(559f) Ammonia-Based Thermochemical Energy Storage: Design and Optimization of Heat Recovery Cycle Using Conductive Ammonia-Selective Absorbents

Concentrating solar power (CSP) offers large-scale, dispatchable solar electricity that is highly valued for the increased penetration of intermittent renewable energy. However, the levelized cost of electricity for CSP is still higher than the cost targets set by DOE (5¢ per kWh) required for large-scale adoption. Recent empirically-observed learning rates for CSP with thermal energy storage (TES) indicate that there is a significant opportunity for future cost reductions through the development of advanced storage subsystems with reduced cost. To date, three TES pathways have been proposed for the CSP power cycle: sensible heat, latent heat of fusion/vaporization, and thermochemical energy storage (TCES). Each pathway has at least one significant techno-economic or reliability risk. There is ongoing research to design economically viable storage technologies that can be integrated with CSP to offer increased grid reliability and resilience by providing solar dispatchability and grid-support functions.

Ammonia-based TCES (Fig.2) has received attention; a fixed inventory of ammonia-nitrogen-hydrogen mixture undergoes alternating charging (dissociation) and discharging (synthesis) cycles. Ammonia cycling is a promising choice for storage in CSP because:

• it is the most studied process in the chemical industry, with large-scale production optimized over a century. Thus, one can take advantage of existing technology and off-the-shelf catalysts for future Gen3 integrated TCES-CSP.
• there is no side reaction for synthesizing/dissociating ammonia.
• in conventional technology, ammonia can be separated from reactants with condensation.
• reactants are abundant and can be cost-effectively stored using salt caverns or shaft drilling.

Our team is advancing the design of the heat recovery cycle in ammonia-based TCES. This will be achieved by devising advanced separations, derisking the reaction and reactor design, and optimizing the storage using advance process system engineering approaches. In this presentation, I will report on the design and progress in developing a 1 kWh_th heat recovery cycle via reaction-absorption process.