ABSORBER ARRANGEMENT FOR A TROUGH COLLECTOR

Abstract

The invention relates to an elongated absorber arrangement for a trough collector, which is subjected to concentrated radiation over its length during operation, and which has means for transporting heat-transporting fluid through the absorber arrangement. The absorber arrangement has at least one fluid-free absorber space for concentrated radiation, which has a thermal opening leading into its interior and walls for absorption of the heat incident into it. The means for transporting the fluid have a supply arrangement and a drain arrangement which are operatively connected to one another by means of a heat-exchanger arrangement through which fluid flows, wherein the same extends along the length of the absorber arrangement, is constructed for the throughflow of the fluid in transverse flow for the length of the absorber arrangement and is thermally connected to the at least one absorber space in such a manner that the fluid is heated during operation in transverse flow from an inlet temperature to the operating temperature and reaches the drain arrangement at this temperature.

Description

The present invention relates to an absorber arrangement for a trough collector plant according to the preamble of claim 1. Trough collectors of the stated type are used among other things in solar power plants.

Until now it has not been possible to generate solar electricity in an approximately cost-covering manner by using this technology, owing to the disadvantages of photovoltaics which have not been overcome. By contrast, for some time, solar power plants have already been producing power on an industrial scale at prices which, compared to photovoltaic methods, are close to the commercial prices now usual for power produced in the conventional manner.

In solar thermal power plants, the radiation of the sun is reflected by the concentrator of collectors and focused in a targeted manner on a location in which high temperatures arise as a result. The concentrated heat can be conducted away and used to operate thermal engines such as turbines which in turn drive the generators which generate electricity.

Three basic forms of solar thermal power plant are currently in use: dish/Stirling systems, solar tower plant systems and parabolic trough systems.

The dish/Sterling systems as small units in the range of up to 50 kW per module have generally not caught on.

Solar tower plant systems have a central absorber which is mounted in an elevated manner (on the “tower”) for the sunlight which is reflected to it by means of hundreds to thousands of individual mirrors, whereby the radiation energy of the sun is concentrated in a punctiform manner in the absorber by means of the many mirrors or concentrators and on account of the thus achievable high concentration, temperatures of up to 1300° C. can be reached, which is favourable for the efficiency of the downstream thermal engines (generally a steam or fluid turbine power plant for electricity generation). Solar tower power plants have hitherto likewise not become widespread (in spite of the advantageously achievable high temperatures), due to the somewhat difficult technology which is intrinsic to them.

Parabolic trough systems are widespread however and have a large number of trough collectors which have long concentrators having small transverse dimensions and therefore do not have a focal point but a focal line, which fundamentally distinguishes these in their design from the dish Stirling and solar tower power plants. These linear concentrators today have a length of 20 m to 150 m whilst the width can reach 5 m or 10 m and more. An absorber line for the concentrated heat (up to nearly 500° C.) is arranged in the focal line, wherein a medium, which absorbs the heat and transports the same via lines to the machine hall of the power plant, flows through the absorber line. A fluid such as e.g. thermal oil or superheated steam are possibilities for the heat-transporting medium.

The 9 SEGS parabolic trough plants in Southern California together produce an outlet of approx. 350 MW. The power plant “Nevada Solar One”, connected to the mains in 2007, has trough collectors with 182,400 curved mirrors, which are arranged on an area of 140 hectares, and produces 65 MW. The plants Andasol 1 to 3 should have a maximum outlet of 50 MW (Andasol 3 entered into operation at the end of 2011). For the plant as a whole (Andasol 1 to 3), a peak efficiency of approx. 20% and also an annual average efficiency of about 15%.

Naturally, it is the case that attempts are being made to increase the temperature in the heat-transporting medium to the greatest extent possible, as with the high temperature thereof, the efficiency of the conversion of the heat obtained in the plant into electricity for example is higher. As high temperatures as possible are also desired in case the solar power plant is to deliver heat for processes of industrial production.

For the efficiency of the power plant, the emission or radiation of heat via the lines in which the heat-transporting medium circulates (heat loss). is to be taken into account This may reach 100 W/m, with a line length of the order of magnitude of up to 100 km, so that the heat losses over the lines are of considerable importance for the overall efficiency of the power plant, also including the absorber pipes' proportion of heat losses. From the above information, it follows that the entire length of the trough collectors and accordingly also that of the absorber pipes in such solar plants reaches dozens of kilometres, thus the heat losses thereof cannot be neglected for the efficiency of the plant as a whole.

Accordingly, the absorber lines are built increasingly complexly in order to avoid such energy losses. Thus, widespread conventional absorber lines are constructed as a metal pipe enveloped by glass, wherein a vacuum prevails between the glass and metal pipe. The metal pipe conveys the heat-transporting medium in its interior and is provided on its outer surface with a coating which better absorbs the incident light in the visible range, but has a deep emission rate for wavelengths in the infra-red range. The enveloped glass pipe protects the metal pipe from cooling by means of the wind and acts as an additional barrier for heat radiation. It is disadvantageous that the enveloping glass wall partly likewise reflects or even absorbs incident concentrated solar radiation, which means that a layer reducing the reflection is applied to the glass.

In order to reduce the expensive cleaning outlay for such absorber lines, but also in order to protect the glass from mechanical damage, the absorber line can additionally be provided with a mechanical protection pipe which envelops it and which although it must be supplied with an opening for the incident solar radiation, otherwise protects the absorber line very reliably.

Such designs are complex and relatively expensive, both in terms of production and in terms of maintenance.

In WO 2010/078 668 (which is here included in the present application by way of reference) an externally-insulated absorber pipe with improved efficiency is disclosed, the elongated thermal opening of which exists on account of the use in a trough collector and is constructed as a slot opening and is optimised with regards to the heat losses, in that the thermal opening is made smaller over the length of the absorber pipe in accordance with the longitudinally-increasing temperature of the heat-transporting medium which flows longitudinally through the absorber pipe. As heat radiation increases with the fourth power of the temperature, an overwhelming part of the overall energy losses of the absorber pipe are prevented in this manner, even though the complex measures for making the thermal opening smaller are only performed in a comparatively small area of the absorber pipe.

It is the object of the present invention to provide an absorber arrangement suitable for high operating temperatures of the heat-absorbing medium, which absorber arrangement has low heat losses and can be produced inexpensively in series.

This object is achieved by means of an absorber arrangement according to the characterising features of claim 1.

The fact that a heat exchanger arrangement, which is constructed for the throughflow of the heat-transporting fluid in transverse flow, is provided means that the absorber space can be constructed in such a manner by means of the separation of the at least one absorber space from the heat exchanger, through which fluid flows, that even at high temperatures of more than 500° C., for example up to 650° C. or even higher, the heat radiation through the thermal opening thereof falls to a lesser extent and as a result, the efficiency of the heat-exchanger arrangement as a whole is improved.

The invention is explained in more detail hereinafter by means of the figures.

In the figures:

FIG. 1 shows a trough collector with an absorber pipe of conventional type,

FIG. 2 shows a view onto a section of a first embodiment of the absorber arrangement according to the invention,

FIG. 3 shows a view onto a section of a second embodiment of the absorber arrangement according to the invention,

FIG. 4 shows a view onto a section of a third embodiment of the absorber arrangement according to the invention,

FIG. 5 shows a view onto an absorber space formed by a part of the heat-exchanger arrangement,

FIG. 6 shows a cross section through a trough collector with an absorber arrangement according to the invention, which has at least two parallel mutually adjacently arranged longitudinally running absorber spaces, and

FIG. 7 shows a cross section through the absorber arrangement of FIG. 6.

FIG. 1 shows a trough collector 1 of conventional type, with a concentrator 2 which is parabolically curved in cross section and reflects incident solar rays 3, wherein the reflected rays 4 are concentrated into a focal line region in which an absorber pipe 5 is arranged. Via a supply line 6, the absorber pipe 5 is fed with a heat-transporting medium which flows through the same, is heated in the process from an inlet temperature T_E to an outlet temperature T_A and finally is conducted away by means of a drain 7.

Schematically illustrated links 8 allow the pivoting of the concentrator 2 about the pivot axis 10, so that the concentrator 2 can constantly be made to track the current position of the sun. Bearings 11 for the concentrator 2 and the lines 6, 7 are likewise schematically illustrated.

In the graph D, the profile of the temperature T of the heat-transporting medium over the length L of the absorber pipe 5 is qualitatively illustrated by means of the curve 15. The temperature curve 15 is essentially linear, in accordance with the heat supplied evenly over the length L to the absorber pipe (and thus the fluid flowing longitudinally through the same) by means of the reflected rays 4.

The absorber pipe 5 has a thermal opening, which is not illustrated so as not to overload the figure, through which the rays pass into the interior of the absorber pipe 5 and heat the heat-transporting fluid. An arrangement of this type is known to the person skilled in the art from the above-mentioned WO 2010/078 668. The interior of the absorber pipe 5 (including the heated heat-transporting fluid) heated by the reflected rays 4 radiates heat in the infra-red range, wherein this heat back radiation or reemission escapes from the absorber pipe through the thermal opening. This back radiation or reemission increases with the fourth power of the temperature prevailing in the interior of the absorber pipe 5. The curve 16 qualitatively shows the profile of the radiation intensity through the thermal opening of the absorber pipe 5. In other words, it is the case that the absorber pipe continuously loses energy with the fourth power of the internal temperature thereof, so that a fundamentally desirable further increase of the outlet temperature T_A from 500° C. to for example 650° C. or more is problematic, because, among other reasons, the back radiation or remission is just as high after a certain length of the absorber pipe 5 as the irradiation by means of the reflected rays 4, so that a further increase of the temperature in the fluid no longer takes place.

FIG. 2 schematically shows an absorber arrangement 20 according to the present invention, as can be used in the place of the absorber pipe 5 in a trough collector (FIG. 1). Only a longitudinal section 21 of the absorber arrangement 20 is illustrated in the figure, starting with a cross section through the absorber arrangement 20 at any desired point along the length thereof and a view of the longitudinal section 21 through to a section line 22 following the cross section, wherein the absorber arrangement 20 continues after the section line 22 through to the end of the respective trough collector. At this point, it may be added that absorber arrangements in a length greater than 100 m, preferably greater than 150 m and preferably up to 200 m or more may be realised according to the invention, which allows correspondingly long trough collectors and is beneficial for the industrial deployment of trough collectors in a solar power plant.

Visible are means for transporting the heat-transporting fluid, with a supply arrangement, here constructed as pipelines 23, 24, and a drain arrangement, here constructed as pipelines 25, which extend along the length L of the absorber arrangement and are operatively connected to one another by means of lines, here constructed as pipelines 26. The pipelines 26 here lie next to one another in two rows 27 and 28 and form a heat-exchanger arrangement 29. The row 28 is indicated by means of the contours of the mutually adjacent pipelines 26, the row 27 is covered in the view illustrated.

Between the rows 27, 28 of pipelines 26 of the heat-exchanger arrangement 29 lies an absorber space 30 for concentrated, i.e. reflected radiation 4, through the thermal opening 35 of which, the rays 4 fall. Walls 36 of the absorber space 30 absorb the heat of the heat incident by means of the rays 4 and pass this on to the pipelines 26 of the heat-exchanger arrangement 29, to which they are thermally connected, for example by means of direct contact with the walls 36, as is illustrated in the figure.

During operation, heat-transporting fluid is supplied to the pipelines 26 of the heat-exchanger arrangement 29 over the length L with the inlet temperature T_E by means of the inlet sections 38 of the pipelines 23, 24 of the supply arrangement, wherein the fluid is heated to the outlet temperature T_A in the pipelines 26 and is passed at this temperature from the outlet sections 39 to the pipeline 25 of the drain arrangement, likewise over the length L of the absorber arrangement.

In other words, it is the case that

• • in one embodiment of the invention, the supply arrangement and the drain arrangement have a supply pipe 23, 24 and a drain pipe 25, wherein the pipes 23, 24, 25 run parallel to one another and the at least one absorber space 30 is arranged between pipes 23, 24, 25 and extends over the length of the pipes 23, 24, 25.
  • In one embodiment of the invention, the supply arrangement has a feed line 23, 24 for the fluid to be heated and supplied to the heat exchanger over its length, which feed line extends over the length of the absorber arrangement, wherein the feed line 23, 24 is preferably thermally insulated over its length through to the openings for the supply of the heated fluid. This may be advantageous if the inlet temperature T_E is above the ambient temperature.
  • In one embodiment of the invention, the drain arrangement has a collecting line 25, extending over the length of the absorber arrangement, for heated fluid supplied to it over its length from the heat-exchanger arrangement 29, wherein the collecting line 25 is thermally insulated over its length through to the openings for the supply of the heated fluid.

It follows that the heat-transporting fluid flows longitudinally through the absorber arrangement as before, but it two separate flows, once with the inlet temperature T_E and once with the outlet temperature T_A, as is symbolised by the flow arrows in the figure. Furthermore, it follows that the heat-transporting fluid is moved in a direction crosswise to the length of the absorber arrangement during the absorption of heat.

In the heat-exchanger arrangement however, the fluid flows in transverse flow to the length L, with the consequence that over the entire length L of the absorber arrangement 20 in the line 25 of the drain arrangement, fluid with the outlet temperature T_A is present. The following advantages result by means of this transverse flow principle:

The absorber space 30 can be laid out once in terms of its shape by the person skilled in the art in such a manner that for a given concentrator 2 (FIG. 1), principally the inlet region of the absorber space 30 is illuminated by the rays 4. In the inlet region close to the thermal opening 35, the fluid has another low temperature close to the inlet temperature T_E, with the consequence that the inlet region is strongly cooled, thus the heat reflection/reemission thereof is correspondingly low. With regards to reemission, the thermal opening 35 overwhelmingly “sees” the inlet region, much less however the (far away, rearmost) wall of the absorber space 30 which is opposite the inlet region and for its part is heated to the outlet temperature T_A. The absorber spaces illustrated in the figures are constructed beneficially in this respect.

At this place one can add that of course it is advantageous for all embodiments according to the present invention to cover the thermal opening e.g. by a glass cover in order to reduce the heat reflection/reemission.

On the other hand, it is the case that by shaping the absorber space (here principally the height thereof or, as seen in the direction of the rays 4, the depth thereof) the person skilled in the art can achieve the enlargement of the heat-exchanging surface. For example, it is the case that the entire inner surface of the pipelines 26 of the heat-exchanger arrangement is used as heat-exchanging surface. Although only one side of the pipelines 26 is irradiated by the radiation 4, the pipelines 26 are heated virtually evenly all the way round by the conduction of heat in the material of the pipelines 26 (for example a good heat-conducting material such as copper or a suitable alloy, conducting heat well at higher temperatures), so that the heat-exchanging surface is correspondingly large. A large heat-exchanging surface is used for the efficient heat transfer to the heat-transporting fluid, so that a local overheating of the heat-exchanging surface can be substantially prevented.

Here, mention may be made of the fact that according to the insight of the applicant, in conventional absorber pipes, at the end region (region of high temperature of the fluid), the walls heated by the radiation often overheat severely with the consequence that the reflection is massively increased. The reason for this lies in the longitudinal flow of the fluid to be heated, which is already strongly heated itself in the high-temperature region of the conventional absorber pipe and the heat-exchanging walls, thus during the short time in which it flows through the end region, the walls of the end region can no longer cool sufficiently. (An increase of the mass flow is not possible, as the same must reach its set point temperature T_A with a given heat input by means of the reflected radiation 4; were the mass flow to be increased, this temperature could no longer be reached).

As a result, it is the case that although in the case of the absorber arrangement according to the invention, a heat reflection or reemission corresponding to the outlet temperature T_A prevails due to the thermal opening 35, as, due to the transverse flow principle, overheating occurs scarcely or only to a small extent, the energy losses in the absorber arrangement according to the invention are, all things considered, lower than in the case of the conventional absorber pipe. Accordingly, the absorber arrangement can be realised in virtually any desired length L, without this having negative consequences with regards to the heat radiation. In addition, in comparison with a conventional absorber pipe, even the heat reflection corresponding to the outlet temperature T_A, as due to the geometry of the absorber pipe, relevant parts of the heat-reflecting or reemitting walls are kept cool.

It follows that according to the invention, the relevant wall regions of the absorber pipe located close to the thermal opening remain cooler and an overheating of the heat-exchanging surfaces is substantially reduced than in the case of a conventional absorber pipe.

At this point, it may also be added that with the term “thermal opening”, depending on the design of the absorber pipe, is designated as a physical opening for the absorber space according to FIG. 2. The term “thermal opening” also comprises a physically closed region in the case of other designs of the absorber space, which region is designed for the passage of heat of the concentrated solar radiation, wherein for example, by means of suitable coatings at the location of the heat irradiation, a reflection of the heat can be minimised. Designs of this type are known to the person skilled in the art. Nonetheless, it is necessarily the case, that at the location of the thermal opening, ultimately it is not possible to achieve good insulation, thus the corresponding relevant heat losses due to heat reflection/reemission must be accepted.

Further, it may be added that the absorber arrangement according to the invention can be used in a trough collector only a short distance from the edge thereof, for example after the fluid has reached a temperature of 100° C. or somewhat more. An absorber arrangement according to the present invention extending over the entire length of the trough collector is preferred however.

Here, it may be mentioned that the pipelines 26 of the heat-exchanger arrangement 29 can replace the walls of the absorber space 30 at least to some extent, with the advantage that as a result, the pipelines 26 are directly irradiated, that is to say the heat transfer to the heat-transporting fluid is only impeded minimally. It is likewise compliant with the invention if at least sections of the wall of the at least one absorber space are formed by the heat exchanger or the pipelines thereof. Further, it is compliant with the invention that the heat exchanger has mutually adjacent line sections for the fluid, which form at least one wall section for the at least one absorber space.

In the embodiment illustrated in FIG. 3, the absorber space may for example be formed by lines 42 of the heat-exchanger arrangement, as the same run in mutually adjacent windings and thus preferably completely envelop the interior of the absorber space.

FIG. 3 shows a further embodiment of the absorber arrangement 40 according to the present invention, which essentially corresponds to that of FIG. 2, except for the construction of the heat-exchanger arrangement 41, whose lines, which are constructed as pipelines 42, are here laid in small loops, that is to say are constructed longer in each case. In spite of these loops running in the longitudinal direction, the heat-exchanging fluid flows through the heat-exchanger arrangement 41 in transverse flow with respect to the longitudinal direction L. The tube 24 (FIG. 2) is omitted in the FIG. 3, in order to make it possible to see the pipelines 42.

Longer pipelines 42 have the advantage that the heat-exchanging surface for the partial flow of the fluid is enlarged, but the disadvantage that the pressure drop in the pipeline 42 is larger. In an actual case, the person skilled in the art can determine the flow and thermodynamic design of the pipelines 42. Fundamentally any suitable conveying of the heat-transporting fluid by means of the heat-exchanger arrangement complies with the invention, as long as the conveying takes place in the main direction thereof transversely to the length L by means of the heat-exchanger arrangement in such a manner that the fluid is heated during operation from an inlet temperature to the operating temperature in the transverse flow and achieves the drain arrangement. Likewise, generally any suitable construction of lines in the heat-exchanger arrangement according to the invention, which is used for passing the fluid, is compliant with the invention.

The small flow arrows 44 show the direction of flow of the heat transporting fluid.

FIG. 4 shows yet a further embodiment of an absorber arrangement 50 according to the present invention, which essentially corresponds to that of FIG. 2, except in turn for the construction of the heat-exchanger arrangement 51, whose lines, which are constructed as pipelines 52, are here laid in small coils 53, that is to say are constructed even longer in each case. The coils 53 are only indicated schematically in the Figure and illustrated in detail in FIG. 5.

The coils 53 formed from the pipelines 52 are open towards the bottom and as a result form absorber spaces 54, as a space section is enclosed by them. As a result, the heat-exchanging surface for this room section and thus also over the length of the absorber arrangement 50 gets substantially larger, with the advantages as mentioned above for FIG. 1. The regions of the coils 53 open at the bottom form thermal openings 59.

The absorber spaces 54 lie in a row 55 due to the shown arrangement of the coils 53.

In FIG. 4 also, the pipeline 24 has been omitted so as not to overload the figure, so that the view onto the coils 53 becomes clear.

The result is that the absorber arrangement 50 in the embodiment illustrated in the figure is constructed in such a manner that the supply arrangement and the drain arrangement have a supply pipe 23, 24 and a drain pipe 25, wherein the pipes 23, 24, 25 run parallel to one another and the here numerous absorber spaces each formed by a coil 53 are arranged between these pipes 23 to 25 and extend over the length of the absorber arrangement 50.

FIG. 5 shows a view of one of the coils 53 only indicated schematically in FIG. 4, formed from the windings of a line of the heat-exchanger arrangement 51 according to the invention, here constructed as a pipeline 52. The coil 53 here has an axis of symmetry 55 and encloses an absorber space 54 for the incident radiation 4, wherein the end of the coil 53 which is open at the bottom forms a thermal opening 59. Heat-transporting medium at the inlet temperature T_E flows through the connecting piece 57 of the pipeline 52 into the coil 53, flows through the same and is passed through the end section 58 of the pipeline 52 at the outlet temperature T_A into a collecting line, here constructed as pipeline 25.

Together with FIG. 4, an absorber arrangement results, in which the supply arrangement and the drain arrangement have a supply pipe 23, 24 and a drain pipe 25, wherein the pipes 23, 24, 25 run parallel to one another and a number of absorber spaces 54 is provided, which are arranged in at least one row 55 running between these pipes 23, 24, 25, wherein the at least one row 55 extends over the length of the pipes. Thus, advantageously generally a plurality of absorber spaces (any desired configuration) are provided, which are connected parallel between the supply and the drain arrangements.

FIG. 6 shows a cross section through a trough collector 60, with an absorber arrangement 61 according to the invention, wherein two concentrators 62 and 63 are provided, which are for example configured according to WO 2010/037 243 (which is here included by reference in the present application). The framework of the trough collector 60 is for example constructed in accordance with WO 2009/135 330.

In accordance with the two concentrators 62, 63, the absorber arrangement 61 has at least two absorber spaces 64 and 65 which extend over the length L of the absorber arrangement 61. However, it is also compliant with the invention to provide two rows of absorber spaces arranged one behind the other, analogously to the embodiments according to FIGS. 3 to 5, in which absorber spaces arranged in rows are illustrated. At this point, it may be added that it is likewise compliant with the invention to provide more than two rows of absorber spaces in an absorber arrangement in the case of trough collectors with even more mutually adjacent concentrators.

FIG. 7 shows a cross section through the absorber arrangement 61 of FIG. 6. Illustrated is a line of a supply arrangement for heat-transporting fluid, constructed as pipeline 72, a heat-exchanger arrangement 74, here with two rows, and also a pipeline of a drain arrangement for the heat-transporting fluid, which is here constructed as a collecting line and is provided with insulation 70. In the embodiment illustrated, the heat-exchanger arrangement 74 has two rows 75 of spirals 53 arranged one behind the other, as illustrated in FIG. 5. The fluid passes through the line 72 at the inlet temperature T_E to the connecting pieces 57 and as a result into each coil 53, passes through the same and leaves the same via the end sections 58 of the pipeline 52 at the outlet temperature T_A and thus passes into the pipeline 25 of the drain arrangement. Preferably, there are secondary concentrators 73 known to the person skilled in the art as trumpets, which run along the thermal openings 59 over the length L of the absorber arrangement 61 in a suitable manner and thus concentrate the radiation already concentrated by the concentrators 62, 63 in the transverse direction of the trough collector a second time in the transverse direction, which makes it possible to reduce the width of the thermal openings.

Frame and structure elements 71 support the arrangement shown in the figure and can be constructed suitably in an actual case by the person skilled in the art.

In the case of an embodiment not illustrated in the figures, a number of absorber spaces lying one behind the other in a row is provided over the length of the absorber arrangement, which absorber spaces are arranged separated from one another at a distance from one another. Such an embodiment is advantageous if the radiation reflected by at least one concentrator (FIG. 1) or by a plurality of concentrators 62, 63 (FIG. 6) is concentrated longitudinally upstream of the absorber arrangement by a further arrangement of longitudinal concentrators, so that instead of a focal line region, a number of focal point regions (wherein one or a plurality of longitudinally extending rows of focal point regions are possible) are present with greater concentration.

Coils modified compared to the coils 53 shown in FIG. 5 are likewise compliant with the invention. These may for example form an elliptical or polygonal absorber space instead of a round one, or be terminated at the wall opposite the thermal opening with a simple lid in the place of the coils of the pipe 52 shown in FIG. 5. (Likewise, the absorber spaces may for example consist of one box in each case in the place of the spaces formed by lines).

Likewise compliant with the invention are coils, the axis of symmetry of which is inclined with respect to the thermal opening (and not perpendicular according to the illustration in FIG. 5), with the advantage that such coils are advantageous for a skew angle range. The skew angle is known as such to the person skilled in the art and designates the angle at which the sun falls onto the concentrator orientated towards it.

In summary, it is the case that according to the invention, the heat-exchanger arrangement and thus the at least one absorber space can be adapted and configured in terms of design in accordance with the thermodynamic requirements present in the actual case, but the heat-exchanging fluid is heated in the transverse flow to operating temperature, i.e. to the outlet temperature T_A, so that the drain arrangement is fed fluid at the outlet temperature A_T at the length L thereof. The person skilled in the art can combine the features explained in the above-described various embodiments depending on the requirements in the actual case, as these are not restricted to the respectively shown embodiments. Likewise, the heat-exchanger arrangement may not only be formed by pipelines, but rather also by means of another suitable construction.

Finally, it is advantageous for reasons of pressure supply and according to a further embodiment of the invention to segment the supply arrangement, wherein each segment has a connection for a fluid source. As a result, energy losses on account of the pressure drop in a long line are minimised.

Claims

1. An elongated absorber arrangement for a trough collector, which is subjected to concentrated radiation over its length during operation, with means for transporting heat-transporting fluid through the absorber arrangement, the absorber arrangement comprising: at least one fluid-free absorber space for concentrated radiation which has a thermal opening leading into its interior and walls for absorption of the heat incident into it, and the means for transporting the fluid have a supply arrangement and a drain arrangement which are operatively connected to one another by means of a heat-exchanger arrangement through which fluid flows; andwherein the same extends along the length of the absorber arrangement, is constructed for the throughflow of the fluid in transverse flow for the length of the absorber arrangement and is thermally connected to the at least one absorber space in such a manner that the fluid is heated during operation in transverse flow from an inlet temperature TE to the operating temperature TA and reaches the drain arrangement at this temperature.

2. The elongated absorber arrangement according to claim 1, wherein a number of absorber spaces lying one behind the other in a row are provided over the length of the absorber arrangement, which absorber spaces are directly adjacent to one another.

3. The elongated absorber arrangement according to claim 1, wherein a number of absorber spaces lying one behind the other in a row are provided over the length of the absorber arrangement, which absorber spaces are arranged separated from one another at a distance from one another.

4. The elongated absorber arrangement according to claim 1, wherein at least sections of the wall of the at least one absorber space are formed by the heat-exchanger arrangement.

5. The elongated absorber arrangement according to claim 1, wherein the heat-exchanger arrangement has mutually adjacent line sections for the fluid, which form at least one wall section for the at least one absorber space.

6. The elongated absorber arrangement according to claim 2, wherein an absorber space is formed by a line of the heat-exchanger arrangement, which run in mutually adjacent windings and thus preferably completely envelop the interior of the absorber space.

7. The elongated absorber arrangement according to claim 1, wherein the drain arrangement has a collecting line, extending over the length of the absorber arrangement, for heated fluid supplied to it over its length from the heat-exchanger arrangement, wherein the collecting line is thermally insulated over its length through to the openings for the supply of the heated fluid.

8. The elongated absorber arrangement according to claim 1, wherein the supply arrangement has a feed line for the fluid to be heated and supplied to the heat-exchanger arrangement over its length, which feed line extends over the length of the absorber arrangement, wherein the feed line is thermally insulated over its length through to the openings for the supply of the heated fluid.

9. The elongated absorber arrangement according to claim 1, wherein the supply arrangement and the drain arrangement have a supply pipe and a drain pipe, wherein the pipes run parallel to one another and the at least one absorber space is arranged between such pipes and preferably extends over the entire length of the absorber arrangement.

10. The elongated absorber arrangement according to claim 1, wherein the supply arrangement and the drain arrangement have a supply pipe and a drain pipe, wherein the pipes run parallel to one another and a number of absorber spaces is provided, which are arranged in at least one row running between such pipes, wherein the at least one row preferably extends over the entire length of the pipes.

11. The elongated absorber arrangement according to claim 1, wherein a plurality of absorber spaces are provided, which are connected parallel between the supply and the drain arrangements.

12. The elongated absorber arrangement according to claim 1, wherein the supply arrangement has a supply pipe which is segmented and wherein each segment has a connection for a source of heat-transporting fluid.

13. The elongated absorber arrangement according to claim 1, wherein the length thereof is greater than 100 m, preferably greater than 150 m and particularly preferably 200 m or more.

14. The elongated absorber arrangement according to claim 1, wherein secondary concentrators are provided, which concentrate the incident radiation in the longitudinal direction of the absorber arrangement upstream of the at least one absorber space.