Variable-volume air source heat pump hot water supply system with energy storage function and control method

Abstract

The invention relates to the technical field of heat energy utilization, and mainly discloses a variable-volume air source heat pump hot water supply system with an energy storage function and a control method.The system comprises an air source heat pump, a heat storage water tank, a circulating pump set, a sensor module and a controller, and variable-volume energy storage of the heat storage water tank is controlled through an electromagnetic valve and a floating ball valve; and dynamically adjusting a heat pump operation strategy in combination with the time-of-use electricity price and the photovoltaic electricity abandoning state. The system has four working states, a time-of-use electricity price regulation and control parameter table and a water demand coefficient are adopted to dynamically set a target liquid level, automatic switching of energy storage and energy discharge is achieved, when the photovoltaic inverter is in a power abandoning state, heat storage is preferentially carried out to absorb green power, water is used as a heat storage medium, constant-temperature energy storage is achieved through volume change, and energy storage efficiency is improved. The problems that a traditional heat storage mode is high in cost and large in temperature fluctuation are solved, and the advantages of economy and safety are achieved.

Description

Technical Field

[0001] This invention relates to the field of thermal energy utilization technology, specifically a variable volume air source heat pump hot water supply system and control method with energy storage function. Background Technology

[0002] An air source heat pump hot water supply system uses an air source heat pump as the heat source to provide users with hot water that meets design requirements in terms of quantity, temperature, pressure, and quality. The system includes a hot water storage tank, a primary circulation system consisting of the air source heat pump and the hot water tank, a secondary circulation system consisting of the hot water tank and the user's water-using equipment, and other accessories such as automatic temperature control valves. To ensure a continuous supply of hot water, the hot water tank in the system is generally large, and water is replenished promptly when the tank level drops. Since the temperature of the replenished water is lower than that of the water in the tank, it can cause the water temperature in the tank to drop. The hot water supply system has a temperature control function, using the air source heat pump to heat the hot water in the tank, maintaining a relatively constant temperature.

[0003] With the gradual improvement of the domestic time-of-use electricity pricing mechanism, energy storage systems play an important role in guiding users to peak and valley filling, improving the power supply and demand situation, and promoting the consumption of new energy sources. Currently, there are two main energy storage methods for air source heat pump water heating systems: First, battery energy storage, typically combined with a photovoltaic system. When there is sunlight, solar energy is converted into electrical energy, simultaneously charging the battery bank and converting the electrical energy into chemical energy for storage. When there is no sunlight, the battery supplies power to the solar-controlled inverter, which then supplies power to the AC load. Second, thermal storage is used, storing excess heat in a thermal storage medium. When heat is needed, the heat is released. Commonly used thermal storage media include water and phase change materials.

[0004] Depending on market conditions and product type, existing technologies for air source heat pump hot water supply systems mainly suffer from the following four types of technical defects.

[0005] The first type of product is a hot water supply system without energy storage capabilities. This type of system cannot automatically adjust its control strategy according to time-of-use electricity price fluctuations, resulting in relatively high operating electricity costs.

[0006] The second type of product can be used in conjunction with a photovoltaic energy storage system for hot water supply. This method automatically stores the electrical energy generated by the photovoltaic system through batteries and inverts it into AC power during peak electricity prices to reduce electricity costs. The disadvantages of this method are the higher cost of batteries, battery life and degradation, and fire safety hazards.

[0007] The third type of product uses sensible heat storage, utilizing the inherent heat capacity of materials to store thermal energy in a hot water control system. This method achieves thermal energy storage by heating the storage material to increase its temperature and internal energy. Currently, water is the most common energy storage material in air source heat pump hot water systems. The main drawback of this method is that it relies on the temperature change of the storage material for heat storage; the heat release process cannot maintain a constant temperature, resulting in low heat storage density.

[0008] The fourth type of product employs phase change thermal storage, utilizing the phase change of the thermal storage material under thermal action to achieve heat storage and release in a hot water control system. Phase change thermal storage has the advantages of high energy density and small temperature fluctuation range during heat release, but the high price of materials is an obstacle to its widespread application. Furthermore, because the phase change temperature of phase change materials is fixed, it is not suitable for temperature control. Summary of the Invention

[0009] This invention addresses the technical problems existing in the prior art by proposing a hot water supply system and control method with energy storage function. The system's energy storage and release processes are achieved by adjusting the volume of hot water in the storage tank. Energy storage is achieved by increasing the hot water volume, and energy release is achieved by decreasing the hot water volume.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: a variable-capacity air-source heat pump hot water supply system with energy storage function, comprising an air-source heat pump, a heat source circulation pump, a solenoid valve, a float valve, a hot water storage tank, a hot water circulation pump, a photovoltaic inverter, a controller, and a sensor module. The sensor module includes a liquid level sensor, a water supply temperature sensor, a water supply pressure sensor, and an outdoor temperature sensor. A solenoid valve and a float valve are connected in series between the tap water side and the hot water storage tank. The bottom of the hot water storage tank is connected to the air-source heat pump through the heat source circulation pump. The air-source heat pump is connected to the heat source return port located at the top of the hot water storage tank to form a circulation loop. The bottom of the hot water storage tank is also connected to the water-using side through the hot water circulation pump, and the hot water circulation pump is also connected to the top of the hot water storage tank. A circulation loop is formed. The liquid level sensor is installed inside the hot water storage tank to detect the liquid level depth in the tank. The water supply temperature sensor is installed between the hot water storage tank and the hot water circulation pump to detect the water supply temperature on the water-using side. The water supply pressure sensor is installed between the hot water circulation pump and the water-using side to detect the water supply pressure on the water-using side. The outdoor temperature sensor is used to detect the outdoor ambient temperature. The photovoltaic inverter, solenoid valve, air source heat pump, heat source circulation pump, hot water circulation pump, liquid level sensor, water supply temperature sensor, water supply pressure sensor, and outdoor temperature sensor are all communicatively connected to the controller. The sensors are used to collect signals from each sensor and control the on / off state of the corresponding solenoid valve, air source heat pump, heat source circulation pump, and hot water circulation pump.

[0011] Through the above technical solution, the hot water storage tank is an insulated open-type water tank with two pipes at the bottom, connected to a heat source circulation pump and a hot water circulation pump respectively. The air source heat pump uses electricity to absorb heat energy from the air, heating the water in the storage tank. The heated water is then injected into the storage tank from the top. The hot water circulation pump provides continuous hot water circulation to the water user side. The circulating water flows through the water user side and then into the storage tank from the top. A photovoltaic system inverter with a communication interface is included. The air source heat pump hot water system controller can collect the inverter's operating status and determine whether the photovoltaic system is wasting electricity based on whether the inverter is in "limited power operation" or "diluted operation" state. When the air source heat pump equipment enters heating mode, the heat source circulation pump needs to be turned on to circulate water between the air source heat pump and the storage tank. The system comprises a ring; a solenoid valve for controlling the supply of tap water to the hot water storage tank; a float valve for preventing water overflow from the tank due to continuous water supply; a level sensor for detecting the water level in the tank and calculating its volume; a water supply temperature sensor for detecting the water supply temperature on the user side, serving as the basis for system temperature control; a water supply pressure sensor for detecting the water supply pressure on the user side; and an outdoor temperature sensor for detecting the outdoor ambient temperature, used for temperature compensation of the water supply temperature. The system's control functions can be achieved through a PLC controller or other control circuits.

[0012] A further technical solution of the present invention is that the supply system includes four working states: Stopped When the hot water circulation pump is turned off, the hot water supply to the user side stops; when the solenoid valve is closed, tap water will not automatically replenish the hot water storage tank. The air source heat pump determines whether it starts by using its internal antifreeze strategy. If the air source heat pump starts, the heat source circulation pump starts to heat the water in the storage tank. If the air source heat pump stops, the heat source circulation pump stops.

[0013] standby mode When the hot water circulation pump is turned on, hot water is supplied normally to the water user; when the solenoid valve is closed, tap water will not automatically replenish the hot water storage tank. The air source heat pump is off, and the heat source circulation pump is off.

[0014] Heating state The hot water circulation pump is turned on, and hot water is supplied normally to the water-using side; the air source heat pump is started, and the heat source circulation pump is started to heat the water in the hot water storage tank; the solenoid valve is opened to fill the tank with water based on the water temperature and liquid level, and the water supply temperature must be maintained at the required level during the filling process.

[0015] Water injection status The hot water circulation pump is turned off, and the supply of hot water to the water-using side stops; the air source heat pump is turned off, and the heat source circulation pump is turned off; the solenoid valve is turned on, and under the action of tap water pressure, tap water is automatically replenished to the hot water storage tank until the liquid level rises to the protection level, and then the water filling stops.

[0016] A further technical solution of the present invention is that the float valve adopts a mechanical water level control structure, and its highest liquid level limit point is lower than the safe liquid level at the top of the hot water storage tank.

[0017] A further technical solution of the present invention is that the hot water circulating pump is connected to the frequency converter, and the control system maintains a constant water supply pressure by controlling the output frequency of the frequency converter.

[0018] A control method for a variable-capacity air-source heat pump hot water supply system with energy storage function includes the following steps: S1. The controller has a preset time-of-use electricity price control parameter table, which includes the target water supply level Li (i=1, 2, ..., 24) for 24 time periods. Li is dynamically configured according to the time period electricity price category and historical water consumption data. The controller has preset parameters for the hot water storage tank, including: the maximum liquid level of the hot water storage tank Lmax, the protective liquid level of the hot water storage tank Lmin, and the liquid level hysteresis ΔL. The controller has preset temperature parameters, including: target water supply temperature Tg and temperature hysteresis ΔT; S2. The controller acquires in real time the hot water tank level L collected by the level sensor, the outlet water temperature T collected by the water supply temperature sensor, the outlet water pressure P collected by the water supply pressure sensor, the outdoor ambient temperature Ts collected by the outdoor temperature sensor, and the power curtailment status of the photovoltaic inverter obtained by the photovoltaic inverter communication interface. S3. The controller compares the real-time hot water tank level L with the current target water supply level Li, the hot water tank protection level Lmin, and the hot water tank protection level Lmin - level hysteresis ΔL; the controller compares the real-time outlet water temperature T with the target water supply temperature Tg and the target water supply temperature Tg - temperature hysteresis ΔT; and determines whether the photovoltaic inverter is in a state of power abandonment. S4. The controller controls the transitions of the supply system between shutdown, standby, heating, and water injection states. Its control logic includes: (a) In standby mode, when T < Tg - ΔT, the supply system is forced to enter the heating state; when T > Tg - ΔT and L < Lmin - ΔL, the supply system is forced to enter the water filling state; when T > Tg - ΔT and L > Lmin - ΔL, the standby mode is maintained. (b) In the water-filling state, when L≧Lmin, it enters the standby state; when L≦Lmin, it remains in the water-filling state. (c) Under heating conditions, when the photovoltaic inverter is in a state of power curtailment, the current time Li = Lmax is forcibly executed; when the photovoltaic inverter is in a state of non-power curtailment, the current time Li is obtained according to the data in the time-of-use electricity price control parameter table. When L < Lmin - ΔL, the forced supply system enters the water injection state; when L > Lmin - ΔL and T < Tg - ΔT, the solenoid valve is closed to maintain the heating state. When L > Lmin - ΔL, T > Tg - ΔT, and T < Tg, maintain the heating state; When T > Tg and L > Li, the supply system is forced into standby mode. When L < Li, the solenoid valve is opened to continue heating.

[0019] A further technical solution of the present invention is that the method for constructing the time-of-use electricity price control parameter table includes the following steps: S1.1. Obtain the peak, peak, flat, valley, and deep valley electricity price time period division data published by the power grid, and set the basic liquid level weight value Wi according to the peak, peak, flat, valley, and deep valley levels; S1.2. Calculate the water demand coefficient Pi (i=1, 2, ..., 24) for each time period based on the user's historical water consumption data. The value range is Pi∈ [-0.1, +0.1]. The historical water consumption for the current time period is Qi (i=1, 2, ..., 24), and the average daily water consumption is Qv. When Qi ≥ 1.2Qv, Pi = +0.1; When Qi ≤ 0.8Qv, Pi = -0.1; In all other cases, Pi = 0; S1.3. The target liquid level setpoint Li satisfies: Li = (W i + Pi)·Lmax; where 0.2Lmax≤Li≤0.95Lmax (protected liquid level).

[0020] A further technical solution of the present invention is that the criteria for judging the power curtailment state are: the photovoltaic inverter is in a "limited power operation" or "reduced operation" state; and the power curtailment state duration threshold t is ≥ 30 minutes.

[0021] A further technical solution of the present invention is that, in the shutdown state, when the outdoor ambient temperature Ts detected by the outdoor temperature sensor is ≤0℃ and the duration is more than 10 minutes, the antifreeze protection is activated, that is, the air source heat pump starts and the heat source circulation pump starts to heat the water in the hot water storage tank.

[0022] A further technical solution of the present invention is to compare the water supply pressure value detected by the water supply pressure sensor on the water-using side with the set target water supply pressure, and adjust the output frequency of the hot water circulation pump inverter through a PID algorithm.

[0023] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention realizes the energy storage and release process of the hot water system by adjusting the volume of hot water in the hot water storage tank. Energy storage is realized by controlling the increase of hot water volume; energy release is realized by controlling the decrease of hot water volume.

[0024] (2) It can automatically adjust energy storage and release strategies according to the changes in peak and valley electricity prices to achieve economic operation.

[0025] (3) It can be integrated with photovoltaic systems to replace battery energy storage. Based on the photovoltaic system's power generation, it automatically stores excess electrical energy, enabling timely utilization of green electricity. Compared to battery energy storage, it has advantages such as lower cost and higher safety.

[0026] (4) During the heat storage and release process, the volume of water changes while the temperature remains relatively constant, which solves the shortcomings of traditional sensible heat storage methods such as water heat storage, which have low heat storage density and temperature changes during the heat storage and release process.

[0027] (5) Compared with phase change thermal storage, it has the advantages of low cost and controllable temperature. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a structural diagram of the hot water supply system of the present invention; Figure 2 This is a flowchart illustrating the specific transitions between different operating states of the hot water supply system of the present invention. Figure 3 This is a flowchart showing the overall process of the hot water supply system of the present invention, including the various working states.

[0030] In the diagram: 1. Air source heat pump; 2. Heat source circulation pump; 3. Solenoid valve; 4. Float valve; 5. Hot water storage tank; 6. Hot water circulation pump; 7. Liquid level sensor; 8. Water supply temperature sensor; 9. Water supply pressure sensor; 10. Outdoor temperature sensor; 11. Controller; 12. Tap water side; 13. Water user side; 14. Photovoltaic inverter. Detailed Implementation

[0031] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0032] like Figure 1 As shown, this embodiment provides a variable volume air source heat pump hot water supply system with energy storage function, including an air source heat pump 1, a heat source circulation pump 2, a solenoid valve 3, a float valve 4, a hot water storage tank 5, a hot water circulation pump 6, a photovoltaic inverter 14, a controller 11, and a sensor module.

[0033] The sensor module includes a liquid level sensor 7, a water supply temperature sensor 8, a water supply pressure sensor 9, and an outdoor temperature sensor 10. A solenoid valve 3 and a float valve 4 are connected in series between the tap water side 12 and the hot water storage tank 5. The bottom of the hot water storage tank 5 is connected to an air source heat pump 1 via a heat source circulation pump 2. The air source heat pump 1 is connected to the heat source return port at the top of the hot water storage tank 5 to form a circulation loop. The bottom of the hot water storage tank 5 is also connected to the water use side 13 via a hot water circulation pump 6. The hot water circulation pump 6 is also connected to the top of the hot water storage tank 5 to form a circulation loop. The liquid level sensor 7 is installed inside the hot water storage tank 5 to detect the liquid level depth. The water supply temperature sensor 8 is installed between the hot water storage tank 5 and the hot water circulation pump 6 to detect the water supply temperature at the water use side 13. The water supply pressure sensor 9 is installed between the hot water circulation pump 6 and the water use side 13 to detect the water supply pressure at the water use side 13. The outdoor temperature sensor 10 is used to detect the outdoor ambient temperature.

[0034] The photovoltaic inverter 14, solenoid valve 3, air source heat pump 1, heat source circulation pump 2, hot water circulation pump 6, liquid level sensor 7, water supply temperature sensor 8, water supply pressure sensor 9, and outdoor temperature sensor 10 are all communicatively connected to the controller 11. The sensors are used to collect signals from each sensor and control the on / off state of the corresponding solenoid valve 3, air source heat pump 1, heat source circulation pump 2, and hot water circulation pump 6.

[0035] Through the above technical solution, the hot water storage tank 5 is an insulated open-type water tank with two pipes at the bottom, which are respectively connected to the heat source circulation pump 2 and the hot water circulation pump. The air source heat pump 1 uses electrical energy to absorb heat energy from the air and heat the water in the hot water storage tank 5. The water heated by the air source heat pump 1 is injected into the hot water storage tank 5 from the top of the tank. The hot water circulation pump is used to provide continuous hot water circulation to the water-using side 13. The water supply circulation flows through the water-using side 13 and is injected into the hot water storage tank 5 from the top of the tank. The photovoltaic system inverter has a communication interface. The air source heat pump 1 hot water system controller 11 can collect the inverter's operating status and determine whether the photovoltaic system is wasting electricity based on whether the inverter is in "limited power operation" or "diluted operation" state. When the air source heat pump 1 enters the heating state, the heat source circulation pump 2 needs to be turned on to circulate water between the air source heat pump and the hot water storage tank 5. The solenoid valve 3 is used to control the supply of tap water to the hot water storage tank 5, and the float valve 4 is used to prevent the water in the hot water storage tank 5 from overflowing due to continuous water supply. The liquid level sensor 7 is used to detect the liquid level depth in the hot water storage tank 5, and then calculate the volume of water in the hot water storage tank 5. The water supply temperature sensor 8 is used to detect the water supply temperature on the water-using side 13, which serves as the basis for system temperature regulation. The water supply pressure sensor 9 is used to detect the water supply pressure on the water-using side 13. The outdoor temperature sensor 10 is used to detect the outdoor ambient temperature, which is used to perform temperature compensation on the water supply temperature. The water supply temperature is adjusted according to the outdoor temperature to improve system comfort. The present invention can realize the system control function through the PLC controller 11 or other control circuits.

[0036] The present invention can realize the system control function through a PLC controller or other control circuits, which can be regarded as known technology and will not be described in detail. The following uses a PLC controller as an example.

[0037] The system collects the following input signals:

[0038] The system control output signals are as follows:

[0039] like Figure 2 As shown, a further technical solution of the present invention is that the supply system includes four working states: Stopped When the hot water circulation pump is turned off, the hot water supply to the water side 13 stops; when the solenoid valve 3 is closed, tap water will not automatically replenish the hot water storage tank 5. The air source heat pump 1 is activated by an antifreeze strategy inside it. If the air source heat pump 1 is activated, the heat source circulation pump 2 is activated to heat the water in the hot water storage tank 5. If the air source heat pump 1 is deactivated, the heat source circulation pump 2 is deactivated.

[0040] standby mode When the hot water circulation pump is turned on, hot water is supplied normally to the water side 13; when the solenoid valve 3 is closed, tap water will not be automatically replenished to the hot water storage tank 5. Air source heat pump 1 is turned off, and heat source circulation pump 2 is turned off.

[0041] Heating state The hot water circulation pump is turned on, and the water supply side 13 supplies hot water normally; the air source heat pump 1 is started, and the heat source circulation pump 2 is started to heat the water in the hot water storage tank 5; the solenoid valve 3 is opened to inject water according to the water temperature and liquid level, and the water supply temperature must be kept within the required range during the water injection process.

[0042] Water injection status The hot water circulation pump is turned off, and the water supply side 13 stops supplying hot water; the air source heat pump is turned off, and the heat source circulation pump 2 is turned off; the solenoid valve 3 is turned on, and under the action of tap water pressure, tap water is automatically replenished to the hot water storage tank 5 until the liquid level rises to the protection level and then the water injection stops.

[0043] It can switch between the four working states.

[0044] A further technical solution of the present invention is that the float valve 4 adopts a mechanical water level control structure, and its highest liquid level limit point is lower than the safe liquid level at the top of the hot water storage tank 5. The hot water circulation pump is connected to a frequency converter, and the control system maintains a constant water supply pressure by controlling the output frequency of the frequency converter.

[0045] like Figure 3 As shown, a control method for a hot water supply system of a variable volume air source heat pump 1 with energy storage function includes the following steps: S1. The controller 11 has a preset time-of-use electricity price control parameter table, which includes the target water supply level Li (i=1, 2, ..., 24) for 24 time periods. Li is dynamically configured according to the time period electricity price category and historical water consumption data. The controller 11 has preset parameters for the hot water storage tank 5, including: the maximum liquid level Lmax of the hot water storage tank 5, the protective liquid level Lmin of the hot water storage tank 5, and the liquid level hysteresis ΔL. The controller 11 has preset temperature parameters, including: target water supply temperature Tg and temperature hysteresis ΔT; S2. The controller 11 acquires in real time the liquid level L of the hot water storage tank 5 collected by the liquid level sensor 7, the outlet water temperature T collected by the water supply temperature sensor 8, the outlet water pressure P collected by the water supply pressure sensor 9, the outdoor ambient temperature Ts collected by the outdoor temperature sensor 10, and the power abandonment status of the photovoltaic inverter 14 obtained by the communication interface of the photovoltaic inverter 14. S3. The controller 11 compares the real-time collected hot water tank level L with the current target water supply level Li, the hot water tank protection level Lmin, and the hot water tank protection level Lmin - level hysteresis ΔL; the controller 11 compares the real-time collected outlet water temperature T with the target water supply temperature Tg and the target water supply temperature Tg - temperature hysteresis ΔT; and determines whether the photovoltaic inverter 14 is in a state of power abandonment. S4. Controller 11 controls the switching of the supply system between shutdown, standby, heating, and water injection states. Its control logic includes: (a) In standby mode, when T < Tg - ΔT, the supply system is forced to enter the heating state; when T > Tg - ΔT and L < Lmin - ΔL, the supply system is forced to enter the water filling state; when T > Tg - ΔT and L > Lmin - ΔL, the standby mode is maintained. (b) In the water-filling state, when L≧Lmin, it enters the standby state; when L≦Lmin, it remains in the water-filling state. (c) Under heating conditions, when the photovoltaic inverter 14 is in a state of power curtailment, the current time Li = Lmax is forcibly executed; when the photovoltaic inverter 14 is in a non-power curtailment state, the current time Li is obtained according to the data in the time-of-use electricity price control parameter table. When L < Lmin - ΔL, the forced supply system enters the water injection state; when L > Lmin - ΔL and T < Tg - ΔT, the solenoid valve 3 is closed to maintain the heating state. When L > Lmin - ΔL, T > Tg - ΔT, and T < Tg, maintain the heating state; When T > Tg and L > Li, the supply system is forced into standby mode. When L < Li, solenoid valve 3 is opened to continue heating.

[0046] In this embodiment, the set general parameter data are shown in the table below.

[0047] The method for constructing the time-of-use electricity price control parameter table includes the following steps: S1.1. Obtain the peak, peak, flat, valley, and deep valley electricity price time period data published by the power grid; Set the base liquid level weight value Wi, and its specific value is: During peak hours, Wi=0.3. During peak hours, Wi=0.4. During normal periods, Wi=0.6. During the valley period, Wi=0.8. During the deepest valley period, Wi=0.9; S1.2. Calculate the water demand coefficient Pi (i=1, 2, ..., 24) for each time period based on the user's historical water consumption data. The value range is Pi∈ [-0.1, +0.1]. The historical water consumption for the current time period is Qi (i=1, 2, ..., 24), and the average daily water consumption is Qv. When Qi ≥ 1.2Qv, Pi = +0.1; When Qi ≤ 0.8Qv, Pi = -0.1; In all other cases, Pi = 0; S1.3. The target liquid level setpoint Li satisfies: Li = (W i + Pi)·Lmax; where 0.2Lmax≤Li≤0.95Lmax (protected liquid level).

[0048] Peak-shaving parameters need to be set according to the time-of-use electricity period and price, and the time-of-use electricity price period varies from month to month. This plan is based on the hour, with one water supply level parameter set for each hour, for a total of 24 parameters.

[0049] In this example, the peak and off-peak time-of-use electricity pricing periods in a certain area during May are divided as follows:

[0050] Based on the above-mentioned time-of-use pricing period division and factors such as user water usage habits, the following peak-shaving parameters are set:

[0051] As time changes, the time-of-use electricity price changes, and the target water level also changes accordingly. If the target water supply level drops to the current level, the system will immediately switch to standby mode to avoid using electricity during peak hours.

[0052] A further technical solution of the present invention is that the criteria for judging the power curtailment state are: the photovoltaic inverter is in a "limited power operation" or "reduced operation" state; and the power curtailment state duration threshold t is ≥ 30 minutes.

[0053] When the unit is off, if the outdoor ambient temperature Ts detected by the outdoor temperature sensor is ≤0℃ and the duration is more than 10 minutes, the antifreeze protection will be activated, that is, the air source heat pump will start and the heat source circulation pump will start to heat the water in the hot water storage tank.

[0054] The water pressure P detected by the water supply pressure sensor on the water-using side is compared with the set target water supply pressure. The output frequency of the hot water circulation pump inverter is adjusted by the PID algorithm. The PID algorithm is existing technology and will not be described in this invention.

[0055] The control system and control method of this invention set different control strategies according to different times to realize the system's energy storage and release. During off-peak electricity prices or when there is a need to consume green electricity, the air source heat pump is controlled to start, and the water replenishment solenoid valve automatically replenishes water according to the water temperature, thereby increasing the hot water capacity; during peak electricity prices, the water replenishment solenoid valve is controlled to close, and the start and stop of the air source heat pump realizes water temperature control, resulting in a decrease in hot water volume after the user uses water.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A variable volume air source heat pump hot water supply system with energy storage function, characterized in that: The system includes an air source heat pump (1), a heat source circulation pump (2), a solenoid valve (3), a float valve (4), a hot water storage tank (5), a hot water circulation pump (6), a photovoltaic inverter (14), a controller (11), and a sensor module. The sensor module includes a liquid level sensor (7), a water supply temperature sensor (8), a water supply pressure sensor (9), and an outdoor temperature sensor (10). A solenoid valve (3) and a float valve (4) are connected in series between the tap water side (12) and the hot water storage tank (5). The bottom of the hot water storage tank (5) is connected to the air source heat pump (1) through the heat source circulation pump (2). The air source heat pump (1) is connected to the heat source return port at the top of the hot water storage tank (5) to form a circulation loop. The bottom of the hot water storage tank (5) is also connected to the water supply side (13) through the hot water circulation pump (6). The hot water circulation pump (6) is also connected to the top of the hot water storage tank (5) to form a circulation loop. The liquid level sensor (7) is installed in the hot water storage tank. The tank (5) is used to detect the liquid level depth in the hot water storage tank (5). The water supply temperature sensor (8) is set between the hot water storage tank (5) and the hot water circulation pump (6) to detect the water supply temperature on the water side (13). The water supply pressure sensor (9) is set between the hot water circulation pump (6) and the water side (13) to detect the water supply pressure on the water side (13). The outdoor temperature sensor (10) is used to detect the outdoor ambient temperature. The photovoltaic inverter (14), solenoid valve (3), air source heat pump (1), heat source circulation pump (2), hot water circulation pump (6), liquid level sensor (7), water supply temperature sensor (8), water supply pressure sensor (9) and outdoor temperature sensor (10) are all connected to the controller (11) for communication. The sensors are used to collect the signals of each sensor and control the operating status of the corresponding solenoid valve (3), air source heat pump (1), heat source circulation pump (2) and hot water circulation pump (6).

2. The variable volume air source heat pump hot water supply system with energy storage function according to claim 1, characterized in that: The supply system includes four operating states: Shutdown status The hot water circulation pump is turned off; Solenoid valve (3) is closed; if air source heat pump (1) is started, heat source circulation pump (2) is started to heat the water in the hot water storage tank (5); if air source heat pump (1) is closed, heat source circulation pump (2) is closed. standby mode Hot water circulation pump (6) is turned on; solenoid valve (3) is turned off; air source heat pump (1) is turned off; heat source circulation pump (2) is turned off. Heating state Hot water circulation pump (6) is turned on; air source heat pump (1) is started, heat source circulation pump (2) is started; determine whether to open solenoid valve (3) to inject water according to water temperature and liquid level; Water injection status Hot water circulation pump (6) is turned off; air source heat pump (1) is turned off; heat source circulation pump (2) is turned off; solenoid valve (3) is turned on.

3. A variable volume air source heat pump hot water supply system with energy storage function according to claim 2, characterized in that: The float valve (4) adopts a mechanical water level control structure.

4. A variable volume air source heat pump hot water supply system with energy storage function according to claim 3, characterized in that: The hot water circulating pump (6) is connected to the frequency converter, and the control system controls the output frequency of the frequency converter.

5. A control method for a variable volume air source heat pump hot water supply system with energy storage function, characterized in that, The control method of the supply system as described in claim 4 includes the following steps: S1. The controller (11) has a preset time-of-use electricity price control parameter table, including the target water supply level Li (i=1, 2, ..., 24) corresponding to 24 time periods, where Li is dynamically configured according to the time period electricity price category and historical water consumption data; The controller (11) has preset parameters for the hot water storage tank (5), including: the maximum liquid level of the hot water storage tank Lmax, the protective liquid level of the hot water storage tank Lmin, and the liquid level hysteresis ΔL; The controller (11) has preset temperature parameters, including: target water supply temperature Tg and temperature hysteresis ΔT; S2. The controller (11) acquires in real time the liquid level L of the hot water storage tank (5) collected by the liquid level sensor (7), the outlet water temperature T collected by the water supply temperature sensor (8), the outlet water pressure P collected by the water supply pressure sensor (9), the outdoor ambient temperature Ts collected by the outdoor temperature sensor (10), and the power abandonment status of the photovoltaic inverter (14) obtained by the communication interface of the photovoltaic inverter (14). S3. The controller (11) compares the real-time hot water tank level L with the current target water supply level Li, the hot water tank protection level Lmin, and the hot water tank protection level Lmin - level hysteresis ΔL; the controller (11) compares the real-time outlet water temperature T with the target water supply temperature Tg and the target water supply temperature Tg - temperature hysteresis ΔT; and determines whether the photovoltaic inverter (14) is in a state of power abandonment. S4. Controller (11) controls the switching of the supply system between shutdown state, standby state, heating state and water injection state. Its control logic includes: (a) In standby mode, when T < Tg - ΔT, the supply system is forced to enter the heating state; when T > Tg - ΔT and L < Lmin - ΔL, the supply system is forced to enter the water filling state; when T > Tg - ΔT and L > Lmin - ΔL, the standby mode is maintained. (b) In the water-filling state, when L≧Lmin, it enters the standby state; when L≦Lmin, it remains in the water-filling state. (c) Under heating conditions, when the photovoltaic inverter (14) is in a state of power curtailment, the current time Li = Lmax is forcibly executed; when the photovoltaic inverter (14) is in a non-power curtailment state, the current time Li is obtained according to the data in the time-of-use electricity price control parameter table. When L < Lmin - ΔL, the forced supply system enters the water injection state; when L > Lmin - ΔL and T < Tg - ΔT, the solenoid valve (3) is closed to maintain the heating state. When L > Lmin - ΔL, T > Tg - ΔT, and T < Tg, maintain the heating state; When T > Tg and L > Li, the supply system is forced into standby mode. When L < Li, the solenoid valve (3) is opened to continue heating.

6. The control method for a variable volume air source heat pump hot water supply system with energy storage function according to claim 5, characterized in that: The method for constructing the time-of-use electricity price control parameter table includes the following steps: S1.

1. Obtain the peak, peak, flat, valley, and deep valley electricity price time period division data published by the power grid, and set the basic liquid level weight value Wi according to the peak, peak, flat, valley, and deep valley levels; S1.

2. Calculate the water demand coefficient Pi (i=1, 2, ..., 24) for each time period based on the user's historical water consumption data. The value range is Pi∈ [-0.1, +0.1]. The historical water consumption for the current time period is Qi (i=1, 2, ..., 24), and the average daily water consumption is Qv. When Qi ≥ 1.2Qv, Pi = +0.1; When Qi ≤ 0.8Qv, Pi = -0.1; In all other cases, Pi = 0; S1.

3. The target liquid level setpoint Li satisfies: Li = (W i + Pi)·Lmax; where 0.2Lmax≤Li≤0.95Lmax.

7. The control method for a variable volume air source heat pump hot water supply system with energy storage function according to claim 5, characterized in that: The criteria for judging the state of power curtailment are: the photovoltaic inverter (14) is in the state of "limited power operation" or "reduced operation"; the duration threshold t of the power curtailment state is ≥30 minutes.

8. The control method for a variable volume air source heat pump hot water supply system with energy storage function according to claim 5, characterized in that: When the machine is stopped, if the outdoor ambient temperature Ts detected by the outdoor temperature sensor (10) is ≤0℃ and the duration is more than 10 min, the antifreeze protection is activated, that is, the air source heat pump (1) starts and the heat source circulation pump (2) starts to heat the water in the hot water storage tank (5).

9. The control method for a variable volume air source heat pump hot water supply system with energy storage function according to claim 5, characterized in that: The water pressure P detected by the water supply pressure sensor (9) on the water supply side (13) is compared with the set target water supply pressure, and the output frequency of the hot water circulation pump (6) is adjusted by the PID algorithm.

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