Techno-economic analysis of thermochemical water-splitting system for Co-production of hydrogen and electricity

The two-step thermochemical metal oxide water-splitting cycle with the state-of-the-art material ceria inevitably produces unutilized high-quality heat, in addition to hydrogen (H-2). This study explores whether the ceria cycle can be of greater value by using the excess heat for co-production of electricity. Specially, this technoeconomic study estimates the H-2 production cost in a hybrid ceria cycle, in which excess heat produces electricity in an organic Rankine cycle, to increase revenue and decrease H-2 cost. The estimated H-2 cost from such a co-generation multi-tower plant is still relatively high at $4.55/kg, with an average H-2 production of 1431 kg/day per 27.74 MWth tower. Sensitivity analyses show opportunities and challenges to achieving $2/kg H-2 through improvements such as increased solar field efficiency, increased revenue from electricity sales, and a decreased capital recovery factor from baseline assumptions. While co-production improves overall system efficiency and economics, achieving $2/kg H-2 remains challenging with ceria as the active material and likely will require a new material. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study investigates the potential of utilizing excess heat from the ceria cycle for co-production of electricity to increase value. Although integrating an organic Rankine cycle to produce electricity can reduce hydrogen production costs, achieving $2/kg H-2 remains challenging with ceria as the active material.