Scenario Evaluation of Reversible Solid Oxide Cells Integrated with Local Renewable Energy Sources: Assessment of Different Coupling Applications

Abstract

Solid Oxide Cells (SOCs) are a technology that is currently considered more and more crucial in the present and future world energy scenarios, mainly thanks to their high efficiencies and flexibility of use. One of their most interesting characteristics is their reversibility: such systems are able to work as fuel cells (thus generate heat and power from a wide variety of fuels) or electrolysers (producing hydrogen or even synthetic fuel, when in co-electrolysis mode) in a single unitized system. In addition, thanks to the high operating temperature, SOCs are able to reach higher efficiencies than conventional electrolysers or fuel cells.Moreover, as mentioned above, the possibility to operate SOCs devices in co-electrolysis mode makes them suitable in possible integration/retrofitting solutions with industrial applications, especially if power is generated by Renewable Energy Sources (RES).This is why SOCs could play a decisive role in decarbonizing the stationary CHP (Combined Heat and Power), residential and industrial sectors, considering their wide power range (from less than 1 kWe up to the order of MWe) and their potential in CO2 capture (production of synthetic fuels in co-electrolysis mode). At the same time, they can provide a higher flexibility of the grid in terms of energy storage, oftentimes an issue because of the fluctuation of the power produced, caused by the nature of RES themselves.This work is focused on the analysis of the integration of reversible SOCs in several end-use application scenarios, all in presence of RES systems.Firstly, a thorough research on RES power generation in Italy has been carried out, whose main objective was to quantify the amount of power produced by RES, such as photovoltaics (PV), Wind, Biogas and Hydropower, with respect to the total energy production, in order to evaluate the penetration of RES in each of the zones Italy has been divided into. The research also includes a temporal distribution analysis of power produced by RES.Secondly, the syngas and hydrogen demands all over the Italian territory were assessed.A performance parameter is assigned to every power production source and to the demand for gas (syngas or hydrogen). Such parameter (a number on a scale from 0 to 10) is an indicator of the production from a specific source (or the demand for a specific gas) in a given area (0 representing no production/demand, 10 representing extremely high production/demand).A matrix for each investigated area has been built. It reports the product of the performance parameter of every RES (reported on the columns of the matrix) and the performance parameter assigned to every gas (on the rows of the matrix). The aim of this approach is to evaluate the most suitable macro-scenarios where SOCs can play a major role.The results of the work were an in-depth analysis of the possible case studies, for which the implementation of reversible SOCs at different scales (order of kW, order of hundreds of kW, order of MW) could be convenient. Consequently, the applications identified are those in which both electrical power and syngas/hydrogen supply are demanded.A preliminary high-level simulation of the reversible SOC systems in these scenarios were carried out: their use as electrolysers or fuel cells is handled in order to respectively avoid RES curtailment (when RES production exceeds demand), and increase the efficiency of the system (when RES production cannot match demand).Applications with high level of thermal integration have been favoured, taking into account CHP solutions. Special attention was dedicated to areas with higher RES curtailment rate, in order to minimize the waste of clean energy production. Figure 1