Note: Descriptions are shown in the official language in which they were submitted.
CA 02691856 2009-12-24
Roof structure for a solar system
The invention relates to a roof structure for
photovoltaic generation of electric current and/or for
heating a flowing medium, in particular an airflow. The
roof structure also serves as a whole for all the
general functions of a roof.
The use of the daily incident solar radiation of roofs
and facades of inhabited and uninhabited buildings for
the purpose of obtaining energy in the form of electric
current and heat has already acquired great
significance.
Because of the finite nature of fossil energy sources
and of uranium, the exploitation of inexhaustible
energy sources such as those of the sun is of great
importance for our future power supply.
The reduction of combustion and/or increased use of
fossil energy sources is also necessary on ecological
grounds.
Developments of recent years have shown that solar
current and heat can be obtained on a large scale. Even
today the annular production of solar cells for power
generation is over 1400 MW, corresponding to an area of
approximately 14 km2. The present annual growth rate is
approximately 40%. By 2004 nearly 6 million mZ of
collector area had been installed on roofs in Germany
alone for the purpose of obtaining heat. This area is
to be doubled by 2012.
While photovoltaic modules are now being mounted in
larger numbers on roofs, it has become normal to cover
roof segments with thermal collectors by laying water
carrying absorbers. However, for reasons of cost and
esthetics the technical development is leading
increasingly to the integration of the solar systems in
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the roof skin, facades and skylights and shading
devices. In addition, the photovoltaic modules and
thermal collectors are also taking over the usual
function of roofs and facades.
Increasing use is being made of large area photovoltaic
roof elements as a "solar roof" for the roof structure.
The German company SUNWORLD AG is marketing an
appropriate solar roof. It is necessary to take
specific, complicated measures for fastening, but above
all for attaining waterproofness (side and transverse
profiles, rubber seals etc.). Separately therefrom,
thermal, mostly water carrying solar collectors are
being installed on or in the roofs. Also known are so
called air correctors that are used as roof structures
chiefly for drying hay with the aid of the warm air
generated. A very esthetic design of overlapping
roofing shingles for photovoltaic current generation is
known from US. 5 990 414 A.
The photovoltaic modules or roof elements themselves
consist essentially of thin, fragile silicon solar
cells of flat design in the form of strips or plates.
For the purpose of protection against mechanical and
chemical damage, the cells are embedded in an elastic
transparent material, usually EVA (ethyl vinyl acetate)
between the front, transparent front side of hardened
glass or plastic, and a rear sheet or glass. The solar
cells are interconnected electrically such that the
module voltage generated can be tapped via an appliance
outlet, mostly arranged at the rear. A multiplicity of
such modules or roof elements are connected in series
and in parallel, in order to obtain the respectively
desired system voltage/DC power. The current is mostly
fed into a public grid via an inverter, or buffered in
batteries in the case of small island systems.
Thin layers are known that are made from amorphous
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silicon, CulS2, or other semiconducting materials or
chemical compounds that are likewise used to construct
modules or roof and facade elements. These layers are
applied to glass or transparent plastic, plastic sheets
being used on the front and/or rear for protection
against mechanical or chemical influences.
Solar systems, in which insulation is used for the
purpose of heating flows of water or air carried in
pipeline systems and current is simultaneously
generated by means of photovoltaics are known, though
scarcely used to date. The total cost of such roofs
fitted with solar systems is very high, and casts doubt
on an important advantage of multifunctionality. The
functionality and heat yield are unsatisfactory, just
as are the esthetic factors and suitability for
construction of standard roofs. Again, the known
systems are not suitable for the mass production that
is required to lower the costs of power generation.
They mostly also have complicated structures for
integration in the roof. The roof elements that obtain
power, which can replace conventional roof elements
(tiles, shingles etc.) would need to be able to be
designed and installed cost effectively. All the
factors mentioned impair the cost effectiveness of
obtaining power and heat in combination.
The object of the present invention is therefore to
provide a roof structure of the type mentioned at the
beginning that enables decisive cost reductions in
conjunction with high operational reliability, and
includes the advantages of multifunctional power
generation without neglecting the esthetic requirements
of the roofs built. Furthermore, it is the object of
the invention also to provide cost effective solutions
for the roof elements that obtain energy.
The object is achieved in accordance with the invention
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by virtue of the fact that glass roof panels that are
transparent or equipped at least partially with solar
cells of flat design and form an airtight flat gap
which is largely free of obstructions in the flow
direction laid and sealed at a spacing from a subroof.
Specific and developing embodiments are the subject
matter of dependent patent claims.
The flat gap preferably has at least one entrance
opening for the cold air, at least one exit opening for
the warm air and an airtight outer roof edge surround
or airtight lateral boundaries of the flat gap.
Guided through the flat gap is an airflow that is cold
when introduced and heated and outlet again into the
atmosphere when used. In certain instances, it is also
possible to install closed circuits that are operated
with air or another gaseous medium.
The expression, generally used here, "glass roof
panels", fully having the function of roof elements -
for example for substitution of roof tiles, roof
shingles etc. - also covers panels made from all other
suitable transparent materials.
The spacing between the subroof of flat design (without
the usual roof ribs) and the glass roof panels is
preferably in the range of 15-30 mm. The spacing is
determined on the basis of design parameters such as,
for example, the desired temperature rise, height of
the roof, expected thermal efficiency and the air speed
determined.
According to one variant, the flat gap can widen
upward. This is the case, in particular, when the glass
roof panels, and thus the roof or the roof part itself
narrow upward (pitched roof).
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The glass roof panels of rectangular or square design
fulfill the function of roofing materials, in
particular of tiles.
In the case of glass roof panels of rectangular design,
these are laid in an overlapping fashion and sealed
with known means such that an airtight flat gap is
ensured. Longitudinal profiles are constructed at the
side and ensure tightness, maintenance of the spacing,
and fastening. In the case of rectangular,
nonoverlapping glass roof panels that abut one another,
the sealing is with rubber profiles and longitudinal
profiles that prescribe the abovementioned spacing of
15-30 mm and enable the panels to be fastened.
A particular refinement of the inventive roof structure
comprises specially designed square glass roof panels
that are laid with their diagonals in a vertical
direction and in a fashion overlapping on both sides.
Cost savings result, in particular, from the fact that
rain water is certain to flow off without further
measures, that is to say profiles and the like for the
lateral sealing of the panels can be eliminated. This
design is particularly suitable for mass production and
is exceptionally cost effective to lay.
The square glass roof panels are esthetically
attractive as roof elements and are used for covering
the entire roof including possible adjacent roofs (also
without power being obtained). In addition to functions
that obtain current and heat, they are also configured
according to the invention for the incidence of light
(skylight function), including in combination with the
power generation as translucent roof elements.
According to a further laying variant, the glass roof
panels can, however, always be sealed, laid and
supported on a plane or in the form of a shingle roof
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while being held with a frame. For its part, the frame
comprises fastening feet that are not allowed to impede
the throughflow of air.
Since the glass roof panels laid in accordance with the
invention replace a conventional roof, these are always
watertight in the case of storm gusts and fulfill the
snow load regulations. It is also possible to walk on
the glass roof panels.
According to the invention, these glass roof panels can
be used as follows for the roof structure:
^ as conventional glass roof panels - transparent
or opaque - for covering roof parts without use
for power. This holds, in particular, for the
square roof panels that are esthetic and easy to
install. The preferably doubly overlapping glass
roof panels are fastened at the four corners on
the subroof and simultaneously pressed onto one
another in order to attain tightness.
^ As thermal glass roof panels for thermal use by
heating the airflow in the air gap thereunder.
In this case, the glass roof panels are
transparent for full solar radiation. The
radiation is absorbed by a selectively coated
absorber that serves for directly efficient
heating of the air to high useful temperatures
(up to 100 C).
^ As photovoltaic glass roof panels with and
without simultaneous thermal use. If no heat is
obtained with the aid of the airflow in the gap
therebehind, this is suitable for performance
enhancing cooling of the cells. The air is
heated at the rear side of the glass roof
panels, useful temperatures of up to
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approximately 55 C being attainable.
^ As transparent glass roof panels with a skylight
function.
^ As partially transparent glass roof panels for
photovoltaic power generation (skylight shaded
by the cells), subroof transparent, or only with
the roof girders.
^ As partially transparent glass roof panels for
photovoltaic and thermal power use.
The roof structure can be installed in the form of roof
sections with only a thermal function, only an
electrical function, only a skylight function with an
electrothermal function (air temperatures of up to
55 C), and in the form of downstream, purely thermal
glass roof panels for obtaining high temperatures at
the output. The thermal roof panels therefore act as a
"booster". Further combinations for the use of the
glass roof panels are likewise possible in conjunction
with the transparent or partially transparent
properties.
Particularly with the preferred roof structure
consisting of the square, esthetic glass roof panels,
there is the possibility of building ultramodern
multifunctional roofs in the case of which power is
produced simultaneously and fossil fuels are replaced
for obtaining heat. Given the installation of dozens of
square kilometers, interesting prerequisites for large
scale economic use of solar energy can be attained
worldwide by the mass production of these roof elements
in combination with thermal use. In Switzerland alone
it is possible to switch fully to inexhaustible
environmentally friendly energy sources if as little as
10% of the areas of roofs and facades of the presently
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existing total area of 700 km2 is used. Currently,
12 km2 of roofs are built or renovated annually in
Switzerland. In Germany the abovementioned numbers are
tenfold.
The embodiments of the various glass roof panels are
described below with reference to the example of the
square doubly overlapping glass roof panels.
^ Glass roof panel with simple roof function. This
consists of a front hardened glass roof panel with
a sheet, laminated on the rear, for coloring, as
well as the fastening elements and pressure
elements at the four corners. However, other
materials can also be used for this function with
the same geometric structure and fastening
technique.
^ If the glass remains transparent, the glass roof
panel can be used with skylight function.
^ Glass roof panel with purely thermal function.
This consists of hardened glass with the same
geometric structure and fastening technique.
^ Glass roof panel with photovoltaic function. This
consists of a photovoltaic cell laminate in
accordance with the layer assembly (silicon cells
or thin-layer cells) described at the beginning.
^ Glass roof panel with photovoltaic function and
passage of light, as well as the same geometric
structure and fastening technique. These consist
of a photovoltaic laminate in accordance with the
layer assembly described at the beginning, the
solar cells being interconnected electrically with
the maintenance of a spacing between the cells for
the purpose of transmitting light. The geometric
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structure and fastening technique once again
remain the same.
Conventional thermal collectors for producing hot water
and for assisting heating with necessary installation
of metallic absorbers with the associated water
carrying tubes, or even vacuum collectors for
"gathering in" sunbeams over an entire area are more
expensive by a multiple than the inventive absorbers of
solar radiation over the same area with an airflow and
downstream heat exchanger for transferring the heat to
the fluid medium. In the case of the photovoltaic roof
panels, the investments for the simultaneous heating of
the airflow have, in addition, already been made, the
costs for a conventional roof element having been
deducted.
However, good heat transmission is a prerequisite for
an effective transfer of heat from the photovoltaic
roof panels to the air circulating therebehind. For the
inventive roof structure, the gap width between panel
and subroof is preferably, as mentioned, 15 - 30 mm,
depending on the definition of the decisive design
parameters.
In order to maintain the air temperature at the exit,
the air speed or flow rate is preferably regulated with
the aid of a ventilator that is controlled by a solar
sensor or driven with solar cells.
According to one variant, for the purpose of further
temperature increase, for example above the
photovoltaic roof panels, it is expedient to dispense
with the installation of solar cells and to arrange the
transparent thermal glass roof panels. In this case,
the radiation passes through the glass roof panel
directly onto a selective absorber sheet thereunder
past which the air flows and is heated. A selective
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absorber has the property that the solar radiation
(shortwave) is virtually completely absorbed (black
body), while the thermal emission of the hot absorber
is avoided as far as possible. This is achieved by
virtue of the fact that the absorber sheet has a low
emission factor for the emission at longer wavelengths.
The selective sheet is, for example, a solid sheet of
ceramic and metal termed CERMET. The coated absorber
sheet is long lived and heat resistant. It can be
touched, cleaned, shaped, welded and riveted. The
absorption factor is 95%, the emission factor only 5%.
These requirements are fulfilled, for example, by the
product Sunselect from Interpane Solar GmbH & Co. in
Germany.
If the selective absorber sheet is fastened on the
subroof, the air flows between it and the transparent
glass roof panel. The thermal efficiency, and thus the
attainable air temperature are less than when the air
flows through behind the selective absorber sheet. The
absorber sheet is preferably fitted at a spacing of
approximately 10 mm below the transparent glass roof
panel.
In a preferred variant, the heated air flows in the
gable region directly through an elongated air/water
heat exchanger running along the gable. Air, for the
most part cooled, is caught by collecting channels
downstream of the exchanger and, for example, guided by
means of a ventilator operated by solar cells directly
into the ambient air or - if still being used for
heating purposes - into the interiors. In certain
applications, an airflow supported and regulated by a
ventilator is not required, since the uplift resulting
from the heating of the air is sufficient to guide the
hot air through the heat exchanger arranged along the
gable.
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According to a further variant, the exiting hot air is
guided via a pipeline system to an air manifold heat
exchanger outside the roof region, where a water
circuit is expediently heated, in turn. The residual
heat can be used for further useful purposes before it
is outlet into the atmosphere as expulsion air.
The advantages of the inventive roof structure are
evident, reference has already been made above to the
applications for using the heat and to the cost
advantages, in particular there is no need for
expensive pipeline systems to be laid in the entire
roof region, and the continuously open flat gap
requires far lower investment costs and makes no demand
on maintenance.
The invention is explained in more detail with the aid
of exemplary embodiments that are illustrated in the
drawing and are also the subject matter of dependent
patent claims. In the drawing,
figure 1 shows a vertical section through half a solar
roof with overlapping glass roof panels,
figure 2 shows a variant in accordance with figure 1,
with glass roof panels laid in a flat fashion
and a ventilator,
figure 3 shows a detail III of figure 2 with a
standard type support,
figure 4 shows a roof gable with a heat exchanger,
figure 5 shows a variant in accordance with figure 4
with an air manifold heat exchanger,
figure 6 shows a view of a specimen roof with five
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laying variants R-V,
figure 7 shows a partial vertical section through the
laying variant S,
figure 8 shows a partial vertical section through the
laying variant V,
figure 9 shows a laying variant with square glass roof
panels set on end,
figure 10 shows a laying variant of the glass roof
panels in the form of a shingle roof,
figure 11 shows a flat laying of the glass roof panels
in accordance with figure 2,
figure 12 shows a laying variant of tapering glass roof
panels for a pitched roof,
figure 13 shows a partial section through a glass roof
panel,
figure 14 shows a variant in accordance with figure 13,
figure 15 shows a further variant of a glass roof
panel,
figure 16 shows a plan view of a roof glass panel with
tightly arranged solar cells,
figure 17 shows a plan view of a translucent glass roof
panel, and
figure 18 shows a view of a solar roof with glass roof
panels set on end.
Figure 1 shows a roof structure 10 for a solar system
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for the photovoltaic production of electric current
and/or for heating a cold airflow 14. The roof
structure 10 is arranged removed in a parallel fashion
by a spacing a from a subroof 14. The spacing a is
approximately 20 mm here.
The subroof 12 and the roof structure 10 form a flat
gap 18 that is virtually free from obstructions in the
flow direction 16 and in which the cold air 14 is
continuously heated, exits as a hot airflow 20 into a
gable space 22 and is fed from there directly to a
further use.
It is of substantial importance that the flat gap 18
extends over the entire roof structure (saving of roof
ribs), and that there are no substantial obstructions
in the flow direction 16. The flat gap 18 is sealed in
the outermost region of the roof structure with the
entire circumference or a part thereof. It is thus
possible for a natural flow to build up in the
direction 16 and heat the cold air 14, which expands
and rises in the flow direction 16 because of the lower
density.
A filter 15 is also expediently arranged at the
entrance opening for the cold air 14. The hot airflow
20 exiting in the gable space 22 can be used directly
for drying.
Figure 2 differs from figure 1 particularly in that the
glass roof panels 24 are not arranged in an overlapping
fashion, but on a plane, again at the spacing a from
the subroof 12. The glass roof panels 24 are held by
standard-type supports 26 of small flow cross section
at the spacing a. The airflow in the direction 16 is
assisted by at least one ventilator 28 in the gable
space 22. This ventilator 28 is connected to at least
one exit opening of the hot airflow 20 via a suction
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tube 30. A variant that is not illustrated serves for
regulating the ventilator performance. The ventilator
can also be driven directly by solar cells, as a result
of which a sensor is eliminated. Both variants serve to
maintain the temperature level under varying radiation
conditions.
Figure 3 illustrates in detail a standard-type support
26 anchored in the subroof 12. A screw 36 with a
peripheral bearing flange 32 and a guide arbor 34
ensures the setting of a flat gap 18 in the
abovementioned region of, expediently, approximately
mm. The mounted glass panels 24 are secured with a
head screw. The laminate structure of the glass roof
15 panels 24 is shown in figures 13 to 15.
The gable space 22 illustrated in figure 4 and that can
also be configured as a manifold, includes a heat
exchanger 40 that is connected upstream of the
ventilator 28 (figure 2), in the hot airflow 20. The
heat exchanger absorbs a substantial fraction of the
heat content of the air and feeds the latter to a water
circuit 42 in a way known per se. Said circuit
comprises a supply lead 44 and a down lead 46, for
example in a hot water or heating circuit. Opening into
the gable space 22, which is sealed in an airtight
fashion, is an exhaust-air line 50 through which the
still hot air can be fed to a further use. According to
one variant, the still hot air exits as expulsion air
into the external atmosphere via an exit opening
indicated by an arrow 52. The airflow can be deflected
or split up with a baffle 54.
Figure 5 shows the further course of the exhaust-air
line 50. After the baffle 54 is opened, the entire hot
airflow 20 flows to an air manifold heat exchanger 56
where the heat content of the air is, once again,
absorbed for the most part by a water circuit 42. The
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hot airflow 20 exiting from the air manifold heat
exchanger 56, which has been cooled but is still hot,
passes into the atmosphere as expulsion air 58, or is
fed to a further use 60.
Figure 6 shows a view of a virtual roof structure 10.
In other words, figure 6 corresponds not to a roof that
is customary in practice, but to a specimen roof with
as many variants as possible. Each of the variants R,
S, T, U and V would correspond in practice to a roof or
a roof segment.
- Variant R. Here, the glass roof panels 24 are
arranged with a photovoltaic function over the
entire roof height. The heating of the air in the
rear gap is performed by the heat transfer of the
glass roof panels 24, which have a temperature of
up to 70 C when the sun is shining. The useful
heat thereby obtained comes in at a temperature
level of 45 - 60 C.
- Variant S. Here, the roof consists in the lower
part of glass roof panels 24 with a photovoltaic
function. In the upper part, the air flows under
glass roof panels 24 with a purely thermal
function. The solar radiation strikes selective
absorber sheets such that the airflow is further
heated depending on whether it is guided past the
front or rear side of the selective sheet up to a
temperature of 60-80 C.
- Variant T. In the case of this roof structure,
glass roof panels 24 with a purely thermal
function are used over the entire roof height such
that high temperatures of up to 100 C are
attained.
- Variant U. Here, use is made of glass roof panels
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24 with a photovoltaic function and translucent
properties. Sunlight enters between the solar
cells 60, which are electrically connected at a
certain spacing. In this roof area, electric
current is generated and the translucent glass
roof panels 24 also take over the function of
shaded sky lights. If the selective sheet is used
in the air gap, the skylight function is dropped
in favor of the generation of heat. The
temperature level attained in this case for the
useful heat is somewhat higher, owing to the
additional incidence of light, than for the glass
roof panels 24 with only power generation.
- Variant V. Here, glass roof panels 24 with a
purely thermal function are used in the upper roof
region for the production of heat.
Of course, yet further variants are possible, and
individual variants can be combined with one another.
In particular, glass roof panels 24 with a skylight
function (roof window) can be installed, or the glass
roof panels 24 can be coated black without solar cells
being installed.
Figure 7 shows a partial longitudinal section through
variant S in accordance with figure 6. Glass roof
panels 24 in the lower region contain solar cells 60
that abut one another on all sides, and the sunlight S1
is completely absorbed thereby. The uppermost two glass
roof panels 24 contain no solar cells 60, and the
sunlight S2 can pass through completely and is
completely absorbed by a black absorber layer 64
applied to the subroof 12, and this leads to intense
heating of the air 20 flowing through. The absorber
layer 64 is applied only in the region of the
completely transparent glass roof panels 24.
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In the embodiment in accordance with figure 8, the
solar cells 60 are applied with an all-round spacing b
corresponding to the variant V of figure 7.
Respectively approximately half the sunlight strikes
the solar cells (S1), or the other half of the sunlight
passes through the glass roof panels 24 and strikes the
selective absorber layer 64 (S2), which covers the
entire subroof 12. By comparison with figure 7, the
photovoltaic generation of electric current is reduced
while the heating of the airflow 20 is increased, by
contrast.
Evidently, in accordance with figure 8, and to a lesser
extent in accordance with figure 7, the flat gap 18 is
increased in the flow direction 16, and this even
further improves the effect of the two completely
transparent glass roof panels 24.
Figure 9 indicates the preferred laying variant of
square glass roof panels 24. The glass roof panels 24
are set on end, the diagonals running in the fall line
of the roof. The glass roof panels 24 are arranged in a
fashion doubly overlapping downward, and they are held
by standard-type supports 26.
According to figure 10, the glass roof panels 24 are
laid conventionally, that is to say in the form of a
shingle roof overlapping downward on one side. Sealing
and collecting channels 66 are laid on both sides and
run in a vertical direction, that is to say in the flow
direction 16 of the air guided through. Below the glass
roof panels 24, the sealing and collecting tracks 66
both provide support and keep the spacing, and have
longitudinal openings (not depicted) for the passage of
the air and the cabling. However, it is not these
openings that are important, but the fact that the
tracks 66 run in the direction of the airflow 16 and
are therefore virtually no obstruction.
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In accordance with figure 11, square or rectangular
glass roof panels 24 are held like a window in frames
68 which both provide a seal and support at a spacing a
(figure 1).
A variant in accordance with figure 10 is illustrated
in figure 12. The glass roof panels 24 taper rearward,
and this is required in particular for a pitched roof.
Embodiments in accordance with figures 13 to 15 show a
laminate structure of the glass roof panels 24. Common
to all the embodiments is a panel 70 made from hardened
glass. It is generally possible to walk on this. An
antireflection layer 72 that prevents undesired mirror
effects is optional. Visible on the other side of the
plate 70 made from hardened glass is a cell embedding
74 made from ethyl vinyl acetate EVA for the solar
cells 60 of flat design. As in figure 13, these solar
cells 60 are arranged in an abutting fashion, and they
pass no sunlight. The EVA layer 74 is protected by a
rear wall sheet 76, for example made from a Tedlar
sheet or an aluminum sheet.
Arranged on the rear wall sheet 76 is a flat box 78 for
cable outlets and a bridging diode 60. The current
conduction takes place in a way known per se, although
it is ensured that the cable 82 is flat and therefore
poses little obstruction to the airflow.
The laminate structure of the glass roof panel 24 in
accordance with figure 14 corresponds substantially to
that of figure 13. The flat solar cells 60 are,
however, embedded in a transparent EVA layer 74 at a
spacing b from one another, the width b of the
transparent strips 90 being greater than the
corresponding linear dimension of the solar cells 60.
The rear sheet or panel 76 must likewise be of
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transparent design. A translucent glass roof panel 24
in accordance with figure 14 has transparent and opaque
regions by definition.
Figure 15 shows a further variant of a laminar glass
roof panel 24 in accordance with which the solar cells
60 are deposited directly onto the underside of the
panel 70 made from hardened glass at a spacing b from
one another (thin-layer cell technology). Also in
accordance with figure 15, what is involved is a
translucent glass roof panel 24, but with a smaller
area fraction of the transparent strips 90 than in
figure 14. Depending on the process, the thin layer
that is applied to glass or transparent plastics lies
between two glass or plastic panels.
Figure 16 shows in plan view a glass roof panel 24
corresponding to figure 13. Solar cells 60, which are
of substantially square design, are laid in a fashion
abutting one another and leave no gap open for the
sunlight S2 to slip through (figure 8). The edge zones
84 serve for the formation of overlaps. The laid glass
roof panels 24 form a roof structure 10 that is opaque
to the sun's rays raised (figure 6, variant R).
Figure 17 shows a translucent glass roof panel 24 with
solar cells 60 arranged at a spacing b in accordance
with figure 15. The laid glass roof panels 24 also have
substantial transparent strips 90.
Figure 18 shows a roof structure 10 for a solar system
for the photovoltaic generation of electric current and
for strong heating of air in the flow direction 16. Use
is made in principle of the laying pattern S of figure
6, but with glass roof panels 24, standing on end, of
square shape with diagonals in the direction of fall.
In the lower region, glass roof panels 24 are arranged
with square solar cells 60, in an abutting arrangement,
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in an overlapping fashion on two sides and sealed. Also
inserted in this region is a transparent or (not
illustrated) translucent glass roof panel 24 that takes
over the function of a roof window 88, and this is
sensible chiefly when the roof consists only of opaque
glass roof panels 24.
Purely thermal glass roof panels 24 without solar cells
are arranged in the uppermost, so called "booster
region". Here, the already preheated air is heated to a
temperature of about 100 C. The air passes directly
into a heat exchanger 40 with a water circuit 42 for
the production of hot water. As already indicated in
figure 4, this heat exchanger 40 is arranged in the
gable region.
Arranged in the lowermost roof region are so called
"dummies" 90, black coated glass roof panels 24 without
a photovoltaic effect, in the case of which "solar
cells" are printed on by screen printing.
