Performance Optimization And Anode Degradation Research Of SOFC Integrated System Driven By Renewable Energy

With the rapid growth of population and economy,the energy supply is getting tighter and the environmental protection situation is getting more severe,along with the rapid increase of urban population has produced a large amount of municipal domestic waste(MSW).Solid oxide fuel cell(SOFC)as a new type of energy conversion device that converts the chemical energy of fuel directly into electrical energy.It has the advantages of high power generation efficiency,low pollution emission and wide fuel adaptation,and can also produce methane(CH4)as SOFC reaction gas by anaerobic digestion(AD)reaction of MSW.Given the high operating temperature of SOFC,its exhaust waste heat utilization is of great value and can be considered to improve the overall energy conversion efficiency which integrating with the system driven by medium to low temperature heat source.However,the commercial application of SOFC systems is facing some problems that need to be solved,such as high cost and poor reliability,degradation of SOFC performance due to long-term operation,especially the anode material coarsening of the anode has an important impact on the performance degradation of anodesupported SOFC.This study proposes an integrated SOFC energy system driven by coupled solar and biomass energy,and a three-dimensional(3-D)numerical model of SOFC is also established,then the thermodynamic performance and economic cost as well as the degradation mechanism of SOFC are evaluated by integrating parameter analysis,surrogate model,CFD modeling and multi-objective optimization.The main contents are drawn as follows:Firstly,a zero-dimensional(0-D)mathematical model of SOFC is established,and the accuracy of the proposed model is verified by comparing with the experimental data.Then the SOFC-PTSC-AD-ORC-KC system is established,and the thermodynamic performance and economy analysis are studied.Under the design conditions,the results show that the total exergy efficiency and cost of the system are 30.96%and 19.68$/h,respectively.The system’s exergy loss is mainly caused by the pre-heater,stack and combustor of the SOFC.It’s found that the total exergy efficiency is increased as the increase in the evaporating pressure of ORC and the ammonia concentration of Kalina cycle(KC),but it’s decreased with the increase in the solar radiation intensity.When the input temperature and the current density of SOFC are increased,the total exergy efficiency is increased firstly then decreased and reached the maximum value of 439.2 and 481 kW at the input temperature of 628.6℃ and the current density of 8286 A/m2.Besides,the cost rate is increased with the main components’ power consumption increasing.Secondly,considering the complex internal structure and the large number of parameters involved of SOFC,the key parameters of the integrated energy system are used as input variables,an improved artificial neural network(ANN)algorithm combining data-driven surrogate model and whale optimization algorithm(WOA)as surrogate model to predict the exergy efficiency and economic cost of the proposed system.The results show that the coefficient of determination(R2)of WOA-ANN for the prediction of the exergy efficiency and economic cost of the proposed system is 0.9978 and 0.9999.then the Pareto frontier is obtained by using the non-dominated sorting whale optimization algorithm(NSWOA)which is employed to perform the multi-objective optimization,and the comprehensive decision-making method(TOPSIS)is used to get the optimal solution.The optimal solution shows that the total exergy efficiency and the cost rate could reach 39.56%and 14.23 $/h,respectively.It is also found that the time using the surrogate model to obtain the optimal solution set spends only 5 minutes which is far less than the physical method which spends more than 40 hours under the same computer configuration.Finally.A 3-D fine-mesh flow field model of SOFC is established,and the accuracy is verified by comparing the polarization curves of experimental data,then the anode degradation model of SOFC is established.The results show that the average current density of SOFC is decayed from 1.0202A/cm2 to 0.8807A/cm2 under the design conditions.The effects of SOFC operating parameters and microstructure parameters on SOFC performance degradation are analyzed.The results show that the higher the operating temperature,the higher the average current density of SOFC.but at the same time the anode degradation also increases;the increase of the initial Ni atomic size increases the anode degradation of SOFC and decreases the average current density of SOFC;the effect of YSZ particle size and Ni volume fraction on the SOFC performance is the opposite of the initial Ni atomic size,the average current density of SOFC increases with the increase of YSZ particle size and Ni volume fraction,and the anode degradation also decreases.The average current density of SOFC increases with the increase of YSZ particle size and Ni volume fraction,and the anode degradation is also alleviated;the same multi-objective optimization is performed using NSWOA-Ⅱ and the optimal operating point of SOFC for long time operation is obtained by TOPSIS decision method,and the results show that the average current density of SOFC reaches 1.1043 A/cm2 under the optimal operating condition,and the degradation rate is reduced to 0.5147%/kh.