TECHNICAL FIELD

The invention relates to a light absorbing unit according to the preamble of claim 1.

BACKGROUND ART

Light absorbing units are available in numerous designs where a liquid medium such as water or a gaseous medium such as air is heated by light radiation from the sun. One advantage of a hydronic system compared to an airborne system is i.a. that it is easier to connect this to an already existing hydronic system as opposed to interchange between an airborne and a hydronic system. Liquid is further more energy dense than air whereby higher efficiency is achieved if the interchange between air and water can be avoided.

A variant of a light absorbing unit is a so-called flat plate collector - a box-like structure with an outer glass sheet which allows the passing through of light radiation, and a liquid medium is circulated in a pipe system in an essentially closed space underneath the glass sheet, whereby the medium is heated by the said light radiation.

Such units are intended to be stationary placed on house walls/roofs whereby the heated medium for example can be used to heat the air in the building or for producing hot tap water.

FR2499693A1 shows a light absorbing unit for heating, via a transparent surface layer, of a liquid medium by means of solar energy, comprising a channel configuration in the form of tubes inside said transparent surface layer in which said liquid medium is arranged to flow for the heating, wherein light absorbing means in the form of upper and lower sheets providing thermal contact are present, which are formed according to and surrounding the tubes. The unit further comprises an inner transparent layer to thermally insulate said channel configuration for said liquid medium against the ambient air. The light absorbing unit is intended to be an integral part of a roof structure. The light absorbing unit is arranged to support roof tiles. DE4323270A1 shows a solar collector of a hybrid type. To arrange solar cell elements only at the longitudinal sides of the solar collector provides only a limited amount of electricity from the solar cell elements. In DE4323270A1 is suggested that a full-scale coating of the top side should be possible if semi- transparent solar cell elements are used. However, semi-transparent solar cell elements are sensitive to moisture. Since the solar cell elements in the device of DE4323270A1 are in contact with the internal space of the solar collector, moisture can access the solar cell elements which will shorten their service life. The vacuum system in DE4323270A1 can to some extent prevent the moisture, but it is not possible to maintain a tight vacuum system without regular maintenance, which requires that the solar collector is arranged to be accessible, in order for such maintenance to be maintained.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a light absorbing unit for a liquid medium which enables flexible and effective energy yield.

SUMMARY OF THE INVENTION

This and other objects, which will become apparent from the following description, are achieved by a light absorbing unit of the initially described type, and which further has the features stated in the characterizing part of the appended independent claim 1. Preferred embodiments of the light absorbing unit are defined in the accompanying dependent claims.

According to the invention the objects are achieved by a light absorbing unit for heating, via a light-transmissive layer, of at least one liquid medium by means of solar energy comprising a channel configuration inside of said light- transmissive layer in which said liquid medium is adapted to flow for said heating, wherein light absorbing means are configured to substantially house said channel configuration, wherein said light-transmissive layer comprises a semi-transparent solar cell element. This makes it possible to, in addition to the generation of thermal energy by allowing solar energy in the form of direct sunlight to be transmitted through the semi-transparent solar cell element to the light absorbing means for absorption, also generate electrical energy where the proportion of thermal energy and electrical energy is determined by the degree of light transmission of the semi-transparent solar cell element. The greater transparency, i.e. the greater light transmission, at the semi-transparent solar cell element, the greater part thermal energy and relatively smaller part of electrical energy and vice versa. Hereby is consequently obtained two functions in one and the same unit in that both thermal energy and electrical energy are generated such that a hybrid solution is thus obtained. This makes it possible, with one set of such light absorbing units arranged, according to a variant integrated, in a roof structure or wall structure, to have different degrees of light transmission of different units. Further, the degree of light transmission can be adapted to the geographical position, for example by having greater degree of electric power generation in warmer climates and in cooler climates have greater degree of generation of thermal energy. Consequently, a flexible and efficient energy exchange is made possible by the semi-transparent solar cell element.

According to one embodiment of the light absorbing unit, said semi- transparent solar cell element includes a thin film solar cell for generating electrical energy. This enables efficient generation of electricity in a compact construction. According to a variant, said thin film solar cell includes cadmium telluride, CdTe.

According to one embodiment of the light absorbing unit, said light- transmissive layer includes two transparent layers between which said solar cell element is arranged. This provides a stable and robust, and for good sealing adapted semi-transparent solar cell element which can thus constitute the outer layer when used outdoors.

According to one embodiment of the light absorbing unit, said two

transparent layers are continuous and enclose said solar cell element at the top side and bottom side. Thereby the life expectancy of the solar cell element is prolonged considerably since it is isolated from moisture or other harmful substances that are harmful to the solar cell element. According to one embodiment of the light absorbing unit, at least one of said transparent layers consists of a glass material. Glass constitutes a suitable material that is robust and has good light transmission.

According to one embodiment of the light absorbing unit, said light- transmissive layer is arranged at a distance from said light absorbing means for forming an insulating space. This allows for optimized generation of thermal energy since heat loss can be avoided by the thus-formed insulating space/insulating layer. According to one embodiment of the light absorbing unit, said light- transmissive layer is arranged to abut against said light absorbing means in a heat-exchanging configuration. By thus allowing the light-transmissive layer, i.e. the semi-transparent solar cell element, to abut the light absorbing means, thermal contact is created there between that will result in heat exchange. Thus is obtained a relatively lower generation of thermal energy as compared to the variant with the insulating layer created by having the light-transmissive layer spaced from the light absorbing means, but a higher electric power generation since the temperature thanks to the heat exchange will be lower in the solar cell element. Consequently is hereby obtained a cooling effect for higher efficiency in the semi-transparent solar cell element. Further is hereby obtained a relatively lower light absorbing unit which allows a total height essentially corresponding to the height of a traditional batten on a roof, which makes it possible to install, on an existing roof, such light absorbing units by means of replacing the existing battens with one or more light absorbing units according to this variant, at the desired location on the roof.

According to one embodiment of the light absorbing unit, said light absorbing unit has a substantially parallelepiped configuration. A thus designed light absorbing unit facilitates the design and installation, for example at installation for integration in a roof or wall structure.

According to one embodiment of the light absorbing unit, said optionally present insulating space consists of air and/or said light absorbing means is surrounded by air at its bottom side. This will enable a structure that is cost- effective, that minimizes maintenance, and that also minimizes connection and installation costs. Additionally is obtained a weight- and space-saving design.

According to one embodiment of the light absorbing unit, said air has a substantially similar configuration as the ambient air, advantageously a similar composition and/or pressure as the ambient air. This means in particular that the above costs are kept low.

According to one embodiment of the light absorbing unit, said light- transmissive layer, along its longitudinal extension, is only supported on or at the long sides of the light absorbing unit. This maximizes the amount of light that can reach the light absorbing means since no further overriding support elements are needed.

According to one embodiment of the light absorbing unit, the solar cell element extends continuously along the entire upper surface of the light absorbing unit. By upper surface is intended, in this context, the on top lying area of the light absorbing unit between the long sides. The upper surface refers to the outer side of the light absorbing unit which is closest to the solar cell element. It should therefore be noted that the upper surface does not necessarily have to be facing upwards, but at a certain orientation of the light absorbing unit it can be facing more towards the side than upwards. Said embodiment maximizes the amount of light that can be converted to current by the solar cell element.

According to one embodiment of the light absorbing unit, at least one batten is provided at the light absorbing unit in order to support roof tiles. This permits a particularly simple way to integrate the light absorbing unit in a roof.

According to one embodiment, the light absorbing unit is intended to constitute an integral part of a roof, wall, balcony or terrace structure. Thus, by integrating a set of such light absorbing units it is made possible to have different degrees or the same degree of light transmission of different units. By thus integrating the light absorbing unit is obtained an aesthetically attractive structure in that a construction and shape is obtained which does not differ substantially from the building. By them being thus integrated, they are consequently difficult to remove and therefore difficult to steal. Because they are integrated and therefore not exposed, they will not gather dirt, leaves or the like to the same extent as a unit mounted on the roof or on the wall. By thus integrating the light absorbing unit the service life is extended.

According to one embodiment, the light absorbing unit is intended to constitute an integral part of a roof structure, wherein the roof structure comprises transparent roof tiles. By thus integrating the light absorbing unit is obtained an aesthetically attractive structure in that a construction and shape is obtained which does not differ substantially from the building. Because they are integrated and therefore not exposed, they will not gather dirt, leaves or the like to the same extent as a unit mounted on the roof or on the wall. By thus integrating the light absorbing unit the service life is extended. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood by reference to the following detailed description read together with the accompanying drawings, in which like reference numerals refer to like parts throughout the several views, and in which:

Fig. 1 schematically illustrates a perspective view of a light absorbing unit according to one embodiment of the present invention; Fig. 2 schematically illustrates a cross section end view of a portion of the light absorbing unit according to one embodiment of the present invention; Fig. 3 schematically illustrates a cross section end view of a portion of a light absorbing unit according to one embodiment of the present invention;

Fig. 4 schematically illustrates a perspective view of light absorbing units according to Fig. 1 integrated in a roof structure;

FIG. 5a schematically illustrates an end view of the light absorbing unit in Fig. 1 integrated in a roof structure;

FIG. 5b schematically illustrates a cross section end view of the light absorbing unit integrated in a roof structure; and

Fig. 5c schematically illustrates an end view of a light absorbing unit according to another embodiment integrated in a roof structure. DETAILED DESCRIPTION

Fig. 1 illustrates schematically a perspective view of a light absorbing unit in accordance with one embodiment of the present invention and Fig. 2 shows a cross section end view of a portion of the light absorbing unit I. The light absorbing unit I is intended to, via a light-transmissive layer 70, heat at least one liquid medium L by solar energy.

The light absorbing unit I comprises a channel configuration 21 , 22 inside of said light-transmissive layer 70, in which said liquid medium L is arranged to flow for said heating.

The light absorbing unit I comprises light absorbing means 30 configured to substantially house said channel configuration 21 , 22. The light absorbing means 30 is provided for generating thermal energy by letting the solar energy in the form of direct sunlight to be transmitted through the light- transmissive layer 70 to the light absorbing means 30 for heating said liquid medium. The light absorbing unit I further comprises means, for example a pump arrangement (not shown) arranged to achieve said flow of the liquid medium L.

Said light-transmissive layer 70 comprises a semi-transparent solar cell element 76.

Said semi-transparent solar cell element 76 includes a thin film solar cell 76 for generating electric energy. According to a variant, said thin film solar cell 76 includes cadmium telluride, CdTe.

The light absorbing unit I is hereby arranged to, by means of said semi- transparent solar cell element 76, generate electrical energy, and, through light radiation in the form of direct sunlight that is allowed to be transmitted through the semi-transparent solar cell element 76 by means of the light absorbing means 30, heat up the liquid medium L that is circulating in the channel configuration, 21 , 22 in order to generate thermal energy. As a result, this makes it possible to, in addition to the generation of thermal energy, also generate electrical energy where the proportion of thermal energy and electrical energy is determined by the degree of transparency of the semi-transparent solar cell element.

Said light-transmissive layer 70 comprises two transparent layers 72, 74 between which said solar cell element 76 is arranged. Said transparent layers 72, 74 comprise an outer transparent layer 72 intended to be arranged outside of the solar cell element and consequently towards incoming sunlight. Said transparent layers 72, 74 comprise an inner transparent layer 74 intended to be arranged inside of the solar cell element and consequently facing towards said light absorbing means 30. At least one of said transparent layers 72, 74, preferably both layers 72, 74, consists of a glass material. Said two transparent layers 72, 74 are advantageously continuous and enclose said solar cell element 76 at the top side and bottom side. An underlying sheet of glass is particularly advantageous to use because it is anyhow needed during the production process of thin film solar cells, in particular of cadmium telluride. The fact that said two transparent layers 72, 74 are continuous prolong the life expectancy of a light absorbing unit according to the present invention considerably, since any voids or other openings in said two transparent layers 72, 74 would allow for moisture to enter into the light-transmissive layer 70 and thus destroy said solar cell element 76. By continuous is meant, in this context, that no cavities, breaks, interruptions or the like are present in said two transparent layers 72, 74. In one example, each of said two transparent layers 72, 74 are from a continuous piece.

Said light-transmissive layer 70 is arranged at a distance from said light absorbing means 30 in order to form an insulating space 3/insulating layer 3. Said light-transmissive layer 70 is arranged at a distance from said light absorbing means 30 so that heat losses through thermal bridges are avoided. Said insulating space 3/insulating layer 3 consists advantageously of air. The air in said insulating space 3/insulating layer 3 has advantageously a similar configuration as the ambient air, i.e. it does not differ substantially from the ambient air composition or pressure. With ambient air, referred to herein, is meant the air outside the light absorbing unit I. By having air, in particular air in a similar configuration as the ambient air, no additional equipment is required such as e.g. vacuum pumps for changing pressure or other apparatuses for changing the configuration. Thereby is obtained an economical design. In addition the maintenance is considerably facilitated. Furthermore, connection costs are reduced as well as the weight, which can be crucial, especially when a light absorbing unit of the present invention is mounted on a roof.

By having similar pressure of the air in the insulation space also no support pillars are needed to counteract the pressure from the ambient air on the material such as the light-transmissive layer 70, which otherwise would be bent inwards due to the pressure difference. Such an inward bending would prevent the use of silicon solar cells since these are not bendable but would crack immediately.

Said light-transmissive layer 70 is thus arranged to thermally insulate said channel configuration 21 , 22 for said liquid medium L against the ambient air.

Said light-transmissive layer 70 is disposed in the vicinity of and at said distance D1 from said channel configuration 21 , 22 and consequently the light absorbing means 30 in order to allow efficient heating of said liquid medium L by means of solar energy.

The light-transmissive layer 70 of the light absorbing unit that is arranged at a distance D1 from the light absorbing means 30 is configured to provide functionality as thermal insulation/sealing for providing a high thermal energy exchange in the light absorbing unit I.

The light-transmissive layer 70 is in this embodiment arranged to thermally insulate the channel configuration 21 , 22 for the flowing medium L. In one embodiment, the light-transmissive layer 70 is arranged in such a manner including sealing/insulating thermal and distance D1 from the light absorbing means 30 that thermal energy transfer according to the type described above in the light absorbing unit I per time unit is maximized for a given light transmission of the semi-transparent solar cell element 76 of the light- transmissive layer 70.

Said light absorbing unit I is substantially a parallelepiped in its configuration. In the example shown, said light absorbing unit has a box-shaped

configuration.

The light absorbing unit I is elongate and has two long sides 42, 44 extending in parallel and at a distance from each other, two short sides 46, 48 extending in parallel and at a distance from each other and connected to the long sides 42, 44 thereby forming a substantially rectangular shape.

Furthermore, the light absorbing unit I has a bottom side 45 that connects the long sides 42, 44 and short sides 46, 48. The thus connected long sides, short sides and bottom side thus form a box unit 40 arranged to receive and accommodate said channel configuration 21 , 22 and said light absorbing means 30.

The light absorbing unit I comprises insulation means 50 having insulating properties. Said insulation means 50 is arranged in said box-shaped unit 40 of the light absorbing unit I.

Said insulating means 50 comprises an insulating layer 52. The insulating layer 52 consists according to one variant of a stonewool mat. The insulating layer 52 is configured to be disposed on the bottom of the box- shaped unit.

Said insulation means 50 includes side insulation elements 54, 56 arranged for insulation of the long sides 42, 44 of the light absorbing unit I. Said side insulation members 54, 56 include a first side insulation member 54 provided in the box-shaped unit to essentially abut against and run along one long side 42, and a second side insulation member 56 provided in the box-shaped unit to essentially abut against and run along the second long side 44 of the light absorbing unit I. The first and second side insulation members 54, 56 have a height essentially corresponding to the height of the first and second long side 42, 44. Said insulation means 50 further includes non-shown end insulation means arranged to insulate the short sides 46, 48. The light absorbing unit I comprises a batten 60 which is included in the second long side 44. The batten 60 is described in more detail below with reference to Figs. 4, 5a and 5b.

The insulating layer 52 is arranged to be accommodated tightly between the first and second side insulation member 54, 56.

The light absorbing means 30 forms, together with the channel configuration 21 , 22, an absorbent member 35. The absorbent member 35 has an elongated shape. The absorbent member 35 has a surface that is black, or dark such as dark gray, dark blue, dark green or the like for the absorption of light.

Said liquid medium L is intended to flow in said first and second channel portion for heating. The first and second channel portion 21 , 22 are

constituted, according to a variant, of copper piping for good heat conduction.

Additionally, the light absorbing unit I comprises annular sealing portions T1 , T2 arranged to surround the respective channel portion 21 , 22 and

essentially abut against the short side 46, 48 adjacent to the channel portion 21 , 22.

Through said sealing portions T1 , T2 is obtained good sealing of the light absorbing unit I. Further, materials such as pollen, leaves or the like are prevented to enter and come into contact with the light absorbing means 30 so that the absorption deteriorates. Furthermore, fire hazard is avoided due to entering of flammable material such as dry leaves or similar. In addition, better heat retention and consequently a more energy-efficient light absorbing unit I is obtained by improved sealing. Also is achieved simple assembly.

Fig. 3 illustrates schematically a cross section end view of a portion of a light absorbing unit II according to an embodiment of the present invention.

The light absorbing unit II according to the embodiment illustrated in Fig. 3, differs from the light absorbing unit I of the embodiment illustrated in Fig. 2 mainly by the orientation of the light-transmissive layer 70. Fig. 1 shows thus also the embodiment II. According to the embodiment of the light absorbing unit II in Fig. 3, said light- transmissive layer 70 is arranged to abut against said light absorbing means in a heat-exchanging configuration.

The light-transmissive layer 70 with the semi-transparent solar cell element 76 is arranged to abut against the light absorbing means 30 such that thermal contact is obtained therebetween for the heat exchanging

configuration. This yields a relatively lower generation of thermal energy as compared to having the light-transmissive layer 70 at a distance from the light absorbing means 30. Thanks to the heat exchange, the temperature will be lower in the solar cell element which results in a higher generation of electric energy.

Apart from batten 160 in embodiment II having a lower height than batten 60 of embodiment I, all other parts of the batten are equal to those of

embodiment I and will not be illustrated with reference numerals once more. This applies for example to the upper portion 62, the foot portion 64, etc.

The height H2 of the light absorbing unit II hereby becomes lower than the height H1 of the light absorbing unit I, see Fig. 2. This allows a total height H2 that is essentially equivalent to the height H2 of a traditional batten on a roof which makes it possible to install such light absorbing units II on an existing roof by replacing the existing batten on the desired location on the roof with one or more light absorbing units according to this variant. Fig. 4 illustrates a perspective view and Figs. 5a-b are end views of sets of the light absorbing unit I integrated in a roof structure 100.

The light absorbing unit I in accordance with this embodiment is intended to, via a transparent surface layer 10 in the form of a roofing, where the roofing comprises transparent roof tiles 10, according to one variant glass tiles, heat a liquid medium L by means of solar energy. By said roofing including transparent roof tiles 10, an aesthetically attractive light absorbing device is made possible where the light absorbing unit I is integrated in a roof structure 100 and the light absorbing unit I consequently constitutes an integrated part of the roof structure 100, where the light absorbing device including said light absorbing units I is easy to replace or to construct anew.

The transparent surface layer 10, i.e. the tiles 10, provide functionality such as mechanical protection against objects, e.g. falling tree branches or hail, or conditions, such as wind forces, etc., and provides insulation.

The light absorbing device I comprises a space 2 inside of said roofing in which said liquid medium L is arranged to flow.

The light-transmissive layer 70 is thus disposed between the thus thermally insulated channel configuration 21 , 22 and the surface layer 10 in the space 2. The transparent surface layer 10 in the form of said roof tiles 10 thereby constitutes an outer transparent layer and the light-transmissive layer 70 constitutes an inner light-transmissive layer in order for generation of thermal energy and electrical energy to be made possible.

The bottom side 45 is intended to face towards and rest on vertical batten portions 104, called battens 104, of a roof as shown in Fig. 5a.

Said transparent roof tiles 10 of said transparent outer surface layer are arranged to be supported by means of the battens 60 of the light absorbing unit I. Said battens 60 are provided to form part of said light absorbing unit I in said roof structure 100, said battens 60 being adapted to be arranged in said roof structure 100 with the light absorbing unit I. As shown in particular in Fig. 2, said battens 60 have a substantially L- shaped cross-section across its length. Said batten 60 comprises an upper portion 62 as support for tiles 10. Said upper portion 62 of the batten 60 is arranged to protrude over an upper side 70 of said light absorbing unit I.

Said batten 60 further includes a foot portion 64 of said L-shaped cross section.

Said upper portion 62 is shorter across the batten's 60 longitudinal direction than said foot portion 64. Said upper portion 62 thus has an extension S1 across the batten's 60 longitudinal direction which is shorter than the extension S2 of said foot portion 64 across the batten's 60 longitudinal direction.

Said batten 60 has an intermediate portion 44 intended to constitute one long side 44 of the light absorbing unit I.

Said upper portion 62 has a downwardly open essentially U-shaped configuration. Said upper portion 62 includes a planar top portion 62a arranged to protrude in a direction away from the long side 44 of the light absorbing unit I. Said upper portion 62 further comprises a hook portion 62b directed downwards at an angle, according to one variant essentially perpendicular, from said flat top portion 62a, running parallel to and at a distance from said intermediate portion 44.

Said foot portion 64 has an upwardly open essentially U-shaped

configuration. Said foot portion 64 comprises a flat bottom portion 64a arranged to protrude in a direction away from the long side of the light absorbing unit I. Said foot portion 64 is, according to the embodiment illustrated in Fig. 4, intended to abut against a batten portion 104 of the roof structure 100, which batten portion extends transversally to the batten 60. The foot portion 64 further includes a stop portion 64b directed upwards at an angle, according to one variant essentially perpendicular, from said flat bottom portion 64a, running parallel to and at a distance from said

intermediate portion 44. Said stop portion 64b of the foot portion 64 is arranged to constitute a stop for the light absorbing unit I so that it is not displaced. Between the stop portion 64b of the batten 60 of a light absorbing unit I and an adjacent light absorbing unit, is arranged a spacer 80 in the form of an element extending between adjacent light absorbing units. This avoids overlapping of the tiles which optimizes the light inflow to the light- transmissive layer. Instead of arranging spacers 80 as illustrated in Figs. 5a and 5b, the bottom portion 64a of the batten 60 may be designed to be wider such that the stop portion 64b abuts against the adjacent light absorbing unit and thus constitutes a spacer. Alternatively, as illustrated in Fig. 5c, the light absorbing unit may be designed to be wider such that the stop portion 64b abuts against the adjacent light absorbing unit.

Said L-shaped cross section of the batten 60 is in one embodiment arranged to be obtained by extrusion. Said batten could according to an alternative variant constitute a separate unit and be arranged to be attached by fastener elements, such as screw or rivet joints, at one long side of the light absorbing unit.

From the respective long sides 42, 44, a support portion 42a, 44a is arranged to protrude in a direction away from the long side 42, 44 of the light absorbing unit I, facing each other and arranged to run along the respective long side 42, 44. The respective support portions 42a, 44a are adapted to support the light-transmissive layer 70. The light-transmissive layer 70 is therefore arranged resting on and supported by said support portions 42a, 44a. Each support portion 42a, 44a further includes a hook portion 42b, 44b directed downwards from the respective support portion 42a, 44a in order to facilitate retention of said side insulation elements 54, 56.

From the respective long sides 42, 44 there is arranged a bottom securing portion 42c, 44c arranged to protrude in a direction away from the long side 42, 44 of the light absorbing unit I, towards each other and arranged to run in height with the bottom side 45 along the respective long side 42, 44. The respective bottom securing portion 42c, 44c is arranged to constitute a securing portion for the bottom side 45, where the bottom side consists of a bottom plate 45. The respective bottom securing portion 42c, 44c has a recess against which the bottom plate is arranged to be secured by means of fastener elements, according to one variant by means of double sided adhesive tape.

According to a variant, each short side 46, 48 has, same as the long side 42, a corresponding support portion for supporting the light-transmissive layer 70 and bottom securing portion for securing the bottom plate 45. According to a variant, the long side 42 and the short sides 46, 48 form a unit, which in the manufacturing has been a straight long unit that has been provided with cutouts so that the respective short side 46, 48 and long side 42 have been formed by bending the short sides 46, 48 perpendicular relative to the long side 42 such that the long side and short sides form a U-shape when seen in an elevated view. What has been said above concerning the light absorbing unit of embodiment I apply in a similar way to the light absorbing unit according to embodiment II.

FIG. 5a shows the light absorbing unit I or II with a portion of a roof structure 100. The roof structure includes a base layer 102 comprising a waterproof layer which, according to one variant, includes conventional roofing board.

The base layer 102 is conventional vertical lath portions 104, also called battens or batten portions 104, arranged at a distance from each other. With vertical batten portions is meant batten portions running along the roof structure from the eaves to the ridge, perpendicular to the horizontal direction.

Fig. 5c schematically illustrates a side view of a light absorbing unit III in Fig. 1 integrated in a roof structure. The light absorbing unit III of Fig. 5c differs from the light absorbing unit I or II, for example as in Fig. 5a, by the light absorbing unit III being slightly wider than the light absorbing unit I or II, such that the foot portion of the batten 60 or 160 forms a spacer between two adjacent light absorbing units III. What is obtained is a slightly larger surface of the light-transmissive layer 70, not shown in Fig. 5c, for improved energy efficiency.

Figs. 4, 5a and 5b show the light absorbing unit I integrated in a roof structure. The light absorbing unit II illustrated in Fig. 3 can also

advantageously form an integral part of a roof structure.

Said light absorbing unit I; II; III is arranged such that said channel portions 21 , 22 run essentially parallel to each other and parallel to the horizontal battens 60 and at such distance that the battens 60 do not shade the channels 21 , 22. This provides more efficient heating of the liquid medium L.

A light absorbing unit is connectable at its end portion, via the protruding channel portions 21 , 22, by connecting channel portions of one light absorbing unit I; II; III with channel portions of a further light absorbing unit in one another's longitudinal extension.

A set of assembled light absorbing units integrated in a roof structure have at least one inlet and at least one outlet. Accordingly, the liquid medium L is arranged to flow between the inlet and the outlet of the configuration of the channels 21 , 22 for heating of the same.

The light absorbing unit I; II; III of the present invention may be used for heating of one or several liquid media, for any desired purposes. For example, the light absorbing unit I; II; III may be used to heat water for domestic hot water, heat water in an accumulator tank to run against heating systems such as radiators, liquid-air convectors or underfloor heating, as well as to regenerate energy wells and/or heat pool water. The light absorbing unit I; II; III as above has two channel portions 21 , 22 extending in parallel and spaced from each other and running in the longitudinal direction of the light absorbing unit I. The light absorbing unit I; II; III could alternatively have one channel portion or more than two channel portions running in the longitudinal direction of the light absorbing unit I; II; III.

Above, an embodiment of a light absorbing means 30 has described for heating of the liquid medium. The light absorbing means may however be of any suitable design for heating by means of solar energy and is not limited to the light absorbing means 30 according to the disclosed embodiments.

A corresponding light absorbing unit could alternatively be an integral part of a wall structure, an integral part of a balcony structure, or an integral part of a terrace structure.

The light absorbing unit I; II; III of the present invention may alternatively be a non-integrated light absorbing unit and can therefore be applied for example on a roof or a wall for said generation of thermal and electric energy.

The light absorbing unit I; II; III, according to the embodiments of the present invention, has an essentially parallelepiped shape. The light absorbing unit of the present invention may however have any suitable geometric form for said generation of thermal and electric energy.

The light absorbing unit I; II; III according to the embodiments of the present invention has a batten 60; 160. The light absorbing unit of the present invention may be configured without battens, which is suitable for integration in a wall structure or terrace structure as well as in a non-integrated variant.

The above description of the preferred embodiments of the present invention has been provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to limit the invention to the variants described. Obviously, many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described to best explain the principles of the invention and its practical applications, thereby enabling a skilled worker to understand the invention for various embodiments and with the various modifications suitable for the intended use.