Coupling of a Solid-oxide Cell Unit and a Linear Fresnel Reflector Field for Grid Management

Recent analyses on energy scenarios for countries with high contribution of intermittent renewables point out that electricity generation from solar and wind energy may exceed the overall electricity demand during a large number of hours per year (that include peak periods). Thus, large-scale electrical –energy storage systems are required for grid balancing. Hydrogen production through solid-oxide electrolysis cells (SOEC) stands for promising power storage systems due to its high capacity and wide variety of applications. SOEC operates with steam in the range of 600-1000 °C, which, in this work, is supplied by a concentrating solar system. Based on its simplicity and low cost of the components, a linear Fresnel reflector coupled with castable ceramic thermal energy storage system was selected. Thermal oil was retained as heat transfer fluid avoiding phase change through the solar receiver. The heat is stored during the day for later use by the SOECs.The proposed hybrid plant, located in Seville, Spain, is analyzed under two scenarios. In the first one, the Solid-Oxide unit is only used as steam electrolyser producing hydrogen that is directly sell to a hydrogen bus refueling station. In the second case, the device operates either as electrolyser or fuel cell, generating hydrogen that is stored and later used to produce electricity during peak periods. The capacity of the plant operating under both scenarios has been evaluated as a function of the storage capacity.