Control method for preheating of high-efficiency energy-saving direct-current heat pump water heater

Abstract

The application relates to the field of heat pump water heaters, and particularly discloses a control method for preheating of a high-efficiency energy-saving direct-current heat pump water heater, which comprises the following steps: predicting the ambient temperature of a space where an outdoor unit of the heat pump water heater is located; judging whether the ambient temperature exceeds a set temperature threshold; if yes, determining the loss heat between heating completion and user use under the ambient temperature and the saved heat of heating under the ambient temperature relative to heating when the user uses; comparing the loss heat with the saved heat; and selectively starting the heat pump water heater for early heating according to the comparison result. The application utilizes the promoting effect of higher ambient temperature on heat exchange of an evaporator of the heat pump water heater, heats and stores heat in the highest period of external ambient temperature, reduces product energy consumption, saves electricity charges, enables the user to use hot water without waiting, improves user experience, and achieves multiple purposes at one time.

Description

Technical Field

[0001] This application relates to the field of heat pump water heaters, and more specifically, to a control method for preheating a high-efficiency and energy-saving DC heat pump water heater. Background Technology

[0002] Currently, heat pump water heaters have become a fairly common household appliance. There are many types of heat pump water heaters on the market, mainly including three series: solar-assisted, water-source, and air-source. Solar-assisted heat pumps combine heat pump technology with solar energy; water-source heat pumps use water at a certain temperature (above 20℃) as a heat source, with a refrigerant as the medium. The heat from the water is absorbed, compressed by a compressor, and then exchanged with cold water through a heat exchanger to achieve the purpose of heating and producing hot water. Water-source heat pumps require a water source with a certain temperature and flow rate; air-source heat pumps use a similar method to water-source heat pumps, obtaining heat from the air to heat water.

[0003] A heat pump water heater typically consists of a water tank and a refrigerant circulation loop. The water tank includes an outer shell and an inner liner. The refrigerant circulation loop includes a compressor, condenser, throttling device, and an evaporator located outdoors, all connected together. The water tank is designed to exchange heat with the condenser and is thus heated. The specific working process is as follows: Liquid refrigerant absorbs heat in the evaporator and evaporates into gaseous refrigerant. The gaseous refrigerant exiting the evaporator is compressed by the compressor, becoming a high-temperature, high-pressure gaseous refrigerant. This high-temperature, high-pressure gaseous refrigerant releases heat energy in the condenser, thus heating the water in the tank, while simultaneously becoming a high-pressure liquid refrigerant. This high-pressure liquid refrigerant is converted back into liquid refrigerant in the throttling device and enters the evaporator, repeating the initial process. In short, a heat pump water heater transfers heat through the gas-phase changes (boiling and condensation) of the flowing refrigerant in components such as the evaporator, compressor, and condenser. Utilizing the principle of a heat pump, it produces more hot water using one kilowatt-hour of electricity than a conventional electric water heater using three kilowatt-hours, a feat unmatched by traditional water heaters.

[0004] Typically, users use hot water in the early morning and at night. However, the current technology requires users to turn on the heat pump water heater temporarily before use to start heating, without considering the energy efficiency of the heat pump water heater or the electricity cost, which is very unintelligent.

[0005] Since the coefficient of performance (COP) of a heat pump water heater is affected by the ambient temperature, the higher the ambient temperature, the higher the evaporation temperature of the heat pump, the higher the COP, and the lower the energy consumption. If the heating starts in the early morning or evening, the outdoor ambient temperature in this period is significantly different from the day's highest temperature, resulting in a lower COP and higher energy consumption.

[0006] Current technical solutions have failed to effectively utilize the high outdoor temperature environment to reduce the energy consumption of DC heat pump water heaters and decrease electricity costs. Therefore, this invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a highly efficient and energy-saving heat pump water heater preheating control method that utilizes the relatively high outdoor ambient temperature to improve the energy efficiency of the heat pump water heater, thereby achieving energy saving and consumption reduction.

[0008] Specifically, the present invention provides a method for controlling the preheating of a heat pump water heater, the method comprising the following steps:

[0009] Predict the ambient temperature of the space where the outdoor unit of the heat pump water heater is located;

[0010] Determine whether the ambient temperature exceeds the set temperature threshold;

[0011] If the heat loss is exceeded, the heat loss between the completion of heating at the ambient temperature and the user's use is determined, as well as the heat saving during heating at the ambient temperature relative to the heat saving during user use.

[0012] Compare the heat loss with the heat saving;

[0013] Based on the comparison results, the heat pump water heater is selectively activated for preheating.

[0014] In a specific implementation of the above control method, the step of "predicting the ambient temperature of the space where the outdoor unit of the heat pump water heater is located" specifically includes:

[0015] The ambient temperature of the space where the outdoor unit of the heat pump water heater is located is predicted in advance based on the weather forecast for each day, or the ambient temperature of the space where the outdoor unit of the heat pump water heater is located is predicted in real time based on IoT data.

[0016] In a specific implementation of the above control method, the step of "selectively activating the heat pump water heater for preheating based on the comparison results" specifically includes:

[0017] If the heat loss is less than the heat saving, then the heat pump water heater is activated for preheating; and / or

[0018] If the heat loss exceeds the heat saving, the heat pump water heater will not be activated for preheating.

[0019] In a specific implementation of the above control method, the step of "selectively activating the heat pump water heater for preheating based on the comparison results" specifically includes:

[0020] If the heat loss exceeds the heat saving, then the extent to which the heat loss exceeds the heat saving is further determined.

[0021] If the amplitude exceeds the preset heat threshold, the heat pump water heater will not be activated for preheating; otherwise, the heat pump water heater will be activated for preheating.

[0022] In a specific embodiment of the above control method, the heat pump water heater includes a heat storage module, and the control method further includes:

[0023] Before comparing the heat loss with the heat saving, first compare the heat loss between the completion of heating and the user's use with the maximum heat storage capacity of the heat storage module.

[0024] Based on the comparison results, the heat loss and the heat saving are selectively compared.

[0025] In a specific implementation of the above control method, the step of "selectively comparing the lost heat with the saved heat based on the comparison results" specifically includes:

[0026] The comparison between the heat loss and the heat saving is only performed when the heat loss is less than the maximum heat storage.

[0027] In a specific implementation of the above control method, the step of "determining the heat loss between the completion of heating at the ambient temperature and user use" specifically includes:

[0028] Get the time when the user arrives home, and predict when the user will use hot water based on this;

[0029] The heat loss is determined based on the time difference between the time the user uses hot water and the time corresponding to the ambient temperature.

[0030] In a specific implementation of the above control method, the step of "determining the heat loss based on the time difference between the time the user uses hot water and the time corresponding to the ambient temperature" further includes:

[0031] The heat loss is determined based on the time difference between the user's arrival time and the time corresponding to the ambient temperature, combined with the heat storage and / or insulation measures of the heat pump water heater.

[0032] In a specific implementation of the above control method, the step of "obtaining the user's arrival time" includes: obtaining the user's arrival time by asking the user and receiving feedback, or predicting the user's arrival time based on historical data and / or the user's current location.

[0033] In a specific implementation of the above control method, the "heat saving of heating at the ambient temperature relative to the heat saving during user use" is determined based on the heating efficiency of the heat pump water heater under different external ambient temperatures.

[0034] By adopting the above technical solution, the present invention predicts the ambient temperature of the space where the outdoor unit of the heat pump water heater is located, and utilizes the promoting effect of the outdoor ambient temperature on the heat exchange of the evaporator of the heat pump water heater. When the external ambient temperature is high, heat is stored in advance, which not only reduces product energy consumption and saves electricity bills, but also allows users to use hot water without waiting, thus improving the user experience. It can be said to have multiple benefits.

[0035] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0037] Figure 1 This is a schematic diagram of the structure of a heat pump water heater according to an embodiment of this application;

[0038] Figure 2 This is a schematic diagram of the main steps of the control method for preheating a DC heat pump water heater according to this application;

[0039] Figure 3 This is a detailed flowchart of the control method for preheating a high-efficiency energy-saving DC heat pump water heater according to the first embodiment of this application;

[0040] Figure 4 This is a detailed flowchart of the control method for preheating a high-efficiency energy-saving DC heat pump water heater according to the second embodiment of this application;

[0041] List of reference numerals in the attached diagram: 1. Compressor; 2. Condenser; 3. Throttling device; 4. Evaporator; 5. Energy storage module; 6. Temperature prediction module; 7. Water tank. Detailed Implementation

[0042] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0043] like Figure 1As shown, the heat pump water heater, as the application object of the control method of this application, includes a water tank 7 and a refrigerant circulation loop. The water tank 7 includes an outer shell and an inner tank. Figure 1 (Not shown), the refrigerant circulation loop includes a compressor 1, a condenser 2, a throttling device 3, and an evaporator 4 located outdoors, all connected together. The water tank 7 is configured to exchange heat with the condenser 2 and is therefore heated. (Reference) Figure 1 The specific working process of this heat pump water heater is as follows: The liquid refrigerant absorbs heat in the evaporator 4 and evaporates into gaseous refrigerant. The gaseous refrigerant coming out of the evaporator 4 is compressed by the compressor 1, becoming a high-temperature, high-pressure gaseous refrigerant. The high-temperature, high-pressure gaseous refrigerant releases heat energy in the condenser 2, thus heating the water in the water tank 7, while simultaneously becoming a high-pressure liquid refrigerant. The high-pressure liquid refrigerant is depressurized in the throttling device 3, becoming a normal-pressure liquid refrigerant again, and then enters the evaporator 4, repeating the initial process. In simple terms, the heat pump water heater transfers heat through the gas phase changes (boiling and condensation) of the flowing refrigerant in components such as the evaporator 4, compressor 1, and condenser 2, and finally transfers the heat to the water in the water tank 7 through the condenser 2.

[0044] like Figure 1 As shown, the heat pump water heater also includes a temperature prediction module 6. This module predicts the ambient temperature of the space where the outdoor unit of the heat pump water heater is located in advance, so that the heat pump water heater can determine the start time for preheating. Specifically, temperature prediction can be based on various information sources, such as weather forecasts and the Internet of Things (IoT). Accordingly, the temperature prediction module 6 is typically configured as a communication module. This invention does not limit the specific form of the prediction module 6, as long as it can predict the ambient temperature of the space where the outdoor unit of the heat pump water heater is located.

[0045] The heat pump water heater described above can perform the preheating control method for a high-efficiency, energy-saving DC heat pump water heater that utilizes the temperature difference between the outdoor and ambient temperatures to improve the energy efficiency of the heat pump water heater, as disclosed in the following embodiments.

[0046] See next. Figure 2 The heat pump water heater preheating control method of the present invention includes the following steps:

[0047] S10: Predict the ambient temperature of the space where the outdoor unit of the heat pump water heater is located;

[0048] In particular, the technical solution of this invention is typically used in heat pump water heaters that do not have an ambient temperature sensor. As described above... Figure 1As described, in this scenario, a temperature prediction module 6 can be installed on the outdoor unit of the heat pump water heater to predict the temperature based on various information sources, such as weather forecasts and the Internet of Things (IoT). Specifically, the temperature prediction module 6 can be configured as a communication module capable of receiving weather forecasts from the outside, thereby predicting the ambient temperature of the space where the outdoor unit of the heat pump water heater is located throughout the day based on the temperature for each time period included in the weather forecast. Alternatively, the temperature prediction module 6 can also be configured as a communication module capable of receiving real-time ambient temperature from other nearby household appliances or devices equipped with temperature sensors, thereby predicting the ambient temperature of the space where the outdoor unit of the heat pump water heater is located throughout the day. In practice, the temperature prediction module 6 can be installed independently or can directly utilize the communication module built into the heat pump water heater itself, as long as it can receive weather or temperature information from external or nearby devices.

[0049] S11: Determine whether the ambient temperature exceeds the set temperature threshold;

[0050] The set temperature threshold can be obtained through simulation experiments or through historical data. For example, the ambient temperature can be collected every 10 minutes, the COP corresponding to each temperature can be calculated, and then the set temperature threshold T0 can be determined based on the magnitude of the COP. Specifically, the temperature threshold can be set based on the average value obtained from a high-temperature range, for example, a temperature threshold of 28°C in summer and 22°C in winter.

[0051] S12: If it exceeds, determine the heat loss between the completion of heating at ambient temperature and user use, as well as the heat saving of heating at ambient temperature relative to heating during user use;

[0052] For example, if the predicted time for the ambient temperature to exceed the set temperature threshold is 12:00 noon, and the ambient temperature T1 at that time is 30°C, which exceeds the set temperature threshold of 28°C, then the heat loss between the completion of heating (assuming 12:20) and the user's use at 19:00 in the evening, as well as the heat saving of heating at 12:00 relative to heating when the user uses the device at 19:00 in the evening, are determined.

[0053] The heat loss mainly depends on parameters such as the heat pump water heater's insulation measures, water temperature, ambient temperature, and storage time. As an example, a heat loss model can be pre-trained for a specific model of heat pump water heater, and then used to predict the heat loss between heating completion and user use. Specifically, the formula for calculating heat loss is: Q = C * m * Δt, where m is the mass of water in the tank, C is the specific heat capacity of water, and Δt is the temperature difference before and after heat loss. This formula can be used to calculate the heat loss at different times and temperatures, and then a three-dimensional mapping function between time difference, temperature, and heat loss can be established as the heat loss model. When it is necessary to determine the heat loss at a specific time point under the ambient temperature, simply input the time difference and ambient temperature as query terms into the function model to retrieve the corresponding heat loss. In the example above, the time difference is 6 hours and 40 minutes, and the ambient temperature is 30℃, thus allowing the retrieval of the corresponding heat loss.

[0054] Regarding the heat savings from heating at the stated ambient temperature relative to heating during user use, since the coefficient of performance (COP) of a heat pump water heater increases by at least 20% for every 5°C increase in the evaporation temperature of the evaporator (e.g., from 22°C to 27°C), the corresponding energy consumption decreases by at least 20%. Therefore, similar to heat loss, a mapping relationship between COP and ambient temperature can be constructed by pre-training a model. The heat savings are then calculated using the difference between the COP corresponding to the current ambient temperature and the ambient temperature at which the user uses hot water. Specifically, the ambient temperature for each time period is obtained through prediction, and the ambient temperature at which the user uses hot water is also predicted through weather forecasts or other methods. The corresponding COP values ​​are then retrieved, and the difference between the two is calculated. Finally, the heat savings corresponding to this COP difference are calculated. The calculation method for the heat savings corresponding to the COP difference is well-known to those skilled in the art and varies depending on the water heater model; therefore, the calculation process will not be described in detail here.

[0055] It should be noted that although the determination of heat loss and heat saving is illustrated here using a pre-trained model and mapping function as examples, this is not restrictive. Without departing from the principles of the present invention, those skilled in the art can use any other suitable method as needed to determine heat loss and heat saving.

[0056] S13: Compare the heat loss with the heat saving;

[0057] S14: Based on the comparison results, selectively activate the heat pump water heater for preheating.

[0058] Specifically, in Figure 3In the first embodiment shown, if the heat loss is less than the heat saving, the heat pump water heater is activated for preheating; if the heat loss exceeds the heat saving, the heat pump water heater is not activated for preheating. Figure 4 In the second embodiment shown, if the heat loss is less than the heat saving, the heat pump water heater is started for preheating; if the heat loss exceeds the heat saving, but the excess is within a set threshold range, the heat pump water heater is still started for preheating; conversely, if the heat loss exceeds the heat saving by more than the set threshold, the heat pump water heater is not started for preheating.

[0059] As mentioned above, for every 5°C increase in the evaporation temperature of the evaporator in a heat pump water heater (e.g., from 22°C to 27°C), the coefficient of performance (COP) of the heat pump water heater can increase by at least 20%, and the corresponding energy consumption can decrease by at least 20%. Typically, users consume hot water in the early morning and at night, when the temperature difference between the outdoor ambient temperature and the day's highest temperature can be at least 5°C. Furthermore, since the high-temperature period is mostly around noon, when temperatures are highest, the power grid supply is sufficient, and electricity prices are low, heating during this period can save on electricity costs. In other words, this invention utilizes the promoting effect of the higher outdoor ambient temperature on the heat exchange of the heat pump water heater's evaporator, heating and storing heat during the period of highest external ambient temperature. This not only reduces product energy consumption and saves on electricity costs but also allows users to use hot water without waiting, improving the user experience—a win-win situation.

[0060] See below. Figure 3 The first specific embodiment of the present invention will be described below.

[0061] like Figure 3 As shown, in the first specific embodiment, the step of "selectively activating the heat pump water heater for preheating based on the comparison result" specifically includes: if the heat loss is less than the heat saving, then activating the heat pump water heater for preheating; and / or if the heat loss exceeds the heat saving, then not activating the heat pump water heater for preheating.

[0062] Specifically, in this implementation, economy is the core consideration. If the heat loss is less than the heat saving, it proves that the overall energy saving is achieved. Furthermore, heating occurs during the period of highest ambient temperature, when electricity prices are typically lower, resulting in electricity cost savings. Therefore, the heat pump water heater is activated for preheating. Conversely, if the heat loss exceeds the heat saving, it proves that the energy saving effect gained through the improved heat pump efficiency is offset by the heat consumed in preheating the hot water, resulting in higher overall energy consumption. Therefore, the heat pump water heater is not activated for preheating.

[0063] More specifically, such as Figure 3As shown, in the first embodiment, the model of the heat pump water heater and the maximum additional heat storage capacity Qsmax of the heat pump water heater are first obtained. The model of the heat pump water heater is used to call the corresponding heat loss model to calculate the heat loss and to calculate the heat saving based on its corresponding COP. The maximum heat storage capacity Qsmax is used to determine the subsequent operation steps, which will be described in detail below.

[0064] Continue reading Figure 3 In the next step, the time and temperature at which the user uses hot water are determined. Both the time and temperature of hot water usage are used to calculate heat loss and savings, ultimately deciding whether to preheat the water. Specifically, the user's arrival time is first obtained, and then the time when the user will use hot water is estimated based on that. For example, historical data can be used to estimate the time the user will use hot water some time after arriving home, such as one hour later. More specifically, various methods can be used to determine the user's arrival time, such as obtaining the arrival time by asking the user and receiving feedback, or predicting the arrival time based on historical data and / or the user's current location. Furthermore, the user's arrival time can be obtained by using connected smart cars, smartwatches, smartphones, etc., or by obtaining the user's navigation information from smart cars or smartphones and predicting the arrival time accordingly. Alternatively, the user's arrival time can be directly inferred from historical data.

[0065] like Figure 3 As shown, the next step is to predict the ambient temperature T1 of the space where the outdoor unit of the heat pump water heater is located and compare it with the temperature threshold T0. The methods for obtaining T1 and T0 have already been explained above. Figure 2 The details have been described in detail, so I won't repeat them here.

[0066] Continue reading Figure 3 When T1 is greater than T0, the heat loss between the completion of heating at ambient temperature and user use is calculated, along with the heat saving during heating at ambient temperature relative to user use. However, the two are not directly compared; instead, the heat loss is first compared with the maximum additional heat storage capacity Qsmax of the heat pump water heater. Then, based on the comparison results, the heat loss and the heat saving are selectively compared. Specifically, in... Figure 3 In the illustrated implementation, the comparison between the heat loss and the heat saving is performed only when the heat loss is less than the maximum additional heat storage Qsmax. If the heat loss is greater than the maximum additional heat storage Qsmax, it indicates that the time interval between heating and user use is too long, resulting in excessive heat loss and poor economic efficiency; therefore, no operational judgment is made.

[0067] Regarding the maximum additional heat storage capacity Qsmax, the heat pump water heater of this invention includes a heat storage module, and its additional heat storage capacity is mainly achieved through the heat storage module. This invention does not limit the form and installation location of the heat storage module; it can be either simply increasing the inner tank capacity of the water tank or adding a phase change energy storage module, as long as it can increase the heat storage capacity, thereby achieving the maximum heat storage capacity.

[0068] Continue reading Figure 3 When the heat loss is less than the maximum additional heat storage Qsmax, the heat loss between the completion of heating at ambient temperature and the user's use is compared with the heat saving during heating at ambient temperature relative to the user's use. If the heat loss is less than the heat saving, the heat pump water heater is started for preheating; if the heat loss exceeds the heat saving, the heat pump water heater is not started for preheating.

[0069] The calculation methods for heat loss and heat saving have been explained above. Figure 2 The details have been explained in detail and will not be repeated here. It is worth noting that "heat saving at ambient temperature relative to user-operated heating" is determined based on the heating efficiency of the heat pump water heater under different external ambient temperatures. Here, "heating efficiency under different external ambient temperatures" refers to the COP of the heat pump water heater at those different external ambient temperatures. Similarly, as mentioned above... Figure 2 As stated above, those skilled in the art can use any suitable method as needed to calculate heat loss and heat saving, which should not constitute any limitation on the scope of protection of this invention.

[0070] The following reference Figure 4 This describes a control method for preheating a heat pump water heater according to a second specific embodiment of the present invention. For example... Figure 4 As shown, the second embodiment is basically the same as the first embodiment, except that the processing method after comparing heat loss and heat saving is different.

[0071] Specifically, in Figure 4 In the second embodiment, if it is determined that the heat loss exceeds the heat saving, the extent by which the heat loss exceeds the heat saving is further determined and it is determined whether the extent exceeds a preset heat threshold. If the extent exceeds the preset heat threshold, the heat pump water heater is not started for preheating; otherwise, the heat pump water heater is started for preheating.

[0072] More specifically, the second implementation does not directly abandon preheating when heat loss exceeds heat saving. Instead, it further assesses the extent of the excess. When the excess is not significant (i.e., not exceeding a preset heat threshold), preheating is still chosen to ensure users have access to hot water promptly, guaranteeing a positive user experience. Conversely, when the excess is significant (i.e., exceeding the preset heat threshold), it indicates that preheating is not economically viable, and therefore preheating is not chosen. In other words, Figure 4 The second implementation method does not strictly follow the economic principle and make a one-size-fits-all judgment, but rather comprehensively weighs the economic and user experience, and prioritizes the user experience when the economic efficiency is not particularly bad.

[0073] Regarding the preset heat threshold, it can be flexibly set by those skilled in the art according to the needs of the application scenario, and the present invention does not impose any restrictions on it. As an example, it should generally not exceed 10% of the saved heat. In addition, the heat threshold can also be set with reference to the electricity cost saved by preheating. Specifically, although the heat loss exceeds the heat saving, preheating is often carried out during off-peak hours, which can save electricity costs. The preset heat threshold can be set to the energy value corresponding to the saved electricity cost.

[0074] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0075] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and adjustments can be made without departing from the principle of this application, and these improvements and adjustments should also be considered to fall within the protection scope of this application.

Claims

1. A method for controlling preheating in a heat pump water heater, characterized in that, The method includes the following steps: Predict the ambient temperature of the space where the outdoor unit of the heat pump water heater is located; Determine whether the ambient temperature exceeds the set temperature threshold; If the heat loss is exceeded, the heat loss between the completion of heating at the ambient temperature and the user's use is determined, as well as the heat saving during heating at the ambient temperature relative to the heat saving during user use. Compare the heat loss with the heat saving; Based on the comparison results, the heat pump water heater is selectively activated for preheating.

2. The control method for preheating a heat pump water heater according to claim 1, characterized in that, The steps of "predicting the ambient temperature of the space where the outdoor unit of the heat pump water heater is located" specifically include: The ambient temperature of the space where the outdoor unit of the heat pump water heater is located is predicted in advance based on daily weather forecasts for each time of day, or the ambient temperature of the space where the outdoor unit of the heat pump water heater is located is predicted in real time based on IoT data for each time of day.

3. The control method for preheating a heat pump water heater according to claim 1, characterized in that, The step of "selectively activating the heat pump water heater for preheating based on the comparison results" specifically includes: If the heat loss is less than the heat saving, then the heat pump water heater is activated for preheating; and / or If the heat loss exceeds the heat saving, the heat pump water heater will not be activated for preheating.

4. The control method for preheating a heat pump water heater according to claim 1, characterized in that, The step of "selectively activating the heat pump water heater for preheating based on the comparison results" specifically includes: If the heat loss exceeds the heat saving, the extent by which the heat loss exceeds the heat saving is further determined. If the extent exceeds a preset heat threshold, the heat pump water heater is not started for preheating; otherwise, the heat pump water heater is started for preheating.

5. The control method for preheating a heat pump water heater according to claim 1, characterized in that, The heat pump water heater includes a heat storage module, and the control method further includes: Before comparing the heat loss with the heat saving, first compare the heat loss between the completion of heating and the user's use with the maximum heat storage capacity of the heat storage module. Based on the comparison results, the heat loss and the heat saving are selectively compared.

6. The control method for preheating a heat pump water heater according to claim 5, characterized in that, The step of "selectively comparing the lost heat with the saved heat based on the comparison results" specifically includes: The comparison between the heat loss and the heat saving is only performed when the heat loss is less than the maximum heat storage.

7. The control method for preheating a heat pump water heater according to any one of claims 1 to 6, characterized in that, The step of "determining the heat loss between the completion of heating at the ambient temperature and user use" specifically includes: Get the time when the user arrives home, and predict when the user will use hot water based on this; The heat loss is determined based on the time difference between the time the user uses hot water and the time corresponding to the ambient temperature.

8. The control method for preheating a heat pump water heater according to claim 7, characterized in that, The step of "determining the heat loss based on the time difference between the time the user uses hot water and the time corresponding to the ambient temperature" further includes: The heat loss is determined based on the time difference between the user's arrival time and the time corresponding to the ambient temperature, combined with the heat storage and / or insulation measures of the heat pump water heater.

9. The control method for preheating a heat pump water heater according to claim 7, characterized in that, The steps to "obtain the user's arrival time" include: obtaining the user's arrival time by asking the user and receiving feedback, or predicting the user's arrival time based on historical data and / or the user's current location.

10. The control method for preheating a heat pump water heater according to any one of claims 1 to 6, characterized in that, The "heat saving at the ambient temperature relative to the heat saving during user use" is determined based on the heating efficiency of the heat pump water heater under different external ambient temperatures.

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