FR2469674A1 - Solar energy trap with absorbent bodies of corrugated bitumastic board - to smooth variations in the rate of energy capture - Google Patents

Abstract

A solar energy trap is made from sheets of corrugated bitumastic cardboard supported on a layer of thermal insulation and opt supporting a transparent cover sheet. Air from a supporting building is recirculated between the corrugations. The cellulosic board may be coated on the external surface with a matt paint, pref of dark colour, e.g. dark blue. The insulation layer pref is of slab phenolic foam. The covers may be of hollow, double-skinned polycarbonate sheet. Traps without ancillary covers have a thermal efficiency of 5-30 % (i.e. produce 50-300 watts/m2 at 20-50 m3/h.m2 flow rates from 1 kW incident thermal energy), are suitable for mounting on or acting as barn roofs or walls for dying crops etc. Traps with covers may achieve 30-50% or higher thermal efficiency, for space heating of houses etc, using flow rates of 5-20 m3/h.m2 trap area. The combination of high thermal capacity and low thermal conductivity of the bitumastic board smooths variations in incident energy due to changes in e.g. wind/cloud cover/sun position to produce a relatively even rate of heat transfer to the recirculating air. The components are relatively light, cheap and simple to assemble to suit various non-modular supporting shapes/areas.

Description

The present invention relates to the collection of solar energy.

 It relates more particularly to a system making it possible to capture and even store solar energy, as well as to limit the variations that solar energy collected frequently undergoes over short periods.

 To collect energy radiated by the sun which reaches the earth, it is necessary to have sensors on the ground or on the constructions in which this energy is to be used.

The capture of solar energy in thermal form can be achieved either by greenhouse effect or trapping between two surfaces, or by concentration by means of converging mirrors. The invention described below relates to the first of these two types of collection.

 Solar energy collectors are already known which are in the form of planar modules of defined size, which it is possible to integrate into a roof or cladding, and of which several unit modules can be juxtaposed and connected together. Such systems however constitute an additional cost compared to the cost of the roofing or cladding; they also require the provision of additional sealing elements around their periphery, the cost and imperfections of which also constitute drawbacks; they also require connections under the roof, either between juxtaposed modules placed in series, or in any event to allow circulation in and out of these modules, of the heat transfer fluid.

We also already know some realizations of ventilated solar roofs, in which the collection system consists of the roof itself, supplemented so that it includes the elements necessary for this type of collectors, namely, interior to the interior, thermal insulation, a possible absorber and potential for ventilation. Such a system would, in theory, make it possible to use large areas for the capture of solar energy with a reduced cost of realization, since the materials normally used in construction (roofing and insulation material) hold both their traditional role and a role in the solar energy collection system.

Such systems are generally designed with blackened metal sheets or plates, placed on an insulator and surmounted, or not, with protective glazing, ensuring a greenhouse effect.

However, such systems, although they actually make it possible to capture part of the solar energy radiated on their surface, on the other hand practically cannot ensure a storage of captured solar energy, nor a fortiori a distribution of this with clipping variations sudden which it undergoes under the influence of sunshine variations> due to the low calorific capacity of the blackened absorber and its very good heat conducting power. Under these conditions, the air delivered by these known air sensors is subject to sudden temperature variations, due to the succession of sunny and cloudy periods which often punctuate a day; this results in certain discomfort for the occupants of buildings using such sensors for their heating, or a risk of irregular drying of the products if the collection system considered is coupled with a product drying system in an industrial or agricultural installation.

 These air sensor systems therefore require an intermediate energy storage system, interposed between the collection itself and the distribution.

 Another disadvantage of the known systems recalled above is the high loss of energy, and the considerable reduction in the daily yields of the system, which must be deplored in the case where incident solar energy is large and greater than the needs of the building concerned in heat energy. : so that there is no overheating then inside the estimate, we must use a regulation which, imposing the stopping of air circulation in the sensor, causes the temperature to rise quickly. The majority of the energy captured is then purely and simply dissipated by heat loss, the materials of the sensors considered revealing themselves incapable of storing received energy, and this is no longer available in the sensor to be distributed during the restart air circulation as soon as clouds reduce the amount of sunshine. Again, this drawback can be remedied in known systems only by interposing, between the collection of solar energy and its distribution, of a complex storage system.

We have now unexpectedly found that an extremely simple and inexpensive system for capturing, storing and distributing solar energy can be produced with clipping of the sudden variations which it undergoes under the influence of the variations in sunshine, thanks to the use as absorbent material for profiled bituminous cellulosic materials.

 The present invention firstly relates to a system for capturing, storing and distributing solar energy with clipping of the sudden variations which it undergoes under the influence of variations in sunshine, basically comprising, from the interior to the interior, a thermal insulation material J arranged vertically or at any angle on the horizontal, and an absorbent material made up of profiled bituminous cellulosic elements fixed on this insulation material so as to define a continuous collection surface and to provide air inlets on one edge of the system, while the other edges are obscured, as well as a device suitable for extracting, continuously or discontinuously, the air located between the insulation material and the absorbent material and entraining it inwards of a building where this hot air must enter a heating or drying cycle for wet products.

The invention also relates to a system as described above and in which a glazing unit is fixed on at least part of the external surface of the profiled bituminized cellulosic material, with concealment of the spaces between the profiled bituminized cellulosic material and this glazing, except on an edge thereof. A very particular advantageous variant of the system according to the invention is thus produced, but it is remarkable that it can be perfectly implemented without this over-glazing.

 It has indeed been fortuitously established that, contrary to generally accepted opinions, the circulation of ducted air between a profiled bituminized cellulosic material and the insulating material on which it is fixed achieves a very suitable capture of solar energy, same as a storage thereof, and even a very advantageous clipping of the sudden variations that the captured solar energy undergoes under the influence of the variations in the sunshine owing to the semi-insulating nature of the absorbent material considered.

 In the following, the invention is described, for simplicity, with reference to corrugated bituminous cellulosic panels, but it is clear that a bituminized cellulosic material comprising profiles of any type would be just as suitable.

 It will be noted that theoretically this system can also operate horizontally, but that, for practical reasons (among which the sealing problems posed by any system comprising joints placed horizontally outside), it is preferable to recommend its installation according to a slope P on the horizontal, with 0 <P # 90.

On the other hand, although it is possible to integrate solar energy collectors according to the invention in only part of the roofs and / or external walls of existing buildings or under construction; it is quite remarkable that the sensors according to the invention can advantageously merge with these roofs and / or these external walls, and constitute all of them, except for the support elements and the accessories ensuring good sealing of the assembly.

 The system according to the invention therefore has the non-negligible advantage of not being subject to dimensional constraints; not being modular, it does not require multiple connections and it can be simply mounted, on request, to the dimensions and in the specifications (independent for each of the constituent elements of the system) adapted to each case, depending desires of users, firlities, and local constraints, especially with regard to sunshine.

 The element ensuring the function of thermal insulation in the system according to the invention can be constituted by any insulating material known to those skilled in the art and suitable for this use. In practice, but this is only an illustrative example, rigid panels made of phenolic foam can be used for this purpose, the thermal insulation characteristics of which are quite suitable, and which themselves may advantageously include members , for example in wood, which improve their mechanical resistance and facilitates their installation on the farm, the farmhouse or the rafters, or on the uprights of vertical wall structure.

 The profiled bituminized cellulosic material can be any profiled bituminous cardboard, and preferably corrugated bituminous cardboard plates, marketed under the registered trademark Ondulin and more advantageously corrugated bituminized cardboard plates (such as Ondulin plates) covered, less on their face located towards the outside of the system according to the invention, of a coating providing roughness capable of enclosing an air mattress, of thickness certainly small but capable of reducing the incidence of convection currents and therefore heat loss. This coating advantageously comprises dark granules, in particular granules of a color which absorb radiation well.

It has indeed been able to establish that this variant of the system according to the invention has the additional advantage of retaining a protective shell of hot air on the surface of the absorber, thereby reducing the heat losses between the sensor and the ambient air and thus further improving the heat storage capacity of the sensor
The profiled bituminized cellulosic material can be fixed by any means to the insulating material, and in particular by nailing, screwing or gluing.

 In the variant of the system according to the invention ~ tion which includes a glazing, this glazing can be fixed by any means known to those skilled in the art on the bituminous profiled cellulosic material. It can of course be a glass, but preferably rather a synthetic glass or any other suitable transparent plastic material, such as a polycarbonate and advantageously a double skin alveolar polycarbonate. It is indeed known that the transparent sheets of double skin alveolar polycarbonate currently available on the market have excellent mechanical properties and have excellent aging behavior from the point of view of their optical and mechanical characteristics. Such polycarbonate sheets can be nailed, glued or screwed onto the profiled bituminous cellulosic material.

 It should be noted that this glazing can itself be cut, for example corrugated. In practice, however, planar glazing is preferred.

 To complete the system according to the invention, in one or other of the above-mentioned variants, a device for extracting the air between the insulation material and the absorbent material should also be added thereto. . This air extraction device can take any suitable shape and constitution and can be located at almost any location in the solar energy collection system. However, for practical reasons, it is often preferred to arrange it in the upper part (that is to say in ridge for the roofs); according to an advantageous embodiment, this device takes the form of a trough of any cross section, for example open rectangular, open square, semi-circular> U or V, and rests on the one hand on one corrugated edges of the absorbent material, and on the other hand on the corresponding edge, set back from the previous one, of the insulation material, so as to obscure vis-à-vis the outside the spaces between the absorbent material and the insulation material, but to open these spaces, in practice kept open to the open air at their other end, in the trough thus defined. I bottom this trough, which can be flat or take any other shape , can extend beyond the plane of the internal face of the insulation material towards the interior of the building, but it can also go only below or at best be confused with this plan, in particular in the case of existing structures, which it is desirable not to have to touch up er. An air suction-blowing system for this chute must be attached to it to take the air and blow it, intermittently or continuously, directly into the building or into any heating system or drying system to which the system according to the invention can thus be subjected. In practice, the chute is provided, at one end or in an opening which has been formed therein, with a sheath of an appropriate diameter to avoid pressure drops , opening itself at its other end in a suction-blowing device such as a fan, a turbinessetc.

 On the other hand, it has been found according to the invention that the above-mentioned system gives, in both of its variants, the best results from the point of view of efficiency when the air flow rates sucked-in by this device is approximately 5 to 20 m3 / h.m2 of collector surface for building heating, and approximately 20 to 50 m3 / h.m2 of collector surface for use in an industrial or agricultural dryer.

The system thus described in its essential organs can obviously be supplemented by other elements or accessories, such as those which are conventionally used in roofing and cladding, in particular for improving sealing, such as for example a waxing piece.

The invention is described below in more detail with reference to the accompanying drawing plates which illustrate two embodiments corresponding to the description above and in which
-l ig. 1 is a partially cutaway perspective view of a system according to the simplest variant of the invention;
-Fig. 2 is a partially cutaway perspective view of a system according to the invention, comprising a glazing in double skin cellular synthetic material;
Figs 3 and 4 are graphs showing, on concrete examples, described below, the efficiency of the systems according to the invention, with, on the abscissa, a time scale graduated from hour to hour and representing the times of the day where the measurements were made, and, on the ordinate, the incident solar power in watts / m of collector, and the temperatures in C.

 The systems according to the invention notably have the advantage of being an extremely easy and less restrictive embodiment than known systems, of very low cost and of remarkable and unexpected efficiency.

 It is of course possible to make modifications or other variants to these systems without departing from the scope of the invention. This is how we can, if we consider it more advantageous, take the air supplying the sensor, at least for a part, inside the building itself, if the air recycling that this implies It does not appear to be annoying. We can also provide for various assass piations of this system, for example to make them dedicate a role rather of storage at the end of the tour and make them restore the energy thus stored, instead or in addition to other heating, at the start of the nights in the case of residential premises, or even to thus provide protection against freezing of second homes.

On a test roof at 450 of 13 m2 produced in accordance with the invention with protective glazing in double skin alveolar polycarbonate, daily yields of 53% were thus obtained, or 530 usable watts per square meter of collector area for 1000 watts of incident energy, and hot air was then delivered at an average temperature of over 40 C.

The invention is now described in more detail with reference to specific embodiments, which in no way limit it and serve only as an illustration.

EXAMPLE 1.

The system developed and implemented in this example corresponds to FIG. 1 attached.

Insulating panels (1) made of phenolic foam were mounted on the roof structure of a double-pitched roof, and a hot air collector (2) was placed on the roof, as shown in partial perspective in the figure. 1, suitably supported on the upper edge of the insulating panels as shown, and to which was added a suction fan (not shown), the outlet of which led to the interior of the bStlment located under this roof.

Plates of corrugated bituminized bituminous cellulosic material (3), commercially available under the name Onduline, of 2 mx 0.90 m, covered on one side (which was that which was turned towards the exterior) of a dark blue granular coating. These plates were placed and fixed with the conventional coverings, without seeking to ensure an absolute seal from plate to plate.

A 13 m2 plane sensor was thus produced. Classic ridge plates, ~ not shown, were added to this system. In operation, the ventilator sucks in the air which circulates under the corrugated plates and heats up slowly, already rising by itself along the roof. The circulation of hot air was therefore in the direction indicated by the arrows in Figure 1.

 With this system in operation, an efficiency of 24% was obtained for an air flow rate of 20 m) / m2 of sensor and per hour.

It has also been found that a peak temperature peak due to sudden variations in sunlight is thus obtained, and a certain storage effect.

 The yields varied from about 5 to 30 (which corresponds to 50 to 300 usable watts per square meter of cover for 1000 watts of incident energy), while the hot air was delivered by the blower-extractor device at a temperature higher than 30 to 50C at room temperature, with an air flow of between approximately 5 and 40 m3 / m2 of sensor and per hour.

This system is very economical, because the only additional cost it entails is that of collecting and distributing the heated air in the sensor. In return, the yield is only relatively low and the air is supplied at a moderate temperature.

Such a system is particularly useful for providing heat to buildings for agricultural breeding, for drying products such as, for example, hay, grains, tobacco, etc., for protection against frost, especially in in the case of unoccupied second homes, or for the protection of premises against humidity.

EXAMPLE 2.

 The system produced according to this example is illustrated in FIG. 2 attached.

This system was carried out by operating as indicated in Example 1, except that> before placing the ridge plates, it was still fixed, by nailing on the plates of corrugated bituminized cellulosic material, transparent flat plates (4) in plastic, in practice in double skin alveolar polycarbonate.

 Compared to a conventional corrugated roof, the additional cost it entails is only that of glazing, of collecting and distributing hot air.

 However, we reached with; this system of outputs varying from 30 to more than 50% (e which corresponds to 300 to 500 usable watts per square meter of coverage for 1000 watts of incident energy), the air flow being between approximately 5 and 40 m3 / rn2 of sensor and per hour.

 With this system in operation, the results recorded on the graph in FIG. 3 were obtained for an air flow rate of 16 m3 / m2 of sensor and per hour.

This figure 3 includes three curves representing respectively, depending on the time of the day on which the measurements were made (1) the ambient temperature, taken outside and under shelter, in C, (2) the power incident solar, in W / m, on the collector, and (3) the temperature of the air distribution issv of the collector at the outlet of the collector, in C.

 On the other hand, we obtained with this system, first stopped then started up at time T (with an air flow of S m / m of sensor and per hour), the results recorded on the graph of the FIG. 4. This FIG. 4 comprises three curves homologous to the curves (1) to (3) of FIG. 3.

The system thus produced therefore proved to have a clear capacity for peak temperature peaks due to abrupt variations in sunshine, and it had a very high efficiency in trapping the energy received and storing it in the cellulosic material. bituminized.

Claims (11)

 1. solar energy storage and distribution collection system with clipping of the sudden variations which it undergoes under the influence of the variations of the sunshine, characterized in that it basically comprises, from the interior towards outside, a thermal insulation material arranged vertically or at any angle on the horizontal and an absorbent material made up of profiled bituminous cellulosic elements fixed to this insulation material so as to define the surface and continuous collection and provide air inlets on one of the edges in the system, while the other edges have obscured, as well as a suitable device for extracting, continuously or undiscovered, the air located between the insulation material and the absorbent material and entrain it towards the interior of a building Where this hot air must enter a heating or drying cycle for wet products.  2. System according to claim 1, characterized in that it comprises a glazing fixed on at least a part of the external surface of the profiled bituminized cellulosic material, with occlusion of the spaces between the profiled bituminous cellulosic material and this glazing, except on an edge of it.  3. System according to one of claims 1 or 2, characterized in that the main axis of the profiles of the profiled bit-uminated cellulosic material is substantially parallel to the line of slope of the system on the horizontal.  4. System according to any one of claims 1 to 3, characterized in that the profiled bituminized cellulosic material consists essentially of a corrugated bituminized cellulosic cardboard.  5. System according to any one of claims 1 to 4, characterized in that the profiled bituminous cellulosic material is covered, at least on its face situated towards the outside, with a coating providing roughness capable of enclosing a air mattress.  6. System according to claim 5, characterized in that the coating comprises granules of a color which absorb radiation well, in particular dark blue granules.  7. System according to any one of claims 1 to 6, characterized in that the thermal insulation material consists essentially of rigid panels of phenolic foam.  8. System according to any one of claims 2 to 7, characterized in that the glazing consists of transparent sheets of double skin alveolar polycarbonate.  9. system according to any one of claims 1 to 8, characterized in that the device for extracting the air comprised between the insulation material and the absorbent material comprises a chute of any cross section, bearing, on the one hand, on one of the corrugated edges of the absorbent material, and on the other hand on the corresponding edge, set back from the previous one, of the insulation material, so as to obscure vis-à-vis the outside the spaces between the absorbent material and the insulation material, but to open these spaces, in practice kept open in the open air at their other end, in the chute thus defined, as well as a device for 'suction-blowing connected to this chute so as to extract the air.  10. System according to claim 9, characterized in that it comprises a glazing, and the aforesaid chute also performs complete concealment, on the side where it is located, of the spaces between the glazing and the profiled bituminized cellulosic material.  11. The system as claimed in claim 9, characterized in that the suction-blowing device extracts the air from the chute at a flow rate of approximately 5 to 20 m3 / h.m2 of collector surface for heating of bSkiment, and approximately 20 to 50 m3 / h.m2 of collector surface for use in an industrial or agricultural dryer.