Method for Monitoring the Energy Content of a Water Storage Tank System

Abstract

A method of controlling a heat up of a hot water tank, comprising a tank, which contains water and receives incoming cold-water at a cold-water inlet and outputs heated water through a heated water outlet, the method comprising: heating the water in the tank depending on a thermal energy content calculated as a function of an actual incoming cold-water temperature measured by a cold-water temperature sensor, when a tapping event is identified. A water tank heating device and a controller system for controlling a heat up of a hot water tank depending on a thermal energy content calculated as a function of an actual incoming cold-water temperature.

Claims

1. A method of determining a thermal energy content of a hot water tank device, the hot water tank device comprising a tank, a cold-water inlet, a heated water outlet, a cold-water temperature sensor, a heating device and a controller component, the tank containing water, wherein the tank receives incoming cold-water at the cold-water inlet and outputs heated water through the heated water outlet when a tapping event occurs, the heated water outlet being located in an upper portion of the tank and the cold-water inlet being located in a lower portion of the tank with the heating device being thermally coupled to water in between the cold-water inlet and the heated water outlet, the cold-water temperature sensor being arranged in the lower portion of the tank configured to determine a temperature of the water in vicinity of the cold-water inlet, wherein the water within the tank is heated by operation of the heating device thermally coupled to the water, the operation of the heating device is controlled by said controller component, the method comprising: measuring, using the cold-water temperature sensor, successive incoming cold-water temperatures in successive cold-water temperature measurements measured in a defined measuring rate, detecting, by said controller component, a beginning of a tapping event when a difference of two successive incoming cold-water temperatures of two successive cold-water temperature measurements exceeds a predetermined first temperature difference threshold, measuring, using the cold-water temperature sensor, successive incoming water temperatures during an adequate time period after the beginning of said tapping event, deriving, using the controller component, the actual incoming water temperature as an average of the incoming water temperatures measured during said adequate time period, determining, using the controller component, the thermal energy content of the hot water tank device as a function of said derived actual incoming cold-water temperature.

2. The method according to claim 1, wherein said adequate time period starts when a difference of two successive incoming cold-water temperatures of two successive cold-water temperature measurements is below a second temperature difference threshold.

3. The method according to claim 1, wherein said adequate time period ends after a predetermined period of time has elapsed or at or after an end of said tapping event.

4. The method according to claim 1, wherein the step of measuring successive incoming cold-water temperatures in successive cold-water temperature measurements with said cold-water temperature sensor during said adequate time period comprises storing said successive cold-water temperatures in a storing unit of the controller component.

5. The method according to claim 1, further comprising: determining, by said control unit, a validity of subsequent incoming water temperature measurements during said adequate time period, wherein said subsequent cold-water temperature measurements are valid if a temperature difference between the two subsequent cold-water temperature measurements is lower than a third temperature difference threshold.

6. The method according to claim 1, the hot water tank device further comprising a second temperature sensor mounted to said tank, the method further comprising: measuring a tank temperature using the second temperature sensor, which is related to a thermal energy content, and output a tank temperature signal representative of said tank temperature with a tank temperature sensor mounted to said tank.

7. The method according to claim 1, further comprising a step of transmitting, using a ripple control transmitter device in signal communication with the controller component, an energy content signal indicative of the determined thermal energy content.

8. The method according to claim 7, further comprising a step of receiving, using a ripple control tuner in signal communication with the controller component, a signal for activating the heating device in response to the energy content signal.

9. A hot water tank device, the hot water tank device comprising a tank, a cold-water inlet, a heated water outlet, a cold-water temperature sensor, a heating device and a controller component, the tank containing water, wherein the tank receives incoming cold-water at the cold-water inlet and outputs heated water through the heated water outlet when a tapping event occurs, the heated water outlet being located in an upper portion of the tank and the cold-water inlet being located in a lower portion of the tank with the heating device being thermally coupled to water in between the cold-water inlet and the heated water outlet, the cold-water temperature sensor being arranged in the lower portion of the tank configured to determine a temperature of the water in vicinity of the cold-water inlet, wherein the water within the tank is heated by operation of the heating device thermally coupled to the water, the operation of the heating device is controlled by said controller component, the cold-water temperature sensor being configured to successively measure incoming cold-water temperatures in successive cold-water temperature measurements in a defined measuring rate, the controller component being configured to determine a beginning of a tapping event when a difference of two successive incoming cold-water temperatures of two successive cold-water temperature measurements exceeds a predetermined first temperature difference threshold, the cold-water temperature sensor being further configured to successively measure incoming water temperatures during an adequate time period after the beginning of said tapping event, the controller component being configured to derive the actual incoming water temperature as an average of the incoming water temperatures measured during said adequate time period, and the controller component being configured to determine the thermal energy content of the hot water tank device as a function of said derived actual incoming cold-water temperature.

10. A controller system for controlling a heat up of a hot water tank, comprising a cold-water temperature sensor configured to be attached at a place of a tank, which contains water and comprises a water inlet configured for receiving incoming cold-water and a water outlet configured for allowing water heated to exit, wherein said cold-water temperature sensor is configured to measure an actual incoming cold-water temperature and to output an actual cold-water temperature signal representative of said actual incoming cold-water temperature and a control unit comprising microprocessor software integrated in an electronic device, wherein said control unit is configured to receive said actual cold-water temperature signal transmitted by said cold-water temperature senor, wherein said control unit is configured to identify a tapping event and to control a heating device when said tapping event is identified in order to heat water in the tank depending on a thermal energy content calculated as a function of an actual incoming cold-water temperature measured by said cold-water temperature sensor.

11. A method of controlling a heat up of a hot water tank having a control unit with a receiver interface circuit, a control circuit arrangement and a transmitter interface circuit, the method comprising the steps of: measuring a first tank temperature of said hot water tank with a temperature sensor mounted to said hot water tank; receiving, by said receiver interface circuit, a first tank temperature signal generated and transmitted by said temperature sensor, which represents said first tank temperature; generating, by said control circuit arrangement, an activation signal to activate a heating device, when said control circuit arrangement calls for heat; feeding an actual incoming cold-water temperature signal into said control circuit arrangement, wherein said actual incoming cold-water temperature signal represents an actual incoming cold-water temperature of cold-water, which flows into said hot water tank; generating, by said control circuit arrangement, a parameter based on said actual incoming cold-water temperature signal; measuring a second tank temperature of said hot water tank with said temperature sensor after said incoming cold-water flowed into said hot water tank, wherein said second tank temperature is related to a thermal energy content of said hot water tank; receiving, by said receiver interface circuit, a second tank temperature signal generated and transmitted by said temperature sensor, which represents said second tank temperature; modifying, by said control circuit arrangement, said parameter based on said second tank temperature signal; performing, by said control circuit arrangement, a comparison of a set point value with said parameter, which is modified based on said second tank temperature signal; processing, by said control circuit arrangement, said activation signal depending on said comparison; and transmitting, by said transmitter interface circuit to a receiver interface circuit of a heating device, said activation signal, which is processed depending on said comparison.

12. The method according to claim 11, further comprising: calculating, by said control circuit arrangement, an exact value of said thermal energy content as a function of a reference mass and said parameter, which is modified based on said second tank temperature signal, wherein the step of generating, by said control circuit arrangement, said activation signal depends on at least one of a) whether said exact value is lower than said set point value and b) on an amount of said exact value, wherein said control circuit arrangement generates said activation signal when said exact value is lower than the set point value.

13. The method according to claim 11, wherein the step of generating, by said control circuit arrangement, said activation signal depends on whether said amount of said exact value is lower than a specified value of thermal energy content, wherein said control circuit arrangement generates said activation signal when said amount of said exact value is less than a specified value of thermal energy content.

14. The method according to claim 11, further comprising: calculating, by said control circuit arrangement, an exact value of said thermal energy content by multiplying a reference mass parameter by a temperature rise value, wherein said temperature rise value is a difference between said set point value and said incoming cold-water temperature, wherein the step of generating, by said control circuit arrangement, said activation signal depends on said exact value.

15. The method according to claim 11, further comprising: comparing, by said control circuit arrangement, said actual incoming cold-water temperature represented by said actual cold-water signal fed into said control circuit arrangement with a previous stored water temperature represented by a previous stored water temperature signal, which is stored in a storage circuit of said control circuit arrangement; updating, by said control circuit arrangement, said previous stored water temperature signal, if said actual incoming cold-water temperature differs from said previous stored water temperature; and utilizing said stored water temperature signal, which is updated, for the step of generating, by said control circuit arrangement, said parameter, wherein the step of updating, by said control circuit arrangement, said previous stored water temperature signal, depends on whether said actual incoming cold-water temperature is lower than said stored water temperature, wherein said control circuit arrangement updates said previous stored water temperature signal if said actual incoming cold-water temperature is lower than said previous stored water temperature.

16. The method according to claim 11, wherein the step of feeding said incoming cold-water temperature signal into said control circuit arrangement, comprises the steps: measuring said actual incoming cold-water temperature with a cold-water temperature sensor located in said hot water tank close to a water inlet; and receiving, by said receiver interface circuit, said actual incoming cold-water temperature signal generated and transmitted by said cold water temperature sensor, which represents said actual incoming cold-water temperature.

17. The method according to claim 11, further comprising: comparing a last measured incoming cold-water temperature with a previously measured incoming cold-water temperature to calculate a difference; and activating a second timer, which initiates detecting said actual incoming cold-water temperature or successive incoming cold-water temperatures with a time base, when said difference is lower than a first defined difference value, after said second timer is started, detecting successive incoming cold-water temperatures periodically for a minimum duration of more than 10 seconds and putting each incoming cold-water temperature in a register; performing, by said control circuit arrangement, a comparison of said successive incoming cold-water temperatures putted in said register; determining, by said control circuit arrangement, a validity of said successive cold-water temperature measurements depending on a difference resulting from said comparison, wherein said successive cold-water temperature measurements are valid if said difference is lower than a second defined difference value; averaging, by said control circuit arrangement, the successive incoming cold-water temperatures putted in said register to obtain an averaged incoming cold-water temperature; comparing, by said control circuit arrangement, said averaged incoming cold-water temperature with a previous stored averaged water temperature represented by a previous stored averaged water temperature signal, which is stored in a storage circuit of said control circuit arrangement; and updating, by said control circuit arrangement, said previous stored averaged water temperature signal, if a difference between said averaged incoming cold-water temperature and said previous stored averaged water temperature is more than 2 C., wherein the step of updating, by said control circuit arrangement, said previous stored water temperature signal comprising a simple moving averaging process.

18. The method according to the claim 11, further comprising: providing energy needs of at least one hot water tank to an energy supplier or transmitting energy needs of at least one hot water tank to a utility company.

19. The method according to claim 11, wherein a utility company sorting consumers into different energy demand classes in order to stabilize a voltage to keep said voltage constant, a frequency to keep said frequency constant, or both, of an electric grid.

20. The method according to claim 19, wherein the heating device comprises a receiver interface circuit to receive a remote control command, which is generated and transmitted by a utility company, wherein the method comprises the step of receiving, by said receiver interface circuit of the heating device, said remote control command generated and transmitted by said utility company.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0135] FIG. 1 shows a relative inaccuracy of a mix water amount at different incoming cold-water temperatures.

[0136] FIG. 2 shows the average ground water temperature in the US by location.

[0137] FIG. 3 shows a water storage system.

[0138] FIG. 4 shows a water storage system with a tilted heating device.

[0139] FIG. 5 shows a water storage system with a flow sensor.

[0140] FIG. 6 shows a result of a feedback of different water heater devices.

DETAILED DESCRIPTION OF EMBODIMENTS

[0141] It is to be understood that the figures and descriptions have been simplified to illustrate elements that are relevant for a clear understanding of the present disclosure, while eliminating, for purposes of clarity, many other elements, which are conventional in this art. Those of ordinary skill in the art will recognize that other elements are desirable for implementing the present disclosure. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present disclosure, a discussion of such elements is not provided herein.

[0142] The present disclosure will now be described in detail on the basis of exemplary embodiments.

[0143] For example, in the US there is a variation of the annual average incoming water temperature by location of 40 F. as illustrated in FIG. 2. A calculation shows in case of 15 C. incoming water temperature and a full loaded tank the customer gets 280 l mixed water out of the tank. If the incoming cold-water temperature changes from 15 C. to 10 C. the amount of hot water produced with the same tank is 30 l less than the indicated value. For an accurate energy monitoring device, it is important to take a variation of incoming cold-water temperature into account or more if units are installed in a location where the temperature of the incoming cold-water temperature differs from the estimated value. In the above example, the water volume in the tank is 100 l and a set point for the water temperature in the tank is 85 C. In the context of the present disclosure, a full loaded tank or full tank is a tank for which the water temperature is heated to the expected hot water temperature, i.e. the set point of 85 C. in the above example.

[0144] The following graph FIG. 1 shows the inaccuracy of the indicated mix water amount if an estimated incoming cold-water temperature of 15 C. is considered. The example is basing on a 300-l tank with an integral sensor and 60 C. hot water temperature setting.

[0145] Referring to FIG. 1 the following is cited as an example. If the incoming water temperature is 15 C., the deviation of the displayed mixed water amount is 0.

[0146] If the tank has a load status of 0.5, that means the tank is half empty, the effective available amount of usable hot water is 20% less for 8 C. cold-water and 14% less for 10 C. incoming cold-water in comparison to the displayed amount.

[0147] If the incoming cold-water temperature is 25 C. and the tank is 50% empty, the displayed amount of mixed water is 28% less than the amount, which is actually available.

[0148] The energy monitoring system has a higher accuracy under consideration of alternating seasonal incoming cold-water temperatures, and a standard energy monitoring device is offered for different locations from northern to southern climates. The higher accuracy is established if the incoming cold-water temperature is measured using a temperature sensor which needs to be located close to the incoming cold-water inlet tube.

[0149] The embodiment describes a system, which controls the energy content of a water tank using an integral sensor, and an additional sensor located close to the incoming cold-water tube. Preferably, the additional sensor is a cold-water temperature sensor.

[0150] FIG. 3 shows schematically and exemplarily a hot water tank device, which is also referred to as a water storage system. The hot water tank device comprises a tank 1 with a hot water outlet pipe 2, an incoming cold-water inlet pipe 3, a heating device 4, an electronic device 5, a display 6 and an actuator panel 7. There is optionally a flow sensor 106 provided to measure the flow of water into the tank 1.

[0151] With this flow sensor 106 the exchange of water in the tank is measured depending on the amount of tapped water in a time period that could affect the set point temperature.

[0152] Display 6 and actuator panel 7 can be implemented as actual physical devices, for instance on the outside of the hot water tank device. Just as an example, display 6 and actuator panel 7 can comprise a touch sensitive LCD screen to integrate the functions of displaying and adjusting the device, while also all other display and actuation alternatives known in the art can be used.

[0153] Alternatively or additionally, display 6 and actuator panel 7 can be implemented remotely, for instance using a downloadable App which communicates wirelessly with electronic device 5.

[0154] There are several temperature sensors 8, 9, 10 mounted to the tank 1. The temperature sensor 8 situated close to the pipe where the hot water leaves the tank, an integral temperature sensor 9, which is mounted in a vertical direction of the tank 1 in order to create a thermocouple chain of a multiple sensor elements, and a bottom temperature sensor 10 situated close to the bottom incoming cold-water port. The electronic device 5 is connected to the heating device 4 to bring the heating device 4 into operation if the water needs to be heated. In this embodiment, the heating device is an electric heating element. In another case, it could additionally or alternatively be a heat exchanger of a heat pump or the tank 1 is connected to a heat pump or refrigerant circuit. The tank 1 preferably comprises or consists of steel, wherein also other materials are contemplated.

[0155] A safety cut-out is required to shut the heating device 4 down in case of a failed electronic control 5 or temperature sensor 8, 9, 10 failures. The safety cut-out is not shown in FIG. 3. All temperature sensors 8, 9, 10 may be mounted on the tank surface using a tape or using welded sensor sleeves which are in contact with water on well-placed spots.

[0156] The electronic device 5 in one embodiment comprises a microcontroller, which controls the amount of usable hot water in the tank 1 by controlling heating device 4. The amount of usable hot water in the tank 1 is determined using the equation [0]. The temperature difference between a temperature measured by temperature sensor 8 and a temperature set point is calculated. The temperature set point is adjustable on the actuator panel 7, for instance. The energy content of the tank 1 is recorded in energy units [KWh] and the temperature difference is determined between a measured temperature and the temperature setting. Electronic device 5 is configured to store a parameter indicating the incoming cold-water temperature. The incoming cold-water temperature is crucial for determining the amount of usable hot water in the tank 1 and also to determine the load status of the tank.

[0157] The thermal conductivity of the steel tank 1 surface and the thermal conductivity of the water transfer heat from the heated top section 101 above the heating device 4 to the cold bottom section 102 of the tank 1, such that also a cold sump 103 is heated. This creates an inaccurate measurement result of the incoming water temperature if the temperature determined by temperature sensor 10 is considered the cold-water temperature. Also, depending on the incoming cold-water pipe 3 section between the water storage tank 1 and an entrance of a pipe into a building where the water tank 1 is installed more or less heat gets transferred from the ambient conditions to the cold-water, which warms up the water in a tube section 104, cf. FIG. 4.

[0158] The actual incoming cold-water temperature needs to be detected with the following steps which are integrated in the microprocessor software as part of the electronic device 5 including an electronic main board.

[0159] 1. Identify a tapping event with an adequate time period in order to detect the actual cold-water temperature by comparison of successive cold-water temperature values using the temperature information of sensor 10 and a time base of 5 seconds.

[0160] 2. Tapping begin is detected if the difference of two successive cold-water temperature values determined by temperature sensor 10 is more than a defined first temperature difference threshold, for example 2 K. Start a first timer 20 when tapping begin is detected.

[0161] 3. Timer 20 compares the successive measured cold-water temperature values periodically, for instance with a time base of 2 seconds. If the difference of two successive measured temperature values is less than a second temperature difference threshold, for example less than 1 K, start a second timer 21.

[0162] 4. Timer 21 detects the incoming cold-water temperature periodically, for instance every 2 seconds, for a time period exceeding a minimum duration, for example a time period of more than 10 seconds, and puts each single following temperature value in a register. The storing in a register is disclosed as one example Timer 21 and 20 are running in parallel and if the comparison of successive measured values shows a difference exceeding a third temperature difference threshold, which can for instance be equal to the first temperature difference threshold such as more than 2 K, both timers are stopped and the measurement is considered not valid. This would correspond to a situation in which the temperature drop, which fell below the second temperature difference threshold, would rise again, in other words, the water temperature would again significantly drop, contrary to what is expected as a true or actual incoming cold water temperature.

[0163] 5. If the measurement is considered valid, i.e. if the conditions for considering the measurement not valid in step 4 above do not apply, averaging the cold-water temperature values takes place by electronic device 5. It should be emphasized that any implementation of such averaging process as known in the art is contemplated.

[0164] 6. Compare the current averaged cold-water temperature with the former stored averaged value.

[0165] 7. If the difference of the actual calculated value compared to the former stored value is more than 2 K overwrite the former stored value using simple moving averaging process.

[0166] 8. For initial start, a factory temperature value of 15 C. cold-water temperature is stored.

[0167] The remaining energy content Q.sub.energy in the tank is calculated using the following law or equation [2]:

Q.sub.energy=M.sub.mcw*CP.sub.Water*(T.sub.mwT.sub.cw)Equation [2]: [0168] M.sub.m cw amount of mixed water based on cold-water temperature [0169] T.sub.mw mix water temperature [0170] CP.sub.water specific heat capacity of water [0171] T.sub.cw temperature incoming cold-water

[0172] The energy content of the tank Q.sub.energy set point is the energy content if the thermostat of the tank is satisfied. It is calculated with the following equation [3]:

[00002]$\begin{array}{cc}{Q}_{\mathrm{energyset}}=M_{m.Math..Math.\mathrm{setpoint}}*C.Math.P_{\mathrm{Water}}*\left(T_{\mathrm{mw}}-T_{\mathrm{cw}}\right)& \mathrm{Equation}.Math.\left[3\right]\end{array}$ [0173] M.sub.m setpoint amount of mixed water based on cold-water temperature and setpoint temperature [0174] T.sub.mw mix water temperature [0175] CP.sub.water specific heat capacity of water [0176] T.sub.cw temperature incoming cold-water

[0177] The amount of energy Q.sub.energy reload needed to be recharged is calculatedequation [4]:

Q.sub.energy reloaded=Q.sub.energy setpoint*Q.sub.energyEquation [4]:

[0178] The value of Q.sub.energy reload is permanently calculated in the software of the electronic device 5.

[0179] The energy content information of the water tank is transmitted from the electronic device 5 over line 13 to a ripple control transmitter device 14, which can be connected to a structure like the internet.

[0180] For remote control, the ripple control tuner 12 is connected via line 11 to the electronic device 5. Both devices 12 and 14 may be integrated with the electronic device 5. It is an advantage to deliver the energy content signal in form of a pulse pattern in a frequency range between 110 Hz-2000 Hz.

[0181] This is an advantage because it is of interest to a grid owner to sort consumers into different energy demand classes in order to be able to stabilize the voltage of the grid structure by remote control.

[0182] FIG. 6 shows the result of feedback of different water heater devices connected with a ripple control system. Due to the loading information of each single water tank 1 system, the units get categorized in terms of their individual loading demand. For example, the number of vertical lines in category [A] represent the number of consumers who needor are capable of receivinga loading capacity of less than 2.5 KWh each. Those units are transmitting their loading demand via their ripple control transmitter a 110 Hz signal to the grid owner. Categories [B], [C] and [D] are categories for other loading capacity needs.

[0183] A tank 1 volume is also calculated.

[0184] A varied incoming cold-water flow is measured with a sensor.

[0185] An incoming cold-water temperature is a value, which is corresponding to the actual water temperature of the cold-water source. This value could be determined by measuring the cold-water temperature by the water utility in a water treatment facility or in a main feed line of the utility. This value is transmitted to the control unit where the energy content of the water tank is calculated. Otherwise, it is an embodiment, that the cold-water temperature is measured in a water line of the building where the water tank is located or in or at the water tank.

[0186] An embodiment of the sensor 10 is an at least single sensor element in close distance to a water inlet 104. It could be mounted inside the cold sump 103 or at the bottom of the tank 1, at the water inlet 105, outside or inside, or in the area of the tube section 104. In a special case where the incoming cold waterpipe 3 is situated through the top section 101 of the tank 1, the sensor could be applied in the area of the incoming cold-water pipe 3 or other water inlet.

[0187] An embodiment of the integral sensor 9 is a chain of thermocouples especially in line, vertically mounted, a wound wire with a defined length consisting of material with NTC or PTC characteristics, a layer with a printed sensor or a multiple printed sensor chain or at least a couple of sensors in a series or parallel circuit. The integral sensor is located inside or outside the tank 1.

[0188] Data acquisition is realized by wire or wireless communication between the temperature sensor 8, 9, 10 and the electronic device 5 or other control unit.

[0189] The temperature sensor 10 should be installed at a place of the actual cold-water temperature. This place is in another embodiment one or more representative locations where the temperature sensors 10 are located. If the temperature sensors 8, 9, 10 are mounted outside of the water tank 1 at a main water pipe or a house water pipe, it is an advantage when the temperature sensors 8, 9, 10 are connected to a wireless communication transmitter to send the measured incoming cold-water temperature to the control unit.

[0190] A further embodiment is to receive local cold-water temperature values from a utility or other source and actually store them in the electronic device 5 and to use them as cold-water temperatures instead of or in addition to a measured temperature value from the cold-water incoming sensor 10. Otherwise, a cold-water temperature value can be entered to the electronic device 5 by the user manually or via verbal command.

[0191] It is possible to retrofit existing water heating systems with this method.

[0192] While this disclosure has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure as defined in the following claims.

[0193] It is noted that citation or identification of any document in this application is not an admission that such document is available as prior art to the present disclosure.