LU84694A1 - SOLAR CAPTOR - Google Patents

Description

"- 1 - s The invention relates to a solar collector which includes an absorbent plate which is provided on at least one face with a light absorbing layer, is internally provided with at least one flow channel for a 5 thermal transfer fluid and has an inlet and an exhaust for this fluid, which are placed in mutual communication by the flow channel, solar collector which also includes a housing which surrounds the absorbent plate, is at least partially translucent and is „10 filled with a thermally insulating gas.

A solar collector of this kind is described in FR-A-2,343.208. The thermally insulating gas in the housing is, however, at atmospheric pressure.

This is also the case for the solar collector 15 according to DE-A-2,610,370.

An object of the invention is to offer a solar collector of the aforementioned kind which has an even higher yield than that of the aforementioned known collectors.

For this purpose, the housing is filled with a gas 20 with a coefficient of thermal conduction of 0.015 W / m ° C

at most, at a pressure below atmospheric pressure.

In a particular embodiment of the invention, the gas pressure is of the order of 10 to 100 millibars.

In a preferred embodiment of the invention, the absorbent plate is coated on either side with a selective absorption layer, the housing is made on either side, at least locally, of translucent material and a thermally insulating gas at a pressure below atmospheric pressure is located on either side of the absorbent plate, between the latter and the housing.

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The aforementioned known solar collectors operate unilaterally. The absorbent plate is covered on one side with an insulating material and the thermally insulating gas is only on the other side, provided with a small thermally insulating layer. Naturally, thanks to bilateral operation, the solar collector in the presence of white or mirror reflectors can be subjected to a higher illumination of 50 to 80% by comparison. right with a one-sided sensor, both with diffuse light and with direct radiation.

; · Solar collectors with an active absorbent plate on both sides are known per se, in particular from FR-A-2,357,832 (embodiments according to Figures 10 and 11). The collectors are however not filled with a thermally insulating gas under reduced pressure, which is necessary for fear that a solar collector active on both sides has a higher yield than that of an active collector unilaterally.

Other details and advantages of the invention will emerge from the description of a solar collector according to the invention given below as an example and not limiting the invention; the references relate to the attached drawings.

Figure 1 is a side elevational view of a solar collector according to the invention.

Figure 2 is a sectional view along line II-II of Figure 1.

Figure 3 is a front elevational view of the solar collector of the previous figures, but on a smaller scale and with partial broken lines.

Figure 4 is a sectional view along the line IV-IV of Figure 3, on a larger scale.

Figure 5 is a sectional view along the line V-V of Figure 3, on the same scale as Figure 4.

In the various figures, identical references relate to similar elements.

The solar collector according to the figures 5 consists of an absorbent plate 1 and a case 2 for the latter.

The shell 2 is essentially formed by a rectangular frame 3 and two tempered glass plates 4. The frame 3 is formed by four profiles of mild steel 10 in the shape of an omega, which are directed with their opening towards the outside and are welded to each other in the corners. These profiles are located with their edges facing outwards opposite the side walls of the plates 4. The latter are glued to the frame 3, in an airtight manner, using thiokol and silicone rubber 5 .

This housing 2 is placed vertically with its horizontal longitudinal direction above a base, for example a roof. This base and this roof are preferably coated with a reflective material and next to the solar collector, reflectors can be placed on this base so that the solar collector receives as much sunlight as possible. The housing 2 is provided on the outer face of the two upper corners 25 of its frame 3, with two welded brackets 6. The latter serve to grip the sensor during its movement, for the connection of the electrodes during treatment. i electrochemical of the plate 1 mounted in the frame ^ '3 during the manufacture of the sensor and for fixing the sensor for example to a vertical wall.

On the internal side of the frame 3 are welded in different places supports 7 for the absorbent plate 1. These supports 7 are angles whose rib is perpendicular to the plates 4. The angles - 4 - - -> 7 are welded by their edges parallel to this rib, to the internal face of the frame 3; their angle is therefore directed inward. This angle is intersected by a groove 8 in which an edge of the absorbent plate 5 fits 1.

In the lower profile of the frame 3, two openings 9 and 10 are also made for, respectively, an inlet 11 and an exhaust 12 of the absorbent plate 1.

This absorbent plate is a flat radiator plate made of mild steel or copper, which is coated on either side with a selective absorption layer with a high absorption coefficient and a low emissivity. The absorbent plate is formed by two rectangular plates 13 which are welded to each other by their edges 14, over their entire periphery. Between the longitudinal edges 14, recesses 15 extending in the transverse direction have been made in the plates 13, at the place where the plates 13 are also welded to one another. In this way, there is formed in the absorbent plate 1, on the upper side a supply volume 16 and on the lower side a discharge volume 17, volumes 16 and 17 which are connected by channels 18 which are formed between the recesses 15.

25 The absorbent plate 1 penetrates through the welded edges 14 into the supports 7. During thermal contractions and expansions, the plate 1 can slide back and forth in the supports 7. The inlet 11 opens into the supply volume 16 and extends in the case 2, upwards along the absorbent plate 1, from the opening 9. At the location of the latter, the inlet 11 is provided with a connector 19 for operation of a solar energy installation. The exhaust 12 extends between the discharge volume 17 and the opening 10 and is

X

- 5 - also provided at the location of the latter, with a connector 19 for connecting the exhaust 12 to the pipe of a solar energy installation. The connections 19 are welded to the frame 3, so that they 5 provide hermetic sealing of the openings 9 and 10.

They are used as electrical contacts during the aforementioned electrochemical treatment of the absorbent plate 1.

The selective absorption layer with which the absorbent plate 1 is coated depends on the metal from which the plates 13 are made. This layer preferably has an absorption coefficient which is greater than 0.9 and an emissivity which is less than 0.1. . This layer must withstand heat up to temperatures of around 300 ° C.

The plates 13 can be made of steel, in which case a suitable absorbent coating is formed by a layer of copper which has undergone a slight chemical oxidation to matt black, by zinc chromate oxide. on zinc, or with chromium oxide on nickel or copper. The plates 13 can be made of copper, in which case a suitable absorbent layer is a layer of chromium oxide or copper.

The space between the absorbent plate 1 and the housing 2 is a completely hermetically closed volume.

This volume is filled with a gas with a coefficient of thermal conduction of 0.015 W / m ° C at most under a pressure which is clearly lower than atmospheric pressure. The gas pressure is for example between 10 and 100 millibars, and is preferably equal to approximately 20 millibars. Suitable gases are: krypton, xenon, hydrocarbon compounds such as

CcEL ·, CrH10 and chlorinated hydrocarbons such as CHCl_, b o b 1Z with freon and CCl4.

To avoid deformation and even breakage * - '"1 - 6 - of the glass plates 4 under the effect of the vacuum prevailing in the housing 2, these plates 4 are maintained. inside the frame 3 by means of separators 20.

5 These separators 20 are formed by a central body which widens and narrows, and by two conical legs connecting to it which are applied by their large round base against the internal faces of the glass plates 4. The separators 20 pass through freely with their bodies 10 openings 21 in the absorbent plate 1. These openings 21 are located at the location of a recess or imprint 15, slightly enlarged at the location of an opening 21.

The openings 21 therefore do not open on the internal side, that is to say on the channels 18 of the absorbent plate 1.

The openings 21 and thus also the separators 20 are located in a square design. The number of openings 21 and the diameter of the base of the feet of the separators 20 depend on the thickness of the glass plates 4. The conical feet of the separators 20 are made of polymethylmeta-20 crylate, polycarbonate or transparent heat-resistant glass. Their central body is made of steel. The separators 20 are held in place by the glass plates 4 themselves, which are pressed towards each other by the upper pressure outside the housing 2.

The openings 21 have a diameter which is greater than the cross section of the part passing through them of the separators 20 and in fact to such an extent that the separators 20 have no contact with the absorbent plate 1 and the latter can also expand. freely under the influence of temperature variations. This expansion can be very strong, because the temperature of the absorbent plate 1 can reach approximately 300 ° C. for maximum solar radiation and without cooling of the plate.

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Since the absorbent plate 1 penetrates by its edges with a certain clearance in the grooves 8 of the supports 7 and can therefore slide slightly with respect to the supports 7, the latter do not prevent this expansion either.

5 The solar collector is suitable for common heat transfer fluids such as water. In the supply volume 16 can be mounted a distributor device connecting to the inlet 11. Since the solar collector is arranged vertically and the absorbent plate 1 is coated on either side with an absorbent layer , it receives relatively a lot of solar energy both with direct radiation and with diffuse light. This amount of energy can be further increased by placing the solar collector 15 perpendicularly on a white reflector or by directing reflectors towards the solar collector.

Since the space between the absorbent plate 1 and the boot 2 is filled with gas with a low coefficient of thermal conduction and under low pressure, and because the absorbent plate 1 has practically no contact with the boot 2, the heat transfer between the absorbent plate 1 and the boot 2 is excessively low. As a result, the efficiency of the solar collector is also high under high working temperatures.

• 25 So when using a mild steel absorbent plate which is nickel plated and has a chromium oxide layer, and which has an absorption coefficient of 0.94 and an emissivity of 0.1 , and with a space filled with CHCl3 at 20 millibars between the absorbent plate 1 30 and the housing 2, the heat transfer coefficient between the absorbent plate 1 and the outside air is only 2 of 0.9 watt per m of housing and per ° C, which corresponds 2 - 8 - * to a heat loss coefficient of 2 watts per m of absorbent plate and per ° C.

It is obvious that the solar collector can however also be used unilaterally, for example on 5 inclined roofs. In such a case, the heat losses can be reduced by placing between the unused faces of the absorbent plate 1 and the glass plate 4 located opposite, a thin sheet of aluminum and / or a glass wool mat. .

The invention is in no way limited to the embodiment described and in the context of the patent application, numerous modifications can be made to the embodiment described, in particular as regards the form, composition, arrangement and number of components which are used to carry out the invention.

Claims (9)

1. Solar collector which comprises an absorbent plate which is provided on at least one side with a light absorbing layer, is internally provided with at least one flow channel for a heat transfer fluid 5 and has an inlet and a exhaust for this fluid, which are placed in mutual communication by the flow channel, solar collector which also includes a shoemaker which surrounds the absorbent plate, is at least partially. translucent and is filled with a thermally insulating gas, characterized in that the boot is filled with a gas with a coefficient of thermal conduction of 0.015 W / m ° C at most, at a pressure below atmospheric pressure. 2. Solar collector according to claim 1, 15 characterized in that the gas pressure is of the order of 10 to 100 millibars. 3. Solar collector according to claim 2, characterized in that the gas pressure is of the order of 20 millibars. 4. Solar collector according to any one of the preceding claims, characterized in that the absorbent plate is coated on either side with a selective absorption layer, the boot is made on either side, at least locally , of trans-lucid material and a thermally insulating gas at a pressure below atmospheric pressure is located on either side of the absorbent plate, between the latter and the case. 4. -¾. - 9 - 5. Solar collector according to claim 4, characterized in that the shoemaker has a frame, two translucent plates mounted on it side by side, which jointly define with the frame a hermetically closed volume, and separators which keep the two translucent plates apart from one another, while the absorbent plate is provided for these separators with openings situated completely next to its flow channel, openings through which the separators 'extend without any contact with the absorbent plate. 6. Solar collector according to any one of the preceding claims, characterized in that the absorbent layer has an absorption coefficient which is greater than 0.9 and an emissivity which is less than 0.1. 7. Solar collector according to claim 6, characterized in that the absorbent plate is made of steel and the absorbent layer consists of one of the following combinations: copper oxide on copper, zinc chromate oxide on zinc, chromium oxide on nickel and chromium oxide on copper. 8. Solar collector according to claim 6,. characterized in that the absorbent plate is made of copper and the absorbent layer is a layer of chromium oxide or copper. 9. Solar collector according to any one of the preceding claims, characterized in that the absorbent plate is mounted in the case with a> possibility of free thermal expansion.