FR2507755A1 - Solar energy trap - comprises multichannel profile beneath absorbent coating to receive and contain thermal energy - Google Patents

Abstract

A solar energy trap for use on roofs or walls comprises an extruded multichannel core panel coated with a mixt. having good radiant energy capture and retention characteristics. The coating is based on aq. emulsions of vinyl acetate polymers or copolymers with maleic esters, or copolymers of styrene and acrylic esters, filled with micro-granular mineral materials . Suitable for temperate or hot climates, depending on modification of the coating composition to suit the different radiant characteristics of the available lighting, ie. for temperate climates, the filler/resin combination may be designed to receive 0.7-3micron radiation and give low dissipation of trapped heat via emission at 5-30microns. The coating can be coloured by incorporating metal oxides, and can be shared to simulate various patterns of plain or polished tiling, bricks, slates, stones, roughcast, etc.

Description

Many heating and air conditioning systems derived from energy are known; solar thermal, most of these systems belonging to the following Techals
- Greenhouse effect with passive system. System known for a long time and having an acceptable yield but receiving many objections on the ecological and medical plans.

 - Optical plane sensor with ~ òcalisation. This system is too time-limited and can only be used for additional thermal air conditioning.

 - Concentrator sensor. This system makes it possible to work with very high temperatures but, unfortunately, is not aesthetic and imposes a very complex technology of solar tracking incompatible with the habitat. It can only be reserved for industrial uses or advanced techniques.

 - Matt black plane sensor. This system, used without greenhouse effect, imposes too large surfaces which, in general, cannot be coupled with the habitat. It is particularly reserved for the heating of swimming pools, horticultural greenhouses, or for certain very specialized industries.

 Here, the system which will be described is new and, as we will see, it can serve as a heating system for the home, for producing domestic hot water and for general air conditioning applicable both in winter and in summer .

 This process allows the thermal capture of solar radiation by a structure appearing either in the form of a roof covering, or in the form of a vertical wall covering, these two versions falling under the obligations of integration into the regional site. These two versions, which can be combined or independent, are, for the first, in the form of panels acting as a roof with a perfect imitation of tiles of any shape, or slate, or any other shape determined according to the geographic location of the installation. This thermal energy sensor roof can, depending on the geographic locations of the habitat it covers, be the source of heat, sanitary water, heating and air conditioning. The second version is in the form of a panel positioned against a vertical wall or on a very steep wall according to the current new architectural structures and this one is particularly adapted to the winter solar thermal capture, when the height of the sun is low, and presents the same heating functions as the first version.

 Depending on the construction techniques used, the "rear" thermal insulation of the structure is either integrated into the structure or separated. In the first case, the assembly constitutes a sandwich which is possibly load-bearing if the insulating structure allows it. In the second case, the insulating material is attached to the structure of the building, on the wall of the facade, or on the frame of the roof.

The solar structure is then connected to the insulating assembly or to the structure of the building by added elements such as: spacers, beams, sleepers, etc.

 The isolatlon. consists of a low density material such as those commonly used in building or industry and on which is advantageously placed a skin reflecting infrared radiation emitted by the bodies (called black) in a temperature range from 300 to 4000K and low emissivity of these radiations, for example: a shiny aluminum sheet. This skin can also, in a variant of the invention, be placed on the rear face of the claimed honeycomb structure.

 The essential characteristics of the plaster or coating claimed are optical, thermal and mechanical. Depending on the material used as the basis of the tubular honeycomb structure, the coating adheres more or less well to the material and certain pre-treatments must be carried out. For polycarbonate, adhesion is excellent while for polypropylene and polyethylene the adhesion is weak.

To improve adhesion, the structure generally obtained by extrusion is designed to allow mechanical attachment, either directly at the level of the tubular elements, or by protuberances making it possible to insert the coating; the latter is applied in a pasty state, then hardens in air while retaining the plasticity and elasticity making it possible to follow the deformations and dilations of the structure.

 The optical characteristics of the coating are, in addition to those relating to color, a very high absorption of visible radiation and infrared solar radiation in the area of 0.7 to 3 microns and a low emission of infrared thermal radiation in the area of 5 to 30 microns for applications in countries where the need for heating has priority. On the other hand, in hot countries, the high emission of the abovementioned thermal radiation is sought and the composition of the coating is modified accordingly, the optical surface properties being linked to the surface layer of the coating.

 One of the very important consequences of the composition and surface finish of the plaster is its paradirectionality which allows it to absorb solar radiation whatever its incidence relative to the layer, and this in the absence of transparent cover. , which is not the case with any absorber currently used and which makes it possible to considerably increase the time for capturing solar thermal energy.

 The thermal characteristics of plaster, in addition to those linked to infrared thermal radiation, are based on good heat conductivity; this is obtained by the presence of microcalibrated fillers and / or known good conductive reinforcements such as micrograins of silica or basalt, or else very good conductors such as aluminum filings or other metals. These charges, the particle size of which is decided according to the desired aspect, must be characterized by a very low emission of infrared radiation.

These fillers are coated in a binder which is an aqueous emulsion and / or a mixture of emulsions of polymers or copolymers such as those based on vinyl acetate and maleic esters or copolymers based on styrene and acrylic esters; the binder can also consist of conventional products such as: asphalt, bitumen, etc., of resins such as: epoxy resins, polyurethane resins or polyamide resins, all these resins being characterized by very high resistance ultraviolet, solvents, and very high resistance to breakage.

 The dyes used in this coating are based on metallic oxides which have low emissivity in infrared radiation, such as red or black ocher iron oxides, yellow or black chromium oxides, white titanium oxides, etc. , a coating which gave excellent results was composed of 68 Z of calibrated silica with a particle size between 0.1 and 0.3 mm, 30 Z of vinylic and maleic copolymers in aqueous emulsion at 50 Z and 2 Z of dyes consisting of red ocher, chromium yellow, iron oxide black, titanium white, the dilutions being made with water and dosed according to the viscosity of use.

 The mechanical characteristics of the plaster, namely: resistance to impact, expansion and deformation. are obtained by the nature of the fillers and their percentage, by the adaptation of the thickness of the coating, by the choice of the binder and by the possible presence of a reinforcement. The choice is made according to the operating temperatures and the aggressions envisaged.

 The addition of cement gives hardness but reduces elasticity and plasticity. Asphalts or bitumens applied hot or in emulsion give flexibility and plasticity, hardness having to be ensured by the nature of the fillers.

 The mechanical characteristics must be sufficient when the temperature varies. The plaster must not be brittle at low temperature or soft at high temperature, finally the plaster must resist rain and humidity when it is placed on a roof and when it also serves as a facade coating. In the latter case, an alternative embodiment of the invention comprises, in front of the coating, a transparent surface which is totally or very permeable to infrared radiation; this surface is a few centimeters from the plaster and is held by a support frame, the assembly constituting a greenhouse and protecting the plaster from heat loss due to the wind and the presence of fresh air. The constitution of the transparent surface is advantageously a film or a sheet of known plastic such as: polyvinyl chloride or polyfluoride, polyethene - lene, polypropylene, polyester, polyethylene tetrafluoride, polyolefins, polycarbonates, methacrylates and various commercial films characterized by special compositions and / or treatments protected by patents and having particularly advantageous mechanical, optical and thermal properties.

 For certain embodiments based on reinforced films or sheets or of cellular structure, the thickness is large enough to consider the transparent surface as a thin plate.

 The use of transparent surfaces is mainly reserved for structures with vertical facades or slightly inclined with respect to the vertical, oriented to the south, southeast and southwest, and used in winter when the sun is low on the horizon and the incidences are still strong and fairly close to normal.

 The avéalr! E structure is obtained by extrusion. It is made of e-trudable materials having mechanical and thermal characteristics suitable for the applications. Among the known materials which can be used, let us mention, without limitation, polyvinyl chloride, polyethylene, polypropylene, polyearbonate, polymethacrylates, polyamides, silicones, elastomers and thermoplastics.

 The honeycomb structure is connected at its ends to collectors by welding, gluing or fitting, the collectors being drilled with holes or split along their length depending on the type and shape of the honeycomb structure and the collector.

 The longitudinal slot is suitable for honeycomb structures, with square, rectangular5 trapezoidal and even circular channels, the collector-honeycomb structure connection being by gluing or by welding.

 Direct connections with elastomer sleeves are reserved for circular tubular channels where the tubes are easily separable from each other.

 The taps to be screwed and / or fitted are reserved for circular channels. These types of tapping are commonly used in drip irrigation equipment.

 The collectors are perpendicular to the channels. The flow of the heat transfer fluid is carried out either in the direction of the slope, from bottom to top or from top to bottom, or transversely to the slope, the positions being chosen according to the circulation system used and the deformations of the structure. alveolar.

 For certain applications, the structure remains flat. As the changes in appearance are limited to the coating, the channels are indifferently in the direction of the slope or perpendicular to this direction. For other applications, such as imitation of round or Roman tiles, the structure must be deformed; the channels are, in this example, advantageously perpendicular to the slope and the collectors in the direction of the slope. When the structure must be specially shaped, the base material is either thermoplastic deformable when hot and rigid at operating temperatures, or deformable when cold like elastomers and certain plastics. In this second case it is the coating which, as it dries, will form a rigid shell.

 For example, the materials of the first case are polycarbonates, polymethacrylates, polyacetals, rigid polyvinyl chlorides and polypropylenes. In the second case, let us quote polyethylenes, silicones, polyamides, "plasticized" polyvinyl chloride and elastomers.

 Another characteristic of the coating according to the invention is its sealing and its compatibility with certain materials commonly used in sealing, which allows a good connection with the gutters covered with a sealing strip and with the walls at the level of the flashings.

 The use of the solar structures according to the invention depends on the period of the year considered, the latitude, the inclination and the orientation of said structures. In the northern hemisphere in mid latitudes with a temperate climate, vertical or near-vertical structures, protected by a transparent cover, are used in winter for space heating and in summer for hot water production . Indeed, for a beautiful sunny day, the solar energy received is of the same order of magnitude all year round, but, in winter, there are more wind clouds, and the outside temperature is colder. To maintain good performance, the temperature of the heat transfer fluid can hardly exceed 25 to 300C; this temperature can be used in a floor heating with a high density of tubes.

In summer, the ambient temperature is higher, the energy requirements for domestic hot water are reduced compared to winter heating, so that the front sensors are more than sufficient for heating domestic hot water at a temperature of the order of 509C. In addition, while for a villa and an average family, the surface of well-oriented collectors for the summer is around 3 to 6 m2 for the supply of domestic hot water, in our case the frontage collection surface. is of the order of 10 to 30 m2, which is more than enough to compensate for the bad inclination.

 Still in the northern hemisphere, in the mid-latitude zones, of the order of 30 to 500, the roof structures which are fairly slightly inclined on the horizontal, from 00 to 459, can be used for a small part in winter, in much of it in spring, summer and fall. In autumn and spring, the use of the heat collected is used for space heating and / or domestic hot water; in summer, the heat collected is used for heating domestic hot water and, possibly, for producing cold in an absorption refrigeration unit.

 For this last application, the solar heat captured is the hot source of the absorption refrigeration unit, that which replaces the burner. Finally, still in the case of the absorption refrigeration unit, it is advantageous in winter and during the heating season, in the event of insufficient solar gain, to use the refrigeration unit as an absorption heat pump with an auxiliary burner fuel or with electrical resistance. Heat can thus be transferred from the roof to the heating system, this heat adding to that of the burner or electric generator.

 Depending on the architectural design of the premises, the latitude and the climate, one of the two inclinations, strong or weak, is used or both inclinations.

 In the presentation of the structures, these are linked to any building. The structures claimed according to the invention also apply when they are placed on the ground or supported on supports independent of the buildings, such as posts, fences, copings, terraces, embankments, low walls, earthen or dry stone levees, pergolas, winged ...

 It should be noted that this heating and air conditioning process is fully integrated into the construction which, from the outside, does not differ in any way from a conventional construction and that the structures used are not a supplement to the building but replace all way of the elements which would have been necessary, which gives a cost price for a solar house (heating and air conditioning) very little higher than a classic constructior.

r DESCRIPTTON
Plate 1/2, we see Fig. 1 and 2, in 1, the coating in the form of corrugated tiles with the step 2 caused by the variation in thickness of the latter. In 3, under coating, is the honeycomb structure composed of channels which, here, are in the direction of the corrugation, which structure is connected to a collector which we will see and describe in detail Fig. 9 Plate 212. In 4, we see the reflective surface that can serve as a rigid support and, in 5, the insulation.

 Fig. 3, 4, 5 and 6 are represented variants of structures and we see Fig. 3 the coating at 6, a plastic structure comprising the channels where the heat transfer fluid flows at 7, which plastic structure comprises profiles at 8 enabling it to be fixed on a frame 9 above which the reflector 10 is located.

 Fig. 4, we still see the plaster at 11, which has a stiffening frame 12 and is deposited on a plastic structure 13 comprising pipes, which is itself fixed by spikes, screws or staples 14 on an insulator 15 separated from the structure by the reflector 16.

 Fig. 5, another variant always shows us a coating 17 deposited on a plastic structure comprising the pipes 18 themselves comprising asperities 19 allowing good adhesion of the coating. At 20 is the reflector and at 21 the insulator.

 Fig. 6, here the coating 22 includes a possibly pierced or perforated stiffness plate 23 and, in this coating, pipes 24 are introduced, the spacing of which can be determined by wires 25, all placed on the reflector 26 and insulation 27.

 Plate 2/2, are shown in Fig. 7 and 8 of the modular rigidity plates 28 covered with the coating 29, fitted one into the other like normal tiles by the sides at 30. These tiles come to crush extruded mono or multi-cellular sheaths 31 on which they are glued ; these sheaths are used for transporting the heat transfer fluid and they are held by lss ~ tiles on the reflector 32, itself placed on the insulation 33. Screws 34 hold the tiles together on the whole structure. Finally, in Fig. 9, as we pointed out at the beginning of this description, is detailed the connection of a type of honeycomb structure on the collector of the heat transfer fluid; this type of connection is not limiting and is presented by way of example. In 35, we see the plaster, in 36 the honeycomb structure, in 37 the reflector, in 38 the insulation, in 39 the collector, the connection being made by a slot in which the structure in 40 is encrusted glued according to 41 and , at 42, an ridge shape including the collector and connecting with the tiles formed by the coating at 35 and having the same appearance and covered with the same coating.

Claims (10)

 1. Device for capturing solar energy, characterized in that it consists of a coating which is a very good absorber of solar radiation, deposited on an alveolar structure with channels in which a heat transfer fluid circulates, said structure being obtained by extrusion a material based on elastomers or thermoplastics.  2. Device according to claim X characterized in that the coating is based on aqueous emulsion or mixture of aqueous emulsions, polymer or copolymers of vinyl acetate and maleic esters, or copolymers based styrene and acrylic esters colored with suitable metal oxides and loaded with mineral matter in the form of micrograins causing an optically paradirctual surface state.  3. Device according to claim l characterized in that the cellular structure of plastic or elastomer is in the form of corrugated tiles cold or hot and where the coating is applied in curable paste and whose constituents form, after hardening, a shell which can be covered with a layer of materials which absorb solar radiation well.  4. Device according to any one of claims 1 to 3 characterized in that the coating is applied in the form of paste and has reliefs imitating a stall of tiles, or slates, or bricks, or stones, or traditional facade coatings or plaster.  5. Device according to any one of claims from i to 4 characterized in that the coating contains a reinforcement in glass fibers or in fibers of plastics with high mechanical resistance or in metallic wires  6. Device according to any one of claims from 1 to 5 characterized in that the coating is covered with a thin layer of colored binder with a low content of mineral fillers 7. Device according to claims from to 6 characterized in that the cellular structure in thermoplastic material is shaped by thermoforming, the shape obtained imitating the undulation and / or the unhooking of tiles.  8. Device according to claim 3 characterized in that the frame is rigid and metallic and has the apparent shape of a tile of determined design, and is applied to a honeycomb structure or on sheaths where the heat transfer fluid circulates.  9. Device according to any one of claims from 1 to 8 characterized in that the coating is protected from wind and weather by a cover transparent to solar radiation, which is placed a short distance from the latter.  10. Device according to any one of claims 1 to 8 characterized in that the coating is covered with a varnish transparent to solar radiation which protects the latter from deterioration due to bad weather and atmospheric pollution.