CSP TRACKING

Description

[0001] The present invention relates to a system and a method for tracking solar energy concentrating systems. The generic term "Concentrated Solar Power ("CSP") is also commonly used. In such systems and methods, the direct solar radiation is typically focused onto a receiver or solar absorber using reflectors. Since the position of the sun changes over time, the orientation of the system components must be adjusted accordingly, i.e., tracked.

[0002] CSP systems concentrate the sun's direct radiation by using focused reflector surfaces that concentrate the incoming sunlight onto the absorber. The reflector and absorber track the sun. The systems thus collect solar energy across a large reflector surface and concentrate it onto a comparatively small receiver surface. For example, the reflector or collector concentrates incoming radiation from an area of 60m² onto a receiver surface of 1m². The ratio of large collector surface to small receiver surface allows for low losses and high temperatures.

[0003] In so-called solar farm power plants, the heat is collected in numerous absorbers or receivers distributed across the area, while in solar tower power plants or parabolic power plants, for example, the sun's radiation is concentrated into a single focal point using point concentrators. All of these systems differ in many ways from direct solar systems or solar power systems, such as photovoltaic systems, as well as from solar thermal systems without concentration, such as thermal power plants.

[0004] CSP systems within the meaning of the present invention particularly and preferably include systems with one or more parabolic trough collectors or Fresnel collectors connected in parallel, so-called line concentrators. A heat transfer medium, such as thermal oil or superheated steam, is heated in the collector field. The heated heat transfer medium is then fed, as in a turbine, to generate electrical energy, for example, to a turbine and a generator.

[0005] The system of a parabolic trough power plant is in Fig. 1a-1 For example, parabolic trough collectors consist of curved mirrors SP that focus the sunlight So onto an absorber tube or a so-called receiver R running along the focal line (see right illustration). In the absorber tubes, the concentrated solar radiation is converted into heat and transferred to a circulating heat transfer medium. The heat medium is then fed via pipes (solar field piping) for further use or energy generation (conversion). For cost reasons, the parabolic troughs are usually only uniaxially tracked. They are therefore arranged in a north-south direction and are only tracked or tilted according to the height of the sun during the course of the day. This is shown schematically in Fig. 1a-2 shown.

[0006] Parabolic troughs or parabolic trough mirrors are essentially parabolic in cross-section, preferably perpendicular to the trough axis. Such a mirror shape has the property of reflecting all rays incident parallel to their axis of symmetry through the focal point of the parabola (see right illustration in Fig. 1a-1 This geometric principle is used, among other things, for parabolic (trough) mirrors, which use a parabolic surface with reflective surfaces (mirrors) to concentrate incoming sunlight at a focal point or, in the case of a parabolic trough mirror, on a focal line. The energy of the concentrated sunlight is absorbed by so-called receivers, which are mounted along the focal point or focal line, and is converted, for example, into heat, and used for further energy conversion. Known parabolic trough mirrors essentially have a trough-like or curved mirror called a reflector (or a plurality of mirrors which together form a trough), an absorber tube called a receiver and a support structure or substructure.

[0007] Fig. 1a-3 shows a schematic representation of an exemplary reflector construction with a parabolic trough mirror 1. The parabolic trough mirror 1 has an exemplary rear or support structure in the form of a guide arch 2 with a receiver in the form of an absorber tube 3. The guide arch 2 here provides a first curved guide matrix 4, which serves as a support for a mirror element, here a first flexible thin glass 5 (on the right half of the parabolic trough mirror 1 of Fig. 1a-3 shown) when it is bent and clamped on the guide arch 2. In Fig. 1a-3 The thin glass 5 is shown in the unbent and tensioned state. The guide arch 2 further preferably provides a second curved guide matrix, which essentially corresponds to the first and is arranged opposite it in the cross-section shown. It serves as a support for a second flexible thin glass 10, which is shown here bent on the left half of the parabolic trough mirror. The trough can have a radius or an opening or aperture width of the parabola of approximately 1 to 8 m, preferably of approximately 1.5 - 5 m, whereby the curvature can vary in a side view of the parabolic mirror 1 along the guide matrix 4.

[0008] The guide matrix of the guide arch 2 can be formed by curved ribs 6A, 6B, as shown here. In the area of the reference numerals 6A, 6B, at the position shown in the illustration according to Fig. 1a-3 Where the ribs abut each other, i.e., at the lowest point of the channel, the ribs can be spaced apart. Preferably, a support, such as a torsion tube, runs along the longitudinal axis of the channel at this point (the cross-section). This is shown, for example, in the illustrations according to Fig. 3a , 3b , 3c , 3d , 3e , 6 , 7 and 8bThis support is firmly connected to the support structure or guide matrix. It preferably runs parallel to a pivot axis, which in turn preferably runs along the lowest point of the trough, and along which the trough can be pivoted to achieve optimal alignment with the sun. Alternative designs, both of the general construction, for example, the use of pre-bent mirror elements and other clamping or other rear structures, as well as of the tracking system and its axis, are known. The discussion of the present invention herein includes, but is not limited to, the previously described designs.

[0009] A further development of the parabolic troughs are the so-called Fresnel-Spiegel-Kollektoren, cf. Fig. 1b .Several parallel, flat, uncurved or slightly curved mirror strips (reflectors) arranged at ground level (based on the principle of a Fresnel lens) reflect the incoming direct sunlight onto an absorber tube. A second reflector (secondary reflector) can be used to achieve better focusing on the absorber tube. The strips are tracked uniaxially. An additional secondary mirror behind the tube directs the radiation onto the focal line.

[0010] This design combines the functional principles of parabolic trough collectors and tower power plants, dispensing with curved mirrors (see above; slightly curved mirrors can also be used) and multi-axis sun tracking, while maintaining a modular structure. Unlike most parabolic trough designs, the absorber tube is not moved. This allows for very long collectors to be built, which, due to the lack of pipe bends and flexible connections, exhibit low flow resistance for the heat transfer medium. This is offset by shading losses between the mirror strips.

[0011] The discussion of the present invention herein includes, but is not limited to, the previously described constructions.

[0012] At the Solarturmkraftwerk, cf. Fig. 1c ,In a central receiver power plant, the absorber R is mounted elevated on a tower Tu. When the sun shines, hundreds to thousands of automatically positioned mirrors SP (heliostats) align themselves so that the sunlight is reflected onto the central absorber (receiver). The strong concentration of solar radiation creates high temperatures of up to several thousand degrees Celsius at the top of the tower.

[0013] The discussion of the present invention herein includes, but is not limited to, the previously described constructions.

[0014] Other systems, generally for decentralized applications with a smaller power range, include parabolic dish systems or solar Stirling systems, in which solar thermal energy is converted into mechanical energy using a Stirling engine. This is usually used to generate electrical energy in a directly connected generator. See also: Fig. 1d .

[0015] The discussion of the present invention herein includes, but is not limited to, the previously described constructions.

[0016] Concentrating solar radiation onto a comparatively small receiver surface requires precise alignment and focusing of the solar radiation. In addition, the sun's position, and thus the angle of incidence, changes depending on time and the position of the sun. Therefore, tracking is required to align solar energy concentrating systems with the sun. Typically, the calculated sun position is used as the actual value. However, this poses problems in practice.

[0017] In particular, the actual solar radiation may deviate from the solar radiation expected based on the calculated position of the sun. This deviation is not astronomically caused, but is due, for example, to the refraction of solar radiation by air layers with significantly different temperatures. Furthermore, deviations from the pre-calculated or predictable radiation paths arise due to design inaccuracies during system construction, design inaccuracies that arise during operation, e.g., foundation movements, design inaccuracies due to wear and tear on drives, and inaccuracies resulting from sensor difficulties in recording the actual position.

[0018] This results in a series of requirements for system components. For example, the rear structure supporting the reflector and / or receiver is crucial for the precise positioning of the reflector and / or receiver. Therefore, high standards regarding dimensional accuracy, weather resistance, wind load, and weight must be met. The tracking system, whether discontinuous or continuous, must also meet requirements regarding approach accuracy, stopping accuracy, energy consumption, reliability, and compliance with guidelines. The system components, especially the rear structure and tracking, are particularly important given the aforementioned design-related inaccuracies in tracking.

[0019] To mitigate or eliminate these and other tracking problems, systems are used that determine the actual position of the sun or the actual solar radiation that deviates from the expected solar radiation. The angle of incidence of the sun's radiation on the reflector is particularly important here.

[0020] On the one hand, it is known to use systems that are completely independent and not connected to the tracking structure, and that determine the actual position of the sun. This includes, for example, a sundial. However, these systems often fail to resolve the problems mentioned above, which arise due to design inaccuracies, wear, or aging.

[0021] Alternatively, it is known to combine position measurement with system design and perform a relative position measurement of the sun to the concentrating system. For this measurement, there are known ways to measure the irradiance directly at the receiver. However, this has also proven to be impractical. In particular, the radiation intensity / density at the receiver is very high, so the required sensor and component specifications are beyond the available scope – both in terms of economic criteria and the general fulfillment of technical requirements. The lifetime of the components, where available, is extremely short.

[0022] It is also known to observe a shadow using special sensors that analyze the shadow cast. This involves analyzing the shadow cast by a diaphragm using a sensor with two photovoltaic (PV) cells. If the shadow runs symmetrically along the center axis of the PV cell array, the voltages of the two cells have the same value. If the shadow moves away from the center due to movement of the collector or the sun, the voltage of the cell that is more shaded than the other decreases.

[0023] Such a system typically consists of a PV cell sensor connected via cabling to a signal amplifier, which in turn is connected via cabling to a separate control unit in the solar field for signal processing, housed in a separate housing. The control unit executes a program to analyze the signal values and transmits the results via cabling to the control room via an interface. From there, control signals are then sent to the system for the appropriate system tracking. This is schematically shown in Fig. 2 shown.

[0024] However, such systems have proven disadvantageous in several respects. Firstly, they are complex, costly, and maintenance-intensive to set up and maintain. For example, they require cleaning twice a day or more. Secondly, the resolution and accuracy of the systems are insufficient. Furthermore, the system's lifespan is limited, and high costs arise from both design-related maintenance and repairs and software-related maintenance. Finally, the entire system is complex to install, requiring significant interventions in the existing system architecture.

[0025] A photovoltaic system with a tracking system is known from CN 203012516 U. The tracking system uses a defined geometric body, namely a cone mounted on a transparent glass pane, and a camera obscura.

[0026] The geometric shape of the cone's shadow on the transparent pane is recorded and its height calculated. The PV system is tracked across multiple axes. This system uses a separate unit to calculate the actual position of the solar radiation, which has a complex structure consisting of several interacting parts. The geometric evaluation is error-prone and depends in particular on the accurate positioning of the individual parts relative to one another. Finally, the described structure does not meet the high requirements for tracking accuracy required for the present application. The use of solar energy to generate power through photovoltaic elements does not require a comparable concentration of radiation incident on a large reflector surface onto a small receiver surface.Therefore, even a relatively inaccurate alignment of the photovoltaic elements to the sun does not have a significant impact on the system's efficiency. Deviations of 1° from the optimal alignment are generally tolerated. For stationary PV systems, e.g., in private operations, a deviation of 30° from the optimal radiation incidence is usually tolerated. In CSP systems, however, a deviation of 1° or more is generally undesirable, as this already has a significant impact on the system's efficiency. In CSP, this has to do with the geometry of the collector, among other things. Here, two system parameters, for example, must be considered: . the distance from the receiver to the mirror surface, and the diameter of the receiver.

[0027] For example, a parabolic trough with a focal line of approximately 1795 mm and an aperture of 6000 mm and a receiver tube of 70 mm diameter can be used.

[0028] The smallest distance between the mirror and the receiver is 1795 mm, the largest distance, at the ends of the parabola, is approximately 3100 mm.

[0029] Given the sun's size of approximately 0.5° (as seen from Earth), this theoretically results in a focal line width of approximately 27 mm. The calculation is easy to follow.

[0030] However, there are other unpredictable factors. For example, the mechanical components (including construction, receiver tube holder, foundations, etc.), the mirror inaccuracies and the drive inaccuracies.

[0031] The diameter of the sun, the mirror inaccuracy, and the mechanical components alone limit the 70 mm receiver tube diameter available in this example. Thus, precise manufacturing and design dimensions become extremely important, even in the drive technology, down to every tenth or even hundredth of a degree.

[0032] US 2013 / 133640 A1 discloses that, in a radiation focuser having a curved mirror configured to focus light onto an energy-harvesting body mounted along the focal axis of the mirror, an alignment correction device and method comprises a linear array of light detectors configured to be mounted on a bottom surface and transverse to a centerline of the curved mirror to intercept the shadow cast by the energy-harvesting body mounted along the focal axis. The output signals of the individual detectors are measured and recorded according to the order in which the light detectors are arranged on the array. When a shadow falls on the array, a drop in output power results from neighboring detectors.A shadow detection device is designed to determine a center point of the intrusion, and a correction device is configured to issue a correction command if the center point is different from an optimal position.

[0033] US 2013 / 092155 A1 discloses a focal display panel located within a parabolic solar energy collection array having reflective surfaces and a tube containing a working fluid to be heated. The panel includes a target area for displaying light and shadow patterns reflected from the array and provides a visual means for determining the amount, if any, by which the focal point of the parabolic array misses the center of the tube containing the heated working fluid.

[0034] The present invention is based on the Aufgabe The aim is to provide an improved CSP system. The system should ideally overcome the disadvantages of the state of the art. In particular, it should be simple, economical, durable, and accurate.

[0035] This object is achieved in particular by an improved tracking system and method, especially for CSP systems. This object is achieved by the features of the independent claims. The dependent claims, as well as the features described below, represent preferred additional or alternative embodiments.

[0036] According to the present invention, the shadow of a shadow shield that is permanently attached to the structure is preferably used to determine the actual solar radiation or to track the reflector depending on the angle of incidence of the solar radiation. More preferably, the shadow of the shadow shield, which is preferably part of the existing structure and furthermore preferably that of the receiver itself, is used. This allows for a particularly simple and durable construction, preferably without the need for additional parts or attachments. Likewise, a high degree of reliability is achieved, especially since the shadow shield is an integral part of the construction, thus preventing interface deviations.

[0037] Fig. 3a shows the example of the shadow cast by a receiver tube in the collector. In the illustrated alignment of the receiver and the collector of a parabolic trough system, the shadow S of the receiver tube R (not visible in the illustration) does not lie directly on the collector mirrors but on a support T of the rear structure. In common designs of parabolic troughs, these are formed from two rows of curved mirrors SP arranged symmetrically to a central axis. The mirrors SP are arranged on opposite sides of a support T running longitudinally through the center. The support T and the receiver tube R are preferably located in the center plane ME of the parabolic trough (cf. Fig. 1a-3 ). With an optimal alignment of the trough to the sun, the shadow SR of the receiver tube R falls centrally on the support, as shown in the illustration according to Fig. 3a It is clear that any shadow receiver can be used as support T. It does not have to be a load-bearing structural element.

[0038] The representation according to Fig. 3b shows a scenario according to Fig. 3a in rendered form. Load-bearing parts of the collector assembly have been omitted here for improved presentation (such as supports of the receiver tube, which appears to be floating freely here, but is actually mechanically fixed). In addition to the representation in Fig. 3a is in Fig. 3b The reflection (Refl.) of the receiver tube R on the mirror SP can be seen. This reflection varies with the viewer's position, unlike a shadow, which is independent of the viewer's position. Fig. 3c shows a detailed section of the rendered image according to Fig. 3b , in which the receiver tube is not visible.

[0039] Accordingly, Fig. 3d another example view of a scenario according to Fig. 3a in rendered form. Load-bearing parts of the collector assembly have also been omitted here for improved presentation (such as supports of the receiver tube, which appears to be floating freely here, but is actually mechanically fixed). Fig. 3d The reflection (Refl.) of the receiver tube R on the mirror SP can be seen. Here, due to the different viewer's perspective, it is at a different location. This can also be seen, for example, in the graphically inserted lettering "erfis," which is also reflected in the mirror.

[0040] Fig. 3e shows a detailed section of a rendered representation according to Fig. 3b or Fig. 3c , in the supports R ST of the receiver tube R are visible, as well as a corresponding reflection.

[0041] Fig. 4 shows the geometric conditions of the shadow using the example of the receiver tube shadow and Fig. 5 shows the shadow schematically with an explanation of the terms or areas of the umbra KS and penumbra HS. Fig. 4 The penumbra is the distance between the intersection points of the shadow receiver and two lines on the shadow receiver. These lines are the tangents to opposite sides of the sun and a side or point of the receiver, as in Fig. 4 The representation in Fig. 4 shows the penumbra on the right in the illustration. The left one is created by using the tangents to the opposite side of the receiver tube. The umbra is the area between the penumbras.

[0042] The width of the penumbra depends on the distance of the shadow aperture from the shadow receiver. All shadow parameters can be calculated using the sun's diameter d sun , the receiver diameter d tube / receiver (the tube diameter in the illustration), the distance h tube receiver to the shadow receiver, for example, carrier T, and the planetary distance h sun sun-shadow receiver. Fig. 5 shows an example of the shadow of the receiver tube on a shadow receiver, highlighting the central umbra and the lateral penumbra, along with preferred dimensions. It is likely that shadows (collectors) on Earth can be assumed here, and thus a 'solar diameter' of 0.5° is relevant. The width of the umbra and that of the penumbra can be calculated, in particular, using the distance of the shadow aperture from the shadow receiver. The angular section of the sun's diameter of 0.5° is taken, and the tangent is used to calculate the width of the penumbra. The present invention, on the other hand, analyzes the geometry and intensity of the shadow. No other information about the sun or the like is required. Even other blurring effects, such as cirrus clouds in the upper layers of the atmosphere or high humidity, do not confuse the algorithm of the present invention.

[0043] In order to determine the deviation from the collector position to the optimal position, the position of the shadow of the shadow diaphragm on the shadow receiver, preferably a shadow of the structure, preferably the receiver tube, on the shadow receiver, preferably the support T, will be determined.

[0044] According to the invention, this is preferably achieved using a camera K, preferably an IP camera. The camera should be specifically designed for the ambient conditions. The temperature range and the protection class against water and dust must be considered in particular. Night vision capabilities are generally not important. Parameters such as contrast, sensitivity, and color space within the standard range are sufficient. Line scan cameras or other color brightness digitizing sensors are also preferred.

[0045] When analyzing the shadow, it is particularly preferable to determine two possible deviations. On the one hand, the absolute deviation of the shadow (actual position compared to the target position) can be determined, which results in an angular deviation, e.g., in degrees, or a positional deviation from the center point or the central axis. On the other hand, a deviation that results in only a tendency (e.g., left or right) can be determined. Both approaches are preferred and suitable for reducing and, preferably, eliminating deviations during tracking.

[0046] The camera is preferably installed on the existing structure, preferably on a support of the shadow shield, preferably of the receiver, or on the receiver itself. The camera is preferably arranged between the shadow shield and the shadow receiver.

[0047] Preferred embodiments of the invention are described below by way of example with reference to the drawings. These are merely schematic representations that often omit other (optional) structures to clarify certain aspects or also consider various optional, interrelated aspects in one representation. In this context, the same reference numerals indicate equivalent, similar, comparable, or identical components in the illustrated embodiments.

[0048] The described embodiments can be modified in many ways within the scope of the claims. It should be noted that the features of the above-mentioned embodiments can be combined in a single embodiment. Therefore, depending on the configuration, embodiments of the invention can have all or only some of the above-mentioned features. The disclosure of the figures is not intended to limit the scope of the invention. Preferred embodiments are described below by way of example with reference to the figures. They show: Fig. 1a-1 a schematic representation of a parabolic trough power plant Fig. 1a-2 a schematic representation of its orientation according to the position of the sun Fig. 1a-3 a schematic representation of an exemplary reflector construction with a parabolic trough mirror, Fig. 1b a schematic representation of an exemplary reflector construction with Fresnel mirror collectors, Fig. 1c a schematic representation of an exemplary reflector construction in a central receiver power plant, here a solar tower power plant, Fig. 1d a schematic representation of an exemplary reflector construction in a system with parabolic mirrors or a solar Stirling system, Fig. 2 the schematic structure of a known system with a PV cell sensor, Fig. 3a the example of the shadow cast by a receiver tube of a parabolic trough system in the collector Fig. 3b simplified rendered representation of the shadow cast by a receiver tube of a parabolic trough system in the collector Fig. 3c simplified rendered detail representation of the shadow cast by a receiver tube of a parabolic trough system in the collector Fig. 3d simplified rendered representation of the shadow cast by a receiver tube of a parabolic trough system in the collector Fig.3e simplified rendered detail representation of the shadow cast by a receiver tube of a parabolic trough system in the collector Fig. 4 the geometric conditions of shadow casting using the receiver tube shadow as an example, Fig. 5 a schematic representation of an exemplary shadow of the receiver tube on a shadow receiver with emphasis on the central core shadow and the lateral penumbra Fig. 6 an example of a raw image of a shadow captured by the camera, Fig. 7 a preferred exemplary configuration of a parabolic trough system. Fig. 8 an example visualization of a preferred algorithm with the steps: decomposing the image line into black / white values and / or increasing the contrast ( Fig. 8a ), Selecting multiple image lines ( Fig. 8b ), Determine the shadow entry, exit and penumbra area for each row ( Fig. 8c ),Forming a geometric enclosure for each line to be analyzed ( Fig. 8d ), and calculating the deviation of the actual from the target position ( Fig. 8e ), and Fig. 9 the exemplary structure of a system according to the invention.

[0049] The following explanations describe digital shadow analysis using an IP camera as an example. The technical specifications of a preferred camera can be summarized as follows, purely for example: Image sensor 1 / 3" High Resolution CCD image sensor Effective pixels 768(H) x 494(V) Minimum Illumination 0.3 Lux / F1.4, 0 Lux (IR ON) Lens F6.0mm Lens Angle 48° Electronic Shutter 1 / 60 (1 / 50) to 1 / 100,000 sec. S / N Ratio More than 48dB (AGC off) White Balance Auto AGC Auto IRIS Mode AES Alarms Notification Send image to FTP or email Remote Access Yes Motion Detection Yes Infrared Lamps 56 LEDs IP rating IP67 Infrared Radiation Distance 130 ft. Operating Temperature -10°C~40°C Power Source DC12V

[0050] The analysis of the shadow image captured by the camera can be performed on various hardware platforms. The analysis is not time-critical. For example, cycles of 1 second are preferred. 1 second is intended to demonstrate that the tracking of the collectors is fundamentally not time-critical. On a standard industrial PC, the algorithm described here requires approximately 1 ms, so shorter cycles can also be used. The cycles should preferably be no longer than 60 seconds, more preferably no longer than 30 seconds, and are preferably in the range of 1 ms to 15 seconds, and more preferably from 0.5 seconds to 5 seconds. A known PC or server is preferably used for the analysis. Alternatively, microprocessors / signal processors are preferred, especially for autonomous systems.

[0051] Fig. 6 shows an example of a raw image of a shadow captured by the camera and analyzed by the evaluation unit. The shadow corresponds to the previously defined, especially in connection with Fig. 3 described. The photo according to Fig. 6 shows the shadow on the support T, here the torsion tube of a parabolic trough system, in a resolution of 768x494.

[0052] The raw image can be transmitted via various cabling standards or wirelessly, e.g. via radio, WLAN, Bluetooth, etc. The protocols that can be used are also numerous.

[0053] For a parabolic trough system, the possible system resolution (angle-related) depends in particular on: Distance (position) of the shadow shield to the rotation axis of the parabolic trough Distance (position) of the shadow receiver to the rotation axis of the parabolic trough Position of the camera, angle of the camera Resolution of the camera Resolution of the used algorithm

[0054] A sample calculation is then performed with a system resolution of approximately 0.03° and a minimum measuring range of 2.1°. Further preferred ranges emerge from the overall description. These parameters preferably offer low repeatability and excellent positioning accuracy. The result is preferably independent of weather, irradiance, or contamination.

[0055] Fig. 7 shows a preferred exemplary configuration of a parbolic trough system in cross section ( Fig. 7a ) as well as in schematic three-dimensional view ( Fig. 7b ) and in plan view (without mirror SP, so only substructure visible) ( Fig. 7c ).The system comprises several sealing elements Sp that form a reflector, in this case a parabolic trough. The mirrors focus the incoming sunlight such that it is concentrated onto the receiver, in this case a receiver or absorber tube R. The receiver is arranged at the focal point or in the focal line of the reflector. The system has a rear or support structure for holding the reflector and the receiver. The support structure can be implemented in various ways. The system is trackable, i.e., movable at least along one axis. The preferred embodiment, as shown here, is pivotable along an axis arranged in the region of the lowest point of the parabolic trough. This axis is preferably parallel to the longitudinal axis of the receiver.

[0056] With exemplary reference to this and to previously described figures, in particular Figuren 3 bis 6 , a preferred calculation of the system resolution as well as the determination of the detection and measuring range are discussed below.

[0057] The Fig. 7 The preferred collector design shown has proven particularly advantageous. The design incorporates parabolic trough collectors. The receiver tube serves as the shadow shield. The central torsion tube T of the rear structure performs the function of the shadow receiver.

[0058] The construction according to a preferred embodiment has the following parameters: Parameter Wert Einheit Viewpoint to be observed 256 [mm] Camera resolution (per line) 768 [Pixel] Distance shadow receiver 1905 [mm] Shadow width 110 [mm] Resolution of the algorithm 3 [Pixel]

[0059] The parameters listed above lead to the accuracy calculated below. In principle, it can be said that 768 pixels are sufficient for a significant increase in efficiency and make the system economically viable. With 1920 pixel technology already available as standard, the resolution doubles, so the range between or greater than 768 pixels and 1920 pixels can be used here.

[0060] The following shows an example of how to calculate the system resolution.

[0061] Here a distinction can be made between the resolution of the shadow receiver and the quantity to be measured later, e.g. the deviation of the angle of rotation.

[0062] Relevant sizes for the system resolution of the shadow receiver are preferred the observed viewing angle [mm] the resolution of the camera [pixels] the expected resolution of the algorithm [pixels].

[0063] The Aufl o ¨ sung Schattenempf a ¨ nger = 256 mm / 768 Pixel * 3 Pixel = 1 mm Resolution shadow receiver = 1 [mm]

[0064] Sizes for the system resolution to measure the deviation of the angle of rotation are preferred Resolution Shadow receiver Distance (position) Shadow aperture to shadow receiver

[0065] This determines: Resolution rotation angle = arctan (0.00052) Resolution rotation angle = 0.029794 [°]

[0066] The detection range for the maximum measuring range of the angle of rotation of interest. Relevant values are Width of the shadow receiver Width of the shadow

[0067] When making the following calculations, please note that if the measuring range is halved, e.g. by halving the viewing angle, the resolution doubles (mathematically halved). Messbereich = arctan Bewegungsbereich Schatten mm / Abstand Schattenempfänger mm Messbereich = arctan 1 2 256 mm − 1 2 110 mm / Abstand Schattenempfänger mm Measuring range = ±2.1945 [°]

[0068] The evaluation of the measurement and the algorithm used can be implemented in various ways. A preferred method is as follows (see Fig. 8 ): 1) Copy the image from the camera to the memory 2) Split an image line into black and white values and increase the contrast. This increases the intensity of the shadow along one of the Fig. 8b displayed lines, as in Fig. 8a shown, plotted against the width of the shadow (mm). (cf. Fig. 8a ) 3) This is done for several image lines (preferably at least 2, more preferably at least 4, and especially preferably 6 or more than 6 lines), in particular to detect any localized contaminated areas (e.g., bird droppings) and exclude them from the analysis. (cf. Fig. 8b )However, in the solution according to the invention, soiling is advantageously only problematic in the area of the shadow transition, see line 5 in Fig. 8b . In the shadow itself they have no influence on the measurement result, see line 1 in Fig. 8b . In the example according to Fig. 8 Line 1 is unproblematic, as the contamination occurs within the shadow and not in the transition area. Line 5, where contamination is present in the transition area, was not used for the shadow analysis. 4) Determine the shadow entry, exit, and partial shadow areas for each line. This can be done using adjustable intensity values or intensity thresholds. (see Fig. 8c ) 5) For each line to be analyzed, a kindA quadrilateral, especially a trapezoid, is formed. This is preferably done within the framework of a geometric analysis or image processing. For this purpose, four points are preferably determined: shadow entry and shadow exit (in Fig. 8d left and right outside / bottom) as well as umbra entry and umbra exit (in Fig. 8d left and right outside / top). According to a preferred embodiment, the points can be shifted by a defined buffer value relative to the geometrically determinable value, preferably inwards relative to the trapezoid. The buffer is in Fig. 8eas Δi (lower limit) Δii (upper limit). Δi + Δii can, for example, be between 3 and 15% of the actual intensity (relative to the geometrically determined actual value), preferably around 10%. Alternatively, Δi + Δii can, for example, be between 3 and 15%, preferably around 10%, of a given reference tolerance. Poor visibility conditions, etc., can be preferably counteracted with this method. The determination is preferably independent of the prevailing solar conditions. (cf. Fig. 8d ) 6) The shadow center (actual position) is calculated and compared with the target position. The shadow center lies in the center of the quadrilateral. The X-value (horizontal in Fig. 8e )the deviation from the target position at which the solar radiation is optimally concentrated on the receiver can be calculated. Using this difference, the tracking path or angle can be calculated and tracking can be carried out. The target position preferably corresponds to the geometric center of the shadow receiver. However, a different target position can also be determined, particularly depending on the geometric conditions. The target position can be marked geometrically or graphically or provided as a mechanical, detectable element to be recorded by the camera. An evaluation can then be carried out directly via image processing. Alternatively, the target position can be specified in the image reference. In this variant, the target position can preferably be adjustable and adjusted if necessary.

[0069] According to the system and method according to the invention, an IP camera is preferably used for shadow analysis. The receiver tube preferably serves as the shadow shield, and a support, preferably a so-called torsion tube, preferably serves as the shadow receiver. The camera records the image of the shadow of the shadow shield, and a program analyzes the position of the shadow.

[0070] The system preferably includes (cf. Fig. 9 ) An (IP) camera + cabling, a program for analyzing the signal values, and an interface to the control room. The program is preferably executed directly in the control room – in contrast to the state of the art, where the program, if comparable, is executed in a separate controller.

[0071] The system according to the invention and the method according to the invention have proven to be advantageous, in particular in comparison with the solutions known from the prior art.

[0072] The system according to the invention comprises far fewer components than previously known solutions. This allows for cost savings. The required components are quicker and easier to install and commission. Fewer disciplines are involved or required, resulting in lower personnel costs for development, support, installation, and commissioning. Since all components are serially dependent, i.e., already present in the system or can be supplemented with standard purchased parts, the new solution offers significantly higher availability. In the event of a failure, the faulty component can also be located and replaced more quickly.

[0073] By using a camera, preferably a CCTV camera and particularly preferably an IP camera, the sensor technology is significantly more durable than that of the state of the art, especially in comparison to systems that use components such as PV cells or signal amplifiers, which are subject to degeneration and sometimes have considerable component deviations. Far less maintenance is also required. By using high-quality series products, maintenance is sometimes virtually unnecessary. The cleaning cycles are also considerably longer than with existing systems, on average in a ratio of 1 to 10. The system according to the invention also proves advantageous in the event of a defect. Even after many years, individual components can be replaced without the overall system imposing restrictions. When replacing the camera, for example, only the technology needs to be network-compatible.Resolution, speed (frames per second), size, and many other parameters are irrelevant or limited. Some of them can be parameterized via software. Finally, compared to PV cell sensors, there are significantly more manufacturers to choose from. Finally, the camera's position in the system is not limited to a specific location where it must be mounted. It only needs to detect the shadow in the recording area.

[0074] The cabling in the system described here is reduced. This results in cost savings in procurement. In particular, various types of cabling such as signal cables, control cables, and network cables are eliminated, leaving only a single network cable. The cabling is also cheaper to install because only one discipline (the network cable) is involved. By favoring wireless transmission technology, such as WLAN technology (industrial WLAN), even the network cable can be eliminated. This results in fewer plug connections overall, leading to fewer sources of error and thus fewer (EMC) problems.

[0075] The use of digital image processing is simple, cost-effective, and future-proof. Even if the platform changes, such as the operating system or hardware, the system remains usable. There is generally no need for expensive, long-term maintenance contracts. Performance improvements can also be easily achieved through software / algorithm updates, particularly without having to intervene in the mechanical and structural components. In comparison, a solution using PV cells would require the development of a new sensor, which would incur enormous costs just for replacement in the field. Digital image processing can be used to observe and roughly measure irradiance values. This can be used, for example, to perform a rough weather analysis, e.g., "clear day" versus "humid" or "cloudy." Finally, greater precision, preferably by approximately 0.3°, can be achieved compared to conventional systems.Such increased precision increases the overall efficiency of a standard industrial collector by approximately 3%. This means the operator requires 3% less land or achieves a 3% higher yield – with lower acquisition and maintenance costs. The system is also significantly less sensitive and can respond better to localized contamination (e.g., bird droppings) and dust, compensating for the results better than conventional systems. Finally, remote maintenance is also significantly simplified. The system can also be used to roughly measure the irradiation situation. The present invention also allows the system's performance to be controlled in a targeted manner, for example, through a deliberate "deviation" from the optimal orientation.

[0076] Where the above description uses the term "essentially," this also encompasses embodiments in which the respective feature is present entirely or completely. The words "plurality" or "multiple" are to be understood in the sense of "at least two," i.e., two or more. Where specific values are specified, these preferably also include minor deviations from these values, such as deviations of + / -10% or + / -5% of the respective value. Individual aspects of the invention may constitute independent inventions and thus be claimed as such.

Claims

1. A CSP system comprising a reflector, the reflector being a parabolic trough, and a receiver, the receiver being a receiver tube, for concentrating the solar radiation incident on the reflector onto the receiver, comprising a shadow blind, the shadow blind being the receiver tube, and a shadow receiver as well as a colour and / or brightness digitizing sensor and a tracking means configured to adapt the position of the reflector and the receiver according to a deviation of an actual shadow position from a target shadow position, characterized in that the sensor is a camera arranged to detect the shadow of the shadow blind on the shadow receiver in order to determine the deviation of the actual shadow position from the target shadow position by digital image processing.

2. The CSP system according to claim 1, wherein the arrangement is configured such that, when the reflectors are optimally aligned with respect to the sun, the shadow SR of the shadow blind falls onto the shadow receiver at a predetermined position, preferably centrically.

3. The CSP system according to any one of the preceding claims, wherein the camera is fixed at the existing structure, preferably at a beam of the shadow blind, preferably of the receiver, or at the receiver itself.

4. The CSP system according to any one of the preceding claims, wherein the camera is arranged between the shadow blind and the shadow receiver.

5. The CSP system according to any one of the preceding claims, wherein the evaluation cycle of the shadow detected by the sensor is about 1 second or less.

6. The CSP system according to any one of the preceding claims, wherein the system, preferably the controller, is configured (1) to copy an image from the camera into a memory, (2) to evaluate the image, preferably in that a scan line is decomposed into black-and-white values and / or the contrast is increased, (3) wherein step (2) is preferably carried out for several scan lines, (4) wherein the shadow entrance, exit and penumbra region are determined for each line, (5) wherein a rectangle is formed for each line to be analyzed, (6) wherein the shadow centre (actual position) is calculated and compared with the target position, and wherein (7) tracking is accordingly performed.

7. The use of a CSP system according to any one of the preceding claims to track the position of the sun with the system.

8. A method for tracking a CSP system with a CSP system according to any one of the preceding claims, comprising at least the following steps: detecting the shadow of a shadow blind on a shadow receiver, image processing of the shadow and determining the shadow position relative to a reference position, tracking the CSP system.

9. The method according to claim 8, wherein tracking is performed by a value that is proportional to the value of the deviation of the shadow position from the reference position.

10. The method according to claim 8 or 9, wherein firstly an image from the camera is copied into a memory, wherein then a scan line is decomposed into black-and-white values, wherein then the intensity of the shadow is determined over the width of the shadow, wherein this is preferably carried out for several scan lines, most preferably at least 2, more preferably at least 4 and most preferably 6 or more than 6 lines, wherein further the shadow entrance, exit and penumbra region are determined for each line, and wherein subsequently the shadow centre is calculated and compared with the reference position of the shadow, finally the tracking path or angle is calculated via this difference and tracking is performed.