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Title:
SYSTEMS FOR INTERCONNECTING SOLAR COLLECTOR PLATES
Document Type and Number:
WIPO Patent Application WO/2015/025292
Kind Code:
A1
Abstract:
This invention relates to a system for interconnecting one or more solar collectors and a solar collector equipped with this system, characterised in that the system comprises a plurality of T-shaped pipes and interconnecting pipes that are connected together alternately in series in a row via a pipe-in-pipe type of connection in order to form a feed line and/or a withdrawal line for a plurality of series-connected collectors in a row.

Inventors:
FRANCKE HANS-CHRISTIAN (NO)
Application Number:
PCT/IB2014/064003
Publication Date:
February 26, 2015
Filing Date:
August 21, 2014
Export Citation:
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Assignee:
FRANCKE HANS-CHRISTIAN (NO)
International Classes:
F24J2/46; F24D11/00
Domestic Patent References:
WO2002088614A12002-11-07
WO2011089530A22011-07-28
Foreign References:
EP1512922A12005-03-09
EP1016835A22000-07-05
EP0022389A11981-01-14
US4324228A1982-04-13
GB1555485A1979-11-14
US4407269A1983-10-04
US4267822A1981-05-19
US20090013991A12009-01-15
EP0045149A11982-02-03
US4987883A1991-01-29
US4297990A1981-11-03
Other References:
DATABASE WPI Section Ch Week 201366, Derwent World Patents Index; Class A88, AN 2013-Q63721, XP002733313
DATABASE EPODOC [online] EUROPEAN PATENT OFFICE, THE HAGUE, NL; 26 May 2009 (2009-05-26), XP002733314, Database accession no. GR-20080100033-A
Attorney, Agent or Firm:
ONSAGERS AS et al. (Oslo, NO)
Download PDF:
Claims:
PATENT CLAIMS

1. A system for forming a feed line 1 or a withdrawal line 2 for thermal fluid to a series-connected row of n number of solar collectors 3 of the flat plate type, where n e { 1 , 2, 3, ... 100}, comprising:

a number of n T-shaped pipes 6 with T-shaped stub 10 adapted for connecting to the inlet 1 1 or the outlet 12 in rear plate 3, 1 13 of the collector 3; a number of n-1 interconnecting pipes 7 adapted to couple together T-shaped pipes in the feed line or the withdrawal line;

a plug pipe 8 adapted for plugging an end of a T-pipe; and

a connecting pipe 5 adapted for being connected to a T-shaped pipe, wherein

the inner diameter of the interconnecting pipe(s) 7, the plug pipe 8 and the connecting pipe 5 is adapted relative to the outer diameter of the T-shaped pipes 6 so that a tight connection can be formed by passing the end of respectively the interconnecting pipes, the plug pipe and the connecting pipe some way over the end of the adjacent T-shaped pipe;

or alternatively

the inner diameter of the T-shaped pipes 6 is adapted relative to the outer diameter of the interconnecting pipe(s) 7, the plug pipe 8 and the connecting pipe 5 so that a tight connection can be formed by passing the end of each T-shaped pipe some way over the end of respectively adjacent interconnecting pipe, plug pipe or connecting pipe.

2. A system according to claim 1, characterised in that

the system further comprises a hollow cylindrical insert 16 adapted to be passed into the T-stub 10 of the T-shaped pipe 6;

and in that

the T-stub 10 that is to be fastened to the solar collector 3 has a conical extension at the end facing the collector 3 and a threaded portion 19 on the inner wall at the opposite end of the T-stub 10;

the insert 16 has a flange 17 at one end and threads 18 on the outer wall at the other end, the threads 18 being adapted to the threaded portion 19 so as to allow them to be screwed together; and

the physical dimensions of the insert 16 are adapted such that when the insert is screwed to the T-stub 10, the flange 17 grips and clamps the rear plate 13 of the collector 3 down against the end surface of the T-stub 10 facing the collector.

3. A system according to claim 2, characterised in

that the conical extension of the T-stub 10 consists of a funnel-shaped extension of the inner diameter of the T-stub;

that the system further comprises a seal 20 located inside the funnel-shaped extension of the T-stub 10; and that the seal is dimensioned so that it will be clamped between the outer wall of the insert 16, the inner wall of the funnel-shaped extension of the T-stub 10 and the surface of the rear plate 13 that faces the T-stub 10, so as thus to form a fluid- tight seal between the insert 16, the T-stub 10 and the rear plate 13 of the solar collector.

4. A system according to claim 2, characterised in

that the conical extension of the T-stub 10 consists of a funnel-shaped extension of wall thickness of the T-stub 10;

that the system further comprises a seal 20 located between the end surface 21 of the T-stub and the surface of the rear plate 13 that faces the T-stub 10; and that the seal is dimensioned such that it is clamped between these surfaces so as thus to form a fluid-tight seal between the end surface 21 of the T-stub and the rear plate 13 of the collector.

5. A system according to claim 2 or 3, characterised in that the seal is made of a resilient fluid-resistant material selected from the group: rubber, glazier's putty, resilient joint fillers or mastic sealant.

6. A system according to claim 5, characterised in that the seal is an O-ring.

7. A system according to any one of the preceding claims, characterised in that the T-shaped pipe 6, the interconnecting pipe 7, the connecting pipe 5 and/or the plug pipe 8 are/is made of one of the following materials: plastic, polyphenylene sulfide plastic, metal, aluminium or copper.

8. A system according to any preceding claim, characterised in that:

if n = 1 and a feed line 1 is to be formed, that it is formed in that:

the connecting pipe 5 is connected to the upstream end of the T-shaped pipe 6 in the feed line, the T-stub 10 of the T-shaped pipe 6 is connected to the inlet of the solar collector 3, and the downstream end of the T-shaped pipe 6 is connected to the plug pipe 8;

or

if n = 1 and a withdrawal line 2 is to be formed, that it is formed in that:

the connecting pipe 5 is connected to the downstream end of the T-shaped pipe 6 in the withdrawal line, the T-stub 10 of the T-shaped pipe 6 is connected to the outlet of the solar collector 3, and the upstream end of the T-shaped pipe is connected to the plug pipe;

or

if n > 1 and a feed line 1 is to be formed, that it is formed in that:

- a first connecting segment in the feed line is formed in that the connecting pipe is connected to the upstream end of the first T-shaped pipe 6 in the feed line, the T-stub 10 of the first T-shaped pipe 6 is connected to the inlet of the first solar collector 3 in the series-connected row of collectors, and the downstream end of the first T-shaped pipe 6 is connected to the upstream end of the first interconnecting pipe 7 in the feed line;

- there then follows a plurality of n = n-2 intermediate segments in the feed line that are formed in that the upstream end of the nth T-shaped pipe 6 is connected to the downstream end of the nth-1 interconnecting pipe 7 in the feed line, the T-stub 10 of the nth T-shaped pipe is connected to the inlet of the nth + 1 solar collector in the series-connected row of collectors, and the downstream end of the nth T-shaped pipe 6 is connected to the nth interconnecting pipe in the feed line;

- and then there follows a final segment that is formed in that the upstream end of T-shaped pipe 6 number n=n is connected to the downstream end of interconnecting pipe number n = n-1 in the feed line, the T-stub 10 of T- shaped pipe number n=n is connected to the inlet of solar collector number n=n in the series-connected row of collectors, and the upstream end of T- shaped pipe number n=n is connected to the plug pipe 8;

or

if n > 1 and a withdrawal line 2 is to be formed, that it is formed in that:

- a first connecting segment in the withdrawal line is formed in that the plug pipe 8 is connected to the upstream end of the first T-shaped pipe 6 in the withdrawal line, the T-stub 10 of the first T-shaped pipe is connected to the outlet of the first solar collector 3 in the series-connected row of collectors, and the downstream end of the first T-shaped pipe 6 is connected to the upstream end of the first interconnecting pipe 7 in the withdrawal line;

- there then follows a plurality n=n-2 intermediate segments in the withdrawal line 2 that are formed in that the upstream end of the nth T- shaped pipe 6 is connected to the downstream end of the nth -1

interconnecting pipe 7 in the feed line, the T-stub 10 of the nth T-shaped pipe is connected to the inlet of the nth + 1 solar collector in the series- connected row of collectors, and the downstream end of the nth T-shaped pipe 6 is connected to the nth interconnecting pipe in the withdrawal line;

- and there then follows a final segment that is formed in that the upstream end of T-shaped pipe number n=n is connected to the downstream end of interconnecting pipe number n=n-l in the withdrawal line, the T-stub of T- shaped pipe number n= n is connected to the inlet of solar collector number n=n in the series-connected row of collectors, and the upstream end of T- shaped pipe number n=n is connected to the connecting pipe 5.

9. A system according to claim 8, characterised in that the system further comprises:

- a number of 2n aluminium angle sections 140;

- a number of 2 retaining rings 149a with a threaded portion; and

- a number of 2n-2 retaining rings 149b with a threaded portion,

wherein: the aluminium angle sections 140 are so configured that they have:

- a leg portion 141 for fixing to the underlying surface;

- a wall-forming part 142 oriented perpendicular to the leg portion and extending up to just below the area where the rear glass plate 1 13 of the solar collector is to be positioned, where it then divides into

- a straight back wall 143; and

- a curved section part 144 which has

- fastening zones 145 and 146 that grip and hold/clamp the ends of the glass plates 1 13 and 1 14, and 150, respectively, and

- two circular apertures 148 in the wall-forming part 142 that allow respectively a feed line and a withdrawal line according to claim 5 or 6 to pass through the wall-forming part 142;

and wherein:

- the 2n T-shaped pipes 106 have a threaded portion some way along the outer surface of the pipe at the downstream end adapted to the threaded portion on the retaining ring 149a or retaining ring 149b, and

- each of the 2n T-shaped pipes 106 have a flange 151 immediately upstream of the threaded portion.

10. A system according to claim 8, characterised in that the system further comprises:

- a number 2n aluminium angle sections 140; and

- a number 2n nuts having a threaded portion;

wherein:

the aluminium angle sections 140 are formed such that they have:

- a leg portion 141 for fixing to the underlying surface;

- a wall-forming part 142 oriented perpendicular to the leg portion and extending up to just below the area where the rear glass plate 1 13 of the solar collector is to be positioned, where it divides into

- a straight back wall 143; and

- a curved section part 144 which has

- fastening zones 145 and 146 that grip and hold/clamp respectively the ends of the glass plates 1 13 and 1 14, and 150, and

- two circular apertures 148 in the wall-forming part 142 that allow respectively a feed line and a withdrawal line according to claim 5 or 6 to pass through the wall part 142;

and wherein:

- the 2n T-shaped pipes 106 have a threaded portion some distance on the outer surface of the pipe at the downstream end adapted to the threaded portion of the nuts; and

- each of the 2n T-shaped pipes 106 have a flange 151 immediately upstream of the threaded portion.

1 1. A system according to claim 9 or 10, characterised in that each of the aluminium angle sections are equipped with a resilient pressure-relieving and sealing material 147 in the fastening zones 145 and 146.

12. A system according to any preceding claim, characterised in that the system further comprises a closed fluid circuit for liquid comprising:

- a pump 22 located downstream of the withdrawal line 2;

- a pipeline 23 for transfer of liquid from the pump 22 to a

- storage tank 24 with an air-filled expansion volume 24a and vent duct 26 connected to the expansion volume 24a;

- a pipeline 28 for transfer of liquid from the storage tank 24 to the feed line 1 ; and

- optionally an air outlet connected to the pump 22,

and where the pipeline 23 ends in the expansion volume 24b at a distance above the liquid surface in the storage tank 24.

13. A system according to claim 12, characterised in that the storage tank 24 contains a heat exchanger 25 flow-connected to a second circuit 25a, 25b for an energy-carrying liquid.

14. A system according to claim 12 or 13, characterised in that the pipeline 28 is equipped with a pump 29 that pumps liquid from the storage tank 24 to the feed line 1.

15. A system according to claim 12, 13 or 14, characterised in that the liquid is water.

16. A solar collector comprising a series-connected row of n number of collectors 3, wherein n e { 1, 2, 3 100},

characterised in that it comprises:

- a feed line 1 according to claim 1, made up as defined in claim 8;

- a withdrawal line 2 according to claim 1 , made up as defined in claim 8, and

- a system for connecting the feed line 1 and the withdrawal line 2 to the series- connected row of n solar collectors 3 as defined in any one of claims 2 to 1 1.

17. A solar collector according to claim 16, characterised in that it further comprises a closed fluid circuit for thermal fluid according to any one of claims 12 to 15.

Description:
Systems for interconnecting solar collector plates

This invention relates to a system for interconnecting one or more solar collectors and a solar collector equipped with this system.

Background

The sun irradiates the earth's surface with light which in sunny areas may constitute an energy flux of more than 1 kW/m 2 . This is a huge energy flow that can be harnessed to produce heat or be converted into other useful energy forms such as electricity, mechanical energy etc.

For households, solar heat is suitable for fully or partially meeting the hot water needs and other heating needs of the household. This can be achieved by using solar collectors, which are devices that make use of the energy in sunlight by absorbing the sunlight and transmitting the energy in the sunlight as thermal energy to an energy carrier/thermal medium (a fluid). The thermal medium may flow to a device in order to put the thermal energy to use, or to a storage tank etc. for later use in the household. In Norway it is estimated that an energy quantity of up to 400 - 450 kWh/year per m 2 of solar collector can be obtained from sunlight [1], i.e., that a few square metres of solar collector on a household roof can provide an appreciable contribution to the household's heating needs and/or hot water needs.

Prior art

Traditionally, solar heat has been used to heat up water in a tank with a dark surface standing in the hot sun. A solar collector of this kind has little thermal efficiency owing to relatively large heat losses to the collector's surroundings, and thus produces water at low temperature and low volumes of hot water. It is therefore usual to include thermal insulation of solar collectors in order to increase their thermal efficiency so as to be able supply a larger volume of hot water at a higher temperature.

A known and much used solution for thermal insulation of the solar collector is to enclose the sunlight-absorbing part of the collector in an enclosure that is essentially transparent to the relatively short-waved sunlight but essentially opaque to the relatively long-waved heat radiation from the sunlight-absorbing part of the solar collector. Thus, both convective and radiation-based heat losses to the collector's surroundings are reduced, thereby enabling the transmission of a larger portion of the collector's thermal energy production to a thermal fluid/medium that functions as energy carrier for transmission of the thermal energy to an end user site or to a thermal store for later use. The need for thermal insulation of the sunlight- absorbing part of a solar collector increases with higher temperature difference between the absorbing part and the collector's surroundings. The thermal insulation of the absorption zone in the solar collector becomes optimal by using vacuum, which reduces convective heat losses from the solar collector to almost zero. This can, for example, be achieved by using two concentric tubes, where the inner tube is the solar collector and is coated with a sunlight-absorbing surface, and the outer tube is of glass. By evacuating the outer tube (of glass) to a low gas pressure (vacuum), the convective heat transfer between the inner tube (the collector) and the insulation tube is reduced to a minimum. The thermal medium can flow on the inside of the inner tube and be heated through contact with the inner wall of the inner tube. This type of solar collector is often termed an "Evacuated Tube Batch (ETB) collector". An example of an ETB type of solar collector is disclosed in US 4 987 883. A disadvantage of ETB-type solar collectors is that they have a relatively low surface-to-volume ratio between the surface area of the sunlight-absorbing layer and the volume of the thermal medium.

Another type of solar collector intended for buildings are so-called flat plate collectors. These collectors consist of at least two congruent plates positioned in parallel and spaced apart from each other, thereby forming a relatively narrow space between the plates in which thermal fluid can flow. The plate facing the sun is often made of a material that is essentially transparent to the relatively short-waved sunlight and essentially opaque to the relatively long-waved heat radiation produced in the space between the plates, whilst the plate facing away from the sun is often made of a material that absorbs light such that the plate is heated up by incident sunlight (which has passed through the first transparent plate and the thermal fluid). Flat plate collectors have, as a rule, one or more dividing walls oriented perpendicular to the plates and disposed between the plates to divide the space between the plates and form one or more flow channels for the thermal fluid. The thermal fluid is fed to one end of the flow channel(s) via an inlet and is withdrawn at the other end of the flow channel(s) via an outlet. An example of such a flat plate type of collector is disclosed in US 4 297 990.

Flat plate collectors may be passive, i.e., that the regulation of the flow of the thermal fluid takes place by temperature-driven natural convection, or active, i.e., that the regulation of the flow of the thermal fluid takes place by forced convection.

Flat plate collectors have excellent surface-to-volume ratio between the surface area of the sunlight-absorbing parts and the volume of the thermal medium and are able to supply relatively large amounts of heated thermal fluids. A disadvantage of the flat plate collectors is that they are not as well thermally insulated as ETB-type collectors and therefore do not work as well in cold climates where the temperature difference between the sunlight-absorbing part of the solar collector and its surroundings is relatively large. This is due in part to the fact that since the thermal fluid is in contact with the first light-transparent plate, this plate will be heated up a little and thus suffer noticeable heat loss to the surrounding air. On the rear side (the side facing away from the sun), this problem can easily be solved by applying an insulating layer of some material or other, but on the front (the side facing the sun), it is imperative that the thermal insulation is able to allow the sunlight through without absorbing significant proportions of the sunlight. A solution to this problem is known from WO 201 1/089530 where a third congruent light-transparent plate is used that is placed in parallel and spaced above the second light-transparent plate. In this way, the hot part of the solar collector is insulated, i.e., the first light- transparent plate and the light-absorbing plate, including the thermal fluid, are insulated from the surroundings in that an air-filled space containing static air is formed which has an excellent thermal insulating effect between the hot part of the solar collector and the relatively cold surroundings. This is an insulation method that is analogous to the way in which double-glazing for windows works.

Another disadvantage of the flat plate collectors is that they are sensitive to changes in pressure in the space between the plates. The relatively large surface areas of the plates mean that small differences in pressure between the inner space between the plates and their surroundings result in relatively large forces of pressure perpendicular to the plates. This makes flat plate collectors particularly sensitive to temperature changes in the thermal fluid that cause large volume changes in the fluid. In periods of low load, it is conceivable that the thermal fluid may undergo excessively strong heating in periods of intense sun or, conversely, excessive cooling when it is cold outside. This can lead to problems of thermal fluids boiling in the liquid phase and, conversely, condensation of thermal fluids in gas phase or freezing of thermal fluids in liquid phase. To counter such problems it is desirable to be able to drain the thermal fluid out of the solar collector quickly in the event of such tendencies.

Clearly, costs are a key issue for solar collectors intended for consumer sale. The costs of the product need to be kept low in order to be competitive in the market.

The objects of the invention

It is an object of the present invention to provide a simple system for import and export of thermal fluid to one or more solar collectors connected in series.

It is a further object of the invention to provide a simple system for import and export of thermal fluid to one or more solar collectors connected in series, and which in addition also functions as a system for interconnecting one or more collectors of the flat plate type in series.

It is yet another object of the invention to provide a solar collector that is equipped with the system for import and export of thermal fluid. Description of the invention

The invention is based on the recognition that solar collectors connected in series can be provided with energy-carrying thermal fluid via at least one pipeline which can be assembled quickly and easily from a set of pipe sections that can be coupled together to form a pipe-in-pipe type of connection in order thus to form at least a first pipeline for the supply of thermal fluid, and that precisely the same method can be used to form at least a second pipeline for draining off thermal fluid. This constitutes a simple and inexpensive design as regards both production and assembly.

The invention thus relates to feed or withdrawal lines suitable for solar collectors series connected in a row containing any number of n collectors. In practice, this will in the majority of cases mean that n ε { 1 , 2, 3, 100} . It is also possible to assemble feed and withdrawal lines according to this invention intended for more than 100 solar collectors in a series-connected row.

In a first aspect, this invention relates to a system for forming a feed line 1 or a withdrawal line 2 for thermal fluid to a series-connected row of n number of collectors 3 of the flat plate type, where n e { 1 , 2, 3, 100}, comprising:

a number of n T-shaped pipes 6 with T-shaped stub 10 adapted for connection to the inlet 1 1 or the outlet 12 in rear plate 3, 1 13 of the solar collector 3;

a number of n-1 interconnecting pipes 7 adapted for coupling together T- shaped pipes in the feed line or the withdrawal line;

a plug pipe 8 adapted for plugging an end of a T-pipe; and

a connecting pipe 5 adapted for connecting to a T-shaped pipe,

wherein

the inner diameter of the interconnecting pipe(s) 7, the plug pipe 8 and the connecting pipe 5 is adapted in relation to the outer diameter of the T-shaped pipes 6 such that a tight connection can be formed by passing the end of, respectively, the interconnecting pipes, the plug pipe and the connecting pipe some way over the end of an adjacent T-shaped pipe;

or alternatively

the inner diameter of the T-shaped pipes 6 is adapted in relation to the outer diameter of the interconnecting pipe(s) 7, the plug pipe 8 and the connecting pipe 5 such that a tight connection can be formed by passing the end of each T-shaped pipe some way over the end of respectively adjacent interconnecting pipe, plug pipe or connecting pipe.

This system is able to form a feed line or a withdrawal line for n series-connected solar collectors by assembling the parts as follows:

if n = 1 and a feed line 1 is to be formed, that it is formed in that: the connecting pipe 5 is connected to the upstream end of the T-shaped pipe 6 in the feed line, the T-stub 10 of the T-shaped pipe 6 is connected to the inlet of the solar collector 3, and the downstream end of the T-shaped pipe 6 is connected to the plug pipe 8;

or

if n = 1 and a withdrawal line 2 is to be formed, that it is formed in that:

the connecting pipe 5 is connected to the downstream end of the T-shaped pipe 6 in the withdrawal line, the T-stub 10 of the T-shaped pipe 6 is connected to the inlet of the solar collector 3, and the upstream end of the T- shaped pipe is connected to the plug pipe;

or

if n > 1 and a feed line 1 is to be formed, that it is formed in that:

- a first connecting segment in the feed line is formed in that the connecting pipe is connected to the upstream end of the first T-shaped pipe 6 in the feed line, the T-stub 10 of the first T-shaped pipe 6 is connected to the inlet of the first solar collector 3 in the series-connected row of collectors, and the downstream end of first T-shaped pipe 6 is connected to the upstream end of the first interconnecting pipe 7 in the feed line;

- then follows a number of n = n-2 of intermediate segments in the feed line that are formed in that the upstream end of the nth T-shaped pipe 6 is connected to the downstream end of the nth-1 interconnecting pipe 7 in the feed line, the T-stub 10 of the nth T-shaped pipe is connected to the inlet of the nth+1 solar collector in the series-connected row of collectors, and the downstream end of the nth T-shaped pipe 6 is connected to the nth

interconnecting pipe in the feed line;

- and then follows a final segment that is formed in that the upstream end of T-shaped pipe 6 number n=n is connected to the downstream end of interconnecting pipe number n=n-l in the feed line, the T-stub 10 of

T-shaped pipe number n=n is connected to the inlet of solar collector number n=n in the series-connected row of collectors, and the upstream end of T- shaped pipe number n=n is connected to the plug pipe 8;

or

if n > 1 and a withdrawal line 2 is to be formed, that it is formed in that:

- a first connecting segment in the withdrawal line is formed in that the plug pipe 8 is connected to the upstream end of the first T-shaped pipe 6 in the withdrawal line, the T-stub 10 of the first T-shaped pipe is connected to the outlet of the first solar collector 3 in the series-connected row of collectors, and the downstream end of the first T-shaped pipe 6 is connected to the upstream end of the first interconnecting pipe 7 in the withdrawal line

- then follows a plurality of n= n-2 intermediate segments in the withdrawal line 2 that are formed in that the upstream end of the nth T-shaped pipe 6 is connected to the downstream end of the nth- 1 interconnecting pipe 7 in the feed line, the T-stub 10 of the nth T-shaped pipe is connected to the inlet of the nth + 1 solar collector in the series-connected row of collectors, and the downstream end of the nth T-shaped pipe 6 is connected to the nth interconnecting pipe in the withdrawal line;

- and then follows a final segment that is formed in that the upstream end of T-shaped pipe number n=n is connected to the downstream end of interconnecting pipe number n=n- 1 in the withdrawal line, the T-stub of T- shaped pipe number n=n is connected to the inlet of solar collector number n=n in the series-connected row of collectors, and the upstream end of T- shaped pipe number n=n is connected to the connecting pipe 5.

The first aspect of the invention is illustrated schematically in Figures la and lb. Figure la shows a feed line 1 designed for supplying a row of three solar collectors 3, which are marked respectively n=l , n=2 and n=3 in Figures l a and lb. The number of collectors in the figure is only meant as an illustration of the basic solution for coupling together the feed line or withdrawal line. Figure la does not show the withdrawal line 2, but from Figure lb it can be seen that it has exactly the same configuration as the feed line and that the withdrawal line 2 is mirror- symmetrical to the feed line. This permits a simplified installation of the system according to the invention in that both lines can be installed by assembling the parts in the same order and according to the same procedure, with the exception of the first and last segment. The invention also has the advantage that since the system is assembled of a plurality of identically formed segments, with the exception of the first and the last, it can easily be expanded to include more solar collectors in the row or, conversely, one or more collectors may be removed according to

modification requirements.

From Figure la or lb it can be seen that the feed line 1 consists, in this example, of a first segment (n=l) that comprises a connecting pipe 5, a T-shaped pipe 6 and an interconnecting pipe 7. The second segment (n=2) comprises a T-shaped pipe 6 and an interconnecting pipe 7, whilst the third segment (n= 3) comprises a T-shaped pipe 6 and a plug pipe 8. In this example, the outer diameter of the T-pipes 6 is slightly smaller than the inner diameter of the connecting pipe 5, the interconnecting pipes 7 and the plug pipe 8, such that the connection between the T-pipes and one of the other pipes is accomplished in that the ends of the T-pipes are inserted some way into respective pipes to which they are to be connected.

Alternatively, the diameters of the pipes could have been the other way round, allowing the connection to be made in that the T-pipes have the ends of one of the other pipes passed some way into them. Although the invention is illustrated and described with reference to the exemplary embodiment where the ends of the T- pipes are passed into the other pipes, it should be understood that the present invention includes embodiments that utilise T-pipes having a larger diameter than the connecting pipes, the interconnecting pipes and the plug pipes as described above.

Each T-shaped pipe 6 has a pipe stub 10 that is adapted to be connected to the inlet 1 1 or to the outlet of the solar collector 3. The present invention can employ any known and conceivable method in order to connect the T-pipe stub 10 to

respectively the inlet 1 1 or outlet 12 of the collector as long as the connection is sufficiently robust to prevent leakages of thermal fluid. For this reason, details concerning the sealing of this connection are not shown in Figures la and lb.

Examples of a simple and robust connection that is well suited for use with flat plate collectors, especially flat plate collectors where the plates are of glass or other fragile and breakable material, are illustrated in Figures 2a and 2b.

Similarly, the present invention can make use of any known and conceivable seal 9 for a pipe-in-pipe type of connection of pipes such as those used in the feed or withdrawal line according to this invention. However, the present invention can advantageously use a simple and robust seal that is obtained in that one of the pipes that is passed into the ends is equipped with some form of deformable projection on the outside of the end of the pipe, which provides a projection sufficiently large to be clamped between the outer wall of the inner pipe and the inner wall of the outer pipe, thereby forming a fluid-tight seal. This can, for example, be obtained by using one or more O-rings etc. In the exemplary embodiment shown in Figures la and lb, the seal 9 is obtained by using two O-rings.

The invention can utilise any known and conceivable thermal fluid, including fluids in gas phase or in liquid phase that are suitable as energy carriers for heating buildings, providing hot water for households and other low temperature uses.

Examples of suitable energy-carrying fluids include, but are not limited to, air, water, glycol, silicone oil, and any commercially available thermal fluid, provided the fluid does not undergo a phase transition in the normal operating temperature range of the collector, which in practice will be from around 0°C to around 100°C. However, uses are conceivable that will involve temperatures of the thermal fluid outside this range, such that the given temperature range should not be understood as limiting for the invention.

The pipe sections that form the feed or withdrawal line according to the invention may have any dimension and configuration as long as they are able to form the said pipe-in-pipe type of connection according to the first aspect of the invention, and as long as the feed and the withdrawal line are able to supply and withdraw sufficient amounts of thermal fluid for the solar collector(s) to work as intended. The - in this respect - suitable dimension of the pipe diameter and the configuration of the different pipe sections (connecting pipe, T-shaped pipe, interconnecting pipe and plug pipe) will depend on how large the volume flow of the thermal fluid should be and the physical dimensions and physical configuration of the solar collector(s) that are to be interconnected. Expedient magnitude of the volume flow of the thermal fluid is a function of the size of the surface area of the collector's light-absorbing parts, the number of collectors that are to be interconnected and the specific heat capacity of the thermal fluid.

Since the feed or withdrawal line according to the first aspect of the invention can be used for a highly varying number of solar collectors connected in series, and for all known types of collectors designed for low and/or medium temperature solar heat (for example, housing heating, hot water supply to households etc.), the dimensions and the physical configuration of the pipe sections in the feed or withdrawal line according to the invention may vary across a wide range. However, it is within the expected skills of a person skilled in the art to carry out such dimensioning when putting this invention into practice, and the present invention includes all known and conceivable configurations and dimensions of the pipe sections, respectively connecting pipe, T-shaped pipe, interconnecting pipe and plug pipe, capable of forming a feed line and/or a withdrawal line according to the first aspect of the invention as defined in attached claim 1.

The first aspect of the present invention can utilise any known and conceivable material that is suitable for forming fluid-carrying pipelines in the temperature ranges to which solar collectors of this type are subjected during normal operation, in practice from just above 0 °C up to 150 °C. Examples of suitable pipe materials include, but are not limited to, plastic such as polyphenylene sulfide plastic (PPS plastic) and metals such as aluminium, copper etc.

In the figures the pipe sections (connecting pipe, T-shaped pipe, interconnecting pipe and plug pipe) are shown as linear pipe sections. This is a simple and advantageous configuration for forming feed and withdrawal lines for flat plate collectors series connected in a row. However, use of linear pipe sections in exemplary embodiments of the invention should by no means be construed as limiting for this invention. Curved pipe sections, for example, could be used to form curved feed or withdrawal lines wherever appropriate, and other pipe configurations could be used wherever expedient.

The present invention is well suited for forming feed and withdrawal lines for flat plate collectors series connected in a row in that the T-shaped pipe 6 may have a relatively large inner diameter which provides relatively large transport capacity of thermal fluid at low flow resistance. This gives an advantageously good circulation of thermal fluid in the solar collector, which is particularly important in the case of flat plate collectors. As mentioned above under "Prior art", flat plate collectors consist of at least two congruent plates 13, 14 placed in parallel and spaced apart such that a relatively small space 15 is formed between the plates in which a thermal fluid (not shown in the figure) can flow. The present invention can be used for all known and conceivable flat plate collectors, including but not limited to, collectors where the rearmost plate in the flat plate collector is sunlight absorbing. Alternatively, both the rearmost and the foremost plate in the collector can be opaque to sunlight, and in that case the foremost plate will work as a sunlight- absorbing zone. Another alternative is to let both the foremost and rearmost plate be transparent and use a thermal fluid with sunlight-absorbing properties. In all alternatives, the rearmost plate of the flat plate collector will be fastened to the T- stub 10, and thus integrated with the first aspect of this invention. By the term "rearmost plate" is meant the light-absorbing plate facing away from the sun and that forms the back of the solar collector. The term "foremost plate" as used herein is the plate that is essentially transparent to sunlight and which forms the sun-facing side of the collector.

From Figures 2a and 2b it can be seen that the fastening mechanism according to a second aspect of the invention consists of a hollow cylindrical insert 16 that is passed into the T-stub 10 of the T-shaped pipe, and that the fixing of the rearmost plate 13 of the collector 3 is accomplished in that a flange 17 on the insert 16 presses the plate 13 down against the end wall of the T-stub 10. The pressure from the insert flange 17 against the rear plate 13 is maintained in that the insert 16 is equipped with threads 18 adapted to a threaded portion 19 on the inner wall of the T-stub, allowing the insert to be screwed into the T-stub with the result that the flange 17 has a firm grip on the plate 13. The coupling is made leak-tight by using an O-ring or other form of resilient material 20 that is placed between the plate 13 and the end wall of the T-stub 10, and thus becomes clamped between them. In the exemplary embodiment shown in Figure 2a, the T-stub 10 has a conical funnel- shaped extension at the end facing the rear plate 13 and the resilient seal 20 is placed in the space that is defined by the inner wall of the T-stub 10, the lower side of the rear plate 13 and the outer wall of the insert 16. In this case, the resilient seal 20 should be dimensioned so that it will be clamped between these surfaces. In the exemplary embodiment shown in Figure 2b, the T-stub 10 has a conical extension of the pipe wall up towards the rear plate such that a useful pressure face is formed at the end of the T-stub against which the resilient seal can rest. Alternatively, it is possible to use a resilient intermediate layer, a flat (with little height) resilient ring such as a jam jar sealing ring or the like clamped between the flange 17 and the upper surface of the rear plate 13 (which faces the flange). Any known and conceivable resilient material can be used that is capable of forming a leak-tight seal at the pressure points (between flange 17 and rear plate 13), fluid pressure inside the pipe duct, and the temperatures that normally occur during the operation of solar collectors of this type. Examples of suitable sealing materials include, but are not limited to, rubber rings, glazier's putty, resilient joint fillers, mastic sealant etc. In Figures 3a and 3b, the insert 16 alone is illustrated schematically from the side and from immediately above, respectively, whilst Figures 2a and 2b show examples of how the insert 16 is integrated with the feed or withdrawal line according to the second aspect of the invention. The invention may utilise any known and

conceivable material in the insert as long as the material provides the threads 18 with sufficient mechanical strength to obtain a steady and secure grip with the threaded portion 19 of the T-stub. Examples of suitable material include, but are not limited to, metals, such as aluminium, acid-proof steel, or plastic such as

polypropylene plastic or polyamide plastic etc.

Solar collectors of the flat plate type are, as mentioned, sensitive to changes in pressure inside the fluid circuit because of the relatively large surface areas in contact with the thermal fluid. A positive pressure (greater pressure inside the circuit than the ambient pressure) is generally more adverse than a negative pressure because positive pressure attempts to separate the plates 13, 14 in the collector from each other and may therefore lead to leakages of thermal fluid. It is therefore advantageous to use a pump located on the withdrawal line downstream of the solar collector(s) that draws the thermal fluid out of the collector and thus creates a negative pressure in the part of the fluid circuit located upstream of the pump.

In a third aspect of the invention, the feed or withdrawal line according to the first or second aspect of the invention comprises an outer closed circuit for thermal fluid. The closed circuit can advantageously have an insulated storage tank and the like for thermal fluid in order to provide storage capacity for solar heat, giving the user the possibility of using the solar heat independently of when the sun shines.

In cases where the thermal fluid is a liquid as, for example, water, there may, as mentioned, arise problems such as overheating or undercooling, which result in phase transition, respectively, boiling or freezing of the thermal fluid. This will result in a volume expansion which at worst can shatter the collector(s). This problem is particularly relevant in periods when the solar collector installation is inactive. Freezing temperatures or strong sun may then cause freezing or boiling problems in the fluid circuit. To remedy this problem, it is an advantage to be able to evacuate the part of the fluid circuit where the freezing or boiling problems may occur by drawing the liquid out and replacing it with air. To achieve this, the feed line can be provided upstream of the solar collector(s) with a valve, for example, a change-over valve or the like, which is activated by a regulating system that engages the valve so that it shuts off the liquid flow and opens to admit air into the fluid circuit when the installation is to be evacuated, and, conversely, which shuts off the air supply and allows the liquid to flow freely through the valve during ordinary operation of the solar collector system. In this case, the pump on the withdrawal line may advantageously be an ejector pump or a self-priming pump that is capable of evacuating air from the fluid circuit whilst ensuring that the liquid is circulated within the fluid circuit. The regulating system can be set up to regulate the operation of the pump and the valve on the basis of information about the temperature of the thermal fluid in the solar collector(s). Alternatively, the evacuation of the collector(s) is achieved by utilising a difference in water level in the pipe that returns from the collector(s) so that when the circulation stops, the pressure column will be larger on the supply side of the collector(s) and therefore the water will run back via the supply.

An exemplary embodiment of a closed fluid circuit for liquid with evacuation means is indicated schematically in Figure 4. The figure shows five flat plate collectors 3 connected in series, where a feed line 1 according to the first or second aspect of the invention conducts a relatively cold liquid into the collectors and a withdrawal line 2 according to the first or second aspect of the invention withdraws relatively hot liquid from the collectors. Downstream of the collectors 3 there is located an ejector pump 22, the task of which is to draw the liquid out of the collectors and pump it onwards via pipeline 23 into a thermally insulated storage tank 24. The inner chamber of the storage tank is divided into a liquid-filled part 24a and an air-filled 24b expansion volume above the liquid phase in order to be able to receive and hold liquid that is evacuated from the solar collectors 3. The liquid level inside the tank is illustrated by a thin broken horizontal line in the figure. As can be seen from Figure 4, the pipeline 23 ends inside the expansion volume 24b in the storage tank 24 such that liquid that is forced out of the end of the pipeline 24 must fall some distance through the air in the expansion volume before it enters the liquid phase 24a in the storage tank. The storage tank has an aperture 26 for admission or discharge of air in accordance with volume changes of the expansion zone 24b. The aperture 26 may advantageously be equipped with a stop valve (not shown) that can be opened and closed by the regulating system that operates the installation. The pump 22 has an outlet for evacuation of air (not shown) that is drawn out of the collector installation. Alternatively, the pump 22 can pump both air and liquid into the storage tank 24, and allow the necessary venting of air that is drawn out of the solar collectors (when they are put into normal operation after having been evacuated) to take place via aperture 26. From the storage tank runs a pipeline 28 that transfers relatively cold liquid from the storage tank 24 onwards into the feed line 1. This means that the fluid circuit is a closed circuit.

The pump 22 on the return line 23 creates suction in the fluid circuit upstream of the pump. In cases where liquid is used as thermal fluid, this suction may cause problems owing to the pressure dependence of the boiling point of the liquid, which may give rise to gas formation in one or more of pipeline 28, collector(s) 3 or feed line 1 if the difference in height between the storage tank 24 and the collector(s) 3, the length indicated by the arrows A in Figure 4, causes a sufficiently strong boiling point depression in the liquid. Water, for example, will boil at around 50 °C if the pressure in the fluid circuit is reduced to about 0.1 atmospheres, which is achieved in an upper part of a 9-metre high water column that is drawn up, and in the case of a 10-metre water column, the pressure in the upper part of the column is close to vacuum and here the water boils at a temperature of less than 10 °C. In many applications, it will therefore be necessary, or at least advantageous, to install a pump on the supply line 28 just downstream of the storage tank 24 which ensures that the fall in pressure from the pump 22 in neither the collector(s), the feed line or the return line falls to a level where the boiling point depression of the liquid becomes a problem. For water, the pressure in the water phase should not fall below 0.3 atmospheres in the fluid circuit, or even more advantageously 0.5 atmospheres. Figure 4b shows schematically an exemplary embodiment with a pump 29 located in the supply line 28. The operation of the pump 29 should be adjusted so that it does not raise the liquid pressure in the supply line 28 to a level where the thermal liquid is pumped actively into the feed line by the pump 29 on the supply line, but is drawn in by means of pump 22 on the return line in combination with the effect of gravity on the liquid in the liquid column of the return line. Any known and conceivable solution for regulating efficiency and operation of the pump 29 to obtain this intended effect can be utilised by the present invention.

Inasmuch as the return line in the fluid circuit (withdrawal line 2 and pipeline 23) ends at a distance above the liquid surface in the storage tank 24, the liquid height (indicated by arrows marked B in Figure 4) in the return line is less than the liquid height in the supply line which consists of the pipeline 28 and feed line 1 (indicated by arrows marked A in Figure 4). Therefore, there is a larger gravity-dependent liquid pressure in the supply line than in the return line, such that the thermal liquid can only circulate in the fluid circuit as long as the pump 22 is in operation. As soon as pump 22 stops, the difference in liquid pressure between the supply line and the return line will cause the liquid to start to flow in the opposite direction in the fluid circuit so that air is drawn in via the end of the return line (pipeline 23), which replaces the liquid in the fluid circuit until the liquid column in the supply line (pipeline 28) is the same as in the storage tank. Then the whole solar collector installation, including feed line 1 and withdrawal line 2, is emptied of liquid. This solution has the advantage that power outages or other undesired stoppage of the circulation pump results in automatic evacuation of the collectors, thereby eliminating the risk of frost or overheating problems.

Down in the liquid phase, i.e., inside the volume 24a, is located a heat exchanger 25 with external flow circuit 25a and 25b for providing one or more user sites (not shown) with solar heat via an energy-carrying thermal medium that is heated up in the heat exchanger 25. In a fourth aspect, the invention comprises a solar collector that is produced by assembling the first, second and third aspects of the invention as defined in claim 16 or 17.

List of figures

Figure la is a schematic side view of an exemplary embodiment of a feed line according to a first aspect of the invention designed for supply of thermal fluid to series-connected solar collectors.

Figure lb is a schematic top view of the same exemplary embodiment of a feed line as that shown in Figure 1 a, and of an exemplary embodiment of a withdrawal line according to a first aspect of the invention designed for the three series-connected solar collectors.

Figure 2a is a schematic side view of a first exemplary embodiment of a fastening mechanism according to a second aspect of the invention.

Figure 2b is a schematic side view of a second exemplary embodiment of a fastening mechanism according to a second aspect of the invention.

Figures 3a and 3b are respectively a schematic side view and a schematic top view of an insert according to the second aspect of the invention.

Figure 4a is a schematic diagram of an exemplary embodiment of a closed fluid circuit for liquid with evacuation means integrated with a feed and a withdrawal line according to a first, second or third aspect of the invention.

Figure 4b is a schematic diagram of the same exemplary embodiment as in Figure 4a, but which also includes a pump on the supply line for pressure support.

Figure 5a is a schematic view of an exemplary embodiment of the invention according to a third aspect of the invention designed for two series-connected solar collectors.

Figure 5b is a truncated sectional view of the exemplary embodiment shown in Figure 5a.

Figure 5c shows an exemplary embodiment of a self-evacuating fluid circuit according to the invention.

Example embodiment of the invention

The invention will be described below in greater detail with reference to an example embodiment of the invention especially suitable for supplying and withdrawing thermal fluid from series-connected solar collectors of the flat plate type that utilise transparent glass plates as, for example, shown in WO 201 1/089530.

The system according to this example embodiment utilises a feed and a withdrawal line according to the second aspect of the invention, and has in addition a simple solution for connecting the collector plates to the feed and withdrawal lines to give an integral collector unit. This is achieved by using a single aluminium section that can be utilised to fasten the glass plates in the correct position and at the same time secure the feed line and the withdrawal line to the collectors as shown in Figures 5a and 5b, where Figure 5a is a schematic side view of the exemplary embodiment, here in a version intended for connecting two collectors, and Figure 5b is a truncated sectional view of Figure 5a in order better to illustrate the aluminium section 140.

Figure 5a shows only the feed line, but as for the first and second aspect of the invention, the configuration of the withdrawal line is identical. The feed and withdrawal lines are mirror-symmetrical and are therefore made up of exactly the same parts. From Figure 5 it can be seen that this exemplary embodiment utilises the same fastening mechanism between the collector's rear plate 1 13 and the T- stubs 1 10 of the feed and withdrawal lines as shown in Figure 2a, i.e., by means of an insert 1 16 with a flange 1 17 that presses the plate 1 13 down against the T-stub 1 10.

The exemplary embodiment utilises a plurality of aluminium sections 140 which are all identically configured such that they have a leg portion 141 for fixing to the underlying surface, and a wall-forming part 142 oriented perpendicular to the leg portion and extending up to just below the area where the glass plates 1 13, 1 14 and 150 of the collector are to be fastened. At that point, the wall of the aluminium section divides into a straight back wall 143 and a curved section part 144 which has fastening zones 145 and 146 that grip and hold/clamp, respectively, the ends of the glass plates 1 13 and 1 14, and 150 in their intended position in the collector. To protect the glass plates 1 13, 1 14, 150 against breakage, it can be advantageous to use a resilient pressure-relieving and sealing material 147 in the fastening zones 145 and 146. In the lower part of the wall portion 142 leg portion there is a circular aperture 148 (not shown in Figure 5b) where the feed line is to be formed, and a corresponding circular aperture where the withdrawal line is to be formed.

As shown in Figure 5a, a simultaneous connection of pipe sections in the feed and withdrawal lines and the collector plates is achieved in that a first aluminium section 140 (counting from the upstream end) has a T-pipe 106 with a flange 151 passed through aperture 148 such that the flange 156 is on the downstream side of the wall portion 142. On the upstream side of the wall portion 142 the connecting pipe 105 is fastened to the T-pipe 106 by means of a retaining ring 149a which both fastens the connecting pipe 105 to the T-shaped pipe 106 and clamps the wall part 142 between the flange 151 and the retaining ring 149a. At the downstream end of the first collector, a connecting pipe 107 that is fastened to the downstream end of a first T-pipe 106 is passed through aperture 148 in a second aluminium section. The retaining ring 149a and the fastening zone of the T-pipe 106 are threaded so as to allow them to be screwed together. A third aluminium section is positioned such that it is locked securely to a second T-shaped pipe 106 in that it is clamped between the T-pipe's flange 151 and a retaining ring 149b which also acts to lock together the downstream end of the interconnecting pipe 107 and the upstream end of the second T-shaped pipe 106. Here too, the fastening of the retaining ring 149b to the T-shaped pipe 106 is obtained by threads which allow them to be screwed together. The second and third aluminium sections are mirror-inverted and stand end to end with the back walls 143 facing each other. At the downstream end of a second collector is located a fourth aluminium section which secures the

downstream end of the glass plates of the second collector. Alternatively, the clamping rings 149a and 149b can be replaced by nuts that are screwed firmly into the threaded portion in the T-pipes 106 and allow the nuts to perform the locking of the wall parts 142 against the flange 151. In this case, the T-pipe 106 is able achieve a fluid-tight connection with respectively the connecting pipes 105 and the interconnecting pipes 107 by the same pipe-in-pipe type of connection as shown in Figure la.

This configuration of the feed line and a corresponding mirror-inverted configuration of the withdrawal line (not shown in the figures) allows the formation of a reciprocally locked structure which entails that the first and second aluminium section for each collector are facing each other and are locked spaced apart from each other, which causes the fastening zones 145 and 146, including the resilient pressure-relieving and sealing material 147, to exert a clamping pressure against the end surfaces of the glass plates 1 13, 1 14 and 150 so that they are held in place, whilst a fluid-tight seal is formed along the end edges of the glass plates. A locking of each collector to each other in the row is achieved in that the back wall 143 of the first aluminium section of collector number n+1 in the row of n collectors buts against and clamps onto the back wall 143 of the second aluminium section of collector number n in the row.

Inasmuch as first and second aluminium angle sections of each solar collector are mirror symmetrical (i.e., are two versions of the same section oriented 180° relative to each other), the exemplary embodiment according to the third aspect of the invention forms a simple system for interconnecting a number of n series-connected collectors of the flat plate type which essentially comprise a number of 2n aluminium angle sections 140, n glass plates 1 13 (coated with a sunlight-absorbing layer), n glass plates 1 14, n glass plates 150, 2n T-shaped pipes 106 with n retaining rings 149b, 2n-2 interconnecting pipes 107, 2 plug pipes 108 and 2 connecting pipes 105, including 2 retaining rings 149a.

The outer glass panel 150 can advantageously be glued to the aluminium angle sections 140 so that they constitute a structural reinforcement of the construction and a visual enhancement in that the glass lies flush with the outermost body of the structure.

This exemplary embodiment is integrated with a self-evacuating liquid circuit as shown in Figure 5c. During ordinary operation, pump 31 ensures that water is drawn out of the storage tank 24 and into ejector pump 22 that is located downstream of the withdrawal line 2. From ejector pump 22 runs a pipeline 23 that ends inside the expansion volume 24b of the storage tank some way above the water surface. The storage tank has an air drainage pipe 26 for evacuating or filling air in accordance with volume changes of the expansion volume 24b. From the storage tank 24 runs a pipeline 28 equipped with circulation pump 29 which sends liquid into the feed line 1. When pump 29 and 31 are stopped, the pressure of the liquid column in the supply line (pipeline 23 and feed line 1) will ensure that the liquid starts to flow in the opposite direction, such that the liquid is replaced with air (which enters via the end of the pipeline 23).

Reference:

1. Store Norske Leksikon 2005-2007, web edition

http://snl.no/solfanger/energiteknikk