The Optimal Design Of Photovoltaic/Fuel Cell Power System

Although photovoltaic power generation has been paid extensively attention by people for solar energy's renewable and environmental-friendly characteristics, it also has a drawback:it can not guarantee a continuous supply of electricity in certain weather conditions. As highly complementary of time distribution can be achieved by combination of photovoltaic arrays and fuel cells, so we can ensure stable supply of electricity with photovoltaic and fuel cell hybrid power generation technology. As a well-structured independent power system, photovoltaic fuel cell hybrid power system is becoming an effective means to solve the energy shortage and environmental pollution. There are many studies on the photovoltaic fuel cell hybrid power system performance and computer simulation, but the study of system modeling and optimization of design is not deep enough. The paper studies on small-scale photovoltaic fuel cell hybrid power system, sets up a mathematical model of main modules of the system, then studies laws of match between modules, initially develops software to optimization design of the system.First of all, according to structural features of photovoltaic fuel cell hybrid power system, we proposed the "modular" modeling strategy and establish the mathematical model for each configuration of the system. We calculate the optimal angle for installation photovoltaic arrays of the system with the using of least square method, calculate hourly solar radiation of tilted surface with the Perez model, then establish mathematical model of PV generation system. Taking into account of the requirements of effectiveness and simplicity for fuel cell power generation system, the combining modeling of mechanism model and empirical model is proposed:the fuel cell gas partial pressure fuel cell is determined by assuming that model's working conditions, according to Nernst equation that concentration, temperature has influence on the actual cell potential, mathematical expression of the ideal voltage of fuel cells are derived Based on experimental data and empirical model, activation over-voltage and Ohm over-voltage of fuel-cell are calculated, and then we establish the mathematical model of fuel cell power system.On the ground of mathematical model for main module in the system, the paper optimizes matching system design according to the control strategy of give priority to the energy level. The paper proposed optimization algorithms and precision analysis, taking net present value cost of the system as the optimization goal as well as electric reliability as constraint condition, software for system optimization design is initial developed. Using the software, we evaluate economical, technical and environmental efficiency of design proposal for PV/fuel cell hybrid energy system.