Design and analysis of a solar tower based integrated system using high temperature electrolyzer for hydrogen production

This paper studies the integration of solar tower technology and thermal energy storage (TES) with a power plant and a high temperature Solid Oxide Steam Electrolyzer (SOSE) to produce hydrogen from solar energy. The different subsystems are integrated and optimized to achieve high overall energy efficiency, maintain continuous operation, and reduce exergy destruction. In this regard, energy and exergy analyses are conducted to investigate the requirements and performance of the SOSE while powered by a solar tower subsystem. Therefore, the SOSE cell performance is modeled and the hydrogen production is measured based on different cell and solar field operating conditions. The SOSE is modeled as an integral part of a concentrated solar power plant where the power produced is used for hydrogen production as a final product. In order to maintain continuous plant operation, a TES subsystem is integrated. Furthermore, a supercritical carbon dioxide (s-CO2) Brayton cycle is adapted for the power plant for high efficiency energy conversion from thermal to electric energy. The overall integrated system solar-to-hydrogen conversion efficiency is found to be about 12.7% while charging the TES, and 39.5% while discharging (TES-to-hydrogen). These high efficiencies rank this technology as competitive with other renewable hydrogen production technologies. The integrated high temperature TES achieved energy and exergy efficiencies of more than 96%. The main implementation challenges are discussed in addition to the comprehensive energy and exergy analyses which provide deeper insight into the performance of the system components, potential improvements and limitations. (C) 2015 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.