A method for monitoring snowmelt on a photovoltaic module

Abstract

The application discloses a photovoltaic module snow melting monitoring method, and belongs to the technical field of melting monitoring, in particular to a photovoltaic module snow melting monitoring method. The application provides a photovoltaic module snow melting monitoring method. In order to achieve the above object, the application adopts the following technical scheme, and the photovoltaic module snow melting monitoring method comprises the following steps: a photovoltaic power generation circuit is composed of one photovoltaic module, one relay and one load resistor; the photovoltaic module faces the south direction, and the inclination angle of the photovoltaic module is determined according to monitoring requirements; the relay controls the opening and closing of the electric circuit; the rated power of the load resistor is P r , and the resistance value is R r ; the two parameters are selected according to the following conditions: (1) P r >P f (2) (U f / I f )<R r <1.5 (U f / I f ), wherein P f is the peak power of the photovoltaic module, U f is the peak voltage of the photovoltaic module, and I f is the peak current of the photovoltaic module.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of thawing monitoring, and particularly relates to a snow thawing monitoring method for a photovoltaic module. BACKGROUND

[0002] In the cold northern region, some residents, especially rural residents, cannot access the heating website, and heating in winter becomes a problem, so they have to use burning straw, burning coal, and electric heating to keep warm. Among these methods, burning straw and burning coal are serious air pollution, and electric heating is high in cost. A clean energy heating method with low use cost is needed to solve the current problem. Therefore, a snow thawing monitoring method for a photovoltaic module is needed. SUMMARY

[0003] The application is aimed at the above problems, and provides a snow thawing monitoring method for a photovoltaic module.

[0004] To achieve the above purpose, the application adopts the following technical scheme, and the application is a snow thawing monitoring method for a photovoltaic module, comprising the following steps:

[0005] The photovoltaic power generation circuit is composed of one photovoltaic module, one relay, and one load resistor; the photovoltaic module faces the south direction, and the inclination angle of the photovoltaic module is determined according to the monitoring requirement; the relay controls the opening and closing of the electric circuit; and the rated power of the load resistor is P r , and the resistance value is R r . The two parameters are selected according to the following conditions.

[0006] (1) P r >P f

[0007] (2) (U f / I f )<R r <1.5 (U f / I f )

[0008] Wherein, P f is the peak power of the photovoltaic module, U f is the peak voltage of the photovoltaic module, and I f is the peak current of the photovoltaic module.

[0009] The monitoring circuit is composed of a microcontroller circuit, a wireless communication circuit, a keyboard and liquid crystal display circuit, a voltage detection circuit, a current detection circuit, a module backboard temperature detection circuit, an irradiation intensity detection circuit, and a relay control circuit.

[0010] The microcontroller circuit is the core circuit of the monitoring system, responsible for data acquisition, calculation and real-time control of the system, composed of CPU and peripheral circuit. The CPU can be selected from high-speed single-chip microcomputer, DSP, ARM and other chips. The working frequency of the CPU should be above 30 MHz.

[0011] The wireless communication circuit is used to realize real-time control of the system through remote terminal equipment (including mobile phones, tablets and the like) and online viewing of real-time working status and historical faults of the system, real-time data and historical data of various physical quantities;

[0012] The keyboard and liquid crystal display circuit are used to realize setting of some physical parameters of the system and real-time display of the working status of the system;

[0013] The voltage detection circuit is used to detect the voltage across the load resistor;

[0014] The current detection circuit is used to detect the current through the load resistor;

[0015] The irradiance detection circuit is used to detect the solar irradiance;

[0016] The relay control circuit is used to control the opening and closing of the relay;

[0017] The component backsheet temperature detection circuit is used to detect the backsheet temperature of the photovoltaic module;

[0018] The component backsheet temperature sensor is installed at the center of the back of the photovoltaic module;

[0019] The actual output power P of the photovoltaic module is continuously detected re The calculated output power P of the photovoltaic module is obtained through the solar irradiance, backsheet temperature of the module and other parameters ca The actual output power P of the photovoltaic module is continuously detected re The calculated output power P of the photovoltaic module is obtained through the solar irradiance, backsheet temperature of the module and other parameters ca The actual output power P of the photovoltaic module is continuously detected re The calculated output power P of the photovoltaic module is obtained through the solar irradiance, backsheet temperature of the module and other parameters ca

[0020] The calculation process is as follows, wherein P ca is the calculated output power of the photovoltaic module, P st is the rated output power of the photovoltaic module under standard test conditions, P re is the actual output power of the photovoltaic module, T a is the actual temperature of the photovoltaic cell inside the photovoltaic module, T b is the actual temperature of the backsheet of the photovoltaic module, T st is the temperature under standard test conditions, δ is the power temperature variation coefficient of the photovoltaic module, K is the comprehensive influence coefficient, R a is the actual irradiance on the surface of the photovoltaic module, R st is the irradiance under standard test conditions, U r is the voltage of the load resistor, and I rThe current of the load resistor;

[0021] In the formula, R st = 1000 W / m 2 , T st = 25℃, P st , and δ are provided by the photovoltaic module manufacturer according to different types of photovoltaic modules.

[0022]

[0023] P re = U r × I r

[0024] When P re > 0.95P ca , the actual output power of the photovoltaic module is very close to the calculated output power value, and the power generation capacity of the photovoltaic module is close to or reaches the power generation capacity in the normal state, so it can be determined that the snow on the surface of the photovoltaic module has melted.

[0025] As a preferred solution, the two parameters T a and K need to be determined by a special calculation method, as described below.

[0026] (1) Calculation method of T a

[0027] Because the photovoltaic cell is very thin and fragile and cannot be used directly outdoors, an encapsulation shell needs to be added to the front and rear surfaces to improve its strength. The upper surface is a high-transparency tempered glass, and the lower surface is a high-strength insulating back plate. The photovoltaic cell is bonded between the upper and lower surfaces by a hot melt adhesive film, which is the usual internal structure of a photovoltaic module. In the past, the coefficient multiplied when calculating the influence of temperature changes on the output power of a photovoltaic module was [1+δ×(T b -T st )], where the back plate temperature T b of the photovoltaic module in this coefficient is not the actual temperature T a of the photovoltaic cell inside the photovoltaic module. Currently, there is no method to directly detect the temperature of the photovoltaic cell inside the photovoltaic module in photovoltaic power generation projects. The temperature of the photovoltaic cell inside the photovoltaic module is usually approximated by the temperature of the back plate of the photovoltaic module in the past calculations. However, this is inaccurate because the hot melt adhesive film and high-strength insulating back plate separate the temperature sensor installed on the back plate of the photovoltaic module from the photovoltaic cell inside the photovoltaic module. Therefore, the actual temperature T a of the photovoltaic cell is higher than the back plate temperature T b of the photovoltaic module, and the difference between these two temperature values is related to the actual irradiance R a ​changes; the coefficient multiplied in the algorithm when calculating the influence of temperature change on the output power of photovoltaic module is [1+δ×(T a -T st )], the actual temperature of photovoltaic cell inside the photovoltaic module can be calculated from the backboard temperature of the module and the actual irradiance according to the following formula; the theoretical output power value of the photovoltaic module calculated in this way is more accurate than that of previous algorithms;

[0028]

[0029] In the formula, T ch is the difference between the temperature of photovoltaic cell inside the photovoltaic module under standard test conditions and the backboard temperature of the module, T ch =2.5℃, R st =1000W / m 2 ;

[0030] (2) Calculation method of K

[0031] The comprehensive influence coefficient K includes the influence of dust on the surface of the module, the influence of the attenuation of photoelectric conversion efficiency of the module with the increase of use time, and the influence of power loss caused by wires, relays, and wiring terminals in the electrical circuit; since the sizes of these influence factors change slowly over time, and the change law is difficult to quantify with a function expression, a fixed empirical value is usually used to calculate the power generation of the photovoltaic system, but it has a great influence on the accuracy of the calculation results; the K value is calculated inversely according to the real-time data such as actual power generation of the photovoltaic module in the present application, and the size of the K value is dynamically adjusted at regular intervals on this basis, so as to improve the accuracy of the calculation results;

[0032] At each integral point in time, and under the conditions that R a >100W / m 2 and P re >0.1P st , the K value is calculated according to the following formula, which is used as the K value in the calculation of P a in the above formula between the integral point in time when the conditions R 2 >100W / m re and P st >0.1P ca are met and the next integral point in time when the conditions are met again; when the calculation conditions are met again, a new K value is calculated to replace the old one, so as to realize dynamic adjustment according to actual data;

[0033]

[0034] Method for calculating snow melting energy efficiency of air source heat pump on photovoltaic system

[0035] The application provides a calculation method of air source heat pump snow melting energy efficiency of a photovoltaic system, and the calculation process is as follows.

[0036]

[0037]

[0038] E j =E i -E r

[0039]

[0040] In the above formula, t z is the time consumed by natural snow melting of the surface of the photovoltaic module, t j is the time consumed by the air source heat pump system for melting snow on the surface of the photovoltaic module, E r is the power consumption of the air source heat pump system in the process of melting snow on the photovoltaic module, E i is the power generation of the photovoltaic system generated after the air source heat pump system melts snow on the photovoltaic module, E j is the net increase of the whole system generated by the air source heat pump snow melting compared with natural snow melting, K cop is the energy efficiency ratio of the air source heat pump system for melting snow, E k (t) is a function of the power consumption of the air source heat pump with time, E f (t) is a function of the power consumption of the auxiliary equipment (including a water pump, a solenoid valve and the like) with time, E p (t) is a function of the power generation of the photovoltaic system with time.

[0041] If E j > 0, it indicates that the power generation of the photovoltaic system increased by the air source heat pump system for melting snow is greater than the power consumption of the air source heat pump system in the process of melting snow; if E j = 0, it indicates that the power generation of the photovoltaic system increased by the air source heat pump system for melting snow is equal to the power consumption of the air source heat pump system in the process of melting snow; if E j < 0, it indicates that the power generation of the photovoltaic system increased by the air source heat pump system for melting snow is less than the power consumption of the air source heat pump system in the process of melting snow.

[0042] K cop > 1, the air source heat pump snow melting mode is effective for increasing the net increase of the system electric energy, and the greater the value is, the more significant the effect is. cop

[0043] K cop ​When =1, the power consumption of the air source heat pump snow melting mode is equal to the power generation of the photovoltaic system increased by snow melting, and at this time, the selection of the air source heat pump snow melting mode or the natural snow melting mode of the photovoltaic module has the same influence on the net energy of the whole system;

[0044] K cop When <1, the power consumption of the air source heat pump snow melting mode is too much, which exceeds the power generation of the photovoltaic system increased after snow melting, and at this time, the natural snow melting mode of the photovoltaic module should be selected.

[0045] Advantages of the present application.

[0046] The photovoltaic module surface snow no longer continues to generate electricity, and can only restore power generation after the snow melts. Since the melting speed of the snow is affected by many factors such as temperature, humidity, wind speed, wind direction, irradiation intensity, photovoltaic module inclination and the like, it is difficult to calculate the accurate time. At present, there is a lack of a simple and effective monitoring method for the snow melting of the photovoltaic module. The present application provides a snow melting monitoring method for the photovoltaic module, which can accurately judge whether the snow on the surface of the photovoltaic module melts through a simple photovoltaic system and a monitoring system, and cooperates with a corresponding calculation method. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 Principle diagram of the snow melting monitoring system for the photovoltaic module.

[0048] Figure 2 Principle diagram of the snow melting controller.

[0049] Figure 3 System control program flow chart.

[0050] Figure 4 Principle diagram of the super-low-temperature air source heat pump heating + photovoltaic power generation multi-energy coupling type energy system.

[0051] Figure 5 "Eye" type snow melting pipe on the back of the photovoltaic module.

[0052] Figure 6 Cross-sectional view of the semicircular steel pipe and the semicircular polyurethane heat preservation pipe shell.

[0053] Figure 7 "Eye" type snow melting pipe on the back of the photovoltaic module.

[0054] Figure 8 Cross-sectional view of the semicircular steel pipe and the semicircular polyurethane heat preservation pipe shell.

[0055] Figure 9 Connection diagram of the snow melting pipe on the back of the photovoltaic module. DETAILED DESCRIPTION

[0056] The photovoltaic module snow melting monitoring method of the application can be applied to a multi-energy coupling energy system. Figure 4 As shown in the figure, the multi-energy coupling energy system comprises a photovoltaic array, a grid-connected inverter, an ultra-low temperature air source heat pump, an auxiliary electrical device, a No. 1-8 electromagnetic valve, a circulating water pump 1, a circulating water pump 2, a heating water tank, a snow melting water tank, the photovoltaic array is connected with the power grid, the power supply port of the ultra-low temperature air source heat pump and the power supply port of the auxiliary electrical device through the grid-connected inverter, the outlet of the ultra-low temperature air source heat pump is connected with one end of the No. 5 electromagnetic valve and one end of the No. 7 electromagnetic valve, the other end of the No. 5 electromagnetic valve is connected with the inlet of the snow melting water distributor, and the outlet of the snow melting water distributor is connected with the photovoltaic module back plate pipeline.

[0057] The other end of the No. 7 electromagnetic valve is connected with the inlet of the heating water distributor and one end of the No. 8 electromagnetic valve, and the outlet of the heating water distributor is connected with the heating terminal pipeline through the heating electromagnetic valve.

[0058] The inlet of the ultra-low temperature air source heat pump is connected with one end of the No. 6 electromagnetic valve and the outlet of the circulating water pump 2, the other end of the No. 6 electromagnetic valve is connected with the outlet of the circulating water pump 1 and the other end of the No. 8 electromagnetic valve, the inlet of the circulating water pump 1 is connected with the outlet of the heating water tank, the inlet of the heating water tank is connected with the outlet of the heating water collector, and the inlet of the heating water collector is connected with the heating terminal return pipeline.

[0059] The inlet of the circulating water pump 2 is connected with the outlet of the snow melting water tank, the inlet of the snow melting water tank is connected with the outlet of the snow melting water collector, and the inlet of the snow melting water collector is connected with the photovoltaic module back plate return pipeline.

[0060] The system uses the ultra-low temperature air source heat pump to provide heating for the cold northern region, and the photovoltaic power generation system generates electricity to solve all or part of the energy consumption of the ultra-low temperature air source heat pump during the day, thereby greatly reducing the electricity cost of the air source heat pump.

[0061] Due to the snow in winter, the power generation of the photovoltaic array is greatly reduced, and when the photovoltaic array surface has snow, the heat energy generated by the ultra-low temperature air source heat pump is used to dissipate heat through the circulating pipeline arranged on the photovoltaic module back plate to melt the snow of the photovoltaic array, thereby improving the power generation of the photovoltaic system and realizing the functions of heating and snow melting of the photovoltaic array by using one heat pump.

[0062] The outlet of the heating water distributor is four-way, and the heating electromagnetic valve comprises a No. 1 electromagnetic valve, a No. 2 electromagnetic valve, a No. 3 electromagnetic valve and a No. 4 electromagnetic valve.

[0063] The circulating water pump 1 and the circulating water pump 2 adopt a low-noise pipeline shield pump, the rated flow of the shield pump should be greater than 1.2 l / s, and the internal motor insulation level of the shield pump needs to reach H level.

[0064] The 1-8 electromagnetic valves are all two-position two-way electromagnetic valves, wherein the 1-4, 6 and 7 electromagnetic valves are normally open type, and the 5 and 8 electromagnetic valves are normally closed type. The 1-4 electromagnetic valves can have a 20 mm diameter, and the 5-8 electromagnetic valves can have a 25 mm diameter.

[0065] The antifreeze used in the system can be replaced every 5 years, and the freezing point of the antifreeze should be 5℃ lower than the lowest temperature in winter in the location of the system.

[0066] The pipes between the heating water distributor and the heating terminal and the pipes between the heating terminal and the heating water collector all use polyvinyl chloride pipes. The inner diameter of the pipes can be 20 mm.

[0067] The pipes between the snow melting water distributor and the backboard of the photovoltaic module and the pipes between the backboard of the photovoltaic module and the snow melting water collector all use round steel pipes. The inner diameter of the steel pipes can be 15 mm. The remaining pipes in the system can all use polyvinyl chloride pipes, and the inner diameter of the pipes can be 25 mm.

[0068] The heating water tank is installed indoors, so that the heating water tank is isolated from the cold atmosphere, reducing heat loss to reduce energy consumption. The electric heater in the heating water tank is installed at the bottom of the heating water tank, and the electric heater is fully immersed in the antifreeze in all working modes. The electric heater is used to heat to maintain the temperature of the fluid inside the heating circulation system when the system needs to realize both snow melting and heating functions.

[0069] The parameters of the heating water tank are as follows:

[0070] 0.7V g ≦V1≦0.9V g

[0071] V1=V pg +V rg

[0072] V yg ≧0.03

[0073] S / 40≦P g ≦(S / 40+1)

[0074] Wherein, V g is the volume of the heating water tank (unit m 3 ), V1 is the volume of the antifreeze stored in the heating water tank when the heating system is not working (unit m 3 ). V pg is the sum of the internal volumes of each pipe in the heating circulation pipe (unit m 3 ), V yg is the antifreeze allowance of the heating circulation system (unit m 3 ), P gThe power of the electric heater in the heating water tank (unit: kW), S is the building area of the heating house (unit: m 2 ).

[0075] The snow-melting water tank is installed underground, so that the snow-melting water tank is isolated from the cold atmosphere. The upper surface of the snow-melting water tank is lower than the depth of the frozen soil layer at the site of the system, so that the antifreeze in the snow-melting water tank maintains a higher temperature.

[0076] The parameters of the snow-melting water tank are as follows:

[0077] 0.7V r ≦V2≦0.9V r

[0078] V2=V br +V pr +V yr

[0079] V yr ≧0.03

[0080] H r >H d

[0081] Wherein, V r is the volume of the snow-melting water tank (unit: m 3 ), V2 is the volume of the antifreeze stored in the snow-melting water tank when the snow-melting system is not working (unit: m 3 ). V br is the sum of the internal volumes of all the backboard snow-melting pipelines of the photovoltaic modules (unit: m 3 ), V pr is the sum of the internal volumes of all the pipelines in the snow-melting circulation system except the backboard snow-melting pipelines of the photovoltaic modules (unit: m 3 ), and V yr is the antifreeze allowance of the snow-melting circulation system (unit: m 3 ). H r is the vertical distance from the upper surface of the snow-melting water tank to the ground (unit: m), and H d is the depth of the frozen soil layer at the site of the system (unit: m).

[0082] The pipeline surface of the backboard of the photovoltaic module is covered with a polyurethane heat preservation pipe shell, and the snow-melting water tank is placed underground to reduce the heat loss of the snow-melting system. Since the use environment is in the cold northern region, the circulating medium in all the pipelines and the water tank is antifreeze, and the antifreeze temperature should be lower than the annual minimum temperature at the site of the system by more than 5 degrees Celsius.

[0083] The working modes of the system include the following five modes.

[0084] Mode 1: Normal heating mode. In this mode, the circulating water pump 1 is started, the circulating water pump 2 is turned off, the 1-4th, 6th and 7th solenoid valves are not powered (corresponding to the pipeline being open), the 5th and 8th solenoid valves are not powered (corresponding to the pipeline being closed). In this working mode, the snow melting circulating system does not work, and there is no liquid circulation in the corresponding pipeline. The hot fluid after the air source heat pump heating supplies all the heating terminal pipelines.

[0085] Mode 2: Energy-saving heating mode. In this mode, the circulating water pump 1 is started, the circulating water pump 2 is turned off, the 6th and 7th solenoid valves are not powered (corresponding to the pipeline being open), the 5th and 8th solenoid valves are not powered (corresponding to the pipeline being closed). Part of the 1-4th solenoid valves are not powered (corresponding to the pipeline being open), and the other part is powered (corresponding to the pipeline being closed). In this working mode, the snow melting circulating system does not work, and there is no liquid circulation in the corresponding pipeline. The hot fluid after the air source heat pump heating selectively supplies the heating terminal pipelines of the 1-4th solenoid valves that are not powered, so as to reduce the heating load and reduce energy consumption.

[0086] Mode 3: Snow melting mode. In this mode, the circulating water pump 2 is started, the circulating water pump 1 is turned off, the 1-4th solenoid valves are not powered (corresponding to the pipeline being open), the 6th and 7th solenoid valves are powered (corresponding to the pipeline being closed), the 5th solenoid valve is powered (corresponding to the pipeline being open), and the 8th solenoid valve is not powered (corresponding to the pipeline being closed). In this working mode, the heating circulating system does not work, and there is no liquid circulation in the corresponding pipeline. The snow melting circulating system works, and the hot fluid after the air source heat pump heating supplies the photovoltaic module backboard pipeline.

[0087] Mode 4: Snow melting + normal heating mode. In this mode, the circulating water pump 1 and the circulating water pump 2 are started, the 5th and 8th solenoid valves are powered (corresponding to the pipeline being open), the 6th and 7th solenoid valves are powered (corresponding to the pipeline being closed), the 1-4th solenoid valves are not powered (corresponding to the pipeline being open), and the electric heater in the heating water tank starts to work. In this working mode, the snow melting circulating system works, and the hot fluid after the air source heat pump heating supplies the photovoltaic module backboard pipeline. The heating circulating system also works, and the hot fluid after the electric heater heating supplies all the heating terminal pipelines.

[0088] Mode 5: Snow melting + energy-saving heating mode. In this mode, the circulating water pump 1 and the circulating water pump 2 are started, the 5th and 8th solenoid valves are powered (corresponding to the pipeline being open), and the 6th and 7th solenoid valves are powered (corresponding to the pipeline being closed). Part of the 1-4th solenoid valves are not powered (corresponding to the pipeline being open), and the other part is powered (corresponding to the pipeline being closed), and the electric heater in the heating water tank starts to work. In this working mode, the snow melting circulating system works, and the hot fluid after the air source heat pump heating supplies the photovoltaic module backboard pipeline. The heating circulating system also works, and the hot fluid after the electric heater heating selectively supplies the heating terminal pipelines of the 1-4th solenoid valves that are not powered, so as to reduce the heating load and reduce energy consumption.

[0089] AsFigure 5 As shown in the drawings, the middle part of the back of the photovoltaic module is provided with a "eye" type snow melting pipeline, the outside of the snow melting pipeline is covered with a heat preservation pipe shell, and a space is left between the snow melting pipeline and the heat preservation pipe shell.

[0090] The water inlet and outlet of the snow melting pipeline are arranged on the diagonal side, and the snow melting pipelines of the photovoltaic modules are connected in series.

[0091] The cross section of the snow melting pipeline is a semicircular frame, and the cross section of the heat preservation pipe shell is a semicircular ring.

[0092] The snow melting pipeline is made of steel pipe.

[0093] The heat preservation pipe shell is made of polyurethane heat preservation pipe shell.

[0094] The "eye" type snow melting pipeline on the back of the photovoltaic module is as shown in the drawings. Figure 5 Figure 5 h is the length of the photovoltaic module (unit: mm), w is the width of the photovoltaic module (unit: mm), m is the distance between the center lines of the steel pipes of the uppermost and lowermost horizontal snow melting pipelines (unit: mm), n is the distance between the center lines of the steel pipes of the left and right vertical snow melting pipelines (unit: mm), g is the distance between the center lines of the steel pipes of the left and right vertical snow melting pipelines and the side edges of the photovoltaic module (unit: mm), f is the distance between the center lines of the steel pipes of the uppermost and lowermost horizontal snow melting pipelines and the side edges of the photovoltaic module (unit: mm), and k is the width of the semicircular polyurethane heat preservation pipe shell (unit: mm).

[0095] Figure 6 b is the outer circle radius of the semicircular steel pipe (unit: mm), c is the pipe wall thickness of the semicircular steel pipe (unit: mm), d is the inner hole radius of the semicircular polyurethane heat preservation pipe shell (unit: mm), and e is the pipe wall thickness of the semicircular polyurethane heat preservation pipe shell (unit: mm).

[0096] The parameter design principles are as follows:

[0097] m = 0.75h

[0098] n = 0.5w

[0099] f = 0.125h

[0100] g = 0.25w

[0101] 1mm ≦ c ≦ 3mm

[0102] 30mm ≦ e ≦ 60mm

[0103] d ≧ (b + 2mm)

[0104] k = 2d + 2e

[0105] ​The back of the photovoltaic module is arranged with a "eye" type snow melting pipe, which can make the snow melting speed of each part of the photovoltaic module more uniform. The pipe uses a semicircular frame-shaped steel pipe to increase the heat conduction contact area between the pipe and the back plate of the photovoltaic module, thereby improving the snow melting effect. A semicircular ring-shaped polyurethane heat preservation pipe shell is installed outside the steel pipe to reduce the heat loss caused by the heat conduction to the surrounding environment.

[0106] Taking a photovoltaic module with model LR5-72HPH-550M produced by Longji Le Ye Photovoltaic Technology Co., Ltd. as an example, the length of the module is 2256mm, and the width is 1133mm. The back plate of the photovoltaic module is designed and installed with a "eye" type snow melting pipe, and the size is as shown in Figure 7 The cross-sectional view of the semicircular steel pipe and the semicircular polyurethane heat preservation pipe shell is as shown in Figure 8 .

[0107] The back of the photovoltaic module is arranged with a "eye" type snow melting pipe, which can make the snow melting speed of each part of the photovoltaic module more uniform. The pipe uses a semicircular frame-shaped steel pipe to increase the heat conduction contact area between the pipe and the back plate of the photovoltaic module, thereby improving the snow melting effect. A semicircular ring-shaped polyurethane heat preservation pipe shell is installed outside the steel pipe to reduce the heat loss caused by the heat conduction to the surrounding environment. Figure 9 The back of the photovoltaic module is arranged with a "eye" type snow melting pipe, which can make the snow melting speed of each part of the photovoltaic module more uniform. The pipe uses a semicircular frame-shaped steel pipe to increase the heat conduction contact area between the pipe and the back plate of the photovoltaic module, thereby improving the snow melting effect. A semicircular ring-shaped polyurethane heat preservation pipe shell is installed outside the steel pipe to reduce the heat loss caused by the heat conduction to the surrounding environment.

[0108] The back of the photovoltaic module is arranged with a "eye" type snow melting pipe, which can make the snow melting speed of each part of the photovoltaic module more uniform. The pipe uses a semicircular frame-shaped steel pipe to increase the heat conduction contact area between the pipe and the back plate of the photovoltaic module, thereby improving the snow melting effect. A semicircular ring-shaped polyurethane heat preservation pipe shell is installed outside the steel pipe to reduce the heat loss caused by the heat conduction to the surrounding environment. Figure 2 The back of the photovoltaic module is arranged with a "eye" type snow melting pipe, which can make the snow melting speed of each part of the photovoltaic module more uniform. The pipe uses a semicircular frame-shaped steel pipe to increase the heat conduction contact area between the pipe and the back plate of the photovoltaic module, thereby improving the snow melting effect. A semicircular ring-shaped polyurethane heat preservation pipe shell is installed outside the steel pipe to reduce the heat loss caused by the heat conduction to the surrounding environment.

[0109] Real-time control of the system through a remote terminal device (including mobile phones, tablets, etc.) is achieved through a wireless communication circuit, and the system's real-time working status and historical faults, real-time data and historical data of various physical quantities are viewed online.

[0110] Setting of some physical parameters of the system through a keyboard and liquid crystal display circuit, and real-time display of the working mode of the system.

[0111] Real-time monitoring of the working status and various physical parameters of the grid-connected inverter and air source heat pump through the 485 communication circuit.

[0112] The voltage range of the analog signal emitted by the temperature sensor is adjusted to the voltage range that the microcontroller can receive through the temperature signal conditioning circuit, and the analog signal is converted into a digital signal for calculation through the AD module inside the microcontroller.

[0113] The voltage range of the analog signal emitted by the irradiation sensor is adjusted to the voltage range that the microcontroller can receive through the irradiation signal conditioning circuit, and the analog signal is converted into a digital signal for calculation through the AD module inside the microcontroller.

[0114] The voltage range of the analog signal emitted by the liquid level sensor is adjusted to the voltage range that the microcontroller can receive through the liquid level signal conditioning circuit, and the analog signal is converted into a digital signal for calculation through the AD module inside the microcontroller.

[0115] The switching quantity control circuit controls the switching of the relay through optical coupling isolation method to control the strong current equipment in the system.

[0116] The microcontroller circuit is the core circuit of the controller, responsible for data acquisition, calculation and real-time control of the system, composed of CPU and peripheral circuits. The CPU can be selected from high-speed single-chip microcomputer, DSP, ARM chip, etc. The working frequency of the CPU should be above 70MHz.

[0117] Among them, the indoor temperature sensor is installed in the heated house, the distance from the ground is 1.2m, and the distance from the south wall and north wall is the midpoint in the north-south direction. The backplane temperature sensor of the assembly is installed at the center of the back of the photovoltaic assembly, away from the snow melting pipe of the assembly backplane. The irradiation sensor is installed near the outdoor photovoltaic assembly, and the irradiation sensor cannot be shaded. The liquid level sensor is installed in the heating water tank and snow melting water tank respectively. The objects controlled by the switching quantity control circuit include circulating water pump 1, circulating water pump 2, electromagnetic valve 1-8, and electric heater in the heating water tank.

[0118] The system control program flow chart is as follows Figure 3The system starts to work, first, the keyboard is used to set various physical parameters, it is judged whether the two water tanks in the system need to be supplemented with anti-freezing liquid, then the system is controlled to enter the corresponding working mode according to the instruction issued by the owner, if there is no new instruction, the system is kept in the regular heating mode or the energy-saving heating mode set last time. When the system enters the regular heating mode, it is first judged whether the indoor temperature exceeds the set temperature, if not, the air source heat pump is started, and the related electromagnetic valves and water pumps are controlled according to mode 1; if yes, the air source heat pump is turned off, and the related electromagnetic valves and water pumps are kept in the original working state. When the system enters the energy-saving heating mode, the control flow is the same as that of the regular heating mode, but the related electromagnetic valves and water pumps work according to mode 2. When the system enters the snow melting mode, the air source heat pump is first started, the related electromagnetic valves and water pumps are controlled according to mode 3, the calculated output power of the photovoltaic power station is calculated according to parameters such as irradiance, if the calculated output power is greater than the actual output power, the cycle waiting is entered; if the calculated output power is less than the actual output power, the snow melting mode is stopped, and the owner is informed through wireless communication. When the system enters the snow melting + regular heating mode, the air source heat pump is first started, the related electromagnetic valves and water pumps are controlled according to mode 4, it is judged whether the indoor temperature exceeds the set temperature, if not, the electric heater is started, if yes, the electric heater is turned off, and the related electromagnetic valves and water pumps are kept in the original working state, then the calculated output power of the photovoltaic power station is calculated according to parameters such as irradiance, if the calculated output power is greater than the actual output power, the cycle waiting is entered; if the calculated output power is less than the actual output power, the snow melting + regular heating mode is ended, and the owner is informed through wireless communication, if the owner has no instruction, the system continues to work according to the regular heating mode. When the system enters the snow melting + energy-saving heating mode, the control flow is the same as that of the snow melting + regular heating mode, but the related electromagnetic valves and water pumps work according to mode 5.

[0119] Carbon emission reduction calculation method of the system

[0120] Step 1) The power consumption mode of the system in the heating mode includes the following three kinds every day.

[0121] (1) Power consumption mode 1: the photovoltaic power generation system does not generate electricity at night or in bad weather, and the power consumption of the air source heat pump is completely provided by the power grid, the energy saving amount of the system in this time period is calculated as follows.

[0122]

[0123] (2) Power consumption mode 2: in the case that the solar irradiance is low during the day, the power generation of the photovoltaic power generation system is less than the power consumption of the system, the power generated by the photovoltaic power generation system is completely consumed by the air source heat pump, part of the power consumption of the air source heat pump is provided by the photovoltaic power generation system, and the insufficient power consumption is provided by the power grid.

[0124]

[0125] (3) Electric power mode 3: When the solar radiation intensity is high during the day, the power generation of the photovoltaic power generation system is greater than the power consumption of the system, and the power consumption of the system is completely provided by the photovoltaic power generation system. In addition to the power generated by the photovoltaic power generation system being used by the air source heat pump, the extra power is used by other loads or transmitted to the power grid.

[0126]

[0127] Wherein, t1+t2+t3=24

[0128] The carbon emission reduction amount of the system per day in the heating mode is calculated as follows.

[0129] C r1 =K e ×(S1+S2+S3)

[0130] In the above formula, Q k (t) is a function of the air source heat pump heating capacity changing with time, E k (t) is a function of the air source heat pump power consumption changing with time, E f (t) is a function of the auxiliary equipment (including water pump, solenoid valve, etc.) power consumption changing with time, E p (t) is a function of the photovoltaic system power generation changing with time, S1 is the energy saving amount of the system in electric power mode 1, t1 is the working hours of the system per day in electric power mode 1, S2 is the energy saving amount of the system in electric power mode 2, t2 is the working hours of the system per day in electric power mode 2, S3 is the energy saving amount of the system in electric power mode 3, t3 is the working hours of the system per day in electric power mode 3, C r1 is the carbon emission reduction amount of the system per day in the heating mode, K e is the proportion coefficient of carbon emission and electric energy.

[0131] Step 2) In the snow melting or snow melting + heating mode, the photovoltaic system does not generate electricity due to snow cover, and the system is completely in power consumption state. The carbon emission of the system per day in the snow melting or snow melting + heating mode is calculated as follows.

[0132]

[0133] In the above formula, E d (t) is a function of the electric heater power consumption changing with time, E d (t) is zero when the system is in snow melting mode, and E d (t) is not zero when the system is in snow melting + heating mode. W is the carbon emission of the system per day in the snow melting or snow melting + heating mode.

[0134] Step 3) In the non-heating season, the air source heat pump and auxiliary equipment do not work, no energy consumption is generated, and the photovoltaic power generation system generates electricity to realize carbon emission reduction. The daily carbon emission reduction of the system in the non-heating season is calculated as follows.

[0135]

[0136] In the above formula, C r2 is the daily carbon emission reduction of the system in the non-heating season.

[0137] Step 4) The annual carbon emission reduction of the system is calculated as follows.

[0138] C ry = T1xC r1 + T2xC r2 - T3xW

[0139] Wherein, T1+T2+T3=365

[0140] In the above formula, C ry is the annual carbon emission reduction of the system, T1 is the number of days the system operates in the heating mode, T2 is the number of days the system operates in the non-heating season, and T3 is the number of days the system operates in the snow melting or snow melting + heating mode.

[0141] The present application is a photovoltaic module snow melting monitoring method

[0142] After the surface snow of the photovoltaic module stops generating electricity, it can only restore power generation after the snow melts. Because the melting speed of the snow is affected by many factors such as temperature, humidity, wind speed, wind direction, irradiation intensity, and photovoltaic module inclination, it is difficult to calculate the accurate time. At present, there is a lack of a simple and effective monitoring method for the snow melting of the photovoltaic module. The present application provides a photovoltaic module snow melting monitoring method, which can accurately determine whether the surface snow of the photovoltaic module melts through a simple photovoltaic system and a monitoring system, and a corresponding calculation method.

[0143] The schematic diagram of the photovoltaic module snow melting monitoring system is shown in Figure 1 , which is composed of a photovoltaic power generation circuit and a monitoring circuit. The photovoltaic power generation circuit is composed of one photovoltaic module, one relay, and one load resistor. The photovoltaic module faces the south direction, and the inclination angle of the photovoltaic module is determined according to the monitoring needs. The relay controls the opening and closing of the electrical circuit. The rated power of the load resistor is P r , and the resistance value is R r . These two parameters are selected according to the following conditions.

[0144] (1) P r > P f

[0145] (2) (U f / I f) <R r <1.5(U f / I f )

[0146] Among them, P f U represents the peak power of the photovoltaic module. f I is the peak voltage of the photovoltaic module. f This represents the peak current of the photovoltaic module.

[0147] The monitoring circuit consists of a microcontroller circuit, a wireless communication circuit, a keyboard and LCD display circuit, a voltage detection circuit, a current detection circuit, a component backplane temperature detection circuit, an irradiation intensity detection circuit, and a relay control circuit.

[0148] The microcontroller circuit is the core circuit of the monitoring system, responsible for data acquisition, calculation and real-time control of the system. It consists of a CPU and peripheral circuits. The CPU can be a high-speed microcontroller, DSP, ARM chip, etc., and the CPU's operating frequency should be above 30MHz.

[0149] The system can be controlled in real time via wireless communication circuits through remote terminal devices (including mobile phones, tablets, etc.), and the real-time working status and historical faults of the system, as well as the real-time and historical data of various physical quantities can be viewed online.

[0150] The system's physical parameters can be set via a keyboard and LCD display circuit, and the system's operating status can be displayed in real time.

[0151] The voltage across the load resistor is detected by a voltage detection circuit.

[0152] The current passing through the load resistor is detected by a current detection circuit.

[0153] Solar irradiance intensity is detected using an irradiance intensity detection circuit.

[0154] The relay is controlled to open and close via a relay control circuit.

[0155] The backsheet temperature of the photovoltaic module is detected by a module backsheet temperature detection circuit.

[0156] The module backsheet temperature sensor is installed at the center of the back of the photovoltaic module.

[0157] In this invention, the actual output power P of the photovoltaic module is continuously detected. re The calculated output power P of the photovoltaic module is obtained by using parameters such as solar irradiance and module backsheet temperature. ca By comparing these two power values, it can be determined whether the snow on the surface of the component has melted.

[0158] The calculation process is as follows, where P caP is the calculated output power of the photovoltaic module. st P represents the rated output power of a photovoltaic module under standard test conditions. re T represents the actual output power of the photovoltaic module. a T represents the actual temperature of the photovoltaic cells inside the photovoltaic module. b T represents the actual temperature of the photovoltaic module backsheet. st The temperature is given by the standard test conditions, δ is the power temperature variation coefficient of the photovoltaic module, K is the comprehensive influence coefficient, and R is the temperature. a R represents the actual irradiance on the surface of the photovoltaic module. st U represents the irradiance under standard test conditions. r I is the voltage across the load resistor. r The current is the load resistor.

[0159] In the formula, R st =1000W / m 2 T st =25℃, P st The specific parameter values ​​for δ are provided by the photovoltaic module manufacturers based on the different models of photovoltaic modules.

[0160]

[0161] P re =U r ×I r

[0162] When P re >0.95P ca When the actual output power of the photovoltaic module is very close to or reaches the power generation capacity under normal conditions, it can be determined that the snow on the surface of the photovoltaic module has melted.

[0163] In the above formula, T a The two parameters, K and K, need to be determined through a special calculation method, as explained below.

[0164] (1)T a Calculation method

[0165] Because photovoltaic cells are very thin and brittle, they cannot be used directly outdoors. Therefore, an encapsulation shell is added to the front and back surfaces to improve their strength. The upper surface is high-transmittance tempered glass, and the lower surface is a high-strength insulating backsheet. The photovoltaic cells are bonded to the upper and lower surfaces with hot melt adhesive film. This is the typical internal structure of a photovoltaic module. Previous algorithms multiplied the output power of photovoltaic modules by a coefficient [1+δ×(T] when calculating the impact of temperature changes. b -T st The photovoltaic module backsheet temperature T in this coefficient is... bIt is not the actual temperature T of the photovoltaic cells inside the photovoltaic module. a Currently, there is no direct method to detect the temperature of the photovoltaic cells inside a photovoltaic module in photovoltaic power generation projects. The only method is to use a temperature sensor to detect the surface temperature of the module's backsheet. In previous calculations, the temperature of the module's backsheet was often used as an approximation of the temperature of the photovoltaic cells inside the module. However, this method has errors because the temperature sensor mounted on the module's backsheet is separated from the photovoltaic cells by a hot-melt adhesive film and a high-strength insulating backsheet. Therefore, the actual temperature T of the photovoltaic cells will vary. a It is more important than the temperature of the photovoltaic module backsheet (T). b The difference between these two temperature values ​​varies with the actual irradiance R on the surface of the photovoltaic module. a The effect of temperature on the output power of the photovoltaic module varies with temperature. In this algorithm, the coefficient multiplied when calculating the effect of temperature variation on the output power of the photovoltaic module is [1+δ×(T)]. a -T st The actual temperature of the photovoltaic cells inside the photovoltaic module can be calculated from the module backsheet temperature and the actual irradiance using the following formula. This calculation yields a more accurate theoretical output power value for the photovoltaic module compared to previous algorithms.

[0166]

[0167] In the formula, T ch T represents the temperature difference between the photovoltaic cells inside the photovoltaic module and the module backsheet under standard test conditions. ch =2.5℃, R st =1000W / m 2 .

[0168] (2) Calculation method of K

[0169] The comprehensive influence coefficient K includes the effects of dust accumulation on the module surface, the decline in photoelectric conversion efficiency of the module over time, and power losses caused by wires, relays, and terminals in the electrical circuit. Since the magnitudes of these influencing factors change slowly over time, and the patterns of change are difficult to quantify using a functional expression, fixed empirical values ​​are typically used when calculating the power generation of a photovoltaic system. However, this significantly impacts the accuracy of the calculation results. This invention uses real-time data, such as the actual power generation of the photovoltaic module, to back-calculate the K value. Based on this, the value of K is dynamically adjusted periodically to improve the accuracy of the calculation results.

[0170] At each hour, and satisfying R a >100W / m 2 And P re >0.1P stUnder the condition that R is satisfied, calculate the value of K according to the following formula, and take this value as the time from the current hour to the next time R is satisfied. a >100W / m 2 And P re >0.1P st The conditions are between the hourly times in the above calculation P ca The K value used in the formula. The next time the calculation conditions are met, a new K value is calculated to replace the old one, thus achieving dynamic adjustment based on actual data.

[0171]

[0172] Calculation method for the snow melting energy efficiency of air source heat pumps for photovoltaic systems

[0173] This invention proposes a method for calculating the snow melting energy efficiency of an air source heat pump for a photovoltaic system. The calculation process is as follows.

[0174]

[0175]

[0176] E j =E i -E r

[0177]

[0178] In the above formula, t z t represents the time it takes for snow to naturally melt on the surface of photovoltaic modules. j E represents the time consumed by the air-source heat pump system to melt snow on the surface of the photovoltaic modules. r E represents the electricity consumed by the air-source heat pump system during the snow melting process of photovoltaic modules. i E represents the additional power generated by the photovoltaic system after snow melting by the air-source heat pump system. j Compared to natural snow melting, the net increase in electricity generated by an air-source heat pump for snow melting is K. cop E represents the energy efficiency ratio of an air source heat pump system for snow melting. k (t) is a function of the electrical power consumed by the air source heat pump as a function of time, E f (t) is a function of the electrical power consumption of auxiliary equipment (including water pumps, solenoid valves, etc.) as a function of time, E p (t) is a function of the photovoltaic system's power generation as a function of time.

[0179] If E j A value >0 indicates that the increased power generation from the photovoltaic system through the air-source heat pump system during snow melting is greater than the power consumed by the air-source heat pump system during the snow melting process; if E j=0, indicating that the increased power generation from snow melting by the photovoltaic system through the air source heat pump system is equal to the power consumed by the air source heat pump system during the snow melting process; if E j <0 indicates that the increased power generation of the photovoltaic system through the air source heat pump system during snow melting is less than the power consumed by the air source heat pump system during the snow melting process.

[0180] K cop When the value is greater than 1, air-source heat pump snow melting is effective in increasing the net increase in system electricity consumption. cop The higher the value, the more significant the effect.

[0181] K cop When the value is 1, the electricity consumed by the air source heat pump snow melting method is equal to the increase in power generation of the photovoltaic system caused by snow melting. At this time, the impact of choosing the air source heat pump snow melting method or letting the photovoltaic modules melt snow naturally on the net energy of the entire system is the same.

[0182] K cop When the power consumption is less than 1, the air source heat pump snow melting method consumes too much electricity, exceeding the power generation increase of the photovoltaic system after snow melting. In this case, the photovoltaic module should be allowed to melt snow naturally.

Claims

1. A method of monitoring snow melt on a photovoltaic assembly, the method comprising: The method comprises the following steps: The photovoltaic power generation circuit is composed of one photovoltaic component, one relay and one load resistor; the photovoltaic component faces the south direction, and the inclination angle of the photovoltaic component is determined according to the monitoring requirement; the relay controls the opening and closing of the electric circuit; the rated power of the load resistor is P r , and the resistance is R r , and the two parameters are selected according to the following conditions; (1) P r > P f (2) (U f / I f )<R r <1.5 (U f / I f ) wherein Pf is the peak power of the photovoltaic module, U f is the peak voltage of the photovoltaic module, If is the peak current of the photovoltaic module; The monitoring circuit is composed of a microcontroller circuit, a wireless communication circuit, a keyboard and liquid crystal display circuit, a voltage detection circuit, a current detection circuit, a component backboard temperature detection circuit, an irradiance intensity detection circuit, and a relay control circuit; The microcontroller circuit is the core circuit of the monitoring system, responsible for data acquisition, calculation, and real-time control of the system, composed of a CPU and peripheral circuits. The CPU uses a high-speed single-chip microcomputer, DSP, or ARM chip, with a working frequency above 30 MHz; Through the wireless communication circuit, the system can be remotely controlled and monitored in real time, and the real-time working status, historical faults, real-time data, and historical data of various physical quantities can be viewed online; Through the keyboard and liquid crystal display circuit, some physical parameters of the system can be set, and the working status of the system can be displayed in real time; The voltage detection circuit detects the voltage across the load resistor; The current detection circuit detects the current through the load resistor; The irradiance intensity detection circuit detects the solar irradiance intensity; The relay control circuit controls the opening and closing of the relay; The component backboard temperature detection circuit detects the backboard temperature of the photovoltaic module; The component backboard temperature sensor is installed at the center of the back of the photovoltaic module; continuously detecting the actual output power P of the photovoltaic module re obtaining the calculated output power P of the photovoltaic module through the solar radiation intensity and the module backsheet temperature parameter ca comparing the two power values to determine whether the snow on the module surface is melted; The calculation process is as follows, wherein P ca is the calculated output power of the photovoltaic module, P st is the rated output power of the photovoltaic module under standard test conditions, P re is the actual output power of the photovoltaic module, T a is the actual temperature of the photovoltaic cell inside the photovoltaic module, Tb is the actual temperature of the backboard of the photovoltaic module, Tst is the temperature under standard test conditions, δ is the power temperature change coefficient of the photovoltaic module, K is the comprehensive influence coefficient, R a is the actual irradiance on the surface of the photovoltaic module, R st is the irradiance under standard test conditions, U r is the voltage of the load resistor, I r is the current of the load resistor; wherein R st = 1000 W / m 2 , T st = 25 °C, P st , δ are provided by the photovoltaic module manufacturer with specific parameter values for different types of photovoltaic modules; P re = U r x I r When P re > 0.95P ca , the actual output power of the photovoltaic module and the calculated output power value are very small, the power generation capacity of the photovoltaic module is close to or reaches the power generation capacity in the normal state, so it can be determined that the snow on the surface of the photovoltaic module has melted. The calculation method of K The value of K is calculated by real-time data of the actual power generation of the photovoltaic module; At each whole point time, and under the condition that R a > 100 W / m 2 and P re > 0.1P st , the K value is calculated according to the following formula, and the value is used as the K value in the above calculation P a formula between the whole point time when the condition R 2 > 100 W / m re and P st > 0.1P ca is met next time; when the calculation condition is met next time, a new K value is calculated instead of the old one, realizing dynamic adjustment according to actual data; wherein T ch is the difference between the temperature of the photovoltaic cells inside the photovoltaic module and the temperature of the backsheet of the module under standard test conditions, T ch = 2.5 °C, R st = 1000 W / m 2 . The calculation method of the energy efficiency of the air source heat pump for snow melting of the photovoltaic system The calculation process is as follows: E j = E i - E r t z t j E r Ei j K cop E k E f E p E If E j > 0, it means that the increased power generation of the photovoltaic system through the air source heat pump system for snow melting is greater than the power consumption of the air source heat pump system in the snow melting process; if E j = 0, it means that the increased power generation of the photovoltaic system through the air source heat pump system for snow melting is equal to the power consumption of the air source heat pump system in the snow melting process; if E j < 0, it means that the increased power generation of the photovoltaic system through the air source heat pump system for snow melting is less than the power consumption of the air source heat pump system in the snow melting process. K cop When K cop The larger the value, the more significant the effect. K cop When =1, the power consumption of the air source heat pump snow melting method is equal to the increased power generation of the photovoltaic system due to snow melting. At this time, the selection of the air source heat pump snow melting method or the natural snow melting method of the photovoltaic module has the same effect on the net energy of the entire system. K cop When <1, the air source heat pump snow melting method consumes too much electricity, which exceeds the increased power generation of the photovoltaic system after snow melting. At this time, the photovoltaic module natural snow melting method should be selected.

2. The method of claim 1, wherein The T a The parameters are determined by the following calculation method: T a of the computing method

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