Design method and operation strategy of biogas fermentation system based on gas production performance prediction

Abstract

The present invention discloses a design method and operation strategy for a biogas fermentation system based on gas production performance prediction, and relates to the technical field of biogas power systems. The design method for a biogas fermentation system based on gas production performance prediction disclosed by the present invention includes the construction of a gas production performance prediction model, which is based on the coupling of a biogas heat transfer model and a biogas production model, and measures the device performance parameters of the biogas production system and outdoor environmental parameters to construct a biogas heat transfer model. At the same time, it combines the system operation plan to construct a biogas fermentation gas production model; the operation strategy includes the control of insulation, the control of feed, etc. The present invention proposes a design method and operation strategy based on gas production performance prediction, and rationally designs the scale of the biogas system based on the gas production performance prediction model to achieve the goal of reducing costs. By rationally controlling insulation, feed, and gas storage tanks, the purpose of stable gas supply can be achieved under adverse conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of biogas power systems, and in particular to a passive temperature increase design method and operation strategy for a biogas fermentation system based on gas production performance prediction. Background Art

[0002] In recent years, in some real-world projects, actual biogas production has been around 0.02% of potential, indicating low biogas plant efficiency. For rural biogas systems, whether household biogas or biogas projects, actual operational performance is crucial for increasing biogas production.

[0003] During anaerobic fermentation of biomass, if the temperature is too low or the temperature fluctuates too much, the gas production rate and the methane content in the biogas will decrease. Temperature has a great impact on biogas fermentation, so the selection of economical and efficient heating measures has become a necessary prerequisite for the implementation of a centralized biogas supply system in villages and towns. At present, efficient and clean biogas tank heating measures mainly include passive solar greenhouse heating technology, biogas power generation waste heat technology, ground source heat pump technology, active solar heating technology, hybrid solar heating technology and combined heating technology. The use of solar energy, geothermal resources and waste heat can effectively increase the fermentation temperature of biogas tanks, but the heating effect is greatly affected by climatic conditions. It is necessary to quantify and predict the main influencing factors of the fermentation environment temperature based on the construction of fermentation materials, biogas tanks, insulation devices and soil, and outdoor heat transfer models, thereby providing theoretical support for the heating and insulation measures of the fermentation system.

[0004] During the biogas fermentation process, due to the low feed temperature, the feed process has a great influence on its heat preservation and warming effect. In biogas projects, feed heat consumption accounts for more than 90% of the total heat. However, many domestic biogas project operators are not well managed, and the biogas feed and heat preservation control operations are not accurate enough. Therefore, it is particularly important to improve the operating efficiency of biogas plants through actual gas production effect prediction models, which can make up for the extensive management of rural biogas plants. The technology of the present invention mainly focuses on the operation and management of biogas production, involving the supply of biogas produced by biogas projects and the integration of biogas power generation into the power grid. At the same time, the construction of a socialized service system for its overall operation and maintenance cannot be ignored. Summary of the Invention

[0005] The purpose of the present invention is to provide a passive warming design method and operation strategy for a biogas fermentation system based on gas production performance prediction, which can make rational use of biomass energy, solar energy, etc., improve the biogas fermentation effect, reduce costs, and at the same time reasonably utilize excess gas production for power generation, thereby achieving the effect of energy conservation and emission reduction.

[0006] In order to achieve the purpose of the present invention, the present invention provides a method for designing a biogas fermentation system based on gas production performance prediction, including constructing a gas production performance prediction model, wherein the gas production performance prediction model is constructed based on the coupling of a biogas heat transfer model and a biogas production model, that is, the fermentation liquid temperature obtained by the biogas heat transfer model is substituted into the biogas production model to obtain the gas production prediction model.

[0007] Furthermore, the method for constructing the biogas heat transfer model is:

[0008] S1. Measure and investigate the physical model parameters of the biogas production system;

[0009] S2. Monitoring meteorological parameters of outdoor air temperature and solar radiation, as well as feed temperature;

[0010] S3. Based on the physical model parameters of the biogas production system and the outdoor meteorological parameters, a dynamic thermal balance is achieved to obtain the hourly fermentation temperature.

[0011] Furthermore, the physical model parameters include greenhouse size, fermentation tank size and heat transfer coefficient, ground size and heat transfer coefficient, exterior wall size and heat transfer coefficient, film size and heat transfer coefficient, insulation material size and heat transfer coefficient.

[0012] Furthermore, the dynamic thermal balance in step S3 includes the following process:

[0013] S301. Soil dynamic heat balance process:

[0014] The dynamic heat balance equation of the outer soil is shown in the following equation (1):

[0015]

[0016] In the above formula, ρ t is the soil density, kg / m 3 ; V yt is the calculated outer soil volume, m 3 ; C t is the specific heat capacity of soil, J / (kg·K); T yd is the outside soil temperature, ℃; τ is time, s; Q rt is the solar radiation heat absorbed by the outer soil, W; Q tyd is the heat conduction of the outer soil, W; Q yd is the heat transfer between air and outer soil, W;

[0017] Since there is no radiation heat gain in the middle soil and the inner soil, the dynamic heat balance equations of the middle soil and the inner soil are shown in the following equations (2) and (3):

[0018]

[0019]

[0020] In the above formula, V zt is the calculated internal soil volume, m 3 ; V nt is the calculated intermediate soil volume, m 3 ;T zd is the middle soil temperature, ℃; T nd is the internal soil temperature, °C; Q tzd is the heat conduction of the soil in the middle, W; Q tnd is the internal soil heat conduction, W; Q zl is the heat transfer between the fermentation liquid and the soil, W; Q nd is the heat transfer between air and internal soil, W. Where Q tzd and Q tnd The calculation of Q tyd Calculation of Q yd , Q zl and Q nd Calculations can be performed according to ISO 13370;

[0021] S302, Greenhouse air dynamic heat balance process:

[0022] The dynamic heat balance equation of the indoor air in the greenhouse is shown in the following equation (4):

[0023]

[0024] In the above formula, ρ a is the indoor air density of the greenhouse, kg / m 3 ; V a is the total volume of air in the greenhouse, m 3 ; C a is the specific heat capacity of the air in the greenhouse, J / (kg·K); T a is the indoor air temperature of the greenhouse, ℃; r a is the proportion of solar radiation absorbed by the greenhouse air; Q r is the solar radiation heat received by the greenhouse, W; Q h is the heat transfer between indoor air and back slope, W; Q wi is the heat transfer between the indoor air and the outdoor air through the exterior wall of the greenhouse, W; Q m is the heat transfer between the greenhouse air through the film and the outdoor air, W; Q l is the heat transfer between indoor air and fermentation liquid, W;

[0025] S303, dynamic heat balance process of fermentation liquid:

[0026] The dynamic heat balance equation of the fermentation liquid is shown in the following formula (5):

[0027]

[0028] In the above formula, T l is the fermentation liquid temperature, ℃; ρ l is the density of fermentation liquid, kg / m 3 ; V l is the volume of fermentation liquid, m 3 ; C l is the specific heat capacity of the fermentation liquid, J / (kg·K); B is the feed control coefficient, which is 1 when the fermentation tank is being fed and 0 when not being fed; Feed volume flow rate, m 3 / s;T j is the feed temperature, °C; r l Q is the ratio of solar radiation absorbed by the fermentation liquid; rl The solar radiation energy collected by the fermentation liquid, W.

[0029] Furthermore, the method for constructing the biogas production model is: performing real-time gas production prediction based on fermentation gas production factors, and using a gas production kinetics model such as the Chen-Hashimoto model to calculate and obtain the real-time tank capacity gas production rate.

[0030] Furthermore, the fermentation gas production factors include the type of fermentation raw materials, the concentration of fermentation raw materials, feeding strategy, hydraulic retention time and fermentation temperature, etc.

[0031] Furthermore, the operation strategy is judged based on whether the gas demand is met and the system cost is lowest, that is, when the system cost is lowest, the operation plan is optimal.

[0032] Furthermore, the method for adjusting the operation strategy specifically includes the following steps:

[0033] P1. Construct a biogas heat transfer model and a biogas production model. Then, couple the biogas heat transfer model and the biogas production model to construct a gas production performance prediction model. Hourly gas production prediction is performed based on the gas production performance prediction model.

[0034] P2. When the hourly gas production forecast process meets the hourly gas demand, the system cost is evaluated to see if it is the lowest. If the system cost is the lowest, the operation plan is the best. If the system cost is not the lowest, the biogas fermentation system design method and biogas production operation plan need to be optimized to achieve the lowest system cost.

[0035] P3. When the hourly gas demand is not met during the hourly gas production forecast process, the biogas production operation plan is optimized. After optimization, it is judged again whether the hourly gas demand is met. If the hourly gas demand is not met, it is necessary to continue to optimize the biogas fermentation system design method and the biogas production operation plan until the hourly gas demand is met; if the hourly gas demand is met, it is evaluated whether the system cost is the lowest. When the system cost is the lowest, the operation plan is optimal; when the system cost is not the lowest, it is necessary to optimize the biogas fermentation system design method and the biogas production operation plan to achieve the lowest system cost.

[0036] Furthermore, the optimization of the biogas production operation plan includes feed time, insulation control, feed waste heat utilization and hydraulic retention time optimization.

[0037] The biogas fermentation system designed by the biogas fermentation system design method based on gas production performance prediction can be used to achieve cogeneration of heat and power, that is, the biogas generated by the biogas fermentation system and the excess biogas are used for cogeneration of heat and power, and the electricity is connected to the grid or used by the system.

[0038] Preferably, the biogas fermentation system is provided with energy storage equipment. In order to better ensure energy supply, energy storage equipment such as gas storage tanks, electrical energy storage equipment, etc. can be added according to actual conditions.

[0039] Preferably, the gas-consuming side monitors the relevant gas usage conditions by monitoring the biogas flow of the biogas supply main pipe, so as to achieve production adjustments on the gas-producing side.

[0040] The present invention has achieved the following beneficial effects:

[0041] 1. The design method and operation strategy described in the present invention make the best use of the abundant biomass energy and solar energy in rural areas to produce biogas, which can save energy, reduce emissions and improve the living quality of farmers compared with the original coal combustion.

[0042] 2. The design method and operation strategy described in the present invention are based on the actual gas production effect prediction model, which is particularly important for improving the operation efficiency of biogas plants and can make up for the extensive management of rural biogas plants.

[0043] 3. The design method and operation strategy of the present invention are rationally controlled based on gas production performance prediction, etc., so as to achieve the purpose of continuing to supply energy under adverse conditions.

[0044] 4. The biogas fermentation system of the present invention makes rational use of biomass energy and solar energy. At the same time, the excess gas produced can be reasonably used to generate electricity during the process, saving energy and reducing emissions. At the same time, the operation strategy is carried out through reasonable control of feeding, insulation, hydraulic retention time, etc., so as to achieve the purpose of gas supply under unfavorable conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic diagram of a biogas heat transfer model of the present invention;

[0046] Figure 2 It is a specific operation flow chart of the operation strategy of the biogas fermentation system of the present invention;

[0047] Figure 3 This is a table showing heating guarantee rates of different biogas systems under configuration and operation optimization of a solar-assisted biogas heating system according to an embodiment of the present invention;

[0048] Figure 4 Schematic diagram of gas production and use in the heating season without optimization under the configuration and operation optimization of the solar-assisted biogas heating system according to one embodiment of the present invention;

[0049] Figure 5 Schematic diagram of gas production and use in the heating season after optimization of the configuration and operation of a solar-assisted biogas heating system according to one embodiment of the present invention;

[0050] Figure 6 This is a table showing heating guarantee rates and economic efficiency of different biogas systems under configuration and operation optimization of a solar-assisted biogas heating system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. All features disclosed in this specification, or steps in all methods or processes disclosed, except for mutually exclusive features and / or steps, can be combined in any manner.

[0052] The present invention provides a method for designing a biogas fermentation system based on gas production performance prediction, which is to construct a gas production performance prediction model. The gas production performance prediction model is based on the measurement of the physical model parameters of the biogas production system (i.e., device performance parameters) and outdoor environmental parameters (i.e., outdoor air temperature meteorological parameters, outdoor solar radiation meteorological parameters, and feed temperature) to construct a biogas heat transfer model. At the same time, in combination with the system operation plan, a biogas production model is constructed, and the biogas heat transfer model is coupled with the biogas production model to obtain a gas production performance prediction model. That is, the fermentation liquid temperature obtained by the biogas heat transfer model is substituted into the biogas production model to obtain the gas production performance prediction model.

[0053] like Figure 1 As shown in Figure 2, heat transfer occurs during the construction of the biogas heat transfer model, and the heat transfer process can include the following steps:

[0054] (1) On a clear day, solar radiation enters the indoor surface of the greenhouse through the light-transmitting film and the enclosure structure, and transfers heat between the indoor surfaces;

[0055] (2) The air in the greenhouse exchanges heat with the surrounding environment through the enclosure structure, soil and light-transmitting film;

[0056] (3) The heat of the fermentation liquid is exchanged with the air and soil through the biogas tank. At night or on cloudy and rainy days, the greenhouse lighting film will be covered with an insulation blanket.

[0057] Preferably, the method for constructing the biogas heat transfer model of the present invention is:

[0058] S1. Measure and investigate the physical model parameters of the biogas production system, such as greenhouse size, fermentation tank size and heat transfer coefficient, floor size and heat transfer coefficient, exterior wall size and heat transfer coefficient, film size and heat transfer coefficient, insulation material size and heat transfer coefficient, etc.

[0059] S2. Monitoring meteorological parameters of outdoor air temperature and solar radiation, as well as feed temperature;

[0060] S3. Based on the physical model parameters of the biogas production system and the outdoor meteorological parameters, a dynamic thermal balance is achieved to obtain the hourly fermentation temperature.

[0061] The dynamic heat balance in the above biogas heat transfer model includes the following processes:

[0062] S301. Soil dynamic heat balance process:

[0063] The dynamic heat balance equation of the outer soil is shown in the following equation (1):

[0064]

[0065] In the above formula, ρ t is the soil density, kg / m 3 ; V yt is the calculated outer soil volume, m 3 ; C t is the specific heat capacity of soil, J / (kg·K); T yd is the outside soil temperature, ℃; τ is time, s; Q rt is the solar radiation heat absorbed by the outer soil, W; Q tyd is the heat conduction of the outer soil, W; Q yd is the heat transfer between the air and the outer soil, W.

[0066] Since there is no radiation heat gain in the middle soil and the inner soil, the dynamic heat balance equations of the middle soil and the inner soil are as follows (2) and (3):

[0067]

[0068]

[0069] In the above formula, V zt is the calculated internal soil volume, m 3 ; V nt is the calculated intermediate soil volume, m 3 ;T zd is the middle soil temperature, ℃; T nd is the internal soil temperature, °C; Q tzd is the heat conduction of the soil in the middle, W; Q tnd is the internal soil heat conduction, W; Q zl is the heat transfer between the fermentation liquid and the soil, W; Q nd is the heat transfer between air and internal soil, W. Where Q tzd and Q tnd The calculation of Q tyd Calculation of Q yd , Q zl and Q nd Calculations can be performed according to standard ISO 13370.

[0070] S302, Greenhouse air dynamic heat balance process:

[0071] The dynamic heat balance equation of the indoor air in the greenhouse is shown in the following equation (4):

[0072]

[0073] In the above formula, ρ a is the indoor air density of the greenhouse, kg / m 3 ; V a is the total volume of air in the greenhouse, m 3 ; C a is the specific heat capacity of the air in the greenhouse, J / (kg·K); T a is the indoor air temperature of the greenhouse, ℃; r a is the proportion of solar radiation absorbed by the greenhouse air; Q r is the solar radiation heat received by the greenhouse, W; Q h is the heat transfer between indoor air and back slope, W; Q wi is the heat transfer between the indoor air and the outdoor air through the exterior wall of the greenhouse, W; Q m is the heat transfer between the greenhouse air through the film and the outdoor air, W; Q l is the heat transfer between indoor air and fermentation liquid, W.

[0074] S303, dynamic heat balance process of fermentation liquid:

[0075] The dynamic heat balance equation of the fermentation liquid is shown in the following formula (5):

[0076]

[0077] In the above formula, ρ l is the density of the fermentation liquid, kg / m 3 ; V l is the volume of fermentation liquid, m 3 ; C l is the specific heat capacity of the fermentation liquid, J / (kg·K); B is the feed control coefficient, which is 1 when the fermentation tank is being fed and 0 when not being fed; Feed volume flow, m 3 / s;T j is the feed temperature, °C; r l Q is the ratio of solar radiation absorbed by the fermentation liquid; rl The solar radiation energy collected by the fermentation liquid, W.

[0078] Preferably, the biogas production model construction method of the present invention is: it is necessary to perform real-time gas production prediction based on fermentation gas production factors (such as fermentation raw material type, fermentation raw material concentration, feeding strategy, hydraulic retention time, fermentation temperature, etc.), for example, using the Chen-Hashimoto model for calculation.

[0079] The present invention provides an operation strategy for a biogas fermentation system based on gas production performance prediction, in which the operation is judged based on whether the gas demand is met and the system cost is minimized. If the gas supply is not met under comprehensive evaluation, the biogas production operation plan is optimized; finally, a comprehensive evaluation is conducted to determine whether the system cost is the lowest. Otherwise, the biogas fermentation system design and operation strategy need to be further optimized to minimize the system cost and optimize the operation plan.

[0080] The optimization of the biogas production operation plan includes feeding time, insulation control, feed waste heat utilization and hydraulic retention time optimization. After optimization, it is judged again whether the hourly gas demand is met.

[0081] Preferably, the method for adjusting the operation strategy of a biogas fermentation system based on gas production performance prediction of the present invention specifically comprises the following steps:

[0082] P1. Construct a biogas heat transfer model and a biogas production model, then couple the biogas heat transfer model with the biogas production model to construct a gas production performance prediction model, and perform hourly gas production prediction based on the gas production performance prediction model.

[0083] P2. When the hourly gas production forecast process meets the hourly gas demand, the system cost is evaluated to see if it is the lowest. When the system cost is the lowest, the operation plan is the best. When the system cost is not the lowest, it is necessary to optimize the biogas fermentation system design method and the biogas production operation plan to achieve the lowest system cost.

[0084] P3. When the hourly gas demand is not met during the hourly gas production forecast process, the biogas production operation plan is optimized. After optimization, it is judged again whether the hourly gas demand is met. If the hourly gas demand is not met, it is necessary to continue to optimize the biogas fermentation system design method and the biogas production operation plan until the hourly gas demand is met; if the hourly gas demand is met, it is evaluated whether the system cost is the lowest. When the system cost is the lowest, the operation plan is optimal; when the system cost is not the lowest, it is necessary to optimize the biogas fermentation system design method and the biogas production operation plan to achieve the lowest system cost. In this embodiment, the net present value indicator is used to evaluate the economic performance of the biogas heating system, taking into account the initial investment and 20-year operating costs. If the net present value is greater than 0, it indicates that the system route is economically feasible. With the net present value of 0, the calculated biogas sales price is the biogas cost price.

[0085] The biogas fermentation system design method and operation strategy based on gas production performance prediction of the present invention can be applied to a variety of gas supply methods, such as using the biogas generated in the present invention to supply cooking, domestic hot water and heating respectively, or using biogas to supply cooking, domestic hot water and heating at the same time.

[0086] Example 1: Configuration and operation optimization of solar-assisted biogas heating system

[0087] Based on the heating and cooking biogas needs of 500 rural users, the heating operating conditions are that the bedroom air conditioner runs from 22:00 to 8:00, the living room air conditioner runs from 7:00 to 22:00, and the heating temperature is 18 to 22℃. The system design and operation plan are determined, and the heating is not guaranteed to be no more than 5 days to meet the gas requirements.

[0088] Based on the above situation, a biogas heat transfer model and a biogas production model were constructed to obtain the heating guarantee rates of different system design schemes, such as Figure 3 When the biogas system scale is such that the effective capacity of the fermentation tank exceeds 12500m 3 (Other supporting facilities match the capacity of the fermentation tank) to meet the gas demand. Finally, the most suitable solution is to determine the lowest system cost, which is a fermentation tank with an effective capacity of 12500m 3 The biogas system and gas production and consumption during the heating season are shown in Figure 4.

[0089] If certain optimization conditions such as Figure 2 In the case shown in FIG, for example, by optimizing the feeding time, heat preservation and utilization of waste heat, the gas production and consumption in the heating season are as follows: Figure 5 As shown. Secondly, determine whether the system meets the minimum cost requirement. Since the gas production surplus is greater after optimization, the cost is not the lowest. Optimize the system design and operation plan again to obtain the final result (as shown Figure 6As shown), the original fermentation tank has an effective capacity of 12500m 3 The biogas system can be optimized to a fermentation tank with an effective capacity of 8300m 3 biogas system.

[0090] The biogas fermentation system design method and operation strategy based on gas production performance prediction in Example 1 rationally utilizes biomass energy and solar energy. Excess gas production can also be used to generate electricity, thereby saving energy and reducing emissions. Furthermore, by rationally controlling feed, insulation, hydraulic retention time, and other factors, gas supply can be achieved even under adverse conditions.

[0091] The above-described embodiments merely represent specific implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A biogas fermentation system design method based on gas production performance prediction, characterized in that: The method comprises constructing a gas production performance prediction model, wherein the gas production performance prediction model is constructed based on the coupling of a biogas heat transfer model and a biogas production model; The method for constructing the biogas heat transfer model is as follows: S1. Measure and investigate the physical model parameters of the biogas production system; S2. Monitoring meteorological parameters of outdoor air temperature and solar radiation, as well as feed temperature; S3, based on the physical model parameters of the biogas production system and the outdoor meteorological parameters to achieve dynamic thermal equilibrium, obtain the hourly fermentation temperature; The dynamic heat balance in step S3 includes the following processes: S301. Soil dynamic heat balance process: The dynamic heat balance equation of the outer soil is shown in the following equation (1): In the above formula, ρ t is the soil density, kg / m 3 ; V yt is the calculated outer soil volume, m 3 ; C t is the specific heat capacity of soil, J / (kg·K); T yd is the outside soil temperature, ℃; τ is time, s; Q rt is the solar radiation heat absorbed by the outer soil, W; Q tyd is the heat conduction of the outer soil, W; Q yd is the heat transfer between air and outer soil, W; Since there is no radiation heat gain in the middle soil and the inner soil, the dynamic heat balance equations of the middle soil and the inner soil are shown in the following equations (2) and (3): In the above formula, V zt is the calculated internal soil volume, m 3 ; V nt is the calculated intermediate soil volume, m 3 ; T zd is the middle soil temperature, ℃; T nd is the internal soil temperature, °C; Q tzd is the heat conduction of the soil in the middle, W; Q tnd is the internal soil heat conduction, W; Q zl is the heat transfer between the fermentation liquid and the soil, W; Q nd is the heat transfer between air and internal soil, W; where Q tzd and Q tnd The calculation of Q tyd Calculation of Q yd , Q zl and Q nd Calculations can be performed according to ISO 13370; S302, Greenhouse air dynamic heat balance process: The dynamic heat balance equation of the indoor air in the greenhouse is shown in the following equation (4): In the above formula, ρ a is the indoor air density of the greenhouse, kg / m 3 ; V a is the total volume of air in the greenhouse, m 3 ; C a is the specific heat capacity of the air in the greenhouse, J / (kg·K); T a is the indoor air temperature of the greenhouse, ℃; r a is the proportion of solar radiation absorbed by the greenhouse air; Q r is the solar radiation heat received by the greenhouse, W; Q h is the heat transfer between indoor air and back slope, W; Q wi is the heat transfer between the indoor air and the outdoor air of the greenhouse through the exterior wall, W; Q m is the heat transfer between the greenhouse air through the film and the outdoor air, W; Q l is the heat transfer between indoor air and fermentation liquid, W; S303, dynamic heat balance process of fermentation liquid: The dynamic heat balance equation of the fermentation liquid is shown in the following formula (5): In the above formula, ρ l is the density of the fermentation liquid, kg / m 3 ; V l is the volume of fermentation liquid, m 3 ; C l is the specific heat capacity of the fermentation liquid, J / (kg·K); B is the feed control coefficient, which is 1 when the fermentation tank is being fed and 0 when not being fed; Feed volume flow, m 3 / s;T j is the feed temperature, °C; r l Q is the ratio of solar radiation absorbed by the fermentation liquid; rl The solar radiation energy collected by the fermentation liquid, W.

2. The biogas fermentation system design method based on gas production performance prediction according to claim 1, characterized in that: The physical model parameters include greenhouse size, fermentation tank size and heat transfer coefficient, ground size and heat transfer coefficient, exterior wall size and heat transfer coefficient, film size and heat transfer coefficient, insulation material size and heat transfer coefficient.

3. The biogas fermentation system design method based on gas production performance prediction according to claim 1, characterized in that: The method for constructing the biogas production model is to make a real-time gas production prediction based on the fermentation gas production elements and to use the gas production kinetics model for calculation.

4. The biogas fermentation system design method based on gas production performance prediction according to claim 3, characterized in that: The gas production kinetics model is the Chen-Hashimoto model.

5. The biogas fermentation system design method based on gas production performance prediction according to claim 3, characterized in that: The fermentation gas production factors include the type of fermentation raw materials, the concentration of fermentation raw materials, the feeding strategy, the hydraulic retention time and the fermentation temperature.

6. A biogas fermentation system operation strategy based on gas production performance prediction, characterized in that: The operation strategy is based on whether the gas demand is met and the system cost is minimized. That is, when the system cost is the lowest, the operation plan is optimal. The method for adjusting the operation strategy specifically includes the following steps: P1. Constructing a biogas heat transfer model and a biogas production model based on the method of claim 1, then coupling the biogas heat transfer model with the biogas production model to construct a gas production performance prediction model, and performing hourly gas production prediction based on the gas production performance prediction model; P2. When the hourly gas production forecast process meets the hourly gas demand, the system cost is evaluated to see if it is the lowest. If the system cost is the lowest, the operation plan is the best. If the system cost is not the lowest, the biogas fermentation system design method and biogas production operation plan need to be optimized to achieve the lowest system cost. P3. When the hourly gas demand is not met during the hourly gas production forecast process, the biogas production operation plan is optimized. After optimization, it is judged again whether the hourly gas demand is met. If the hourly gas demand is not met, it is necessary to continue to optimize the biogas fermentation system design method and the biogas production operation plan until the hourly gas demand is met; if the hourly gas demand is met, it is evaluated whether the system cost is the lowest. When the system cost is the lowest, the operation plan is optimal; when the system cost is not the lowest, it is necessary to optimize the biogas fermentation system design method and the biogas production operation plan to achieve the lowest system cost.

7. The biogas fermentation system operation strategy based on gas production performance prediction according to claim 6, characterized in that: The optimization of the biogas production operation plan includes controlling the feeding time, heat preservation management, utilizing the feed waste heat and optimizing the hydraulic retention time.

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