Dynamic modeling and simulation of a power-to-power energy storage system based on hydrogen

The goal of this thesis is to model and evaluate the dynamic behaviour and performances of a power-to-power (P2P) energy storage system installed in remote area, where there is no connection with the electrical grid and power is supplied by renewable energy sources (RES). The model has been developed in MATLAB-Simulink® environment, starting from single components and then constructing the whole system, also introducing control strategies. Single component models have been developed relying on an extensive research in literature, studying mass and energy balance equations, in addition to mass transport, thermal, electrical and electrochemical phenomena. The modelled system is composed by a proton exchange membrane water electrolyzer (PEMWE), a pressurized hydrogen storage tank, a proton exchange membrane fuel cell (PEMFC). The model has been validated by performing the best fit of PEMWE and PEMFC polarization curves available in literature, using the Simulink® Parameter Estimator tool in order to evaluate fitting parameters. The analysis has been carried out evaluating the dynamic behaviour and performances of such system in different scenarios (i.e. a working day and a non-working day for each month of the year) to observe its response to various power profiles. The results consist of daily power profiles, which show the dynamic response of the system and a table reporting all key performance indicators (KPI) that have been considered for this study. The main result is that such system can increase a lot the self-sufficiency of isolated users supplied by RES, even if certain amount of surplus in energy production from RES needs to be curtailed in most of the cases. Furthermore, in the simulation results, the load is always covered either directly by RES production or by the P2P system. Thus, the consumption associated to the backup system (i.e. diesel generators), which intervenes when the load is totally or partially not covered, is negligible. In addition to the main simulation results, further analyses have been conducted on the optimal sizing of RES systems, the exploitation of curtailed energy for local hydrogen mobility and the evaluation of the costs related both to different sizes of RES systems and to hydrogen and battery energy storage systems. From such analyses, it has been found that the sizes of the RES systems can be reduced leading to lower costs and that the cheapest energy storage system is the one based on hydrogen. In conclusion, it can be stated that such system could lead to higher self-sufficiency, higher exploitation of RES and negligible contribution of the backup system, with consequent reduction of greenhouse gases (GHG) emissions. The model developed in this work could be used to simulate and investigate the dynamic response of a P2P system according to different operating conditions in order to predict and optimize its performances.