CN104766133A - Comprehensive optimization method for small biomass methane combined supply system of cooling, heating and power - Google Patents

Abstract

The invention discloses a comprehensive optimization method for a small-scale biomass biogas combined cooling, heating and power supply system. For a given user who can produce biogas, simulate its annual hourly cooling, heating and power load demand in a typical weather year, and obtain the building's annual Cooling, heating and power load curve; design the variable working condition characteristics of the main equipment of the cogeneration system; construct and design the small biomass biogas cogeneration system; determine the optimization variables of the small biomass biogas cogeneration system The energy saving rate, cost recovery rate and emission reduction benefit of the power supply system are the comprehensive goals, and the parameters of other equipment in the small biomass biogas cogeneration system are set; the optimization constraints are determined; the optimal design objective function is established; the optimal design is solved The objective function obtains the optimized variable, and further obtains the optimal configuration of other equipment in the system. The method is simple and easy to implement, and combined with the building energy consumption analysis theory, it can be applied to the optimal design of different types of small-scale combined cooling, heating and power systems.

Description

A comprehensive optimization method for a small-scale biomass biogas cogeneration system

technical field

The invention relates to the field of energy technology, in particular to a comprehensive optimization method for a small-scale biomass biogas cogeneration system.

Background technique

As a large agricultural country, my country has abundant biomass energy resources. The resources that can be used to produce biomass gas each year are equivalent to about 250 million tons of standard coal, which can convert about 199 billion cubic meters of biogas equivalent, equivalent to 120 billion cubic meters of natural gas, which is equivalent to my country's natural gas consumption in 2011 was 93% of 129 billion cubic meters. According to the total energy consumption in 2011 (3.48 billion tons of standard coal), the development of biomass gas will increase the proportion of China's gas energy consumption by about 7%. As a typical biomass gas renewable energy, biogas has the advantages of high calorific value and low combustion pollution. The complete combustion of 1 cubic meter of biogas can produce the heat equivalent to 0.7 kg of anthracite coal. Using biogas to generate electricity can not only solve the power shortage It can also reduce the emission of greenhouse gases such as methane and purify the air environment.

However, it is an indisputable fact that at present, a large number of biomass resources in my country have not been used reasonably and efficiently. For example, most of the rural biomass biogas is only used for cooking by farmers, and it is idle for the rest of the time, resulting in extreme shortages of equipment, funds and resources. Big waste. The combined cooling, heating and power system is a total energy system based on the concept of energy cascade utilization. The three processes of water) meet the user's cooling, heating, and electricity needs on the spot, thereby reducing the transmission loss of long-distance energy supply, and greatly improving social and economic benefits and energy utilization efficiency. In particular, the tens of kilowatt-level biomass air-cooled combined heat and power system is just suitable for the decentralized and small-scale application of biomass resources in my country. It can greatly alleviate the problems of rural heating difficulties and local environmental pollution, and is of great significance to promoting the adjustment of agricultural structure and building a new socialist countryside.

Obviously, my country's demand for tens of kilowatts of biomass air-cooled combined heat and power distributed energy supply systems is very urgent, and the demand is huge. As a polygeneration complex total energy system, the cogeneration system has a wide variety of composition structures and operation modes, and it is also accompanied by real-time changes in building loads, which makes its design problems extremely complicated. Once improperly designed, it will lead to Low efficiency and investment waste and many other disadvantages.

After searching the public literature of the prior art, it is found that, for example, the patent with the publication number CN 1945472 takes cost and energy consumption as the optimization goal, and proposes a centralized optimization control method for the combined cooling, heating and power supply system, which realizes the operation of terminal equipment. Parameter control; the patent application No. 201010147996.0 discloses an energy efficiency optimization scheduling system for combined cooling, heating and power generation systems, which optimizes and dispatches the output plans of each energy unit based on load forecasting and related optimization calculations, and then realizes the cooling, heating, and electricity energy. supply and demand balance. Although the above methods have effectively improved the performance of the cogeneration system, there are also certain deficiencies:

1) It does not involve the engineering optimization design of small combined cooling, heating and power systems, especially those using biomass as energy. On the one hand, most of the existing combined cooling, heating and power systems still use natural gas as the main energy source. However, since natural gas is a fossil fuel, it is difficult to maximize the advantages of energy saving and emission reduction of distributed energy supply systems. On the other hand, with the rise of household and small commercial cogeneration systems, tens of kilowatts of gas turbines have attracted more and more attention. As the core of this type of small-scale cogeneration system, it is different from large and medium-sized units in terms of unit parameters, efficiency, and waste heat, which in turn affects the subsequent selection of matching equipment and capacity selection, which also leads to system failure. The overall design scheme will also be different from the past.

2) The cogeneration system is a complex energy system composed of multiple units, in which the input and output characteristics of each unit, especially the key equipment, have a decisive impact on the overall performance of the system. However, due to the difficulty of modeling each component and the heavy workload, the current conventional optimization design method only starts with the energy flow function, and does not involve the dynamic characteristics of each device.

Contents of the invention

The purpose of the present invention is to solve the above problems, and provide a comprehensive optimization method for a small-scale biomass biogas cogeneration system. Taking the distribution system as a reference object, the energy saving rate, cost recovery rate and _CO2 emission reduction rate are comprehensive. Objective: To establish an optimization model for the combined cooling, heating and power supply system of small biomass biogas internal combustion generators, which takes into account the characteristics of variable operating conditions of the equipment, and solve the capacity of internal combustion generators, the start-stop coefficient and the specific gravity of electric refrigeration, and realize the small biomass biogas Optimal design of joint supply system.

In order to achieve the above object, the present invention adopts the following technical solutions:

A comprehensive optimization method for a small-scale biomass biogas cogeneration system, comprising the following steps:

Step 1: For a given user that can produce biogas, simulate its annual hourly cooling, heating and power load demand in a typical weather year, and obtain the building's annual cooling, heating and power load curve;

Step 2: Design the variable working condition characteristics of the main equipment of the cogeneration system;

Step 3: Construct and design a small-scale biomass biogas cogeneration system;

Step 4: Determine the optimization variables of the small-scale biomass biogas CHP system, including:

The capacity of the internal combustion generator set, the start-stop coefficient of the internal combustion generator set and the electric refrigeration ratio are three variables, where the electric refrigeration ratio is defined as:

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; ch</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; ch</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; ab</span>}}}$

In the formula: Q _ch and Q _ab represent the electric cooling capacity of the electric refrigeration unit and the absorption cooling capacity of the absorption refrigeration unit, respectively;

In addition to internal combustion generator sets and refrigeration units, set equipment efficiency values, carbon dioxide emission coefficients for gas and grid power generation, algorithm parameters, and energy prices according to the research situation;

Step 5: Determine the optimization constraint conditions; establish an optimal design objective function, with the energy-saving rate, cost recovery rate and emission reduction benefit relative to the traditional distribution system as the comprehensive target; solve the optimal design objective function to obtain the optimization variables in the step 4, Further obtain the optimal configuration of other equipment in the system.

In said step 2, the main equipment of the cogeneration system includes an internal combustion generator set, a lithium bromide absorption refrigerator and an electric refrigerator;

The specific method for the design of the variable working condition characteristics of the main equipment of the cogeneration system is as follows: determine the efficiency parameters according to the partial load rate of the internal combustion generator set; determine the maximum cooling capacity of the lithium bromide absorption refrigerator according to the temperature of hot water and cooling water generated by waste heat recovery ; Calculate the maximum cooling capacity of the electric refrigerator according to the set chilled water temperature and cooling water temperature; obtain the variable operating condition characteristic curve or surface by fitting the spline interpolation method.

In the third step, the small-scale biomass biogas cogeneration system includes biogas pretreatment equipment, gas storage tanks, internal combustion generators, heat exchangers, auxiliary boilers, absorption refrigeration units, electric refrigeration units and large grid power supply systems ;

The biogas produced by anaerobic fermentation of biomass enters the gas storage tank after passing through the biogas purification equipment, and is used to drive the internal combustion generator set to generate electricity. The output power of the internal combustion generator set is supplied to users, electric refrigerators, cooling towers and other equipment. The system is an auxiliary power supply; the heat exchanger water circulation system is used in series to fully recover the waste heat of the flue gas and the waste heat of the jacket water; the recovered heat is suitable for driving a small-capacity single-effect absorption refrigerator; the auxiliary boiler also uses biogas as fuel, It is used to supplement the heat demand gap of the system; the electric refrigeration unit cooperates with the absorption refrigerator to provide cooling for users.

In said step five,

The method of determining the optimization constraints is as follows: during the optimization calculation process, the balance of cold, heat and electric energy inside the system is guaranteed, and the upper and lower limits of the optimization variables are set to meet the characteristics of the variable working conditions of the equipment.

In said step five,

The optimal design objective function is:

max V＝ω ₁ PESR+ω ₂ ACR+ω ₃ CO ₂ ERR

in $\mathrm{PESR}=\frac{G_{\mathrm{SP}}-G_{\mathrm{CCHP}}}{G_{\mathrm{SP}}},{\mathrm{CO}}_2\mathrm{ERR}=\frac{{\mathrm{CO}}_2{\mathrm{E.}}_{\mathrm{SP}}-{\mathrm{CO}}_2{\mathrm{E.}}_{\mathrm{CCHP}}}{{\mathrm{CO}}_2{\mathrm{E.}}_{\mathrm{SP}}},$

$\mathrm{<span\; class="notranslate">\; ACR</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 365</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; j</span>}}{\overset{\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; sp</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; grid</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; ej</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; sp</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; gas</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; CCHP</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; SP</span>}}}$

In the formula, PESR is the energy saving rate of the cogeneration system; ACR is the number of years required for the cogeneration system to recover the increased equipment purchase cost by saving energy costs, that is, the annual cost recovery rate; CO ₂ ERR is the carbon dioxide emission reduction rate of the cogeneration system; ω ₁ , ω ₂ , and ω ₃ represent the weight coefficients of PESR, ACR, and CO ₂ EER respectively, and satisfy 0≤ω ₁ , ω ₂ , ω ₃ ≤1, and ω ₁ +ω ₂ +ω ₃ =1; max V Indicates the maximization of the comprehensive objective function; G _CCHP and G _SP respectively represent the annual total energy consumption of the combined power supply system and the distributed power supply system; CO _{2 E CCHP} represents the annual carbon dioxide emissions of the combined power supply system _; G _gas is the total gas energy consumed by the cogeneration system, E _grid is the electricity purchased by the cogeneration system from the large power grid; R _CCHP and R _SP represent the equipment investment costs of the cogeneration system and the distributed system, respectively ; E _sp is the power consumption of the distribution system; i and j represent the day and hour respectively; p _ej is the time-of-use electricity price at j moment, and p _f is the fuel price.

According to the optimization variables obtained in the above step 4, the capacity of absorption refrigeration units, heat exchangers, auxiliary boilers and electric refrigerators is further determined in combination with user loads, and the comparison between this small biomass biogas combined cooling, heating and power system and natural gas combined supply The difference in annual gas consumption, energy costs and CO ₂ emissions of the system.

Beneficial effects of the present invention:

Taking the distribution system as the reference object, the energy saving rate, the cost recovery rate and the CO ₂ emission reduction rate are comprehensively targeted, and an optimization model for the combined cooling, heating and power generation system of small biomass biogas internal combustion generator sets is established considering the characteristics of equipment variable operating conditions , and obtained the internal combustion generator capacity, start-stop coefficient and electric refrigeration specific gravity, and realized the optimal design of the small-scale biomass biogas cogeneration system. The method is simple and easy to implement, and combined with the building energy consumption analysis theory, it can be applied to the optimal design of different types of small-scale combined cooling, heating and power systems.

Description of drawings

Figure 1 is a schematic diagram of the structure of a small-scale biomass biogas internal combustion power generation combined cooling, heating and power system;

Figure 2 is a flowchart of the optimal design of a small combined cooling, heating and power system considering energy saving, economy, and environmental protection;

Figure 3 is the fitting curve or surface of the variable working condition characteristics of the internal combustion generator set and the refrigeration unit; among them, Figure (a) is the thermal efficiency curve of the internal combustion generator set; Figure (b) is the power generation efficiency curve of the internal combustion generator set, and Figure (c) is The variation of capacity coefficient (the ratio of usable capacity to rated capacity) of absorption chiller, figure (d) is the variation of capacity coefficient of electric chiller (ratio of usable capacity to rated capacity).

Among them, 1. Internal combustion generator set; 2. Jacket water heat exchanger; 3. Flue gas heat exchanger; 4. Auxiliary boiler; 5. Electric refrigerator; 6. Absorption refrigerator; 7. Cooling tower; 8. User; 9. Biogas pretreatment equipment; 10. Gas storage tank. the

The symbols in the figure are: E _grid and E _pgu respectively represent the electricity purchased by the grid and the power generated by the generator set; E _{ch_CCHP} and E _{pa_CCHP} represent the power consumption of the electric refrigerator and peripheral equipment of the cogeneration system; E is the instantaneous electric load; G _pgu represents the gas energy _consumed by the unit; Q _ch is the cooling capacity of the electric refrigerator; Q _ab is the cooling capacity of the absorption refrigerator; C is the user’s _{instantaneous} cooling demand _; is the total waste heat recovered by the unit; H represents the user’s instantaneous heat load demand; Q _b represents the heat supplied by the waste heat boiler; Q _ex is the redundant heat generated by the system; Q _bch represents the heat driving the lithium bromide absorption refrigerator; G _b is The input energy required by the gas boiler; G _pgu represents the gas energy consumed by the unit; G _CCHP represents the total energy consumed by the cogeneration system.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a structural diagram of a small biomass biogas cogeneration system of the present invention. Composed of internal combustion generator set 1, jacket water heat exchanger 2, flue gas heat exchanger 3, auxiliary boiler 4, electric refrigerator 5, absorption refrigerator 6, cooling tower 7, user 8, biogas pretreatment equipment 9, storage Composed of a gas tank 10, the biogas pretreatment equipment 9 is biogas purification equipment.

The specific working process is as follows:

(1) The biogas produced by the anaerobic fermentation of biomass passes through the pretreatment equipment 9 and then enters the gas storage tank 10 for storage. When the joint supply system is working, it is used to drive the internal combustion generator set 1 to generate electricity, and supply the building, the electric refrigeration unit 5, and the cooling tower 7 and other equipment use; when the power generation is insufficient, it can be met through the purchase of electricity from the large grid;

(2) The waste heat generated while the biogas is supplied to the internal combustion generator set 1 for power generation is recovered in series through the jacket water heat exchanger 2 and the flue gas heat exchanger 3, and the recovered heat is used to drive the absorption refrigerator 6 in summer and directly in winter Supply to the user 8; when the heat provided is insufficient, it is supplemented by the auxiliary boiler 4;

(3) The internal-combustion generator set 1 operates according to the electric load, no excess electricity is generated, and the excess heat generated can be directly discharged and supplied to nearby users.

Fig. 2 is the overall implementation process of the present invention, and concrete steps are as follows:

1. Use the energy consumption simulation software to simulate the 8,760-hour hourly cooling, heating, and electricity load data of a typical meteorological year for energy supply objects in a given area, and draw the annual load change curve in units of hours;

2. Integrating factors such as local energy prices and policies, design a traditional distributed energy system as a reference for the optimal design of the combined power supply system; on the premise of meeting the needs of users, calculate the annual electricity consumption and gas consumption of the system , and at the same time get the annual energy consumption cost and CO ₂ emissions;

3. Based on the TRNSYS energy consumption simulation platform, a small-scale biomass biogas internal combustion power generation combined cooling, heating and power supply system is constructed and designed taking into account the characteristics of equipment variable working conditions. Compared with the traditional power distribution system, the energy saving rate and annual cost recovery rate and CO ₂ emission reduction rate, and optimize the design of the key parameters of the structure, capacity and operation mode of the cogeneration system. And the system is compared with the natural gas cogeneration system in terms of annual gas consumption, energy cost and CO ₂ emissions. The specific process is as follows:

3.1 Construct a small biomass biogas combined cooling, heating and power system, including biogas purification equipment, gas storage tanks, internal combustion generators, heat exchangers, auxiliary boilers, absorption refrigeration units, electric refrigeration units and large power grid power supply systems, the specific working process As follows: (1) The biogas produced by anaerobic fermentation of biomass is pretreated to drive the internal combustion generator set to generate electricity, which is supplied to buildings, electric refrigeration units and other equipment; when the power generation is insufficient, it can be met by purchasing electricity from the large grid; (2) Biogas The waste heat generated while supplying the internal combustion generator set for power generation is recovered in series through the jacket water heat exchanger and the flue gas heat exchanger. The recovered heat is used to drive the absorption refrigerator in summer and directly supplied to the user in winter; when the heat provided is insufficient supplemented by auxiliary boilers;

3.2 Selection and determination of optimization variables for small-scale biomass biogas combined cooling, heating and power system: including three variables: capacity of internal combustion generator set, start-stop coefficient of internal combustion generator set, and electric cooling ratio, where the electric cooling ratio is defined as:

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; ch</span>}}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; ch</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; ab</span>}}}$

In the formula: Q _ch and Q _ab represent electric cooling capacity and absorption cooling capacity respectively;

Limited by the waste heat of small internal combustion generator sets, it is only suitable for matching single-effect absorption refrigerators with low COP (cooling coefficient), which will reduce the performance of the cogeneration system. The refrigerator realizes mixed cooling to take into account waste heat utilization and cooling efficiency;

3.3 Fit the variable working condition characteristic curve or surface of the main equipment by the cubic spline interpolation method, as shown in Figure 3:

① In actual operation, parameters such as thermal efficiency and power generation efficiency of the internal combustion generator set change with the change of the partial load rate PLR, as shown in Figure 3(a) and 3(b), which clearly show that when the PLR is low, the parameters of the unit have For this reason, the start-stop coefficient of the unit is set, that is, when the PLR is higher than this coefficient, the unit works normally; otherwise, it stops running, and the power is purchased from the large grid and the auxiliary boiler supplies energy. This can avoid the overall performance reduction of the cogeneration system caused by the light-load operation of the unit;

②The maximum capacity that the refrigerator can provide is not the same under different working conditions. For hot water lithium bromide absorption units, the maximum available capacity is affected by the temperature of the heat source and cooling water. The maximum available capacity of an electric refrigerator is determined by the temperature of chilled water and cooling water. Figures 3(c) and 3(d) show the changes in the capacity coefficient of the refrigerator (the ratio of the available capacity to the rated capacity) after data fitting. Combined with the rated capacity, the absorption refrigerator and electric refrigeration can be calculated under each working condition. The maximum available cooling capacity of the machine;

3.4 Determination of optimization constraints:

①Set the upper and lower limits of the optimization variables to meet the characteristics of the variable working conditions of the equipment;

②Energy balance constraints, that is, to maintain the energy balance of each component in the cogeneration system.

3.5 Establish the optimal design objective function:

maxV＝ω ₁ PESR+ω ₂ ACR+ω ₃ CO ₂ ERR

The energy saving rate of the cogeneration system is defined as:

$\mathrm{<span\; class="notranslate">\; PESR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; SP</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; CCHP</span>}}}{{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; SP</span>}}}$

In the formula, G _CCHP and G _SP represent the annual total energy consumption of the combined power supply system and the distributed power supply system, respectively.

The cogeneration system can recover the increased equipment purchase cost by saving energy costs, that is, the annual cost recovery rate is defined as:

$\mathrm{<span\; class="notranslate">\; ACR</span>}<span\; class="notranslate">\; =</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; d</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; i</span>}}{\overset{\mathrm{<span\; class="notranslate">\; 365</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; j</span>}}{\overset{\mathrm{<span\; class="notranslate">\; twenty\; four</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; sp</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; grid</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; ej</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; sp</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; gas</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; CCHP</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; SP</span>}}}$

In the formula, G _gas represents the total gas energy consumed by the combined power generation system, E _grid is the electricity purchased by the combined power generation system from the large power grid; R _CCHP and R _SP represent the equipment investment costs of the combined power generation system and the distribution system, including biogas investment in pretreatment equipment and biogas storage tank; p _ej is the time-of-use electricity price at moment j, and p _f is the fuel price.

The _CO2 emission reduction rate of the cogeneration system is defined as:

${\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; ERR</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; SP</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; CCHP</span>}}}{{\mathrm{<span\; class="notranslate">\; CO</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; SP</span>}}}$

In the formula, CO ₂ E _CCHP is the annual carbon dioxide emission of the joint supply system, and CO ₂ E _SP is the annual carbon dioxide emission of the separate supply system;

ω ₁ , ω ₂ , and ω ₃ represent the weight coefficients of PESR, ACR, and CO ₂ EER respectively, and satisfy 0≤ω ₁ , ω ₂ , ω ₃ ≤1, and ω ₁ +ω ₂ +ω ₃ =1, where we choose The method of equal weight coefficient means that the three aspects are equally important, ω ₁ =ω ₂ =ω ₃ =1/3.

3.6 Cogeneration system optimization design parameter setting: In addition to internal combustion generator sets and refrigeration units, set equipment efficiency values, carbon dioxide emission coefficients for gas and grid power generation, algorithm parameters, and energy prices, etc. according to the research situation.

3.7 Solving the optimization model:

Select an appropriate optimization algorithm to solve the optimization problem, and obtain the optimal internal combustion generator set capacity, start-stop coefficient and electric refrigeration ratio, and further combine the user load conditions to determine the absorption refrigeration unit, heat exchanger, gas boiler, electric refrigerator and other equipment capacity, complete the optimal design of the small biomass biogas combined cooling, heating and power system.

Now take a single-story office building of a farm in Jinan as an example to illustrate the application effect of the optimal design method of the present invention:

1. The farm has a 10m ³ biogas digester with a daily biogas output of about 400m ³ , of which a single-storey office building is divided into 6 areas with a total area of about 486m ² and an overall height of 3.2m; the lighting load is 11W/m ² , The power consumption of the equipment is 13W/m ² , and the personnel density is 0.1 person/m ² . Through the energy consumption simulation calculation software, the hourly load data of 8760 hours throughout the year is obtained, the maximum electric load is 39kW, and the maximum cooling and heating loads are both 72kW.

2. The structure of the reference distribution system is as follows: the heat load required by the building comes from the gas boiler, and the electric refrigeration unit is responsible for cooling in summer; the electricity used by the building, the electric refrigerator and other equipment is supplied from the coal-fired power plant through the municipal power grid. Assuming that the grid power generation efficiency is 0.35, the transmission efficiency is 0.92, the COP of the electric refrigeration unit is 4.0, and the thermal efficiency of the boiler is 0.85, the total annual energy consumption of the power supply system is calculated to be 4.11*10 ⁵ kWh.

3. The time-of-use electricity price is used for calculation, and the specific setting is that the peak value (11:00～14:00, 18:00～23:00) is 1.070 yuan/kWh, and the average value (7:00～11:00, 14:00 ～18:00) is 0.687 yuan/kWh and the valley value (23:00～7:00) is 0.360 yuan/kWh; the local biogas price and natural gas price are 0.218 yuan/kWh and 0.252 yuan/kWh respectively; at the same time, biogas, The CO2 emission coefficients of natural gas and electricity purchased from the grid are 196g/kWh, 220g/kWh, and 968g/kWh, respectively.

Particle swarm optimization algorithm is used to optimize and solve: the internal combustion generator set capacity N _pgu = 23kW, the unit start-stop coefficient α = 0.22, and the electric cooling ratio θ = 0.12.

According to the above optimization results, the total annual energy consumption of the biogas cogeneration system is calculated to be 2.76*10 ⁵ kWh; the gas consumption is 36107m ³ ; the energy consumption cost is 46578 yuan; the total CO ₂ emission is 75474kg;

The performance of the distribution system is compared with the annual energy saving rate of 32.8%, the annual cost recovery rate of 33.7%, and the _CO2 emission reduction rate of 25.6%. From the results, it can be seen that the optimized design has significant effects in energy saving, economy and emission reduction. .

It is calculated that the annual gas consumption of the natural gas joint supply system is 23183m ³ ; the energy consumption cost is 55015 yuan; the total CO ₂ emission is 81702kg. It can be seen that although the annual gas consumption of the cogeneration system using biomass biogas has increased by 55.7% compared with that of natural gas, the total annual energy cost and _CO2 emissions have decreased by 15.3% and 7.3% respectively. That is to say, compared with natural gas, using biomass biogas as energy can effectively improve the economy of combined cooling, heating and power system.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (6)

1. a small-sized biomass biogas cooling heating and power generation system comprehensive optimization method, is characterized in that, comprise the following steps:

Step one: for the given user that can produce biogas, simulate its typical meteorological year the whole year by time cool and thermal power workload demand, obtain building annual cool and thermal power load curve;

Step 2: the Study on Variable Condition Features of design co-feeding system major equipment;

Step 3: tectonic sieving small-sized biomass biogas cooling heating and power generation system;

Step 4: the optimized variable determining small-sized biomass biogas cooling heating and power generation system, comprising:

The capacity of internal combustion engine generator group, internal combustion engine generator group start and stop coefficient and electricity refrigeration are than three variablees, and wherein electricity refrigeration is than being defined as:

In formula: Q _chand Q _abrepresent the electric refrigerating capacity of electrical chillers and the absorption refrigeration amount of absorption refrigeration unit respectively;

Except internal combustion engine generator group and refrigeration unit, according to the CO2 emission coefficient of investigation situation set device efficiency value, combustion gas and grid generation, algorithm parameter and energy prices;

Step 5: determine to optimize constraint condition; Set up optimal design objective function, divide the fractional energy savings of the system of confession, cost recovery rate with relatively traditional and reduce discharging benefit for integration objective; Solving-optimizing design object function obtains the optimized variable in described step 4, obtains the allocation optimum of system miscellaneous equipment further.

2. a kind of small-sized biomass biogas cooling heating and power generation system comprehensive optimization method as claimed in claim 1, it is characterized in that, in described step 2, co-feeding system major equipment comprises internal combustion engine generator group, lithium-bromide absorption-type refrigerating machine and electric refrigerating machine;

The concrete grammar of the Study on Variable Condition Features design of co-feeding system major equipment is: determine every efficiency parameters according to internal combustion engine generator group part load ratio; The hot water temperature produced according to waste heat recovery and cooling water temperature determination lithium-bromide absorption-type refrigerating machine maximum cooling capacity; Electric refrigerating machine maximum cooling capacity is calculated according to setting chilled water temperature and cooling water temperature; Study on Variable Condition Features curve or face is obtained by spline method matching.

3. a kind of small-sized biomass biogas cooling heating and power generation system comprehensive optimization method as claimed in claim 1, it is characterized in that, in described step 3, small-sized biomass biogas cooling heating and power generation system comprises biogas pre-processing device, gas-holder, internal combustion engine generator group, heat interchanger, donkey boiler, absorption refrigeration unit, electrical chillers and bulk power grid electric power system;

The biogas that biomass anaerobic fermentation produces enters gas-holder after marsh gas purifying equipment, generate electricity for driving internal combustion engine generator group, internal combustion engine generator group exports electric energy supply user, electric refrigerating machine, cooling tower and other equipment electricity consumptions, is auxiliary electric power supply with bulk power system simultaneously; Adopt the heat interchanger abundant Mist heat recovering of water circulation system series system and jacket water waste heat; Reclaim the single-effective absorption refrigerating machine that heat is applicable to drive low capacity; Described donkey boiler is also fuel with biogas, for the heat demand vacancy of replenishment system; Described electrical chillers coordinates Absorption Refrigerator to be user's cooling.

4. a kind of small-sized biomass biogas cooling heating and power generation system comprehensive optimization method as claimed in claim 1, is characterized in that, in described step 5,

The defining method optimizing constraint condition is: in optimization computation process, ensure the balance of internal system cool and thermal power energy, and set the bound of optimized variable, meet the Study on Variable Condition Features of equipment.

5. a kind of small-sized biomass biogas cooling heating and power generation system comprehensive optimization method as claimed in claim 1, is characterized in that, in described step 5,

Optimal design objective function is:

max V＝ω ₁PESR+ω ₂ACR+ω ₃CO ₂ERR

Wherein

In formula, PESR is co-feeding system energy conservation rate; ACR for co-feeding system by economize energy expense with reclaim increase equipment purchasing cost needed for the time limit, i.e. the annual cost recovery; CO ₂eRR is the carbon dioxide discharge-reduction rate of co-feeding system; ω ₁, ω ₂, ω ₃represent PESR, ACR, CO respectively ₂the weight coefficient of EER, and meet 0≤ω ₁, ω ₂, ω ₃≤ 1, and ω ₁+ ω ₂+ ω ₃=1; Max V represents that integrated objective function maximizes; G _cCHP, G _sPbe expressed as co-feeding system and divide for the annual total energy consumption of system, CO ₂e _cCHPfor co-feeding system year CO2 emissions, CO ₂e _sPrepresent point year CO2 emissions supplying system; G _gasrepresent total combustion gas energy that co-feeding system consumes, E _gridfor co-feeding system is from the purchase of electricity of bulk power grid; R _cCHP, R _sPrepresent co-feeding system and the equipment investment cost of dividing for system respectively; E _spthen for dividing the power consumption for system; I and j represent respectively day and hour; p _ejfor tou power price, the p in j moment _fit is then fuel price.

6. a kind of small-sized biomass biogas cooling heating and power generation system comprehensive optimization method as claimed in claim 1, it is characterized in that, according to the optimized variable obtained in described step 4, further combined with the capacity of customer charge determination absorption refrigeration unit, heat interchanger, donkey boiler and electric refrigerating machine, contrast this small-sized biomass biogas cooling heating and power generation system and rock gas co-feeding system at annual air consumption, energy cost and CO ₂the difference of discharge capacity aspect.