Modelling and optimization of a flexible PEMFC power plant for grid balancing purposes

Flexible power resources in the electric system, capable to rapidly ramp their electricity production or consumption, must compensate for the variability given by the increasing penetration of renewable energy sources. The EU project GRASSHOPPER aims to setup and demonstrate a 100 kWel PEM Fuel Cell Power Plant unit which is cost-effective, flexible in power output and scalable to MW-size, designed to provide grid support with a Demand Side Management program. In this work, different layouts proposed for the pilot plant are simulated with Aspen Plus for system performance evaluation, optimization of design and operating conditions. The system may operate at atmospheric or mild pressurised conditions (0.1-0.6 barg), using a compressor and optionally a turbine expander on the cathode exhaust side for energy recovery. The simulation includes a custom PEMFC model, reflecting the voltage dependence on pressure, relative humidity and gas composition. The main BoP components are also modelled in detail (see Figure). The increased voltage of the cell allows a slightly higher net system efficiency with pressurisation (taking into account increased BoP consumption) and the turbine adds nearly 2%pt of net electrical efficiency, reaching 45%LHV. Coolant pump Purge valve