CN101974420A - System for warming methane tank by ground source/air source heat pump and control method - Google Patents

Abstract

The invention belongs to the field of energy saving, and specifically relates to a system and a control method for heating a biogas digester by means of a ground source/air source heat pump. The control method is: when the average outdoor temperature is lower than 20°C for ten consecutive days, the ground source heat pump unit is activated for heat exchange; when the outdoor temperature is higher than 20°C for ten consecutive days, the air source heat pump unit is activated for heat exchange. When the temperature in the biogas digester drops below 35°C, the ground source/air source heat pump unit starts automatically, and transfers the heat of the groundwater to the hot water in the heat coil in the biogas digester by consuming electric energy; the input of the local source/air source heat pump unit , When the outlet water temperature difference reaches 7.5°C and the temperature of the biogas digester is at 35°C, the ground source/air source heat pump unit will automatically stop working. The present invention takes a medium-scale fermentation project as an object, and explores a new type of heating system and control method that improves energy utilization and reduces construction costs under the premise of ensuring gas production rate. This method not only has high energy-saving benefits but also has environmental protection effects good.

Description

A system and control method for heating a biogas digester by using a ground source/air source heat pump

technical field

The invention belongs to the field of energy saving and relates to ground source heat pump/air source heat pump technology, in particular to a system and control method for heating a methane pool by using a ground source/air source heat pump approach.

Background technique

Biogas is a renewable energy suitable for promotion and utilization in rural China. However, the low or no gas production of biogas digesters in cold seasons seriously restricts the use and promotion of biogas in rural areas. The main reason is that the ambient temperature is too low, which reduces the activity of biogas fermentation microorganisms.

Within a certain temperature range, temperature has a positive effect on fermentation efficiency, so reasonable temperature control is very necessary in future biogas projects. Generally, biogas bacteria can ferment in the range of 8-60°C. 10-26°C is the room temperature fermentation zone. Under this temperature condition, the tank volume gas production rate can reach 0.15-0.30m ³ /(m ³ ·d) (the pool volume gas production rate refers to the amount of biogas produced per unit volume of the biogas tank per day); 28-38°C is for medium-temperature fermentation zone (the optimum temperature is 35°C), the gas production rate of the tank volume can reach about 1.0m ³ /(m ³ ·d); 46～60℃ is the high-temperature fermentation zone, and the gas production rate of the tank volume can reach 2.0～2.5m ³ /(m ³ ·d). Therefore, if there is a heating method that can make the pool temperature of the biogas digester reach and maintain an appropriate level in the cold season, the gas production of biogas can be guaranteed.

At present, there are mainly the following six heating methods for biogas digesters: electric heating, solar heating, fossil energy hot water boiler heating, biogas boiler heating, biogas power generation waste heat heating and combustion pool heating.

Electric heating technology uses electric heaters to heat hot water, and heats the fermentation feed liquid through the flow of hot water in the circulation pipe of the biogas digester. However, this method consumes high-grade electric energy at the cost of low energy saving; the solar heating system completes the collection and transmission of heat energy through the solar heat collection system, and the solar hot water heats the feed liquid through the heat exchanger. The system is energy-saving and environmentally friendly, easy to operate, and can realize automatic operation, but it is easily affected by weather conditions; the heating of fossil energy hot water boilers uses hot water boilers burning coal, oil and other fuels as heat sources, and heats the fermentation materials through heat exchange equipment. Liquid heating. However, the combustion of fuel will produce a large amount of smoke and harmful gases, polluting the environment, and the energy utilization rate is not high; the heating of the biogas boiler is a part of the biogas generated by the combustion system itself, and the high-temperature flue gas generated by combustion flows in the bottom pipe of the reactor. Then heat the biogas digester, this method has high heating efficiency, and at the same time requires relatively high equipment and operating technology; the waste heat heating of biogas power generation is in the biogas cogeneration project, and the gas internal combustion engine will emit nearly 600 ℃ while the generator set is generating electricity The high-temperature gas contains a large amount of waste heat, and the waste heat is used to heat the fermentation raw materials through the heat exchanger in the waste heat recovery system. Generally, it is only used in large-scale biogas projects; The fuel in the pool is slowly burned, and the pool cover and pool wall surface can be kept at the temperature required for mesophilic fermentation according to the adjustment. This method can be burned for one winter with one-time input of low-quality fuel, without manual management, and is generally used in household biogas projects.

The above heating methods have their own advantages and disadvantages, but starting from the reality of wastewater treatment projects in medium-scale farms, there is currently no more economical, reasonable, energy-saving and environmentally friendly heating method.

Contents of the invention

The object of the present invention is to provide a system and control method for heating a biogas digester by means of a ground source/air source heat pump. That is, using geothermal energy and air heat energy as heat sources, the feed liquid is heated through the ground source heat pump/air source heat pump heating system. On the premise of ensuring the gas production rate, the energy utilization rate is improved and the construction cost is reduced. Among them, ground source heat pumps are mainly used in cold seasons, while air source heat pumps are mainly used in warm seasons, avoiding cold seasons where air source heat pumps may condense and frost.

The working principle of the present invention is as follows: in the cold season, the outdoor average temperature is lower than 20°C for ten consecutive days, and the ground source heat pump unit is used to exchange heat between the underground soil and circulating water; when the outdoor temperature is higher than 20°C for ten consecutive days, the ground source heat pump unit is activated The air source heat pump unit exchanges heat between the air and the circulating water of the digester and supplements the underground heat when the average underground temperature is lower than 17°C. Then the temperature of the circulating water is increased, and then a small amount of high-grade electric energy is input to the ground source heat pump/air source heat pump to realize the transfer of heat energy from the low temperature to the high temperature, so that the outlet water temperature of the ground source heat pump unit/air source heat pump unit reaches about 45°C , The hot water in the heat coil exchanges heat with the fermentation raw materials in the biogas digester in the way of radiation and convection, so that the temperature of the biogas digester is kept within the range of medium-temperature fermentation. Install an automatic temperature control device to realize automatic temperature control. When the temperature in the biogas tank drops below 35°C, the ground source heat pump/air source heat pump unit will automatically start, and transfer the heat of the groundwater to the hot water in the heat coil in the biogas tank by consuming electric energy. , and then heat the fermentation raw materials; when the temperature difference between the inlet and outlet water of the local source/air source heat pump unit meets 7.5°C and the temperature of the biogas digester is 35°C, the ground source/air source heat pump unit will automatically stop working.

The system for heating biogas digesters by means of ground source/air source heat pump proposed by the present invention is composed of underground loop 10, air cooling equipment 9, common unit of ground source/air source heat pump and control system, wherein:

The ground source/air source heat pump public unit includes a compressor 6 and a condenser 7; the first evaporator 5, the compressor 6, the condenser 7 and the second evaporator 8 are sequentially connected by pipelines to form a closed channel; the first evaporator The output end of 5 is connected to the underground loop 10, the input end is connected to the electromagnetic valve 1 on the ground source side, and the first evaporator 5 is connected to the air cooling device 9 through the electromagnetic valve 2 on the air source side to form a closed channel; the output end of the underground loop 10 is connected to the ground The pipeline connected to the solenoid valve 1 on the source side is connected to the first solenoid valve 3, the other end of the first solenoid valve 3 is connected to the input end of the condenser 7, and the input end of the underground loop 10 is connected to the output of the condenser 7 through the second solenoid valve 4 end;

The control system consists of an ambient temperature sensor 11, an average soil temperature sensor 12, a ground source heat pump unit outlet water temperature sensor 13, a ground source heat pump unit water inlet temperature sensor 14, a biogas tank temperature sensor 15, a signal generator, an actuator, a single chip microcomputer 25 and a computer 26; the ambient temperature sensor 11 is connected to the single-chip microcomputer 25 through the first signal generator 16, and the electromagnetic valve 1 on the ground source side is connected to the single-chip microcomputer 25 through the first actuator 21 to form a closed loop; The single-chip microcomputer 25 forms a closed loop; the first solenoid valve 3 is connected with the single-chip microcomputer 25 to form a closed loop by the third actuator 23; the second electromagnetic valve 4 is connected with the single-chip microcomputer 25 to form a closed loop by the fourth actuator 24; the soil average temperature sensor 12 passes through the second The signal generator 17 is connected to the input end of the single-chip microcomputer 25, the outlet water temperature sensor 13 of the ground source heat pump unit is connected to the input end of the single-chip microcomputer 25 through the third signal generator 18, and the water inlet temperature sensor 14 of the ground source heat pump unit is connected to the input end of the single-chip microcomputer 25 through the fourth signal generator 19. The input end of the single-chip microcomputer 25 and the biogas tank temperature sensor 15 are connected to the input end of the single-chip microcomputer 25 through the fifth signal generator 20; the single-chip microcomputer 25 is connected to a computer 26 .

In the present invention, the underground loop 10 is an underground pipe and a valve, and the air cooling device 9 is a fan.

The control method of heating the biogas digester with the ground source/air source heat pump approach proposed by the present invention, the specific steps are as follows:

(1) Environmental temperature sensor 11 gathers temperature signal and sends corresponding digital signal by first signal generator 16 and transmits to single-chip microcomputer 25, records in computer 26 through the digital conversion of single-chip microcomputer 25, adopts corresponding program analysis temperature data, when program When the average temperature of the environment is found to be lower than 20°C for ten consecutive days, a control command is issued, and the actuator operates the corresponding command to realize the opening of the solenoid valve 1 on the ground source side, and the closing of the solenoid valve 2, the first solenoid valve 3 and the second solenoid valve 4 on the source side. At this time, the working mode using the underground soil as the heat source; when the working mode using the underground soil as the heat source is in progress, the unit does not run continuously. The ground source heat pump unit inlet water temperature sensor 14, the ground source heat pump unit outlet water temperature sensor 13 and the digester temperature sensor 15 collect temperature signals through the fourth signal generator 19, the third signal generator 18 and the fifth signal generator 20 respectively. The corresponding digital signal is transmitted to the single-chip microcomputer 25, and then transferred to the computer 26. If the computer 26 program finds that the temperature difference between the inlet and outlet water of the ground source heat pump unit meets 7.5°C, and the temperature of the biogas digester is 35°C, an instruction is issued, and the actuator executes the operation , so that the electromagnetic valve 1 on the ground source side, the electromagnetic valve 2 on the air source side, the first electromagnetic valve 3 and the second electromagnetic valve 4 are all closed, so that the heating system stops heating;

(2) Environmental temperature sensor 11 gathers temperature signal and sends corresponding digital signal by first signal generator 16 and transmits to single-chip microcomputer 25, records in computer 26 through the digital conversion of single-chip microcomputer 25, and corresponding program analyzes temperature data, when program finds When the average ambient temperature is higher than 20°C for ten consecutive days, a control instruction is issued, and the actuator operates the corresponding instruction to open the solenoid valve 2 on the air source side, and close the solenoid valve 1, the first solenoid valve 3 and the second solenoid valve 4 on the ground source side , at this time the working mode with outdoor air as the heat source; when the working mode with the outdoor air as the heat source is in progress, the unit does not run continuously. The ground source heat pump unit inlet water temperature sensor 14, the ground source heat pump unit outlet water temperature sensor 13 and the digester temperature sensor 15 collect temperature signals through the fourth signal generator 19, the third signal generator 18 and the fifth signal generator 20 respectively. The corresponding digital signal is transmitted to the single-chip microcomputer 25, and then transferred to the computer 26. If the program of the computer 26 finds that the temperature difference between the inlet and outlet water of the ground source heat pump meets 7.5°C, and the temperature of the biogas digester is 35°C, an instruction is issued, and the actuator executes the operation , so that the electromagnetic valve 1 on the ground source side, the electromagnetic valve 2 on the air source side, the first electromagnetic valve 3 and the second electromagnetic valve 4 are all closed, so that the heating system stops heating;

(3) ambient temperature sensor 11 and soil average temperature sensor 12 gather temperature signal and send corresponding digital signal by first signal generator 16, second signal generator 17 respectively and transmit to single-chip microcomputer 25, record through the digit conversion of single-chip microcomputer 25 in In the computer 26, the corresponding program analyzes the temperature data. When the program finds that the average ambient temperature is higher than 20°C for ten consecutive days, and the average soil temperature is lower than 17°C, a control command is issued, the solenoid valve 2 on the air source side is opened, and the electromagnetic valve on the ground source side is Valve 1, the first solenoid valve 3 and the second solenoid valve 4 are closed, and after working for 2 hours, the computer 26 program sends out instructions, and the actuator sends out actions to realize the air source side solenoid valve 2, the first solenoid valve 3 and the second solenoid valve 4 When it is turned on, the electromagnetic valve 1 on the ground source side is closed, and at this time, the heat from the outdoor air is used to supplement the heat from the ground.

Advantages of the present invention: (1) adopting the ground source heat pump/air source heat pump method heating biogas digester technology of the present invention can be conveniently realized by on-site assembly, simple in structure, practical, safe and convenient; (2) ground source heat pump/air source heat pump The source heat pump heating system can operate automatically, the operation is simple, the heat of the soil is well utilized, and the energy consumption is small; (3) No fuel is required, no pollution, and is not affected by the weather.

Description of drawings

Figure 1 is a block diagram of a biogas digester system heated by a ground source heat pump/air source heat pump.

Fig. 2 is a block diagram of the control system of the biogas digester system heated by the ground source heat pump/air source heat pump approach shown in Fig. 1 .

Numbers in the figure: 1 is the solenoid valve on the ground source side; 2 is the solenoid valve on the air source side; 3 is the first solenoid valve; 4 is the second solenoid valve; 5 is the first evaporator; 6 is the compressor; 7 is the condenser ; 8 is the second evaporator; 9 is the air cooling equipment; 10 is the underground loop; 11 is the ambient temperature sensor; 12 is the soil average temperature sensor; Water temperature sensor; 15 is the digester temperature sensor; 16-20 are respectively the first signal generator, the second signal generator, the third signal generator, the fourth signal generator and the fifth signal generator; 21-24 are respectively 25 is a single-chip microcomputer (data acquisition board); 26 is a computer.

Detailed ways

Further describe the present invention below by embodiment in conjunction with accompanying drawing.

Embodiment 1: As shown in Figures 1-2, the system consists of an underground loop 10, an air cooling device 9, a ground source/air source heat pump unit and a control system, and the control parameter collection part of the control system includes the ambient temperature The sensor 11, the average soil temperature sensor 12, the outlet water temperature sensor 13 of the ground source heat pump unit, the inlet water temperature sensor 14 of the ground source heat pump unit and the biogas tank temperature sensor 15 are all DS18B20 temperature sensors to collect temperature signals. The temperature control part of the biogas tank in the control system is composed of a signal generator, an actuator, a single-chip microcomputer 25 and a computer 26. The single-chip microcomputer 25 and the computer 26 are connected by an R232 interface signal line, and the rest are directly connected by signal lines to realize automatic control. The underground loop 10 is a buried pipe and some valves, and the air-cooling device 9 is a blower fan, which act as four major parts of the unit (condenser 7, compressor 6, first evaporator 5 and second evaporator 5) in the heating mode. The evaporator in the device 8); the common part of the unit is composed of a compressor 6 and a condenser 7, and is a common part of two different heating modes of the unit. The first evaporator 5, the compressor 6, the condenser 7 and the second evaporator 8 are connected by copper tubes in order to form a closed channel; the refrigerant flows in it, and the biogas digester is heated by the reverse Carnot principle circulation . The control system mainly controls the opening and closing of the entire system, switching of operating modes, etc. by controlling the opening and closing of the solenoid valve. The output end of the first evaporator 5 is connected to the underground loop 10, the input end is connected to the ground source side electromagnetic valve 1, and the first evaporator 5 is connected to the air cooling device 9 through the air source side electromagnetic valve 2 to form a closed channel; the underground loop 10 The pipeline connecting the output end to the electromagnetic valve 1 on the ground source side is connected with the first electromagnetic valve 3, the other end of the first electromagnetic valve 3 is connected to the input end of the condenser 7, and the input end of the underground loop 10 is connected to the condenser through the second electromagnetic valve 4. The output terminal of device 7.

The air source heat pump system is turned on for 4 hours a day, of which 2 hours are used to heat the digester, and the other 2 hours are used to transfer air heat to the ground to supplement the heat extracted from the ground in cold seasons.

The control system includes: a control parameter acquisition system, a digester temperature control system and a heating mode switching control system.

1. The control parameter acquisition system is controlled by the temperature of the biogas digester, the temperature difference between the inlet and outlet water of the heat coil of the digester and the average temperature of the environment. The acquisition instrument is a temperature sensor and a single-chip microcomputer. The ambient temperature sensor 11, the average soil temperature sensor 12, the ground-source heat pump unit outlet water temperature sensor 13, the ground-source heat pump unit water inlet temperature sensor 14, and the biogas tank temperature sensor 15 are all connected to the single-chip microcomputer 25 through signal lines. connected, the digital signal is transmitted to the single-chip microcomputer 25, and then the corresponding data acquisition and analysis platform of the computer 26 control platform executes the set control mode after receiving the control signal to realize the control function.

2. The working mode of the biogas digester temperature control system is: after the control parameter acquisition system collects the temperature of the biogas digester and the temperature difference between the inlet and outlet water of the heating coil, if the temperature difference between the inlet and outlet water meets 7.5°C and the temperature of the biogas digester is at 35°C, the heating The system stops heating, otherwise, the heating system starts.

3. The control parameter collection system collects the average outdoor temperature and the average temperature of the underground soil to change the heating mode. There are 3 heating modes:

1) When the average ambient temperature is lower than 20°C for ten consecutive days, the solenoid valve 1 on the ground source side is opened, and the solenoid valve 2, the first solenoid valve 3 and the second solenoid valve 4 are closed on the air source side. At this time, the underground soil is used as the heat source working mode;

2) When the average ambient temperature is higher than 20°C for ten consecutive days, the solenoid valve 2 on the air source side is opened, and the solenoid valve 1, the first solenoid valve 3 and the second solenoid valve 4 are closed on the ground source side. At this time, the outdoor air is used as the heat source Operating mode;

3) When the average ambient temperature is higher than 20°C for ten consecutive days and the average underground soil temperature is lower than 17°C, the solenoid valve 2 on the air source side is opened, and the solenoid valve 1, the first solenoid valve 3 and the second solenoid valve 4 on the ground source side are Close, after working for 2 hours, switch to open air source side solenoid valve 2, first solenoid valve 3 and second solenoid valve 4, close ground source side solenoid valve 1, at this time use outdoor air heat to supplement underground heat.

In the present invention, the temperature of the biogas digester can be kept at about (35±2)°C under the action of the heating system, and the gas production rate can be kept at about 0.6m ³ /(m ³ ·d) in the range of mesophilic fermentation. Sometimes the fermentation temperature can reach 35°C, and the gas production rate can reach 1.1m ³ /(m ³ ·d).

In the present invention, the heating efficiency (COP) of the ground source heat pump unit is maintained at about 3.6, and the system COP is about 2.7. The primary energy consumption of the system is small, and the primary energy utilization coefficient can reach 0.84. Compared with the electric heating film heating system, the energy saving rate was 63%.

The above system is used in a small-scale centralized gas supply project with 300 pigs in stock and a daily gas output of 36m ³ for 30 users. The effective volume of the biogas digester is 69.3m ³ . The internal size of the biogas digester is 3.8m×3.8m×4.8m (length×width×height), and the thermal insulation material of the closed-cell polystyrene foam board with a thickness of 7cm is added to the bottom and wall of the pond to weaken the connection between the biogas digester and the earth, Heat conduction in air. The top of the biogas digester is covered with plastic film for heat preservation, and the coverage is larger than the pool surface to facilitate heat preservation. Heating coils are laid along the inner wall of the digester for heating. The heating coil adopts φ25*2.8 PERT pipe, the total length of the coil is 200m, and the distance between the coils is 200mm. In order to speed up the heat transfer of the feed liquid and improve the heating effect, a stirring device is installed in the biogas digester. Install a mixer in the middle of the side wall of the biogas digester at a height of 0.8m from the bottom of the digester for stirring. The parameters of the mixer are: rated power 2.5kw, rated operating frequency 50Hz, speed 740r/min. The ground source heat pump unit is 10.2kw/380V.

Among them, the ground source heat pump system works for an average of 1.5 hours a day, intermittent operation, which can alleviate the thermal imbalance of the underground soil temperature field.

The temperature of the biogas digester is kept at about (32±2)°C, and the gas production rate can be kept at about 0.6m ³ /(m ³ ·d), which is 1.5 times the national standard value of 0.2～0.4m ³ /(m ³ ·d). ~3 times.

Claims (3)

1. A system for heating a biogas digester with a ground source/air source heat pump, consisting of an underground loop (10), an air cooling device (9), a ground source/air source heat pump common unit and a control system, characterized in that: The ground source/air source heat pump public unit includes a compressor (6) and a condenser (7); the first evaporator (5), the compressor (6), the condenser (7) and the second evaporator (8) pass through The pipes are connected to form a closed channel; the output end of the first evaporator (5) is connected to the underground loop (10), the input end is connected to the electromagnetic valve (1) on the ground source side, and the first evaporator (5) passes through the electromagnetic valve on the air source side. The valve (2) is connected to the air-cooling equipment (9) to form a closed channel; the pipeline connecting the output end of the underground loop (10) and the electromagnetic valve (1) on the ground source side is connected with a first electromagnetic valve (3), and the first electromagnetic valve The other end of the valve (3) is connected to the input of the condenser (7), and the input of the underground loop (10) is connected to the output of the condenser (7) through the second electromagnetic valve 4; The control system consists of an ambient temperature sensor (11), an average soil temperature sensor (12), a ground source heat pump unit outlet water temperature sensor (13), a ground source heat pump unit water inlet temperature sensor (14), a digester temperature sensor (15), signal generator, actuator, single-chip microcomputer (25) and computer (26); the ambient temperature sensor (11) is connected to the single-chip microcomputer (25) through the first signal generator (16), and the electromagnetic valve on the ground source side (1) is executed through the first Device (21) connects single-chip microcomputer (25) to form a closed loop; air source side solenoid valve (2) connects single-chip microcomputer (25) to form a closed loop through the second actuator (22); the first electromagnetic valve (3) passes the third actuator (23) connect single-chip microcomputer (25) and form closed loop; Second electromagnetic valve (4) connects single-chip microcomputer (25) to form closed loop by the 4th actuator (24); Soil average temperature sensor (12) passes second signal generator ( 17) Connect the input end of the single-chip microcomputer (25), the outlet water temperature sensor (13) of the ground source heat pump unit to the input end of the single-chip microcomputer (25) through the third signal generator (18), and the water inlet temperature sensor (14) of the ground source heat pump unit Connect the input end of single-chip microcomputer (25) by the 4th signal generator (19), the digester temperature sensor (15) connects the input end of single-chip microcomputer (25) by the 5th signal generator (20); Single-chip microcomputer (25) connects computer ( 26). 2. The system for heating a biogas digester with a ground source/air source heat pump approach according to claim 1, characterized in that the underground loop (10) is a buried pipe and a valve, and the air cooling device (9) is fan. 3. A method for controlling the system of heating a biogas digester with a ground source/air source heat pump approach as claimed in claim 1, characterized in that the specific steps are as follows: (1) environment temperature sensor (11) collects temperature signal and sends corresponding digital signal by first signal generator (16) and transmits to single-chip microcomputer (25), records in computer (26) through the digital conversion of single-chip microcomputer (25), Use the corresponding program to analyze the temperature data. When the program finds that the average temperature of the environment is lower than 20°C for ten consecutive days, a control command is issued, and the actuator operates the corresponding command to realize the opening of the solenoid valve (1) on the ground source side and the solenoid valve (2) on the source side. 1. The first electromagnetic valve (3) and the second electromagnetic valve (4) are closed, and at this time, the working mode using the underground soil as the heat source; when the working mode using the underground soil as the heat source is carried out, the unit does not run continuously; the ground source heat pump unit The temperature signals collected by the inlet water temperature sensor (14), the outlet water temperature sensor (13) of the ground source heat pump unit and the biogas tank temperature sensor (15) pass through the fourth signal generator (19), the third signal generator (18) and the third signal generator respectively. The five-signal generator (20) sends a corresponding digital signal to the single-chip microcomputer (25), and then transfers it to the computer (26). When the temperature is 35°C, an instruction is issued, and the actuator performs an operation action, so that the solenoid valve (1) on the ground source side, the solenoid valve (2) on the air source side, the first solenoid valve (3) and the second solenoid valve (4) are all Close, so that the heating system stops heating; (2) ambient temperature sensor (11) collects temperature signal and sends corresponding digital signal through first signal generator (16) and transmits to single-chip microcomputer (25), records in computer (26) through the digital conversion of single-chip microcomputer (25), The corresponding program analyzes the temperature data. When the program finds that the average temperature of the environment is higher than 20°C for ten consecutive days, it issues a control command, and the actuator operates the corresponding command to open the solenoid valve (2) on the air source side, and open the solenoid valve (1) on the ground source side. 1. Both the first solenoid valve (3) and the second solenoid valve (4) are closed. At this time, the working mode takes the outdoor air as the heat source; when the working mode takes the outdoor air as the heat source, the unit does not run continuously; the ground source heat pump The unit inlet water temperature sensor (14), the ground source heat pump unit outlet water temperature sensor (13) and the digester temperature sensor (15) collect temperature signals through the fourth signal generator (19), the third signal generator (18) and the The fifth signal generator (20) sends a corresponding digital signal to the microcontroller (25) and transmits it to the computer (26). When the temperature of the pool is 35°C, an instruction is issued, and the actuator performs an operation action, so that the solenoid valve (1) on the ground source side, the solenoid valve (2) on the air source side, the first solenoid valve (3) and the second solenoid valve (4) Both are closed, so that the heating system stops heating; (3) ambient temperature sensor (11) and soil average temperature sensor (12) gather temperature signal and send corresponding digital signal by first signal generator (16), second signal generator (17) and transmit to single-chip microcomputer (25) respectively ), is recorded in the computer (26) through the digital conversion of the single-chip microcomputer (25), and the corresponding program analyzes the temperature data, and when the program finds that the average ambient temperature is higher than 20°C for ten consecutive days, and the average soil temperature is lower than 17°C, it sends out control Instruction, air source side solenoid valve (2) is opened, ground source side solenoid valve (1), first solenoid valve (3) and second solenoid valve (4) are closed, after working for 2 hours, the computer (26) program issues an instruction, The actuator sends out an action to realize the solenoid valve (2), the first solenoid valve (3) and the second solenoid valve (4) on the air source side are opened, and the solenoid valve (1) on the ground source side is closed. At this time, the outdoor air heat is used to supplement the ground heat.

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