Temperature estimation for a water heater system

Abstract

A water heater system includes a tank storing water, a first sensor operably coupled with an upper portion of the tank and that communicates a first signal, a second sensor operably coupled with a lower portion of the tank and that communicates a second signal, and control circuitry configured to determine a first temperature of water in the upper portion based on the first signal, determine a second temperature of water in the lower portion based on the second signal, determine functional weights for the first temperature and the second temperature based on a difference between a target temperature for the water and the second temperature, calculate a weighted average of the first temperature and the second temperature based on the functional weights, determine a representative temperature of the water based on the weighted average, and communicate an output in response to the representative temperature.

Description

FIELD OF THE DISCLOSURE

[0001] The present disclosure generally relates to temperature estimation for water heater systems, more particularly, to control systems and methods for determining the heat capacity of a water tank of a water heater system.SUMMARY OF THE DISCLOSURE

[0002] According to a first aspect of the present disclosure, a water heater system includes a tank storing water, a first sensor operably coupled with an upper portion of the tank and that communicates a first signal, a second sensor operably coupled with a lower portion of the tank and that communicates a second signal, and control circuitry configured to determine a first temperature of water in the upper portion of the tank based on the first signal, determine a second temperature of water in the lower portion of the tank based on the second signal, determine functional weights for the first temperature and the second temperature based on a difference between a target temperature for the water and the second temperature, calculate a weighted average of the first temperature and the second temperature based on the functional weights, determine a representative temperature of the water based on the weighted average, and communicate an output in response to the representative temperature.

[0003] Embodiments of the first aspect of the present disclosure can include any one or any combination of the following features:

[0004] the control circuitry is configured to determine a heat capacity of the tank based on the representative temperature;

[0005] the control circuitry is configured to determine the functional weights via a linear function of the difference;

[0006] a heating system configured to heat the water, wherein the control circuitry is configured to determine operation of the heating system, and determine the functional weights based on the operation of the heating system; and

[0007] the heating system includes a compressor, wherein the control circuitry is configured to adjust the functional weights while the compressor is activated.

[0008] According to a second aspect of the present disclosure, a water heater system including a tank storing water, a first sensor operably coupled with an upper portion of the tank and that communicates a first signal, a second sensor operably coupled with a lower portion of the tank and that communicates a second signal, and control circuitry configured to determine a first temperature of water in the upper portion of the tank based on the first signal, determine a second temperature of water in the lower portion of the tank based on the second signal, control functional weights for each of the first temperature and the second temperature, calculate a weighted average of the first temperature and the second temperature based on the functional weights, and determine a representative temperature of the water based on the weighted average

[0009] Embodiments of the second aspect of the present disclosure can include any one or any combination of the following features:

[0010] the representative temperature is an estimate of a mean temperature of the water;

[0011] the functional weights are determined based on a difference between the second temperature and a target temperature for the water;

[0012] the control circuitry is configured to determine the functional weights as a function of the difference;

[0013] the function is a linear function between a lower difference threshold and an upper difference threshold;

[0014] calculating the weighted average includes summing of a first product of a first functional weight and the first temperature and a second product of a second functional weight and the second temperature;

[0015] the first functional weight is a first percentage and the second functional weight is a whole less the first percentage;

[0016] the control circuitry is configured to determine a heat capacity of the tank based on the representative temperature;

[0017] a heating system configured to heat the water, wherein the control circuitry is configured to determine operation of the heating system, and determine the functional weights based on operation of the heating system;

[0018] the heating system includes a heat pump, wherein the control circuitry is configured to adjust the functional weights during the operation of the heat pump;

[0019] the heat pump includes a compressor, wherein the control circuitry is configured to adjust the weighted average while the compressor is activated; and

[0020] at least one of the first sensor and the second sensor includes a temperature sensor.

[0021] According to a third aspect of the present disclosure, a method for operating a water heater system that heats water. The method includes determining a first temperature of water in an upper portion of a tank of the water heater, determining a second temperature of water in a lower portion of the tank, determining functional weights for the first temperature and the second temperature based on a difference between a target temperature for the water and the second temperature, calculating a weighted average of the first temperature and the second temperature based on the functional weights, determining a representative temperature of the water based on the weighted average, and communicating an output in response to the representative temperature.

[0022] Embodiments of the third aspect of the present disclosure can include any one or any combination of the following features:

[0023] determining a heat capacity of the tank based on the representative temperature;

[0024] determining operation of a heat pump of the water heater system; and determining the functional weights based on the operation of the heat pump.

[0025] These and other features, advantages, and objects of the present disclosure will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.BRIEF DESCRIPTION OF THE DRAWINGSIn the drawings:

[0026] FIG. 1 is a functional diagram of a water heater system;

[0027] FIG. 2 is a listing of equations for calculation of a representative temperature of water in a tank of a water heater system;

[0028] FIG. 3 is a pair of graphs demonstrating a representative temperature for a water heater system determined by control of the relative weights of measured temperatures;

[0029] FIG. 4 is graph demonstrating different functions of functional weights for measured temperatures based on heating system operation; and

[0030] FIG. 5 is a flow diagram of a method for operating a water heater system.

[0031] The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles described herein.DETAILED DESCRIPTION

[0032] As used herein, the term “and / or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0033] As used herein, the term “coupled” (in all of its forms: couple, coupling, coupled, etc.) generally means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and / or any additional intermediate members. Such joining may include members being integrally formed as a single unitary body with one another (i.e., integrally coupled) or may refer to joining of two components. Such joining may be permanent in nature or may be removable or releasable in nature, unless otherwise stated.

[0034] As used herein, the terms “the,”“a,” or “an,” mean “at least one,” and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to “a component” includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0035] Referring generally to FIGS. 1-5, reference numeral 10 generally designates a water heater system. The water heater system 10 includes control circuitry 12 that controls heating systems to heat a tank 14 of the water heater system 10. For example, the water heater system 10 can include a water heater that utilizes electrical and / or refrigerant-based heating. A heat pump 16 and / or one or more resistance heating elements 18a, 18b can therefore be provided for warming water in the tank 14 of the water heater. The control circuitry 12 can utilize sensors 20a, 20b, 22, 24, 26, 28 to control the water heater system 10 to heat the water. For example, measured temperatures at points on the heat pump 16 and / or the tank 14 (e.g., the upper portion 30 and the lower portion 32) can be read by the control circuitry 12 and compared to target temperatures. The control circuitry 12 can control one or more components of the heat pump 16 based on the estimates to warm water in one or both of an upper portion 30 of the tank 14 and a lower portion 32 of the tank 14. For example, the control circuitry 12 can control at least one of a compressor 36, a condenser 38, an expansion device 40, an evaporator 42 that transfers heat to the tank 14, and a fan 44 that is controlled to draw air over the evaporator 42 to draw heat from the air to the heat pump 16. In general, the water heater system 10 can employ an estimation algorithm that determines a representative temperature TREP that may be indicative of an average temperature for the water in the tank 14, such that a product of a volume of the water in the tank 14 multiplied by the representative temperature TREP can represent a heat capacity of the tank 14. The heat capacity can be communicated to other sources, such as energy management utilities and / or can be used for control of the water heater system 10.

[0036] With continued reference to FIGS. 1-5, a water heater system 10 includes a tank 14 storing water, a first sensor 20a operably coupled with an upper portion 30 of the tank 14 and that communicates a first signal, a second sensor 20b operably coupled with a lower portion 32 of the tank 14 and that communicates a second signal, and control circuitry 12 configured to determine a first temperature of water in the upper portion 30 based on the first signal, determine a second temperature of water in the lower portion 32 based on the second signal, determine functional weights for the first temperature and the second temperature based on a difference ΔT between a target temperature for the water and the second temperature, calculate a weighted average of the first temperature and the second temperature based on the functional weights, determine a representative temperature TREP of the water based on the weighted average, and communicate an output in response to the representative temperature TREP.

[0037] The water heater system 10 can utilize the representative temperature TREP to determine various qualities about the water heater system 10, such as heat capacity. In some examples, the representative temperature TREP is indicative of an actual mean temperature of water in the tank 14, where a non-weighted average TAVG of an upper temperature T U (e.g., temperature at the upper portion 30) and a lower temperature TL (e.g., temperature at the lower portion 32) would be less than or greater than the representative temperature TREP of water in the tank 14. For example, stratification, non-linear distribution of heat in the tank 14, or dynamic operation of the water heater system 10 (e.g., warmed water actively being drawn from the tank 14) can result in non-linear distributions.

[0038] Referring now to FIG. 1, one or more resistance heating elements 18a, 18b can include a first resistance heating element 18a adjacent an upper portion 30 of the tank 14 and a second heating element 18b adjacent a lower portion 32 of the tank 14. The upper portion 30 can be near a top of the tank 14 and the lower portion 32 can be near a bottom of the tank 14. For example, the first sensor 20a can measure a temperature of the water in a top 10%, by height or volume, of the tank 14, and the second sensor 20b can measure a temperature of the water in a bottom 10%, by height or volume, of the tank 14. In some examples, the upper temperature is measured within the top 20% of the tank 14, and the lower temperature is measured within bottom 20% of the tank 14. In general, the vertical displacement of the first sensor 20a relative to the second sensor 20b is greater than a vertical displacement of the bottom of the tank 14 and the second sensor 20b and / pr a vertical displacement of the top of the tank 14 and the first sensor 20a. The first sensor 20a can be positioned on the tank 14 at a first height, and the second sensor 20b can be positioned at a second height of the tank 14. The upper element 18a can be positioned at the first height, and the lower element 18b can be positioned at the second height. In general, temperature of the upper portion 30 and the temperature of the lower portion 32 can be determined by the control circuitry 12 using the signals from the first sensor 20a and the second sensor 20b, respectively.

[0039] Each resistance heating element 18a, 18b can be configured to heat water in the tank 14 and is mounted thereto. In the present example, the resistance heating elements 18a, 18b extend into the tank 14, though it is contemplated that the resistance heating elements 18a, 18b may operably couple to an outer surface 34 of the tank 14 to indirectly heat water in the tank 14 by heating a wall of the tank 14. The resistance heating elements 18a, 18b can be electrical elements that generate heat when an electrical current passes through the element due to the resistive components of the resistance heating elements 18a, 18b. For example, the resistance heating elements 18a, 18b can be composed of metallic alloys, ceramic materials, or ceramic metals that are configured to generate heat in response to electrical current.

[0040] The heat pump 16 includes a compressor 36, a first heat exchanger 38 (e.g., a condenser), an expansion device 40 downstream of the first heat exchanger 38, and a second heat exchanger 42 (e.g., evaporator) downstream of the expansion device 40. The heat pump 16 can be configured to circulate refrigerant to heat the tank 14 and the water therein. For example, in operation, refrigerant is cycled through a closed-loop system to transfer heat. The cycle begins at the expansion device 40 (e.g., expansion valve), where high-pressure liquid refrigerant is throttled to a low-pressure, low-temperature state. This cooler refrigerant then enters the evaporator 42, where it absorbs heat from the surrounding environment via air drawn over the evaporator 42 by a fan 44. As the refrigerant absorbs this heat, it evaporates into a low-pressure vapor. The vaporized refrigerant is then drawn into the compressor 36, which increases its pressure and temperature. The high-pressure, high-temperature vapor exits the compressor 36 and flows into the condenser 38, where it releases the absorbed heat to the tank 14. As the refrigerant releases heat, it condenses back into a high-pressure liquid. This liquid then flows back to the expansion device 40, completing the cycle and allowing the process to repeat. By continuously cycling refrigerant through these components, the heat pump 16 effectively moves heat from one location (air) to another (the tank 14).

[0041] The control circuitry 12 can be configured to operate the heat pump 16 and one or more of the resistance heating elements 18a, 18b to warm the water in the tank 14 in response to temperatures of the water in the tank 14 being below target thresholds. For example, the control circuitry 12 can determine the upper temperature T U, compare the upper temperature T U to a target temperature (e.g., a setpoint temperature TSP), and, if the upper temperature T U is below the setpoint temperature TSP or below the setpoint temperature TSP by a threshold amount, control the heat pump 16 and / or the resistance heating elements 18a, 18b to heat the tank 14. In some examples, the representative temperature TREP can be used for control of the heating system (e.g., the heat pump 16 and / or the resistance heating elements 18a, 18b).

[0042] The control circuitry 12 is configured to control components of the heat pump 16 based on temperatures of the refrigerant and / or air as measured via sensors 22-28 positioned at various points of the heat pump 16, including in ambient air. For example, a third sensor 24 can be operably coupled to an entry of the evaporator 42 and a fourth sensor 24 can be operably coupled to an exit of the evaporator 42. A fifth sensor 26 can be operably coupled to an outlet of the compressor 36. For example, the fifth sensor 26 can be coupled to the heat pump 16 upstream of the condenser 38. In some examples, the fifth sensor 26 can be positioned at a narrow portion of a discharge portion of the compressor 36 and upstream of a wide portion of tubing that interposes the narrow portion and the condenser 38, as shown in FIG. 1. A sixth sensor 28 can be provided for measuring the temperature of air ambient to the water heater system 10, such that the control circuitry 12 can read an ambient temperature and control the water heater system 10 based on the ambient temperature.

[0043] The sensors 20a, 20b, 22, 24, 26, 28 can be temperature sensors. In some examples, one or more of the sensors 20a, 20b, 22, 24, 26, 28 include flow sensors, pressure sensors, or any other sensor that can communicate signals that allow the control circuitry 12 to determine temperatures at the locations of the sensors 20a, 20b, 22, 24, 26, 28. For example, the control circuitry 12 can determine the lower temperature T L via signals from the second sensor 20b and can determine the upper temperature T U via signals from the second sensor 20a.

[0044] With respect to the heat pump 16, the control circuitry 12 can control the compressor 36 by controlling a first motor 48 that drives the compressor 36. The compressor 36 can be a constant-speed compressor 36. In some examples, the compressor 36 receives only an on command or not an on command (e.g., no speed input). In other examples, the compressor 36 can be controlled to a target rotational speed or power among a range of power commands. The fan 44 can also be controlled via a second motor 50 that drives the fan 44. The expansion device 40 can include an actuator 52, such as a third motor 52, that can be controlled via the control circuitry 12. By controlling these devices, the control circuitry 12 can execute a heat-pump control algorithm in which water in the tank 14 is heated via the heat pump 16 (e.g., heat transferred from the condenser 38 to the tank 14).

[0045] A mixing device 54 can optionally be provided for mixing water from a supply conduit 56 from a water utility (“cold water”) and heated or warmed water from the tank 14 via an output conduit 58. Accordingly, a target temperature for the tank 14 can exceed a setpoint temperature desired by the user, such that a temperature of a mixture of the supply water and warmed water reaches the setpoint temperature. The mixed water can be output via a mixed water conduit 60. The temperature of the tank 14 and / or the water therein can be determined using sensors 20a, 20b. Based on the temperature of the tank, the control circuitry 12 can activate / deactivate the heat pump 16 and / or the resistance heating element 18a, 18b to provide the warmed water at the target temperature. It should be understood that a setpoint temperature for the tank 14 can be greater than a setpoint temperature for the mixed water when a mixing device 54 is provided, and for examples without the mixing device 54, the setpoint temperature for the tank 14 can equal the setpoint temperature (i.e., there is no mixed water).

[0046] A user interface 64 can be provided in communication with the control circuitry 12 to allow user / technical personnel control of the water heater system 10 and for displaying information related to the water heater system 10. For example, the user interface 64 can include a display 66 that can indicate different diagnostic conditions, fault conditions, or operating conditions of the water heater system 10. The display 66 may be provided with the water heater system 10 or may be a display 66 remote from the water heater system 10. By way of example, the user interface 64 can include an interface of a mobile device executing a software application that allows the water heater system 10 and the mobile device to communicate with one another. In this way, the control circuitry 12 can communicatively couple with the user interface 64 via wired or wireless (e.g., Wi-Fi, Bluetooth, etc.) communication.

[0047] The control circuitry 12 includes a controller 68 having a processor 70 and a memory 72. The memory 72 can store instructions that, when executed by the processor 70, cause the controller 68 to perform tasks related to temperature estimation for the water heater system 10. The processor 70 may include any computing unit capable of executing instructions, such as a central processing unit (CPU), microcontroller unit (MCU), digital signal processor 70 (DSP), application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA). The processor 70 may be a single-core or multi-core unit and can be implemented as part of a system-on-chip (SoC) or as a standalone component.

[0048] The memory 72 can include any type of storage medium capable of storing data or instructions for execution by the processor 70. This includes volatile memory, such as random-access memory (RAM), and non-volatile memory, such as read-only memory (ROM), flash memory, electrically erasable programmable read-only memory (EEPROM), or magnetic or optical storage. The memory 72 may store executable program code, configuration data, sensor readings, or any other type of information necessary for the controller 68 to perform operations related to temperature estimation for the water heater system 10. The memory 72 and processor 70 may be integrated into a single package or exist as separate components interconnected by a bus or other communication means.

[0049] The controller 68 may be implemented as a discrete hardware device or as part of a larger system, such as a computer, embedded device, or Internet of Things (IoT) node. It may also include auxiliary components, such as communication interfaces, power management units, and analog-to-digital converters (ADCs) to interact with external devices or sensors. The processor 70 may execute firmware, software, or both, enabling the controller 68 to perform specific functions, such as processing input signals, executing control algorithms, or managing system resources for temperature estimation for the water heater system 10.

[0050] Referring now to FIGS. 2-5, the water heater system 10 can utilize the first sensor 20a and the second sensor 20b to estimate a representative temperature TREP of water in the tank 14. While the each of the sensors 20a, 20b can be configured to provide an indication of a temperature at only one proximity each, the control circuitry 12 can include one or more specialized algorithms to provide the representative temperature TREP for an accurate estimation of heat capacity of the tank 14. For example, the control circuitry 12 can provide a weighted average of the upper temperature T U and the lower temperature TL that, when multiplied by the volume of water in the tank 14, can produce an energy level. The software and hardware implements can therefore, in some examples, account for various temperature differentials and heat distribution patterns in the tank 14 when determining the representative temperature TREP. The upper temperature T U and the lower temperature TL can be determined by the control circuitry 12 and weighted by controlling a functional weight of each temperature T U, TL.

[0051] Referring now to the equations in FIG. 2, the functional weight accorded to each of the upper temperature T U and the lower temperature TL can be a function of a setpoint temperature TSP for the tank 14. In some examples, the functional weights are based on a weight factor X that is controlled by the control circuitry 12. For example, the weight factor X can represent a percentage, or portion of a whole, that is applied to one of the upper temperature T U and the lower temperature TL. For example, the representative temperature TREP can be a sum of a product of the lower temperature TL and the weight factor X and a product of a remainder of the whole (e.g., 1-X) and the upper temperature T U. Thus, by controlling the weight factor X, the control circuitry 12 controls a functional weight for each of the upper temperature T U and the lower temperature TL.

[0052] The functional weights can be a function of the setpoint temperature TSP and the lower temperature TL. For example, the weight factor X can be a function of a difference ΔT in the setpoint temperature TSP and the lower temperature TL. For example, the weight factor X can be controlled according to a linear function. For example, the weight factor X can equal a product of the difference ΔT and a gain value k plus an offset A. The gain value k can be predetermined or otherwise selected by the control circuitry 12 based on operation of the heating system.

[0053] The weight factor X can be controlled according to another function, such as a logarithmic, sinusoidal, arcuate, or other curve fit. For example, the linear fit may be applied between a low difference threshold TTHL and a high difference threshold TTHH only, in some examples. By way of example, the linear fit may be applicable for a fixed difference ΔT between the setpoint temperature TSP and the lower temperature TL. As will be described with respect to FIG. 3, the slope, or rate of change, for the linear fit can be controlled based on the weight factor X. As will be described in reference to FIG. 4, an offset A of the weight factor X can be controlled by the offset A. For example, operation of the heat pump 16 can cause the offset A to be increased or decreased. By way of example, the control circuitry 12 can negate the offset A when a heating system is not in use and increase the offset A when the heating system is in use.

[0054] Referring now to FIG. 3, a first plot 74 is presented demonstrating an example in which there is a relatively high difference ΔT in the setpoint temperature TSP and the lower temperature TL, and a second plot 76 demonstrates an example in which there is a relatively low difference ΔT in the setpoint temperature TSP and the lower temperature TL. In the first example, (e.g., the first plot 74), the setpoint temperature TSP is 140 degrees Fahrenheit (°F) and the lower temperature TL is 80 °F, thereby resulting in a difference ΔT of 60 °F. The upper temperature T U is 115 °F. An average temperature TAVG of the upper temperature T U and the lower temperature TL is 97.5 °F. In the present example, the control circuitry 12 determined a representative temperature TREP that is less than the average temperature TAVG (88.75 °F). The representative temperature TREP is calculated by determining the weight factor X based on the difference ΔT and applying the weight factor X to the lower temperature TL and the upper temperature T U. By way of example, the control circuitry 12 determines the weight factor X to be 75%, or 0.75, due to the relatively large difference ΔT of 60 °F. Accordingly, the control circuitry 12 determines the modified lower temperature TL to be 60 °F and a modified upper temperature T U of 28.75 °F based on a functional weight of 0.25 (1 – 0.75). The sum of these modified temperatures results in the control circuitry 12 determining the representative temperature TREP of 88.75 °F.

[0055] The control circuitry 12 can communicate an output based on the representative temperature TREP. For example, the control circuitry 12 can determine a heat capacity of the tank 14 and communicate a signal to a utility to report the heat capacity. In some examples, the representative temperature TREP can be used by the control circuitry 12 to control the heat pump 16 and / or the resistance heating elements 18a, 18b.

[0056] With reference to the second plot 76, the setpoint temperature TSP is 120 °F and the upper and lower temperatures TU, TL are the same as they are in the first plot 74. Accordingly, the difference ΔT is lower (40 °F) than in the first case (60 °F). In this example, the control circuitry 12 determines the weight factor X to be 40%. The resulting representative temperature TREP is 101 °F, which is above the average temperature TAVG of 97.5 °F.

[0057] The first and second plots 74, 76 demonstrated in FIG. 3 are during a deactivation period of the heating system. The weight factor X can be determined via a look-up table or other data structure that stores different weight factors X associated with each value of the difference ΔT. During operation of the heating system, the weight factor X can be adjusted to account for the increasing heat capacity being added to the tank 14 by the heating system.

[0058] Referring now to FIG. 4, a third plot 78 demonstrates two functions of the weight factor X as a function of the temperature difference ΔT. As demonstrated, the difference ΔT is modeled between the low difference threshold TTHL and the high difference threshold TTHH as a linear function. The thresholds TTHL, TTHH can be pre-determined or pre-programmed in the control circuitry 12. By way of example, the controller 68 can determine a first value of the difference ΔT associated with the compressor 36 being deactivated and a second value of the difference ΔT associated with the compressor 36 being activated. Although demonstrated as an adjustment of the offset A, the adjustment can be a combination of an adjustment of the offset A and an adjustment of the gain value k (e.g., slope).

[0059] Referring now to FIG. 5, a method 500 for operating a water heater system 10 includes determining a first temperature of water in an upper portion 30 of a tank 14 of the water heater at 502, determining a second temperature of water in a lower portion 32 of the tank 14 at 504, determining functional weights for the first temperature and the second temperature based on a difference ΔT between a target temperature for the water and the second temperature at 506, calculating a weighted average of the first temperature and the second temperature based on the functional weights at 508, determining a representative temperature TREP of the water based on the weighted average at 510, and communicating an output in response to the representative temperature TREP at 512.

[0060] In some examples, the method 500 includes any of the steps performed by the control circuitry 12 via execution of one or more of the algorithms previously described. Method 500 can include determining a heat capacity of the tank 14 based on the representative temperature TREP. Method 500 can include determining operation of the heat pump 16 of the heating system and determining the functional weights based on the operation of the heat pump 16.

[0061] In some examples, the control circuitry 12 can be configured to determine spikes, or sharp increases, in the difference ΔT. In such cases, the control circuitry 12 can mute, or disable, the determination of the representative temperature TREP. For example, the control circuitry 12 can selectively limit the determination of the representative temperature TREP when a large change (e.g., 20%) of the difference ΔT occurs in a time threshold (e.g., 1 second, 2 seconds, 5 seconds, 10 seconds). In general, the control circuit can detect these “spikes” and can limit use of the representative temperature TREP for calculation of the heat capacity. For example, the control circuitry 12 can instead use the average temperature TAVG or the lower temperature TL, or the upper temperature T U to determine heat capacity during spikes.

[0062] The temperature estimation systems and methods provided herein can provide for enhanced accuracy in thermal estimation for the tank 14 by modeling the thermal capacity of the tank 14 to a tank 14 having a vast number of temperature sensors. The water heater system 10 may also provide for lower manufacturing costs by utilizing, in some cases, only two sensors 20a, 20b to provide an accurate heat capacity model for the water. Further, the water heater system 10 may provide for enhanced determination based on heating system operation and utilizing the operation of which for precise temperature estimation.

Claims

1. A water heater system, comprising:a tank storing water;a first sensor operably coupled with an upper portion of the tank and that communicates a first signal;a second sensor operably coupled with a lower portion of the tank and that communicates a second signal; andcontrol circuitry configured to:determine a first temperature of water in the upper portion of the tank based on the first signal;determine a second temperature of water in the lower portion of the tank based on the second signal;determine functional weights for the first temperature and the second temperature based on a difference between a target temperature for the water and the second temperature;calculate a weighted average of the first temperature and the second temperature based on the functional weights;determine a representative temperature of the water based on the weighted average; andcommunicate an output in response to the representative temperature.

2. The water heater system of claim 1, wherein the control circuitry is configured to:determine a heat capacity of the tank based on the representative temperature.

3. The water heater system of claim 1, wherein the control circuitry is configured to determine the functional weights via a linear function of the difference.

4. The water heater system of claim 1, further comprising:a heating system configured to heat the water, wherein the control circuitry is configured to:determine operation of the heating system; anddetermine the functional weights based on the operation of the heating system.

5. The water heater system of claim 4, wherein the heating system includes a compressor, wherein the control circuitry is configured to adjust the functional weights while the compressor is activated.

6. A water heater system, comprising:a tank storing water;a first sensor operably coupled with an upper portion of the tank and that communicates a first signal;a second sensor operably coupled with a lower portion of the tank and that communicates a second signal; andcontrol circuitry configured to:determine a first temperature of water in the upper portion of the tank based on the first signal;determine a second temperature of water in the lower portion of the tank based on the second signal;control functional weights for each of the first temperature and the second temperature;calculate a weighted average of the first temperature and the second temperature based on the functional weights; anddetermine a representative temperature of the water based on the weighted average.

7. The water heater system of claim 6, wherein the representative temperature is an estimate of a mean temperature of the water.

8. The water heater system of claim 6, wherein the functional weights are determined based on a difference between the second temperature and a target temperature for the water.

9. The water heater system of claim 8, wherein the control circuitry is configured to determine the functional weights as a function of the difference.

10. The water heater system of claim 9, wherein the function is a linear function between a low difference threshold and a high difference threshold.

11. The water heater system of claim 6, wherein calculating the weighted average includes summing of a first product of a first functional weight and the first temperature and a second product of a second functional weight and the second temperature.

12. The water heater system of claim 11, wherein the first functional weight is a first percentage and the second functional weight is a whole less the first percentage.

13. The water heater system of claim 6, wherein the control circuitry is configured to:determine a heat capacity of the tank based on the representative temperature.

14. The water heater system of claim 6, further comprising:a heating system configured to heat the water, wherein the control circuitry is configured to:determine operation of the heating system; anddetermine the functional weights based on the operation of the heating system.

15. The water heater system of claim 14, wherein the heating system includes a heat pump, wherein the control circuitry is configured to adjust the functional weights during operation of the heat pump.

16. The water heater system of claim 15, wherein the heat pump includes a compressor, wherein the control circuitry is configured to adjust the weighted average while the compressor is activated.

17. The water heater system of claim 6, wherein at least one of the first sensor and the second sensor includes a temperature sensor.

18. A method for operating a water heater system that heats water, comprising:determining a first temperature of water in an upper portion of a tank of the water heater;determining a second temperature of water in a lower portion of the tank;determining functional weights for the first temperature and the second temperature based on a difference between a target temperature for the water and the second temperature;calculating a weighted average of the first temperature and the second temperature based on the functional weights;determining a representative temperature of the water based on the weighted average; andcommunicating an output in response to the representative temperature.

19. The method of claim 18, further comprising:determining a heat capacity of the tank based on the representative temperature.

20. The method of claim 18, further comprising:determining operation of a heat pump of the water heater system; anddetermining the functional weights based on the operation of the heat pump.

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