Defrosting decision method and device for photovoltaic photo-thermal heat pump system

Abstract

The present disclosure provides a defrosting decision method and device for a PVT heat pump system, and relates to the technical field of solar energy. The method comprises the following steps: obtaining frosting state data of a PVT component surface of the PVT heat pump system; taking the frosting state data as input of a first model to predict defrosting energy consumption and energy supply recovery time of the PVT heat pump system in the case of determining to perform a defrosting operation; obtaining an energy supply reduction amount of the PVT heat pump system in the case of determining not to perform the defrosting operation according to the energy supply recovery time; obtaining a defrosting cost of the PVT heat pump system in the case of determining to perform the defrosting operation according to the defrosting energy consumption and the energy supply recovery time; and determining to perform the defrosting operation of removing frost on the PVT component surface in the case that the difference between the energy supply reduction amount and the defrosting cost is greater than a preset value.

Description

Technical Field

[0001] This disclosure relates to the field of solar energy technology, and in particular to a defrosting decision method, apparatus and computer-readable storage medium for a photovoltaic / thermal (PVT) heat pump system. Background Technology

[0002] Driven by the "dual carbon" goal, the deep integration of photovoltaic power generation, solar thermal collection, and heat pump technology has become an important direction for solving the energy consumption problems of building heating, cooling, and domestic hot water. The PVT heat pump system integrates photovoltaic modules, solar thermal collectors, and heat pump units to simultaneously meet users' electricity and heat energy needs in the same system, achieving a high proportion of cascaded utilization of solar energy.

[0003] However, in the cold winter, PVT heat pump systems face the problem of frost formation. Frost forms on the surface of the PVT modules in the PVT heat pump system, reducing the amount of sunlight received by the PVT modules and thus affecting the power generation and heating efficiency of the PVT heat pump system.

[0004] In related technologies, a periodic defrosting strategy has been proposed to address the frosting problem in PVT heat pump systems. However, it was later found that the periodic defrosting strategy is difficult to adapt to dynamic operating conditions and can easily lead to energy waste. For example, when the defrosting node is set according to the cycle, even if the PVT components are not significantly affected by frosting or there is no frosting on the surface, the defrosting operation will still be triggered.

[0005] Furthermore, the related technology proposes a "frost-to-defrost" strategy, which determines whether to defrost based on the current frost state of the PVT module. For example, when the frost layer thickness on the surface of the PVT module reaches a certain threshold, it is determined to perform a defrost operation. Summary of the Invention

[0006] The inventors noted that defrosting strategies in related technologies may still lead to energy waste.

[0007] Specifically, if defrosting is determined solely by the degree of frost formation, a thick frost layer that meets the defrosting criteria often results in a higher additional energy consumption for defrosting. This could even lead to a situation where, for a period of time, the cost of defrosting (including at least the additional energy consumed) exceeds the energy reduction of the PVT heat pump system if defrosting is not performed. In this case, performing defrosting actually results in further energy waste compared to not performing it.

[0008] In view of this, the present disclosure proposes the following technical solution to accurately determine whether a defrosting operation needs to be performed on a PVT heat pump system from the perspective of saving energy as much as possible.

[0009] According to a first aspect of the present disclosure, a defrosting decision method for a PVT heat pump system is provided, comprising: acquiring frost state data on the surface of the PVT components of the PVT heat pump system; using the frost state data as input to a first model to predict the defrosting energy consumption and power supply recovery time of the PVT heat pump system when it is determined that a defrosting operation will be performed; acquiring, based on the power supply recovery time, an energy reduction of the PVT heat pump system when it is determined that a defrosting operation will not be performed; acquiring, based on the defrosting energy consumption and the power supply recovery time, a defrosting cost of the PVT heat pump system when it is determined that a defrosting operation will be performed; and determining to perform a defrosting operation to remove the frost layer on the surface of the PVT components when the difference between the energy reduction and the defrosting cost is greater than a preset value.

[0010] In some embodiments, obtaining frost status data on the surface of the PVT component of the PVT heat pump system includes: obtaining the power generation attenuation rate of the PVT heat pump system relative to the PVT component in a frost-free state based on the actual power generation of the PVT heat pump system, the surface irradiance of the PVT component, and the battery temperature; and using the power generation attenuation rate as input to a second model to predict the frost status data.

[0011] In some embodiments, obtaining the power generation attenuation rate of the PVT heat pump system relative to the PVT module in a frost-free state, based on the actual power generation of the PVT heat pump system, the surface irradiance of the PVT module, and the battery temperature, includes: obtaining a reference power generation of the PVT heat pump system when the PVT module is in a frost-free state, based on the surface irradiance and the battery temperature, wherein the reference power generation is positively correlated with the surface irradiance and negatively correlated with the battery temperature; and obtaining the power generation attenuation rate based on the actual power generation and the reference power generation.

[0012] In some embodiments, obtaining the reference power generation of the PVT heat pump system when the PVT module is in a frost-free state, based on the surface irradiance and the battery temperature, includes: obtaining the standard power generation of the PVT module under standard test conditions, the standard test conditions including standard temperature and standard irradiance; and calculating the reference power generation based on the standard power generation, the battery temperature, the standard temperature, the surface irradiance, and the standard irradiance.

[0013] In some embodiments, the input to the first model further includes at least one of historical defrost duration and defrost waiting time, wherein the historical defrost duration is obtained based on the time spent on the most recent n defrost operations of the PVT heat pump system, where n≥1, and the defrost waiting time is the interval between the start time of the defrost operation and the time required to collect the relevant data for the frosting status data.

[0014] In some embodiments, the energy reduction includes at least one of a first power generation reduction and a first heat generation reduction, wherein the first power generation reduction is positively correlated with a first difference and with the energy recovery time, and the first difference is the difference between the reference power generation of the PVT heat pump system and the actual power generation of the PVT heat pump system when the PVT module is in a frost-free state; the first heat generation reduction is positively correlated with a second difference and with the energy recovery time, wherein the second difference is the difference between the reference heat generation of the PVT heat pump system and the actual heat generation of the PVT heat pump system when the PVT module is in a frost-free state.

[0015] In some embodiments, the defrosting cost includes at least one of a second power generation reduction and a second heating reduction, and the defrosting energy consumption. The second power generation reduction is positively correlated with the reference power generation of the PVT heat pump system when the PVT modules are in a frost-free state and is also positively correlated with the energy recovery time. The second heating reduction is positively correlated with the reference heating power of the PVT heat pump system when the PVT modules are in a frost-free state and is also positively correlated with the energy recovery time.

[0016] In some embodiments, the second reduction in power generation is proportional to the reference power generation and the energy recovery time; the second reduction in heat supply is proportional to the reference heat supply and the energy recovery time.

[0017] In some embodiments, the preset value is a preset ratio of the defrosting energy consumption.

[0018] In some embodiments, the frosting status data includes at least the frost thickness, and / or the inputs to the first model further include one or more of the following: ambient temperature, ambient humidity, actual heating power of the PVT heat pump system, surface temperature of the PVT component, and compressor operating power, and / or the inputs to the second model further include one or more of the following: ambient temperature, ambient humidity, fin temperature of the air-cooled heat exchanger, evaporation pressure, compressor operating frequency, fan speed, and surface temperature of the PVT component.

[0019] According to a second aspect of the present disclosure, a defrosting decision device for a PVT heat pump system is provided, comprising: a memory; and a processor coupled to the memory, the processor being configured to execute the method of any of the above embodiments based on instructions stored in the memory.

[0020] According to a third aspect of the present disclosure, a PVT heat pump system is provided, including: a defrosting decision device according to any of the above embodiments.

[0021] According to a fourth aspect of the present disclosure, a computer-readable storage medium is provided, including computer program instructions, wherein the computer program instructions, when executed by a processor, implement the method of any of the above embodiments.

[0022] According to a fifth aspect of the present disclosure, a computer program product is provided, comprising a computer program, wherein the computer program, when executed by a processor, implements the method of any of the above embodiments. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this disclosure 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 this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of a defrosting decision method for a PVT heat pump system according to some embodiments of the present disclosure.

[0025] Figure 2 This is a schematic diagram illustrating the specific process of obtaining frosting status data according to some embodiments of this disclosure.

[0026] Figure 3 This is a schematic diagram illustrating the specific process for obtaining the power generation attenuation rate according to some embodiments of this disclosure.

[0027] Figure 4 This is a schematic diagram of the defrosting decision device of a PVT heat pump system according to some embodiments of the present disclosure.

[0028] Figure 5 This is a schematic diagram of the structure of a PVT heat pump system according to some embodiments of the present disclosure. Detailed Implementation

[0029] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0030] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this disclosure.

[0031] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0032] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0033] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0034] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0035] Figure 1 This is a schematic flowchart of a defrosting decision method for a PVT heat pump system according to some embodiments of the present disclosure.

[0036] like Figure 1 As shown, the defrosting decision method includes steps S10, S20, S30, S40 and S50.

[0037] In step S10, frosting status data of the PVT component surface of the PVT heat pump system is obtained.

[0038] In some embodiments, the frosting status data includes the frost thickness. As some implementations, the frosting status data may further include the frost growth rate.

[0039] In some embodiments, frost condition data can be obtained based on measurements. For example, a high-precision capacitive frost thickness sensor can be used to measure the frost thickness, and the ratio of the change in frost thickness between two adjacent measurements to the measurement time interval can be calculated to obtain the frost growth rate.

[0040] In other embodiments, machine learning models can be used to predict frost condition data on the surface of PVT components. For example, feature data of the PVT heat pump system can be used as input to the model to predict frost condition data.

[0041] In step S20, the frosting state data is used as input to the first model to predict the defrosting energy consumption and power recovery time of the PVT heat pump system when it is determined that a defrosting operation will be performed.

[0042] The first model could be, for example, a back propagation neural network (BPNN) model.

[0043] Defrosting energy consumption refers to the additional electrical energy consumed by a PVT heat pump system to perform defrosting operations. For example, the electrical energy consumed during the defrosting process can be measured using an electricity meter.

[0044] Power recovery time refers to the time from the start of defrosting to the completion of the defrosting operation, during which the power supply of the PVT heat pump system returns to a given power. It measures the duration of time the PVT heat pump system is affected by frost during defrosting. The given power can be, for example, a preset percentage of the PVT heat pump system's power supply before the start of defrosting, such as 90%.

[0045] Since PVT heat pump systems can generate electricity and provide heat simultaneously, the energy recovery time can be determined from at most the perspectives of power generation and heat supply.

[0046] For example, if only the impact of frost on power generation is considered, the power recovery time can be the time from the start of the defrosting operation to the completion of the defrosting operation when the power generation of the PVT heat pump system recovers to the given power generation.

[0047] Power generation can be measured using an electricity meter.

[0048] For example, if only the impact of frost on heating is considered, the power recovery time can be the time from the start of the defrosting operation to the completion of the defrosting operation when the heating power of the PVT heat pump system recovers to the given heating power.

[0049] The heating power Q can be calculated based on the temperature change of the hot water storage tank over a given time: Q = Cm(T2-T1) / t, where C is the specific heat capacity of water, m is the mass of the water being heated, T1 and T2 are the water temperatures measured at two different times, and t is the time interval between the two measurements. For example, if the hot water storage tank is fully loaded, the mass of the water being heated can be obtained by multiplying the density of the water by the volume of the tank. Alternatively, the mass of the water being heated in the tank can be measured using a flow meter.

[0050] For example, if we consider the impact of frost on both power generation and heating, the power recovery time can be the greater of the following: the time from the start of the defrosting operation to the completion of the defrosting operation when the PVT heat pump system's power generation returns to the given power generation, and the time from the start of the defrosting operation to the completion of the defrosting operation when the PVT heat pump system's heating power returns to the given heating power. In this case, the proportion of the given power generation to the total power generation of the PVT heat pump system before the start of the defrosting operation and the proportion of the given heating power to the total heating power of the PVT heat pump system before the start of the defrosting operation can be the same or different.

[0051] For example, if the impact of frost on both power generation and heating is considered, the power recovery time can be defined as the time from the start of the defrosting operation to the completion of the defrosting operation, during which the total power supply of the PVT heat pump system recovers to a given total power. Here, the total power supply is the sum of the power generation and heating power, and the given total power can be a preset proportion of the total power supply of the PVT heat pump system before the start of the defrosting operation.

[0052] In some embodiments, feature data related to the PVT heat pump system in multiple dimensions can be acquired periodically. This feature data may include, for example, power generation and the water temperature of the hot water storage tank used to calculate the heating power. For example, the feature data acquisition period is 30 seconds.

[0053] As some implementation methods, the multi-dimensional characteristic data of a PVT heat pump system may also include one or more of the following: ambient temperature, ambient humidity (e.g., relative humidity and / or absolute humidity), fin temperature of the air-cooled heat exchanger, surface temperature of the PVT module, cell temperature of the PVT module, evaporation pressure, compressor operating frequency, compressor operating power, and fan speed.

[0054] The aforementioned feature data can be used at various stages of the defrosting decision-making method, for example, as input to models (including the first model and the second model mentioned below). For example, the input to the first model may also include one or more of the following, such as ambient temperature, ambient humidity, actual heating power of the PVT heat pump system, surface temperature of the PVT components, and compressor operating power: all of these.

[0055] Furthermore, the defrosting decision-making method disclosed herein can be executed in every cycle. That is, in each cycle, it determines whether to defrost based on the current frost status data and the collected characteristic data. In this way, defrosting can be promptly determined and executed when it is necessary, avoiding excessive frost buildup.

[0056] During model training, a large amount of sample data needs to be collected, and each sample data contains feature data of one or more PVT heat pump systems. In some embodiments, if feature data is not successfully collected in a certain period, the average of the feature data from the previous period and the next period can be used as the feature data for that period. In some embodiments, if feature data is not successfully collected in multiple consecutive periods, the feature data for these multiple periods can be obtained based on the feature data collected in the periods on either side of these multiple periods, including but not limited to: directly using the feature data collected in a certain period as the feature data for the adjacent period (where feature data was not successfully collected) to fill the data gap; and the above-mentioned method of calculating the average.

[0057] In some embodiments, the Adam optimizer can be used during model training to adaptively adjust the learning rate, thereby accelerating model convergence while avoiding getting trapped in local optima.

[0058] In some embodiments, during the training and use of the model, to avoid large variations in the range of input sizes across different input layer nodes, the feature data of each input can be MIN-MAX normalized. The normalization boundary can use a preset value, or the maximum and minimum values ​​of measurements within a recent period (e.g., 24 hours).

[0059] In some embodiments, outlier data in the sample data can also be removed during model training. For example, if a feature in a sample is much larger or smaller than the average of the corresponding feature in all samples (e.g., the absolute value of the difference is greater than 3 times the standard deviation of the corresponding feature), then that sample is removed.

[0060] In some embodiments, the input to the first model may further include at least one of historical defrosting duration and defrosting waiting time, such as historical defrosting duration, defrosting waiting time, or both historical defrosting duration and defrosting waiting time.

[0061] Here, the historical defrosting time is obtained based on the time spent on the most recent n defrosting operations of the PVT heat pump system, where n≥1.

[0062] For example, when n=1, the historical defrost time is the time spent on the most recent defrost operation of the PVT heat pump system. Alternatively, when n>1, the historical defrost time is the average time spent on the most recent n defrost operations of the PVT heat pump system. The average can be calculated using either equal-weighted summation or unequal-weighted summation. When using unequal-weighted summation, the weight of the defrost operation more recent can be increased, thus making the historical waiting time more closely reflect the current actual operating conditions.

[0063] The defrosting waiting time is the interval between the start time of the defrosting operation and the time required to collect relevant data on the frost status.

[0064] For example, when frosting status data is obtained through measurement, the defrosting waiting time is the interval between the start time of the defrosting operation and the time when the frosting status data is collected. As another example, when certain characteristic data of a PVT heat pump system are measured, and then frosting status data is predicted using a model based on that characteristic data, the defrosting waiting time is the interval between the start time of the defrosting operation and the time when the characteristic data is collected.

[0065] Historical defrosting time can reflect the efficiency of a PVT heat pump system in performing defrosting operations to some extent. For example, if a PVT heat pump system has historically taken a long time to defrost, it may be due to low defrosting efficiency rather than a large frost layer thickness. In this case, the next defrosting operation may also take a long time, resulting in higher defrosting energy consumption and power recovery time. Therefore, using historical defrosting time as input to the first model can more accurately predict the defrosting energy consumption and power recovery time of the next defrosting operation.

[0066] Furthermore, defrost waiting time reflects the delay in defrost operation. A longer defrost waiting time indicates a later start to the defrost operation, potentially leading to a greater increase in frost thickness during the time preceding the operation. This can result in a longer defrost time for the next PVT heat pump system operation, resulting in higher defrost energy consumption and power recovery time. Therefore, using defrost waiting time as input to the first model can more accurately predict the defrost energy consumption and power recovery time for the next defrost operation.

[0067] Back Figure 1 In step S30, the amount of energy reduction of the PVT heat pump system when it is determined that defrosting operation will not be performed is obtained based on the energy recovery time.

[0068] Here, energy reduction refers to the energy reduction of the PVT heat pump system relative to the PVT modules in a frost-free state, within the energy recovery time if defrosting is not performed.

[0069] For example, assuming all other conditions remain unchanged (such as the characteristic data of the multiple dimensions related to the PVT heat pump system mentioned above), and the PVT modules are in a frost-free state, the energy supplied by the PVT heat pump system during the energy recovery time is x1. Assuming no defrosting operation is performed and the PVT modules are covered by frost, the energy supplied by the PVT heat pump system during the energy recovery time is y1. In this case, the energy reduction of the PVT heat pump system is x1 - y1.

[0070] In some embodiments, taking into account the impact of frost on power generation and / or heating, the reduction in energy supply may include at least one of a first reduction in power generation and a first reduction in heating.

[0071] In step S40, the defrosting cost of the PVT heat pump system is obtained based on the defrosting energy consumption and the power supply recovery time when it is determined that a defrosting operation will be performed.

[0072] Here, defrosting cost refers to the reduction in energy supply of the PVT heat pump system relative to the PVT components in a frost-free state, within the energy recovery time, if a defrosting operation is performed, as well as the defrosting energy consumption for performing the defrosting operation.

[0073] For example, assuming all other conditions remain unchanged (such as the aforementioned characteristic data related to the PVT heat pump system across multiple dimensions), and the PVT modules are in a frost-free state, the energy supplied by the PVT heat pump system during the energy recovery time is x2. Assuming a defrosting operation is performed, the frost thickness on the PVT module surface gradually decreases; in this case, the energy supplied by the PVT heat pump system during the energy recovery time is y2. The energy reduction of the PVT heat pump system in this situation is x2 - y2. Assuming the defrosting energy consumption is z, the defrosting cost of the PVT heat pump system is x2 - y2 + z.

[0074] In some embodiments, taking into account the impact of frost on power generation and / or heating, defrosting costs may include at least one of a second power generation reduction and a second heating reduction (both being the energy reduction during defrosting) and defrosting energy consumption.

[0075] The specific steps for obtaining the energy reduction when not defrosting and the cost of defrosting will be explained below.

[0076] In step S50, if the difference between the energy reduction and the defrosting cost is greater than a preset value, it is determined that a defrosting operation to remove the frost layer on the surface of the PVT module will be performed.

[0077] In some embodiments, the preset value is equal to 0. In this case, a defrosting operation is determined to be performed when the energy reduction without defrosting exceeds the cost of defrosting.

[0078] In other embodiments, the preset value is greater than 0. Since the defrosting energy consumption predicted by the first model may fluctuate relative to the actual defrosting energy consumption, resulting in fluctuations in defrosting costs, setting the preset value to be greater than 0 can prevent defrosting decisions from frequently changing due to fluctuations in defrosting costs.

[0079] As one implementation method, the preset value is a preset proportion of the defrosting energy consumption predicted by the first model. The preset proportion can be determined based on the prediction uncertainty of the first model, for example, 10%. In this way, the adverse impact of the prediction fluctuation of the first model on the defrosting decision can be reduced.

[0080] In some other embodiments, the preset value is less than 0. In this case, the probability of performing the defrosting operation can be appropriately increased to minimize the possibility of the PVT components being covered by frost.

[0081] This provides a defrosting decision-making method for PVT heat pump systems. This method does not directly determine whether to perform defrosting based on frost status data, but rather fully considers both the adverse effects of not performing defrosting (i.e., the energy reduction of the PVT heat pump system) and the adverse effects of performing defrosting (i.e., the cost of defrosting). Defrosting is only performed when the adverse effects of not performing defrosting significantly outweigh those of performing it. Conversely, if the adverse effects of performing defrosting are greater, it is not performed. The defrosting decisions made by this method can save more energy for the PVT heat pump system.

[0082] In some embodiments, the defrosting operation can be completed when the fin temperature of the air-cooled radiator in the PVT heat pump system reaches a set temperature (e.g., 5 degrees Celsius) and / or the defrosting time reaches a preset time (e.g., 3 minutes).

[0083] In some embodiments, the accuracy of the first model's predictions of defrost energy consumption and power recovery time may decrease as operating conditions drift. In such cases, the first model can be updated based on actual data from the most recent defrost operation. For example, the first model can be updated when the actual defrost energy consumption of a defrost operation deviates significantly from the prediction (e.g., greater than 15%), and / or the actual power recovery time deviates significantly from the prediction (e.g., greater than 2 minutes).

[0084] One implementation approach is to fine-tune the first model by freezing the weights of all layers except the output layer and training only the weights of the output layer. This can improve the model's update efficiency.

[0085] The following section explains the specific steps for obtaining frosting status data.

[0086] Figure 2 This is a schematic diagram illustrating the specific process of obtaining frosting status data according to some embodiments of this disclosure.

[0087] like Figure 2 As shown, step S10, which involves obtaining frosting status data, further includes steps S101 and S102.

[0088] In step S101, the power generation attenuation rate of the PVT heat pump system relative to the PVT module under frost-free conditions is obtained based on the actual power generation of the PVT heat pump system, the surface irradiance of the PVT module, and the battery temperature.

[0089] The surface irradiance of the PVT component can be measured using an irradiometer.

[0090] The battery temperature of a PVT module can be measured by a temperature sensor placed on the backplane of the PVT module. Generally, due to the limitations of battery power generation and heat dissipation, the battery temperature of a PVT module will be slightly higher than the surface temperature. In some embodiments, the surface temperature of the PVT module can be used as an approximation for the battery temperature of the PVT module.

[0091] In step S102, the power generation attenuation rate is used as the input of the second model to predict the frosting status data.

[0092] The second model can be the BPNN model.

[0093] In related technologies, when using models to predict frost condition data, discrete feature data such as the actual power generation of the PVT heat pump system, the surface irradiance of the PVT modules, and the battery temperature are often directly input into the model to predict the frost condition data of the PVT modules. On the one hand, this increases the number of input nodes in the model, thus increasing the structural complexity of the model. On the other hand, the individual correlation between these feature data and the frost condition data is weak, making it difficult for the model to accurately learn the correlation between each feature data and the frost condition data, resulting in unsatisfactory model training performance and poor prediction accuracy.

[0094] In the above embodiment for obtaining frosting status data, the actual power generation of the PVT heat pump system, the surface irradiance of the PVT modules, and the battery temperature are integrated into a new feature—the power generation degradation rate. This feature directly characterizes the degradation of power generation efficiency caused by frosting in the PVT heat pump system and has a strong correlation with the frosting status data. Therefore, using the power generation degradation rate as the core criterion for predicting frosting status data can reduce the structural complexity of the second model, improve its computational efficiency, and enhance the accuracy of the second model in predicting frosting status data.

[0095] In some embodiments, the inputs to the second model may further include one or more, such as all, of the following: ambient temperature, ambient humidity, fin temperature of the air-cooled heat exchanger, evaporation pressure, compressor operating frequency, fan speed, and surface temperature of the PVT components. Thus, the second model can more accurately predict frosting status data.

[0096] In some embodiments, the input to the second model may also include the output of the second model from the previous period, i.e., the frosting state data. In this way, the second model can predict the frosting state data of the current period based on the frosting state data of the previous period, forming a self-closing loop and further improving the accuracy of the prediction.

[0097] Figure 3This is a schematic diagram illustrating the specific process for obtaining the power generation attenuation rate according to some embodiments of this disclosure.

[0098] like Figure 3 As shown, step S101, which obtains the power generation attenuation rate, further includes steps S1011 and S1012.

[0099] In step S1011, the reference power generation of the PVT heat pump system under frost-free conditions is obtained based on the surface irradiance of the PVT module and the battery temperature. Here, the reference power generation is positively correlated with the surface irradiance and negatively correlated with the battery temperature.

[0100] In some embodiments, the power generation of the PVT module under specific conditions can be used as a benchmark, and the reference power generation of the PVT heat pump system under frost-free conditions can be calculated based on the theory of solar photovoltaic power generation (the higher the surface irradiance, the higher the power generation; the higher the cell temperature, the lower the power generation). The accuracy of the reference power generation obtained in this way is relatively high.

[0101] Specifically, the standard power generation of the PVT module under standard test conditions can be obtained, where the standard test conditions include standard temperature and standard irradiance; and the reference power generation of the PVT heat pump system under frost-free conditions can be calculated based on the standard power generation, battery temperature, standard temperature, surface irradiance, and standard irradiance.

[0102] As some implementation methods, it is possible to base P refer =P stc ·(G pvt / G stc )·[1+γ·(T cell -T stc )] Calculate the reference power generation P refer .

[0103] P stc This refers to the standard power generation of a PVT module under standard test conditions. For example, the P value can be obtained from the PVT module manufacturer's datasheet. stc .

[0104] T cell T represents the cell temperature of the PVT module. stc For example, the standard temperature is 25 degrees Celsius.

[0105] T cell T represents the surface irradiance of the PVT module. stc The standard irradiance is, for example, 1000 W / m². 2 .

[0106] γ is the power-temperature degradation coefficient of a solar cell, characterizing the percentage decrease in power generation for every degree Celsius increase in actual temperature relative to standard temperature. γ is negative; for example, for crystalline silicon solar cells, γ is -0.38% / K.

[0107] In step S1012, the power generation attenuation rate is obtained based on the actual power generation and the reference power generation.

[0108] For example, the power generation attenuation rate η=(P refer -P cur ) / P refer , where P cur This represents the actual power generation.

[0109] The following section explains how to obtain the energy reduction of the PVT heat pump system when defrosting is not performed.

[0110] In some embodiments, when it is determined that defrosting is not performed, the reduction in power generation of the PVT heat pump system (hereinafter referred to as the first reduction in power generation) is positively correlated with the first difference and positively correlated with the power recovery time of the PVT heat pump system.

[0111] Here, the first difference is the difference between the reference power generation of the PVT heat pump system and the actual power generation of the PVT heat pump system when the PVT modules are in a frost-free state. The reference power generation can be obtained according to the method described above.

[0112] As one of the ways to achieve this, the first reduction in power generation J E For reference power generation P refer Compared with actual power generation P cur The first difference and the power recovery time t rec The product of: J E =(P refer -P cur )·t rec That is, during the time when the power supply is restored, it is approximately assumed that the reference power generation and the actual power generation of the PVT heat pump system remain unchanged.

[0113] As some other implementation methods, the first reduction in power generation J E For: J E =k E ·d·t rec , where k E Here, k represents the power generation loss coefficient based on frost thickness, where d is the frost layer thickness. For example, in situations where a defrosting decision-making method is used periodically to determine whether defrosting should be performed, a moving window weighted average can be used to calculate k. E :k E =λ·k E_ins +(1-λ)·kE_old , where k E_ins Calculate k for the current period E The median value, k E_ins =(P refer -P cur ) / d,k E_old The power generation-thickness loss coefficient for the previous cycle is given by λ, which is a smoothing factor, for example, λ is set to 0.15. For example, in the first cycle, k... E =(P refer -P cur ) / d.

[0114] In some embodiments, when it is determined that defrosting is not performed, the heat reduction of the PVT heat pump system (hereinafter referred to as the first heat reduction) is positively correlated with the second difference and with the energy recovery time of the PVT heat pump system.

[0115] Here, the second difference is the difference between the reference heating power of the PVT heat pump system and the actual heating power of the PVT heat pump system when the PVT components are in a frost-free state.

[0116] The first reduction in heat supply can be calculated using a method similar to that used to calculate the first reduction in power generation.

[0117] As one of the ways to achieve this, the first reduction in heating supply J Q For reference heating power Q refer With actual heating power Q cur The second difference and the energy recovery time t rec The product of: J Q =(Q refer -Q cur )·t rec That is, during the time when the power supply is restored, it is approximately assumed that the reference heating power and the actual heating power of the PVT heat pump system remain unchanged.

[0118] As some other implementation methods, the first heating reduction J Q For: J Q =k Q ·d·t rec , where k Q Here, k is the heating power-thickness loss coefficient, and d is the frost thickness. For example, in situations where a defrosting decision-making method is used periodically to determine whether defrosting should be performed, a moving window weighted average can be used to calculate k. Q :k Q =λ·k Q_ins +(1-λ)·k Q_old , where k Q_ins Calculate k for the current period Q The median value, k Q_ins =(Qrefer -Q cur ) / d,k Q_old Let λ be the heating power-thickness loss coefficient for the previous cycle, and λ be a smoothing factor. For example, the smoothing factor related to heating and the smoothing factor related to power generation can have the same or different values. For example, in the first cycle, k Q =(Q refer -Q cur ) / d.

[0119] In the above embodiments for obtaining the reduction in energy supply, for power generation and / or heating, the difference between the reference energy supply power and the actual energy supply power is used as the main basis for calculating the reduction in energy supply. This can make the reduction in energy supply closer to the true value, especially when the reference energy supply power and the actual energy supply power of the PVT heat pump system do not change drastically.

[0120] In some embodiments, the heating reference power Q refer The weighted average obtained by moving windows, as described above, can be used similarly, where Q is calculated in the current period. refer The median value can be the average of the actual heating power over the most recent several cycles, and the smoothing factor can be, for example, 0.2.

[0121] The following section explains the defrosting cost of a PVT heat pump system when a defrosting operation is determined to be performed.

[0122] In some embodiments, when it is determined that a defrosting operation is to be performed, the power generation reduction of the PVT heat pump system (hereinafter referred to as the second power generation reduction) is positively correlated with the reference power generation of the PVT heat pump system when the PVT components are in a frost-free state and is also positively correlated with the power supply recovery time.

[0123] As one of the ways to achieve this, the second reduction in power generation J defrost_E Compared with the reference power generation P refer It is directly proportional to and related to the energy recovery time t rec Proportional: J defrost_E =α·P refer ·t rec Where α is the recovery period loss ratio coefficient related to power generation, reflecting the proportion of power generation lost relative to the reference power generation during the power supply recovery period. For example, α can be taken as 0.3-0.5, such as 0.4.

[0124] In some embodiments, when it is determined that a defrosting operation is to be performed, the heat reduction of the PVT heat pump system (hereinafter referred to as the second heat reduction) is positively correlated with the reference heat power of the PVT heat pump system when the PVT components are in a frost-free state and is also positively correlated with the energy recovery time.

[0125] The second reduction in heating can be calculated using a method similar to that used to calculate the second reduction in power generation.

[0126] As one of the implementation methods, the second heating reduction J defrost_Q With reference heating power Q refer It is directly proportional to and related to the energy recovery time t rec Proportional: J defrost_Q =β·Q refer ·t rec Where β is the recovery period loss ratio coefficient related to heating supply, reflecting the proportion of heating power missing relative to the reference heating power during the energy recovery period. The values ​​of β and α can be the same or different.

[0127] Based on the calculation of the second reduction in power generation and / or the second reduction in heat supply, and adding the defrosting energy consumption predicted by the first model, the defrosting cost of the PVT heat pump system under the condition that defrosting operation is performed can be obtained.

[0128] This disclosure also provides a defrosting decision device for a PVT heat pump system.

[0129] Figure 4 This is a schematic diagram of the defrosting decision device of a PVT heat pump system according to some embodiments of the present disclosure.

[0130] like Figure 4 As shown, the defrosting decision device 400 of the PVT heat pump system includes a memory 401 and a processor 402 coupled to the memory 401. The processor 402 is configured to execute the defrosting decision method of any of the above embodiments based on the instructions stored in the memory 401.

[0131] The memory 401 may include, for example, system memory, fixed non-volatile storage media, etc. The system memory may store, for example, an operating system, application programs, a boot loader, and other programs.

[0132] In some embodiments, the defrosting decision device 400 of the PVT heat pump system may further include an input / output interface 403, a network interface 404, and a storage interface 405. These interfaces 403, 404, and 405, as well as the memory 401 and processor 402, can be connected, for example, via a bus 406. The input / output interface 403 provides a connection interface for input / output devices such as a monitor, mouse, keyboard, and touchscreen. The network interface 404 provides a connection interface for various networked devices. The storage interface 405 provides a connection interface for external storage devices such as SD cards and USB flash drives.

[0133] This disclosure also provides a PVT heat pump system, including the defrosting decision device of any of the above embodiments.

[0134] Figure 5 This is a schematic diagram of the structure of a PVT heat pump system according to some embodiments of the present disclosure.

[0135] like Figure 5 As shown, the PVT heat pump system includes a defrosting decision device (not shown), a PVT water circulation loop, and a refrigerant loop.

[0136] In normal heating mode (i.e., without defrosting), in the PVT water circulation loop, the antifreeze absorbs heat below the PVT components and, driven by the circulation pump, flows through a three-way valve to the plate heat exchanger, finally returning to the bottom of the PVT components to complete the circulation. The plate heat exchanger transfers the heat from the antifreeze to the refrigerant in the refrigerant loop.

[0137] In the refrigerant circuit, the refrigerant flows through the electronic expansion valve to the air-cooled heat exchanger and the plate heat exchanger, where it absorbs heat. It then flows through the four-way valve to the compressor, where it is compressed into high-temperature and high-pressure vapor. After that, it flows through the four-way valve to the water-side heat exchanger, where it releases heat to the water in the hot water storage tank to provide heating to the room. Finally, it flows to the electronic expansion valve to complete the cycle.

[0138] During the defrosting process, in the PVT water circulation loop, after absorbing heat below the PVT components, the antifreeze no longer flows to the plate heat exchanger to exchange heat with the refrigerant. Instead, it flows directly to the indoor terminal heat dissipation device to directly heat the room.

[0139] In the refrigerant circuit, the four-way valve switches to reverse the flow of refrigerant. The high-temperature and high-pressure vapor formed by the compressor's additional power consumption flows in the opposite direction to the air-cooled heat exchanger and plate heat exchanger to dissipate heat and melt the frost on the surface of the PVT components.

[0140] In some embodiments, the PVT heat pump system may also include various measuring instruments (such as temperature sensors, humidity sensors, DC meters, evaporation pressure sensors, water temperature sensors, etc.) to collect the various characteristic data of the PVT heat pump system described above.

[0141] This disclosure also provides a computer-readable storage medium including computer program instructions that, when executed by a processor, implement the defrosting decision method of any of the above embodiments.

[0142] This disclosure also provides a computer program product, including a computer program that, when executed by a processor, implements the defrosting decision method of any of the above embodiments.

[0143] The embodiments of this disclosure have now been described in detail. To avoid obscuring the concept of this disclosure, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0144] Those skilled in the art will understand that embodiments of this disclosure can be provided as methods, systems, or computer program products. Therefore, this disclosure can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this disclosure can take the form of a computer program product embodied on one or more computer-usable non-transitory storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0145] This disclosure is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It should be understood that the functions specified in one or more flowchart illustrations and / or one or more block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate functions for implementing the functions in the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0146] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0147] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0148] While specific embodiments of this disclosure have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A defrosting decision method for a photovoltaic thermal (PVT) heat pump system, comprising: Acquire the frosting status data on the surface of the PVT components of the PVT heat pump system; The frosting state data is used as input to the first model to predict the defrosting energy consumption and power recovery time of the PVT heat pump system when a defrosting operation is determined to be performed. Based on the energy recovery time, obtain the energy reduction of the PVT heat pump system when it is determined that defrosting operation will not be performed; Based on the defrosting energy consumption and the power supply recovery time, obtain the defrosting cost of the PVT heat pump system when it is determined that a defrosting operation will be performed. If the difference between the energy reduction and the defrosting cost is greater than a preset value, it is determined that a defrosting operation to remove the frost layer on the surface of the PVT component will be performed.

2. The method according to claim 1, wherein, Obtaining the frosting status data on the surface of the PVT components of the PVT heat pump system includes: Based on the actual power generation of the PVT heat pump system, the surface irradiance of the PVT module, and the battery temperature, the power generation attenuation rate of the PVT heat pump system relative to the PVT module in a frost-free state is obtained. The power generation attenuation rate is used as input to the second model to predict the frosting state data.

3. The method according to claim 2, wherein, Based on the actual power generation of the PVT heat pump system, the surface irradiance of the PVT module, and the battery temperature, the power generation attenuation rate of the PVT heat pump system relative to the PVT module under frost-free conditions is obtained, including: Based on the surface irradiance and the battery temperature, the reference power generation of the PVT heat pump system is obtained when the PVT module is in a frost-free state, wherein the reference power generation is positively correlated with the surface irradiance and negatively correlated with the battery temperature; The power generation attenuation rate is obtained based on the actual power generation and the reference power generation.

4. The method according to claim 3, wherein, Based on the surface irradiance and the battery temperature, the reference power generation of the PVT heat pump system when the PVT module is in a frost-free state includes: Obtain the standard power generation of the PVT module under standard test conditions, including standard temperature and standard irradiance; The reference power generation is calculated based on the standard power generation, the battery temperature, the standard temperature, the surface irradiance, and the standard irradiance.

5. The method according to any one of claims 1-4, wherein, The input to the first model also includes at least one of historical defrosting duration and defrosting waiting time. The historical defrosting time is obtained based on the time spent on the most recent n defrosting operations of the PVT heat pump system, where n≥1. The defrosting waiting time is the interval between the start time of the defrosting operation and the time required to collect the relevant data for the frost status data.

6. The method according to any one of claims 1-4, wherein, The reduction in energy supply includes at least one of a first reduction in power generation and a first reduction in heat supply. The first reduction in power generation is positively correlated with the first difference and also positively correlated with the energy recovery time. The first difference is the difference between the reference power generation of the PVT heat pump system and the actual power generation of the PVT heat pump system when the PVT module is in a frost-free state. The first reduction in heat supply is positively correlated with the second difference and also positively correlated with the energy recovery time. The second difference is the difference between the reference heat supply power of the PVT heat pump system and the actual heat supply power of the PVT heat pump system when the PVT component is in a frost-free state.

7. The method according to any one of claims 1-4, wherein, The defrosting cost includes at least one of the second reduction in power generation and the second reduction in heating, plus the defrosting energy consumption. The second reduction in power generation is positively correlated with the reference power generation of the PVT heat pump system when the PVT module is in a frost-free state, and is also positively correlated with the energy recovery time. The second reduction in heat supply is positively correlated with the reference heat supply power of the PVT heat pump system when the PVT component is in a frost-free state, and is also positively correlated with the energy recovery time.

8. The method according to claim 7, wherein, The second reduction in power generation is proportional to the reference power generation and also proportional to the power supply recovery time. The second reduction in heating is proportional to the reference heating power and the energy recovery time.

9. The method according to any one of claims 1-4, wherein, The preset value is a preset ratio of the defrosting energy consumption.

10. The method according to any one of claims 1-4, wherein, The frosting status data includes at least the frost thickness, and / or The inputs to the first model also include one or more of the following: ambient temperature, ambient humidity, actual heating power of the PVT heat pump system, surface temperature of the PVT components, and compressor operating power, and / or The inputs to the second model also include one or more of the following: ambient temperature, ambient humidity, fin temperature of the air-cooled heat exchanger, evaporation pressure, compressor operating frequency, fan speed, and surface temperature of the PVT component.

11. A defrosting decision device for a photovoltaic thermal (PVT) heat pump system, comprising: Memory; as well as A processor coupled to the memory is configured to execute the method of any one of claims 1-10 based on instructions stored in the memory.

12. A photovoltaic thermal (PVT) heat pump system, comprising: The defrosting decision device according to claim 11.

13. A computer-readable storage medium comprising computer program instructions, wherein, When the computer program instructions are executed by the processor, they implement the method described in any one of claims 1-10.

14. A computer program product comprising a computer program, wherein, When the computer program is executed by a processor, it implements the method described in any one of claims 1-10.

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