Solar photothermal and geothermal coupled heating and domestic hot water comprehensive energy system and control method

Abstract

The application provides a solar heat and geothermal heat coupled heat supply and domestic hot water comprehensive energy system and a control method thereof, and the system comprises a flat plate collector, a coaxial sleeve type buried pipe heat exchanger, a heat storage water tank, a domestic hot water tank, an electric heating boiler, a ground source heat pump unit, a circulating pump group and a central control unit. In a non-heating season, the flat plate collector collects solar heat energy to heat the domestic hot water tank, meets the domestic hot water demand, and the electric heating boiler is used to supplement when the solar energy is insufficient or at night; when the hot water is in surplus, the heat is stored in the ground through the buried pipe heat exchanger, cross-season heat storage is realized, and the cold accumulation of the ground heat is prevented. In a heating season, the ground heat is preferentially used to meet the heating load, and the ground source heat pump is started to assist the heat supply when the outlet temperature of the buried pipe is insufficient; meanwhile, the domestic hot water system operates, and the surplus heat is used for heating instead of being stored in the ground. The solar heat system and the ground heat system are coupled through the cross-season heat storage of the buried pipe, energy efficient utilization and system collaborative operation are realized.

Description

Technical Field

[0001] This invention belongs to the field of renewable energy comprehensive utilization and building energy supply technology, specifically relating to a solar thermal and geothermal coupled integrated energy system for heating and domestic hot water and its control method. Background Technology

[0002] With the increasing prominence of energy crises and environmental issues, the development and utilization of renewable energy has received widespread attention. Solar and geothermal energy, as two important renewable energy sources, have broad application prospects in building heating and domestic hot water supply. According to statistics from the International Energy Agency (IEA) in 2024, building energy consumption accounts for 30%-40% of total social energy consumption, with heating and domestic hot water consumption accounting for 60%-70% of building energy consumption. In the cold regions of northern my country, winter heating energy consumption accounts for 50%-65% of total building energy consumption. Therefore, developing efficient renewable energy heating systems is of significant strategic importance for achieving "dual carbon" goals and promoting energy structure transformation.

[0003] Currently, solar water heating systems and ground source heat pump systems typically operate independently. A solar water heating system mainly consists of solar collectors, a hot water storage tank, a circulating pump, and a control system. It heats the water in the tank by absorbing solar radiation energy through the collectors. According to the "Report on the Development of the Solar Thermal Utilization Industry," by the end of 2023, my country's installed solar water heater area exceeded 500 million square meters, saving approximately 60 million tons of standard coal annually. However, solar water heating systems have the following significant limitations: (1) The system is greatly affected by weather conditions and its operation is unstable. It cannot work effectively on cloudy or rainy days and at night, and the system's heat collection efficiency drops significantly. Actual measurement data shows that the heat collection efficiency on cloudy days is only 20%-40% of that on sunny days, and it cannot collect heat at all at night. This requires the system to be equipped with a large-capacity auxiliary heat source, which increases the initial investment and operating costs.

[0004] (2) There is a serious seasonal mismatch. Taking Beijing as an example, the average daily solar radiation in summer (June-August) can reach 20-25 MJ / m², while in winter (December-February) it is only 8-12 MJ / m², a difference of 2-3 times. At the same time, the demand for building heat load is small in summer (mainly domestic hot water, accounting for about 15%-20% of the annual heat load), while the demand for heating load is large in winter (accounting for 70%-80% of the annual heat load). This mismatch in supply and demand in time results in a large amount of solar thermal energy being wasted in summer, while the solar energy system is unable to meet the heat load demand in winter. According to statistics, the annual average solar energy guarantee rate of traditional solar water heating systems is only 40%-60%, and drops to 20%-30% in winter.

[0005] (3) A large-capacity auxiliary heat source is required. To ensure the continuity and reliability of hot water supply, the system must be equipped with auxiliary heat sources such as electric heating or gas boilers, whose installed capacity usually needs to reach 80%-100% of the peak heat load. This not only increases the initial investment cost, but also leads to the auxiliary heat source being idle for a long time in summer, resulting in low equipment utilization.

[0006] (4) Limited heat storage capacity. The heat storage tank capacity of conventional solar water heating systems is generally only enough for 1-3 days of hot water consumption, which can only achieve short-term heat storage (daily heat storage) and cannot achieve cross-seasonal heat storage. This means that the surplus solar heat energy in summer cannot be stored for use in winter.

[0007] Ground source heat pump systems utilize shallow geothermal resources (typically referring to soil and groundwater within 200 meters below the surface) as heat sources and cold sources, using heat pump units to provide heating and cooling for buildings. Ground source heat pump systems offer advantages such as stable operation, high energy efficiency ratio, and environmental friendliness. According to the "Technical Specification for Ground Source Heat Pump System Engineering" (GB50366-2009), the heating energy efficiency ratio (COP) of ground source heat pump systems can reach 3.5-4.5, which is 30%-50% higher than traditional air source heat pumps and 40%-60% more energy-efficient than gas boilers. By the end of 2023, the application area of ​​ground source heat pump systems in my country had exceeded 800 million square meters.

[0008] However, ground source heat pump systems suffer from the problem of heat and cold accumulation in the underground soil during long-term operation, which has become a key technical bottleneck restricting their widespread application. Especially in cold regions where heating is the primary function (such as northern my country), ground source heat pump systems continuously extract heat from the ground in winter, while the cooling load is low or unnecessary in summer, leading to a severe imbalance in the heat balance of the underground soil. Research shows that: (1) Soil temperature decreases year by year. In heating-dominated applications, after 5-10 years of continuous operation, the soil temperature around the buried pipe may decrease by 3-8℃, forming a "cold accumulation" phenomenon. Monitoring data from a certain actual project showed that after 8 years of operation, the outlet temperature of the buried pipe dropped from the initial 12℃ to 6℃, a decrease of 50%.

[0009] (2) Severe degradation of system performance. The drop in soil temperature leads to a decrease in the evaporation temperature of the heat pump unit, an increase in the compressor pressure ratio, a decrease in the system energy efficiency ratio (COP) of 15%-30%, and a decrease in heating capacity of 10%-25%. When the soil temperature drops below 0℃, the buried pipe may also freeze, which may cause the system to fail to operate normally in severe cases.

[0010] (3) Increased initial investment costs. To avoid cold buildup, the number or depth of buried pipes needs to be increased during the design phase, typically requiring an increase of 20%-40% in the length of the buried pipes. This results in the initial investment of the buried pipe heat exchanger accounting for 40%-50% of the total system investment, significantly increasing the economic burden of the project. Taking a 100kW heating system as an example, the drilling cost for the buried pipes is approximately 150-250 yuan / meter, with a total drilling depth of 3000-5000 meters, resulting in an investment of 450,000-1,250,000 yuan for the buried pipe portion alone.

[0011] Existing technologies have already attempted to combine solar and geothermal energy. For example: Chinese patent CN201510847XXX discloses a solar-assisted ground source heat pump system, which provides an auxiliary heat source for the ground source heat pump through a solar collector, thereby improving the heating performance in winter.

[0012] Chinese patent CN201620345XXX discloses a solar-ground source heat pump composite system that uses solar collectors to supplement heat to the ground in summer.

[0013] Chinese patent CN201710123XXX discloses a solar-ground source heat pump system with seasonal heat storage, which uses buried pipes as seasonal heat storage devices.

[0014] However, existing technical solutions still have the following significant shortcomings: (1) The system structure is complex and the control strategy is imperfect. Existing systems often simply connect solar energy systems and ground source heat pump systems in parallel or series, lacking organic coupling and deep integration. The system requires multiple heat exchangers, multiple hot water storage tanks and complex piping systems, resulting in a complex system structure, high initial investment and large footprint. At the same time, the control strategy is not perfect, making it difficult to achieve coordinated control and optimized operation of the two subsystems, and unable to dynamically adjust the operating mode according to real-time operating conditions.

[0015] (2) The seasonal mismatch of solar energy has not been effectively addressed. Existing systems mainly utilize solar energy for auxiliary heating in winter, but due to insufficient solar energy resources in winter (only 40%-50% of summer's), the auxiliary effect is limited, and the solar energy guarantee rate only increases by 5%-15%. Meanwhile, the surplus solar thermal energy in summer (accounting for 50%-60% of the annual solar heat collection) cannot be effectively utilized, resulting in serious energy waste. It is estimated that in northern regions, the overheating problem of solar energy systems in summer leads to the waste of about 40%-50% of solar heat collection.

[0016] (3) The cross-seasonal thermal storage mechanism is imperfect. Although some studies have proposed the concept of using buried pipes for seasonal thermal storage, the existing technical solutions have the following problems: the thermal storage control strategy is unclear, and there is a lack of quantitative design methods for key control parameters such as thermal storage start-up conditions, thermal storage temperature, and thermal storage flow rate; the thermal storage efficiency is low, and due to the low thermal conductivity of the soil (generally 1.5-3.0 W / (m·K)), the stored heat is severely lost through lateral diffusion underground, and the measured seasonal thermal storage efficiency is only 30%-50%; it has failed to be effectively integrated with the domestic hot water system and heating system, and the thermal storage system operates as an independent subsystem, which increases the system complexity.

[0017] (4) Failure to coordinate the supply of heating load and domestic hot water load. Existing systems typically treat heating and domestic hot water as two independent subsystems, configuring collectors, hot water storage tanks, and control systems separately, which fails to achieve flexible allocation and tiered utilization of heat. This results in: redundant equipment configuration, increasing initial investment by 20%-30%; inability to achieve optimal heat distribution, as surplus heat from one load cannot be transferred to another; and reduced overall system energy efficiency and economy.

[0018] (5) The geothermal energy compensation mechanism is imperfect. Although the existing system proposes the idea of ​​supplementing the ground with heat, the following problems exist: the timing of heat supplementation is not controlled reasonably. Some systems supplement heat all year round, resulting in excessively high underground temperatures in summer (above 25°C), which reduces the heat extraction capacity of the ground source heat pump in winter; the control of the amount of heat supplementation lacks a basis, and it is impossible to dynamically adjust the amount of heat supplementation according to the heat extraction in winter and changes in soil temperature, resulting in insufficient or excessive heat supplementation; there is a lack of long-term operation data verification, and the sustainability and stability of the heat supplementation effect need to be verified.

[0019] (6) Poor system economy. Due to the complex system structure, redundant equipment configuration and imperfect control strategy, the initial investment of the existing solar-ground source heat pump composite system is 40%-60% higher than that of a single system, while the energy-saving benefits are only 20%-30% higher. The investment payback period is as long as 12-18 years, which is economically poor and limits its promotion and application.

[0020] Therefore, there is an urgent need to develop a solar thermal and geothermal coupling system with a simple structure, a sound control strategy, and good economic efficiency to achieve efficient complementary utilization and deep integration of solar and geothermal energy, effectively solve technical problems such as seasonal mismatch of solar energy and cold accumulation of geothermal energy, and at the same time meet the comprehensive needs of building heating and domestic hot water, thereby improving the overall energy efficiency and economy of the system. Summary of the Invention

[0021] To address the shortcomings of existing technologies, this invention provides a comprehensive energy system for heating and domestic hot water supply coupled with solar thermal and geothermal energy, and its control method. The aim is to solve the technical problems of seasonal mismatch of solar energy, cold accumulation of geothermal energy, and inability to coordinate the supply of heating and domestic hot water in existing technologies.

[0022] This invention is achieved through the following technical solution: A solar thermal and geothermal integrated energy system for heating and domestic hot water coupling includes: a flat plate collector, a domestic hot water tank, an electric heating boiler, a buried pipe heat exchanger, a hot water storage tank, a ground source heat pump unit, heating terminals, and a central control unit. The outlet of the flat plate solar collector is connected to the inlet of the domestic hot water tank, forming a solar thermal circulation loop. The outlet of the domestic hot water tank is connected to the inlet of the electric heating boiler and the inlet of the buried pipe heat exchanger, respectively. The outlet of the electric heating boiler flows back to the domestic hot water tank, forming an auxiliary heating circuit for domestic hot water. The outlet of the buried pipe heat exchanger is connected to the inlet of the hot water storage tank and the evaporator inlet of the ground source heat pump unit, respectively. The condenser outlet of the ground source heat pump unit is connected to the inlet of the hot water storage tank. The outlet of the hot water storage tank is connected to the inlet of the heating terminal. The outlet of the heating terminal flows back to the hot water storage tank, forming a heating circulation loop. The signal terminals of the central control unit are respectively connected to the flat plate collector, domestic hot water tank, electric heating boiler, buried pipe heat exchanger, hot water storage tank, ground source heat pump unit, and the electric control valves and circulation pumps of each circulation loop. The central control unit is configured to switch the system operation mode according to seasonal operating conditions, temperature parameters and heat load demand, so as to realize the integrated supply of heating and domestic hot water and the cross-seasonal solar heat storage.

[0023] Preferably, the buried pipe heat exchanger adopts a bidirectional convection heat exchange structure with the inner pipe guiding the flow downward and the annular heat exchange gap returning the flow upward, including an outer pipe and an inner pipe; the outer pipe and the inner pipe are arranged coaxially and nested, with the inner pipe housed inside the cavity of the outer pipe, and a sealed annular heat exchange gap is formed between the outer wall of the inner pipe and the inner wall of the outer pipe. The upper end of the inner tube forms the inlet of the buried pipe, and the lower end of the inner tube is an open structure that extends to the bottom of the outer tube. The bottom of the outer tube is a closed end, allowing the lower end of the inner tube to be in fluid communication with the annular heat exchange gap at the bottom. The upper end of the outer pipe and the upper end of the inner pipe form the outlet of the buried pipe; The heat exchange medium enters the inner pipe through the inlet of the buried pipe and flows vertically downward along the inner pipe. It then changes direction at the bottom of the outer pipe and enters the annular heat exchange gap. It then flows vertically upward along the annular heat exchange gap back to the outlet of the buried pipe, forming a unidirectional counter-current heat exchange flow path. The burial depth of the buried pipe is 50-200 meters.

[0024] Preferably, it further includes a temperature sensor group, the temperature sensor group comprising: A first temperature sensor is installed at the fluid outlet of the flat plate collector, a second temperature sensor is installed inside the domestic hot water tank, a third temperature sensor is installed at the fluid outlet of the buried pipe heat exchanger, and a fourth temperature sensor is installed inside the hot water storage tank. The signal output terminals of each temperature sensor are electrically connected to the signal input terminals of the central control unit.

[0025] Preferably, the solar thermal collection circulation loop, the domestic hot water auxiliary heating loop, and the heating circulation loop are all equipped with circulation pumps and electrically controlled valves. The central control unit can switch between modes such as cross-seasonal heat storage in the non-heating season, direct heating in the heating season, heat pump-assisted heating in the heating season, and hot water-assisted heating in the heating season by adjusting the speed of the circulation pump and the on / off state of the electrically controlled valve.

[0026] Preferably, the domestic hot water tank is provided with a temperature stratification structure, including: a vertically arranged stratified flow guiding component, a bottom cold water distributor and an upper hot water collector; the stratified flow guiding component is divided into multiple temperature gradient chambers along the height of the tank, so that the water in the tank forms a stable temperature stratification of a high temperature zone at the top and a low temperature zone at the bottom, and suppresses the mixing of hot and cold water. Multiple sets of vertical guide plates are evenly arranged along the height direction on the inner wall of the hot water storage tank. The guide plates are provided with flow stabilizing holes, and a meandering water flow channel is formed between adjacent guide plates. The ground source heat pump unit is an auxiliary heating device that is only started during the heating season when the outlet temperature of the buried pipe heat exchanger is lower than the heating threshold, and is completely shut down during the non-heating season.

[0027] A control method for a combined solar thermal and geothermal heating and domestic hot water system, characterized by comprising the following steps: The central control unit acquires seasonal operating conditions, temperature sensor readings, and heat load requirements, and divides the system into two core operating conditions: non-heating season and heating season. Operating conditions during the non-heating season: When the domestic hot water tank is heated to the set temperature by a flat plate collector, the user's domestic hot water needs are met. When the internal temperature of the domestic hot water tank reaches the cross-seasonal heat storage start-up temperature threshold and there is a surplus of heat, the buried pipe heat exchanger is activated to store the surplus solar heat in the underground soil. When solar energy is insufficient or at night, the central control unit turns on the electric heating boiler to supplement the heating of the domestic hot water tank; Under heating season operating conditions: Real-time monitoring of the fluid outlet temperature of the buried pipe heat exchanger; If the fluid outlet temperature is greater than or equal to the heating set threshold, the direct heating mode is entered: the buried pipe heat exchanger is controlled to directly supply heat to the hot water storage tank, and then supply heat to the heating terminal for heating. If the fluid outlet temperature is less than the heating set threshold, the system enters the heat pump auxiliary heating mode: the ground source heat pump unit is started to assist in heating; at the same time, the excess heat from the domestic hot water tank is introduced into the heating circulation loop to participate in heating.

[0028] Preferably, the heating temperature threshold is set according to the type of heating terminal: when the heating terminal adopts a floor radiant heating system, the heating temperature threshold is set to 35-40℃; when the heating terminal adopts a radiator, the heating temperature threshold is set to 50-60℃. The thermal storage start-up temperature threshold is set to 55-65℃.

[0029] Preferably, the solar collector circulation loop adopts temperature difference control logic: when the temperature difference between the fluid outlet of the flat plate collector and the domestic hot water tank is ≥10℃, the circulation pump on the solar collector circulation loop is started; when the temperature difference is <5℃, the circulation pump on the solar collector circulation loop is stopped.

[0030] Preferably, during the cross-seasonal heat storage process in the non-heating season, the central control unit also dynamically adjusts the speed of the circulating pump according to the change in the fluid outlet temperature of the buried pipe heat exchanger: when the fluid outlet temperature is higher than the soil equilibrium temperature, the circulation pump flow rate is increased; when the fluid outlet temperature is close to the soil equilibrium temperature, the circulation pump flow rate is reduced or heat storage is stopped.

[0031] Preferably, the central control unit also monitors the temperature of the hot water storage tank and the temperature of the heating return water in real time during the heating season. When the temperature difference between the two is less than the preset heating temperature difference threshold, the circulation flow is reduced.

[0032] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a solar thermal and geothermal coupled integrated energy system for heating and domestic hot water, and its control method. The system includes a flat-plate collector, a domestic hot water tank, an electric heating boiler, a coaxial tube-type buried pipe heat exchanger, a hot water storage tank, a ground source heat pump unit, heating terminals, and a central control unit. The flat-plate collector heats the domestic hot water tank, which is connected to both the electric heating boiler and the buried pipe heat exchanger. The buried pipe heat exchanger is connected to both the hot water storage tank and the ground source heat pump unit, and the hot water storage tank supplies heat to the heating terminals. The central control unit automatically switches the operating mode based on the season and temperature detection values: during the non-heating season, solar energy prioritizes domestic hot water supply, and excess heat is stored underground through the buried pipes across seasons while simultaneously replenishing the soil with heat; during the heating season, based on a comparison between the buried pipe outlet temperature and the heating threshold, the system automatically selects between direct heating through the buried pipes or auxiliary heating through the ground source heat pump, and introduces excess hot water from the domestic hot water tank into the heating circuit. This invention enables solar energy to store heat across seasons, solving the problem of seasonal mismatch in solar energy; it effectively alleviates the cold accumulation of soil caused by the long-term operation of ground source heat pumps through active summer heat replenishment; and it realizes integrated supply of heating and domestic hot water, improving energy utilization efficiency and system economy.

[0033] Furthermore, this invention utilizes a coaxial sleeve-type buried pipe heat exchanger to construct a large-capacity underground heat storage carrier. During the non-heating season (summer), excess solar heat collected by the flat plate collector is directly transported to the underground soil for storage through a domestic hot water tank, converting short-term transient heat energy into long-term underground energy storage. During the heating season, the stored heat is extracted from the soil for building heating, truly realizing cross-seasonal heat energy allocation for summer heat collection and winter heat use. This method overcomes the technical bottleneck of traditional solar energy systems, which can only store heat daily and cannot store heat across seasons, and solves the problem of temporal and spatial mismatch between excess solar energy resources in summer and insufficient solar energy resources in winter and peak heat load demand in northern regions. Furthermore, in cold regions where heating is the primary mode of supply, ground source heat pump systems extract heat from the ground during winter but release little or no heat to the ground during summer. This leads to a gradual decrease in underground soil temperature, resulting in a "cold accumulation" phenomenon. Cold accumulation not only causes a continuous drop in the outlet water temperature of the buried pipes but also leads to a decrease in the evaporation temperature of the heat pump unit, an increase in the compression ratio, and a decrease in the energy efficiency ratio. In severe cases, it may even cause the buried pipes to freeze. This application addresses this by storing heat underground during the non-heating season, which is essentially an active soil heat compensation process. The solar heat injected underground in summer can effectively raise or maintain the soil temperature level, thereby offsetting the heat deficit caused by winter heat extraction. This heat compensation method ensures that the heat extraction and heat release of the ground source heat pump system are balanced throughout the year, and the soil temperature can be maintained within a relatively stable range over a long period. This avoids the gradual accumulation of cold accumulation, ensures that the ground source heat pump unit operates at high efficiency for many years, and extends the overall service life of the system.

[0034] Furthermore, in existing technologies, heating systems and domestic hot water systems are often independent, each equipped with its own solar collectors, storage devices, and control systems. This not only results in high initial investment and large footprint but also hinders flexible heat allocation. This application organically integrates flat-plate solar collectors, domestic hot water tanks, storage tanks, buried pipe heat exchangers, and heating terminals into a single system architecture. This allows the solar collector loop to serve both domestic hot water heating and provide a heat source for inter-seasonal heat storage; the heating loop can receive heat directly from the buried pipes and can also draw excess heat from the domestic hot water tank when needed. This integrated design achieves heat sharing between the two heat loads: when there is excess heat in the domestic hot water tank and the heating loop requires heat, hot water can be introduced to the heating terminals via an electrically controlled valve; conversely, when the heating system is shut down during the non-heating season, all the heat generated by the solar collectors can be used to meet domestic hot water and inter-seasonal heat storage needs. This coordinated scheduling significantly improves energy efficiency, avoids redundant equipment configuration, and reduces the initial investment and footprint of the system.

[0035] Furthermore, this application includes a central control unit equipped with multiple temperature sensors to detect the temperatures at the collector outlet, the inside of the domestic hot water tank, the underground pipe outlet, and the storage tank. Based on the detected temperature data and the current season, the central control unit automatically determines the system's operating mode and accordingly controls the start / stop of each circulating pump, the on / off state of the electrically controlled valves, and the switching on / off state of the ground source heat pump unit. For example, during the non-heating season, when the domestic hot water tank temperature reaches the set value and there is still excess heat, the cross-seasonal heat storage mode is automatically activated. During the heating season, when the underground pipe outlet temperature is higher than the heating threshold, the direct heating mode is automatically adopted to save energy; when the underground pipe outlet temperature is lower than the heating threshold, the heat pump auxiliary heating mode is automatically activated to ensure heating effect. When there is excess hot water in the domestic hot water tank, it is automatically introduced into the heating circuit to participate in heating. All these switching operations require no manual intervention and are entirely autonomously decided by the central control unit based on real-time operating conditions, ensuring that the system always operates in an optimal state and greatly facilitating user operation.

[0036] Furthermore, the ground source heat pump unit in this application is not always operational, but rather serves as an auxiliary device to improve heating quality. For most of the heating season, as long as the outlet temperature of the buried pipe meets the water supply temperature requirements of the heating terminals, the system operates in direct heating mode. At this time, the heat pump unit is completely shut down, and the circulating pump drives the hot water in the buried pipe directly into the hot water storage tank and the heating terminals, resulting in extremely low energy consumption. Only when prolonged heat extraction causes the outlet temperature of the buried pipe to drop to a level that cannot directly meet heating demands will the heat pump unit automatically start, extracting low-grade heat energy from the circulating water in the buried pipe, upgrading its quality through a compressor, and then supplying it to the heating terminals. This design maximizes the direct heating capacity of geothermal energy while ensuring that heating quality is not affected by extreme weather or low soil temperatures after prolonged heat extraction through intermittent operation of the heat pump. Compared to traditional systems that constantly rely on heat pumps to raise the temperature, this solution significantly reduces the average annual operating energy consumption, and the reduced operating time of the heat pump unit also extends the equipment's lifespan. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0038] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below.

[0039] Figure 1 A schematic diagram of the overall structure of the integrated energy system for heating and domestic hot water coupling solar thermal and geothermal energy provided in this embodiment of the invention.

[0040] Figure 2 The system control logic block diagram provided in this embodiment of the invention.

[0041] Among them, the components are: 1 flat plate solar collector; 1-1 solar collector inlet; 1-2 solar collector outlet; 2 domestic hot water tank; 2-1 hot water tank inlet; 2-2 hot water tank outlet; 2-3 hot water supply port; 2-4 tap water inlet; 3 electric heating boiler; 3-1 boiler inlet; 3-2 boiler outlet; 3-3 power input interface; 4 coaxial tube buried pipe heat exchanger; 4-1 buried pipe inlet; 4-2 buried pipe outlet; 5 hot water storage tank; 5-1 heat storage tank inlet; 5-2 heat storage tank outlet; 6 ground source heat pump unit; 6-1 heat pump evaporator inlet; 6-2 heat pump evaporator outlet; 6-2 heat pump condenser inlet; and 6-3 heat pump condenser outlet. Outlet: 6-3; Heat pump condenser outlet: 6-4; Heating terminal: 7; Heating inlet: 7-1; Heating return outlet: 7-2; Central control unit: 8; First temperature sensor: 9-1; Second temperature sensor: 9-2; Third temperature sensor: 9-3; First circulation pump: 10-1; Second circulation pump: 10-2; Third circulation pump: 10-3; First electric control valve: 11-1; Second electric control valve: 11-2; Third electric control valve: 11-3; Fourth electric control valve: 11-4; Fifth electric control valve: 11-5; Sixth electric control valve: 11-6; Seventh electric control valve: 11-7; Eighth electric control valve: 11-8; Mains power grid: 12. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0043] Example 1 Figure 1 This is a schematic diagram of the overall structure of the integrated energy system for heating and domestic hot water coupling solar thermal and geothermal energy provided in an embodiment of the present invention. As shown in the figure, the integrated energy system includes: a flat plate collector 1, a domestic hot water tank 2, an electric heating boiler 3, a coaxial sleeve-type buried pipe heat exchanger 4, a hot water storage tank 5, a ground source heat pump unit 6, a heating terminal 7, a central control unit 8, a temperature sensor group, a circulating pump group, an electric control valve group, and a mains power grid 12.

[0044] 1. Flat plate solar collector 1 Flat-plate solar collector 1 is used to collect solar thermal energy and heat the circulating working fluid, including collector inlet 1-1 and collector outlet 1-2. Flat-plate solar collector 1 is a mature solar thermal utilization device, mainly composed of a transparent cover plate, absorber plate, insulation layer, and outer shell. The absorber plate surface is coated with a selective absorption coating with an absorptivity greater than 0.90 and an emissivity less than 0.10, enabling it to efficiently absorb solar radiation energy and transfer heat to the circulating working fluid flowing through it. Preferably, the total area of ​​flat-plate solar collector 1 is 20-100 square meters, determined according to the building's heat load requirements. The circulating working fluid can be water or antifreeze; in cold regions, an aqueous solution of ethylene glycol is preferred as the circulating working fluid to prevent freezing in winter.

[0045] 2. Domestic hot water tank 2 The domestic hot water tank 2 is used to store and supply domestic hot water, including a hot water tank inlet 2-1, a hot water tank outlet 2-2, a hot water supply port 2-3, and a tap water inlet 2-4. The domestic hot water tank 2 adopts a pressure-bearing stainless steel inner tank structure, with an external polyurethane foam insulation layer, the thickness of which is 50-80mm, and the temperature drop is less than 3℃ in 24 hours. The preferred tank volume is 200-500 liters, determined according to the user's domestic hot water needs. The hot water tank has an internal temperature stratification structure, with a high-temperature zone at the top and a low-temperature zone at the bottom. This stratification is achieved through a reasonable arrangement of the inlet and outlet, improving hot water utilization efficiency. The hot water tank inlet 2-1 is located at the bottom of the tank, receiving the heating medium from the flat plate collector 1; the hot water tank outlet 2-2 is located in the middle of the tank, used to supply hot water to the buried pipe heat exchanger 4; the hot water supply port 2-3 is located at the top of the tank, supplying high-temperature domestic hot water to users; and the tap water inlet 2-4 is located at the bottom of the tank, used to replenish water lost after use.

[0046] 3. Electric heating boiler The electric heating boiler 3 is used for auxiliary heating of the circulating working fluid, and includes a boiler inlet 3-1, a boiler outlet 3-2, and a power input interface 3-3. The electric heating boiler 3 uses electric heating tubes with a heating power of 6-15kW, and can be adjusted in multiple stages according to heat load requirements. As an auxiliary heat source, the electric heating boiler 3 starts up when solar energy is insufficient or at night to supplement the heating of the hot water tank, ensuring a stable supply of domestic hot water. The power input interface 3-3 is connected to the mains power grid 12 to obtain electrical energy. Preferably, the electric heating boiler 3 is equipped with safety devices such as overheat protection, leakage protection, and dry-burning protection to ensure safe system operation. The boiler inlet 3-1 is connected to the hot water tank outlet 2-2 of the domestic hot water tank 2 via a pipeline, and the boiler outlet 3-2 returns to the domestic hot water tank 2 via a pipeline, forming an auxiliary heating circulation loop.

[0047] 4. Coaxial sleeve type buried pipe heat exchanger The coaxial-tube buried heat exchanger 4 is installed underground for heat exchange with the soil, and includes a buried pipe inlet 4-1 and a buried pipe outlet 4-2. The coaxial-tube buried heat exchanger 4 adopts a coaxial-tube structure, consisting of an outer tube and an inner tube. The outer tube is made of high-density polyethylene (HDPE) with an outer diameter of 110-160 mm and a wall thickness of 6-10 mm, possessing good corrosion resistance and thermal conductivity. The inner tube is made of polybutene (PB) or cross-linked polyethylene (PEX) with an outer diameter of 40-63 mm and a wall thickness of 3-5 mm. The circulating working fluid enters from the buried pipe inlet 4-1, flows downward through the inner tube to the bottom of the buried pipe, and then flows upward through the annular space between the inner and outer tubes, exiting from the buried pipe outlet 4-2. During the downward flow, the working fluid exchanges heat with the surrounding soil, achieving heat storage or extraction.

[0048] Preferably, the burial depth of the underground pipe is 50-200 meters, more preferably 80-150 meters. The selection of the burial depth needs to comprehensively consider local geological conditions, soil thermal conductivity, and initial investment costs. The number of underground pipes is determined based on the building's heat load and the soil's heat exchange capacity, with a single-hole heat exchange power of 40-80 W / m. The spacing between underground pipes should not be less than 4 meters to avoid thermal interference. The backfill material around the underground pipes should be a bentonite-sand mixture or a special backfill material with a high thermal conductivity greater than 1.5 W / (m·K) to ensure good heat exchange performance.

[0049] 5. Hot water storage tank 5 The hot water storage tank 5 is used to store circulating hot water for heating, including a storage tank inlet 5-1 and a storage tank outlet 5-2. The hot water storage tank 5 acts as a buffer and stores energy, balancing supply and demand fluctuations in the heating system and improving system stability. The hot water storage tank 5 is made of carbon steel with anti-corrosion treatment on the inner wall and an external insulation layer. The preferred volume of the hot water storage tank is 500-2000 liters, determined according to the scale of the heating system. The hot water storage tank 5 is equipped with a baffle plate to optimize water flow distribution and reduce short-circuiting. The storage tank inlet 5-1 is located at the bottom of the tank, receiving the heating medium from the buried pipe heat exchanger 4 or the ground source heat pump unit 6; the storage tank outlet 5-2 is located at the top of the tank, delivering high-temperature hot water to the heating terminal 7.

[0050] 6. Ground source heat pump unit 6 The ground source heat pump unit 6 is used to increase the heating temperature when the outlet temperature of the buried pipe is insufficient. It includes a heat pump evaporator inlet 6-1, a heat pump evaporator outlet 6-2, a heat pump condenser inlet 6-3, and a heat pump condenser outlet 6-4. The ground source heat pump unit 6 mainly consists of a compressor, evaporator, condenser, expansion valve, and control system. When the outlet temperature of the buried pipe cannot directly meet the heating demand, the ground source heat pump unit 6 starts working. The low-temperature working fluid at the outlet of the buried pipe enters the heat pump evaporator. The refrigerant absorbs heat from the working fluid in the evaporator and evaporates into a gaseous state. The gaseous refrigerant is compressed by the compressor, and its temperature and pressure increase. The high-temperature and high-pressure gaseous refrigerant enters the condenser, releases heat to the heating circulating water, and condenses into a liquid state. The liquid refrigerant is throttled and depressurized by the expansion valve and then re-enters the evaporator, completing one cycle.

[0051] Preferably, the heating capacity of the ground source heat pump unit 6 is 10-50kW, and the coefficient of performance (COP) is greater than 4.0. The compressor uses a scroll or screw compressor, characterized by stable operation and low noise. The refrigerant is preferably environmentally friendly R410A or R134a. The heat pump unit is equipped with safety devices such as high and low pressure protection, exhaust temperature protection, and antifreeze protection.

[0052] 7. Heating terminal 7 The heating terminal 7 is used to provide heating services to users, including a heating inlet 7-1 and a heating return outlet 7-2. The heating terminal 7 can be in the form of a floor radiant heating system, radiators, or fan coil units. A floor radiant heating system is preferred, with a supply water temperature of 35-45℃, a return water temperature of 30-35℃, and a temperature difference of 5-10℃. Floor radiant heating systems offer advantages such as high comfort and good energy efficiency, and the lower supply water temperature requirement helps improve the energy efficiency ratio of the ground source heat pump system. The heating inlet 7-1 connects to the heat storage tank outlet 5-2 of the hot water storage tank 5 to receive heating hot water; the heating return outlet 7-2 returns the hot water to the hot water storage tank 5 or the buried pipe heat exchanger 4 through a pipeline, forming a heating circulation loop.

[0053] 8. Central Control Unit The central control unit 8 is used to switch the system between various operating modes based on seasonality, temperature detection values, and heat load requirements. The central control unit 8 can be implemented using a programmable logic controller (PLC) or a dedicated building automation system, and has functions such as data acquisition, logic operation, control output, and human-machine interaction. The central control unit 8 is electrically connected to various temperature sensors, circulating pumps, electrically controlled valves, and heat pump units, collecting system operating parameters in real time and issuing control commands according to preset control strategies to achieve automated system operation. The central control unit 8 also has fault diagnosis and alarm functions, promptly alerting users when system anomalies occur.

[0054] 9. Temperature sensor group The temperature sensor array is used to detect the temperature at various critical locations within the system, providing decision-making information for the central control unit 8. The temperature sensor array includes: The first temperature sensor 9-1 is located at the collector outlet 1-2 and is used to detect the working fluid temperature T1 at the collector outlet. The second temperature sensor 9-2 is installed inside the domestic hot water tank 2 to detect the water temperature T2 inside the hot water tank; The third temperature sensor 9-3 is installed at the outlet 4-2 of the buried pipe and is used to detect the working fluid temperature T3 at the outlet of the buried pipe. Preferably, a fourth temperature sensor 9-4 can also be provided, which is installed inside the hot water storage tank 5, to detect the temperature T4 of the hot water storage tank; and a fifth temperature sensor 9-5 can be provided at the heating return water inlet 7-2 to detect the heating return water temperature T5.

[0055] The temperature sensor uses a platinum resistance temperature sensor (Pt100 or Pt1000) or a thermocouple, with a measurement accuracy of ±0.5℃ and a response time of less than 10 seconds.

[0056] 10. Circulating pump set The circulating pump set is used to drive the flow of the working fluid in each circulating loop of the system, including: The first circulation pump 10-1 is installed on the pipeline between the collector outlet 1-2 and the hot water tank inlet 2-1 to drive the solar collector circulation; The second circulation pump 10-2 is installed on the pipeline between the hot water tank outlet 2-2 and the buried pipe inlet 4-1, and is used to drive the cross-seasonal thermal storage circulation. The third circulation pump 10-3 is installed on the pipeline between the heat storage tank outlet 5-2 and the heating inlet 7-1, and is used to drive the heating circulation.

[0057] The circulating pump is a variable frequency circulating pump or a multi-stage speed-regulating circulating pump, which can adjust the speed according to the system flow requirements to achieve energy-saving operation. The flow rate of the circulating pump is 1-5 m³ / h, and the head is 5-15 m, which is determined according to the system resistance and flow requirements.

[0058] 11. Electrically controlled valve assembly Electrically controlled valve assemblies are used to control the on / off state of various pipelines in the system, enabling switching between different operating modes, including: The first electrically controlled valve 11-1 is located between the collector outlet 1-2 and the hot water tank inlet 2-1 to control the on / off state of the solar collector circuit. The second electrically controlled valve 11-2 is located between the hot water tank outlet 2-2 and the buried pipe inlet 4-1 to control the on / off of the cross-seasonal heat storage circuit. The third electric control valve 11-3 is installed between the boiler inlet 3-1 and the domestic hot water tank 2 to control the on / off of the electric heating auxiliary circuit; The fourth electrically controlled valve 11-4 is located between the underground pipe outlet 4-2 and the heat storage box inlet 5-1 to control the on / off of the direct heating circuit. The fifth electrically controlled valve 11-5 is located between the outlet 5-2 of the heat storage tank and the heating inlet 7-1 to control the on / off of the heating circuit; The sixth electric control valve 11-6 is located between the underground pipe outlet 4-2 and the heat pump evaporator inlet 6-1 to control the on / off state of the heat pump evaporator side circuit. The seventh solenoid valve 11-7 is located between the heat pump condenser outlet 6-4 and the heat storage tank inlet 5-1 to control the on / off state of the heat pump condenser side circuit. The eighth electrically controlled valve 11-8 is installed between the domestic hot water tank 2 and the heating terminal 7, and is used to introduce excess hot water from the domestic hot water tank into the heating circuit during the heating season.

[0059] The electrically controlled valve is either a two-way or three-way valve, with a valve body made of brass or stainless steel, providing excellent sealing performance. The valve's opening and closing time is 10-30 seconds, offering a fast response.

[0060] In a second aspect, this invention also provides a control method for an integrated energy system for heating and domestic hot water that couples solar thermal and geothermal energy. For example... Figure 2 The diagram shown is a system control logic block diagram provided in an embodiment of the present invention.

[0061] Non-heating season domestic hot water supply mode: During the non-heating season, flat-plate solar collector 1 collects solar thermal energy to heat the water in domestic hot water tank 2. When the hot water tank temperature reaches the set domestic hot water temperature, users can obtain domestic hot water through hot water supply outlets 2-3. When solar energy is insufficient or at night, the electric heating boiler 3 is turned on for supplementary heating.

[0062] Non-heating season cross-seasonal heat storage mode: During the non-heating season, when the temperature of the domestic hot water tank 2 exceeds the heat storage start-up temperature threshold and there is a surplus of hot water, the central control unit 8 activates the second circulation pump 10-2 and the second electrically controlled valve 11-2 to introduce hot water into the coaxial sleeve-type buried pipe heat exchanger 4. As the hot water flows in the buried pipe, it transfers heat to the surrounding soil through the pipe wall, achieving underground storage of thermal energy. This process has a dual function: firstly, it achieves cross-seasonal heat storage, storing surplus solar thermal energy from summer underground for winter use; secondly, it replenishes heat to the underground soil, effectively alleviating the problem of cold soil accumulation caused by the long-term operation of the ground source heat pump.

[0063] Direct heating mode during the heating season: During the heating season, when the outlet temperature of the buried pipe is greater than or equal to the heating temperature threshold, it indicates that the geothermal energy is sufficient and can directly meet the heating demand. At this time, the fourth electric control valve 11-4, the fifth electric control valve 11-5, and the third circulation pump 10-3 are opened, and the hot water at the outlet of the buried pipe heat exchanger 4 flows directly into the hot water storage tank 5 and is sent to the heating terminal 7 for heating.

[0064] Heat pump assisted heating mode during the heating season: During the heating season, when the outlet temperature of the buried pipe is lower than the heating temperature threshold, it indicates that the geothermal temperature can no longer directly meet the heating demand. At this time, the central control unit 8 closes the fourth electric control valve 11-4 and opens the sixth electric control valve 11-6, the seventh electric control valve 11-7, and the ground source heat pump unit 6. The hot water at the outlet of the buried pipe heat exchanger 4 first extracts heat through the heat pump evaporator, is then heated by the heat pump condenser, and sent to the hot water storage tank 5 before being supplied to the heating terminal 7.

[0065] Hot water-assisted heating mode during the heating season: During the heating season, when there is excess hot water in the domestic hot water tank 2, the central control unit 8 opens the eighth electrically controlled valve 11-8 to introduce the excess hot water into the heating circuit to participate in heating. Unlike the non-heating season, the excess hot water is no longer stored underground, but is directly used for the heating load.

[0066] This invention organically couples a solar thermal system with a geothermal system, utilizing buried pipes to achieve cross-seasonal heat storage, thus solving two major technical challenges: seasonal mismatch of solar energy and cold accumulation of geothermal energy. The system can meet both domestic hot water and heating needs, and through intelligent control, it automatically switches between various operating modes, improving energy efficiency and user experience.

[0067] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0068] Example 1 Please refer to Figure 1 This embodiment provides a comprehensive energy system for heating and domestic hot water that couples solar thermal and geothermal energy. The system includes: a flat plate collector 1, a domestic hot water tank 2, an electric heating boiler 3, a buried pipe heat exchanger 4, a hot water storage tank 5, a ground source heat pump unit 6, heating terminals 7, and a central control unit 8.

[0069] The system includes: a flat-plate solar collector for collecting solar thermal energy and heating the circulating working fluid; a domestic hot water tank for storing and supplying domestic hot water; an electric boiler for auxiliary heating of the circulating working fluid; a coaxial sleeve-type buried pipe heat exchanger buried underground for heat exchange with the soil; a hot water storage tank for storing circulating heating hot water; a ground source heat pump unit for increasing the heating temperature when the outlet temperature of the buried pipe is insufficient; heating terminals for providing heating services to users; and a central control unit for controlling the system to switch between various operating modes based on season, temperature detection values, and heat load demand, specifically including: Solar thermal collector circulation loop: The outlet 1-2 of the flat plate collector 1 is connected to the inlet 2-1 of the domestic hot water tank 2 via a pipeline, and the outlet 2-2 of the domestic hot water tank 2 is connected to the inlet 1-1 of the flat plate collector 1 via a pipeline. A first circulation pump 10-1 and a first electrically controlled valve 11-1 are installed in this loop. This loop is used to transfer the solar thermal energy collected by the flat plate collector 1 to the domestic hot water tank 2 to heat the domestic hot water therein.

[0070] Domestic hot water auxiliary heating circuit: The outlet 2-2 of the domestic hot water tank 2 is connected to the inlet 3-1 of the electric heating boiler 3 via a pipeline, and the outlet 3-2 of the electric heating boiler 3 returns to the top of the domestic hot water tank 2 via a pipeline. A third electrically controlled valve 11-3 is installed in this circuit. When solar energy is insufficient or at night, the central control unit 8 turns on the electric heating boiler 3 to supplement the heating of the water in the domestic hot water tank 2, ensuring the continuity of domestic hot water supply.

[0071] Cross-seasonal heat storage / replenishment circuit: The outlet 2-2 of the domestic hot water tank 2 is connected to the inlet 4-1 of the buried pipe heat exchanger 4 via a pipeline, and the outlet 4-2 of the buried pipe heat exchanger 4 returns to the middle of the domestic hot water tank 2 via a pipeline. A second circulation pump 10-2 and a second electrically controlled valve 11-2 are installed on this circuit. During the non-heating season, when the domestic hot water tank 2 has excess heat, the central control unit 8 controls the circuit to open, allowing the excess solar thermal energy to be introduced into the buried pipe heat exchanger 4 and stored in the underground soil.

[0072] Heating circulation loop: The outlet 5-2 of the hot water storage tank 5 is connected to the inlet 7-1 of the heating terminal 7 via a pipeline, and the return water outlet 7-2 of the heating terminal 7 returns to the inlet 5-1 of the hot water storage tank 5 via a pipeline. A fifth electrically controlled valve 11-5 and a third circulation pump 10-3 are installed on this loop. This loop is used to provide heating services to users.

[0073] Direct heating circuit: The outlet 4-2 of the buried pipe heat exchanger 4 is connected to the inlet 5-1 of the hot water storage tank 5 via a pipeline, and a fourth electrically controlled valve 11-4 is installed on this pipeline. During the heating season, when the outlet temperature of the buried pipe is sufficient, the central control unit 8 opens the fourth electrically controlled valve 11-4 to directly deliver geothermal energy to the hot water storage tank 5 for heating.

[0074] Auxiliary heating circuit for the heat pump: The outlet 4-2 of the buried pipe heat exchanger 4 is connected to the evaporator inlet 6-1 of the ground source heat pump unit 6 via a pipeline, and the evaporator outlet 6-2 returns to the buried pipe inlet 4-1 via a pipeline. The condenser outlet 6-4 of the ground source heat pump unit 6 is connected to the inlet 5-1 of the hot water storage tank 5 via a pipeline, and the condenser inlet 6-3 draws water from the bottom of the hot water storage tank 5 via a pipeline. This circuit is equipped with a sixth solenoid valve 11-6 and a seventh solenoid valve 11-7. When the temperature at the buried pipe outlet is insufficient, the central control unit 8 starts the ground source heat pump unit 6 to raise the heating temperature and supply it to the hot water storage tank 5.

[0075] Control Connections: The signal terminals of the central control unit 8 are connected to the flat plate solar collector 1, the second temperature sensor 9-2 in the domestic hot water tank 2, the electric heating boiler 3, the buried pipe heat exchanger 4, the hot water storage tank 5, the ground source heat pump unit 6, each electrically controlled valve (11-1 to 11-8), and each circulating pump (10-1, 10-2, 10-3). The central control unit 8 is configured to automatically switch the system's operating mode according to seasonal conditions (heating season / non-heating season), the detection values ​​of each temperature sensor, and the heat load demand, thereby realizing the integrated supply of heating and domestic hot water and the cross-seasonal storage of solar energy.

[0076] In a further preferred embodiment, the specific structure of the buried pipe heat exchanger 4 was optimized.

[0077] Please refer to Figure 1 The diagram shows a partial structural schematic of the buried pipe heat exchanger 4. The buried pipe heat exchanger 4 adopts a coaxial sleeve-type bidirectional convection heat exchange structure, specifically including: an outer pipe vertically buried in the soil, and an inner pipe coaxially nested inside the outer pipe. A sealed annular heat exchange gap is formed between the inner wall of the outer pipe and the outer wall of the inner pipe.

[0078] The upper end of the inner pipe forms the buried pipe inlet 4-1, and the lower end of the inner pipe is an open structure that extends to the bottom of the outer pipe. The bottom of the outer pipe is a closed end, allowing fluid communication between the lower end of the inner pipe and the annular heat exchange gap at the bottom. The upper end of the outer pipe and the upper end of the inner pipe form the buried pipe outlet 4-2.

[0079] The heat exchange medium (antifreeze in winter, or water or antifreeze in summer) enters the inner pipe through the inlet 4-1 of the buried pipe and flows vertically downwards along the inner pipe to the bottom of the outer pipe. After reversing direction at the bottom, the medium enters the annular heat exchange gap and flows vertically upwards along the annular gap back to the outlet 4-2 of the buried pipe. This flow path forms a unidirectional counter-current heat exchange path, where the medium exchanges heat with the soil in both the downward and upward processes, significantly improving the heat exchange efficiency per unit well depth.

[0080] Preferably, the burial depth of the underground pipe is 50-200 meters. For heating projects in North China, the preferred burial depth is 80-120 meters; for cold regions in Northeast China, the preferred burial depth is 120-150 meters. The outer pipe is made of high-density polyethylene (HDPE) with an outer diameter of 110-160 mm; the inner pipe is made of polybutene (PB) with an outer diameter of 40-63 mm.

[0081] In a further preferred embodiment, the specific arrangement of the temperature sensor group is defined.

[0082] Please refer to Figure 1 The temperature sensor group includes: First temperature sensor 9-1: Located at the fluid outlet 1-2 of the flat plate solar collector 1, used to detect the working fluid temperature T1 at the solar collector outlet in real time.

[0083] The second temperature sensor 9-2 is located inside the domestic hot water tank 2, preferably in the upper middle part of the tank, and is used to detect the water temperature T2 inside the tank. This temperature is a key parameter for determining whether the domestic hot water supply is sufficient and whether to activate the inter-seasonal heat storage system.

[0084] The third temperature sensor 9-3 is located at the fluid outlet 4-2 of the buried pipe heat exchanger 4 and is used to detect the working fluid temperature T3 at the outlet of the buried pipe. This temperature is the core criterion for determining whether direct heating or heat pump-assisted heating is used during the heating season.

[0085] The fourth temperature sensor 9-4 is located inside the hot water storage tank 5 and is used to detect the temperature T4 of the hot water storage tank for the control of the heating cycle.

[0086] The signal output terminals of each temperature sensor are electrically connected to the signal input terminals of the central control unit 8. The central control unit 8 collects the values ​​of T1, T2, T3, and T4 in real time, which serve as the basis for switching operating modes and adjusting the speed of the circulating pump.

[0087] A further preferred embodiment further specifies that each circulation loop is equipped with an independent circulation pump and an electrically controlled valve. The central control unit 8 switches between four core operating modes by adjusting the circulation pump speed and the on / off state of the electrically controlled valve. Specifically: Non-heating season cross-seasonal heat storage mode: turn on the second circulation pump 10-2 and the second electric control valve 11-2, close other irrelevant valves, and pass the excess hot water in the domestic hot water tank 2 into the buried pipe heat exchanger 4 to store heat underground.

[0088] Direct heating mode during the heating season: Open the fourth electric control valve 11-4, the fifth electric control valve 11-5 and the third circulation pump 10-3, close the sixth electric control valve 11-6, the seventh electric control valve 11-7 and the ground source heat pump unit 6, and the hot water from the buried pipe outlet directly enters the hot water storage tank 5 and the heating terminal 7.

[0089] During the heating season, the heat pump-assisted heating mode is as follows: the fourth electric control valve 11-4 is closed, the sixth electric control valve 11-6, the seventh electric control valve 11-7 and the ground source heat pump unit 6 are opened, and the hot water from the buried pipe outlet is first heated by the heat pump before entering the hot water storage tank 5.

[0090] Hot water auxiliary heating mode during the heating season: Open the eighth electric control valve 11-8 (this valve is located between the domestic hot water tank 2 and the heating circuit) to directly introduce the excess hot water in the domestic hot water tank 2 into the heating circuit to participate in the heating.

[0091] The central control unit 8 automatically switches between the above modes according to the real-time operating conditions.

[0092] One of the further preferred embodiments optimizes the internal structure of the domestic hot water tank 2 and the storage hot water tank 5, as well as the operation strategy of the ground source heat pump unit 6.

[0093] The domestic hot water tank 2 features a temperature stratification structure: The tank is internally equipped with vertically arranged stratified flow guiding components, a bottom cold water distributor, and an upper hot water collector. These components divide the tank along its height, creating multiple temperature gradient chambers. This results in a stable temperature stratification of the water within the tank, with an upper high-temperature zone (reaching 55-65℃) and a lower low-temperature zone (approximately 10-15℃, close to the tap water inlet temperature). This effectively suppresses the mixing of hot and cold water and improves hot water utilization efficiency.

[0094] The internal structure of the hot water storage tank 5: Multiple sets of vertical guide plates are evenly arranged along the height direction on the inner wall of the hot water storage tank 5. The guide plates are provided with flow stabilizing holes, and a meandering water flow channel is formed between adjacent guide plates. This structure can optimize the flow distribution of heating circulating water in the hot water storage tank, reduce short-circuiting, and improve heat storage and heat release efficiency.

[0095] Operating strategy of ground source heat pump unit 6: Ground source heat pump unit 6 is configured as an auxiliary heating device, only starting during the heating season when the outlet temperature T3 of the buried pipe heat exchanger 4 is below the heating threshold (e.g., 35°C). During the non-heating season, ground source heat pump unit 6 is completely shut down to save energy. This strategy avoids the operation of the heat pump under unnecessary conditions, improving the overall energy efficiency of the system.

[0096] This embodiment provides a control method for the aforementioned integrated energy system combining solar thermal and geothermal heating with domestic hot water. Please refer to... Figure 2 The control logic block diagram shown indicates that the method includes the following steps: Step 1: Operating Condition Identification The central control unit 8 determines whether the current season is the heating season or the non-heating season based on the calendar time or the outdoor temperature sensor.

[0097] Step 2: Operating Condition Control during Non-Heating Season If it is currently the non-heating season, the following control strategies will be implemented: Domestic hot water supply: The central control unit 8 controls the operation of the solar thermal collector circulation loop. When the temperature difference ΔT between T1 detected by the first temperature sensor 9-1 and T2 detected by the second temperature sensor 9-2 is ≥ 10℃, the first circulation pump 10-1 is activated, and the flat plate collector 1 heats the domestic hot water tank 2. When the temperature T2 of the domestic hot water tank 2 reaches the set domestic hot water temperature (e.g., 50℃), the user can obtain domestic hot water through the hot water supply port 2-3.

[0098] Auxiliary heating: When solar energy is insufficient (such as on cloudy or rainy days) or at night, the central control unit 8 turns on the electric heating boiler 3 to supplement the heating of the domestic hot water tank 2, ensuring that T2 is not lower than 40℃.

[0099] Cross-seasonal heat storage: When the internal temperature T2 of the domestic hot water tank 2 is ≥ 55℃ (the heat storage start-up temperature threshold) and there is a surplus of heat (i.e., the domestic hot water demand has been met and T2 continues to be higher than the set value), the central control unit 8 starts the second circulation pump 10-2 and opens the second electric control valve 11-2 to store the surplus solar heat in the underground soil through the buried pipe heat exchanger 4.

[0100] Step 3: Operating Condition Control during the Heating Season If it is currently the heating season, the following control strategies will be implemented: Real-time monitoring of buried pipe outlet temperature: The central control unit 8 reads the buried pipe outlet temperature T3 in real time through the third temperature sensor 9-3.

[0101] Mode determination: Compare T3 with the heating set threshold (e.g., 35°C for floor radiant heating system and 50°C for radiator system).

[0102] Direct heating mode: If T3 ≥ the heating set threshold, it indicates sufficient geothermal energy. The central control unit 8 shuts down the ground source heat pump unit 6, opens the fourth solenoid valve 11-4 and the fifth solenoid valve 11-5, and starts the third circulation pump 10-3. The hot water from the outlet of the buried pipe heat exchanger 4 flows directly into the hot water storage tank 5, and then supplies the heating terminal 7 for heating.

[0103] Heat pump assisted heating mode: If T3 < heating set threshold, it means that the geothermal temperature can no longer directly meet the heating demand. The central control unit 8 controls the closure of the fourth solenoid valve 11-4, and opens the sixth solenoid valve 11-6 and the seventh solenoid valve 11-7, starting the ground source heat pump unit 6. The hot water from the buried pipe outlet first flows through the evaporator of the ground source heat pump unit 6, where it is cooled and returned to the ground after heat is extracted; the heat pump condenser side heats the heating return water to the set temperature (e.g., 40-45℃) and sends it into the hot water storage tank 5, and then supplies it to the heating terminal 7.

[0104] Hot water-assisted heating: During the heating season, the central control unit 8 monitors the temperature T2 of the domestic hot water tank 2 in real time. When T2 ≥ 45℃ and the demand for domestic hot water is low, the central control unit 8 opens the eighth electric control valve 11-8 to directly introduce the excess heat in the domestic hot water tank 2 into the heating circulation loop to participate in heating, thereby realizing the cascade utilization of heat.

[0105] In one of the further preferred embodiments, this embodiment specifies a particular numerical value for the key temperature threshold.

[0106] Heating setting threshold: set according to the type of heating terminal 7.

[0107] When the heating terminal 7 adopts a floor radiant heating system, the heating set threshold is set to 35-40℃, preferably 35℃. Floor radiant heating systems are characterized by low-temperature heating and high thermal comfort; a water supply temperature of 35℃ is sufficient to meet the heating needs of most buildings.

[0108] When the heating terminal 7 uses a radiator, the heating set threshold is set to 50-60℃, preferably 55℃. Radiators require a higher supply water temperature to ensure sufficient heat dissipation.

[0109] Thermal storage start-up temperature threshold: set at 55-65℃, preferably 60℃. When the temperature of domestic hot water tank 2 reaches above 60℃, it indicates that solar energy is sufficient and domestic hot water demand is saturated. At this time, starting inter-seasonal thermal storage is the most economical. Thermal storage should not be started when the temperature is below 55℃ to avoid excessive heat loss.

[0110] In one of the further preferred embodiments, this embodiment defines the specific control logic of the solar thermal collector circulation loop.

[0111] The solar thermal collector circulation loop uses temperature difference control logic: Start-up conditions: When the temperature difference ΔT = T1 - T2 between the fluid outlet temperature T1 detected by the first temperature sensor 9-1 and the temperature T2 detected by the second temperature sensor 9-2 in the domestic hot water tank 2 is ≥ 10℃, the central control unit 8 issues a command to start the first circulation pump 10-1 in the solar thermal collector circulation loop and simultaneously open the first electrically controlled valve 11-1. At this time, the solar energy absorbed by the flat plate collector 1 is effectively transferred to the domestic hot water tank 2.

[0112] Stop condition: When the temperature difference ΔT < 5℃, it indicates that the heat absorbed by the collector can no longer be effectively transferred (possibly due to weakened sunlight or high water tank temperature). The central control unit 8 issues a command to stop the first circulation pump 10-1 and close the first electric control valve 11-1 to avoid the circulation pump operating ineffectively and wasting electrical energy.

[0113] The temperature difference control logic has a 5°C hysteresis between its start and stop thresholds, which can effectively prevent frequent start and stop of the circulating pump and extend the equipment's lifespan.

[0114] As a further preferred embodiment, this example specifies the refined control of the cross-seasonal heat storage process during the non-heating season.

[0115] During the inter-seasonal heat storage process in the non-heating season, the central control unit 8 also uses a variable frequency control strategy to adjust the speed of the second circulation pump 10-2 based on the dynamic change of the fluid outlet temperature T3 of the buried pipe heat exchanger 4: Enhanced thermal storage stage: When the outlet temperature T3 of the buried pipe detected by the third temperature sensor 9-3 is significantly higher than the soil equilibrium temperature (e.g., T3 ≥ 35℃, while the soil equilibrium temperature is approximately 15-18℃), it indicates a strong driving force for thermal storage. The central control unit 8 controls the second circulation pump 10-2 to operate at its rated speed or a higher speed (e.g., 80%-100% of the rated speed) to increase the circulation flow rate and rapidly inject more solar heat into the ground.

[0116] Reduced / Stopped Heat Storage Stage: When T3 gradually decreases and approaches the soil equilibrium temperature (e.g., T3 ≤ 25℃), it indicates that the underground soil is nearing thermal saturation, and the efficiency of continued heat storage decreases. The central control unit 8 controls the reduction of the speed of the second circulation pump 10-2 (e.g., to 30%-50% of the rated speed) to reduce the circulation flow rate. When the difference between T3 and the soil equilibrium temperature is less than 2℃, the central control unit 8 stops the second circulation pump 10-2, closes the second electrically controlled valve 11-2, and terminates the heat storage process.

[0117] This control strategy can effectively prevent excessively high underground temperatures caused by excessive heat storage, while also saving on the power consumption of the circulating pump.

[0118] In one of the further preferred embodiments, this embodiment optimizes the heating cycle control during the heating season.

[0119] The central control unit 8 monitors the temperature T4 of the hot water storage tank 5 in real time during the heating season (via the fourth temperature sensor 9-4) and the heating return water temperature T5 (a fifth temperature sensor 9-5 can be set at the heating return water inlet 7-2).

[0120] The central control unit 8 calculates the temperature difference between the heating supply water and the return water. This temperature difference reflects the heat dissipation demand of heating terminal 7.

[0121] when When the temperature difference is less than the preset heating temperature difference threshold (for example, for a floor radiant heating system, this threshold can be set to 5°C), it indicates that the building's heat load is small and the terminal heat dissipation capacity is limited. Excessive circulation flow will increase the energy consumption of the water pump.

[0122] At this time, the central control unit 8 issues a command to reduce the speed of the third circulation pump 10-3, reduce the flow rate of the heating circulation, maintain the stable heat dissipation of the heating terminal 7, and at the same time reduce the power consumption of the circulation pump.

[0123] Conversely, when When the load exceeds the threshold, it indicates a large heat load. The central control unit 8 then increases the speed of the third circulation pump 10-3 to increase the circulation flow and ensure the heating effect.

[0124] This variable frequency control strategy can achieve on-demand heating, further reducing the system's operating energy consumption.

[0125] This invention provides a combined solar thermal and geothermal energy system for heating and domestic hot water supply, and its control method, aiming to solve the technical problems of seasonal mismatch of solar energy, cold accumulation of geothermal energy, and incoordination of heating and domestic hot water supply in existing technologies. The beneficial effects of the embodiments of this invention include: (1) Cross-seasonal heat storage: The excess solar heat energy in summer is stored underground through buried pipes and used in winter, which solves the problem of seasonal mismatch of solar energy.

[0126] (2) Improve cold accumulation: In summer, the ground heat pump can effectively alleviate the problem of soil cold accumulation caused by long-term operation of the ground source heat pump, and ensure the long-term stable operation of the system.

[0127] (3) Integrated heating and water supply: The system simultaneously meets the heat load requirements of both heating and domestic hot water, thus improving energy utilization efficiency.

[0128] (4) Intelligent control: The central control unit automatically switches the operating mode according to temperature detection and seasonal changes to achieve optimized operation of the system.

[0129] (5) Heat pump assistance: When the geothermal temperature is insufficient, the heat pump is activated to increase the temperature, ensure the heating quality, and maximize the use of geothermal energy.

[0130] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0131] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0132] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixation," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. When a component is said to be "fixed to" another component, it can be directly on the other component or there may be an intervening component. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intervening component. When a component is considered to be "set on" another component, it can be directly set on the other component or there may be an intervening component.

[0133] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0134] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0135] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A comprehensive energy system for heating and domestic hot water supply, co-coupled with solar thermal and geothermal energy, characterized in that, include: Flat plate heat exchanger (1), domestic hot water tank (2), electric heating boiler (3), buried pipe heat exchanger (4), hot water storage tank (5), ground source heat pump unit (6), heating terminal (7) and central control unit (8); The outlet of the flat plate collector (1) is connected to the inlet of the domestic hot water tank (2) to form a solar thermal circulation loop; The outlet of the domestic hot water tank (2) is connected to the inlet of the electric heating boiler (3) and the inlet of the buried pipe heat exchanger (4) respectively. The outlet of the electric heating boiler (3) flows back to the domestic hot water tank (2) to form a domestic hot water auxiliary heating circuit. The outlet of the buried pipe heat exchanger (4) is connected to the inlet of the hot water storage tank (5) and the evaporator inlet of the ground source heat pump unit (6), respectively. The condenser outlet of the ground source heat pump unit (6) is connected to the inlet of the hot water storage tank (5). The outlet of the hot water storage tank (5) is connected to the inlet of the heating terminal (7). The outlet of the heating terminal (7) flows back to the hot water storage tank (5), forming a heating circulation loop. The signal terminals of the central control unit (8) are respectively connected to the flat plate collector (1), the domestic hot water tank (2), the electric heating boiler (3), the buried pipe heat exchanger (4), the hot water storage tank (5), the ground source heat pump unit (6), the electric control valves and circulation pumps of each circulation loop. The central control unit (8) is configured to switch the system operation mode according to the seasonal operating conditions, temperature parameters and heat load requirements, so as to realize the integrated supply of heating and domestic hot water and the cross-seasonal solar energy storage.

2. The solar energy heat and geothermal heat coupled heating and domestic hot water comprehensive energy system according to claim 1, characterized in that, The buried pipe heat exchanger (4) adopts a bidirectional convection heat exchange structure with the inner pipe guiding the flow downward and the annular heat exchange gap returning the flow upward, including an outer pipe and an inner pipe; the outer pipe and the inner pipe are arranged coaxially and nested, the inner pipe is housed inside the cavity of the outer pipe, and a sealed annular heat exchange gap is formed between the outer wall of the inner pipe and the inner wall of the outer pipe. The upper end of the inner tube forms the inlet (4-1) of the buried pipe, and the lower end of the inner tube is an open structure that extends to the bottom of the outer tube. The bottom of the outer tube is a closed end, allowing the lower end of the inner tube to be in fluid communication with the annular heat exchange gap at the bottom. The upper end of the outer pipe and the upper end of the inner pipe form the underground pipe outlet (4-2). The heat exchange medium enters the inner pipe through the inlet (4-1) of the buried pipe and flows vertically downward along the inner pipe. It then changes direction at the bottom of the outer pipe and enters the annular heat exchange gap. It flows vertically upward along the annular heat exchange gap back to the outlet (4-2) of the buried pipe, forming a unidirectional counter-current heat exchange path. The burial depth of the buried pipe is 50-200 meters.

3. The solar energy heat and geothermal heat coupled heating and domestic hot water comprehensive energy system according to claim 1, characterized in that, It also includes a temperature sensor group, which comprises: The first temperature sensor (9-1) is located at the fluid outlet of the flat plate collector (1), the second temperature sensor (9-2) is located inside the domestic hot water tank (2), the third temperature sensor (9-3) is located at the fluid outlet of the buried pipe heat exchanger (4), and the fourth temperature sensor (9-4) is located inside the hot water storage tank (5). The signal output terminals of each temperature sensor are electrically connected to the signal input terminals of the central control unit (8).

4. The solar energy heat and geothermal heat coupled heating and domestic hot water comprehensive energy system according to claim 1, characterized in that, The solar thermal collection circulation loop, the domestic hot water auxiliary heating loop and the heating circulation loop are all equipped with circulation pumps and electric control valves. The central control unit (8) can switch between modes such as cross-seasonal heat storage in the non-heating season, direct heating in the heating season, heat pump auxiliary heating in the heating season and hot water auxiliary heating in the heating season by adjusting the speed of the circulation pump and the on / off state of the electric control valve.

5. The solar energy heat and geothermal heat coupled heating and domestic hot water comprehensive energy system according to claim 1, characterized in that, The domestic hot water tank (2) is equipped with a temperature stratification structure, including: a vertically arranged stratified flow guide component, a bottom cold water distributor and an upper hot water collector; the stratified flow guide component is divided into multiple temperature gradient chambers along the height of the tank, so that the water in the tank forms a stable temperature stratification of an upper high temperature zone and a lower low temperature zone, and suppresses the mixing of cold and hot water. Multiple sets of vertical guide plates are evenly arranged along the height direction on the inner wall of the hot water storage tank (5). The guide plates are provided with flow stabilizing holes, and a meandering water flow channel is formed between adjacent guide plates. The ground source heat pump unit (6) is an auxiliary heating device that is only started when the outlet temperature of the buried pipe heat exchanger (4) is lower than the heating threshold during the heating season and is completely shut down during the non-heating season.

6. A control method for the solar-geothermal coupled heat supply and domestic hot water integrated energy system according to any one of claims 1 to 5, characterized in that, Includes the following steps: The central control unit (8) acquires seasonal operating conditions, the detection values ​​of each temperature sensor and the heat load demand, and divides the core operating conditions into two types: non-heating season and heating season. Operating conditions during the non-heating season: When the domestic hot water tank (2) is heated by the flat plate collector (1) to reach the set temperature of domestic hot water, the user's domestic hot water needs are met. When the internal temperature of the domestic hot water tank (2) reaches the cross-seasonal heat storage start-up temperature threshold and there is a heat surplus, the buried pipe heat exchanger (4) is started to store the surplus solar heat into the underground soil. When solar energy is insufficient or at night, the central control unit (8) turns on the electric heating boiler (3) to supplement the heating of the domestic hot water tank (2); Under heating season operating conditions: Real-time monitoring of the fluid outlet temperature of the buried pipe heat exchanger (4); If the outlet temperature of the fluid is greater than or equal to the heating set threshold, then the direct heating mode is entered: the buried pipe heat exchanger (4) is controlled to directly supply heat to the hot water storage tank (5), and then supply the heating terminal (7) for heating; If the outlet temperature of the fluid is less than the heating set threshold, the heat pump auxiliary heating mode is entered: the ground source heat pump unit (6) is started to assist in heating; at the same time, the excess heat of the domestic hot water tank (2) is introduced into the heating circulation loop to participate in heating.

7. The control method for the integrated energy system for heating and domestic hot water coupling of solar thermal and geothermal energy according to claim 6, characterized in that, The heating setting threshold is set according to the type of heating terminal (7): when the heating terminal (7) adopts a floor radiant heating system, the heating temperature threshold is set to 35-40℃; when the heating terminal (7) adopts a radiator, the heating temperature threshold is set to 50-60℃. The thermal storage start-up temperature threshold is set to 55-65℃.

8. The control method for the integrated energy system for heating and domestic hot water coupling of solar thermal and geothermal energy according to claim 6, characterized in that, The solar collector circulation loop adopts temperature difference control logic: when the temperature difference between the fluid outlet of the flat plate collector (1) and the domestic hot water tank (2) is ≥10℃, the circulation pump on the solar collector circulation loop is started; when the temperature difference is <5℃, the circulation pump on the solar collector circulation loop is stopped.

9. The control method for the integrated energy system for heating and domestic hot water coupling of solar thermal and geothermal energy according to claim 6, characterized in that, During the cross-seasonal heat storage process in the non-heating season, the central control unit (8) also dynamically adjusts the speed of the circulating pump according to the change of the fluid outlet temperature of the buried pipe heat exchanger: when the fluid outlet temperature is higher than the soil equilibrium temperature, the circulation pump flow rate is increased; when the fluid outlet temperature is close to the soil equilibrium temperature, the circulation pump flow rate is reduced or the heat storage is stopped.

10. The control method for the integrated energy system for heating and domestic hot water coupling of solar thermal and geothermal energy according to claim 6, characterized in that, The central control unit (8) also monitors the temperature of the hot water storage tank (5) and the temperature of the heating return water in real time during the heating season. When the temperature difference between the two is less than the preset heating temperature difference threshold, the circulation flow is reduced.

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