METHOD FOR TRANSFERRING SEDIMENT IN A BODY OF WATER

Description

[0001] The present invention relates to a method for transferring sediment in a body of water, wherein the body of water is part of a waterway in which a hydroelectric power plant is located. The body of water typically includes a reservoir.

[0002] Sediment transfer processes are implemented in sections of watercourses threatened by siltation. These are watercourses that are dammed in some way or whose outflow is naturally inadequate for the sufficient removal of the accumulating sediment. In particular, sections of watercourses containing hydropower plants are often at risk of siltation. This includes pumped-storage power plants with natural upper reservoirs, storage power plants, and run-of-river power plants. Most of the sediment is introduced into the affected section of the watercourse by natural inflows. Besides combating siltation, such a process offers the further advantage of restoring the sediment permeability of hydropower plants.

[0003] WO 2019 / 161996 A1 discloses a method for transferring sediment in bodies of water, which may be reservoirs of hydroelectric power plants, such as pumped-storage power plants. Sediment is drawn from the bottom of the body of water via a suction line, a sediment intake device, and a pressure line for transferring the collected sediment, and then transferred to another location. In some of the described embodiments, the sediment is transferred to the vicinity of a discharge device or into the discharge device of the body of water itself. The discharge device may be connected to a power plant unit, for example, a turbine. Ultimately, the sediment reaches a tailrace. Furthermore, during the transfer process, the concentration of the transferred sediment is measured using a measuring device, and the concentration is adjusted to create near-natural conditions in the tailrace.

[0004] Another method for transferring sediment in a body of water is disclosed in DE 10 2007 016679 A1. DE 10 2007 016679 A1 discloses a method with the features of the preamble of the first claim.

[0005] The inventors have recognized that the method disclosed in WO 2019 / 161996 A1 can cause erosion damage (i.e., abrasive wear) to parts of a hydroelectric power plant connected to the outlet of the water body.

[0006] The object of the invention is to provide a method for transferring sediment in a body of water, wherein the body of water is part of a waterway in which a hydroelectric power plant is located, in which erosion damage to parts of a hydroelectric power plant can be minimized as much as possible, i.e., kept as small as possible.

[0007] The problem is solved according to the invention by a method according to claim 1. Further advantageous features of the embodiment according to the invention are found in the dependent claims.

[0008] The inventive method is explained below with reference to the figures. The figures show in detail: Fig. 1 Body of water in which a method according to the invention is carried out

[0009] Figure 1Figure 1 shows a highly schematic representation of a body of water on which a method according to the invention is carried out. The body of water is designated by 1. It typically includes a reservoir, which is designated by 7. The term reservoir is understood to encompass any part of the body of water that is impounded or dammed in any way. It can therefore also simply be a section of a flowing watercourse upstream of a hydropower plant. A discharge device, designated by 3, is arranged in the body of water. The discharge device 3 can be designed in various ways, e.g., as a discharge near the bottom of the watercourse, as an opening in a dam, or as an inlet of any design for a hydropower plant (e.g., as an intake screen).The outlet 3 is connected to a hydroelectric power plant, designated 2, by means of a connecting pipe, designated 6, such that water from the reservoir 7 can flow through the connecting pipe 6 to the hydroelectric power plant. The water then passes through the hydroelectric power plant and finally enters a tailrace, which is located in . Figure 1 The arrow indicates the direction towards the tailrace. If the hydropower plant 2 is a pumped-storage power plant, the water can, of course, also flow in the opposite direction during pumping, i.e., from the tailrace to the reservoir 7. However, this flow direction is irrelevant for the method according to the invention. The connecting pipe 6 is generally the so-called penstock of the hydropower plant. However, it could also be a canal or other waterway.

[0010] Figure 1Figure 4 further shows a device for supplying a sediment-water mixture, which is designated 4. Device 4 is connected to the connecting pipe 6 between the reservoir 7 and the hydroelectric power plant 2 in such a way that the sediment-water mixture supplied by device 4 can be introduced into the connecting pipe 6 and thus discharged by the water flow in the connecting pipe 6 through the hydroelectric power plant 2 into the tailrace. The connection between device 4 and the connecting pipe 6 can be opened via the discharge device 3 as shown in Figure 4. Figure 1The process can be described or carried out in other ways. According to the inventive method, sediment is first collected in the reservoir 7. The collected sediment is then transferred to the device 4, and finally, in the form of the sediment-water mixture provided by the device 4, it is introduced into the connecting pipe 6. In this way, sediment is transferred within the body of water 1, i.e., from the reservoir 7 into the downstream area through the hydropower plant 2.

[0011] The device 4 for supplying a sediment-water mixture is located somewhere in, on, or near the reservoir 7. The device 4 for supplying a sediment-water mixture could, for example, be a movable device on the water body 1, as described in WO 2019 / 161996 A1. However, the device 4 could equally well be located on the bottom of the water body, on the bank of the reservoir 7, or on a structure in the water body 1. It is also conceivable that the device 4 is located in the outlet 3 itself or in or on the connecting pipe 6 between the outlet 3 and the hydroelectric power plant 2. In any case, the sediment-water mixture supplied by the device 4 is introduced into the connecting pipe 6. This can be done, for example, by a pipe extending from the device 4 to the outlet 3, into which this pipe empties, as described in [reference to relevant document]. Figure 1 depicted.

[0012] The sediment-water mixture provided by Facility 4 consists of sediment and water extracted from or withdrawn from reservoir 7. Extraction can be carried out as described in WO 2019 / 161996 A1, with the sediment-water mixture being generated directly during the extraction process. Facility 4 has the resources described in the aforementioned document. Alternatively, sediment and water can be extracted separately. For example, sediment can be removed from reservoir 7 using a floating dredger, such as a bucket dredger or a submarine, and then conveyed to Facility 4, perhaps via another floating device. The water for the mixture can, for example, simply be pumped from body of water 1. Facility 4 then generates the sediment-water mixture by blending the individual components, and in this case, the facility must have the appropriate resources for doing so.This could include, for example, a container for storing sediment, into which the floating device periodically introduces sediment.

[0013] In any case, facility 4 has means for monitoring the sediment concentration in the provided sediment-water mixture. This monitoring can be carried out using measuring instruments capable of determining the concentration. Alternatively, it can be achieved by measuring and controlling the quantity of sediment and water used to prepare the sediment-water mixture.

[0014] Figure 1Figure 5 further shows a control device, designated 5. The control device 5 is connected to the device 4 for supplying a sediment-water mixture in such a way that it can control the amount of sediment contained in the supplied sediment-water mixture. The amount of sediment-water mixture introduced into the connecting pipe 6 can also be controlled, since, given a known sediment concentration, the amount of sediment is also controlled. The connection between the control device 5 and the device 4 can also be wireless. Furthermore, the control device 5 can also be connected in such a way that the control device 5 and the device 4 form a single unit. The control device 5 is also connected to the hydropower plant 2 in such a way that the control device 5 can use data about the current operating mode of the hydropower plant 2 to control the device 4.The connection to the hydropower plant 2 can also be wireless. Furthermore, the control unit 5 can also be part of the hydropower plant 2. In this case, the control unit 5 can also be integrated into the control unit that regulates the operation of the hydropower plant 2.

[0015] The inventors recognized that the erosive effect of sediment added to the water powering a hydroelectric plant depends on the plant's operating mode. Therefore, it is advantageous for the control unit 5 to regulate the device 4 in such a way that the amount of sediment introduced into the connecting pipe 6 per time interval does not exceed a predefined maximum permissible quantity, thus minimizing erosion damage to parts of the hydroelectric plant. The applicable maximum permissible amount of sediment depends on the current operating mode of the hydroelectric plant 2. This ensures that, on the one hand, erosion damage to the hydroelectric plant 2 is minimized, and on the other hand, that as much sediment as possible is removed within a given period.

[0016] The phrase "that the maximum permissible amount of sediment depends on the current operating mode of the hydropower plant" is to be understood as meaning that there is at least one operating mode of the hydropower plant in which the maximum permissible amount of sediment that may be introduced into the connecting pipeline when the hydropower plant is operating in this mode differs from a maximum amount of sediment that may be introduced into the connecting pipeline when the hydropower plant is operating in a different mode. This difference in the maximum permissible amount of sediment is determined excluding other influencing factors (su), i.e., these factors are only considered as parameters with the same values ​​when determining the respective maximum amounts of sediment.Specifically, there is a first operating mode B1 with an associated maximum sediment quantity max_S1 and a second operating mode B2 with an associated maximum sediment quantity max_S2, where B1 ≠ B2 and max_S1 ≠ max_S2, and where all other possible influencing factors are considered constant. Analogous definitions apply to the additional dependencies mentioned in the dependent claims.

[0017] The operating mode of a hydropower plant encompasses every conceivable state of the plant in which water flows through it, such as operation at nominal load, overload, or minimum load. The operating mode is typically controlled by continuously adjustable control elements, such as a guide vane or a nozzle as in Pelton turbines. Therefore, even in hydropower plants with continuously adjustable control elements, the operating mode is a continuously variable parameter.

[0018] The predefined maximum permissible sediment levels can be determined in various ways. For example, CFD and other mathematical methods can be used to calculate the extent of erosion damage caused by a specific amount of sediment in the turbine water under different operating conditions of the hydropower plant. This erosion damage is generally inhomogeneously distributed, meaning that certain components or zones within specific components suffer particularly high levels of erosion depending on the operating conditions. Naturally, the properties of the individual components are taken into account, especially their resistance to abrasive wear, which can be increased, for example, through appropriate material selection or a suitable coating.The determination of the respective maximum values ​​may include considerations that take into account the costs of the respective damaged components or the effort required for their replacement or repair. Alternatively, the maximum permissible sediment quantities in the turbine water can also be determined experimentally, for example, in a model test or at a pilot plant. In any case, to determine the predefined maximum permissible sediment quantity, the respective extent of erosion damage to parts of the hydropower plant (2) is determined beforehand for the relevant sediment quantity and operating mode.

[0019] The inventive method can be further improved if, when introducing the sediment into the connecting pipe, the properties of the sediment contained in the sediment-water mixture are also taken into account. This means that the maximum permissible amount of sediment then additionally depends on the properties of the sediment currently being introduced. This can be achieved in various ways. In some cases, the method can be satisfactorily improved simply by considering the properties of the sediment typically present in the respective body of water. This is particularly sufficient if the body of water has a homogeneous structure and does not exhibit significant variations over the course of the seasons. If the body of water exhibits a high degree of inhomogeneity, then, for example, the source of the sediment currently being introduced into the connecting pipe 6 can be considered.If the seasons play a significant role in the body of water in question, they can be taken into account by varying the maximum permissible amount of sediment introduced depending on the season. In general, the method according to the invention can be improved by considering the quantity and / or nature of sediment naturally present in the water flowing through the turbine, i.e., the sediment already in the water flowing into the outlet 3 before it is introduced by the device 4 into the connecting pipe 6. Understandably, the quantity and nature of all sediment in the turbine flow is responsible for erosion, regardless of whether the sediment is naturally present or introduced into the connecting pipe 6 by the device 4. This influence can also vary considerably with the seasons.

[0020] The composition of the sediment, including grain size as well as its chemical and physical properties (e.g., hardness or roughness), influences its erosive effect. These parameters can be measured using suitable measuring instruments of unit 4, or, as indicated above, determined by other means (e.g., via the location of sediment extraction in the water body) and taken into account when introducing it into the connecting pipe 6. This means that the maximum permissible sediment quantities can also depend on these parameters.

[0021] The method according to the invention can also be improved by actively determining certain properties of the sediment introduced into the connecting pipe 6 depending on the current operating state of the hydropower plant 2. For example, the sediment taken up from the reservoir 7 can be divided into several groups with respect to a specific composition and separated accordingly before being introduced into the connecting pipe 6. For example, the sediment can be divided into several groups with respect to grain size and separated, so that sediment with grain sizes in a first grain size range is stored in a first container, and sediment with grain sizes in a second grain size range is stored in a second container, and so on. Depending on the operating mode of the hydropower plant 2, a first maximum quantity of sediment is then drawn from the first container and a second maximum quantity of sediment from the second container, and so on.per unit of time introduced into connecting pipe 6, whereby all values ​​of the stated maximum quantities may depend on the respective operating mode. In other words, the maximum permissible amount of sediment that may be introduced into connecting pipe 6 depends on the group from which the sediment is taken.

[0022] Separation according to grain size can be achieved using suitable sieves.

[0023] It should be noted that in certain operating modes it may also be the case that no sediment at all, or no sediment of a certain nature, may be introduced into the connecting pipe 6, i.e. that the corresponding maximum values ​​are zero.

[0024] The method according to the invention enables the minimization of erosion damage caused by sediments in the drive water to parts of a hydropower plant. An additional advantage is that, by controlling the amount of sediment introduced, it is possible to calculate the resulting erosion damage. This allows necessary repair and maintenance work to be predicted and planned, thereby minimizing downtime of the hydropower plant. Reference symbol list

[0025] 1. Water body 2. Hydropower plant 3. Outlet 4. Device for providing a sediment-water mixture 5. Control device 6. Connecting pipe 7. Reservoir

Claims

1. A method for transferring sediment in a body of water (1), wherein a discharge member (3) is arranged in the body of water (1), which is connected to a hydropower plant (2) by a connecting pipe (6) in such a way that water can flow from the body of water (1) through the connecting pipe (6) to the hydropower plant (2), and wherein a device (4) for providing a sediment-water mixture is connected to the connecting pipe (6) in such a way that provided sediment-water mixture can be introduced into the connecting pipe (6), and wherein the device (4) comprises means for controlling the sediment concentration in the sediment-water mixture provided, that provided sediment-water mixture can be introduced into the connecting pipe (6), and wherein the device (4) comprises means for controlling the sediment concentration in the provided sediment-water mixture, and wherein a control device (5) is connected to the device (4) such that it can control the amount of sediment introduced into the connecting pipe (6), and wherein the method comprises the following steps: - Collecting sediment in the water body (1); - transferring sediment to the device (4) for providing a sediment-water mixture; - introducing the sediment-water mixture provided into the connecting pipe (6); wherein the control device (5) controls the device (4) in such a way that the quantity of sediment introduced into the connecting pipe (6) per time interval does not exceed a predefined maximum permissible quantity in order to minimise erosion damage to parts of the hydropower plant (2), wherein the predefined maximum permissible quantity of sediment depends on the current mode of operation of the hydropower plant (2), and characterised in that the predefined maximum permissible quantity of sediment depends on the nature of the sediment currently introduced into the connecting pipe (6).

2. Method according to claim 1, wherein the predefined maximum permissible quantity of sediment is dependent on the season.

3. Method according to one of the preceding claims, wherein the predefined maximum permissible quantity of sediment is dependent on the area of the body of water (1) from which the sediment currently introduced into the connecting pipe (6) originates.

4. Method according to one of the previous claims, wherein the predefined maximum permissible quantity of sediment is dependent on the quantity and / or nature of the sediment currently naturally present in the water flowing into the outlet member (3).

5. Method according to claim 1, wherein the nature of the sediment is the grain size of the sediment.

6. Method according to claim 1, wherein the nature of the sediment is the hardness of the sediment.

7. Method according to one of the preceding claims, wherein properties of the sediment introduced into the connecting pipe (6) are actively determined as a function of the current operating state of the hydroelectric power plant (2).

8. Method according to claim 7, wherein the sediment taken up from the body of water (1) is categorised into a plurality of groups with regard to a specific quality before being introduced into the connecting pipe (6) and is separated in this respect.

9. Method according to claim 8, wherein the groups are categorised with respect to the grain size and the sediment is separated accordingly.

10. Method according to one of claims 8 or 9, wherein the predefined maximum permissible quantity of sediment which may be introduced into the connecting pipe (6) is dependent on the group from which the sediment is taken.

11. Method according to one of the preceding claims, wherein erosion damage to parts of the hydropower plant (2) caused by the sediments introduced into the connecting pipe (6) is calculated.