U.S. patent application number 11/313035 was filed with the patent office on 2006-06-22 for solar thermal collector.
This patent application is currently assigned to Bayer MaterialScience AG. Invention is credited to Frank Krause, Gerhard Opelka, Constantin Schwecke.
Application Number | 20060130827 11/313035 |
Document ID | / |
Family ID | 35934204 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060130827 |
Kind Code |
A1 |
Opelka; Gerhard ; et
al. |
June 22, 2006 |
Solar thermal collector
Abstract
A solar thermal collector comprising multiplicity of chords and
webs is disclosed. The first, second and third horizontal chord of
the solar thermal collector are connected to one another by webs
positioned vertically to said horizontal chords. The first
horizontal chord is transparent and the second horizontal chord,
which is positioned between the first and third horizontal chords,
absorbs thermal radiation and is perforated. The horizontal chords
and said webs of the inventive solar thermal collector comprise
thermoplastic materials. Producing the solar thermal collector
including perforating the second horizontal chord by means of a
laser beam is also disclosed.
Inventors: |
Opelka; Gerhard;
(Leverkusen, DE) ; Krause; Frank; (Bergisch
Gladbach, DE) ; Schwecke; Constantin; (Alfter,
DE) |
Correspondence
Address: |
BAYER MATERIAL SCIENCE LLC
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Assignee: |
Bayer MaterialScience AG
|
Family ID: |
35934204 |
Appl. No.: |
11/313035 |
Filed: |
December 20, 2005 |
Current U.S.
Class: |
126/651 |
Current CPC
Class: |
F24S 10/80 20180501;
F24S 10/501 20180501; Y02E 10/44 20130101; F24S 10/73 20180501 |
Class at
Publication: |
126/651 |
International
Class: |
F24J 2/24 20060101
F24J002/24 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2004 |
DE |
102004061712.0 |
Claims
1. A solar thermal collector comprising a first, second and third
horizontal chords that are connected to one another by webs
vertical to said horizontal chords in which the first horizontal
chord is transparent and the second horizontal chord, which is
positioned between the first and third horizontal chords, absorbs
radiation and is perforated with a multiplicity of holes, said
horizontal chords and said webs comprising thermoplastic
materials.
2. The solar thermal collector according to claim 1, characterised
in that the proportion of the perforated surface in the whole
surface of the second horizontal web is at most 3%
3. The solar thermal collector of claim 2 wherein the proportion is
at most 1%.
4. The solar thermal collector of claim 2 wherein the proportion is
0.1 to 0.4%.
5. The solar thermal collector according to claim 1 wherein the
horizontal chords have a thickness of 0.2 to 2 mm.
6. Solar thermal collector according to claim 1 or 2 wherein chords
and webs are forming at least two superimposed rows of adjacent
chambers, which are separated from each other and may be flowed
through by a heat exchange gas in particular by air.
7. Solar thermal collector according to claim 6 wherein the
superimposed chambers are connected by a multiplicity of holes.
8. Solar thermal collector according to claim 6 or 7 wherein the
chambers are closed at their ends and the chambers located above
the second (absorbing) horizontal chord have at least one inlet for
a heat exchange gas and the chambers located below the second
horizontal chord have at least one outlet for heated solar thermal
collector gas.
9. Solar thermal collector according to claim 6 or 7 wherein the
chambers are connected to a blower which optionally is part of a
pumping circuit.
10. Solar thermal collector according to claim 6 or 7 wherein the
cross section of the chambers preferably has a cross section area
of 0,25 to 3600 mm.sup.2.
11. The solar thermal collector according to claim 1 wherein the
vertical webs have a height of 3 to 50 mm.
12. The solar thermal collector according to claim 1 wherein the
thermoplastics material is at least one member selected from the
group consisting of polycarbonate, polymethyl methacrylate,
polystyrene, polyethylene, polyethylene terephthalate,
thermoplastic polyurethane and polyvinyl chloride.
13. The solar thermal collector according to claim 1 wherein the
second horizontal chord and/or the third horizontal chord comprise
at least one member selected from the group consisting of
polybutylene terephthalate, polystyrene, thermoplastic polyurethane
and acrylonitrile/butadiene/styrene/copolymer.
14. The solar thermal collector according to claim 1 wherein the
second horizontal chord contains carbon black.
15. A method for the production of the solar thermal collector of
claim 1 comprising in a first step forming a multiple web panel by
coextrusion of a transparent and a radiation absorbing
thermoplastic material with a plurality of horizontally oriented
chords, which are connected by a plurality of vertical webs and
wherein the second horizontal chord comprises the radiation
absorbing thermoplastic material and in a second step directing a
laser beam through the first horizontal chord onto the second
horizontal web in a manner calculated to perforate said second
horizontal chord and providing the chord with a multiplicity of
holes.
16. The method according to claim 10 wherein the laser beam has a
wavelength in the range of 800 to 1200 nm.
Description
FIELD OF THE INVENTION
[0001] The thermoplastically formed article of manufacture and in
particular to a solar thermal collector.
BACKGROUND OF THE INVENTION
[0002] Air collectors, also called air heaters or solar thermal
collectors, are radiation solar thermal collectors by means of
which non-concentrated solar radiation energy is absorbed and
transmitted in part to the heat carrier medium comprising air or
another gas. This type of radiation or solar collectors is used for
example in the low temperature range.
[0003] At the present time solar thermal collectors for solar
radiation are mainly manufactured with absorbers of aluminium or
other metals. The reason for this is the good thermal conductivity
of metals, since on account of the low heat transmission from air
to a flat surface the solar heat in solar thermal collectors has to
be distributed over a large surface (e.g. over fins on the rear
side of the absorber).
[0004] A fundamentally different concept is adopted in surface
layer extraction-type solar thermal collectors and perforated
absorbers. The structure of such a collector is described for
example in DE 19 820 156 A, DE 2 943 159 A and EP 553 893 A.
[0005] Absorbers with perforations and surface layer extraction
type collectors have two types of advantages compared to absorbers
involving flow over the rear surface: on the one hand the
perforations produce a significant improvement in the heat
transmission from the absorber to the air; secondly, due to the
suction effect convection in the collector is prevented, as a
result of which the thermal losses from the absorber to the glazing
fall dramatically and a well-cooled absorber (i.e. with a high heat
transmission coefficient from the absorber to the air) is no longer
absolutely necessary in order to achieve a high efficiency. In
surface layer extraction-type absorbers the thermal conduction in
the collector accordingly plays a minor role in regards to the
efficiency of the collector. Extremely thin absorbers or absorbers
with low thermal conductivity may therefore be used.
[0006] A disadvantage of the solar thermal collectors known from
the prior art is the relatively large weight of the absorber, frame
and covering, since they are manufactured from metal.
[0007] The object of the present invention is accordingly to
provide a solar thermal collector of thermoplastics material that
may be manufactured relatively easily, i.e. with a low technical
expenditure, as well as a process for its production.
SUMMARY OF THE INVENTION
[0008] A solar thermal collector comprising multiplicity of webs
and chords is disclosed. The first, second and third horizontal
chords of the solar thermal collector are connected to one another
by webs positioned vertically to said horizontal chords. The first
horizontal chord is transparent and the second horizontal chord,
which is positioned between the first and third horizontal chords,
absorbs thermal radiation and is perforated. The horizontal chords
and said webs of the solar thermal collector comprise thermoplastic
materials. Producing the solar thermal collector including
perforating the second horizontal chord by means of a laser beam is
also disclosed.
DESCRIPTION OF THE DRAWING
[0009] FIG. 1 is a schematic representation of the inventive solar
thermal collector.
[0010] FIG. 2 is a schematic representation of the solar thermal
collector with a pumping circuit.
DETAILED DESCRIPTION OF THE INVENTION
[0011] The invention provides a solar thermal collector comprising
a panel that contains a plurality of horizontally oriented chords
of thermoplastics material optionally parallel to and separate from
one another. The webs are connected to one another by a plurality
of vertical webs. The panel includes at least one transparent
outermost horizontal chord (referred to below as first horizontal
chord), and an underlying perforated horizontal web with a
multiplicity of holes (referred to below as second horizontal
chord) that absorbs radiation.
[0012] In a preferred embodiment chords and webs are forming at
least two superimposed rows of adjacent chambers, which are
separated from each other and may be flowed through by a heat
exchange gas in particular by air.
[0013] In another preferred embodiment the superimposed chambers
are connected by a multiplicity of holes.
[0014] In a particular preferred embodiment the chambers are closed
at their ends and the chambers located above the second (absorbing)
horizontal chord have at least one inlet for a heat exchange gas
and the chambers located below the second horizontal chord have at
least one outlet for heated solar thermal collector gas.
[0015] In another preferred embodiment of the solar thermal
collector the chambers are connected to a blower which optionally
is part of a pumping circuit. Particularly preferred a solar
thermal collector is located clown stream to the outlet of the
chambers.
[0016] The cross section of the chambers preferably has a cross
section area of 0,25 to 3600 mm.sup.2.
[0017] The invention also provides a process for the production of
the solar thermal collector according, to the invention, in which
in a first step a multiple web panel is formed by coextrusion of a
transparent and a radiation absorbing thermoplastic material with a
plurality of horizontally oriented chords, which are connected by a
plurality of vertical webs and wherein the second horizontal chord
comprises the radiation absorbing thermoplastic material and in a
second step a laser beam is directed through the first horizontal
web onto the second horizontal web and the second horizontal web is
perforated and provided with a multiplicity of holes by means of
the laser beam.
[0018] Panels containing a plurality of webs and chords are known.
The multiple web panel used according to a preferred embodiment
comprises at least three horizontal webs arranged preferably
parallel to one another. The horizontal chords are connected to one
another by vertical webs arranged preferably perpendicular thereto.
The vertical webs are arranged preferably parallel to one another.
In this way at least two superimposed layers of
parallelepiped-shaped chambers lying adjacent to one another are
formed, through which air or another gas flows during operation of
the solar thermal collector. The horizontal chords and vertical
webs may be of the same or different thicknesses and have a
thickness of preferably 0.2 to 2 mm. The second horizontal chord in
the perforation area (for example laser perforations) is designed
having wall thicknesses of preferably 0.2 to 0.5 mm. The vertical
webs are 3 to 50 mm high. The height of the vertical webs
determines the height of the chambers, which may be formed having
the same height or different heights. Preferably the vertical webs
are shorter towards the middle of the multiple web panel than in
the edge regions of the web panel in order to minimise the shadow
area of laterally incident solar radiation.
[0019] In a further preferred embodiment of the solar thermal
collector the diameter of the holes in the radiation absorbing
chord is 0.1 to 0.5 mm, particular preferred 0.2 to 0.5 mm.
[0020] The first horizontal web is transparent for the radiation to
be absorbed. The degree of transmission in the wavelength range
from 400 to 1300 nm is preferably at least 60%. During operation of
the solar thermal collector the transparent horizontal web is
aligned facing the sun. The sunlight passes through the first
horizontal web onto the second horizontal web, which forms the
absorber surface.
[0021] The second horizontal web, which is positioned between the
first and third horizontal chords, absorbs radiation, i.e. it has
in particular an absorption capacity of at least 80% in the
wavelength range from 400 to 2500 nm. The second horizontal chord
with its comparatively high absorption capacity must be able-to
absorb as much sunlight as possible during operation of the solar
thermal collector. For this purpose the second horizontal web is
for example colored and/or coated with a black compound. A black
coloration of the second horizontal web may be achieved for example
by imprinting with a black colorant, coating with black chromium or
black aluminium, or by direct coloration of the plastics
composition with suitable colorants, preferably carbon black. The
second horizontal web is hereinafter also termed absorber
surface.
[0022] The partial transparency of the second horizontal chord of
up to 20% in the visible wavelength range may be achieved by a
compound with or without a high reflection capacity in the infrared
wavelength range, or may be accomplished in combination with such a
compound, for example in the form of an additional layer. The solar
thermal collector is also suitable for use as a partially
transparent glazing element, for example in a building
enclosure.
[0023] In a preferred embodiment the second horizontal chord
comprises a selective absorber layer on the side facing the sun
during operation. In this connection the second horizontal web is
coated with one or more compounds that have a reflection capacity
of at least 70% in the infrared wavelength range. If the second
horizontal chord is colored black and/or has in addition a coating
of a black compound, the compound with a high reflection capacity
in the infrared wavelength range may be largely permeable to
visible light. Examples are indium/tin oxide (ITO), zinc oxide
(ZnO) and tin oxide (SnO). The infrared wavelength range is
understood to denote the wavelength range above 800 nm.
[0024] The second horizontal chord is perforated. The perforated
surface amounts to at most 3%, preferably at most 1% and
particularly preferably 0.1 to 0.4% relative to the total surface
area of the second horizontal chord.
[0025] The third horizontal chord may be transparent or absorbent,
for example colored and/or coated. This chord faces away from the
sun during operation of the solar thermal collector.
[0026] In addition further layers of adjacently-lying chambers may
be included in the structure of the inventive solar thermal
collector. For this purpose further horizontal chords are provided
that are in turn joined by vertical webs. For example, a fourth
horizontal chord may be arranged underneath the third horizontal
chord. In this way a third layer of adjacently-lying chambers is
formed. This third layer is aligned facing away from the sun during
operation of the solar thermal collector. The chambers of this
third layer serve as insulating chambers.
[0027] In a preferred embodiment the multiple web panel is open on
two sides lying opposite one another, i.e. the two surfaces
perpendicular to the horizontal chords and vertical webs are not
bordered. This enables gas flow through the chambers of the
panel.
[0028] The two remaining sides lying opposite one another are
terminated by vertical webs and are thus not open. The panel may be
provided with a tongue-and-groove system on the two non-open sides,
as described for example in DE10 304 536 A and in WO 2004/070287
incorporated herein by reference.
[0029] The chambers of the first layer between the first and second
horizontal chords are aligned facing the sun. They are hereinafter
also termed absorption chambers. The chambers of the second layer
between the second and the third horizontal chord are aligned
facing away from the sun. They are hereinafter also termed
collecting chambers. During operation of the solar thermal
collector the chambers of both layers are filled with gas or gas
flows through them. Preferably the gas is air. In addition other
gases or mixtures of various gases may also be used, for example
those having a higher thermal capacity than air, such as for
example argon. Cold gas (temperature in the range from -10.degree.
to -30.degree. C.) is introduced into the absorption chambers
exposed to sunlight. From there the gas flows through the
perforations of the second horizontal web into the collecting
chambers resting against the rear side of the chord. The gas heats
up on passing through the perforations. The heated gas flows out of
the collecting chambers.
[0030] The multiple web panel of the solar thermal collector
according to the invention is made of thermoplastics material.
Examples of suitable transparent thermoplastics materials, such as
are used in particular for the first horizontal web, are
polycarbonates, polymethyl methacrylate, polystyrene, polyethylene,
polyethylene terephthalate, thermoplastic polyurethane and
polyvinyl chloride. Alternatively, materials other than transparent
plastics materials produced by multilayer extrusion processes may
be used for the second horizontal web (absorber surface) and/or for
the third horizontal web (i.e. the surface facing away from the
sun), such as for example polybutylene terephthalate, polystyrene,
acrylonitrilelbutadiene/styrene (ABS), thermoplastic polyurethane
or blends of polycarbonate and ABS.
[0031] The production of multiple web panels by extrusion is
known.
[0032] According to the process of the invention a laser beam is
directed through the first horizontal chord onto the second
horizontal chord, and perforated. The wavelength of the laser beam
is preferably in the range from 800 to 1200 nm. Diode lasers or
Nd:Yag lasers for example are suitable as laser. The transparency
of the first horizontal chord must therefore be sufficiently high
that the laser beam passes through this substantially unhindered.
The laser beam is absorbed first by the second horizontal chord.
Due to the energy of the laser the material of the second
horizontal chord is locally combusted, resulting in the formation
of a hole. The laser energy is preferably 10 to 100 W.
[0033] By means of the laser a large number of holes may be
produced in the second horizontal chord. The production of the
holes may take place serially or sequentially.
[0034] During the perforation by means of the laser beam the upper
layer of the chambers between the first and second horizontal webs
is preferably subjected to compressed air from one of the two open
sides of the multiple web panel. Due to the resultant gas flow
through the chambers the combustion residues formed by the laser
irradiation are expelled, so that these may not settle on the walls
of the multiple web panel.
[0035] The process according to the invention is preferably carried
out directly after the extrusion of the inventive panel, which
means that the extrusion and the perforation of the panel take
place in one work stage. To this end a row of laser beams may be
arranged behind the extrusion nozzle in such a way that, when the
panel leaves the extrusion nozzle, the laser beams are directed
through the first horizontal web onto the second horizontal
web.
[0036] The process according to the invention is described
diagrammatically with reference to the figures.
EXAMPLE
[0037] FIG. 1 shows panel 10 with a first, 11, second, 12 and
third, 13 horizontal webs as well as vertical webs 15, positioned
perpendicularly to the horizontal webs. The inventive solar thermal
collector is open on the two sides lying opposite one another, i.e.
on the two surfaces 18, 19 aligned perpendicularly to the
horizontal and vertical webs. The first horizontal web 11 is
transparent enabling directing laser beams (not shown) through the
first horizontal web 11 onto the second horizontal web 12. The
direction of the laser beams is indicated by the arrow 20. The
laser beams pass through the first horizontal web 11 and are
absorbed by the second horizontal web 12, which for example is
colored with carbon black, holes (1) thereby being formed.
[0038] Such a multiple web panel was used as a solar-operated solar
thermal collector, with a first horizontal chord 11 (i.e. a
transparent horizontal web facing towards the sun) of polycarbonate
(available as Makrolon DP 1-1853 polycarbonate from Bayer
MaterialScience AG, Germany), which was covered with an outer UV
protective layer of Makrolon DP 1-1816 polycarbonate (a product of
Bayer MaterialScience AG, Germany), and a second horizontal chord
12 (i.e. an absorber surface) of non-transparent Makrolon 9415
polycarbonate (a product of Bayer MaterialScience AG, Germany). The
absorber surface was colored with carbon black.
[0039] The absorber surface was perforated by means of an Nd:Yag
laser with a wavelength of 1064 nm. The proportion of holes in the
total surface was 0.1%, and the holes were of 0.3 to 1 mm. in
diameters.
[0040] FIG. 2 demonstrates the use of the solar thermal collector
according to FIG. 1 using air as heat exchange gas. Sunlight 2
passes through the transparent first horizontal chord 11 and is
absorbed in the second horizontal chord 12 and heat energy is
formed.
[0041] Air enters through inlet 3 into the collector by suction
with blower 5, will pass through the holes 1 in the second chord 12
and leaves the chambers 8a via outlet 4.
[0042] Chambers 8 and 8a are closed at their respective ends 9 and
9a. The collector is part of a pumping circuit 6 which can be an
open or a closed loop. The heated air is guided through the solar
thermal collector 7, to use the collected heat.
[0043] Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood
that such detail is solely for that purpose and that variations can
be made therein by those skilled in the art without departing from
the spirit and scope of the invention except as it may be limited
by the claims.
* * * * *