Design And Performance Study Of A Biomass-based Fuel Cell System Integrated With Energy Storage Device

The development of society has created a huge demand for energy and has contributed to the renewal of energy utilization technologies.Distributed energy system is an efficient energy utilization technology which is directly accessible to consumers,reducing energy losses and installation of pipelines over long distance transportation.In addition,it can flexibly use renewable energy sources such as wind,solar,geothermal and biomass,helping to achieve the "double carbon" target.Solid oxide fuel cell is the third generation of fuel cell and it has favoured by researchers in various countries because of its fuel flexibility and high efficiency.Therefore,this paper investigates a biomass-based solid oxide fuel cell distributed energy system for remote mountainous and rural areas with abundant biomass resources.The mathematical models of the biomass gasification system,fuel cell system,waste heat recovery system and energy storage system are established and the main operating parameters are optimized.The capacity and economic feasibility of the system under varying load demand conditions are also evaluated.Finally,the dynamic models of the biomass gasification process and fuel cell operation are developed to further study system stability and economy by scheduling the fuel cell output in advance through load prediction.The main work and findings of this paper are summarized as follows:(1)The waste heat cascade utilization scheme of exhaust gas is analyzed and designed for the application scenario in remote mountainous and rural areas.A micro gas turbine,a two-stage Rankine cycle,a supercritical CO2 power cycle and a direct heating gas waste heat recovery scheme are established.The multi-objective optimization algorithm is adopted to optimize the gasifier operating temperature,water to carbon ratio,the SOFC operating temperature and fuel utilization ratio.The optimized results indicates that the total investment is US$49.4 million when the efficiency of the gasification system reaches 44.0%and the maximum output of this system is 9.1 MW.(2)In order to improve the quality of power supply,the vanadium liquid flow battery energy storage system is introduced to this system.The mathematical model of the vanadium liquid flow battery is developed,and the effects of electrolyte flow rate and charge/discharge current on efficiency are investigated under different state of charge.It is found that properly reducing the current and increasing the electrolyte flow rate can improve the efficiency of vanadium liquid flow battery,especially at the end of charging and discharging.Therefore,this paper adopts a predictive control-based method to improve the charging and discharging efficiency,reaching up to 84%.(3)Finally,the dynamic model of the biomass gasification process and solid oxide fuel cell are developed to investigate the dynamic characteristics of this system and advance scheduling for the system output by predicting the load data,and then investigate the peak regulation capability of this system itself.The results show that a properly planning of the system operation based on the predicted load data can improve the system stability and reduce the investment of energy storage batteries,and the capacity of the energy storage system can meet the demand at 10 MW by optimizing the control strategy in real time.