Solar collector board and system of solar collector boards

Description of equivalent WO 2011089530 A2

Title:

Solar Collector Board and System of Solar Collector Boards Technical Field:

The present invention concerns a solar collector, in particular a specific solar collector board, and a system of several such solar collector boards. Background:

A solar collector is a device which converts energy in sun radiation into heat at a useable temperature. Energy conversion takes place in an absorber. The absorber is designed so that the radiation is absorbed and converted to thermal energy, and the energy is transmitted to a heating medium which transports the energy away from the absorber of the solar collector board to a heat storage or to immediate utilisation. The heating medium may be a gas such as air, or a fluid such as water. The solar collector board is normally insulated. At the absorber side facing towards the sun an insulation that is transparent to sunlight is often applied, for example, glass or transparent plastic, and at the side of the board facing away from the sun mineral wool or other solid, temperature resistant insulation is often applied. A plane solar collector has a cover plate and often an absorber that is plane, i.e. there is no focusing of the sunlight towards the absorber. Plane solar collectors that do not have cover plates in front of the absorber are also known. Solar collectors made of plastic may utilize pure water, resulting in a higher energy transmission than utilizing glycol-bearing water, for example 30 %. However, plastic materials have limited durability with respect to the exposure of sunlight and heat.

Further, the solar collectors may offer a challenge for aesthetic or constructional reasons. At present, solar collectors are not used as part of the building construction. Thus, the solar collector board represents an addition to the building.

The present invention aims to solve the above mentioned problems concerning known solar collector boards by providing solar collector boards that are able to utilize fluids such as water as a cooling medium without the risk of corrosion. Further, the solar collector board in accordance with the present invention is very resistant towards external influences such as sun, frost, humidity and temperature variations. Further, the present invention provides a solar collector board which may constitute part of a building construction and which may even appear as a design element in a facade, on a roof or the like. Further, the present invention provides a solar collector board utilizing recyclable materials that in addition requires small amount of energy during manufacture. Summary of the invention:

The above indicated problems are solved in accordance with the present invention by a solar collector board formed as a layered construction as stated in the introductory part of claim 1, and having the characterizing features stated in the charactering clause of the claim. Further advantageous embodiments of the invention are stated in the dependent claims 2-16.

In particular, the inventive solar collector board comprises at least a first and a second platelike body, which are congruent or substantially congruent, and arranged mutually parallel or substantially parallel with a distance between them, the first platelike body being, at its surface facing the second platelike body, provided with absorbing properties, and the second platelike body being transparent or opaque. A seal, for example made of adhesives such as structural adhesives, is arranged in between the first and the second platelike body at their respective side edges. The seal assures said distance and at the same time provides a fluid tight space between the first and the second platelike body. The space between the first and the second platelike body is adapted for circulation of a fluid. The layered construction is further provided with at least one inlet and at least one outlet for the circulating fluid.

To reduce the compressive load on said platelike bodies it would be advantageous to attach one or more materials on their surface(s) positioned between the first and the second platelike body. The one or more materials may for example be made of identical material as used in the sealing along the side edges of the plates, for example structural adhesives.

In another aspect the solar collector board in accordance with the present invention is characterized in that the layered construction further comprises at least a third platelike body which is congruent or substantially congruent with the rest of the layered construction, and which is arranged with a space adjacent and parallel or substantially parallel to the second platelike body.

In yet another aspect the layered construction in accordance with the present invention further comprises at least a platelike insulating body arranged adjacent and parallel or substantially parallel to the first platelike body. In yet another aspect of the present invention one or more points/areas are arranged in the space between the first platelike body and the second platelike body, said points/areas being attached to one or both of the first platelike body and the second platelike body. In yet another aspect of the present invention one or more channels in form of partition walls are arranged in the space between the first platelike body and the second platelike body, said channels being attached at their elongate sides to the first and the second platelike body, respectively. According to another aspect of the present invention a solar collector board in combination with any one of the above mentioned aspects is provided, where at least one inlet and/or the at least one outlet for the circulating fluid is arranged in the surface of the second platelike body.

According to yet another aspect of the present invention a solar collector board in

combination with any one of the above mentioned aspects is provided, where the inlet and/or the outlet for the fluid is arranged in the edge between the second platelike body and the first platelike body.

According to yet another aspect of the present invention provides a solar collector board in combination with anyone of the above mentioned aspects is provided, where the layered construction can have a curved surface.

According to yet another aspect of the present invention a solar collector board in

combination with anyone of the above mentioned aspects is provided, where the solar collector board can be adapted to the facade, roof or doors of building or installations, to constitute a part of the building construction in the same manner as glass.

According to yet another aspect of the present invention a solar collector board in

combination with anyone of the above mentioned aspects is provided, where the absorbing surface of the first platelike body is constituted by one or more paint coatings or inking. The paint coating/ inking can be of ceramic, metal oxide or powder coating type. The absorbing surface can also comprise silicone or other polymer-like material with low thermal conductivity. The latter feature is advantageous since the energy that is absorbed in the surface cannot escape the construction. The main part of the first platelike body can in a preferred embodiment be produced using a suitable glass, but can also be made of other material such as fibreglass or carbon fibre sealed with for example silicone. According to yet another aspect of the present invention a solar collector board in combination with anyone of the above mentioned aspects is provided, where the second platelike body is a low emission glass. Alternatively or in combination with low emission glass the second platelike body may be covered with a low emission layer.

According to yet another aspect of the present invention a solar collector board in

combination with one or more of the above mentioned aspects is provided, wherein the third platelike body is a low emission glass. According to yet another aspect of the present invention a solar collector board in

combination with one or more of the above aspects is provided, where the third platelike body is a glass with low absorbance within a specific spectral area, for example between 250 - 3000 nm, preferably between 380 - 2500 nm. According to yet another aspect of the present invention a solar collector board in

combination with anyone of the above mentioned aspects is provided, where the layered construction comprises further platelike bodies arranged in a layered structure and adjacent the third platelike body. According to yet another aspect of the present invention a solar collector board in

combination with anyone of the above mentioned aspects is provided, where at least one of the platelike bodies adjacent the first platelike body in the layered construction is made by one of: toughened glass, laminated glass or laminated toughened glass. Further the present invention provides a system comprising several solar collector boards according to one or many of the previous aspects mentioned above, where each solar collector boars is in fluid communication with one or several adjacent solar collector boards.

Further advantages with the present invention will be apparent from the dependent claims.

Figures

The present invention will be described by the appended figures in a manner to make it easier to understand,

Figure 1 illustrates a cross-section of a layered solar collector board construction,

Figure 2 illustrates an example of a solar collector board with several channels,

Figure 3 illustrates an example of a solar collector board with several partition walls between two plates comprised by the solar collector board, Figure 4 illustrates yet another example of a solar collector board with an angular partition wall in a different configuration from that of figure 3 between two plates comprised by the solar collector board,

Figure 5 illustrates yet another example of a solar collector board with several s-shaped partition walls in a different configuration from that of figure 3 between two plates comprised by the solar collector board, and

Figure 6 illustrates yet another example of a solar collector board with two partition walls in a different configuration from that of figure 2 between two plates comprised by the solar collector board.

Detailed description

The present invention will now be described in more detail with support of the appended figures.

If nothing else is said, the term glass in the following description is to be understood in its broadest sense. The important thing is that the useful properties of the glass are utilized in a solar collector board configuration according to the invention. A non exclusive list of materials that should be interpreted as glass comprises: soda-lime glass, borosilicate glass, acrylic glass, mica-glass (muscovite), aluminium oxitrin or other suitable solid materials including plastic materials.

There is a desire to provide a solar collector board or a solar collector configuration of a layered type comprising one or more volumes arranged for the circulation of a fluid. Such a layered construction would preferably be formed so that a maximal portion of the incoming radiation energy from the sun is absorbed by the circulating fluid. To achieve this, a layered construction that only comprises one volume for circulation of a fluid will typically have an outer surface that admits as much as possible of the incoming radiation energy from the sun, while the outer surface lets as little radiation energy as possible out again. The thermal conductivity of the outer surface can preferably be low, so that the heat loss to the

surroundings is as small as possible. Adjacent the inside of the outer surface the said volume holding the circulation fluid is arranged, and behind and adjacent this volume preferably a surface is arranged, which has the property of absorbing as much as possible of the incoming radiation energy. The surface behind should have a low thermal conductivity towards its back so that a heat loss towards layers/constructions behind it is avoided. The circulation fluid will then absorb heat from the absorbing surface. As an example the surface can be covered with a silicone or another polymer-like material having a low thermal conductivity. Recent developments regarding glass technology, as for example low emission materials and sun protection, have revolutionized the potential for the use of glass. Today big panels or formed glass surfaces can be manufactured, having a size of at least up to (4 x 2,5) m and tolerating the load limits for constructional elements. Glass, both transparent and coloured, are widely used as facade element. With today's technology toughened glass of low emission type can be provided, that is, glass that lets through more useful thermal energy relative to the injected power than what is the case with traditional glass and simultaneously lets out less thermal energy than traditional glass. Glass can be tailored both with respect to shape, colour, strength and emission features, and it can be laminated with films providing specifically desired features. In a layer formed configuration isolation glazing can be filled with noble gas, such as argon, between two or more hermetic glass surfaces. Glass is chemically stable and well proven in laboratory chemistry. Therefore, glass in its broadest sense is considered a good candidate for use as a solar collector board in that the glass in its broadest sense can be tailored in such a way that the properties described earlier can be achieved. The conductivity through the glass can for example be controlled by including conductive or non-conductive materials. The surface can be tailored by foils attached on the outside, or by foils integrated into the surface itself. As an example a layer of low emission material on the outwards facing surface of the second platelike body reflecting the main part of energy over a certain radiation range, as an example over 2500 nm, will be advantageous. It can also be preferable to apply a layer on the outwards facing surface of the third platelike body providing a low absorbance in a specific spectral range, for example, 380 - 2500 nm.

According to the present patent application a layer construction for solar collector boards is provided, which in its simplest form comprises at least one outer plate of glass exposed to the surroundings and one plate that is essentially parallel with this and that is placed on the inside of it, where the inside plate will have the features suitable for absorbing of radiation, i.e. thermally injected energy. Hence it will be possible for the absorbing surface to obtain considerably higher temperatures than the "surrounding temperature". The elevated temperature can be utilized by allowing a fluid to circulate between the two plates. The fluid will then absorb the heat from the absorbing surface, the absorber. Typically, the absorber and the outer glass surface can be congruent or substantially congruent so as to be adapted to be merged at their outer edges. In one aspect of the invention these surfaces are brought together so that they form a volume between them that is fluid tight. If this fluid tight volume is then equipped with one or several openings arranged for inlet and outlet of a fluid, the fluid can circulate through the container so that the fluid can absorb the heat from the absorber. This heat can then be used for example for the heating of buildings. The solar collector according the principle outlined above will obtain further favourable features if the outer plate, i.e. the second platelike body, is made from a material that will let a big part of the solar energy through to the core plate, i.e. the first platelike body. Such a material can be low emission glass that is transparent to sunlight in a specific spectrum, for example 380- 2500nm. Further, the outer glass plate can be made of a toughened glass type so that it can hold the loads defined for construction regulations and stand for being walked on. The outer glass plate can be completely transparent or coloured and it can be laminated and/or be equipped with an external film. So called structural glazing makes it possible to glue or in some other way attach the solar collector board to the underlying structure, thereby making it a bearing part of the construction.

In facades the solar collector board can be a bearing part of the construction, whereas in roofs it can replace roofing tiles or other roofing. In climates where snow is a problem the solar collector board according to the present invention will normally prevent snow from piling on the roof surface, with the benefits this has concerning the load on the roof structure and with respect to snow falling from the roof.

The absorber, i.e. the first platelike body, can be a glass plate with for example layer of paint, or a ceramic coating, a metal oxide or with powder coating in the surface or in the glass facing the volume. The surface can be given a colour suited to the desired design, and thereby contribute to making the solar collector of the present invention not only a solar collector but also a design element.

Because most types of glass are very stable and resistant to chemicals it will be possible to choose between several fluids to circulate inside the volume. For example, clean water, water containing glycol and many other fluids may be used. If a suitable joining is used it will be possible to obtain a good compressive strength, especially if toughened glass is used.

Experiments have shown that solar collector boards according to the present invention can reach a temperature of several hundred degrees. The compressive strength means that a system of solar collector plates according to the present invention can be pressurised up to 10 bar. As is known to a person skilled in the art it is possible to secure the pipe system connecting a solar collector board to the circulation fluid with one or several pressure valves. Further the solar collector board may be equipped with pressure valves. Such pressure valves can be adjusted to vent out overpressure at a certain pressure or at a specific temperature.

The joint between the outer glass plate and the absorber can be achieved according to the same principle as for insulation glass, where a profile is placed between two glass plates. The profile will usually be shaped to provide a room/slot for applying a butylene string between the profile and each of the plates. Finally, the profiles and butylene strings are joined using jointing paste. Other types of joints can be used; today several fasteners exist that are based on polymer compositions and that may be suitable, depending on desired features. The most important thing is that the plates are fluid tightly joined so that the fluid will not leak when cooling fluid circulates between the plates. It is also beneficial to apply adhesive material such as structural glue on the plates between the outer glass surface and the absorber surface so that pressure stress applied to the plates is reduced. Typically maximal pressure stress in the space between the plates at circulation of the cooling medium is for example 0.5-1 bar. From the above it is clear that a solar collector board according to the present invention will be able to combine several good properties, both as an energy-yielding element, as a construction element, as a design element, and as a suitable choice with respect to the environment. A solar collector board according to the present invention can work as a closed, pressurised system or as an open, non-pressurised system. Further the described layer construction can be extended with a desired number of glass plates. Such an increase in the number of glass plates can provide better properties for a solar collector in such a way that the thermal energy that is emitted is additionally reduced compared to a solar collector comprising only an outer glass plate. The layer construction indicated above in relation to the present invention can be produced according to customer specifications or follow standards for the construction branch so that a solar collector board according to the present invention can have standard width and length and appear as complete building elements with piping connections integrated for fluid circulation. The direction of a fluid inside a solar collector board, that is, inside the volume, can be affected by incorporating channels into the volume. Examples of such channels can be seen in Figs. 2-5.

Two or more solar collector boards can be linked so that they together form a system of solar collector boards. Typically inlets 4 to the solar collector boards will then be connected to a pipe path with incoming fluids, while outlet or exits 3 will be connected to a pipe path so that the solar collector boards are connected in parallel. These pipe paths can be located between two columns of several solar collector boards, they can be placed between two rows of several collector boards, or they can be located at the back of the solar collector boards so that an orthogonal system of several solar collector board arranged side by side is possible. The requirements on the pipe construction will be dependent on the fluid and the pressure to be handled. In the above the present invention has been described in general. To facilitate the understanding, embodiments with solar collector boards will be shown. The examples are only intended for illustration and other embodiments concerning partition walls 2 inside the volume arranged for fluid may be considered. The first embodiment example shows a layered solar collector board. It should be understood, as indicated in the above, that the number of layers of glass can be higher than indicated in figure 1. Further, several layers of fluid may be considered. Hence, in addition to the volume shown in figure 1 there may be several layers as is known from radiators having several cores/layers, for example, used in the car industry. It would also be possible to make the plates defining a volume for circulation of a fluid from glass in its broadest sense in combination with an absorber, glass in its broadest sense in combination with absorbing glass, or two absorbing plates in another suitable material.

A first embodiment of a solar collector board according to the present invention. The present invention will now be described in more detail with reference to figure 1. Figure 1 shows a cross section of a layered solar collector board in accordance with an aspect of the present invention. Solar collector boards according to this embodiment are shaped with a rear cover plate 9, this rear cover plate 9 will bear against a installation foundation. Cover plate 9 can be made from a range of materials, preferably it will be congruent or partly congruent with the remaining layered construction so that together with the remaining layer it will constitute a layered solar collector board as a separate element. The layer outside the cover plate according to the figure is an isolation layer 8. The isolation layer's function is to reduce the heat transmission to layers or construction behind the layer. Adjacent to the isolation layer 8 lies absorbing layer 7. The function of the absorbing layer 7 or the absorber 7 is to absorb incoming thermal energy in the form of radiation and then emit as much as possible of this energy to the circulating fluid, as indicated in the above. The adjacent element is shown in figure 1 as a glass plate 6. Between the glass plate 6 and the absorber 7 a volume for circulation of a fluid is defined. The fluid's function is to transport thermal energy supplied from the absorber to heat for example buildings. Glass plate 6 can be made from a number of glass types, depending on the desired features and on the external adjacent layer 5. The adjacent layer 5 can be an outer cover plate using underlying plates/layers. Layer 5 can also in itself have particularly favourable properties, for example produced from one or more hardened low-emission materials. Between layer 5 and layer 6 a volume having a noble gas or air may be defined. Layer 5 can also lie adjacent to layer 6 within.

Typical parameters for a configuration according to embodiment 1 can be:

Core layer, absorber 7:

- absorption in the spectral range 250-2500 nm > 50% - thermal conductivity < = 1,0 W/mK

- reflection in the spectral range 250-2500 ran < 15 %

Layer 6 adjacent the absorber:

- transition in the spectral range 250-2500 nm > 60 %

- reflection in the spectral range 250-2500 nm < 15 %

emissivity E <= 0,3

Alternative, if layer 6 is to be absorbing:

- absorption in the spectral range 250-2500 nm > 50 %

- reflection in the spectral range 250-2500 nm < 15 %

- emissivity E<=0,3

thermal conductivity >= 0,2 W/mK

The first embodiment according to the invention can be combined with any one of the following embodiment examples.

A second embodiment of an solar collector board according to the present invention.

The present invention will now be described with reference to figure 2. Figure 2 illustrates a square outline of a solar collector board. It should be understood that the shape of the solar collector board in this example is not limited to a square body.

From the figure it can be seen that the solar collector board is provided with a glue joint 1 around the edge of the solar collector board. This glue joint 1 holds two or more plates together, where at least one plate is glass in the broadest sense of the word or another absorbing material, while glue joint 1 can be any suitable fastener including fasteners used for traditional multiphase glass. The plates are parallel and congruent. The solar collector plate is illustrated having an inlet 4 for a circulating fluid in a corner, and having an outlet 3 for the circulating fluid in a diagonally opposite corner. The configuration of inlets 4 and outlets 3 is however neither limited to diagonally opposite corners, nor limited to one inlet and one outlet. The inlet 4 and outlet 3 can be placed on the front or the rear according to figure 2, but as stated above inlets 4 and or outlets may also be placed in the glue joint 1 itself. Any perceivable combination of in- and outflow configuration, i.e. openings on the front and/or rear and/or joint and a number inlets or outlets exceeding 2 can be possible. From Figure 2 it can be seen that glue joints 2 are provided that will lie inside the volume between an outer and an inner surface/plate. These glue joints 2 are in this embodiment assumed to be a number of random points/areas distributed within the volume with the primary purpose to reduce the compressive load that arises against the surfaces (glass) at the start of the circulating cooling medium and/or from outer compressive loads and/or the load of the circulating fluid's pressure. The joint (silicone) can also be placed in definite one- or two- dimensional patterns between the surfaces, to increase the circulation of the cooling medium and thereby to increase the capacity to receive sun energy transferred from the absorbing surfaces (see further embodiments under).

The points/areas 2 do not need to be glue joints but can be made of other suitable materials. Such points/areas 2 might affect the fluid stream through the volume from inlet to outlet. In addition points/areas 2 can give especially good properties for thermal conductivity, they can be homogeneous or made from more than one material. For example a point/area 2 may be glued to the absorber with thermally conductive glue, while being glued against the outwards surface with a glue having a low thermal conductivity. Further, the actual point/area 2 may be a thermally conductive material so that the circulating fluid obtains an increased surface for heat transfer, as is known from radiators/condensers. The term glue should be understood to include other fastener, and points/areas 2 do not need to define a solid wall between the two surfaces limiting the volume. The points/areas 2 can for example be attached to the absorber, but having a height allowing them not to have direct contact with the opposing outer surface.

As indicated above the points/areas 2 can function as strengthening elements so that a solar collector board with points/areas 2 will tolerate increased pressure loads both from the outside and from a pressurized fluid. Especially for big solar collector boards the strengthening features will be of interest.

A third embodiment of an solar collector board according to the present invention.

The present invention will now be described with reference to figure 3. Figure 3 illustrates a square outline of a solar collector board. It should be understood that the shape of the solar collector board in this example is not limited to a square body. The same construction features shown in figure 2 regarding the configuration for fluid inlets 4 and fluid outlets 3 are also relevant for the embodiment shown in figure 4.

Glue joint 1 holding two or more plates can comprise the same features shown for the example from figure 2.

From Figure 3 it can be seen that glue joints 2 are inserted that will lie inside the volume between an outer and an inner surface/plate. In contrast to the points/areas shown in figure 2 the glue joints 2 in this embodiment are assumed to be a number of parallel partition walls in the volume that will lead the cooling medium in preferred channels. The partition walls 2 or joints 2 can have the same features and functions mentioned in connection with the example associated with figure 2 above. A fourth embodiment of an solar collector board according to the present invention.

The present invention will now be described with reference to figure 4. Figure 4 illustrates a square outline of a solar collector board. It should be understood that the shape of the solar collector board in this example is not limited to a square body.

The same construction features shown in figure 2 regarding the configuration for fluid inlets 4 and fluid outlets 3 are also relevant for the embodiment shown in figure 4.

Glue joint 1 holding two or more plates can comprise the same features as shown for the example of Figure 2.

From figure 4 it can be seen that glue joints 2 are inserted that will lie inside the volume between an outer and an inner surface/plate. These glue joints 2 are in this embodiment thought to be a number of partition walls 2 in the volume which are arranged according to a fishbone design. The partition walls 2 or joints 2 can have the same features and functions shown in the example associated with figure 2 above.

A fifth embodiment of an solar collector board according to the present invention. The present invention will now be described with reference to figure 5. Figure 5 illustrates a square outline of a solar collector board. It should be understood that the shape of the solar collector board in this example is not limited to a square body.

The same construction features shown in figure 2 regarding the configuration for fluid inlets 4 and fluid outlets 3 are also relevant for the embodiment shown in Figure 5.

Glue joint 1 holding two or more plates can comprise the same features as shown for the example of figure 2. From figure 4 it can be seen that one glue joint 2 is inserted that will lie inside the volume between an outer and an inner surface/plate. This glue joint 2 is in this embodiment thought to be a partition wall 2 in the volume which is arranged according to a diagonal between two opposite corners. The partition walls 2 or joints 2 can have the same features and functions shown in the example associated with figure 2 above.

A sixth embodiment of an solar collector board according to the present invention.

The present invention will now be described with reference to figure 6. Figure 6 illustrates a square outline of a solar collector board. It should be understood that the shape of the solar collector board in this example is not limited to a square body. The same construction features shown in figure 2 regarding the configuration for fluid inlets 4 and fluid outlets 3 are also relevant for the embodiment shown in Figure 6.

Glue joint 1 holding two or more plates can comprise the same features as shown for the example of figure 2.

From figure 6 it can be seen that several glue joints are inserted that will lie inside the volume between an outer and an inner surface/plate. These glue joints is in this embodiment thought to be a number of partition walls 2 in the volume which are arranged according to a s-formed design. However the s-formed partition walls may be formed so they describes several periods of a sine curve. The partition walls 2 or joints 2 can have the same features and functions shown in the example associated with figure 2 above.

A seventh embodiment of an solar collector board according to the present invention. The present invention will now be described with reference to figure 7. Figure 7 illustrates a square outline of a solar collector board. It should be understood that the shape of the solar collector board in this example is not limited to a square body.

The same constructive features shown in figure 2 regarding the configuration for fluid inlets 4 and fluid outlets 3 are also relevant for the embodiment shown in Figure 7.

Glue joint 1 holding two or more plates can comprise the same features as shown for the example of figure 2. From figure 7 it can be seen that two glue joints are inserted that will lie inside the volume between an outer and an inner surface/plate. These glue joints are in this embodiment assumed to be two or more partition walls 2 where the first partition wall stretches orthogonally from one side edge, while the next partition wall stretches orthogonal from the opposite side edge. The partition walls 2 or joints 2 can have the same features and functions shown in the example associated with figure 2 above.

Figure references

1) Glue joint or other joint around the edge of the glass (in the utmost layer is this joint open in the bottom)

2) Glue joint or other dedicated joint materials or materials for partition walls between the glass where the cooling liquid circulates

3) Outlet for the circulating cooling liquid

4) Inlet for the circulating cooling liquid

5) Outer cover plate of glass or plastic

6) Outer layer of absorbing element with glasslike qualities

7) Inner layer of absorbing element

8) Isolation material

9) Rear cover plate