EP0039682A1

EP0039682A1 - Sealing- and venting device for a solar collector

Info

Publication number: EP0039682A1
Application number: EP80901904A
Authority: EP
Inventors: Stefan Yard; Allan Malm
Original assignee: MALM ALLAN
Priority date: 1979-10-09
Filing date: 1980-10-08
Publication date: 1981-11-18
Also published as: WO1981001044A1; SE8004984L

Abstract

Dispositif de scellement et de mise a l'event dans un espace de ventilation entre une surface externe permeable a la chaleur solaire et une surface d'absorption de la chaleur dans un element de chauffage solaire, ce dispositif etant caracterise en ce qu'il comprend au moins un tuyau expansible (9a) desservant un dispositif de fermeture et de mise a l'event a une extremite de l'espace (8) et des moyens (11, 12, 13) connectes au tuyau (9a) pour l'evacuation et l'expansion du tuyau pour ouvrir et fermer respectivement l'espace (8).Sealing and venting device in a ventilation space between an external surface permeable to solar heat and a surface for absorbing heat in a solar heating element, this device being characterized in that it comprises at least one expandable pipe (9a) serving a closure and venting device at one end of the space (8) and means (11, 12, 13) connected to the pipe (9a) for evacuation and expanding the pipe to open and close the space (8) respectively.

Description

^' SEALING-AND VENTING DEVICE FOR A SOLAR COLLECTOR

The present invention relates in general to solar heating installations and, more particularly, to a seal¬ ing and venting device in a ventilation gap between a solar heat permeable surface and a heat absorbing sur- face in a solar collector.

If a solar heating installation is dimensioned for sufficient capacity during the spring and autumn months, the installation will be overdimensioned for the warm summer months and underdimensioned for the cold winter months. The heat shortage during the win¬ ter months can be compensated for by a corresponding additional amount of heat which may be realized by means of some previously known conventional heating plant. For an acceptable heating supply also during the relatively cool marginal periods in the spring and autumn, a relatively large solar collector area is required. A condition for attaining economic viabi¬ lity is that the price per square metre be kept low. One method of realizing this condition is to integrate the solar collector construction in a roof construc¬ tion such that the solar collector forms a part of the roofing material over a corresponding area of the roof.

It is. possible, by utilizing a sufficient solar collector area, to achieve a satisfactory..degree of heat supply during the spring and autumn, but, as is apparent from the above discussion, there will be excess heat during the summer, which, if it cannot be stored, must be led off in some way. Solar collectors which are overdimensioned for the summer months can, during the height of the summer, entail a serious problem, that is, the risk for overheating and boiling. Attempts have been made to circumvent the risk of boiling by con¬ necting the water system of the solar heating installa- 2 tion to expansion vessels or radiators which are placed, for example, in the attic of a dwelling; or quite simply by emptying the water circuit of the solar collector system when the heat absorbing section of the solar heating installation has reached a certain temperature. Granted, in this way, it is possible to eliminate the the risk of boiling, but one is then faced instead .with the problem that the temperature, in the solar collector proper may^' rise greatly, which places high demands on material properties and, in particular in the various types of sealings and connection fittings. Another ex¬ tremely troublesome overheating problem may arise if the circulation pumps included in the installation cease to function, for example, as the result of a power failure. Attempts have been made to resolve this- situation in a manner similar to that described above concerning the first problem with overheating, for example, by allowing the hot water or steam to be drained off from the solar collector system proper to sufficiently large expansion vessels, or by empty¬ ing the system in some other manner when the circula¬ tion pumps cease to function. However, in such an in¬ stance the risk of material overheating increases. A further solution to this problem is to employ an accumulator-driven auxiliary pump which does not come into operation until a power failure has occurred.

A further solution in a prior art solar collector element is to provide, between the "solar collector sur¬ face", that is to say the solar-permeable surface and the heat-absorbing surface, a gap open at two opposite ends, and to provide, at one of the open ends of the gap, an openable sealing valve leaf which is so arranged that it can be opened and closed by means of an operating device which is actuated in direct correspondence to the temperature level in the solar collector element. According to this solution, the gap is always open at its one end and is -opened at the other end for allowing the through-flow of air and there¬ by cooling the solar collector element, in that the valve leaf automatically opens when overheating is de¬ tected. Since it is relatively difficult to operate a large valve leaf, this prior art arrangement calls for the provision of one or more small leaves which open or close correspondingly small ventilation openings in one end of the gap. However, to reduce the risk of overheating and boiling in abnormal operational conditions by air cooling in the gap,, large volumes of through-flowing air may be required, which calls for the employment of large inlet and outlet openings at the opposite ends of the gap. At the same time, to avoid heat losses in normal operational conditions, it is necessary that the gap be well sealed at its opposite ends . Besides, efficient sealing is required around the en¬ tire circumference of the solar collector element. It is difficult to satisfy both of these requirements in- combination.

As was mentioned above, it. is a condition for good heating economy that the price per square metre of the solar collector element be kept low. In order to satis- fy this requirement, the solar collector element should be of large area. The use of large solar heat permeable elements and corresponding collector units entails serious sealing.problems because of the dimensional changes which accompany temperature changes. The major object of the present invention is, by means of a relatively simple device, simultaneously to solve the problem of realizing efficient sealing of the ventilation gap, for example, at each of two op¬ posite ends, or, when necessary, about the entire cir- cumference of the gap, and to realize large inlet and outlet openings to and from the gap, respectively, when the situation requires large volumes of through-flow air. This major object has now been satisfied by means of the sealing and venting device according to the in¬ vention which is characterised by at least one elastical¬ ly deformable tubular member disposed in the ventila- tion gap and extending along at least one side of the gap; an apparatus for expanding the tubular member, by means of an expansion medium,into tight abutment ^• against the solar heat permeable and heat absorbing surfaces; and means for opening the gap for allowing the through-flow of air, these means consisting of a device for evacuating the expansion medium from the tubular member and a device for causing the tubular member to assume a substantially flattened-out state in abutment against but one of the above-mentioned surfaces.

In a preferred embodiment of the present invention, the gap is sealable and openable at two opposite sides by means of two apparatuses of the above-disclosed type. If it is desirable, in a square or rectangular solar heating element, to provide seals at all four sides of the element, tubular sealing members of the same type can be disposed in the ventilation gap along all four sides, these four members possibly being formed by sections of a single expandable tubular mem- ber. Moreover, these sections may, if desired, be ar¬ ranged such that only the two sections at the opposite ends of the. gap serve as openable venting devices as a result of evacuation of expansion medium in these latter sections. The expansion of the tubular member (or members) can, in one advantageous embodiment, be realized by air pressure. This air pressure is generated by the intermediary of water pressure by means of an elec¬ tric circulation pump which is normally used for pump- ing water in the water system in solar heating instal¬ lations. Furthermore, the apparatus for evacuating the expansion medium may comprise a normally closed evacua- 5 tion valve which is opened when the power supply to the circulation pump fails and/or when a certain water tem¬ perature is exceeded.

Advantageously, a device according to the inven- tion may also be used for converting the solar heating element so as to operate as an air heat exchanger, in which event the ventilation gap is opened at its op¬ posite ends in order to allow warm ambient air to flow through the gap -in the element, this flow possibly being positively realized by means of a fan.

According to a preferred embodiment of the present invention, expansion of the tubular members can be realized by means of air pressure in a pressure ves¬ sel in which the air pressure is generated by means of the water circulation pump by the intermediary of water pressure. In this apparatus, use may be made, for evacuation of the expansion medium, of suction which is realized in the pressure vessel on lowering of the pressure when the circulation pump ceases operat- ing, for example, in the event of a power failure.

The nature of the present invention and its aspects will be more readily understood from the following brief description of the accompanying drawings, and discussion relating thereto. In the accompanying drawings:

Fig. 1 is a fragmentary and schematic cross-sectional view showing a roof with a solar collector element in¬ tegrated in the. roof, and a device according to the pre¬ sent invention; Fig. 2 is a fragmentary longitudinal sectional view taken along the line II-II in Fig. 1;

Fig. 3 is schematic plan view of the element of Figs. 1 and 2, with a sealing device according to the invention which is disposed in the gap between the heat-permeable surface and heat-absorption surface of the solar collec¬ tor element, and of which two sections at the upper and lower ends of the gap form venting means;' and 6 Fig. 4 is a cross-section taken along the line IV-IV in Fig. 3.

Fig. 1 shows a sloping roof with a bearing surface 1 which normally consists of transverse tongued and grooved timber. A solar collector is installed on the roof 1, the collector being generally designated 2 and comprising thermal insulation 3 disposed on the roof, for example, a layer of foamed polyurethane, a heat absorbing -bed 4 resting on the thermal insula- tion 3 and being provided with a series of water chan¬ nels 5, and an outer layer 6 disposed in spaced apart relationship to the heat-absorbing bed 4 and consist¬ ing of solar energy-permeable material, such as panels of glass or translucent plastic. The entire solar collector may be mounted direct on the bearing roof structure 1 but may also be in the form of one or more cassettes, so-called solar panels which may easily be mounted on the roof surface.

Expandable tubular members 9a, 9b are disposed in a ventilation gap 8 between the heat-absorbing bed 4 and the outer layer 6, proximal the upper and lower ends of the solar collector. These members 9a, 9b may be of the same design. In the illustrated embo¬ diment, the members 9a, 9b form, at the ends of the gap 8, efficient sealing and venting devices which are in the form of hoses of rubber, plastic or other suit¬ able material. If it is considered desirable, these members may be .reinforced by fabric or the like. The hoses are-disposed such that, after expansion by means of an expansion medium, for example (or preferably) air, they form effective sealing devices between the bed 4 and the outer layer 6. By the exhausting of air and, possibly, by the generation of suction, the hoses 9a, 9b serving as venting devices can be flattened out such that they assume a substantially recumbent position against the heat-absorbing bed 4, which is illustrated by means of dot-dash lines in Fig. 1. When these hoses

:.^« _,PΪ 7 9a, 9b serving as venting devices are expanded, they form efficient sealings against air circulation through the gap 8, and when they are contracted, the gap 8 forms an open ventilation channel for natural draught (by means of so-called chimney effect) for cooling the heat-ab¬ sorbing bed 4 so that injurious heating of the bed 4 and risk of boiling the water in the channels 5 will thereby be prevented in a manner which is as simple as it is effective. According to the invention, sealing for a square or rectangular solar collector element can be realized also at the side^'s of the gap 8 by means of two further hoses 9c, 9d which extend along the outer edges of the gap 8 (see Figs. 3 and 4) . These latter hoses can be permanently expanded, since in general they need not carry out any venting function. Possibly however, these two latter hoses 9c, 9d may also be disposed to be evacuated to form vents and they can also, together with the two first hoses 9a, 9b be formed from one . continuous hose.

The hoses 9a, 9b (and possibly also the hoses 9c, 9c) may be designed such that they are normally in the form of planar, strip-formed members. Each hose may, for example, be manufactured from two 5-15 cm wide strips of plastic or rubber sheeting, for example butyl rubber, which have been vulcanized together along the edges. As was mentioned previously, the hoses are nor¬ mally filled with air in order to form efficient seals in the gap 8 between the two layers 4 and 6 when 'con- ditions are such that the greatest possible heating from the sun is desired. When the ventilation gap 8 is to be kept closed, the hoses should be under a certain excess pressure in order to realize good sealing and when the hoses 9a, 9b serving as venting devices are fully evacuated, they should lie relatively flat against the heat absorbing bed 4. It may possibly be difficult to cause the hoses 9a, 9b to assume a flat position on the bed 4 merely by reducing the air pressure. A reliable flattening-out of the hoses may be realized by rendering the hoses resiliently retractable from the expanded to the flattened position. This may be achieved by manufacturing the hoses with "elastic memory" that is to say such that they, as a result of the natural elasticity of the material and the design of the hoses, normally strive to retract to the flattened con¬ figuration, but if a relatively thin, soft sheeting is used, the hose may possibly be supplemented by spring means. Such a spring means is intimated at 10 in Fig. 1 and may consist of one or more leaf springs which, on inflation of the hose are bent from one state of curvature by the intermediary of bistable plane to an opposite state of curvature in which the spring strives tohold the hose in abutment against the under- face of the outer layer 6. On evacuation of the hose, the spring is bent back by the intermediary of the bi¬ stable plane and is curved such that it strives to hold the hose taut and in abutment against the upper face of the bed 4.

Pressure regulation of the hose 9 may be realized in several different manners. For example, it is pos¬ sible to employ an apparatus with a hand pump or pres- sure vessel and a safety valve which is opened by a temperature sensor at a certain temperature or by an electric sensor in the event of a failure of the power supply to the circulation pump which is normally used to cause the water to flow through the water channels 5. A manometer may also be used. In the event of a pres¬ sure increase in the water system caused by too high a temperature, the manometer senses this pressure change and opens the safety valve, the sealing hoses 9a, 9b serving as venting devices being emptied and opening the ventilation gap or gaps 8. After emptying, the safety valve can be closed and the hoses once again filled with air to the desired pressure. This may be 9 effected automatically when the temperature has fallen to a predetermined level.

For pressure supply, use may be made, for example, as an alternative to the above-mentioned possibilities, of a compressor, in which case the system operates in principle in the same manner as that described above, but with the difference^' tha ^'the compressor may be caused to start automatically when the temperature has fallen. It may be advantageous to use a pressure equa¬ lizer which is placed in a space having as-constant a temperature as possible, such that the pressure in the hoses is not influenced too much by the temperature in the solar collector. This is in order to reduce the risk that the -hoses 9 are compressed with far too high a pressure against the outer layer 6 in the event of strong sunshine.

According to a further alternative, the pressure in the hoses 9 may be realized by means of air pres- sure which is exercised by water against an air cushion in a vessel. The water pressure may be realized by means of that circulation pump which is normally used in solar heating systems of the above-described type. Water could also be used as the pressure medium. A solar collector system according to the invention provided with ventilation gaps 8 may, by combination with a heat pump, be used as an air heat exchanger and thereby realize an acceptable degree of self-sufficiency during a large part of the winter. Many regions during the winter experience a number of cloudy but nevertheless mild days when the solar collector system can, without appreciable modification, be used in an efficient manner. In order to realize sufficient air through-flow under these conditions, it may be necessary to install a fan as a supplement to the natural ventilation. During use of the solar collector system in combination with a- heat pump under the above-described conditions, the 10 hoses 9a, 9b serving.as venting devices are, naturally, kept in the open position in the ventilation gap 8.

In the event of a power failure, the sealing and venting device according to the invention can be evecuat- ed as a result of the impulse which the power failure provides, that is .to say a solenoid-operated valve may be used as the safety valve, in which the magnetic coil, on energization, normally holds the valve closed, where¬ as a spring opens^" the valve in the event of a power failure. By the use of electronics, the opposite mode of operation can also be achieved, that is to say such that the valve is normally kept closed when no current passes through, and such that the valve opens in the event of a failure of the power supply to the circulation pump. Figs. 3 and 4 schematically illustrate, at 11, air supply conduits which are connected to a compressed air source of the above-described type and lead to the hoses 9a-9d by the intermediary of non-return valves 12. The safety valves connected to the hoses 9a and 9b are shown at 13. Instead of non-return valves 12, use may be made of regulated valves which may be opened and closed, for example electrically, in order to permit also emptying via the air supply conduits. If a commu¬ nication line^* between the two hoses 9a, 9b serving as venting devices is provided, only one of these or only the communication line need be provided with the above- mentioned valves 12, 13. The sealing hoses 9c and 9d which, in Fig. .4, are shown as hoses of round section, may be provided with solely filling and emptying valves 14 in conjunction with air supply and evacuation con¬ duits 15. Possibly, all of the hoses may be connected to a common air supply system equipped with suitable valves.

In a solar collector system in which solar heat is transferred to air instead of to water as is shown in Figs. 1 and 2, and which, therefore, lacks the bed 4 provided with water channels, the sealing and venting 11 device according to the invention may be used in a man¬ ner similar, to that described above between the heat- permeable and heat absorbing surfaces which define an air gap for heating air by means of solar heat through the outer layer 6 in Fig. 1.

Thus, the present invention is not restricted to the embodiments shown on the drawings> but may be modi¬ fied in various ways without departing from the spirit and scope of the appended claims.

OMPI

Claims

1. Sealing and venting device in a ventilation gap (8) between an outer solar heat permeable and a heat absorbing surface (6, 4 respectively) in a solar heat¬ ing element (2) c h a r a c t e r i s e d in that the device comprises at least one elastically deformable, tubular member (9a) disposed in the ventilation gap (8) and extending along at least one side of the gap, means (11, 12) for expanding the tubular member by means of an expansion medium into tight abutment against the solar heat permeable and heat absorbing surfaces (6; 4), and means for opening the gap (8) to allow the through- flow of air, said means comprising means (11, 12 or 13) for evacuation of expansion medium from the tubular member, and means (11, 12 or 13 and/or 10) for causing the tubular member (9a) to assume a substantially flattened-out state in abutment against but one or the other of said surfaces (6,. 4) .

2. Device according to claim 1, c h a r a c t e r .i s e d in that it includes two elastically deformable, tubular members (9a, 9b) of the same type at each of two opposing sides of the gap (8) .

3. Device according to claim 2, c h a r a c t e r i s e d in that, in a square or rectangular solar heating element (2) , expandable, tubular members (9a-9d) are disposed in the- ventilation gap (8) at all four sides, of which members only the two members (9a-9b.) at said two opposing sides include said means for opening the gap (8) to allow the through-flow of air, while the other two tubular members (9c, 9d) solely form expandable seal- ing devices.

4. Device according to any one of the preceding claims, c h a r a c t e r i s e d in that the expansion means include an apparatus for realizing air pressure. generated by the intermediary of water pressure by means 13 of an electric circulation-pump.

5. Device according to claim 4, c h a r a c t e r i s¬ e d in that said means for evacuation of the expansion medium comprise a normally closed evacuation valve (12 or 13) which is operative to be opened in the event a failure of the power to the circulation pump and/or in the event of a certain water temperature -being ex¬ ceeded.

6. Device according to claim 4, c h a r a c t e r i. s- e d in that said expansion means include a pressure vessel in which the air pressure is generated by means of the water circulation pump by the intermediary of water pressure.

7. Device according to any one of claims 4-6, c h a r a c t e r i s e d in that said means for evacua¬ tion of the expansion medium comprise an apparatus for generating suction pressure.

8. Device according to claim 7, c h a r a c t e r i s- e d in that the apparatus generating suction pressure includes an air compartment in a pressure vessel which is connected to the water circulation pump, so that the air pressure is dependent upon the water pressure in the vessel.

9. Device according to claim 2, c h a r a c t e r i s- e d in that the elastically deformable members (9a, 9b) are disposed to permit conversion of the solar heating element (2) so as to operate as an air heat exchanger by opening of the ventilation gap (8) at its opposite ends in order to allow warm ambient air to flow through the gap (8), for example positively by advancing the air by means of a fan.