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

Abstract

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 (H2). 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 H2 production cost in a hybrid ceria cycle, in which excess heat produces electricity in an organic Rankine cycle, to increase revenue and decrease H2 cost. The estimated H2 cost from such a co-generation multi-tower plant is still relatively high at $4.55/kg, with an average H2 production of 1431 kg/day per 27.74 MWth tower. Sensitivity analyses show opportunities and challenges to achieving $2/kg H2 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 H2 remains challenging with ceria as the active material and likely will require a new material.