Research On Optimization Of Operation Strategies Of Three-staged Thermostatic Biogas Production System Heated By Solar Energy

Solar energy and biomass energy are two types of abundant renewable energy in ruralareas. And due to the high efficient and low cost of their utilization they are quite importantfor improving the living environment, ecological environment in rural areas and satisfyingrural multi-level demand for energy.Based on the the characters that the economical heat-collecting temperature of solarenergy could be accordance with the high efficient thermostatic anaerobic fermentationtemperature of biomass energy, our team proposed three-stage thermostatic biogas productionsystem heated by solar energy and studied the performance of this system in the early days.And the research mainly focused on the research of the single biogas fermentation deviceheated by solar energy and the three stage thermostatic biogas production system combinedwith heating and power system (CHP) or cooling, heating and power system (CCHP). On thebasis of the prior research, in order to realize the biogas production thermostatically with highefficient and low cost, this subject studied on optimization of operation strategies ofthree-stage thermostatic biogas production system heated by solar energy. The main researchcontents and conclusions are as follows:(1) Rest on the established the three-stage thermostatic biogas production system heatedby solar energy in Gaolan, Lanzhou, this article established the optimization model ofoperation strategies which regards the biogas production maximization and the cost of thebiogas units minimization as the objective functions, separately, and the positive of differenceof energy input and output of system as the constraint condition.(2) It established the model of energy input and output of the system. The model ofenergy input of the system included: the model of the heat of the daily feed into the system,the model of solar energy absorbed by solar collectors, the model of electric powerconsumption of five recycle pumps. The model of energy output of the systems included: themodel of the heat of the daily effluent out of the system, the model of the heat taken away bydry methane and the water vapour, the model of heat loss of digesters and the heat storagetank.(3) Rest on meteorological construction data of Lanzhou, this article calculated theenergy input and output of the system operated with fresh-cattle manure or mixed fresh-cattlemanure and cabbage which concentration is8%.Then, based on the optimization model, itchose the optimal operation strategy for the system operated with fresh-cattle manure or mixed fresh-cattle manure and cabbage which concentration is8%, compared the optimaloperation strategy with the original operation strategy, and analyzed the economic efficiencyof the optimal operation strategy. When the raw material is fresh cattle manure whichconcentration is8%, the objective function-the biogas production maximization or theobjective function-the cost of the biogas units minimization are in accordance with each other.January's strategy is NO.1digester operated under30℃, NO.2digester operated under37℃and NO.3digester operated under37℃, the strategies of February to November are NO.1digester operated under37℃,NO.2digester operated under37℃and NO.3digester operatedunder37℃, December's strategy is NO.1digester operated under30℃, NO.2digesteroperated under37℃and NO.3digester operated under30℃. After comparing with thesystem's original operation strategy which is NO.1digester operated under30℃, NO.2digester operated under30℃and NO.3digester operated under30℃, the result shows thatwhen the system operates with the optimal strategy, the biogas production of the system raises45.14%, the cost of biogas units reduces22.20%annually. And when the system regardsmixed fresh-cattle manure and cabbage which concentration is8%as the raw material, theoptimal operation strategy for the objective function-the biogas production maximization isJanuary's is NO.1digester operated under37℃, NO.2digester operated under37℃andNO.3digester in30℃, February's strategy is NO.1digester operated under52℃, NO.2digester in52℃and NO.3digester under37℃, the strategies of March to October are NO.1digester operated under52℃, NO.2digester operated under52℃and NO.3digester in52℃,November's strategy is NO.1digester operated under52℃, NO.2digester operated under37℃and NO.3digester in37℃, December's strategy is NO.1digester operated under30℃,NO.2digester operated under37℃and NO.3digester operated under30℃. After comparingwith the system's original operation strategy which is NO.1digester operated under30℃,NO.2digester operated under30℃and NO.3digester operated under30℃, the result showsthat when the system operates with the optimal strategy, the biogas production of the systemraises81.62%annually. Besides, the optimal operation strategy for the cost of the biogas unitsminimization is January's strategy is NO.1digester operated under37℃,NO.2digesteroperated under37℃and NO.3digester operated under30℃, the strategies of February toNovember are NO.1digester operated under37℃, NO.2digester operated under37℃andNO.3digester operated under37℃, December's strategy is NO.1digester operated under30℃, NO.2digester operated under37℃and NO.3digester operated under30℃. Aftercomparing with the system's original operation strategy which is NO.1digester operatedunder30℃, NO.2digester operated under30℃and NO.3digester operated under30℃, theresult shows that when the system operates with the optimal strategy, the cost of biogas unitsreduces19.75%annually. No matter the raw material is fresh cattle manure or mixed fresh-cattle manure and cabbage which concentration is8%, when the system operates withthe optimal strategy, it could operate steady and produce biogas continuously and efficiently.Meanwhile, some remanent hot water could be provided each month.The innovation of this subject is as follows: based on the experimental data. The optimaloperation strategy and its economy of three-stage thermostatic biogas production systemheated by solar energy are obtained.The research method of the subject follows the principle named 'TemperatureCorrespond to the Cascade Utilization', and the research result has not only the crucialguiding role for the popularization and application with high efficient and low cost ofthree-stage thermostatic biogas production heated by solar energy, but also the significantreference role for the development and utilization on a large-scale of solar energy and biomassenergy with high efficient and low cost.This work was supported by National Natural Science Foundation of China(51166008/E0607), Key Technologies R&D Program of China (2011BAD15B03), ChinaSpark Program (2010GA860004), Research Foundation of Education Bureau of Gansu(0803-06), Longyuan Youth Innovative Support Program (09-0165), Construction Science andTechnology Development Program of Gansu (JK2010-29),Tamarisk Outstanding TalentProgram of Lanzhou University of Technology (Q201101).