CH706465A1 - Trough collector with a concentrator. - Google Patents

Abstract

The invention relates to a trough collector (50) having a primary concentrator (52) which concentrates solar radiation into a focal line region, with an arrangement for secondary concentration of the sun's rays reflected from the primary concentrator (52), which further concentrates them into focal regions. The secondary concentration arrangement has multiple rows of secondary concentrators (40) which have the same orientation in one row but different orientation from row to row. Further, means are provided to hold one of the rows in the operating position, the other rows in a rest position. In this way, each of the rows can be allocated one area of the skew angle and, when it is changed, another row can be brought into the operating position.

Description

The present invention relates to a solar collector with a concentrator arrangement according to the preamble of claim 1.

Trough collectors find u.a. in solar power plants application, wherein arrangements for the secondary concentration for such trough collectors have been increasingly proposed.

To date, it has not been able to produce solar power in application of this technology in approximately cost-covering nature because of the not yet overcome disadvantages of photovoltaics. Solar thermal power plants, on the other hand, have been producing electricity on an industrial scale for some time now at prices which, compared to photovoltaics, are close to the current commercial prices for conventionally generated electricity.

In solar thermal power plants, the radiation of the sun is mirrored by collectors using the concentrator and focused specifically focused on a place in which thereby high temperatures (or high light density) arise. The concentrated heat can be dissipated and used to operate thermal engines such as turbines, which in turn drive the generating generators.

Today, three basic forms of solar thermal power plants are in use: Dish Sterling systems, solar tower power plant systems and parabolic trough systems.

The Dish Sterling systems as small units in the range of up to 50 kW per module have not generally prevailed.

Solar tower power plant systems have a central, increased (on the "tower") mounted absorber for hundreds to thousands of individual mirrors with mirrored to him sunlight, so the radiation energy of the sun over the many mirrors or concentrators concentrated in the absorber and so Temperatures up to 1300 ° C to be achieved, which is favorable for the efficiency of the downstream thermal machines (usually a steam or fluid turbine power plant for power generation). California Solar has a capacity of several MW. The PS20 plant in Spain has an output of 20 MW.

Solar tower power plants (in spite of the advantageously achievable high temperatures) to date also found no greater spread.

Parabolic trough power plants, however, are widespread and have collectors in large numbers, which have long concentrators with small transverse dimension, and thus do not have a focal point, but a focal line. These line concentrators today have a length of 20 m to 150 m. In the focal line runs an absorber tube for the concentrated heat (up to 500 ° C), which transports the heat to the power plant. The transport medium is e.g. Thermal oil, molten salts or superheated steam in question.

The 9 SEGS parabolic trough power plants in Southern California together produce an output of about 350 MW. The "Nevada Solar One" power plant, which went online in 2007, has trough collectors with 182,400 curved mirrors arranged over an area of 140 hectares and produces 65 MW. Andasol 3 in Spain, under construction since September 2009, is expected to be operational in 2011 so that the Andasol 1 to 3 turbines will have a maximum output of 50 MW.

For the overall system (Andasol 1 to 3), a peak efficiency of about 20% and an annual average efficiency of about 15% is expected.

As indicated above, an important parameter for the efficiency of a solar power plant, the temperature of the heated by the collector transport medium through which the heat is transported away from the collector and used for the conversion into, for example, electricity: higher temperature can be a higher efficiency in the conversion. The realizable in the transport medium temperature in turn depends on the concentration of the reflected solar radiation through the concentrator. A concentration of 50 means that in the focal zone of the concentrator an energy density per m 2 is achieved which corresponds to 50 times the energy radiated from the sun to one m 2 of the earth's surface.

The theoretically maximum possible concentration depends on the geometry of the earth - the sun, i. E. from the opening angle of the solar disk observed from the earth. From this opening angle of 0.27 ° it follows that the theoretically maximum possible concentration factor for trough collectors is 213.

Even with very elaborate, and thus for industrial use (too) expensive mirrors are well approximated in cross-section of a parabola and thus produce a focal line area with the smallest diameter, it is not possible today, this maximum concentration of 213 only almost reach. However, a reliably achievable concentration of about 50 to 60 is realistic and already allows the above-mentioned temperatures of about 500 ° C in the absorber tube of a parabolic trough power plant.

To increase the achievable temperature, secondary concentrators have now been proposed which concentrate the solar radiation reflected by the primary (trough) concentrator in the longitudinal direction of the primary concentrator, so that the solar radiation is finally concentrated in a number of foci, thus the concentration of sunlight and the temperature generated thereby are higher and should be achievable above 600 ° C.

The same applies if the radiation is to be concentrated on photovoltaic cells, but what, as mentioned above, has not yet been implemented on an industrial scale.

However, the design of secondary concentrators is demanding because the so-called skew angle, i.e. the angle at which the sunlight is incident on the primary concentrator of a trough collector, changes, for example, which can shift the focus areas generated by the Sekundärkonzentratoren, which is particularly problematic in the application of an absorber tube with thermal openings.

As a compound parabolic concentrator (CPC) trained secondary concentrators appear to be particularly suitable for a concentration in the longitudinal direction, but have the disadvantage that the achievable concentration on the acceptance angle (θin) of the secondary concentrator is dependent (radiation that falls outside the acceptance angle in the secondary concentrator , does not reach the focal point range generated by it): the greater θin, the smaller the further concentration achievable by the CPC secondary concentrator.

In US 2010/037 953 it has been proposed to arrange the Fresnel lenses or parabolic reflectors trained secondary concentrators with respect to the Primärkonzentrator pivotable, so that they can be updated continuously the current skew angle.

However, the solution shown for the formation of the pivotable secondary concentrators has the disadvantage that they can be pivoted only over a small part of the necessary pivoting range, without abutting each other and thus to block against another pivoting movement. It is conceivable to equip the arrangement shown with spaced in vertical position secondary concentrators, which would allow the necessary pivotability, but would have the consequence that in the vertical position necessary in operation not the entire solar radiation reflected by the primary concentrator can be secondarily concentrated, which is the efficiency of the solar collector reduced.

Accordingly, it is the object of the present invention to provide a gutter collector with an improved arrangement for the secondary concentration of reflected solar rays.

This object is achieved by a trough collector with the features of claim 1.

Characterized in that the differently oriented components for incident radiation components can be positioned in the path of the radiation reflected by the primary concentrator, is possible to use depending on the current skew angle appropriately aligned secondary concentrators without these must be designed to be pivotable. Currently not required secondary concentrators of different orientation can be parked in a rest position outside the path of the reflected radiation.

Accordingly, eliminates the design effort for an arrangement of pivotable Sekundärkonzentratoren both for the complete detection of all reflected rays as well as for the always highly precise with the passage of time, but constantly changing orientation. This is particularly important in a high-temperature environment, as it is unavoidable in the case of secondary concentrators, which should produce temperatures above 600 ° C, in nature. Likewise, or aggravated by the use of photovoltaic cells, which in nature are arranged directly at the output of the secondary concentrators and therefore must be cooled, which creates additional design problems.

The invention will be explained in more detail with reference to FIGS.

It shows: <Tb> FIG. 1a schematically shows a gutter collector of known design with an arrangement of secondary concentrators, <Tb> FIG. 1b <sep> schematically shows the daily path of the sun and the skew angle that occurs <Tb> FIG. 1c <sep> schematically the skew angle in the collector, <Tb> FIG. 1d <sep> is a diagram showing the change of the skew angle during one year in a north-south orientation of a trough collector with the assumed location Dubai <Tb> FIG. 2 <sep> a preferred embodiment of a secondary concentrator, <Tb> FIG. 3 schematically shows a first preferred embodiment of the trough collector according to the present invention, <Tb> FIG. 4 <sep> is a top view of the embodiment of FIG. 3, <Tb> FIG. 5 <sep> is a view of a section of the juxtaposed rows of secondary concentrators according to the view of FIG. 4, <Tb> FIG. 6 <sep> another embodiment according to the present invention, and <Tb> FIG. 7a to 7c show a side view of a concentrating element modified according to the invention for different acceptance ranges.

Fig. 1a shows a trough collector 1 according to the prior art with a primary concentrator 2, which rests in a frame not shown for relief of the figure, is pivotable and can be tracked so the daily run of the sun.

The double arrow 3 shows the longitudinal direction, the double arrow 4, the transverse direction of the trough collector 1 and the double arrow 5, the pivoting directions of the collector. 1

Further shown is an arrangement 8 of here designed as Fresnel lenses Sekundärkonzentratoren 9 and a sunbeam 10 which is incident on the Primärkonzentrator 2, reflected by this as a beam 11 against a focal line region of the Primärkonzentrators 2 and after passing through a Sekundärkonzentrator 9 in the longitudinal direction 3 is broken, so that it is finally directed as a beam 12 to a focus areas 13.

In other words, the incident sunbeams are first concentrated in the transverse direction 4, then in the longitudinal direction 3, wherein the resulting focal point regions 13 are located on an absorber tube 14, which absorbs the heat and dissipates heat transporting medium.

The primary concentrator 2 shown here as a rigid mirror can also be designed as a flexible, spanned in a pressure cell film, as shown for example in WO 2010/037 243. Instead of the absorber tube 14 shown here, it is also possible to provide photovoltaic cells for the production of electricity at the location of the focal point regions 13.

As mentioned above, it is proposed in US 2010/037 953 to form the secondary concentrators 9 pivotably with a pivot axis extending in the transverse direction 4 in order to continuously track them to the skew angle (see FIG.

Fig. 1b shows the daily path of the sun with respect to a collector 1. Shown is the north-south oriented collector 1 with the symbolized by the dashed line 20 horizon, as he may be visible from the collector 1 from. Further illustrated is the orbit 21 of the sun on a summer day which begins at point 22 in the east and ends at point 23 in the west. Also visible is the orbit 25 of the Sun on a winter day, starting at the east at point 26 and ending at the west at point 27.

By pivoting according to the double arrow 5, the collector 1 is continuously aligned during the day with the sun, i. E. In the morning, with reference to FIG. 1b, it is tilted to the left, aligned horizontally at noon, and tilted to the right in the evening.

Despite this orientation, it is such that in summer the sun (seen here in relation to the plane of the drawing) rises in front of the collector 1 (ie north of him), at noon behind him (ie south) and in the evening in front of him (ie turn north). In winter, the sun is always behind the collector 1, so south of him.

This is illustrated by the normal 28 of the collector 1, which is perpendicular to the dashed lines, extending in the longitudinal direction 3 generating line 29 of the concentrator 2: for example, it closes with the sun's ray 30 (sun in the winter months) a first angle S, and with the sun ray 31 (sun in the summer half-year) a second angle S a. The angle S is known in the art as a skew angle and refers to the incidence of the sun's rays in the longitudinal direction 3 obliquely to the concentrator of the collector when it is aligned with the sun.

Falls a sunbeam 31 obliquely from the front of the collector 1, the skew angle is negative, falls a sunbeam 30 from obliquely behind the collector 1, the skew angle is positive. If a sunbeam coincides with the normal 29 at noon, the skew angle is 0. This is shown in summary in FIGS. 1 c and 1 d: If the collector 1 is aligned with the sun, the sunrays fall below the skew angle S the concentrator 2 so that they lie with the normal 29 in a plane E, wherein the not reflected for relieving the figure reflected rays are concentrated in the focal line region of the concentrator 2.

Fig. 1d shows an example of a diagram with the range of the skew angle on the basis of location Dubai depending on the season: on the horizontal axis, the season t is plotted, on the vertical axis, the value of the skew angle in degrees.

The diagram of FIG. 1d is based on a north-south orientation of the collector 1, wherein the pivoting range of -70 ° to + 70 ° ranges (0 ° corresponds to the horizontal orientation at noon).

For the conditions shown in Fig. 1b is to be read that the skew Angle S in the summer, approximately on 25 June, in the morning (point 22 in Fig. 1b) is about -17 °, at noon at ca + 4 ° and in the evening again at about -17 °. Over day, the skew angle S changes by about 21 °.

In the winter half-year, approximately on 5 January, the skew Angle S changes between about + 32 ° and about + 48 °, so changes by about 26 °.

Fig. 2 shows a secondary concentrator 40, as it can be used in a collector 1 (Fig. 1a) instead of the there schematically shown, designed as Fresnel lenses secondary concentrators 9. The secondary concentrator 40 has a front wall 41 and a rear wall 42, which are formed as Compound Parabolic Concentrator (CPC). CPC's are generally known to those skilled in the art. The CPC is for the secondary concentration of the sun's rays 11, 11 reflected from the primary concentrator 2 (Figure 1a), i. he concentrates these in the longitudinal direction 3.

Further illustrated are a right side wall 43 and a left side wall 44, which are formed as a Trumpet Concentrator and allow concentrated by the primary concentrator in the transverse direction 4 sun rays 11 in addition to concentrate once again in the transverse direction 4. The person skilled in the art is aware of a Trumpet Concentrator.

As a result, highly concentrated rays 45 exit from the upper opening 46 of the secondary concentrator 40 and hit in a focal point region 47 according to the invention an absorber tube 14 (FIG. 1a) or photovoltaic cells, which are omitted to relieve the figure.

The lower opening 48 of the Sekundärkonzentrators 40 has an acceptance range, which is determined by the properties of the CPC and this Trumpet Concentrators, with the result that incident only at the acceptance angle rays 11 are concentrated in the focal area 47, which for here exemplified, lying outside the acceptance angle beam 11 is not the case.

Fig. 3 shows a preferred embodiment of the present invention. Shown is a collector 50, with a flexible, arranged in a pressure cell 51 concentrator membrane 52, the primary sun rays 53, 53 concentrated primarily and thus reflected as rays 54, 54 to a secondary concentration arrangement 55. The pressure cell 51 is clamped in a frame 59 of the collector 50.

In a frame 56 below the absorber tube 57, a carriage 58 is arranged, which is arranged displaceably in the transverse direction 4 under the absorber tube 57 and carries secondary concentrators 40 (Figure 2), here in several adjacent rows 60, 61 and 62, so that the secondary concentrators 40 are grouped in the rows 60 to 62. In each row or group 60 to 62 are then the associated secondary concentrators 40 behind each other and are thus arranged along the length of the primary concentrator along.

To relieve the figure, a conventional drive of the carriage 58 is omitted, which can be readily designed by the skilled person according to the needs on site.

By suitably moving the carriage 58, one of the rows 60 to 62 is located below the absorber tube 57, i.e., one of the rows 60 to 62. in operative position in the path of the reflected radiation and the other two rows in rest position, i. outside the path of the reflected radiation.

The secondary concentrators of each row (or group) 60-62 are oriented differently than those of another group, thus having a differently oriented acceptance range and are thus capable of secondarily concentrating radiation corresponding to an associated predetermined area of the skew angel S. ie in a predetermined skew range corresponds to:

Starting from the range of skew angles at the specific location and according to the diagram of FIG. 1 d, the person skilled in the art can thus determine the complete skew area (ranging from -18 ° to + 49 ° in the example of FIG subdividing a suitable number of predetermined skew areas (in the example according to the arrangement of Fig. 3, the three thereof) and assigning to each of these skew areas predetermined therewith a row (or group) 60 to 62 of secondary concentrators 40 which are in their skew area are aligned and then brought in the appropriate season by the displacement of the carriage 48 in operating position.

Fig. 4 shows a view from above of the collector 50 according to FIG. 3, wherein the discharge tube 57 is omitted to relieve the figure. Its position is represented by the line 70.

In the carriage 58, three rows or groups 60 to 62 of secondary concentrators 40 are arranged according to the illustrated embodiment. As noted above, the secondary concentrators 40 in a respective row are aligned with an associated skew area.

The dashed line 71, a portion of the rows 60 to 62 designated by secondary concentrators, which is shown in Fig. 5 in more detail.

As a result, the trough collector according to the invention has a secondary concentration array 65 of sunbeams 54, 54 reflected from the primary concentrator 42 which further concentrates them into focus areas 46 (Figure 2), the secondary concentration array 65 of the reflected radiation being different in number aligned, here as secondary concentrators 40 formed concentrating components and further comprising means to bring the concentrating components alternately in an operating position in the path of the reflected radiation or in a rest position outside the path of the reflected radiation. These means are formed in the embodiment according to FIG. 3 as a frame 56, carriage 58 and drive for the carriage 58.

Fig. 5 shows the view of the portion according to the dashed line 71 from the rows 60 to 62 of secondary concentrators 40. To relieve the figure, the carriage 58 and all other elements of the collector 50 is omitted, only the position of the absorber tube 57th is marked by the line 71. In the figure, the different orientation of the secondary concentrators of each of the rows 60 to 62 is clearly visible.

As mentioned above, the present invention is not limited to the embodiment of a secondary concentrator shown in Fig. 2, according to the invention is any element through which the radiation reflected from the primary concentrator is longitudinally concentrated in a focal point region. Further, the means for the displacement of the secondary concentrating elements may be formed differently, it is conceivable, for example, instead of a moving carriage 56 via the frame 56, to arrange the secondary concentrating elements on rotating, placed around the absorber tube rings. Likewise, photovoltaic cells may be arranged in the focus areas formed by the secondary concentrating elements.

Due to the parabolic trough shape of the primary concentrator, it follows that the reflected rays seen in the longitudinal direction are not incident parallel to the secondary concentrating element, but at an angle of a few degrees, whose magnitude changes with the size of the skew angle. Accordingly, in a preferred embodiment, the acceptance areas of the secondary concentrating elements of the various rows or groups are made overlapping, so that when changing from one row to another row, the instantaneous solar radiation can be completely concentrated by both rows into the focal areas.

Fig. 6 shows another embodiment of a collector 80 according to the present invention in which the secondary concentration assembly 65 is modified. Between the absorber tube 57 and the carriage 58, a single row 83 of secondary concentrating elements, here of secondary concentrators 40, in the frame 56 via retaining arms 84 is fixed. The carriage 58 has rows 85 and 86 of attachment members 87 and 89 which, depending on the position of the carriage 85, are in an operating position (ie in the path of the radiation 44, 44) and together with the secondary concentrators 40 form a modified secondary concentration element , The effect of the attachment elements is such that the acceptance range of the secondary concentrators 40 changes, so that once again there are three different series of secondary concentrating elements, each associated with a skew area and having the corresponding acceptance range.

Secondary concentrators 40 are shown schematically in FIGS. 7a to 7c, wherein FIG. 7a shows a secondary concentrator 40 without an attachment element whose acceptance range corresponds to the dot-dash line 86. In Fig. 7b, a header member 87 is shown, which is opposite the rear wall 42 of the Sekundärkonzentrators 40 an asymmetric continuation of the front wall and thus changes the direction of its acceptance range according to the dotted line 88. Similarly, in Fig. 7c, where the direction of the acceptance area of the secondary concentrator 40 shown there is further changed by the larger attachment element 89, as shown by the dotted line 90. For example, and following the diagram according to FIG. 1c, the row of secondary concentrators 40 according to FIG. 7a for a skew range from -18 ° to + 10 °, the row of secondary concentrators with attachment elements 87 according to FIG. 7b for a skew range from 5 ° to + 33 °, and the series of secondary concentrators with attachment elements 89 according to FIG. 7c can be designed for a skew range of + 30 ° to + 48 °.

The person skilled in the art can determine the skew ranges according to the specific conditions prevailing on site. Also, those skilled in the art can determine the number of rows of secondary concentrating elements, the number of three rows shown in the present embodiments is considered to be advantageous, but only two or more than three, for example, four to six rows are conceivable.

Claims (12)

A trough collector having a primary concentrator (2) which concentrates solar radiation (10, 11, 53, 53) in a focal line region, with a secondary concentration arrangement (56) for the solar radiation (10, 11, 53, 13) reflected by the primary concentrator (2). 53) further concentrating them into focus areas (47), characterized in that the secondary concentration arrangement (56) of the reflected radiation has a number of incidentally aligned components (40, 87, 89) and means for varying aligned components (40, 87, 89) are alternately brought into an operating position in the path of the reflected radiation or in a rest position located outside the path of the reflected radiation. 2. trough collector according to claim 1, wherein the differently oriented components (40,87,89) in groups have the same on a predetermined skew area firmly oriented acceptance area, a plurality of groups (60 to 62) provided for each different skew areas and formed the means are each to position one of the groups operable in the path of the reflected radiation. A trough collector according to claim 1, wherein the acceptance range of at least one group (60 to 62) in the transverse direction is different from that of another group (60 to 62). 4. trough collector according to one of claims 1 to 3, wherein the concentrating components (40, 87, 89) as secondary concentrators (40) with groups of the same but the same, but different from group to group orientation, wherein the orientation of a group a predetermined skew And the secondary concentrators (40) of a group are arranged one behind the other along the length of the primary concentrator (2). A trough collector according to any one of claims 1 to 3, wherein the concentrating components (40, 87, 89) comprise a single group of fixed secondary concentrators (40) and various groups of header elements (87, 89) for the secondary concentrators (40). which, in conjunction with the secondary concentrators (40), respectively align their acceptance range for different skew areas, and wherein the means are arranged to position one group of header elements operatively in the path of the radiation in front of the secondary concentrators (40) , 6. gutter collector according to claim 4 or 5, wherein the secondary concentrators (40) are designed as compound parabolic concentrators. 7. Trough collector according to claim 1, wherein the arrangement for secondary concentration (56) for the concentration of the reflected radiation is also formed in the transverse direction, and preferably for each focal point region comprises a Trumpet Concentrator. 8. Trough collector according to claim 1 or 2, wherein the arrangement for secondary concentration (56) is adapted to concentrate at a skew angle of -20 ° to + 50 ° to the primary concentrator (2) incident sunlight in focal areas (47). 9. Trough collector according to claim 2, wherein the acceptance ranges for the different, predetermined skew areas overlap. 10. Trough collector according to claim 1, wherein an absorber tube (57) is provided with thermal openings, and the focal areas (47) are located at the location of the thermal openings. 11. trough collector according to claim 1, wherein photovoltaic cells are arranged at the location of the focal areas (47). 12. trough collector according to claim 1, that the primary concentrator (2) is divided into a plurality of longitudinal regions and each longitudinal region is associated with an arrangement for the secondary concentration of the sunlight reflected by the longitudinal region.