System for monitoring the fill level of a container

Abstract

System for monitoring the fill level of a container (1), comprising: - A container (1) for receiving a measuring medium (11), which has an inlet (13), an outlet (14) and an overflow outlet (15), wherein the inlet (13) is designed to convey measuring medium (11) into the container (1) at a variable flow rate, wherein the outlet (14) is designed to convey measuring medium (11) out of the container (1) at a limited flow rate, and wherein the overflow outlet (15) is arranged on the container (1) and is designed to convey excess measuring medium (12) out of the container (1) through the overflow outlet (15) if the measuring medium (11) exceeds a predetermined fill level (h) in the container (1); - A field device (2) designed to determine the fill level of the container (1); and - A generator (3) wherein, in the event of an overflow, the excess measuring medium (12) drives the generator (3) to generate electrical energy and which is designed to supply the field device (2) with electrical energy when the generator (3) is driven by the excess measuring medium (12), characterized in that the field device (2) is designed to operate in a first and a second operating mode, wherein the field device (2) is designed to operate in the first operating mode during a period in which the field device (2) is not supplied with electrical energy by the generator (3) and wherein the field device (2) is designed to switch to the second operating mode during a period in which the field device (2) is supplied with electrical energy by the generator (3).

Description

[0001] The invention relates to a system for monitoring the fill level of a container, comprising a container, a field device and a generator.

[0002] Field devices are already known from the state of the art and are used in industrial plants. They are widely employed in process automation as well as in manufacturing automation. In principle, field devices are defined as all devices that are used close to the process and that provide or process process-relevant information. Thus, field devices are used to acquire and / or influence process variables. Measuring devices or sensors are used to acquire process variables. These are used, for example, for measuring pressure and temperature, conductivity, flow rate, pH, level, etc., and acquire the corresponding process variables such as pressure, temperature, conductivity, pH value, level, and flow rate. Actuators are used to influence process variables.These include, for example, pumps or valves that can influence the flow of a liquid in a pipe or the fill level in a container. In addition to the aforementioned measuring devices and actuators, field devices also include remote I / Os, radio adapters, and generally any devices located at the field level.

[0003] A large number of such field devices are produced and distributed by the Endress+Hauser Group.

[0004] Rainwater collection basins are often located in remote areas without access to electricity or communication lines. Remotely controlled field devices with wireless communication links, powered by batteries or solar energy, are used to detect overflow events. This raises the following problems: - Power consumption: Batteries with a large capacity and therefore a long lifespan are expensive, require regular replacement, and cause environmental problems due to the inevitable replacement at the end of their service life. Furthermore, special care must be taken to reduce the power consumption of the entire measuring system in order to maximize battery life. - Accuracy: Due to the limited battery capacity, the overflow is not normally checked continuously, but only at specific times. Sudden, short periods of overflow can lead to significant inaccuracies in the measurement. To avoid the second issue, the system is often equipped with an additional level switch that detects a predetermined fill level in the basin and thus only activates the field device in the event of an actual overflow. However, such a level switch incurs additional costs and also requires electrical power from the battery. Since solar energy is only available when the weather is sufficiently good and overflow events are unlikely under such weather conditions, large accumulators are needed. These store the generated electrical energy to ensure operation at night and during bad weather, when overflows are most likely to occur.

[0005] US20150033722A1 describes a turbine system that can be anchored in a fluid flow, such as a waterfall, to generate energy. It includes a rotor, a pressure pipe, an inlet valve, a level sensor, a control circuit, and an anchoring device.

[0006] CN207300351 U1 describes a self-generating water level monitoring system that includes a power generation mechanism, multiple monitoring transmitters, data processing and communication modules, and uses water, wind and solar energy for power supply.

[0007] CN206919975U1 describes a multifunctional corridor bridge equipped with a hydroelectric generator, a floating box, paddle wheels, guide rods, stabilizing devices, power modules, water level and earthquake sensors, and an alarm circuit to generate power and provide safety warnings.

[0008] Based on this problem, the invention aims to optimize the energy supply and energy consumption of a field device attached to a rainwater overflow basin.

[0009] The task is solved by a system for monitoring the fill level of a container, comprising: - A container for receiving a measuring medium, which has an inlet, an outlet and an overflow outlet, wherein the inlet is designed to convey measuring medium into the container at a variable flow rate, wherein the outlet is designed to convey measuring medium out of the container at a limited flow rate, and wherein the overflow outlet is arranged on the container and designed to convey excess measuring medium out of the container through the overflow outlet if the measuring medium exceeds a predetermined fill level in the container; - A field device designed to determine the fill level of the container; and - A generator, wherein in the event of an overflow the excess measuring medium drives the generator to produce electrical energy and which is designed to supply the field device with electrical energy in the event the generator is driven by the overflowing measuring medium, wherein the field device is designed to be operated in a first and a second operating mode, wherein the field device is designed to be operated in the first operating mode during a period in which the field device is not supplied with electrical energy by the generator and wherein the field device is designed to switch to the second operating mode during a period in which the field device is supplied with electrical energy by the generator.

[0010] The major advantage of the system according to the invention is that it can reliably detect an overflow of a container, such as a rainwater collection basin. In the event of such an overflow, the excess measuring medium drives the generator, which supplies the field device with electrical energy, enabling it to determine the fill level of the measuring medium in the container. This method ensures that the field device is supplied with the electrical energy required for operation in the event of an overflow. Since the field device begins its measuring operation when the generator supplies electrical energy, the occurrence of an overflow can be reliably detected.

[0011] The generator is, for example, an electromechanical generator which is driven by a water wheel.

[0012] Field devices mentioned in connection with the system according to the invention have already been given as examples in the introductory part of the description.

[0013] The first operating mode can be an energy-saving mode in which the measurement operation and / or communication of the field device is deactivated and / or their respective rate is reduced, or a switched-off state of the field device.

[0014] In a preferred embodiment, the system includes a power source configured to supply the field device with electrical energy in the first operating mode. The first operating mode of the field device is designed such that the field device can be supplied by the power source for as long as possible before the power source needs to be recharged or replaced.

[0015] In an advantageous embodiment, the generator is designed to charge the energy source with electrical energy when driven by the excess measuring medium. The generator can be designed such that, in the event of an overflow, it produces a quantity of electrical energy greater than the amount of energy required by the field device for its operation. The excess, or a portion thereof, of electrical energy is then supplied to the energy source, which is charged with this electrical energy.

[0016] According to an advantageous embodiment of the system according to the invention, the first operating mode defines a first measurement rate, and the second operating mode defines a second measurement rate. The field device is configured to set the first or second measurement rate depending on whether the field device is operated in the first or second operating mode and to determine a measured value of the fill level of the measuring medium in the container according to the first or second measurement rate. The higher the measurement rate of the field device is selected, the more electrical energy is required, or the greater the amount of electrical energy required in a given period.

[0017] According to an advantageous embodiment of the system according to the invention, the first measurement rate is zero or greater than zero, and the second measurement rate is greater than the first measurement rate. The electrical energy required in the first operating mode, or the amount of electrical energy required over a period of time, is less than the electrical energy required in the second operating mode, or the amount of electrical energy required over a period of time.

[0018] According to an advantageous embodiment of the system according to the invention, the system comprises a radio unit connected to the field device, wherein the radio unit is part of a wireless communication network. It is provided that a wireless communication network is used as the communication network. In particular, this is based on the WLAN or WiFi standard, the Bluetooth standard, or a mobile communication standard, for example, GSM. Alternatively, any other common wireless standard can be used.

[0019] According to an advantageous embodiment of the system according to the invention, the field device is designed to transmit the currently measured value of the fill level to the radio unit after the measurement has been taken, and the radio unit is designed to transmit the measured value of the fill level to another participant in the communication network via the communication network.

[0020] In a preferred embodiment, the energy source is designed to supply the radio unit with electrical energy in the first operating mode of the field device.

[0021] In an advantageous embodiment, the generator is designed to supply the radio unit with electrical energy in the field device's second operating mode. The generator can be designed such that, in the event of an overflow, it produces an amount of electrical energy greater than the energy required by the field device for its operation and / or the energy required to charge the power source. In this case, the excess, or a portion thereof, of electrical energy is supplied to the radio unit.

[0022] According to an advantageous embodiment of the system according to the invention, the field device or the other participant in the communication network is configured to calculate a measure of the excess measuring medium based on the fill level of the measuring medium determined in the second operating mode. In particular, a quantity for the flow rate, for example a volumetric flow rate, is calculated. The so-called Poleni formula is used for the volumetric flow rate. With this formula, the volumetric flow rate can be determined by the difference between the fill level and the height of the outlet, the so-called weir.

[0023] The invention is explained in more detail with reference to the following figure. It shows Fig. 1: an embodiment of the system according to the invention.

[0024] The diagram shows a container 1 in the form of a stormwater overflow basin. This container has an inlet 13 through which the measuring medium 11, for example rainwater, is fed into the container. The inflow rate of the measuring medium 11 through the inlet 13 is variable over time, and particularly weather-dependent when the container 1 is used as a stormwater overflow basin.

[0025] Furthermore, container 1 has a drain 14 which removes the measuring medium 11 from container 1 at a substantially defined and constant flow rate. This flow rate is limited and, due to the design of the drain, cannot exceed the defined flow rate. The drain 14 can be operated in a controlled manner, i.e., it can be opened and closed as needed.

[0026] The shape of the container 1, in particular the positioning and design of the inlet and outlet 13, 14, is freely selectable and not dependent on the one in Fig.1. The embodiment shown is limited.

[0027] Furthermore, the container 1 includes an overflow outlet 15. This overflow outlet 15, also referred to as a weir, is designed to discharge excess measuring medium 12 from the container 1 after the fill level of the measuring medium 11 in the container has exceeded a predetermined height h.

[0028] A field device 2 is used to detect the current fill level of the measuring medium 11 in the container 1. This device is a level measuring instrument, in particular a non-contact level measuring instrument, e.g., based on the radar principle. Other measuring principles can also be used to detect the fill level.

[0029] In the event of an overflow, the field device 2 can also determine the current quantity, or flow rate, of the excess measuring medium flowing out of the overflow outlet 15. The field device determines the current fill level of the measuring medium, which is above the predetermined height h at which the measuring medium 11 overflows. The difference to the predetermined height h of the overflow outlet 15 is then calculated. The Poleni formula is used for the final calculation of the flow rate of the excess measuring medium 12: Q=23μb2gΔh32

[0030] Q denotes the volume flow rate, b denotes the width of the overflow outlet 15, or the length of the overflow edge. g denotes the acceleration due to gravity at the overflow location, specifically the acceleration due to gravity. Δh denotes the difference between the fill level and the predetermined height h, i.e., the height of the liquid level above the overflow edge of the overflow outlet. µ denotes the so-called overflow coefficient, a dimensionless parameter that depends on the design of the overflow outlet, or rather its overflow edge, and on the overflowing medium. Depending on the design of the overflow outlet, it assumes values ​​between approximately 0.5 and 0.8 for water as the measuring medium.

[0031] The volume V that overflowed between two times t0 and t1 is obtained by integrating the volume flow over the overflow duration: V=∫t0t1Q(t) dt Q(t) denotes the overflow volume flow rate per unit time, V the amount of water flowed over, t the time, and t0, t1 the time points at the beginning and end of the period under consideration. In measurement, the volume flow rate is approximated as the sum of individual measured values: V=∑iQi(ti)Δti

[0032] i denotes the index of the measured values ​​under consideration, Q i (t i ) the volume flow measurement at time t i and Δt i the time interval corresponding to time t i .

[0033] If the fill level of the measuring medium 11 is less than the predetermined height h, meaning no overflow occurs, the field device 2 operates in a first operating mode. In this mode, the field device 2 operates at a low measurement rate—for example, it records one fill level value per hour—or it records no measurements at all. In this first operating mode, the field device 2 is supplied with the electrical energy required for operation by a power source 4. This power source could be, for example, a battery or an alternative rechargeable power source. In this way, the field device 2 requires only a small amount of electrical energy, allowing the power source to supply the field device with electrical energy for an extended period. Since no overflow occurs, it is sufficient to determine the fill level at very long intervals.

[0034] The measured fill level is transmitted via a radio unit 5. Radio unit 5 is part of a wireless communication network and transmits the measured fill level to another participant in the communication network, for example, a radio gateway, which then forwards its data, e.g., to a control system, or directly to a control system or operating unit, such as a laptop or a mobile device like a tablet or smartphone. A wireless communication network is intended to be used. Specifically, this is based on the WLAN / WiFi standard, the Bluetooth standard, or a mobile communication standard, such as GSM. Alternatively, any other common wireless standard can be used. Radio unit 5 is also powered by the power source 4.

[0035] In the event of an overflow, the field device 2 must be operated at a higher measurement rate to reliably determine the current fill level of the measuring medium 11 or the amount of the overflowing medium 12. Since a higher measurement rate increases energy consumption for both the field device 2 and the radio unit 5, the power source can only operate these components for a significantly shorter time than in overflow-free operation.

[0036] For this purpose, a generator 3 is attached to the overflow outlet 15. In this embodiment, the generator is an electromechanical generator driven by a water wheel. The water wheel extends across the entire width of the overflow outlet. In the event of an overflow, the excess measuring medium 12 moves the water wheel, which in turn drives the generator. The electrical energy generated by this drive is supplied to the field device 2 and the radio unit 5. The latter then switches to a second operating mode and records the current fill level of the measuring medium 11 in the container at a higher measurement rate, for example, one measurement every five minutes. The field device 2, or the aforementioned additional network participant, can then determine the amount of overflowing measuring medium 12 from this data.Alternatively, the rotational speed of the water wheel can be determined in order to deduce the flow rate of the measuring medium 12 flowing over it. For this purpose, a separate sensor, such as a light barrier, can be used to determine the rotational speed. Alternatively, the rotational speed can be deduced from the amount of electrical energy currently generated by the generator 3, since the amount of electrical energy generated increases proportionally with increasing rotational speed.

[0037] Generator 3 can be designed such that, in the event of an overflow, it generates an amount of electrical energy greater than the amount of energy required by field device 2 for its operation and / or the amount of energy needed to charge the energy source. In this case, the excess, or a portion thereof, of electrical energy is supplied to energy source 4, which is then charged. Reference symbol list 1 container 11 Measuring medium, in the container 12 excess measuring medium 13 Inflow 14 Procedure 15 Overflow outlet 2 Field device 3 Generator 4 Energy source 5 radio unit h predetermined fill level

Claims

[1] System for monitoring the fill level of a container (1), comprising: - A container (1) for receiving a measuring medium (11), which has an inlet (13), an outlet (14) and an overflow outlet (15), wherein the inlet (13) is designed to convey measuring medium (11) into the container (1) at a variable flow rate, wherein the outlet (14) is designed to convey measuring medium (11) out of the container (1) at a limited flow rate, and wherein the overflow outlet (15) is arranged on the container (1) and is designed to convey excess measuring medium (12) out of the container (1) through the overflow outlet (15) if the measuring medium (11) exceeds a predetermined fill level (h) in the container (1); - A field device (2) designed to determine the fill level of the container (1); and - A generator (3) wherein, in the event of an overflow, the excess measuring medium (12) drives the generator (3) to generate electrical energy and which is designed to supply the field device (2) with electrical energy in the event that the generator (3) is driven by the excess measuring medium (12), characterized by that the field device (2) is designed to operate in a first and a second operating mode, wherein the field device (2) is designed to operate in the first operating mode during a period in which the field device (2) is not supplied with electrical energy by the generator (3), and wherein the field device (2) is designed to switch to the second operating mode during a period in which the field device (2) is supplied with electrical energy by the generator (3). [2] System according to claim 1, wherein the system comprises an energy source (4) which is configured to supply the field device (2) with electrical energy in the first operating mode. [3] System according to at least claim 2, wherein the generator (3) is configured to charge the energy source (4) with electrical energy in the case of a drive by the excess measuring medium (12). [4] System according to at least one of claims 1 to 3, wherein the first operating mode defines a first measurement rate and wherein the second operating mode defines a second measurement rate, wherein the field device (2) is configured to set the first measurement rate or the second measurement rate depending on whether the field device (2) is operated in the first operating mode or in the second operating mode and to determine a measured value of the fill level of the measuring medium (11) in the container (1) according to the first measurement rate or the second measurement rate. [5] System according to claim 4, wherein the first measurement rate is equal to zero or greater than zero and wherein the second measurement rate is greater than the first measurement rate. [6] System according to at least one of claims 1 to 5, wherein the system comprises a radio unit (5) connected to the field device (2), wherein the radio unit (5) is part of a wireless communication network. [7] System according to claims 4 and 6, wherein the field device (2) is configured to transmit the currently measured level to the radio unit (5) after the measurement has been taken, and wherein the radio unit (5) is configured to transmit the measured level to another participant in the communication network via the communication network. [8] System according to at least one of claims 6 or 7, wherein the energy source (4) is configured to supply the radio unit (5) with electrical energy in the first operating mode of the field device (2). [9] System according to at least one of claims 6 to 8, wherein the generator (3) is configured to supply the radio unit (5) with electrical energy in the second operating mode of the field device (2). [10] System according to at least one of claims 4 to 9, wherein the field device (2) or the further participant in the communication network is configured to calculate a measure for the quantity of excess measuring medium (12) on the basis of the fill level of the measuring medium (11) determined in the second operating mode.

Images