WO2010076784A2

WO2010076784A2 - Solar heating apparatus

Info

Publication number: WO2010076784A2
Application number: PCT/IL2009/001217
Authority: WO
Inventors: Uri Saar; Dvir Brand
Original assignee: Ziv-Av Engineering
Priority date: 2008-12-31
Filing date: 2009-12-27
Publication date: 2010-07-08
Also published as: WO2010076784A3

Abstract

A solar heating apparatus comprising: a first longitudinal space for holding water; a second longitudinal space for allowing upwardly flow of water being heated, located parallel to the first longitudinal space and substantially thermally separated therebfrom; passage means for allowing flow of water from the bottom portion of the first longitudinal space, to the second longitudinal space and heated water from the second longitudinal space to the top portion of the first longitudinal space, wherein the first longitudinal space equivalent cross section is substantially larger than that of the second longitudinal space, wherein the two longitudinal spaces are integral portions of the solar heating apparatus, and wherein the apparatus is adapted to be installed so that the second longitudinal space is located at a side that would be heated up by incident solar radiation absorbed by a solar collecting plate, thereby heating of water flowing through that second longitudinal space.

Description

SOLAR HEATING APPARATUS

Field of the Invention

The present invention generally relates to solar energy collection and is particularly directed towards improved solar collectors having increased thermal collecting efficiency.

Background of the Invention

Conventionally, the supply of hot water for domestic use has been fulfilled by boilers where water was electrically heated or by using other sources of energy such as solar energy, etc. to heat water containing boilers. These boilers are typically provided with thermal insulation to reduce heat losses to the ambient. Conventional solar heating systems are generally composed of three major components: solar thermal collectors which are typically collecting plates used for absorbing radiant solar heat, a fluid system used to convey the usable heat absorbed by the solar thermal collector and typically comprises a plurality of pipes arranged in an array fastened to the surface of the collector plate, thereby allowing the transport of the fluid that conducts the absorbed energy, and a reservoir or tank used for storage and enabling subsequent use of the heated fluid. Such systems are used to heat water for a wide variety of uses, including domestic, business and industrial uses.

It is therefore desirable to increase the thermal efficiency of such heaters, which depends primarily upon the collection of solar energy and the transfer efficiency of heat collected by the solar collector, into the fluid via heat conduction mechanism.

Most solar collector panels that are presently being manufactured are not optimally efficient in conducting heat from the collector plate to the fluid. Typically the sheet stock for the collector plate is shaped to form semicircular channels into which the pipes are fitted. One problem associated with such configuration is the relatively too small area of the pipes that are in direct contact with the collector plate, to allow efficient transfer of heat by conduction. Secondly, because of manufacturing requirements, the sheet stock that is used is usually too thin to provide good lateral heat transfer from all parts of the collector plate to the pipes, thereby greatly reducing the operating efficiency. Also, machine forming of semicircular channels usually cannot be accomplished to the accuracy required for the close mating contact with the pipes, which even further decreases the efficiency of the heat transfer.

In addition, such a solar system comprises a water tank that holds the heated water (being the typical fluid used to absorb the incident solar radiation) . The tank is typically positioned higher than the solar unit, allowing the heated water to circulate due to the small difference existing in specific gravity between cold and hot water, but can also be located lower than the solar unit, if artificial water circulation is forced by a pump.

Some attempts were made in the art to try and solve at least some of the above drawbacks. CN 101158513 discloses a solar energy absorber that consists of the circular pipes which are arranged on the same surface and connected with each other by fins, an upper cover plate, a lower support plate and a member which consists of the side plates sealed at two sides, and is made of the transparent materials and the fins are connected with the circular pipes at the surrounding of the upper cover plate. A solar energy heat collecting layer is arranged on the internal wall of the circular pipe and a reflective layer is arranged at the bottom of the lower support plate. However, in order for such a design to operate while achieving improvement in solar absorption efficiency, the absorber should be made by using transparent material, which of course has its own drawbacks .

US 4452231 describes a solar water heating apparatus that comprises a plurality of longitudinal tubular storage tanks positioned adjacent one another in a stacked array. Each tank is aligned adjacent the next tank in the same direction and plane. A cold water inlet pipe is directed through coaxial apertures near the bottom of each tank while a hot water outlet pipe is directed through aligned apertures near the top of each tank. Each tank in the array is associated with a heat conducting plate with each plate having a pipe thermally connected thereto. The pipe enters the associated tank at the bottom end through a first opening and enters at the top end through a second opening. When cold water is directed through the cold water inlet pipe, it enters the pipe associated with the plate. As the solar energy impinges on the plate, the water is heated and the thermo siphon effect causes the water to rise through the pipe towards the top opening. When a particular pressure is reached due to temperature a valve at the top end will pivot and open to allow the heated water to continue to circulate until the entire temperature of the storage tank reaches an ambient value. Still, this publication does not offer the flexibility reguired in manufacturing and installing solar heating systems, to the extent that a substantial reduction in their cost may be achieved, and suffers from similar disadvantages as described hereinbefore.

While many configurations of solar heating systems have been designed and installed, the cost of these systems still prevents many potential users from buying and using them.

Summary of the Invention

It is therefore an object of the present invention to provide a solar heating system that is significantly less expensive to manufacture than currently available systems.

It is another object of the present invention to provide a solar heating system which is a modular apparatus/system. It is still another object of the present invention provide a solar heating apparatus that can easily be installed.

It is yet another object of the present invention to provide a solar heating apparatus that is flexible and may be installed in different configurations.

Other objects of the invention will become apparent as the description of the invention proceeds.

Thus, in accordance with a first embodiment of the present invention there is provided a solar heating apparatus which comprises: at least one first longitudinal space adapted to hold water; at least one second longitudinal space adapted to allow upwardly flow of water being heated therethrough, located substantially parallel to the at least one first longitudinal space and being thermally substantially separated therefrom; a first passage means adapted to allow flow of water from the bottom portion of the at least one first longitudinal space and/or of the solar heating apparatus, to the at least one second longitudinal space; a second passage means adapted to allow flow of heated water from the at least one second longitudinal space to the top portion of the at least one first longitudinal space and/or of the solar heating apparatus; wherein the at least one first longitudinal space cross section is substantially larger than the at least one second longitudinal space cross section; wherein both the at least one first longitudinal space and the at least one second longitudinal space are integral portions of the solar heating apparatus; and wherein the solar heating apparatus is adapted to be installed in a way that the at least one second longitudinal space is located to face a solar radiation source thereby enabling heating of water flowing through that at least one second longitudinal space by solar radiation absorbed at the wall confining the at least one second longitudinal space.

As will be appreciated by those skilled in the art, although there are two passage means connecting between the first longitudinal space and the second longitudinal space (s) , for the purpose of describing the present invention these first longitudinal space and second longitudinal space (s) are referred to as being substantially thermally separated from each other.

According to another preferred embodiment of the invention, both the at least one first longitudinal space and the at least one second longitudinal space are integral portions of the solar heating apparatus.

In accordance with another preferred embodiment, the solar heating apparatus further comprises at least one bottom portion, adapted to enclose the bottom of the respective at least one first longitudinal space and of the respective at least one second longitudinal space, wherein each of the at least one bottom portion is provided with a cold water ingress to allow introduction of cold water into the respective at least one first longitudinal space and/or the respective at least one second longitudinal space.

According to yet another preferred embodiment, the solar heating apparatus further comprises at least one top portion, adapted to enclose the top of the respective at least one first longitudinal space and of the respective at least one second longitudinal space, wherein each of the at least one top portion is provided with a hot water egress to allow withdrawal of hot water from the respective at least one first longitudinal space and/or the respective at least one second longitudinal space, cording to yet another preferred embodiment of the invention, the solar heating apparatus further comprises an internal insulation layer adapted to further separate the at least one first longitudinal space from the at least one second longitudinal space. Preferably, the insulation layer is installed internally (i.e. within the solar heating apparatus itself) , and covers substantially the wall of the at least one first longitudinal space, and optionally other internal surfaces such the internal surface of the covers .

In accordance with still another preferred embodiment, the solar heating apparatus is further adapted to receive an outer transparent cover while leaving an air gap between that outer transparent cover and the external wall of the at least one second longitudinal space. This transparent cover is operative to allow substantial part of the incident solar radiation to reach the external wall of the at least one second longitudinal space, and at the same time to reduce heat losses from that heated external wall due to heat transfer by convection and conduction mechanisms .

According to another embodiment of the present invention, the solar heating apparatus further comprises means to enable its connection to at least one other adjacent solar heating apparatus. By this embodiment, the solar heating apparatus may be installed at various configurations, where each solar heating apparatus is modularly connected to at least one other solar heating apparatus. The solar heating apparatus may be connected to such a neighbor solar heating apparatus in parallel and/or in series, and as will be appreciated by those skilled in the art, the connection of the various solar heating apparatus to form a final array configuration may either take place at the plant/assembly shop or preferably on site. Preferably, each of the at least one top portion and the at least one bottom portion is further adapted to be dismantled from solar heating apparatus at the site where the solar heating device is installed. Thus, when two solar heating apparatus should be connected in series, one on top of the other, the required result may be achieved by taking off the bottom portion of the apparatus that will be the top apparatus of this combination and the top portion of the apparatus that will be the bottom apparatus of the combination, and then connecting the two together while using appropriate adaptors.

By yet another embodiment of the present invention the first passage means and/or the second passage means comprises an orifice to enable conveying of water therethrough .

According to another preferred embodiment of the invention the solar heating apparatus is a product of an extrusion process. Having the solar heating apparatus made in an extrusion process, results in a number of advantages. The main advantages are: first, the at least one first longitudinal space and the at least one second longitudinal space and possibly any one of the following: the solar radiation collecting plate, the air gap enclosure and the means to fix the transparent cover to its place, are comprised within a single integral unit with no need for welding, sealing etc. Secondly, the solar heating apparatus can be made of any desired length that would still be practical for installation, and thirdly, the price of such a manufactured solar heating apparatus is reduced substantially, as compared with non-extrudable devices. Preferably, the solar heating apparatus further comprises at least one member of the group consisting of: a solar radiation collecting plate, means for fix a transparent cover in front of said at least one second longitudinal space, and an air gap enclosure, wherein that at least one member constitutes an integral part of the solar heating apparatus, and is manufactured by that extrusion process together with the remaining parts of the solar heating device.

In accordance with still another embodiment of the invention, the solar water heating apparatus further comprises a heat conductive plate, of which at least a substantial part is adapted to be subjected to solar radiation, i.e. when the heating apparatus is installed, the heat conductive plate would face the incident solar radiation. Preferably, that heat conductive plate is an integral part of the solar water heating apparatus itself.

Brief Description of the Drawings

For a more complete understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic view of a vertical cross section of a solar radiation collecting apparatus constructed in accordance with an embodiment of the present invention; FIG. 2 illustrates a horizontal cross section of the solar heating apparatus of FIG. 1;

FIGs. 3A-3C show modular configurations according to certain embodiments of the present invention; FIG. 4 illustrates an additional configuration of an embodiment of the present invention apparatus; FIGs. 5A-5C show details of a preferred embodiment of the present invention; and

FIG. 6 shows an array of several tanks interconnected to each other in parallel.

Detailed Description of Preferred Embodiments

A better understanding of the present invention is obtained when considering the following non-limiting detailed examples taken in conjunction with the drawings.

Some of the objects of the present invention are to provide a solar water heating apparatus that is inexpensive to manufacture, flexible in installation, may be delivered in a very broad range of sizes, and is built in a way that makes recycling of its components very economic.

An array of solar heating apparatus of the present invention typically comprises a number of solar heating apparatus having a cross section in the shape of a circle, and ellipse, a polygon, and the like and any combination thereof, preferably manufactured in a process of extruding aluminum. However, it should be noted that while aluminum is the most popular metal for extrusion, the present invention is not limited to the material that the apparatus or some of its parts are made of. The array comprises a number of these solar heating apparatus

(although even one apparatus may be used for the purpose) where each of them is connected to at least one of its neighbors in a modular fashion. Each of the solar heating apparatus comprises at least one first longitudinal space for holding water and one or more much narrower second longitudinal spaces (e.g. cavities, tubes, etc.) through which the flowing water is being heated. In a typical apparatus of the invention, the base of the apparatus is bolted to the body, and comprises an orifice that connects between the tubes (the second longitudinal spaces) and the water storage tank (the first longitudinal space) , as well as an intake port to enable feeding the apparatus with fresh cold water. The top cover is also typically bolted to the body, and comprises an orifice connecting between the tubes and the water storage space, as well as an output port to enable conveying heated water from the apparatus towards the consumer. As will be appreciated by those skilled in the art, although an apparatus having a single body and terminated with a single base cover and a single top cover is a simple configuration of the present invention, still, alternative configurations can be constructed, as will be described hereinafter.

Turning now to FIG. 1, this FIG. illustrates a schematic view of apparatus 20 constructed according to the present invention. The apparatus body 20 is made of extruded aluminum and extends from top line 24 to bottom line 26. The extruding direction of this element is vertical, so that all horizontal cross sections of the body are substantially identical to each other. In this example, body 20 is tightly covered by a top cover 22 and a base cover 28. Upon assembling the apparatus (body 20 and the two covers 22 and 28) a closed volume is formed which may be filled with water. Within this volume there are included water storage volume 32, bottom tunnel 42 and top tunnel 40 (these two bottom and/or top tunnels are preferably not made as part of the extrusion process itself), as well as one or more cavities 34. All these parts are preferably integral parts of the extruded body, and are form during the extrusion process. In addition, several other parts may be fitted to apparatus. For example, an isolation sleeve 36 may be inserted prior to assembling the apparatus into body 20, so as to separate between the water contained in storage volume 32 and the metal wall of body 20. Also, a transparent cover 50, typically made of glass, polycarbonate or any other applicable material, may preferably be inserted in groves 46 and 48 during assembly, and may also be supported by vertical groves located along the body (not shown in this FIG.), thereby reducing heat loss from the apparatus face 52 which is being heated by the solar radiation, to the environment. If required, the space embodied by the apparatus face 52 and transparent cover 50 may be sealed and evacuated in order to achieve substantially reduced heat losses, but of course this embodiment is applicable only when conditions are such that would justify such a configuration.

Fresh water is supplied to the apparatus via input manifold 44 at the bottom portion, while hot water is withdrawn from the apparatus via output manifold 38 located at the top portion of the apparatus . When installed, the apparatus is installed so that the apparatus side that comprises cavity 34 would face the sun. Thus, the solar radiation will hit side wall 52 of apparatus 10 which is in fact the side of cavity 34, and the heated side wall 52 will heat the water located within cavity 34. The heated water become lighter than the rest of the water in the apparatus and makes its way up along the cavity space towards top cover 22. When the heated water enters top cover 22, it flows through cover tunnel 40 to the top of the water tank while allowing cold water to enter the bottom of cavity 34 while being withdrawn from the bottom of the water storage tank 32 through bottom tunnel 42 of bottom cover 28. Such water cycle of water is repeated, and as long as water is not withdrawn from the top of the apparatus, the total volume of water is getting hotter with every such cycle. When hot water is consumed through top manifold 38, fresh cold water enters the apparatus through bottom manifold 44.

FIG. 2 illustrates a horizontal cross section 60 made through an apparatus constructed in accordance with the present invention. The apparatus whose cross section is illustrated in this FIG., comprises an elongated member

(i.e. a tank) 62, three cavities, 68 (which are external to the walls of tank 62) , transparent cover holders 66 and 72 and a heat collecting plate 74 which is used for further increasing the collection efficiency of solar radiation. Tank 62 is fitted in this example with an insulation sleeve 63, such as expanded polyurethane, expanded polystyrene, expanded polypropylene and the like, that is thick enough to efficiently prevent substantial heat losses from the heated water at the tank inner space 64, to the tank's wall (typically an insulation layer of about 3 cm thick) . Three cavities 68 are shown in this FIG. (as opposed to the example of FIG. 1 where only one central cavity tube is demonstrated) . The cavities may be of any shape/cross section and any applicable number of cavities may be used. All these cavities are used for circulating upwardly the water being heating by the solar radiation. Transparent cover 70 is sled into the grooves comprised in transparent cover holders 72 and 66 before the base and the cover are tightly attached to the body, so that the transparent cover is supported from all four sides - bottom (the base), top (the cover) and sides. When installed, the apparatus will be mounted in a way that heat collecting plate 74 will face the solar source behind the transparent cover, to enable the absorption of radiation energy at the whole surface of plate 74. Once the plate starts to heat, the energy is conveyed towards the contact area with the cavities, and as the cavities themselves will always be cooler than the solar heating panel as long as there is direct solar radiation that reaches the plate and as long as water is circulating through these cavities. Thus, the cavities act in fact as heat sinks and the energy absorbed by the solar heating plate would be conducted towards these cavities. In other words, heat will be conducted from the various areas of the plate towards the cavities' walls and from there will be conducted through the walls to the water flowing within.

FIGS. 3A, 3B and 3C illustrate three different sizes of a water tank that can be manufactured while using the same tooling in the factory. FIG. 3A shows the same configuration as was described in FIG. 1, and is shown here mainly for the purpose of serving as a scale for the other two examples. FIG. 3B illustrates a larger apparatus, where body 71 is made by the same machine that makes the body illustrated in FIG. 3A, with the only difference that the body is cut to a different size (longer) , while the base and the cover are the same as those of the FIG. 3A example. This example demonstrates a meaningful advantage of the present invention, as the apparatus may be offered in a practically unlimited size of apparatus with no real effort to be invested on the manufacturing side, as the same tooling is used. The apparatus simply comprises the typically long extruded metal body and standard top and bottom covers.

FIG. 3C illustrates an embodiment of an even greater level of modularity, where apparatus of different volumes may be assembled in the field. A number of standard elongated members 72 are coupled to each other (two in this example) thereby creating a member that is twice as long as the standard member. A fitting module 73, having the same internal structure as the body, but comprising two bands configured to tightly couple two bodies to each other, is used to interconnect the body parts to each other. A standard base and cover are used to terminate the apparatus and connect it to the cold and hot water supply, respectively. By this embodiment, when there is a need for a substantially bigger capacity of heated water, the final apparatus may be brought to the field in small units that can be transported easily (e.g. while using domestic elevators, staircases and through normal doors) . The lighter weight and the smaller size of the elements make this apparatus unique in its simplicity handling, installing and repair services.

In both configurations shown in FIGs. 3B and 3C, the transparent cover that reduces heat losses should preferably be a single piece that will be cut to the right final size. In the alternative, for the assembly illustrated in FIG 3C, two transparent covers may be used, each associated with a respective body. Similarly, two insulation layers may be used, each with its respective body.

FIG. 4 demonstrates an example of assembling of four elongated devices 92 into a two dimensional system, having a substantially larger solar collection area. The bottoms of the two lower bodies are connected to a common bottom cover (base) 98 comprising two orifices each of which is the same as in bottom cover (base) 28 of FIG. 1, to serve both bodies. Base 98 also serves to feed in the water via input pipe 102. Similarly, the two top bodies are connected to a common top cover 100 that is built to have the same structure as top cover 22 of FIG. 1, with two orifices serving as outlets for two bodies. Pipe 96 is used to convey the heated water away from this solar heater. Two couplers 94 are used to connect the two lower bodies to the two upper bodies, in a way similar to the connection of bodies 72 by coupler 73, as illustrated in FIG. 3C. The space formed between the four 92 bodies may be used to increase the amount of collectable heat. In this example, a solar heating plate 90, such as a solid metal plate or a structure built utilizing a greenhouse effect, is preferably conductively connected to the cavities of the four bodies. In this example, edge 104 of plate 90 is in contact with the external walls of the cavities so that heat collected by the plate is conductively conveyed into the water flowing therein and contributes to the heating process. Furthermore, in this example, the cavities are heated both by direct radiation and by heat conducted. The back side of the heated plate is isolated to avoid thermal energy loss to the surrounding environment.

Water is introduced into system via pipe 102, and then is divided in the bottom cover 98 into two pipes each associated with one of the two lower bodies. The solar heating of water in the respective cavities causes the water to move upwardly, in both sides. The heated water flows from the lower cavities to the upper cavities and then to top cover 100. The system of this example is positioned so that the top cover 100 is substantially higher than the bottom cover 98. Hot water may be extracted from the system via output pipe 96.

Next, let us consider FIGS. 5A - 5D, illustrating possible configurations of apparatus according to certain embodiments of the present invention. As shown in FIG. 5A, apparatus 110 comprises an elongated member 83 in the form of a tubular vessel having a fixed cross section, which is typically made of extruded material. This elongated member is adapted to be filled with heated liquid 200 and is isolated from its surrounding by means of internal insulation layer 130. The vessel is covered by means of a top end cover 67 and a bottom end cover 65. Both top and bottom end covers are preferably also internally insulated by insulation layers 120 and 140, respectively. Bottom end cover 65 comprises ingress port 76 through which cold water enter the vessel while top end cover includes an egress port 75 through which the heated water leaves the vessel.

Apparatus 110 further comprising a duct 220 (a cavity) which extends along a substantial part of the main tubular vessel 83, at which the flowing water will be heated by the incident solar radiation. The front plane of the duct 220 is a part of solar energy collecting panel 270 which absorbs the solar radiation and conducts the absorbed energy so that a substantial part thereof may eventually be absorbed by the water running through the duct. Cold water enters the duct 220 via an orifice 240 located at the bottom end cover 65, heated and consequently is pushed upwardly, to eventually exit the duct via a similar orifice 230 located at the top end cover 60. In order to gain increased energy collection efficiency with minimum losses to the environment, the absorption panel 270 is isolated by means of an air gap 300 and a front transparent material 99 that provides good isolation, yet enables most of the solar radiation to pass through. In certain cases, the air trapped in gap 300 may be evacuated in order to achieve further reduced heat losses . As long as the temperature of the solar energy collecting panel 270 temperature is higher than that of the water flowing in the duct 220, heat will be conducted to the water and resulting in continuing the circulation of cold water entering the bottom orifice, heated and leaving the duct through the top orifice. As long as no water is withdrawn from apparatus 110, the water leaving the top orifice will occupy the top layer of the water comprised in the tubular vessel, and eventually increasing the temperature of the full volume of water contained in the apparatus .

FIGS. 5B-5D illustrating different enlarged views of three portions of the apparatus illustrated in FIG. 5A.

FIG. 6 demonstrates a way of using the modularity of the apparatus of the present invention, and shows an array of vessels where each elongated member is attached to its adjacent neighbor (or two neighbors as the case may be) . Having such design flexibility, enables the installing of a number of apparatus in many different configurations, including different sizes of cross sections and lengths, arrays of units located side by side or in series so as one extends the previous one, etc. As the apparatus is preferably connected to its neighbor in any of the possible ways through the cover portions, systems comprising each a number of apparatus are easily installed and may be field upgradeable, resulting with the desired volume of heated water and/or the desired shape/footprint.

As will be appreciated by those skilled in the art, the above description includes only some embodiments of the apparatus for collecting solar radiation, and serves for its illustration. It should be understood that a number of other ways of carrying out the present invention may be devised by a person skilled in the art without departing from the scope of the invention, and are thus encompassed by the present invention.

The present invention has been described using non- limiting preferred embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. Variations of embodiments described will occur to persons of the art. Furthermore, the terms "comprise", "include", "have" and their conjugates, shall mean, when used in the claims, "including but not necessarily limited to." The scope of the invention is limited only by the following claims:

Claims

1. A solar heating apparatus which comprises: at least one first longitudinal space adapted to hold water; at least one second longitudinal space adapted to allow upwardly flow of water being heated therethrough, located substantially parallel to said at least one first longitudinal space and being thermally substantially separated therefrom; a first passage means adapted to allow flow of water from the bottom portion of the at least one first longitudinal space and/or of the solar heating apparatus, to said at least one second longitudinal space, a second passage means adapted to allow flow of heated water from said at least one second longitudinal space to the top portion of the at least one first longitudinal space and/or of the solar heating apparatus, wherein said at least one first longitudinal space cross section is substantially larger than the at least one second longitudinal space cross section; wherein both said at least one first longitudinal space and said at least one second longitudinal space are integral portions of said solar heating apparatus; and wherein the solar heating apparatus is adapted to be installed in a way that the at least one second longitudinal space is located at a side that would face a solar radiation source thereby enabling to heat water flowing through that at least one second longitudinal space by collected solar radiation.

2. A solar heating apparatus according to claim 1, being a product of an extrusion process.

3. A solar heating apparatus according to claim 1, further comprising at least one bottom portion, adapted to enclose the bottom of a respective at least one first longitudinal space and of a respective at least one second longitudinal space, wherein each of said at least one bottom portion is provided with a cold water ingress to allow introduction of cold water into said respective at least one first longitudinal space and/or said respective at least one second longitudinal space.

4. A solar heating apparatus according to claim 1, further comprising at least one top portion, adapted to enclose the top of a respective at least one first longitudinal space and of a respective at least one second longitudinal space, wherein each of said at least one top portion is provided with a hot water egress to allow withdrawal of hot water from said respective at least one first longitudinal space and/or said respective at least one second longitudinal space.

5. A solar heating apparatus according to claim 1, further comprising an internal insulation layer adapted to further separate the at least one first longitudinal space from the at least one second longitudinal space.

6. A solar heating apparatus according to claim 1, further adapted to receive an outer transparent cover.

7. A solar heating apparatus according to claim 1, further comprising means to enable its connection to at least one other adjacent solar heating apparatus.

8. A solar heating apparatus according to claim 1, wherein each of said first passage means and/or said second passage means comprises an orifice to enable conveying of water therethrough.

9. A solar heating apparatus according to claim 2, further . comprising at least one member of the group consisting of: a solar radiation collecting plate, means for fix a transparent cover in front of said at least one second longitudinal space, and an air gap enclosure, which constitutes an integral part of said solar heating apparatus, and manufactured by said extrusion process.

10. A solar heating apparatus according to claim 1, further comprising a heat conductive plate, of which at least a substantial part is adapted to be subjected to solar radiation.