U.S. patent application number 11/929682 was filed with the patent office on 2009-04-30 for apparatus and method for solar thermal energy collection.
Invention is credited to Randy C. Gee, Roland Winston.
Application Number | 20090107488 11/929682 |
Document ID | / |
Family ID | 40581257 |
Filed Date | 2009-04-30 |
United States Patent
Application |
20090107488 |
Kind Code |
A1 |
Gee; Randy C. ; et
al. |
April 30, 2009 |
Apparatus and Method for Solar Thermal Energy Collection
Abstract
An apparatus for collecting solar energy includes a receptacle
adapted for receiving solar thermal energy, an insert adapted for
counter-flow located within the receptacle, and an absorption
device positioned proximate to and substantially conforming to at
least a portion of an internal surface of the receptacle and
thermally coupled to the insert.
Inventors: |
Gee; Randy C.; (Arvada,
CO) ; Winston; Roland; (Merced, CA) |
Correspondence
Address: |
FOLEY & LARDNER LLP
P.O. BOX 80278
SAN DIEGO
CA
92138-0278
US
|
Family ID: |
40581257 |
Appl. No.: |
11/929682 |
Filed: |
October 30, 2007 |
Current U.S.
Class: |
126/646 ;
126/684 |
Current CPC
Class: |
F24S 10/90 20180501;
Y02E 10/44 20130101; F24S 23/80 20180501; F24S 10/45 20180501 |
Class at
Publication: |
126/646 ;
126/684 |
International
Class: |
F24J 2/12 20060101
F24J002/12 |
Claims
1. An apparatus for collecting solar energy, comprising: a
receptacle adapted for receiving solar thermal energy; an insert
adapted for counter-flow located within the receptacle; and an
absorption device positioned proximate to and substantially
conforming to at least a portion of an internal surface of the
receptacle and thermally coupled to the insert.
2. The apparatus of claim 1, wherein the receptacle has a vacuum
drawn interior that is sealed with a glass to metal seal.
3. The apparatus of claim 1, further comprising a non-imaging optic
reflector located external to the receptacle and adapted to direct
solar thermal energy to the receptacle.
4. The apparatus of claim 3, wherein the reflector is a compound
parabolic concentrator (CPC).
5. The apparatus of claim 1, wherein a substantial portion of one
side of the insert is adjacent the absorption device.
6. The apparatus of claim 5, wherein the insert enters the
receptacle substantially at a cross-sectional center of the
receptacle and, further inside the receptacle, the insert shifts to
become closer to the absorption device and closer to a non-imaging
optical reflector.
7. The apparatus of claim 1, wherein the insert is a metal selected
from the group consisting of brass, copper and aluminum.
8. The apparatus of claim 1, wherein the absorption device is a
metal selected from the group consisting of brass, copper and
aluminum.
9. The apparatus of claim 1, further comprising: a manifold adapted
for circulating a fluid and coupled to the receptacle; and a pump
utilized for the circulating.
10. The apparatus of claim 9, wherein the manifold is coupled to
multiple receptacles.
11. The apparatus of claim 1, wherein the absorption device is
coated with a coating.
12. The apparatus of claim 11, wherein the coating is aluminum
nitride.
13. The apparatus of claim 1, wherein the absorption device has a
corrugated shape.
14. The apparatus of claim 1, wherein the insert is a counter-flow
tube.
15. The apparatus of claim 14, wherein the counter flow tube is
disposed inside the receptacle and is adapted to flow a thermal
transfer fluid therein.
16. The apparatus of claim 14, wherein the counter-flow tube
includes an inner tube and an outer tube and wherein the thermal
transfer fluid flows between the inner tube and the outer tube.
17. The apparatus of claim 1, further comprising a seal connecting
the receptacle to the insert.
18. The apparatus of claim 17, wherein the seal is a metallic disk,
and wherein the insert extends through a center of the metallic
disk.
19. A method for collecting solar thermal energy, comprising:
positioning a reflector exterior to a receptacle, the receptacle
containing an absorption device positioned proximate to and
substantially conforming to at least a portion of an internal
surface of the receptacle, wherein the reflector is adapted to
direct sunlight onto the absorption device; positioning an insert
inside the receptacle, the insert being coupled to the absorption
device, and the insert being adapted for counter-flow; and
circulating a fluid within the insert.
20. The method of claim 19, wherein a manifold is adapted to
circulate the fluid, the receptacle being coupled to the
manifold.
21. The method of claim 19, wherein the counter flow insert is an
element of the manifold.
22. The method of claim 20, wherein the manifold is coupled to
multiple receptacles.
23. The method of claim 19, wherein the absorption device is coated
with a coating of aluminum nitride.
24. The method of claim 19, wherein the reflector is a compound
parabolic concentrator (CPC).
25. The method of claim 19, wherein the insert and the absorption
device are formed of a metal selected from the group consisting of
brass, copper and aluminum.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to the field of
solar thermal energy. In particular, the present invention relates
to solar thermal energy collectors.
[0002] Solar thermal collectors have been utilized for over 20
years. The designs have varied from flat plate, box, air, integral,
unglazed more commonly to parabolic troughs and dishes and full
power towers. Though they have been commercially available for over
20 years, recent designs of evacuated tubes have become more
efficient and less costly, allowing them to be both commercially
and domestically available as well as more widely utilized. Some
devices contain heat removal inserts that are placed within the
tubes that serve the purpose of transferring the collected energy
to a heat-transfer fluid and are used to transfer heat to a
manifold located at the end of the tubes or in connection with the
inserts.
[0003] Conventional designs are limited in their ability to
transfer heat from the collector. It is desirable to improve the
efficiency with which such heat is transferred.
SUMMARY OF THE INVENTION
[0004] In one aspect, the invention includes an apparatus for
collecting solar energy. The apparatus comprises a receptacle
adapted for receiving solar thermal energy, an insert adapted for
counter-flow located within the receptacle, and an absorption
device positioned proximate to and substantially conforming to at
least a portion of an internal surface of the receptacle and
thermally coupled to the insert.
[0005] In one embodiment, the receptacle has a vacuum drawn
interior that is sealed with a glass to metal seal.
[0006] In one embodiment, the apparatus further comprises a
non-imaging optic reflector located external to the receptacle and
adapted to direct solar thermal energy to the receptacle. The
reflector may be a compound parabolic concentrator (CPC).
[0007] In one embodiment, a substantial portion of one side of the
insert is adjacent the absorption device. The insert may enter the
receptacle substantially at a cross-sectional center of the
receptacle and, further inside the receptacle, the insert is
shifted closer to the absorption device and closer to a non-imaging
optical reflector.
[0008] In one embodiment, the insert is a metal selected from the
group consisting of brass, copper and aluminum.
[0009] In one embodiment, the absorption device is a metal selected
from the group consisting of brass, copper and aluminum.
[0010] In one embodiment, the apparatus further comprises a
manifold adapted for circulating a fluid and coupled to the
receptacle and a pump utilized for the circulating. The manifold
may be coupled to multiple receptacles.
[0011] In one embodiment, the absorption device is coated with a
coating. The coating may be aluminum nitride.
[0012] In one embodiment, the absorption device may have a
corrugated shape.
[0013] In one embodiment, the insert is a counter-flow tube. The
counter-flow tube may be disposed inside the receptacles and may be
adapted to flow a thermal transfer fluid therein. The counter-flow
tube may include an inner tube and an outer tube, and the thermal
transfer fluid may flow between the inner tube and the outer
tube.
[0014] In one embodiment, the apparatus further comprises a seal
connecting the receptacle to the insert. The seal may be a metallic
disk, and the insert may extend through a center of the metallic
disk.
[0015] In another aspect of the invention, a method for collecting
solar thermal energy includes positioning a reflector exterior to a
receptacle, the receptacle containing an absorption device
positioned proximate to and substantially conforming to at least a
portion of an internal surface of the receptacle, wherein the
reflector is adapted to direct sunlight onto the absorption device;
positioning an insert inside the receptacle, the insert being
coupled to the absorption device, and the insert being adapted for
counter-flow; and circulating a fluid within the insert.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates a solar thermal energy collecting
apparatus according to an embodiment of the present invention;
[0017] FIGS. 2A and 2B illustrate cross-sectional views taken along
II-II of FIG. 1 of solar thermal energy collecting apparatus
according to embodiments of the present invention;
[0018] FIG. 3 illustrates a cross-sectional view of a receptacle
with another embodiment of an absorption device; and
[0019] FIG. 4 illustrates a detailed view of a section of the
counter-flow tube in the apparatus of FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Embodiments of the present invention provide method and
apparatus for collection and/or transferring of solar thermal
energy. In this regard, embodiments of the present invention may
provide inexpensive and efficient manners for collection of solar
thermal energy.
[0021] Referring to FIGS. 1, 2A and 2B, a solar thermal energy
collection apparatus 100 according to an embodiment of the present
invention is illustrated. In the illustrated embodiment, the
apparatus 100 includes one or more receptacles 120, each receptacle
120 having an insert 130 located therein. In the illustrated
embodiment, the receptacle 120 is a single-layer cylindrical glass
tubing that is closed at one end. The single-layer glass
configuration allows for operation of the apparatus at higher
temperatures and results in increased heat removal, as described
below. Of course, in other embodiments, various other types of
receptacles may be used. For example, in one embodiment, the
receptacle 120 may be a double-walled dewar with an inner wall and
an outer wall. The region between the inner wall and the outer wall
may be evacuated to reduce heat loss. The level of evacuation of
the region between the inner wall and the outer wall may be varied
to either increase efficiency (e.g., reduce heat loss) or improve
cost-effectiveness.
[0022] The other end of the receptacle 120 may be sealed with, for
example, a metallic disk 118 by way of a glass-to-metal seal. In
other embodiments, the metallic disk 118 may be replaced with
another type of closure that is sealed with the receptacle 120.
Preferably, the closure allows simple and efficient assembly of the
receptacle 120 to the apparatus 100 while ensuring integrity in the
sealing of the receptacle. In other embodiments the metallic device
may be replaced with a glass device used as a seal. In other
embodiments, the metallic disk may be replaced with a device having
a non-disk configuration. Any device may be used instead of metal
disk 118 as long as a reliable seal is a provided between the
receptacle 120 and a manifold 110.
[0023] In one embodiment, the inside of the receptacle 120 is
evacuated. The vacuum inside the receptacle 120 facilitates
reduction of thermal loss, thereby improving efficiency of the
apparatus, as described below. In this regard, the metallic disk
118 or other such closure provides sufficient sealing to maintain
the vacuum within the receptacle 120. The level of evacuation of
the receptacle 120 may be varied to either increase efficiency
(e.g., reduce heat loss) or improve cost-effectiveness.
[0024] The receptacle 120 is positioned such that an external
reflector 140 concentrates solar thermal energy (or solar
irradiance) onto the receptacle 120. The shape of the reflector 140
may be selected from a variety of shapes. In some embodiments, the
reflector 140 may operate in conjunction with a solar tracking
component. Preferably, the reflector 140 is adapted to operate in
the absence of such a tracking component. In one embodiment, the
external reflector 140 is a compound parabolic concentrator (CPC).
Such reflectors are well known to those skilled in the art.
[0025] FIGS. 2A and 2B illustrate two embodiments of an external
reflector 140a, 140b for use with embodiments of the present
invention. Referring first to FIG. 2A, the external reflector 140a
has two concave, parabolic components joined by a central convex,
v-shaped component. Each concave component forms substantially half
of a parabola.
[0026] Referring now to FIG. 2B, the external reflector 140b
includes two concave, parabolic segments joined to each other. In
this embodiment, each concave component forms substantially more
than half of a parabola. In this regard, the two concave segments
join to form an inverted "v" shape. Other reflector configurations
may also be used.
[0027] Thus, the shape of the reflector 140 directs all sunlight
incident on the reflector 140 within a predetermined angle of
incidence onto the receptacle 120. In this regard, sunlight is
concentrated efficiently onto the receptacle 120 while minimizing
heat loss. Further, the evacuated configuration of the receptacle
120 facilitates minimizing of the heat loss. Thus, sufficient
efficiency of the apparatus 100 can be achieved in the absence of a
solar tracking component, thereby resulting in significant cost
reduction.
[0028] Each receptacle 120 is provided with an insert 130 adapted
to fit within the receptacle 120. The insert 130 may be formed of a
variety of materials. In one embodiment, the insert 130 is formed
of a metal from the group of brass, copper and aluminum. The insert
130 enters the receptacle substantially at the cross-sectional
center of the receptacle through the sealed area (e.g., the metal
disk 118). In this example, a seal may be formed between the insert
130 and the metal disk 118 to maintain a vacuum within the
receptacle 120. Further inside the receptacle 120, the insert 130
includes a shifting portion 132 which shifts the insert to become
closer to a wall of the receptacle 120. In one embodiment, the
shifting portion 132 shifts insert 130 toward the cross-sectional
bottom of the tube, as shown in FIG. 2B, so that it is close to the
apex of the reflector. In another embodiment, the shift may be
further from the reflector and to one side as shown in FIG. 2A.
[0029] The insert 130 is coupled to a manifold 10, which is also
coupled to an insert corresponding to each of the other receptacles
of the apparatus 100. The number of receptacles 120 and
corresponding inserts 130 coupled to the manifold 110 may be
selected from any practical number dependant on the size of the
apparatus 100 desired.
[0030] In one embodiment, as illustrated in FIGS. 1, 2A and 2B, the
insert 130 may be coupled to the receptacle 120 in a variety of
manners including, but not limited to, welding. In one embodiment,
the coupling of the receptacle 120 and the insert 130 includes use
of screw-type threads formed on the manifold 110 and the tube 130,
similar to those found on conventional plumbing joints, that may
use a thread seal. In this embodiment, the vacuum area in the
receptacle 120 and the seal maintaining the vacuum are provided
with the receptacle 120 and insert 130 together. This provides ease
of on-site assembly and ease of maintenance and repair.
[0031] In one embodiment, the insert 130 is an integral part of the
manifold 110. In this regard, the insert 130 may be formed as an
integral part of the manifold 110 and does not include any joints,
connections or seals. The integral configuration of the insert 130
and the manifold 110 reduces the number of parts required, thereby
reducing the time and effort required for installation and assembly
of the apparatus 100 in the field. Thus, during assembly, the
receptacle 120 only needs to be positioned around the insert 130, a
vacuum area pulled and secured with, for example, the metallic disk
118. Further, the integral configuration eliminates a potential
leakage point for fluid flowing through the receptacle, as
described below.
[0032] The manifold 110 includes an inlet pipe 112 and an outlet
pipe 114 for circulating a fluid through the manifold 110 and the
insert 130. A pump 116 is provided to circulate the fluid 110. The
pump 116 may be located in the main portion of the manifold (as
shown) or away from the receptacles 120. The dimensions of the
inlet pipe 112, the outlet pipe 114 and the pump 116 may be
selected according to the requirements of the specific
implementation of the collector 100.
[0033] The inlet pipe 112 and the outlet pipe 114 are coupled to
the insert 130. The insert 130 is adapted for counter-flow of
fluid. One embodiment of such an insert is illustrated more clearly
in FIG. 4. In the illustrated embodiment, the insert 130 includes
an outer tube 134 and an inner tube 136. As illustrated in FIG. 4,
the bottom end of the inner tube 136 is spaced apart from the end
of the outer tube 134. The amount of space between the bottom end
of the inner tube 136 and the end of the outer tube 134 is
sufficient to allow fluid to flow freely around the open end of the
tube 130. As illustrated by the arrows in FIG. 4, fluid may flow in
through the inner tube 136 and may flow out through a region
between the outer tube 134 and the inner tube 136. In this regard,
the inner tube 136 and the outer tube 134 may be concentrically
positioned. Those skilled in the art will understand that the
direction of flow within the insert 130 may be reversed in other
embodiments, which are also contemplated within the scope of the
present invention.
[0034] An absorption device, such as absorption fin 150, is
positioned within the receptacle 120. The absorption fin 150 may be
formed of a variety of materials and may take a shape other than
that generally categorized as a fin. In one embodiment, the
absorption fin 150 is formed of a metal from the group of brass,
copper and aluminum. In one embodiment, the absorption fin 150 is
positioned proximate to the internal surface of the receptacle 120.
Further, the absorption fin 150 is configured to substantially
conform to the internal surface of the receptacle 120. Although the
embodiment illustrated in FIGS. 1, 2A and 2B includes an absorption
fin 150 which conforms to the entire circular cross section of the
receptacle 120, other embodiments may include fins which conform to
a portion of the receptacle 120.
[0035] In one embodiment, the outer surface of at least a portion
of the absorption fin 150 is covered with a selective coating. The
coating facilitates thermal absorption of solar thermal energy by
the absorption fin 150 to increase efficiency of the apparatus 100.
The coating may be aluminum nitride cermets or other types of
materials that facilitate thermal absorption.
[0036] In one embodiment, the absorption fin 150 is thermally
coupled to the insert 130 in order to facilitate transfer of
thermal energy to the manifold 110. In this embodiment, a
substantial portion of one side of the insert is adjacent the
absorption fin 150. The insert 130 may also be adjacent the
absorption fin 150 so as to be thermally coupled to it, but not be
physically coupled. In another embodiments the absorption fin 150
is integrally formed with the insert 130. In other embodiments the
absorption fin 150 is thermally coupled to the insert 130 by
mechanical means, such as welding, for example. The length of the
absorption fin 150 and the insert 130 within the receptacle 120 may
be as long as the receptacle 120 in which it is located or the
devices 130, 150 may be shorter than the receptacle 120.
[0037] As illustrated most clearly in FIG. 2, the absorption fin
150 may have a circular cross section to conform to the circular
cross section of the receptacle 120. In the embodiment illustrated
in FIG. 2, the absorption fin 150 is provided with a substantially
smooth, continuous surface. In other embodiments, as exemplarily
illustrated in FIG. 3, an absorption fin 152 may be provided with a
corrugated surface. The corrugations provide an increased surface
area for the absorption fin 152 while still conforming to the
internal surface of the receptacle 120.
[0038] In operation, a fluid is circulated through the manifold 110
via the pump 116. The flowrate of the fluid through the manifold
110 may be adjusted for particular conditions and particular
implementations. The fluid circulates through the inlet pipe 112
and into the counter-flow insert 130 within the receptacle 120. In
embodiments in which the insert 130 is integral with the manifold
110 (and the inlet pipe 112), no leakage issues are present. The
flow of the fluid through the insert, as exemplarily described
above with reference to FIG. 4, forms a circulation path within the
receptacle 120 (through the insert 130) and the manifold 110. The
fluid then exits the insert 130 and the receptacle 120 to the
outlet pipe 114. Thus, in this embodiment, substantially all of the
insert 130 contains circulating fluid. Again, the integral
configuration of the insert 130 and the manifold 110 prevents
leakage of the fluid as it exits the receptacle 120. Those skilled
in the art will understand that the circulation path (inlet pipe to
insert to outlet pipe) may be reversed in other embodiments, which
are also contemplated within the scope of the present
invention.
[0039] Thus, solar thermal energy is directed by the reflector 140
onto the receptacle 120. The solar thermal energy is absorbed by
the receptacle 120 and, more specifically, the absorption coating
on the outer surface of the absorption fin 150. The vacuum created
within the receptacle 120 reduces thermal heat loss by eliminating
the conduction and convection from the absorption fin 150 and the
insert 130.
[0040] While circulating through the insert 130, the fluid is
heated by the thermal energy transferred through the absorption fin
150, thereby facilitating transfer of solar thermal energy from the
apparatus 100. The fluid circulated through the apparatus 100 may
be selected from a variety of fluids. In one embodiment, the fluid
is mineral oil.
[0041] Embodiments of the present invention are capable of heating
the fluid to temperatures of above 280 degrees Fahrenheit without
the use of a solar tracker component. Certain embodiments are
capable of heating the fluid to temperatures of above 300 degrees
Fahrenheit as the fluid exits the receptacle 120. Thus, embodiments
of the present invention can provide efficient collection of solar
thermal energy in a cost-effective manner.
[0042] While particular embodiments of the present invention have
been disclosed, it is to be understood that various different
modifications and combinations are possible and are contemplated
within the true spirit and scope of the appended claims. There is
no intention, therefore, of limitations to the exact abstract and
disclosure herein presented.
* * * * *