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

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.

In ammonia-based TCES (see figure), ammonia is dissociated endothermically (NH₃ + ΔH_r → 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.