DE19726330A1 - Vacuum panel for thermal utilisation of solar energy - Google Patents

Abstract

The vacuum panel for thermal utilisation of solar energy includes at least one cover pane (2) and a flexible metal foil (7) forming a trough, with aerogel (1) located between the cover pane and the trough. The panel contains elements (3, 46) of arbitrary colouring and good heat conduction for absorption and/or reflection of radiation energy, and/or elements (4, 6) with a liquid heat carrier, and/or elements (46, 51) for shading, and/or pressure resistant elements (5) for heat insulation.

Description

The invention relates to devices according to the preamble of claim 1 and methods for Manufacture of such devices.

The devices are preferred as facade panels for the thermal use of solar energy used. Transparent thermal insulation, as described in DE 43 17 858 or EP 075 165 A2, use the storage mass of a mostly south-facing, massive wall by Solar energy reaches the wall through the TWD material and the absorbed heat time-shifted to the room behind the wall. So especially in summer Overheating takes place, the systems are back-ventilated, shaded or heated by a fluid.

The heart of the facade panels is the TWD material. In addition to air or gas Capillary material made of glass or plastic or airgel is used. In terms of avoidance pressure-resistant airgel in the form of granules, plates, flakes or flexible mats considered. Also can cut remnants z. B. from the manufacture of such materials. The materials can also be used as composite materials e.g. B. strengthened with fibers. Because of their transparency and Particularly low thermal conductivity, aerogels are particularly suitable. This affects e.g. B. granular Aerogels in the form of small spheres (EP 0171722), monolithic aerogels (WO 9203378, EP 0653377 and US 4,610,863) and other forms (DE 44 30 669.5 and DE 44 30 642.3) such as structurally reinforced Mats, plates etc.

Aerogels can be used particularly effectively in vacuum insulation panels. Their low thermal conductivities of approx. 0.02 W / mK for monolithic aerogels at normal pressure are reduced to approx. 0.008 W / mK at 100 mbar ambient pressure. For granular aerogels with air gaps between the individual airgel spheres, it is necessary to evacuate from approx. 0.013 W / m ² K to approx. 10 mbar to achieve thermal conductivities. Due to the low thermal conductivities that can be achieved, particularly compact panels can be produced, which have thicknesses of 0.5 to 10 cm, preferably 1 to 5 cm. The purpose of using vacuum or vacuum panels is furthermore to protect the sensitive insulating materials and to form a stable body through sandwich construction.

In the present application, a distinction is made between vacuum modules and vacuum modules. Vacuum modules, as described in DE 43 17 858 A1, require an absolute filling pressure Ambient temperature around 800 mbar. Vacuum panels are characterized by the fact that they have the effect of Use so-called super insulation or super thermal insulation and at pressures between 10E-3 and 750 mbar, preferably between 10 and 200 mbar, clearly shows the thermal conductivity of the TWD material is reduced.

Such vacuum and vacuum panels (panel = module) can be used with airgel between two transparent panes. You will e.g. B. described in EP A 0 468 124. The The use of airgel mats and plates is described in DE 195 07 732. The use of the Aerogels is limited to the use of glass panes. DE 195 07 732 describes the Typical vacuum pressures required when using fiber-reinforced aerogels.  

Another possibility to manufacture vacuum or vacuum panels in the above sense is that Enclosing TWD material between a transparent pane and a metal tray.

DE 43 17 858 describes a closed module with an airtight edge bond. Doing so with regard to pressure forces which act on the cover plate by evacuation, the negative pressure in the module only reduced to about 800 mbar to the extent that the thermal expansion of the air at Heating the module base just does not have any overpressure relative to the environment in the module. The negative pressure on the cover should be absorbed by the module housing. DE 43 17 858 makes no proposals for such a housing. Functional disadvantage of the devices are additional housing components that only allow the convective removal of the excess heat.

A description of a vacuum or partial vacuum collector can be found in DE 43 22 169 A1, here is also called the use of solids as thermal insulation. To implode the cover plate Vacuum applications will be prevented even in the presence of solids Thermal insulation, additional support profiles provided.

The cover disk can also be imploded if non-dimensionally stable TWD material is used avoid using less than 100 µm thick by using thin stainless steel foils. By means of this Manufacture vacuum panels using the TWD materials described above, with the thin films absorb the reaction forces to the negative pressure.

Vacuum panels, produced by means of such foils, are built into a test facade Capatect Dämmsysteme GmbH & Co. Energietechnik KG in Ober-Ramstadt. The panels will be to avoid excess temperatures in the device described in DE 43 17 858 by the Back vented convectively. This limits the use of such vacuum panels and means high additional costs for the device for ventilation, especially if it is effective against overheating should be regulated.

EP 0 750 165 A2 proposes a solution to the problem of overheating. It describes a layer by layer built-up thermal insulation composite system for well and poorly insulated walls with heat dissipation by means of Fluid system. In the system with coupling of transparent thermal insulation and heat dissipation the problem of summer overheating by means of heat transfer flow remains if no heat is generated the heat transfer stream is removed or the temperature of the fluid is too high. With the system the individual functional elements are created on site similar to a composite thermal insulation system and coupled to one. EP 0 750 165 A2 shows a way to avoid high additional costs for external components of overheating protection and the use of excess heat by the Integration of functional components in a TWD thermal insulation composite system.

To make TWD systems particularly competitive in the field of facade design and renovation must make the overheating problem, ideally by using the Excess heat to be solved. It is also an inexpensive production with high quality Appearance necessary.

The invention has for its object to devices according to the preamble of claim 1 create which under the aspects of high energy input for heating, cooling and warm water preparation, the safe avoidance of excess temperatures on the house wall and more effectively Shading are marked. This affects one or more of the aspects mentioned. Furthermore, there is the task of methods for producing such devices under the aspects of continuous industrial production and permanent vacuum or vacuum resistance create.

According to the invention, this object is achieved by the claims 1 to 15 mentioned, with the following advantages:
The advantage of the device according to claim 1 is the creation of compact sandwich elements that meet the requirements for attractive facade design, especially through the use of aerogels. High additional costs for creating functioning systems are avoided by integrating components ( 3 ), ( 4 ), ( 5 ), ( 6 ), ( 46 ), ( 51 ) of the overheating protection and the use of excess heat in the vacuum panels according to the generic term.

The panels can be manufactured in a particularly simple manner in that aerogels ( 1 ) and components can be introduced into the metal trough without special processing and accuracy requirements and reaction forces to the negative pressure, which would otherwise destroy the cover plate, are absorbed by the deforming metal foil. Another advantage is the possibility to produce particularly thin panels by using the super thermal insulation as well as the possibility of any color design.

Advantage of the device according to claim 2 is the avoidance of manufacturing steps by simply making a thermal contact between z. B. a pipe coil ( 4 ) and the module floor ( 7 ) and the possibility to dissipate summer excess heat by a fluid in the pipe coils ( 4 ), so that the solar yields increase and avoid excess temperatures on house walls.

The advantage of the device according to claim 3 is the improvement of the heat transfer between the absorber sheet ( 3 ) and the fluid, which results in a particularly effective switchability between the heating situation without fluid flow and collector use with fluid flow. Excessive temperatures on the back of the panel can also be reduced, in particular by inserting thermal insulation strips.

The advantage of a device according to claim 4 is the formation of a panel for collector applications on the facade and roof, whereby collectors with a particularly thin construction are possible.

Advantage of a device according to claim 5 is the effective use of solar energy for heating and Water heating, in that the elements in winter as desired as transparent heat Insulation are used and in the summer and the transition period the excess heat to solar Hot water heating, solar cooling or delayed heating can be used. Further advantages are the safe switching between collector and heating use, the avoidance of Elements of shading, the avoidance of overheating, the optimized use of energy and the possibility of inexpensive production through simple construction.

An advantage of an application according to claim 6 when switching according to FIG. 9 and low temperatures of the heat sink is the possibility of using the collector and cooling the wall of the building. Through pure TWD applications e.g. B. with shading can save about 100 kWh / m ² a heating energy based on the wall area compared to opaque insulation at the Cologne location. If the system is also used as a facade collector, an additional 250 kWh / m ² a of energy for hot water supply can be saved in the transition period and in summer, when conventional solar wall systems are shaded to prevent overheating. Exact values are determined object-specifically with a dynamic simulation program with the help of an electrical analogy model.

Advantages of an application according to claim 7 are the control of high fluid temperatures by switching according to FIG. 10 without overheating the building wall.

Advantages of an application according to claim 8, the possibility of solar heating by means of a safe circuit according to FIG. 11.

Advantages of a device according to claim 9 are the possibility of avoiding excess temperatures of the absorber sheet ( 7 ) and thus of the house wall ( 9 ) at high sun positions in summer by reflection of the solar radiation on slats ( 46 ) with high reflectivity on the front. When the sun is low, the rays reach the panel floor through the relatively low-scattering TWD material and heat it and the wall.

An advantage of a device according to claim 10 is, in addition to avoiding excess temperatures on the absorber trough, as in claim 9, the possibility of additional heat dissipation to a sink. It comes as a transparent thermal insulation material ( 1 ) z. B. granular airgel or residual material such as cut residues of mats or sheets into consideration.

An advantage of a device according to claim 11 is the possibility of using various airgel materials, composite materials and cut residues made of airgel, wherein monolithic aerogels ( 1 ''), especially in connection with lamellae ( 46 ) and z. B. granules ( 1 ') can be used to fill empty spaces in the metal tub ( 7 ).

Advantages of a device according to claim 12 result from the protection of the glass-metal joining Conducting pipes and valves, simplifying assembly, portability, Integration in facade systems, the avoidance of heat loss through the frame and the Use as a collector frame.

Advantages of a device according to claim 13 result from the possibility of the desired Shading, the integration in electrically controlled facade systems when using an electrical Switching and the creation of particularly thin modules with effective shading.

Advantage of the method according to claim 14 is the possibility of the time-consuming joining process z. B. one Outsource the metal-glass connection from the continuous production and at a separate location higher temperatures, lower ambient pressure and special purity.

The advantage of the method according to claim 15 is the possibility of using in particular Welding process to form vacuum-tight panels also in the area of the glass-metal connection, which leak rates are less than 2E-8 mbar 1 / s based on a panel volume of approx. 20 liters.

Embodiments

The drawings show exemplary embodiments:

Fig. 1a shows a section through a facade panel which z. B. is evacuated to a vacuum of absolutely 100 mbar. The radiation power of the sun is approx. 60-85% after passing through the front cover plate ( 2 ) and the airgel ( 1 ), in the manifestations ( 1 '), ( 1 ''), ( 1 ''') colored sheet ( 3 ) absorbed and discharged through a fluid ( 11 ) by means of a pipe system ( 4 ) on the front. Unwanted heat transfer to the back of the panel is prevented by a pressure-resistant thermal insulation material ( 5 ), which can be transparent but also opaque. The heat output absorbed by the fluid ( 11 ) can, as desired, be supplied to a heat sink ( 18 ), such as particularly layered solar storage systems, or via coupling to the fluid ( 10 ) at the rear of the panels for heating the wall ( 9 ). FIG. 1b shows a trough (7) with blades (46) and monolithic (1 '') and flaked (1 ''') airgel. Fig. 1c shows a tub with fiber-reinforced airgel ( 1 ''') and a switchable shade ( 51 ).

FIG. 2 shows a simplified electrical equivalent circuit diagram for the case of an arrangement of the elements according to claim 1 described in FIG. 1 or FIG. 6. Here the heat transfer mechanisms are illustrated and the switch between wall heating and collector operation is indicated by switch S1. The heat flows analogously to the electrical current from nodes with a high temperature to those with a low temperature. From a balancing of the heat flows for each node, dynamic calculations result in the heat flows q_ infinite as a leakage current to the surroundings, q_fl as the heat flow supplied to the fluid and q_i as the heat flow emitted to the room.

The airgel is characterized in particular by its transmission and the total energy transmittance g and the thermal resistance [1]. [3,4] is, for example, the thermal resistance (m ² K / W) from the absorber sheet ( 3 ) to a copper pipe coil ( 4 ). [W_i] denote the thermal resistance of the building wall, the storage capacity of the wall is [C_i]. A precise dimensioning of the functional elements takes place depending on the TWD material and applications by means of simulation calculations based on analogy models as shown in FIG. 2.

Fig. 3 shows a section through a device according to claim 2 in the z. B. a pipe coil ( 4 ), made of Cu with a few mm diameter, is directly on the arbitrarily colored module base ( 7 ). By using TWD composite materials ( 1 ''') and dimensionally stable panels or mats, an intermediate layer between the TWD material and pipe coil ( 4 ) can be dispensed with. The distance between the turns is a few cm. The radiative heat transfer [7-9] can be reduced by using polished sheets.

Fig. 4 shows an improvement in the heat transfer [7, 4] to fluid ( 11 ) by inserting an additional heat-conducting sheet of any color ( 3 ) [3, 4]. To reduce the heat transfer [4, 7] from the hot absorber tubes ( 4 ) to the rear of the panel ( 7 ), an opaque or transparent thermal insulation material ( 12 ) can be placed between the tub base ( 7 ) and the absorber ( 3 ). B. be inserted in strips. The TWD material ( 1 ) is shown in flake and granulate form.

Fig. 5 shows a device according to claim 1 as a facade collector, by inserting opaque or transparent thermal insulation material ( 5 ), for. B. from manufacturing remnants of airgel production, the heat output to the back of the panel [5] is greatly reduced. Fig. 5 shows a pipe coil ( 4 ), which is located in the direction of the sun in front of the absorber sheet, this makes sense when laminated thermal insulation materials ( 5 ) are inserted. Otherwise, the pipe coil ( 4 ) is preferably placed between the absorber ( 3 ) and thermal insulation ( 5 ).

Fig. 6 shows a facade collector according to claim 4, in which between the rear panel ( 7 ) and thermal insulation ( 5 ) a rear pipe system ( 6 ) is attached. Through this pipe system, heat, which is directly or indirectly coupled with the front pipe system ( 4 ) via a fluid, is transported to the rear of the panel ( 7 ) and is used there for room heating according to FIG. 11, or for cooling the wall according to FIG. 9 .

Fig. 9 shows a hydraulic scheme according to which one or more panels can be interconnected. In a circuit according to FIG. 9, a heat transfer fluid is pumped through the pipes ( 6 ) and ( 4 ) by means of the pump ( 41 ). The four-way valve ( 17 ) is preferably outside the panels and is, for. B. Part of a solar hot water and heating device. By using an on device according to claim 6 in a circuit according to FIG. 9, the fluid from a heat sink, such as. B. a stratified or seasonal storage ( 18 ) as cool as possible, z. B. at 20 ° C, first along the house wall ( 9 ) and warms up, for example, to 23 ° C. The fluid on the front then heats up to 70 ° C, for example, through the solar radiation absorbed.

Fig. 10 shows a circuit to avoid overheating of the wall ( 9 ) at high fluid temperatures of the heat sink. By using a device according to claim 7 in a circuit according to FIG. 10, the fluid removed from the heat sink ( 18 ) is fed through the connecting line ( 22 ) directly to the pipe coil ( 4 ) on the front side of the panel and thus does not heat the house wall. This happens at high fluid temperatures of the sink, e.g. B. with loaded memory.

Fig. 11 shows a circuit for heating the building wall.

Fig. 12 shows a frame ( 23 ) for enclosing a panel. It consists of an elastic all-round material ( 19 ) as well as a fixed enclosure ( 20 ). The frame comprises the module frame made of pane ( 2 ), joining material and sheet metal ( 7 ) and has a recess on the outside ( 28 ). It has passages for the pipe systems ( 4 ), ( 6 ), ( 22 ).

Fig. 13 shows a panel with integrated slats ( 46 ) for shading. The slats cause shading of the panel base ( 7 ) at high sun positions by reflecting the sun's rays on their surface. When the sun is low, a large part of the sun's radiation reaches the panel floor. The inserted airgel material ( 1 ) consists, for example, of granules, monolith strips ( 1 '') and / or cut remnants of mats, materials which scatter light sunlight are preferred.

FIG. 14a shows the insertion of a disc (2) with all-round frame (48) on the edge of the panel. The frame with z. B. a difficult metal-glass connection can be prefabricated outside the production line of the panel. Fig. 14b shows the bonding of a metal frame (48) to the edge of the panel (27) z. B. by a welding process.

Fig. 15 shows an embodiment of a Fassadenpaneels, are integrated in the blades (46) in the panel and these slats are coupled to a fluid system (4).

Fig. 16 shows a module with a switchable layer ( 51 ) as shading, such switchable layers can be switched, for example, by temperature of the layer ( 51 ) or by applying an electrical voltage ( 52 ). Layers that can be switched by temperature change their light transmission from transparent to opaque at a switching temperature of the layer of, for example, 30 ° C.

Fig. 17 shows schematically the joining of a glass pane ( 2 ) with a circumferential metal frame ( 48 ) by a welding process, with intermediate foils ( 50 ) consisting of e.g. B. aluminum, which compensate for differences in the thermal expansion coefficient of the joining partners. The device ( 49 ) is used for local heating and, for example, 400 ° C.

Claims (15)

1. Vacuum panel for the thermal use of solar energy, comprising at least one cover plate ( 2 ) and a tub-forming flexible metal foil ( 7 ), airgel ( 1 ) being located between the cover disk and the tub, characterized in that highly heat-conducting, colored elements for Absorption and / or reflection of radiation energy ( 3 ), ( 46 ) and / or elements ( 4 ), ( 6 ) and / or elements for shading ( 46 ), ( 51 ) and / or pressure-resistant elements for thermal insulation that can flow through a liquid heat transfer medium ( 5 ), ( 12 ) are inserted. 2. Apparatus according to claim 1, characterized in that flowable from a liquid heat transfer elements ( 4 ) rest directly on the panel base ( 7 ), wherein the panel base with the overlying elements ( 4 ) can be colored as desired. 3. Apparatus according to claim 2, characterized in that between the, through which a liquid heat transfer medium can flow ( 4 ) and the TWD material ( 1 ) good heat-conducting, arbitrarily colored elements for absorbing solar radiation ( 3 ), ( 46 ) in the tub ( 7 ) are inserted and additional pressure-resistant elements for thermal insulation ( 12 ) can be inserted in the area of the elements ( 4 ) through which a liquid heat transfer medium can flow. 4. Apparatus according to claim 2 or 3, characterized in that there are opaque and / or transparent, pressure-resistant elements for thermal insulation ( 12 ) between the good heat-conducting, arbitrarily colored elements for absorption and / or reflection of solar radiation ( 3 ), ( 46 ) and / or elements ( 4 ) through which a liquid heat transfer medium can flow and the trough base ( 7 ) are located, the heat insulation material ( 5 ) being laminated with a heat-conducting film. 5. The device according to claim 4, characterized in that second, through which a liquid heat transfer fluid elements ( 6 ) between the thermal insulation ( 5 ) and the rear panel ( 7 ) are arranged, the elements ( 6 ), ( 5 ) and ( 4th ) can be prefabricated in a group. 6. Use of a device according to claim 5, characterized in that the elements ( 4 ), ( 6 ) which can be flowed through by a liquid heat transfer medium are preferably connected externally to a pump ( 41 ) and sink ( 18 ) and are connected in such a way that at low flow temperatures from the depression ( 18 ) and the lack of heat on the wall ( 9 ), the fluid is first passed along the wall of the house through the second elements ( 6 ) through which a liquid heat transfer medium flows, and then heat-absorbing the side facing the sun through those through which a liquid heat transfer medium flows Flows through elements ( 4 ). 7. Use of a device according to claim 5, characterized in that the elements ( 4 ), ( 6 ) which can be flowed through by a liquid heat transfer medium are preferably connected externally to a pump ( 41 ) and sink ( 18 ) and are connected in such a way that at high flow temperatures from the depression ( 18 ) the fluid flows directly through the connection ( 19 ) to the side facing the sun. 8. Use of a device according to claim 5, characterized in that the elements ( 4 ) and ( 6 ) which can be flowed through by a liquid heat transfer medium are preferably connected externally to a pump ( 41 ) and sink ( 18 ) and are connected in such a way that when there is no Decrease in heat through the sink and heat requirement on the wall ( 9 ) the heated fluid is guided from the first elements ( 4 ) through which a liquid heat transfer medium flows to the second elements ( 6 ) to the rear of the panel. 9. The device according to claim 1, characterized in that slats ( 46 ) are inserted with a selectable fixed angle alpha and the reflection of the slats for visible light is high. 10. The device according to claim 1, characterized in that fins ( 46 ) with, through which a liquid heat transfer medium, elements ( 4 ) for dissipating the absorbed radiation energy are connected and inserted, and that the absorption of the fins for visible light is high. 11. The device according to claim 1, characterized in that the aerogels ( 1 ) in the form of granules, beads or particles ( 1 ') and / or in the form of monolithic or homogeneous plates ( 1 '') and / or in the form of mats or plates ( 1 ''') and can also be modified by structural reinforcement or composite with other materials and can also consist of production waste of the aforementioned materials. 12. The device according to claim 1, wherein the connection point between the metal foil ( 7 ) and cover plate ( 2 ) is surrounded by a frame ( 23 ), characterized in that the frame consists of elastic ( 19 ) and dimensionally stable material ( 20 ), wherein the elastic material ( 19 ) firmly surrounds the connection point and the dimensionally stable material ( 20 ) comprises the elastic material, wherein the frame ( 20 ) can contain recesses on the side surfaces ( 28 ). 13. The apparatus according to claim 1, characterized in that a switchable layer ( 51 ) is arranged for shading the panel base ( 7 ) behind the disc ( 2 ). 14. A method for producing a device according to claim 1, characterized in that the joining of the cover plate ( 2 ) and an auxiliary frame ( 48 ) is outsourced from production and, after prefabrication, the plate ( 2 ) with the peripheral frame ( 48 ) with the Metal foil ( 7 ) is connected, the prefabrication can be carried out at elevated temperatures. 15. A method for producing a device according to claim 1 or 14, comprising a disc ( 2 ) made of soda-lime glass, wherein the joining between two or three of the joining partners disc ( 2 ), frame ( 48 ) and tub ( 7 ) by means of a welding or Soldering technology takes place, an intermediate film ( 50 ) can be inserted, characterized in that the trough ( 7 ) and / or the frame ( 48 ) made of the metallic materials X6 Cr Ti 17, X6 Cr Nb 17, Ni Fe 45, Ni 36 , X5 Cr17, number 1.4509 or number 2.4617.