In concentrating solar power (CSP) applications, Thermochemical Energy Storage (TCES) refers to the process of chemically storing and releasing concentrated sunlight to produce solar electricity. TCES technologies allow CSP production to continue after the sun goes down and during cloudy conditions. TCES offers longer term, denser energy storage than other sensible and latent heat storage methods and can be coupled to efficient, high-temperature power cycles.
One form of TCES involves reduction-oxidation reactions of a metal oxide material. In the first step, the metal oxide is reduced by concentrated sunlight. This reaction produces oxygen and the metal in a pure or lower oxidation state, and stores the solar energy in a stable chemical form. In the second step, the reduced metal oxide is re-oxidized back into its original chemical form by an airstream. This reaction releases the stored energy, which heats the airflow. When the second step occurs at an elevated pressure, the compressed, high-temperature airflow can be expanded through a gas turbine to produce electricity. The process is oxygen-neutral, allows recycling of the TCES material, and produces no direct greenhouse gas emissions.
TCES at the Solar FTL
The Solar FTL participates in a variety of TCES research. Our efforts include:
· Study of fundamental thermodynamic, kinetic behavior of redox materials
This work allows us to identify materials whose reaction behavior is compatible with the operating temperatures of CSP processes, and which materials react at a rate and manner that allows rapid, efficient, and dense energy storage.
· Modeling and optimization of solar reactor technologies
Solar reactors should absorb a large percentage of incident concentrated sunlight, reduce all or most of the TCES material, and withstand the high flux, high temperature conditions in which they operate. Detailed modeling and lab-scale testing allow us to design and improve solar reactors.
· Design and synthesis of state-of-the-art TCES materials
By experimenting with new metal combinations and dopants, researchers can tune TCES materials and the conditions under which they react to specific operating ranges. Synthetic TCES materials also can be designed to improve their stability, reaction rates, and energy storage capacity relative to existing candidates.
For more information on the Solar FTL’s TCES research, please see our following publications: