Simulation of direct coupling 20 kW class photovoltaic and electrolyzer system connected with lithium ion capacitors

Abstract

The 20 kW class Proton Exchange Membrane (PEM) type Water Electrolyzer (Ely) system directly coupled with photovoltaic panels (PV) was developed. In this system the number of Ely cells is changeable during operation to truck maximum power point of the PV by adjusting operation voltage. Since neither DC/DC converters nor power conditioners are used in this system, there are no power conversion loss, however the input current into Ely fluctuates due to the fluctuation of the irradiation. Lithium ion capacitors (LiC) are incorporated into PV-Ely system in order to smooth the Ely input current, that would stabilize the pressure of generated hydrogen gas and extend the lifetime of the Ely cells. Before the examination using the facility, the simulation program for the 20 kW PV-ELY-LiC system was developed. The program can simulate the operation condition of the system each one second. The simulation program can be used to estimate the current smoothing effect by the LiC. The simulation program can also contribute to a preparatory experiment and tuning of parameters in the control program for the system.