with vacuum chambers,
characterized in that at least two flat solar collectors with
vacuum chambers are serially or parallel connected according to
claims 1.
22. A flat solar collector system with vacuum chambers,
characterized in that connection of flat solar collectors with
vacuum chambers is performed by attaching the inlet and outlet
conducting tubes.
Description
FIELD OF INVENTION
[0001] This invention refers to a device which provides an
improvement in solar energy collection and conservation, in thermal
solar collectors. The device is formed by using conventional
components, which allows guaranteeing a better efficiency and a
reduction in manufacturing cost.
BACKGROUND
[0002] This invention is directly related with flat solar
collectors, which are used to absorb solar energy and transferring
it to a fluid. Moreover, it is linked with flat vacuum solar
collectors which provide vacuum between a collection plate and a
glass closure to obtain a better performance.
[0003] Since time ago it is known that flat vacuum solar collectors
are the most reliable of its kind, due to simplicity in their
structure and low operating temperatures. These low operating
temperatures do not damage the commercial materials being used in
their manufacturing. However, collectors which are able to transfer
a higher amount of energy to a fluid have been demanded in recent
times, and a number of promising technologies have been
achieved.
[0004] A reason why flat solar collectors do not reach high
temperatures is mainly due to the convection effect. In these
collectors, the main energy loss is due to the produced convection
since the collecting plate is at a different temperature than the
glass plate (collector closure). A number of different methods have
been proved with the passage of time to prevent this effect, such
as plate panels (hexagonal shape surfaces), by assembling a double
glass plate, and creating a vacuum between the collector plate and
the glass plate. This last method is the most commonly used, but
requires a more rough structure than the conventional flat
collector to support the vacuum caused stresses. In order to
provide the required structural support to withstand these efforts,
the collector structure has been modified, but a device is not yet
available to reach the desired temperature without requiring
costly, specialized materials and a troublesome manufacturing
process.
[0005] In order to get an outlet temperature in the collector
higher than 200.degree. C. using commercial parts and simple
manufacturing processes, the present device has been developed.
Said device comprises high transmittance in solar spectrum tubes
(TATES) closed in the end sides by a pair of heads attached to
small vacuum chambers. The only TATES which are not closed by the
vacuum chambers, are those with working fluid inlet and outlet.
Within these TATES conducting tubes (TUCS) made of any thermal
conducting material are located, attached to collector plates and
closed with a selective surface in the solar spectrum to absorb the
largest possible amount of energy. These TUCS are arranged over low
thermal conduction supports, preferably ceramics, in order to lose
the least possible amount of energy by conduction. By means of a
vacuum pump coupling, a vacuum is created within the high
transmittance in solar spectrum tubes and the vacuum chambers,
which allows reaching temperatures higher than 200.degree. C. The
present invention is different from previously designed devices due
to several factors, most relevant of them disclosed below. The
first difference is that flat vacuum solar collectors in the past
(U.S. Pat. No. 4,038,965-Lyon, U.S. Pat. No. 4,281,642-Steinberg,
U.S. Pat. No. 4,289,113-Whittemore, U.S. Pat. No. 5,653,222-Newman)
were designed in such a way that they all have a base, and a glass
plate which closes the collector at all. These have a severe
technical problem, since stresses created by a pressure difference
within the collector and the atmospheric pressure, distort the
structure and make it to fail, which causes a loss in vacuum within
the collector. Lyon and Whittemore use linear supports which are
attached along the collector so that they prevent distortion of the
collector containing box. Steinberg designed a complex support
which is located within the box. This support is a series of
semicircles, which provide support to the glass closure on one
side, while providing box support on the other side. Finally,
Newman proponed a less complex solution, which uses a glass closure
for the top of collector but the bottom thereof is comprised of
semicircles, the semicircle peaks serve as a support for the top
portion. In present invention the problem of pressure difference is
solved by using high transmittance in solar spectrum tubes, which
provide a smoothly spread stress distribution between said tubes.
Another important problem having the above mentioned collectors is
that glass thermal expansion and that from the base is different,
which causes vacuum losses. The expansion of one piece depends on
both the thermal expansion coefficient and the piece size. This is
not a problem under present invention, since the only expansion
which produces significant differences is the one occurring along
the high transmittance in solar spectrum tubes and the conducting
tubes, but because of the collector assembly form, said expansion
does not cause any vacuum losses since having enough space for
conducting tube differential expansion. Newman proposes in his
design that tempered glass is used on top closure and then a series
of treatment is provided to improve the glass optical properties,
while under present invention commercial tubes showing better
optical and thermal properties are used without any need to subject
them to any additional treatment.
BRIEF DESCRIPTION OF DRAWINGS
[0006] FIG. 1 is a general view of a flat vacuum solar
collector.
[0007] FIG. 2 is a top view of a collector.
[0008] FIG. 3 is a cross-sectional view A-A of FIG. 2.
[0009] FIG. 4a is rear view of one of the heads.
[0010] FIG. 4b is a top view of one of the heads.
[0011] FIG. 4c is a front view of one of the heads.
DETAILED DESCRIPTION OF INVENTION
[0012] The present invention represented in FIGS. 1 and 3 is a flat
solar collector comprising an arrangement of High Transmittance in
Solar Spectrum Tubes, herein and forth "TATES" (2), aligned in
parallel and closed in their end sides by a pair of heads (1) and
attached to small vacuum chambers (3).
[0013] Within each TATES and longitudinally arranged is a
conducting tube (TUCS) (9) with a lower diameter than TATE, which
transport the working fluid, TUCS are composed of any thermal
conducting material, and each TUCS has attached along its length, a
collecting plate (8) covered with a selective surface in solar
spectrum to absorb the most possible amount of solar energy. These
TUCS are arranged on low thermal conduction supports, preferably
ceramics (10) to minimize the energy losses by conduction.
[0014] Each TATES end is closed by a head (1); the heads are
preferably rectangular, having small punctures aligned along the
head, this punctures have a larger diameter than TUCS to allow
passing them therein. The number of circular punctures coincides
with the number of TUCS, and the head side which is attached to
TATES is named front side and the opposite one, rear side; being
through this side where these vacuum chambers are joined (3), being
of an area such that covers the cross-sectional area of 2 TATES.
Vacuum chambers cover and are grouping in pairs the head circular
punctures, where TUCS (9) are introduced. TUCS are located in
parallel and they are joined each other, within the vacuum chamber
by 90.degree. or 180.degree. elbows. The only circular punctures
which are not covered by vacuum chambers are the first circular
puncture or inlet puncture (6) and the last circular puncture or
outlet puncture (7) from conducting tubes (TUCS) (9) which carry
the working fluid. These are the only two contact points, no matter
what the amount of TUCS comprising the solar collector is, with the
feature that in this and last circular puncture the thermal
expansion coefficient is different from the remaining.
[0015] For vacuum control and generation, at least on vacuum
generation pump (4), and a pressure level meter (5) are connected
to one of the vacuum chambers (3), which allows to generate the
vacuum within the TATES and vacuum chambers, that is, in case that
the vacuum within the system is lost, it is possible to recover it
without requiring a system replacement and allowing additionally to
control vacuum levels to keep a determined temperature thus
preventing a modification in fluid temperature and flow. Because of
that, the vacuum level in turn allows that TUCS reach temperatures
higher than 200.degree. C.
[0016] It may be noted from FIGS. 1, 2, 4a, 4b and 4c that the
collector is a sealed device and composed by a variety of
conventional elements which when being integrated achieve a
non-conventional thermal performance. For improving the TATES
performance (2), these are preferably built from borosilicate glass
since due to its high compression mechanical strength they may
reach a high vacuum level, which was impossible in other flat
vacuum solar collectors.
[0017] Heads (1) are more detailed shown in FIGS. 4a, 4b and 4c. In
FIG. 4c it is noted that the head is preferably rectangular and a
number of bores are aligned in its front side equivalent to the
amount of TATES (2) forming the solar collector. Surrounding these
bores, circular slots (11) with the same diameter than TATES (2)
are located and having a depth about the same than the TATES wall
width (provided that this depth does not weaken excessively the
head wall (1). Upon assembling the TATES(2) in heads (1) these
circular slots (11) are filled with a material which prevents
vacuum leakages, where said material may be grease, silicone or
structural glue, the last being preferable. Assembly should be
carried out once glue is dried to guarantee a vacuum leakage free
joint between TATES and heads.
[0018] In FIG. 4a, the head rear side is seen where other slots are
noticed (12) for vacuum chambers (3), which gather the bores
whereby TUCS are passed, in such a way that when the TUCS number is
odd, one of the bores at edge does not carry a slot, while when the
number of TATES connected to heads is pair, the end side bores are
always surrounded by a slot (12). Slots (12) shall be of a similar
area to vacuum chambers (3), and with a depth about the same than
the chamber wall width provided it does not excessively weaken the
head wall (1). In the assembly process, these slots (12) are
preferably filled with a structural glue, and vacuum chambers are
inserted (3) inside the heads (1) before the glue is dried, in such
a way that a vacuum leakage free joint is achieved between the
vacuum chambers (3) and the heads (1).
[0019] One of the most important elements of this invention are the
high transmittance in solar spectrum tubes (TATES), which shall be
preferably of borosilicate glass, since these tubes show high
optical, thermal and mechanical properties beneficial for collector
performance. For example a common borosilicate glass tube will
transmit more than 92% of the energy received from the sun and
would reflect a negligible percentage (a common glass cannot reach
these properties unless subjected to several additional treatments
after manufacturing). Another important property is that its
thermal expansion coefficient is so low that allows a wide material
selection for head manufacturing (1). These TATES (2) shall be
preferably of an outer diameter higher than 50 mm to adjust
internally the conducting tubes (TUCS) with its respective
collecting plate, as well as the support means. TATES are an ideal
element since their circular cross-sectional surface show a smooth
stress distribution in vacuum and therefore a need to add
additional supports is nonexistent. Another element is the vacuum
chambers (3); which serve as head closures (1), these are
preferably built of glass tubes with a depth larger than 5 mm,
although the cross section of these chambers may be circular,
elliptic and polygonal, provided that fulfills the function of
covering with one of their cross-sectional ends two adjacent TUCS.
The use of glass is recommended since in this way takes advantage
of the joint and elbow collecting surface which connect among them
the TUCS. These vacuum chambers (3) may be of regular or
borosilicate glass. It is worth to mention that some of these
chambers carry a coupling to connect a vacuum pump (4) in the
opposite end to the one on contact with the head, which allows to
generate an initial vacuum or to recover the vacuum in case that
due to any event a loss may exist. It is advisable that in another
one of the vacuum chambers (3), preferably in the opposite side of
a vacuum chamber (3) with vacuum pump (4), a pressure indicator (5)
is installed, with which the existing vacuum level may be measured
and the type of leakage if any. Another important feature which may
be noticed in FIG. 1 is the working fluid inlet which for operation
in these collectors is generally water. This inlet as not being in
a vacuum chamber includes a package which contains the vacuum
within the collector.
[0020] In FIG. 2 the same previously disclosed features may be
observed. The amount of TATES (2) shall be determined by the
working fluid flow and temperature to be observed, but sometimes at
least two serial or parallel vacuum chamber solar collectors will
be required to achieve these goals, thus obtaining a flat solar
collector system. Having this in mind, it should be considered that
for an odd TATES number (2), the TUCS inlet (6) and outlet (7)
carrying the working fluid are each in each head (1), while when
the TATES (2) number is even, TUCS inlet (6) and outlet (7)
carrying the working fluid are located in the same head (1).
[0021] In FIG. 3, a detail is shown of a cross-sectional view in
point A-A represented by FIG. 2; the different elements comprising
each TATES inner part in the solar collector may be observed.
Beginning with the upper part, a collector plate (8) is firstly
located, which is whether welded or attached to the conducting tube
(TUCS) (9) carrying the working fluid and the TUCS (9) stand on low
thermal transmission supports, preferably ceramics (10). Within the
vacuum chambers (3) the joints among the TUCS (9) are located,
depending on the arrangement to be used (serial or parallel).
[0022] Collector plates (8) are made of a thermal conducting
material (preferably copper). These collector plates (8) shall be
of a thickness not larger than 0.2 mm and their length shall be
shorter than each TATES (2) on each end depending on the circular
slot (11) depth. Their width shall be also a minimum of 95% from
TATES (2) diameter, and the maximum dimension of these plates shall
be only determined by the collector plate material thermal
expansion (8), since in any time these will not touch the TATES (2)
because that would cause heat losses by contact. Another important
feature of collector plates (8) is that these are coated by a solar
spectrum selective surface on both sides. Together with these
collector plates (8) the TUCS (9) are located which carry the
working fluid. The joint between these components is carried out by
using any additive which allows a maximum possible heat
transmission, such as silver welding. The TUCS (9) are also coated
with a selective surface, preferably black chromium. This selective
surface shall have a high solar spectrum monochromatic absorptivity
and a low solar spectrum monochromatic emittance to be a candidate
for use in a collector. All the thermal conducting material angles
of this selective surface are coated since in special cases
concentrators may be arranged together to the collector and
directing their light beam to the concentrator bottom, since being
the TATES (2) bottom would pass the same energy passing in the top
portion (more than 92%). TUCS and collector plate assembly stands
on support means (10) made of a thermal insulating material (e.g.
ceramics) so that the largest possible amount of energy is
transferred to the working fluid. These supports (10) may be
substituted by designs having a lower contact surface with the TUCS
(9) or with the TATES (2). In the vacuum chamber ends (3) is where
the TUCS attachment is made. Materials within the vacuum chambers
(3) generally form 180.degree. elbows which are also coated with a
solar spectrum selective surface, in order to take advantage as
much as possible from solar energy.
[0023] A flat vacuum solar collector with chamber type heads is
possible to operate by fulfilling with all previous disclosure,
which may raise the working fluid temperature higher than
200.degree. C. since vacuum prevents that convection is present,
then conduction losses are only present. These losses are very
small since the contact is with insulating materials. In addition,
a 100% of the piping for solar energy absorption may be used since
everything is enclosed within containers with high solar spectrum
transmittance.
* * * * *