Thermochemical energy storage with ammonia and implications for ammonia as a fuel


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This seminar presents recent advances in ammonia-based thermochemical energy storage1 (TCES), supported by an award from the US Department of Energy SunShot program. The goal of SunShot is to “reduce the total installed cost of solar energy systems to $.06 per kWh by 2020.” Within the arena of concentrating solar thermal power, Sunshot has established goals for each subsytem, including reducing the cost of the energy storage subsystem to $15 per kWht of stored energy and enabling working fluid temperatures greater than 600°C, consistent with advanced, high performance power blocks.

Schematic of an NH3-based thermochemical energy storage system.
Schematic of an NH3-based thermochemical energy storage system.

In ammonia-based TCES (see figure), ammonia is dissociated endothermically (NH3 + ΔHr → 1/2 N2 + 3/2 H2) as it absorbs solar energy during the daytime. When energy is required, the reverse reaction releases energy to heat a working fluid such as steam, to produce electricity.

The main focus of our research has been ammonia synthesis using the Haber-Bosch process, with an emphasis on achieving high temperatures, and doing so cost-effectively. This talk will present results of our modeling and experiments of ammonia synthesis used to produce 650°C steam for a supercritical steam Rankine cycle. The implications for synthesis of ammonia for use as a fuel will also be discussed.

1). R. Dunn, K. Lovegrove, and G. Burgess, 2011 “A Review of Ammonia-Based Thermochemical EnergyStorage for Concentrating Solar Power,” IEEE, Vol.100, No. 2, pp. 391-400.