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Abstract
Ammonia produced from renewably sourced electrolytic hydrogen has considerable promise as a seasonal energy storage medium to enable high renewable penetration in the electrical power generation mix. Long duration energy storage via ammonia is significantly less expensive than using hydrogen or batteries [1,2]. Renewable ammonia can also be used as in its traditional application as a fertilizer to reduce agricultural carbon intensity. These multiple renewable ammonia use cases give rise to opportunities for sector coupling [3]. For example, an electric utility could deploy ammonia for energy storage while also pursuing additional ammonia production for sale in local agriculture markets. This energy-agriculture coupling would enable the utility to monetize otherwise curtailed renewable generation.
Maximizing the economic benefit of ammonia-based sector coupling requires a coordinated approach which accounts for the plethora of available process technologies and projections for their cost and performance improvement, impending public policy, demand growth, and potential revenue streams on a multi-decade timescale while also accounting for renewable intermittency on short-term (less than a day) and seasonal timescales. To this end, we have developed a combined investment planning and scheduling model which systematically minimizes energy system net present cost by (i) determining optimal energy generation and storage installation over consecutive multi-year investment periods while (ii) simultaneously scheduling hourly operation (i.e., production rates, storage inventories, commodity purchases/sales) over a representative yearly operating horizon for technologies installed in each and all previous investment periods. Accounting for hourly scheduling at the design stage ensures both short-term and seasonal operational reliability without unnecessary, expensive oversizing [4].
In this work, we present an energy-NH3 sector coupling case studies for Southern California using the CIPS model. We consider 500 MW power demand balancing areas with existing wind and solar generation representative of the region’s power supply mix: on an annual basis, 14% solar and 7% wind [5]. We determine the optimal investment pathway for additional solar and wind generation as well as energy storage to reach 100% renewable energy supply by 2040. Specifically, we include candidate technologies for ammonia, hydrogen, and battery energy storage pathways which may be complimentary across different timescales. We also allow for ammonia sales to the state agriculture sector or as a hydrogen carrier to be cracked at fueling stations to help defray the costs of this renewable energy transition. We examine the potential of such sector coupling to reduce the net present cost of this energy system. Ultimately, this work aims to answer the important question: What role does ammonia play in the most economical path to 100% renewables?
References
[1] Smith et al. (2020). Energy Environ. Sci. 13(2), 331-344.
[2] Cesaro et al. (2021). Applied Energy, 282, 116009.
[3] Demirhan et al. (2021). Applied Energy, 281, 116020.
[4] Palys & Daoutidis. (2020). Comput. Chem. Eng. 136, 106785.
[5] U.S. EIA. (2020). State Electricity Profiles: https://www.eia.gov/electricity/state/
