EP3622227A1

EP3622227A1 - Method for operating a receiver and receiver for carrying out the method

Info

Publication number: EP3622227A1
Application number: EP18726716.6A
Authority: EP
Inventors: Gianluca AMBROSETTI; Philipp GOOD
Original assignee: Synhelion SA
Current assignee: Synhelion SA
Priority date: 2017-05-10
Filing date: 2018-05-07
Publication date: 2020-03-18
Also published as: US20220090825A1; AU2018266741B2; CH713765A1; AU2018266741A1; MA50762A; MA49301A; CN110720017A; CL2019003147A1; CH713773A2

Abstract

The receiver (25) according to the invention is provided with a heating region for heating a heat-carrying medium, having an optical opening (3) for sunlight and an absorber (27) arranged in the path of the incident sunlight (4) and absorbing said sunlight, and with a transport assembly for transporting the medium through the heating region, wherein the absorber (27) is designed as a black-body radiation assembly with reduced convection, and the transport assembly is designed for transporting a gas as the heat-carrying medium. In this way, the receiver can be designed to be simpler and more reliable.

Description

Method for operating a receiver and receiver for execution

of the procedure

The present invention relates to a method for operating a receiver and a receiver for carrying out the method according to the preamble of claims 1 and 6, and to a method for producing a receiver according to the preamble of claim 18.

Receivers are used in solar power plants. They capture the concentrated solar radiation and thereby heat a heat-transporting medium, via which the heat obtained is utilized in a subsequent technical process, be it via the conversion into mechanical work, for example by the drive of turbines, for the execution of heat-requiring processes in industry or for heating, for example district heating of inhabited areas. In solar tower power plants, receivers designed essentially as tube bundles are used, which are suitable for temperatures of up to 600 ° C. and concentrations of 600 suns. For higher temperatures predominantly spatially trained receivers are used, which are designed for concentrations of 600 suns, 1000 suns or more. Such temperatures are typically above 600 ° C, ranging from 800 ° C to 1000 ° C and above, and may reach the range of 1200 ° C to 1500 ° C in the near future. Such receivers can be used, but on a smaller scale, even with Dish concentrators. In the present case, receivers are referred to as spatial receivers whose dimensions are comparably large in all three dimensions, in contrast to tubular receivers which are used in conjunction with trough or gutter collectors. Such tubular receivers have a dimension, the length, which is a multiple, in the range of ten or a hundred times or more of the cross-sectional dimensions width or height. Trough collector receivers are not designed for the above mentioned temperatures because the trough-shaped concentrator concentrates in two dimensions with respect to the receiver, but the field of heliostats in a tower power plant or a dish concentrator in three dimensions.

Such receivers are known to the person skilled in the art as volumetric receivers which are also suitable for solar tower power plants, with the required temperature being determined in such receivers. ren of more than 500 ° C, or more than 1000 ° C, for example, to reach 1200 ° C. However, the high operating temperatures lead to considerable design effort.

Volumetric receivers have an extensive (voluminous, hence the term "volumetric" Reciever) absorber structure, which may for example consist of a voluminous wire mesh or an open-porous ceramic foam. The concentrated solar radiation then penetrates into the interior of the (voluminous) absorber structure and is absorbed there. The heat-transporting medium, such as air or a suitable reaction partner for a subsequent reactor, is passed through the open-porous absorber structure and thus absorbs heat by means of forced convection at the open-porous absorber structure. The absorber structure can also consist of a tube structure, a staggered in depth lattice structure or a per se arbitrary structure with a large surface, which causes the convective heat transfer from the absorber structure to the heat-transporting medium when it flows through the absorber.

A volumetric receiver has become known, for example, from the REFOS project (Receiver for solar-hybrid gas turbine and combined cycle systems, R. Buck, M. Abele, J. K¸ngerger, T. Denk, P. Heller and E. Lüpfert, in Journal de Physique IV France 9 (1999)), which is described in more detail below in connection with FIG.

Such receivers have the disadvantage that the absorber structure can be complicated to produce and the flow through the absorber can become unstable, in particular due to an undesirable temperature distribution during operation. Accordingly, it is the object of the present invention to provide an improved receiver.

This object is achieved by the method having the characterizing features of claim 1 and the characterizing features of claim 6.

By virtue of the fact that, according to the method according to the invention, the selected heat-transporting gas is absorptive in the frequency bands of the infrared range, and the operating parameters are set in such a way that a considerable part of the heat increase is absorbed by Sorption takes place in the heat-transporting gas, a simplified concept of the receiver can be realized, since the heat transfer by convection takes place only reduced.

The fact that the absorption arrangement is designed as a black body radiation arrangement with reduced convection, simplifies the formation of the absorber, and thus construction and operation of the receiver, since the absorber no longer over its depth, the introduced via the solar radiation heat convectively to the heat-transporting gas must give up.

Preferred embodiments have the features of the dependent claims. The invention will be explained in more detail with reference to FIGS. It shows:

1a shows a receiver according to the prior art,

1 b shows schematically a diagram with the temperature profile in the receiver of FIG.

2 schematically shows a receiver according to the present invention in longitudinal section,

3 shows schematically a diagram with the temperature profile in the receiver of FIG. 2,

4 shows schematically an embodiment of the receiver according to the invention,

5 shows schematically a further embodiment of the receiver according to the invention,

6a and 6b are diagrams with the temperature profile in a receiver according to the invention,

Fig. 7a-c diagrams with the efficiency and the temperature of the absorbent surface in a receiver according to the invention

8 shows the steps of an inventive operating method for a receiver, and 9 shows the steps of a manufacturing method for a receiver according to the invention.

FIG. 1 a shows a test arrangement for a volumetric receiver 1 according to the REFOS project, with a heating area 2 for heating a heat-transporting medium, in this case air, which has an opening 3 designed as a quartz window for the radiation of the sun or sunlight 4 and arranged in the path of the incident radiation 4 behind the quartz window 3, this radiation 4 absorbing absorber 5. A transport assembly 6 for the transport of the heat-transporting medium through the heating area 2 has in the embodiment shown an inlet 7, through which the medium with a Inlet temperature T _in enters the receiver 1 and an outlet 8, through which it leaves this with the outlet temperature T _out .

Via edge-side channels 9 of the transport arrangement 6, the air at the inlet temperature T _{in is conducted} to the front side of the receiver 1, where it passes through suitably formed openings 10 into a distribution space 11 located in front of the absorber 5, then distributes the absorber 5 flows through it, thereby convectively heated, and finally passes with the temperature T _out in a collecting space 13 and from there into the outlet 8, through which it leaves the receiver 1. The quartz window 3 is arched towards the inside, so that the receiver 1 can be operated at elevated pressure, so that the heated air can be supplied under pressure to a downstream consumer, for example a turbine.

The constructed as a volumetric absorber, space-saving the contour of the quartz window 3 tracked absorber 5 has a number of layers of a fine wire mesh, in which the sunlight 4 can penetrate deeply, so that the absorber 5 is heated over its entire depth and thus the flowing through it Air convectively heated to T _out . As mentioned above, in other embodiments, a conventional absorber can be formed from an open-pore ceramic foam or other arrangement having a very large surface area compared to the volume of air in the absorber to achieve the required convective heat transfer.

An insulation 12 surrounds the receiver 1, to which in front of its optical aperture 3, a secondary concentrator omitted for relief of the figure is connected, which controls the flow the solar radiation 4 concentrated to the quartz window 3. To relieve the figure, a control for the receiver 1 and the transport arrangement 6 is further omitted, via which the operation of the receiver 1 or the supply and removal of air is suitably regulated, as is known in the art. By means of a receiver in the manner of the REFOS receiver shown, an exit temperature T _out of 800 ° C., with a ceramic absorber of 1000 ° C., can be achieved.

FIG. 1b shows a diagram 15 with a temperature curve 16 which, in conjunction with FIG. 1 a, schematically shows the temperature profile of the air flowing through the receiver 1. In section A from the inlet 7 to the end of the peripheral channels 9, a small convective heating of the air takes place from T _in to Ti (part 17 of the temperature curve 16). In section B, during the passage of the air through the openings 10 in the absorber 5, a first, relevant and convective heating of Ti to T _{2 takes place} (part 18 of the temperature curve 16). In section C, ie in the distribution space 11, the air heats up absorptively, but only slightly, since air as a gas mixture contains, for example, a small amount of CO ₂ (or another gas) which absorbs in the infrared, but is otherwise substantially transparent to infrared radiation (Part 19 of the temperature curve 16). Finally, the air in section D flows through the absorber 5, where it is convectively heated to the temperature T ₄ , which corresponds to the outlet temperature T _out (part 20 of the temperature curve 16). In section E, the air passes through the collecting space 13 in the outlet 8, which in turn results in a small absorptive increase in temperature by the infrared-absorbing gas component. The temperature jump from T _in to T _out is essentially convective.

Figure 2 shows schematically an embodiment of an inventive, designed as a spatial receiver receiver 25, with a heating region 26, which has an opening 3 for the radiation of the sun, such as a quartz window, and a plate-shaped absorber 27, wherein between the quartz window 3 and the Absorber 27, an absorption space 28 is provided, which is traversed by the heat-carrying medium according to the arrows from right to left, ie against the absorber 27, respectively. For this purpose, the transport device 29 arranged around the quartz window 3 around inlet nozzle 30 for heat-transporting medium, which lead into the absorption space 28, and a central outlet 31 behind the absorber 27. To relieve the figure here as well as in the following figures, the insulation omitted from the receiver. According to the invention, the absorber 27 is designed as a black body radiation arrangement, ie it has a surface 27 'which absorbs this radiation and is arranged in the path of the incident sunlight or the incident solar radiation 4 and which is designed such that it forms on the surface 27 'incident solar radiation 4 is operatively heated and then emits infrared radiation into the absorber chamber 28 via its surface 27'.

In this way, the absorber 27 transfers its heat output to a considerable extent in the form of infrared radiation into the absorber space 28, where the heat-transporting medium already heats up largely or predominantly absorptively with respect to T _out before it reaches it.

A real structure only radiates approximately as the ideal black body does. In the present case, a "black body radiation arrangement" is understood to mean that the incident solar radiation 4 is absorbed to the greatest possible extent on the surface of the absorber (ie basically penetrates only slightly into the absorber, in contrast to the known volumetric absorbers) that this surface heats up high and thereby radiates in the manner of a black body with the relevant high temperature in the absorber space 28, with respect to the solar radiation other frequency spectrum. The majority of blackbody radiation emitted into the absorber space 28 is at temperatures of the absorber 27 to 2000 ° K (or even higher) in the infrared region, i. as mentioned, in relation to the visible light lower frequencies.

In other words, it is the case that the absorber according to the invention is designed to be cooled via its black body radiation so that the ratio χ can be achieved (see the description below).

An elaborate, in particular for volumetric eceiver provided, staggered in depth absorber structure that absorbs about their depth incident solar radiation or radiation of the sun according to their depth by being at least partially scattered in the interior and increasingly absorbed after multiple reflection, thus disappears. This eliminates the often occurring with such absorber structures, complex thermal problems. Thus, the absorber 27 is further preferably formed konvektionsarm, ie, for example, easily flowed through, without increased convective properties for the heat exchange of importance. This also eliminates the need for training for maximized convection of the medium flowing through, ie the structure required for the most efficient heat exchanger with large surface area which, compared to the volume of the heat exchanging medium, is costly and expensive to produce at high efficiency and in operation a significant pressure drop of the medium flowing through the result, which in turn is detrimental to the efficiency of the corresponding receiver.

At this point it should be noted that a certain convective heat transfer at the absorber 27 by contact with the heat exchange medium is of course inevitable, especially in the illustrated embodiment of Figure 2, since it forms a wall portion of the absorption space 28 there. The corresponding convective heat transfer to the heat-transporting gas is in itself, as any heat transfer, quite welcome - however, the outlet temperature T _out to a substantial or predominant part (see below) based on absorption and so a simplified design of the receiver 25 allow. The simplified structure of the absorber 27 opens, among other things, as mentioned above, the possibility for cost-effective production (low-cost receiver for high temperatures) and also a more stable operation, for example in thermal terms (temperature distribution over the absorber 27), resulting in an improved Industrial suitability of the receiver leads.

According to the invention, a receiver is provided with a heating area for the heating of a heat-transporting medium, which has an opening for the radiation of the sun and an absorber arranged in the path of the incident radiation of the sun, with a transport arrangement for the transport of the medium through the heating region, wherein an absorption space for heating the heat-transporting medium is provided outside the absorber and the absorber is designed as a convection-poor blackbody radiation arrangement and the transport arrangement for the transport of a gas as a heat-transporting medium. In this case, the absorber designed for the flow through of the heat-transporting gas, which is designed as a convection-poor blackbody radiation arrangement, is preferably formed, and more preferably lies opposite the optical opening 3. Preferably, as shown in FIG. 2, the absorber space 28 is provided between the opening 3 for the radiation of the sun and the absorber 27, wherein the ratio χ is the ratio of the temperature increase (T ₃ -T ₂ ) by absorption of the radiation of the absorber 27 in this absorber space 28 to the total temperature increase (T ₄ - T ₂ ) by the absorption and convection at the absorber 27, after which the gas has passed this. The gas has then passed through the absorber 27 when it has either just passed through the absorber 27 and thus reaches the collecting space 33, or if it has just been taken sideways at the location of the absorber 27 (for example through openings 92 '' or 93 ''). according to Figure 5), wherein of course in a specific embodiment, both options can be provided simultaneously.

In another embodiment, not shown in the figure, the collecting space 33, which is located on the back of the absorber 27, formed as a further absorber space. In the case of an at least partially gas-tight absorber (see below), gas is passed around the absorber to a rear side of the absorber and then away from it.

Then the already absorptive and convective heated, heat-transporting gas flows through this further absorption space and heats up additionally, absorptively and convectively, preferably according to the invention with a temperature ratio χ> 0.3. This ultimately makes it possible to enlarge the radiating surface 27 'and thus to optimize the absorptive heat transfer.

Thus, the heating area has two absorber spaces with a common absorber, wherein the ratio χ is provided for one or both of the absorber rooms. As a heat-transporting medium according to the invention, an infrared-absorbing gas or gas mixture is further used, which absorbs in frequency bands of the infrared range. Such gases are for example heteropolar gases, preferably C0 ₂ , water vapor, CH ₄ , NH ₃ , CO, S0 ₂ , S0 ₃ , HCl, NO, and N0 ₂ , or a mixture thereof, such as a mixture of water vapor and C0 ₂ . When using such gases ultimately results by the eceiver 25 usable or used greenhouse effect, since these gases are highly transparent to the visible light, which thus substantially reaches the absorber 27, but for the infrared radiation of the absorber are little to no transparent, so they so in front of the absorber 27 absorptively with respect to T _out to a considerable or predominant degree. It should be noted here that real gases do not absorb visible light or infrared radiation uniformly over all frequencies or are transparent to them, but vary in strength, especially in frequency bands specific for a particular gas. In addition, the absorption decreases with the distance from the radiation source. This is spoken above with regard to the absorption or transparency of radiation from "highly transparent" or from "little to little transparent".

It should also be noted that, of course, the radiation of the sun has a proportion of infrared frequency bands, as far as they pass through the atmosphere to the earth's surface. Thanks to the formation of the heating region 26 such that it is little to almost transparent for infrared frequencies, this (comparatively small) fraction contributes so far directly, without detour via the absorber 27, according to the invention most efficiently for heating the heat-transporting fluid. This is in contrast to conventional receivers, in which the infrared portion of the solar radiation substantially heats the absorber and is then given off predominantly convectively to the heat-transporting fluid.

The absorber according to the invention may be formed as a perforated plate, preferably as a double perforated plate or as a simple, flat lattice structure. In the case of the perforated plate, a hole pattern is distributed over the extent thereof, so that the heat-transporting gas can easily flow through, but enough or as much as possible is given to the surface of the perforated plate for absorbing the incident solar radiation and the infrared reflection into the absorber space. In addition, the hole pattern can be designed for easy flow, since the need for convection is eliminated, and reduced flow resistance is advantageous. The person skilled in the art can easily optimally determine the hole pattern in the specific case. Likewise, in the case of a lattice structure or double perforated plate with two parallel plates, in which case the holes of one plate relative to those of the other plate are offset from each other, such that despite konvekti- onsarmem passage of the heat exchange gas the absorption space as continuous as possible , radiating surface of the absorber is facing. In this case, the gas passed through the absorber. Alternatively, the absorber can also be made gas-tight, in which case the gas, as shown, for example, in FIG. 5, flows laterally out of the absorber chamber 26. Then the gas is guided past the absorber. The skilled person can provide a mixed form in the specific case, so that a part of the gas flows through the absorber and a part flows past him. The absorber then has at least partially a gas-tight surface and is preferably plate-shaped (a completely gastight surface is present when the gas is conducted past the absorber).

A suitable material for the absorber has both a high degree of absorption of solar radiation and a high emissivity of infrared radiation, which - if necessary - with suitable texturing of the surface 27 'such as V-grooves, in the surface in or outstanding pyramids, or other radiation traps can be additionally increased. In addition, high temperature (change) and corrosion resistance (for example, oxidation by steam or CO 2 at high temperatures) are assumed. Suitable materials are both high-temperature ceramics such as silicon carbide (SiC) and refractory materials that the expert in a particular case, among others, with regard to the intended temperature range, can select.

The result is an inventive eceiver with a heating range for the heating of a heat-transporting medium having an opening for the radiation of the sun, and arranged in the path of the incident radiation of the sun, these absorbing absorber, with a transport arrangement for the Transporting the medium through the heating area, characterized in that an absorber space is further provided for heating the heat-transporting medium and the absorber is designed as a radiation arrangement acting in the absorber space and the transport arrangement for transporting a gas as heat-transporting medium, wherein the heat-transporting medium is substantially an absorbing gas in frequency bands of the infrared range, and the absorber space cooperating with the absorber is dimensioned such that, in operation, the ratio χ of the temperature increase (T ₃ -T ₂ ) of the one in frequency bands of the infrared region absorbing, heat-transporting gas by absorption in the absorber space against the temperature increase (T ₄ -T ₂ ) by the absorption and the convection at the absorber,> 0.3. In this case, according to the choice of the person skilled in the specific case of the receiver according to the invention can be designed such that the temperature during transport through the heating area by absorption of the radiation of the absorber increases such that the ratio χ of the temperature increase (T ₃ - T ₂ ) by absorption of the Radiation of the absorber against the total increase in temperature (T ₄ -T ₂ ) by the absorption of the radiation of the absorber and convection at the absorber is> 0.3.

FIG. 3 shows a diagram 40 with a temperature curve 41 which, in conjunction with FIG. 2, shows schematically the temperature profile of the gas flowing through the receiver 25.

In section F, heating of the infrared-absorbing, heat-transporting gas from T _in to Ti is shown by the part 42 of the temperature curve, in the case where in the embodiment of the receiver 25 shown in FIG. 2 the infrared-absorbing gas is the same as in the receiver 1 Air (Figure 1) is also the absorption space 28 along the end to be transported (which is not mandatory). In section G, there is a small convective heating of the air from Ti to T ₂ (part 43 of the temperature curve 41) due to the passage of the gas through the inlet ports 30.

In section H, the infrared-absorbing gas flows through the absorption space 28 and heats up absorptively through the infrared radiation 32 of the absorber 27 (here with the infrared portion of the solar radiation) from T ₂ to T ₃ (part 44 of the temperature curve 41) flows through it in section I and thereby convectively heated from T ₃ to T ₄ (part 45 of the temperature curve 41). Finally, there is a further absorptive heating of the infrared-absorbing gas in section K of T ₄ to the outlet temperature T _out (part 46 of the temperature curve 41) while the gas is in the collecting space 33 and flows against the outlet 31. The temperature jump from T _in to T _out according to the invention results in a large or predominantly absorptive condition.

It can be seen from the representation of FIGS. 2 and 3 that the transport arrangement of the receiver preferably has an absorption space 28 in the flow direction before and a further absorption space (formed here as collecting space 33 in the flow direction behind the absorber 27. The expert sets in this particular case the operating parameters, usually starting from the desired or necessary outlet temperature T _out and given by using the heat from the receiver inlet temperature T _in. He also chooses the appropriate in this case infrared absorbing gas or gas mixture and sets the flow rate in the absorption chamber 28 fixed (which in turn may be dependent on the current solar radiation). Such and further operating parameters resulting in the specific case may depend on each other, with the result that the absorptive increase in temperature from T ₂ to T ₃ in section H of Figure 3, ie in the absorption space 28, in the specific case depending on the larger or smaller fails.

The Applicant has found that the advantages according to the invention are already relevant at a ratio χ of> 0.3, where

Ύ =

T ₄ -T ₂

i.e. indicates the ratio between the absorptive and total absorptive and convective heating of the heat transporting gas when the gas has passed to and through an infrared radiating absorber 27 (or to an outlet thereafter); this has happened. By suitable operation with the selected operating parameters, in other words by suitable design of the control of the receiver 25, the person skilled in the concrete case can achieve the inventive value of χ> 0.3.

The expert can, as mentioned, in the specific case, the ratio χ> 0.3 on the absorption of only the absorber radiation 32,55 or on the absorption of the absorber radiation including the absorption of the infrared portion of the absorption chamber 28, 57 (Figures 2 and 4) current solar radiation 4 relate.

It follows that, according to the invention, a gas absorbing in frequency bands of the infrared range is provided as the heat-transporting medium. Furthermore, according to the invention, an absorption space cooperating with the absorber is dimensioned such that, during operation, the ratio χ of the absorptive temperature increase (T ₃ -T ₂ ) of a heat-transporting gas absorbing in frequency bands of the infrared range in the absorption chamber compared with the total temperature increase (T ₄ - T ₂ ) by absorption and convection at the absorber> 0.3. Preferably, the heat exchanging gas flows through an absorber zone (absorption space 28) against an absorber (absorber 27), wherein it is absorptive in the absorber zone and also convectively heated by the absorber. A receiver can be constructed in several stages, ie heat heat-transfer medium gradually. According to the invention, at least one stage for absorptive / convective heating with the ratio χ of> 0.3 is then formed.

The heating area then preferably has two absorption spaces, the ratio χ being provided for one or both of the absorption spaces in conjunction with the absorber.

For a high efficiency of the inventive receiver is determinative that the radiated heat from the absorber as much as possible in the absorption space from the heat-transporting gas is absorbed (for example, not penetrating the gas and escapes through the opening for solar radiation as re-radiation from the receiver). A determining parameter here is the absorptivity a of the heat-transporting gas, which can be measured by experiments, calculated from spectral line values of molecular spectroscopic data bases (for example HITEMP2010), or approximately determined from emissivity diagrams according to the Hottel rule. If, under the current operating conditions of the receivers, in one embodiment a distance H between the absorber and the opening is such that 60% or more of the heat energy radiated by the absorber is absorbed by the heat-transporting gas in this spatial area, this results in a good efficiency of the receiver , which is designed to absorb the absorber heat. Particularly preferably, a height in said spatial region is such that 80% or more, particularly preferably 90% or more, of the radiated heat output of the absorber is absorbed by the heat-transporting gas.

It should be noted here that the absorber space certainly has an opening for the radiation of the sun and an absorber acting on it via its black body radiation, wherein, according to FIGS. 2 and 4, the absorber preferably lies opposite the opening. In principle, however, the absorber space can also not be cylindrical, but can be formed as desired, for example with recessed side walls, so that the opening is smaller than the absorber surface, which is advantageous in view of the unwanted reflection. In in such a case the radiation is concentrated in the aperture by a concentrator and diverges after the aperture so that the whole and larger absorber surface is illuminated. Then the absorber space may not have under the re-entrant walls, but below the opening a height such that in the affected space area (where this height is present) is an absorption in the above degree.

Since the absorptivity depends on the nature of the gas, its pressure and the temperature of the radiating absorber surface and that of the gas itself (Hottel's rule), the skilled person can determine the height as a function of the absorption-determining parameters: as mentioned, these are the type of the gas, its operating pressure, its temperature and the temperature of the absorber surface during operation, which determine insofar an operating state of the receiver.

This results in a preferred embodiment of the receiver according to the invention, in which the absorption space has a height above the absorber such that in an operating state of the receiver in this area 60% or more, preferably 80% or more, most preferably 90% or more of the radiated heat output of the absorber is absorbed by the heat-transporting gas. FIG. 4 shows a further embodiment of the receiver according to the invention. Shown is a section through a receiver 50, which corresponds to the Reciever 25 of Figure 2, but wherein the absorber 51 with its the optical opening 3 facing the absorbent surface 51 'has a projecting into the absorber chamber 57, preferably plate-shaped portion 54 which is located in the center of the absorber space 57 extends against the opening 3 and is aligned substantially parallel to the flow direction of the infrared-absorbing, heat-exchanging gas indicated by the arrows shown. The portion 54 substantially absorbs infrared radiation emitted by the absorbing surface 51 ', as far as it has not yet been absorbed by the gas flowing therealong, that is to say in particular radiation in those frequency bands for which the gas is less absorptive. As a result, it heats up and in turn represents a black body radiation arrangement which radiates the corresponding frequency spectrum as a whole to the temperature of the section 54 and in turn absorptively heats the passing-through heat-transporting gas. This results in an improved use of those frequencies of the radiation 55, which are absorbed only slightly by the gas, since these free introduce heat into section 54, which in turn radiates in all (infrared) frequencies. Section 54 represents a secondary absorber.

Such an arrangement can be made in larger dimensions, for example with a diameter of the absorber surface 51 'of 15.96 m and a length of the absorption rim 53 (absorber surface 51' to optical opening 3) of 15.96 m. Then, the receiver 50 is adapted to receive the flow of a large number (or all) heliostats of a tower power plant. It follows that the receiver 50 has an absorption space 57 and the absorber 51 projects with a section or secondary absorber 54 into this space, which is preferably plate-shaped.

In a further, not shown in the figure embodiment, a transparent for example for the visible spectrum of sunlight glass wall (borosilicate glass) can be provided as Sekundärabsorber, approximately in the middle between the absorber surface 51 'and the optical opening 3 (Figure 4) parallel to Absorber surface 51 'is arranged and passages, for example in the manner of a perforated plate, for the heat-transporting gas. Again, the glass wall is heated by the infrared radiation of the absorber surface 51 ', or by their not yet absorbed by the gas frequency components and radiates even in the nature of the black body in both directions, namely both the optical aperture and against the absorber. In a concrete case, the person skilled in the art can design the glass plate in such a way that for the section of the absorption space between the glass plate and the optical opening and its associated glass plate and also for the section of the absorption space between the glass plate and the absorber with the absorber assigned to it, the ratio χ of> 0.3. According to the invention, this results in a receiver which has another secondary absorber designed as a black body radiation arrangement with reduced convection in an absorption space located in front of the absorber, which is arranged and designed such that it can be heated by the infrared radiation of the absorber. FIG. 5 schematically shows a cross section through a further embodiment of a receiver such as that of FIG. 2. The sun's rays 4 fall through a window of, for example, quartz glass 3 onto the absorber 27, whose radiating surface 27 'surrounds the gas flowing through the absorption space 26 heated, the temperature of which increases from the window 3 to the absorber 27 towards. Accordingly, the gas via openings 91 to 91 "'in the cylindrical wall of the receiver 90 can be removed at different temperatures. The arrows indicate the direction of flow of the heat-transporting gas, wherein the arrows at the openings 91 to 91 "are drawn longer correspondingly to the rising temperature Alternatively or together with the openings 91 to 91"', a line protruding into the absorption space 26 93 are provided for the gas, which then feeds via openings 92 to 92 "'gas at the prevailing at the location of the openings 92 to 92''temperatures. This is especially advantageous if the receiver 90 supplies a downstream process which proceeds at different temperature stages with heat. Heat-transporting gas can then be conducted back to the receiver at likewise different temperatures from this process, so that further feed lines for the heat-transporting gas into the absorption space 26 are more preferably in the region of the openings 91 to 91 '' and 92 to 92 '' of the receiver 90 (which are omitted here to relieve the figure). The result is a receiver in which the transport arrangement comprises one or more lines 91 to 91 '' and 92 to 92 '' for heat-transporting gas connected to an absorber space 26, which are arranged in such a way that gas which is partially heated is taken from the absorber space 26 and / or or divergently heated gas can be supplied at a location at which substantially the temperature of the gas in the absorber space 26 corresponds to the temperature of the partially heated, supplied gas.

Such supply and discharge lines for partially heated gas can be provided on an absorptive receiver according to the invention, without having to modify its layout, in particular the absorber 27 - these lines can also be used or shut down without it being due to the different heat transfer requires a constructive modification.

The Applicant has found that a temperature ratio χ> 0.5 is particularly advantageous when divisionally heated gas is used, for example, if at an inlet temperature T _in of 1000 K and an outlet temperature T _out of 1800 K, the divider heated gas in the range of 1400 K, ie at half the temperature difference, lies: the temperature layer T = 1400 K is still in the absorber space 26 in the purely absorptive region and is correspondingly easily accessible, in the figure 5 through the openings 91 to 91 "or 92 to 92" , FIGS. 6a and 6b as well as FIGS. 7a and 7b show various operating parameters in a receiver according to FIG. 2 in accordance with a mathematical modeling of the receiver 25 of FIG. 2 of the Applicant. The system has been modeled using the most accurate method available today, namely "spectral line-by-line (LBL) photon Monte Carlo ray tracing", the absorption coefficients being derived from the HITEMP 2010 Spectroscopic Database. Modeled is a receiver whose absorption space has a diameter of 15.96 m and a height of 15.96 and the opening 3 has a diameter of 11.28 m. This results in an area of the absorbing surface 27 'of 200 m ² and an area of the opening 3 of 100 m ² . As a heat-transporting medium, water vapor was assumed, at a pressure of 1 bar, without windows in the opening 3. The radiation flux at the opening 3 is 200 kW / m ² and at the absorbing surface 27 '600 kW / m ² (which compared to Opening 3 has twice the area). The absorbent surface 27 'was assumed to be a radiating black body, and, in contrast to Figure 2, with a continuous flat and smooth surface, so that the heat-transporting medium in the manner of Figure 5 through openings 91 "' at the level of the absorber 27th is led away laterally from the absorber space 26.

Figures 6a and 6b show the temperature profile during operation of the receiver 20 (Figure 2) along its longitudinal axis, starting from the opening 3: on the vertical axis, the temperature is plotted in Kelvin, on the horizontal axis, the distance from the opening 3. The diagram 60, Figure 6a, shows a process with an inlet temperature T _in of l'OOO K and an outlet temperature T _out of 400 K. The diagram 65, Figure 6b, shows a process also with an inlet temperature T _in of l'OOO K, but an initial temperature T _out of 800 K.

Because of the heated in operation walls there is a temperature distribution in the heat transporting medium (here water vapor) with increased temperature at the edge of the absorber space 26, so that at a certain cross section in the absorber space 26 at the edge (on the wall) (temperature curves 61 and 66 ) the highest and in the middle, at the location of the axis of the cylindrical absorber space 26, the lowest temperatures (temperature curve 62 and 67, respectively) are present. The temperature curves 63 and 68 show the average temperature of the water vapor in the respective cross-section of the absorber space 26. FIGS. 6a and 6b show, together with a proof-of-concept for an absorptive receiver, the possible embodiment of such a receiver according to FIG. 5.

FIG. 7 a shows a diagram 70 for the efficiency of the receiver 20 (FIG. 2). On the horizontal axis, the outlet temperature T _{out is} plotted, assuming a constant inlet temperature T _in of l'OOO K. The curve 71 shows the efficiency of the receiver 20 as a function of the output temperature T _out . The reduction of the efficiency towards higher temperatures T _out is explained by the increased (loss) reverberation caused by the higher temperatures out of the opening 3 - despite the constant inlet temperature T _in of l'000 K, since a portion of the reversion from the interior of the absorber room (at elevated temperatures). The concept of the absorptive receiver accordingly has an efficiency that is equivalent to the conventional, convective receivers or even improved with increasing output temperature Tout. FIG. 7b shows a diagram 75 of the temperature of the absorbent surface 27 'as a function of the starting temperature T _out . Again, there is a temperature distribution with higher temperatures at the edges and a minimum temperature at the location of the axis of the cylindrical absorber space 26: The curve 76 shows the temperature at the edge of the absorbent surface 27 'and the curve 77 the temperature at its center. The curve 78 shows its average temperature. The decreasing temperature difference to the absorbing surface 27 'with higher T _{out is} explained by the fact that the energy radiation of the black body increases with the fourth power of its temperature - with a relatively small increase in temperature (here around 300 K), the heat-transporting medium is massively heated higher (here around 1000 K). The concept of the absorptive receiver therefore has considerable flexibility with regard to the intended temperature T _out : an absorber suitable for high temperatures can equally be used for different temperatures T _out , which is not the case with the convective absorbers of the prior art, and supports the concept of the apsorptive low-cost high-temperature receiver. According to the modeling used, the ratios shown in FIGS. 6a, b and 7a, b also apply to a receiver 20 (FIG. 2) with smaller dimensions but increased pressure in the heat-transporting medium. Figure 7c shows a diagram 80 for the efficiency of the receiver 20 (Figure 2), but with a window in the opening 3 and for different dimensions. It can be seen that the efficiency for the large dimensions of the receiver 20 according to the description of Figures 6a, b and 7a, b, s. the curve 82. Also visible is the efficiency for small dimensions (diameter and height of the absorber space 26 = 1.596 m, diameter of the window in the opening 3 = 1.128, corresponding to 1 m ² ), with a pressure in the heat-transporting gas of 10 bar, s. the curve 81. The slightly lower efficiency compared to Figure 7a is explained by the reduced due to the window flow on the absorbent surface of 554.4 kW / m ² instead of 600 kW / m ² .

According to the Applicant's knowledge, therefore, the dimensions of the receiver 20 and all the embodiments according to the invention of the absorptive receiver can be easily scaled, whereby for a comparably high degree of efficiency or comparable temperature ratios with a reduction of the dimensions the pressure must be increased in the same ratio, here e.g. at a reduction by a factor of 10, the pressure increases by a factor of 10. However, with higher pressure in the heat transporting gas, the efficiency tends to increase disproportionately. FIG. 7c shows the conditions for a pressure of 10 bar. In the specific case, the skilled person can provide the overpressure in a range between 2 and 20 bar, more preferably between 5 and 15 bar and most preferably, as mentioned above, of 10 bar.

In the simulated embodiments according to FIGS. 6a to 7c, χ is in a range of> 0.9 since the convection on the flat and smooth absorbing surface is very small. It should be noted that convection fundamentally cools the absorber somewhat, therefore it is suitable to lower the efficiency-reducing losses by re-radiation out of the opening 3, ie to increase the efficiency of the receiver. However, increased convection leads to increased pressure losses in the flowing gas (which in turn reduces the efficiency), and to increased construction costs of the absorber. In the concrete case, the person skilled in the art can determine the optimum ratio between absorption and convection, ie a specific value for τ ₃ -τ ₂

χ = (see the description of Figure 3) in a range χ> 0.3 set.

T ₄ - 2 According to the findings of the Applicant leads, as mentioned, already a value of χ = 0.3 to a simpler design of the inventive receiver, with an efficiency which corresponds to that of the known, formed on the principle of convection receiver (or higher).

Since for the most intense blackbody radiation in the absorption chamber high temperatures of the absorber, but also the side walls of the absorption space are advantageous, eliminating any coolant, especially cooling channels, as provided in receivers according to the prior art - either cooling channels in the walls, or the convection-ensuring cooling channels in the absorber. This results in a receiver in which the walls of the absorption space and / or the absorber are free of coolant, in particular cooling channels.

In another embodiment, not shown in the figures, the absorber is the same as in the receiver 25 (Figure 2) disposed opposite the optical opening 3 and forms a wall portion of the absorption space 28 (Figure 2). In contrast to the receiver 25, however, the absorber is not provided with flow-through openings for the heat-transporting medium, but instead is at least partially gas-tight, so that heated gas flows radially out of the absorption space at the level of the absorber. This simplifies the design of the absorber once again, the ratio χ can be increased to a value higher than 0.3.

The expert can optimize the embodiment according to Figure 2, or by combining this embodiment with other described features (additional portion 54 of the absorber 51 of Figure 4, glass plate according to the embodiment not shown in the figures, etc.) the value of the ratio χ of> 0.3 to> 0.4 or> 0.5 or> 0.6 or> 0.7 or even increase to> 0.8.

FIG. 8 shows the steps of a method for operating a preferred spatial receiver according to the present invention. In a first step 60, a suitable receiver is selected, for example with a structure according to FIG. 2, which has an absorber which can be heated by sunlight, against which gaseous, heat-transporting medium is guided by a transport device in order to heat it for the heat transport through the absorber , In a second step 61, a gas absorbing in the infrared range is selected as the heat-transporting gas, in particular a heteropolar gas or one of the gases CO ₂ , water vapor, CH ₄ , NH ₃ , CO, SO ₂ , SO ₃ , HCl, NO, and NO ₂ (Or a mixture of this gas), to absorb black body radiation of the absorber by absorption of the transported against the absorber gas before the absorber and so to heat the heat-transporting medium.

In a third step 62, the operating parameters of the receiver are set such that, during operation of the receiver, the ratio χ of the temperature increase of the heat-transporting medium by absorption in front of the absorber against the temperature increase by absorption and convection at the absorber is> 0.3.

In the fourth step 63, the receiver is put into operation and driven with the parameter χ> 0.3.

The result is a method for operating a receiver having a heating area for the heating of a heat-transporting medium, and a transport arrangement for the transport of the medium through the heating area, wherein in the heating area an opening for the radiation of the sun and in the path the absorbing radiation of the sun arranged, this absorbing absorber is provided, and wherein as the heat-transporting medium is provided in frequency bands of the infrared absorbing gas, and the operating parameters of the receiver set and the gas is selected such that its temperature during transport through the heating area (to the absorber) by absorption of radiation increases such that the ratio χ of the temperature increase (T ₃ -T ₂ ) by absorption of radiation against the total temperature increase (T ₄ -T ₂ ) by the absorption and convection at the absorber> 0 , 3 is. In one embodiment, the ratio χ> 0.3 relates to the absorption of only the absorber radiation, so that the temperature during transport through the heating region by absorption of the radiation of the absorber increases such that the ratio χ of the temperature increase (T3 - T2) by Absorption of the radiation of the absorber opposite the total increase in temperature (T4 - T2) by the absorption of the radiation of the absorber and convection at the absorber is> 0.3.

In a specific case, the person skilled in the art can calculate the ratio χ> 0.3 on the absorption of only the absorber radiation 32, 55 or on the absorption of the absorber radiation, including the absorption of the infrared portion by the absorption space 28, 57 (FIGS. 2 and 4). refer to current solar radiation 4.

Preferably, a heteropolar gas is selected as the absorbing gas, more preferably C0 ₂ , steam, CH ₄ or a mixture of these gases.

The person skilled in the art can then modify the process according to the invention such that the ratio χ is equal to or greater than 0.4, or 0.5 or preferably equal to or greater than 0.7, more preferably equal to or greater than 0.8.

In one embodiment, the method according to the invention can be embodied such that the gas is passed through the absorber. Alternatively it can be provided that the gas is guided past the absorber.

FIG. 9 shows the steps of a production method according to the invention for an eceiver, for example according to FIGS. 2 to 4, wherein in step 70 the absorber is designed as a black body radiation arrangement with reduced convection and correspondingly an absorber space interacting with the absorber is provided to absorb the heat to transfer the heat-transporting gas. Thereafter, in step 71, a gas absorbing in frequency bands of the infrared region is provided as a heat-transporting gas together with the dimensions of the absorber space so that a predetermined operating condition of the receiver can be defined in which the temperature increase of the heat-transporting gas by absorption (the blackbody (Infrared) radiation of the absorber and the infrared components of the sun compared to the temperature increase by absorption and convection at the absorber in a ratio χ> 0.3. The result is a manufacturing method for an eceiver with a heating area for the heating of a heat-transporting medium, and a transport arrangement for the transport of the medium through the heating area, wherein in the heating area an optical opening for sunlight and in the path of the incident sunlight arranged, the absorber absorbing sunlight is provided, characterized in that the absorber is formed as a blackbody - radiation arrangement with reduced convection and an absorber space cooperating with the absorber space is provided as a heat transporting medium in a frequency bands of the infrared absorbing gas and so provided the absorber space is measured that in a predetermined operating condition of the receiver, the temperature of the absorption space operatively flowing through the heat-transporting medium by absorbing the infrared radiation of the absorber Bers (and the infrared components of the solar radiation) increases, such that the ratio χ of the temperature increase (T ₃ -T ₂ ) by absorption in the absorber space compared to the total temperature increase (T ₄ -T ₂ ) by the absorption and convection at the absorber> Is 0.3.

A heteropolar gas is preferably provided as the gas, particularly preferably CO ₂ , steam, CH ₄ , NH ₃ , CO, SO ₂ , SO ₃ , HCl, NO, and NO ₂ or a mixture of these gases. In this case, further in one embodiment of the invention, the ratio χ is set to be equal to or greater than 0.4, preferably 0.5, more preferably 0.6, more preferably 0.7 and most preferably 0.8.

Finally, in a further embodiment, a secondary absorber designed as a black body radiation arrangement with reduced convection can be provided in the absorber space, and more preferably the receiver can be designed as a spatial receiver.

Claims

claims

A method of operating a receiver having a heating region for heating a heat-transporting medium, and a transport assembly for transporting the medium through the heating region, wherein in the heating region an opening for the radiation of the sun and in the path of the incident radiation of Sun arranged, this absorbing absorber is provided, characterized in that as the heat-transporting medium is provided in frequency bands of the infrared absorbing gas, and that the operating parameters of the receiver set in such a way and the gas is selected such that its temperature during transport through the Heating range by absorption of radiation increases such that the ratio χ of the temperature increase (T ₃ -T ₂ ) by absorption of radiation over the total temperature increase (T ₄ -T ₂ ) by the absorption and convection at the absorber> 0.3.

2. The method of claim 1, wherein the temperature during transport through the heating region by absorbing the radiation of the absorber increases such that the ratio χ of the temperature increase (T ₃ -T ₂ ) by absorbing the radiation of the absorber over the total temperature increase (T ₄ - T ₂ ) by the absorption of the radiation of the absorber and convection at the absorber> 0.3.

3. The method of claim 1, wherein the heating region has a arranged in the path of the incident radiation of the sun, provided between the opening and the absorber absorber space, and wherein the ratio χ the ratio of the temperature increase (T ₃ -T ₂ ) by absorption the radiation of the absorber in this absorber space to the total temperature increase (T ₄ -T ₂ ) by the absorption and convection at the absorber, after the gas has passed this.

4. The method of claim 1, wherein the heating area comprises two absorber spaces with a common absorber, and wherein the ratio χ is provided for one or both of the absorber spaces.

5. The method of claim 1, wherein the gas is a heteropolar gas, preferably one or a mixture of the gases C0 ₂ , water vapor, CH ₄ , NH ₃ , CO, S0 ₂ , S0 ₃ , HCl, NO, and N0 ₂ , especially preferably a mixture with water vapor and C0 ₂ .

6. The method of claim 1, wherein the ratio χ is equal to or greater than 0.5 or preferably equal to or greater than 0.7, more preferably equal to or greater than 0.8.

7. The method of claim 1, wherein gas is passed through the absorber.

8. The method of claim 1, wherein gas is guided past the absorber.

9. The method of claim 1, wherein the gas is placed in the heating region under pressure, preferably in a range between 2 and 20 bar, more preferably between 5 and 15 bar, most preferably 10 bar.

10. The method of claim 1, wherein gas is passed around the absorber to a rear of the absorber and then away therefrom.

11. The method according to claim 1, wherein the gas which is heated by absorption of the radiation of the absorber is taken from an absorber space as soon as it is partially heated and / or a partially heated gas is supplied to an absorber space, and wherein the supply takes place in the absorber space at the respective location, where essentially the temperature in the absorber space corresponds to the temperature of the partially heated gas

A receiver for carrying out the method according to claim 1 or manufactured according to the method of claim 21, comprising a heating section for heating a heat-transporting medium having an opening for the radiation of the sun, and one arranged in the path of the incident radiation of the sun , comprising these absorbent absorbers, with a transport arrangement for the transport of the medium through the heating area, characterized in that further provided an absorber space for heating the heat transporting medium and the absorber as acting in the absorber space radiation arrangement and the transport arrangement for transport a gas is formed as a heat-transporting medium, wherein the heat-transporting medium is substantially a in Absorbing frequency band of the infrared region absorbing gas, and the cooperating with the absorber absorber space is dimensioned such that in operation the ratio χ of the temperature increase (T ₃ - T ₂ ) in the frequency bands of the infrared absorbing heat-transporting gas by absorption in the absorber space against the temperature increase (T ₄ - T ₂ ) by absorption and convection at the absorber,> 0.3.

13. Eceiver according to claim 12, wherein the absorber space is dimensioned such that in operation the ratio χ of the temperature increase (T ₃ - T ₂ ) of the frequency bands of the infrared region absorbing heat-transporting gas by absorbing the radiation of the absorber in the absorber space with respect to the temperature increase (T ₄ - T ₂ ) by the absorption of the radiation of the absorber and the convection at the absorber,> 0.3.

14. Receiver according to claim 12, wherein an absorber space between the opening for the radiation of the sun and the absorber is arranged, and wherein χ the ratio of the temperature increase (T ₃ - T ₂ ) by absorbing the radiation of the absorber in this absorber space the total increase in temperature (T ₄ - T ₂ ) due to absorption and convection at the absorber, after which the gas has passed through it.

15. Receiver according to claim 12, wherein the heating area has two absorber spaces to which the absorber is common and wherein the ratio χ is provided for one or both of the absorber spaces, with connecting channels preferably leading around the absorber connecting the two absorber spaces.

16. Receiver according to claim 12, wherein the absorber at least partially has a gas-tight surface and is preferably plate-shaped.

17. Receiver according to claim 12, wherein the walls of the absorption space and / or the absorber are free of coolant, in particular cooling channels.

18. Receiver according to claim 12, wherein in operation the heat-transporting gas contains a heteropolar gas, preferably one or more of the gases C0 ₂ , water vapor, CH4, N is H3, CO, S0 ₂ , SO3, HCl, NO, and N0 ₂ , and more preferably a mixture with water vapor and C0 ₂ .

19. The receiver according to claim 12, wherein a secondary absorber is provided in an absorption space and is arranged and configured such that it can be heated by the infrared radiation of the absorber and in operation acts via its radiation in turn into the absorber space, wherein it is preferably plate-shaped and particularly preferably does not shade the absorber substantially.

20. Receiver according to claim 12, wherein the transport arrangement comprises one or more connected to an absorber space lines for heat-transporting gas, which are arranged such that the absorber space teilwärwärtes gas removed and / or divergently heated gas can be supplied to a place at which in Essentially, the temperature of the gas in the absorber space corresponds to the temperature of the partially heated, supplied gas.

21. Receiver according to claim 12, wherein an absorber space for a pressure of the gas in a range between 2 and 20 bar, more preferably between 5 and 15 bar, most preferably 10 bar is designed.

22. Receiver according to claim 11, wherein the ratio χ is equal to or greater than 0.5 or preferably equal to or greater than 0.7, more preferably equal to or greater than 0.8.

23. A manufacturing method for a receiver having a heating area for the heating of a heat-transporting medium, and a transport arrangement for the transport of the medium through the heating area, wherein in the heating area an optical opening for sunlight and arranged in the path of the incident sunlight, the sunlight absorbent absorber is provided, characterized in that the absorber is formed as a radiation arrangement and a cooperating with the absorber absorber space is provided as a heat-transporting medium in a frequency bands of the infrared absorbing gas such and the absorber space is dimensioned such that in a predetermined operating condition of Receivers the temperature of the absorption space operable by flowing, heat-transporting medium by absorption of the infrared radiation of the absorber increases, such that the ratio χ of the temperature increase (T ₃ -T ₂ ) by absorption in the absorber space compared to the total temperature increase (T ₄ -T ₂ ) by the absorption and convection at Absorber> 0.3.

24. The method of claim 23, wherein an absorber space in the path of the incident radiation of the sun between the opening and the absorber is arranged, and the ratio χ as a ratio of the temperature increase (T ₃ -T ₂ ) by absorbing the radiation of the absorber in this absorber space to the total temperature increase (T ₄ - T ₂ ) by the absorption and convection at this absorber, after which the gas has passed this, is provided.

25. The method of claim 23, wherein the gas comprises a heteropolar gas, preferably one or more of the gases C0 ₂ , water vapor, CH ₄ , NH ₃ , CO, S0 ₂ , S0 ₃ , HCl, NO, and N0 ₂ and more preferably a mixture with water vapor and C0 ₂ ..

26. The method according to claim 23, wherein the ratio χ is equal to or greater than 0.4, preferably 0.5, more preferably 0.6, more preferably 0.7 and most preferably 0.8.

27. The method of claim 23, wherein in the absorber space designed as a radiation arrangement Sekundärabsorber is provided.