U.S. patent application number 12/051456 was filed with the patent office on 2009-08-27 for reflector element for a solar heat reflector and the method for producing the same.
This patent application is currently assigned to RIOGLASS SOLAR, S.A.. Invention is credited to Ignacio Garcia-Conde Noriega, Josep Ubach Cartategui.
Application Number | 20090211569 12/051456 |
Document ID | / |
Family ID | 39683508 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090211569 |
Kind Code |
A1 |
Garcia-Conde Noriega; Ignacio ;
et al. |
August 27, 2009 |
REFLECTOR ELEMENT FOR A SOLAR HEAT REFLECTOR AND THE METHOD FOR
PRODUCING THE SAME
Abstract
Reflector element (1) for a solar collector which comprises a
not mechanically flexed monolithic glass pane (2) of heat treated
glass which due to its enhanced resistance properties becomes
self-supported without requiring the presence of any kind of frame
member or device to maintain its shape at the normal utilization
temperatures. The reflector element is substantially parabolic and
can be provided with at least one bore (3) for a fixing element to
fix the reflector element (1) to a supporting structure.
Inventors: |
Garcia-Conde Noriega; Ignacio;
(Asturias, ES) ; Ubach Cartategui; Josep;
(Asturias, ES) |
Correspondence
Address: |
MOORE & VAN ALLEN PLLC
P.O. BOX 13706
Research Triangle Park
NC
27709
US
|
Assignee: |
RIOGLASS SOLAR, S.A.
Santa Cruz de Mieres - Asturias
ES
|
Family ID: |
39683508 |
Appl. No.: |
12/051456 |
Filed: |
March 19, 2008 |
Current U.S.
Class: |
126/694 ;
427/165 |
Current CPC
Class: |
Y02E 10/40 20130101;
G02B 7/183 20130101; F24S 25/60 20180501; G02B 5/10 20130101; F24S
23/82 20180501; F24S 23/74 20180501 |
Class at
Publication: |
126/694 ;
427/165 |
International
Class: |
F24J 2/12 20060101
F24J002/12; B05D 5/06 20060101 B05D005/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2008 |
EP |
EP08380058.14 |
Claims
1. A reflector element (1) for a solar heat reflector comprising a
self-supported curved not mechanically flexed monolithic
heat-treated glass pane (2) and reflecting means.
2. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that the heat treatment process consists
of thermal heat strengthening.
3. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that the heat treatment process consists
of thermal tempering.
4. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that it is substantially parabolic.
5. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that it is provided with at least one
bore (3) for a fixing element to fix the reflector element (1) to a
supporting structure.
6. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that the thickness of glass pane (2) is
equal or less than 5 mm.
7. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that its energy reflectance (R.sub.E %)
is larger than 92% in the solar spectrum comprising 270 to 2500 nm,
with an air mass value of 1.5.
8. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that its light reflectance (RL.sub.D65%)
is larger than 94% in the solar spectrum comprising 270 to 2500 nm,
with an air mass value of 1.5.
9. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that when the glass pane (2) is thermally
heat strengthened, both reflector element surface sides have a
compressive layer with strength in a range between about 20 Mpa and
about 69 Mpa.
10. A reflector element (1) for a solar heat reflector according to
claim 1, characterized in that when the glass pane is thermally
heat tempered, both reflector element surface sides have a
compressive layer with strength in excess of 70 Mpa.
11. A solar heat reflector comprising at least one reflector
element (1) according to claim 1.
12. A solar heat reflecting installation comprising at least one
solar heat reflector according to claim 11.
13. Method for producing the reflector element (1) of claim 1
comprising the steps of i) cutting off an annealed glass, grinding
of the edges of the cut glass pane, ii) washing the glass pane,
iii) loading the glass pane in a bending furnace for its bending
until the desired curved shape, iv) heat treatment of the glass
pane by heating and rapid cooling in order to increase its
strength, v) cooling down the glass pane to normal handling
temperature, and vi) application of a reflective coating (10) and
protective layers (11-14).
14. Method according to claim 13 characterized in that the heat
treatment is thermal heat strengthening.
15. Method according to claim 13 characterized in that the heat
treatment is thermal tempering.
16. Method according to claim 13 characterized in that the bending
furnace bends the glass pane until a substantially parabolic
shape.
17. Method according to claim 13 characterized in that the step i)
of edge grinding additionally comprises the operation of drilling
bores (3) in the glass pane.
18. Method according to claim 13 characterized in that the step vi)
of application of a reflective coating (10) and protective layers
(11-14) comprises the following steps: a) preparation of the glass
pane by removing all impurities and minor surface defects on the
glass side to be coated, polishing and further warming up to a
temperature of about 25.degree. C., b) deposition of a layer of
metallic silver (10) c) allowing a reaction time and application of
an anticorrosion and antioxidant layer made of metallic copper
(11), d) allowing a reaction time, rinsing with water, air drying
and entering a heating tunnel for the final metal coats (10, 11)
drying, e) application of a "basecoat" paint layer (12), curing in
a infrared curing furnace and an cooling to reduce the glass pane
temperature prior to the next step, f) application of a second
layer of paint or "intermediate" paint (13), curing in a infrared
curing furnace and an cooling to reduce the glass pane temperature
prior to the next step, and g) application of a third layer of
paint or "top" coat (14), curing in a infrared curing furnace and
an cooling to reduce the glass pane temperature.
19. Method according to claim 18 characterized in that the step b)
of deposition of a layer of metallic silver (10) is made after two
solutions, a first solution of silver nitrate and a second solution
of a reducer, being both solutions independently sprayed and mixed
up on top of the glass pane surface (2).
20. Method according to claim 18 characterized in that the layer of
metallic silver (10) has a minimum thickness of 0.7 g/m.sup.2.
21. Method according to claim 18 characterized in that the step c)
of deposition of a layer of metallic copper (11) is made after two
solutions, a first solution of copper sulphate and a second
solution of a suspension of iron powder, being both solutions
independently sprayed and mixed up on top of the layer (10).
22. Method according to claim 18 characterized in that the layer of
copper (step c)) has a minimum thickness of 0.3 g/m.sup.2.
23. Method according to claim 18 characterized in that the dry film
thickness for the base coat (12) is in a range between about 20 to
45 micron, the dry film thickness for the intermediate paint (13)
is in a range between about 25 to 55 micron, and the dry film
thickness for the top coat (14) is in a range between about 25 to
55 micron.
24. Method according to claim 18 characterized in that the
reflecting coating and the protection layers are applied to the
convex side off the glass pane (2).
Description
TECHNICAL FIELD
[0001] The present invention relates to a reflector element for use
in a solar heat reflector or the like, a solar heat reflector
comprising at least one of those reflector elements, a solar heat
reflecting installation comprising at least one those solar
reflectors, and to a method of manufacturing the reflector
element.
DESCRIPTION OF RELATED ART
[0002] Technologically advanced societies have become increasingly
dependent on energy. As populations and living standards rise, the
demand for energy grows and this trend will continue in the future.
Consequently, the capability of a nation to satisfy its energy need
plays a crucial role in its economic output and in its inhabitants'
quality of life. Fossil fuels are currently the most used energy
resources. The dependence on these non-renewable exhaustible fuels
raises environmental concerns and is a source of regional and
global conflicts.
[0003] As the need for energy grows and the reserves of fossil
fuels are being depleted, governments all over the world are facing
the challenge of establishing initiatives to develop efficient
renewable energy technologies for the use and production of energy
obtained from natural sources such us wind, sunlight, tides, waves
or geothermal heat.
[0004] Sunlight is seen as one of the most promising among
renewable energy resources, since it is clean, reliable,
environment respectful, endless and free. Nevertheless, in order to
meet the world's growing energy needs, it is essential a further
development, both in research and applications, of technologies for
collecting, accumulating and harnessing solar energy, so costs are
reduced and efficiency improved, making this energy worldwide
competitive.
[0005] Electricity can be generated from the sun in several ways.
Photovoltaic systems, also known as PV systems, have been mainly
developed for small and medium-sized applications due to the high
price of photovoltaic cells although new multi-megawatt PV plants
have been built recently. For large-scale generation, concentrating
solar thermal power plants have been more common. These systems
comprise solar collectors which use lenses or mirrors to
concentrate a large area of sunlight onto a receiver, through which
a working fluid flows, which is heated before transferring its heat
to a boiler or power generation system.
[0006] Solar collectors are known in the art. They usually include
at least one mirror that reflects incident light to a focal
location such as a focal point or line. A solar collector can
include one or more mirrors that reflect incident sunlight and
focus the light at a common location. A cost-effective collector
consists of a linear parabolic reflector that concentrates light
onto a receiver positioned along the reflector's focal line. A
liquid (e.g., water, oil, or any other suitable thermal liquid) to
be heated, may be positioned at the focal point of the mirror so
that the reflected sunlight heats the liquid and energy can be
collected from the heat or steam accumulated by the liquid.
[0007] A conventional method to produce a parabolic reflector
consists on hot-bending. A glass substrate is bent on a
approximately parabolic shape mould using high temperatures and
once slowly cooled, a reflective coating is applied either on the
concave or the convex side of the bent glass substrate. A drawback
of a parabolic reflector thus produced is that the hot-bending may
cause some distortions which lead to optical deficiencies and sun
energy reflection loss. Other drawbacks are the low bent glass
production rate achieved when using this manufacturing methodology
and the low resistance of the glass panes to the wind loads and the
accidental impacts against them.
[0008] An alternative method for producing a parabolic reflector is
described in documents WO 2007/108837 and WO2007/108861. Said
method comprises forming a reflective coating on a flat glass
substrate, using a mould member to cold-bend the glass substrate
and applying a frame member to the cold-bent glass substrate to
mechanically maintain the cold-bent glass substrate in a bent
shape. By frame member it is meant any solid element which is
applied to the bent glass substrate in order to maintain it in its
bent shape and without which element the glass substrate would
recover its initial flat shape. For example a frame, an additional
pre-bent glass or metal sheet, or a thermoplastic member. The
method set forth in said documents has some limitations and
drawbacks, among which: [0009] The glass substrate must necessarily
be sufficiently flexible to be cold-bent, said flexibility being
usually provided by making a relatively thin glass substrate.
[0010] As abovementioned, parabolic reflectors produced by this
method need to be maintained in their bent shape by a frame member,
otherwise they would recover their flat shape.
[0011] Document U.S. Pat. No. 4,337,997 describes an alternative
energy reflector and a method for producing the same. In that case
a flexible glass substrate is included in a laminate with a metal
ply and the laminate is subjected to flexing forces, causing its
flexure within the elastic limit of the metal ply. The relative
thicknesses of the metal and glass plies and the bonding means
between them need to be suitably chosen, so the glass ply is not
subjected to tensile stress when the laminate is flexed.
[0012] In document JP57198403 a curved reflector is disclosed
including a mirror which comprises a thin plate-like chemically
tempered glass, a reflective coating and a protective coating,
which mirror is mechanically curved along the surface of a rigid
member at room temperature.
[0013] Chemical tempering strengthens glass by putting the surface
of the glass into compression, due to an exchange of ions. In a
chemical tempering process a piece of glass is submersed in a bath
of molten salt at a prescribed temperature. The heat causes the
smaller ions to leave the surface of the glass and the larger ions
present in the molten salt to enter it. Once the piece of glass is
removed from the bath and cooled, it shrinks. The larger ions that
are now present in the surface of the glass are crowded together.
This creates a compressed surface, which results in a stronger
glass with an increased resistance to breaking. This method of
chemical tempering is time-demanding, low manufacturing rated and
very expensive.
[0014] Ordinary annealed glass, without special treatment, is
widely used in the technical field of the invention. However, this
glass can become fragile when exposed to wind loads, impact of
solids in the open air and when be provided with bores it cannot
bear the necessary mounting or fixing stresses.
[0015] Therefore it is an object of the present invention to
provide an improved reflector for a solar heat collector, which
solves the abovementioned drawbacks present in the reflectors
comprised in the prior art, i.e., a reflector with the appropriate
optical properties, resistant and which does not require the use of
a frame member to maintain its curved shape. A second object of the
present invention is to provide an efficient method for producing
such a reflector, which is cheap, simple and reproducible.
SUMMARY OF THE INVENTION
[0016] This and other objects of the invention are achieved by a
reflector element for a solar heat reflector according to
independent claim 1, a solar heat reflector according to
independent claim 11, a solar heat reflecting installation
according to independent claim 12 and a method for producing a
reflector element for a solar heat reflector according to
independent claim 13. Favourable embodiments are defined by the
dependent claims.
[0017] A solar heat reflector according to the invention comprises
a number of reflector elements which forms a substantially
parabolic reflecting surface that reflects and concentrates
incident sun radiation to a focal receiver which performs as a heat
collector. Normally the heat reflector comprises four reflector
elements following a substantially parabolic curve.
[0018] According to a first aspect of the invention, a reflector
element for a solar heat reflector is provided, which comprises a
self-supported curved not mechanically flexed monolithic piece of
heat-treated glass pane and reflecting means.
[0019] The term `not mechanically flexed` shall be understood
throughout this document as a glass pane which is not flexible in a
static situation and cannot be cold-bent, maintaining the desired
and preformed curved or bent shape without the use of a frame
member, rigid member or any other external force. These frame or
rigid members has been used in the prior art to maintain the shape
of the glass once this has been mechanically cold-bent.
[0020] `Monolithic` shall be understood throughout this document as
a glass pane made of a single piece of glass in opposition to a
multi-piece glass, such as laminated, that is composed of at least
two glasses and one or several interlayer resins.
[0021] Heat-treatment of glass involves heating the glass to a
temperature near its softening point and forcing it to rapidly cool
under carefully controlled conditions. Heat-treated glasses can be
classified as either fully tempered or heat strengthened, according
to their surface compression degrees. The heat-treating process
produces highly desirable conditions of induced stress which result
in additional strength--achieving up to six times that of the
normal annealed glass--, resistance to thermal shock and impact
resistance. These improved conditions are especially advantageous
for a reflector element to be used in a solar heat reflector
located in the open air, usually in desert regions, where the
collector is subjected to huge temperature variations and high wind
loads in those large open spaces.
[0022] The heat-treating process for either, tempering or
heat-strengthening glass, confers enhanced resistance properties to
the reflector element of the invention. During said process, once
the piece of heat-treated glass pane has been softened, it is bent
in a continuous process to a curved shape suitable for a solar heat
collector. The reflector element is preferably bent in a
substantially parabolic shape but other shapes--such as cylindrical
or spherical--can be envisaged for different embodiments of the
invention.
[0023] `Substantially parabolic` shall be understood throughout
this document as any transversal section of the reflector element
of the invention that has a substantially parabolic shape. Such
`substantially parabolic` shape can be characterized by the
intercept factor (IF). This factor is defined by the percentage of
the whole incoming solar radiation that strikes the reflector and
that is reflected on a tube of a 70 mm diameter (the linear
receiver or absorbing tube) with its axis located along the
theoretical focal line of the solar heat reflector. The IF factor
of the reflector elements produced by the method herein described,
have a minimum value of 95%.
[0024] In this sense a `self-supported` glass pane shall be
understood throughout this document as a glass pane which does not
require the cooperation of a frame member or any other device to
maintain its shape at the normal utilization temperatures, and that
it is kept in its working position by the supporting structure. The
absence of a frame member or other device in the reflector element
of the invention to keep its curved shape results in material,
money and time saving in its manufacturing and also has the
advantage of a smaller weight and maintenance cost of the solar
heat reflector.
[0025] A further advantage of the reflector element of the
invention is that it comprises a monolithic glass, i.e. no
lamination or combination of glass with other glass panes or other
materials is needed.
[0026] The glass pane of the reflector element for a solar heat
reflector according to the invention has preferably a thickness of
equal or less than 5 mm, although thicker glass panes can be
manufactured and used as reflectors in accordance with the
invention.
[0027] The reflector element of the invention also comprises
reflecting means, such as a reflecting coating or a layer of a
reflecting element deposited either on its concave or convex side,
the reflecting capabilities being provided by one or more coating
layers, covered by one or more protecting layers of a protective
element such as paint coats or adhesive films. The purpose of such
protection layers being the preservation of the reflective
behaviour of the reflector elements and the increase of the
duration of the reflective coatings of the reflector element,
normally installed in places where it is exposed to very aggressive
environmental conditions.
[0028] When a reflective coating layer is applied on the convex
side of the curved glass pane, the first protection layer of the
reflector element of the invention comprise an antioxidant or
passivation layer, chemically deposited directly on top of the
reflecting layer, and on top of this first protection layer, an
additional second or even more layers of paint are sequentially
deposited to increase the weather resistance and durability of the
reflecting layer.
[0029] The reflector element provided by the present invention has
optimal optical properties, such as solar energy reflectance
(R.sub.E %) larger than 92% and light reflectance (RL.sub.D65%)
larger than 94% in the solar spectrum comprising 270 to 2500 nm,
when measurements are made in accordance with ISO 9050:2003 with an
1.5 air mass value.
[0030] When thermally heat strengthened, the reflector element has
compressive layers in both surfaces between 20 Mpa and 69 Mpa,
resulting in improved mechanical properties with respect to typical
annealed glass reflectors in use.
[0031] When thermally tempered, the reflector element has
compressive layers in both surfaces in excess of 70 Mpa, resulting
in improved mechanical properties with respect to typical annealed
glass reflectors in use.
[0032] Due to its mechanical properties the reflector element of
the invention can be provided with at least one bore without
fracturing when submitted to mounting stresses. Said bore can be
advantageously used to fix the reflector element to a supporting
structure in the solar heat reflector by means of a fixing element
and can have different diameter values depending on the required
attachment of the reflector element to its supporting
structure.
[0033] Other reflectors in the prior art would be easily fractured
when submitted to mounting stresses in the bores, and therefore
they need to be fixed to supporting structures via adhesive means,
which are known to degrade when exposed to the ultra-violet sun
radiation and the unfavourable environmental conditions typically
found in the locations where solar heat collecting facilities use
to be installed.
[0034] A second aspect of the invention is to provide a solar heat
reflector comprising at least one reflector element according to
the invention.
[0035] A third aspect of the invention is to provide a solar heat
reflecting installation comprising at least one solar reflector
according to the invention.
[0036] A fourth aspect of the invention is to provide a method for
manufacturing the reflector element of the invention.
[0037] A flat annealed glass is cut by several potential means,
such as diamond cutting wheel, milling, water jet, etc, to its
desired perimeter shape and dimensions and then grinded to either
flat or curved edge finishing. This edge grinding operation
prevents glass from stress breaking due to the small surface cracks
that normally appear on the glass edge in the cutting operations.
After the edge grinding, one or more bores can be drilled in the
glass plane depending on the reflector attachment method to its
supporting structure. The edges of the holes in every side of the
glass can be countersunk to smooth away the mechanical stress of
the fixing devices that will be fixed through them.
[0038] As all these mechanical operations on glass are finished,
the glass is carefully washed and dried. In the washing operations
a common water washing is firstly conducted to remove sand glass
coming from the edges' grinding and immediately after a
demineralised water rinse is made to prevent water salt pollution
deposits on the glass surfaces.
[0039] Drying of the glass is normally made by means of high speed
cold or hot air angled projection on the glass surfaces.
[0040] The glass cut, edge grinded, drilled and cleaned is loaded
on a bending furnace to conduct its bending and thermal stress
treatment.
[0041] The glass is properly positioned on the loading table of the
heating oven and progressively heated to its bending temperature by
continuous, or step-by-step, travelling through the heating tunnel.
Radiation with electrical heat sources or convection by means of
hot air heating can be used to heat up the glass. As the glass
reaches the desired temperature, it is rapidly moved to the bending
section, where the glass is bended to its desired curved shape and
immediately heat strengthened or tempered (heat treatment) with
rapid cooling by means of violent air blowing on both glass sides.
After this heat treatment the glass is cooled down to a normal
handling temperature (under 50.degree. C.) by continuous or
discontinuous travelling in a cooling tunnel where it is blown with
atmospheric air coming from one or several fans. Compressed air can
also be used to apply cooling for strengthening of the glass.
[0042] Glass handling is made with special automatic or manual
devices that allow easy displacement when loading and unloading
operations are carried out.
[0043] All cutting, grinding and drilling operations are conducted
on numerically controlled (NC) automatic machines. Also speed,
water and air temperature in the washing and drying operations are
PLC (programmable logic controller) controlled.
[0044] All these operations, including bending and tempering, are
carried out in specific equipments which, in some way, are similar
to those used in the glass industry such those used in the
manufacturing of heat-treated glass, well known to the skilled
person, like for example in the automobile industry.
[0045] Furnace parameters (glass speed, temperatures, bender
operation, air pressure, etc), furnace operations and their
coordination are fully automatic and controlled by means of a
sophisticated computer control system.
[0046] The bent glass is then moved to a coating line to provide it
with the necessary reflective capabilities, conducting a mirroring
process, but specifically adapted to curved parabolic shape glass
panes.
[0047] On the convex side of the bent glass, a reflective coating
process is conducted comprising the application of a reflective
layer, anti-oxidation or passivation layers, and several protective
layers.
[0048] These and other aspects of the invention will be apparent
from and elucidated with reference to the embodiments described
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] The invention will be better understood and its numerous
objects and advantages will become more apparent to those skilled
in the art by reference to the following drawings, in conjunction
with the accompanying specification, in which:
[0050] FIG. 1 shows top and side views of the parabolic reflector
element of the invention.
[0051] FIG. 2 shows the principle of reflection of an incident
solar ray in a parabolic reflector element and the corresponding
absorbing tube.
[0052] FIG. 3 shows top and side views of a reflector element with
conventional mounting means.
[0053] FIG. 4 shows a preferred configuration of the reflective and
protection layers applied to the reflector element's convex
side.
[0054] Throughout the figures like reference numerals refer to like
elements.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0055] In FIG. 1 a reflector element (1) for a solar collector
according to a preferred embodiment of the invention is shown in
both, top and side--section AA--views. Said reflector element
comprises a not mechanically flexed monolithic glass pane (2) of
heat treated glass which due to its enhanced resistance properties
becomes self-supported without requiring the presence of any kind
of frame member or device to maintain its shape at the normal
utilization temperatures. The principle of reflection of an
incident solar ray (6) in a reflector element (1) and the
corresponding absorbing tube (5) is shown in FIG. 2.
[0056] In an embodiment the thickness of the glass pane is equal or
less than 5 mm.
[0057] FIG. 3 shows the reflector element (1) of the invention and
a detail of a conventional mounting means (7) for fixing the
reflector element (1) to a solar heat reflector's structure. These
conventional mounting means (7), which do not require bores in the
reflector, comprises supporting pads (8) for installation on the
collector structure attached to the reflector element's back
surface (convex face) via an adhesive material (9). These mounting
means are perfectly usable in the reflector element of the
invention.
[0058] In a further embodiment four bores (3) have been made
through the glass pane thickness (2) to provide housing for
mounting elements through which the reflector element (1) will be
fixed to the solar collector structure. One detail of a bore (3) is
shown in FIG. 1.
[0059] On the convex face of the glass pane (2), a reflective layer
(10) made of chemically deposited silver, an antioxidant or
passivation layer made of chemically deposited copper (11), and
three layers (12-14) of paint have been applied to provide the
reflecting and weathering endurance characteristics to the
reflector element.
[0060] In FIG. 4 the composition of the reflective (10) and
protective layers (11-14) applied to the reflector element's convex
face according to a preferred embodiment of the invention are
shown.
[0061] The method of producing the reflector element of the
invention comprises the steps of: [0062] cutting off an annealed
glass, [0063] grinding the edges of the cut glass pane, [0064]
washing the glass pane, [0065] loading the glass pane in a bending
furnace for its bending until the desired curved shape, [0066] heat
treatment of the glass pane with rapid cooling in order to increase
its strength, [0067] cooling down the glass pane to normal handling
temperature, and [0068] application of a reflective coating.
[0069] In a particular embodiment the heat treatment is thermal
heat strengthening or thermal tempering.
[0070] In a particular embodiment the step of edge grinding
comprises the operation of drilling bores (3) in the glass pane
(2). These bores (3) will be used by the corresponding mounting
means to fix the reflector element to the solar heat reflector's
structure.
[0071] In turn, the application of a reflective coating (10) and
its protective layers (11-14) comprises the following steps.
[0072] The first step in the manufacture of the reflector element
is the removal of all impurities and minor surface defects on the
glass side to be coated. This is achieved by using a water
suspension of a polishing material such as Cerium Oxide (CeO) in
combination with water. The polishing is performed by feeding the
polishing means into a station equipped with brushes that describe
both, rotation and side to side movements. After the polishing
operation is performed, the residual polishing powder is removed by
demineralised water rinsing.
[0073] Glass sheets are then warmed up to near 25.degree. C. by
rinsing with hot water and then sprayed with a promoter adhesion
solution made of Tin Chloride salt in water.
[0074] After water rinsing, the reflective layer (10) is created.
The reflective surface (10) is composed of a chemically deposited
layer of metallic silver that is created after two solutions. The
first one is made of Silver Nitrate and the second one is made of a
Reducer. Both are independently sprayed and mixed up on top of the
glass surface. After allowing a reaction time, typically 1 to 2
minutes, glasses are rinsed with demineralised water followed by
the application of an anticorrosion and antioxidant layer made of
metallic Copper (11).
[0075] In a particular embodiment the layer of metallic silver (10)
has a minimum thickness of 0.7 g/m.sup.2.
[0076] The Copper (passivation) layer (11) is deposited after two
water solutions; the first one containing copper sulphate and the
second one being a suspension of iron powder. They are
independently sprayed and mixed up on top of the previous
reflecting layer (10). After allowing a reaction time of 1 to 2
minutes, glasses are rinsed with water and air dried before
entering a heating tunnel for the final metal coats (10, 11)
drying.
[0077] In a particular embodiment the layer of copper (11) has a
minimum thickness of 0.3 g/m.sup.2.
[0078] Further, the protective layers (12-14) of paint are applied
on top of the metal coats (10, 11) described.
[0079] The first out of three layers of paint or "basecoat" paint
(12) is applied via a curtain coater followed by the corresponding
infrared (IR)-curing furnace and an air cooling tunnel to reduce
the glass temperature prior to the next step. In a particular
embodiment the dry film thickness for the base coat (12) ranges
from about 20 to 45 micron.
[0080] The second layer of paint or "intermediate" paint (13) is
also applied in a curtain coater followed by the corresponding
IR-curing furnace and an air cooling tunnel. In a particular
embodiment, the dry film thickness for the intermediate paint (13)
ranges from about 25 to 55 micron.
[0081] The third layer of paint or "top" coat (14) is also applied
in a curtain coater with its corresponding IR-curing furnace and an
air cooling tunnel. In a particular embodiment, the dry film
thickness for the top coat (14) ranges from about 25 to 55
micron.
[0082] Once all the layers (10-14) composing the final mirror have
been deposited, the reflector element goes through a final washing
station provided with demineralised water, to remove any
contamination caused during the process on its opposite, non-coated
side, and then trough an air drying station to remove the moisture
from the previous washing step.
[0083] After the coating process, the glass panes are moved to the
fitting section where the fixing accessories are mounted of the
glass panes by means of robotized equipment for an accurate, easy,
rapid mounting of the fixing hardware on the calculated points of
the reflector element for its attachment to the solar heat
reflector' structure.
[0084] Finally the glass panes are safely packed and stocked for
shipment to their final destination in the solar collecting
facilities.
* * * * *