Solar thermal power plant and method for operating same

Abstract

The invention relates to a solar thermal power plant (1) comprising a plurality of collector mirrors (9) which are parallel to an absorber tube (10), wherein the collector mirrors (9) are each elevated on a support frame (8) which can each be pivoted by means of at least one electric drive (2), wherein each electric drive (2) of a support frame (8) is assigned to a storage battery (3) so that the power supply to the electric drive (2) is not interrupted in the event of a power failure.

Description

[0001] SOLAR THERMAL POWER PLANT AND METHOD FOR OPERATING SUCH A PLANT

[0002] The present invention relates to a solar thermal power plant comprising a plurality of collector mirrors arranged parallel to an absorber tube, wherein the collector mirrors are each mounted on a support frame which can be pivoted by means of at least one electric drive, and to a method for operating such a power plant.

[0003] Such solar thermal power plants are already known. In an existing solar field, incoming sunlight is concentrated using collector mirrors mounted on a support structure and directed onto an absorber tube, which runs elevated above collector mirrors mounted on a support structure. The light rays concentrated by the collector mirrors heat a heat transfer medium located in the absorber tube. The heat energy thus generated can then be converted into electrical energy using a power machine. To focus the collector mirrors onto the absorber tube, the collector mirrors are mounted on a movable support structure. Several control units are arranged in the area of ​​the support structure, which control electric drives in the form of linear motors for moving the support structure.

[0004] Uninterruptible power supplies are typically used in solar thermal power plants to ensure that critical electrical loads can continue to operate even in the event of disruptions or grid failures. Critical loads are usually those that perform a safety-relevant function. The uninterruptible power supply is often implemented as a battery consisting of accumulators.

[0005] Such a solar array has a modular structure consisting of several parallel collector loops. Each loop, in turn, consists of several control units arranged in series. Each control unit has two linear motors that track the mirrors and thus direct the concentrated solar radiation onto the absorber tube. The linear motors are the safety-relevant consumers of the solar array, as their orientation controls the heat input.

[0006] In the event of a power outage, the collector mirrors would remain in their position, which in turn could lead to overheating of the absorber tube. Therefore, an uninterruptible power supply in the form of a storage battery is connected to the overall power supply of the solar thermal power plant in an existing solar field.

[0007] However, this has the disadvantage that in the event of a failure of the uninterruptible power supply, the entire solar field is affected. While this can be avoided by using a second storage battery, it increases complexity and costs. Furthermore, the operating voltage required for the entire power supply is 400 V AC, whereas the electric drives for controlling the movement of the support structure typically require an operating voltage of only 24 V DC. Therefore, the power must first be converted before it can be used by the electric drives. The uninterruptible power supply is therefore very inefficient and poses an increased safety risk in the event of a failure.Against this background, the present invention is based on the object of creating a solar thermal power plant and a method for operating such a plant that provides a reliable, uninterrupted power supply that is also highly efficient. The power supply should function without interruption so that the electric drives are continuously supplied with power and the solar thermal power plant is protected from overheating.

[0008] This is achieved by a solar thermal power plant according to the features of independent claim 1 and by a method for operating such a solar thermal power plant according to the features of independent claim 7. Further useful embodiments of such a solar thermal power plant and of a method for operating such a plant can be found in the respective subsequent dependent claims.

[0009] A solar thermal power plant is provided comprising several collector mirrors arranged parallel to an absorber tube. Each collector mirror is mounted on a support frame, which can be pivoted by means of at least one electric drive. According to the invention, each electric drive of a support frame is assigned a storage battery to ensure uninterrupted power supply to the electric drive in the event of a power failure.

[0010] In its specific form, a solar thermal power plant comprises an absorber tube containing a heat transfer medium that melts when heated. Molten salt, with its melting point of several hundred degrees Celsius, is particularly suitable for this purpose. Collector mirrors can be arranged along the absorber tube, mounted on a support frame. The collector mirrors can be illuminated by sunlight and pivoted with the support frame via an electric drive. Depending on the position of the sun, the collector mirrors are pivoted into the position where they direct the concentrated light rays onto the absorber tube to heat the heat transfer medium. The pivoting of the frame is accomplished by at least one electric drive.This electric drive can be powered by the solar thermal power plant's overall power supply or, in the event of a power outage, operated by a dedicated storage battery. This ensures that all electric drives continue to receive power in the event of a power outage and can adjust the position of the collector mirrors located on the support structure. In the event of a power outage, the power plant will no longer operate, as the continued pumping of the heat transfer medium is also compromised. The heat supply to the absorber tube is stopped by moving the collector mirrors to a safe position using the electrical energy provided by the storage batteries.

[0011] In a specific embodiment, at least one electric drive can be controlled by a control unit. This has the advantage that the control unit can include a sensor that measures the operating voltage. In the event of a power failure, the power supply of the at least one electric drive can be switched to the storage battery.

[0012] Preferably, several control units can be arranged at a distance from one another on the support frame. The use of multiple control units has the advantage that only small sections of the support frame can be moved simultaneously. Each control unit can be connected to one or more electric drives. In the event of a simultaneous power failure and a storage battery failure, only one of several electric drives would cease functioning. This would allow parts of the support frame to continue moving to protect them from overheating.

[0013] The invention can provide for at least one drive to be designed as a linear motor, preferably operable with a DC voltage of 24 V. The electric drive can pivot the collector mirrors located on the support frame into specific positions for focusing the bundled light beams. The support frame can perform a translational movement in one direction for each linear motor. A DC voltage of, for example, 24 V can be provided by the storage battery without voltage conversion. Thus, the use of linear motors operable with a DC voltage of 24 V is very efficient.

[0014] In a specific embodiment, a central power supply can be provided, preferably providing an AC voltage of 400 V, which is connected to the control units via a voltage conversion interface. The control units of the solar thermal power plant are supplied with power by the central power supply. Since the control units preferably operate linear motors, which require a DC voltage of 24 V, the current of the central power supply is converted to the various levels. This can be done in an interface between the control units and the central power supply.

[0015] Preferably, several control units can be combined into a single supply circuit. In this case, it may be useful for individual storage batteries to temporarily supply power to neighboring drives in an emergency.

[0016] The method for operating a solar thermal power plant according to the invention allows at least one electric drive to be supplied with power without interruption in the event of a power failure using a storage battery, and at least one collector mirror pivotably mounted on a support frame can be pivoted into a safety position. The safety position is characterized by the collector mirrors being in a position in which the solar thermal power plant is protected from overheating.

[0017] In a specific design, the storage battery capacity can be selected to be sufficient to move the support frame to the safety position using the electric drive from any position of the collector mirror. The battery can have sufficient capacity to operate at least one electric drive for the time required to reach a safe position of the support frame. In the safety position, the bundled light beams are not focused on the absorber tube, and the solar thermal power plant is protected from overheating.

[0018] In a specific design, in the safety position, a focal line of the collector mirrors can be located above, preferably centrally above, the collector mirrors. In this position, the collimated light beams are not directed toward the absorber tube, and it is a position that can be reached relatively quickly from all other positions.

[0019] The invention described above is explained in more detail below using an exemplary embodiment.

[0020] It shows

[0021] Figure 1 shows a supporting structure in a solar thermal power plant with attached collector mirrors and an absorber tube in perspective view,

[0022] Figure 2 shows the supporting structure according to Figure 1 with attached collector mirrors and an absorber tube in a side view, as well as

[0023] Figure 3 shows a schematic representation of a solar thermal power plant.

[0024] Figure 1 shows a perspective view of a support frame 8 in a solar thermal power plant 1. As a whole, a solar thermal power plant 1 comprises a plurality of absorber tubes 10, which are mounted elevated relative to an array of collector mirrors 9. The collector mirrors 9 are pivotably mounted on the support frame 8 via electric drives 2. Since the collector mirrors 9 are intended to concentrate the incoming sunlight and direct it onto the elevated absorber tube 10, they must be aligned depending on the position of the sun and the time of day. Only when the light rays are focused on the absorber tube 10 can the heat transfer medium contained therein be heated and the solar thermal power plant 1 be operated.

[0025] Figure 2 clearly shows that the absorber tube 10 is a tube located above the support frame 8. To focus the light rays onto the absorber tube 10, precise electric drives 2 are required, which pivot the support frame 8 and the collector mirrors 9 located thereon, thus tracking the position of the sun. The solar energy focused onto the absorber tube 10 heats a molten salt contained within the absorber tube 10, which serves as a heat transfer medium. The salt is pumped through the absorber tube 10, and the energy absorbed therein is ultimately used to generate electricity.

[0026] However, the case of a power outage is problematic. If the salt is no longer pumped but continues to be heated by the collector mirrors 9 in the absorber tube 10, which remain focused even during a power outage, this can lead to overheating and, in extreme cases, damage to the system. This scenario must therefore be avoided.

[0027] The solar thermal power plant 1, as shown in Figure 3, has a central power supply 7 which, in normal operating conditions, powers all electrical consumers within the power plant, including electric drives 2 which move the collector mirrors on their support frames. If the central power supply 7 fails, distributed storage batteries 3 are provided in the solar thermal power plant 1 which supply the electric drives 2 with power in the event of a power failure. The electric drives 2 are arranged at a distance from one another on the support frame 8 and are controlled by means of control units 4. The control units 4 are connected to the central power supply via an interface 5 and, in normal operation, ensure data transmission and the conversion of the central voltage from 400 V alternating or three-phase current to the operating voltage of the electric drives 2 of 24 V direct current.In this case, the voltage supply 6 is provided from the central overall power supply 7 to the individual control units.

[0028] If the overall power supply 7 fails, the required defocusing of the collector mirrors 9 can no longer be carried out via the power supply 6. A storage battery 3 is therefore provided for each control unit 4, which can continue to supply the electric drives 2 connected to the control unit 4 with power without interruption. The stored energy is at least sufficient for the control unit 4 to detect the power failure, issue a control signal to the electric drives 2, and move them to a safe position in which the focal line of the respective collector mirror 9 is located centrally above the collector mirror 9 itself. In this position, it is ensured that the absorber tube 10 is no longer heated by the collector mirror 9. Even if other consumers fail in addition to the power failure, defocusing as many collector mirrors 9 as possible can avert damage to the system.

[0029] The above description describes a solar thermal power plant that provides a reliable, uninterrupted power supply that also boasts high efficiency. The power supply operates without interruption, the electric drives are continuously supplied with power, and the solar thermal power plant is protected against overheating.

[0030] 1 Solar thermal power plant 2 Electric drive

[0031] 3 storage battery

[0032] 4 Control unit

[0033] 5 Interface

[0034] 6 Power supply 7 Total power supply

[0035] 8 Support structure

[0036] 9 collector mirrors

[0037] 10 absorber tube

[0038] 11 Supply circuit

Claims

AMENDED CLAIMS received by the International Bureau on 23 July 2024 (23.07.2024) 1 . Solar thermal power plant comprising a plurality of collector mirrors (9) arranged parallel to an absorber tube (10), wherein the collector mirrors (9) are each mounted on a support frame (8) which can be pivoted by means of at least one electric drive (2), wherein a molten salt is located in the absorber tube (10) as a heat transfer medium, and the collector mirrors (9) can be pivoted into a position in which they direct bundled light beams onto the absorber tube in order to heat the heat transfer medium above its melting point, characterized in that each electric drive (2) of a support frame (8) is assigned a storage battery (3) for the uninterrupted power supply of the electric drive (2) in the event of a power failure, with the aid of which storage battery the collector mirrors (9) can be pivoted into a safety position in which the solar thermal power plant is protected from overheating.

2. Solar thermal power plant according to claim 1, characterized in that at least one electric drive (2) can be controlled by a control unit (4).

3. Solar thermal power plant according to one of the preceding claims, characterized in that several control units (4) are arranged spaced apart from one another on the support structure (8).

4. Solar thermal power plant according to one of the preceding claims, characterized in that at least one electric drive (2) is designed as a linear motor, which is preferably operable with a direct voltage of 24 V. AMENDED SHEET (ARTICLE 19) 5. Solar thermal power plant according to one of the preceding claims, characterized in that a total power supply (7) is provided, which preferably provides an alternating voltage of 400 V and which is connected to the control units (4) via an interface (5) for voltage conversion.

6. Solar thermal power plant according to one of the preceding claims, characterized in that several control units (4) are combined at an interface (5) to form a supply circuit (6).

7. Method for operating a solar thermal power plant according to one of the preceding claims, characterized in that in the event of a power failure, at least one electric drive (2) is supplied with power without interruption by means of a storage battery (3) and pivots at least one collector mirror (9) pivotably arranged on a support frame (8) into a safety position in which the solar thermal power plant is protected from overheating.

8. Method according to claim 7, characterized in that the capacity of the storage battery (3) is sufficient to move to the safety position of the support frame (8) with the aid of the electric drive (2) from any position of the collector mirror (9).

9. Method according to one of claims 7 or 8, characterized in that in the safety position a focal line of the collector mirrors (9) lies above, preferably centrally above, the collector mirrors (9). AMENDED SHEET (ARTICLE 19)

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