Optimal design and operation of resilient power systems with ammonia-based energy storage.

Abstract

The increasing penetration of intermittent renewable generation, the electrification of new sectors, and the growing need for resilience against extreme events have introduced significant complexity into the planning and operation of power distribution systems. Energy storage technologies offer critical flexibility and resilience enhancement, but existing solutions like stationary lithium-ion batteries have limitations in scalability, long-term storage, and cost. This thesis uses optimization to investigate the potential of ammonia-based energy storage systems, particularly mobile ammonia-powered generators, as non-wires alternatives and resilience-enhancing measures for power distribution networks. First, we propose an optimization model that determines the optimal combination of investments into mobile ammonia-powered generators, ammonia storage tanks, and mobile batteries to satisfy all power demands in multiple operational scenarios. A case study is performed to assess the optimal use of ammonia storage technologies alone and in coordination with batteries. We ultimately find that it is optimal to coordinate ammonia-powered generators with batteries, and that ammonia-powered generators are well-suited for high-total-energy use cases. Next, we address the challenge of optimizing large-scale, two-stage stochastic programs with mixed-integer recourse, a problem structure that emerged in the resilience-focused part of this study. A modification to the integer L-shaped method with alternating cuts is proposed that terminates mixed-integer subproblems early to generate looser cuts that still advance the solution of the Master Problem. Two case studies demonstrate that the proposed algorithm has improved scaling with subproblem size and complexity. Finally, the developed algorithm is applied with problem-specific modifications to optimize the investment and coordinated operation of the following resilience-enhancing measures: mobile ammonia-powered generators, mobile batteries, line hardening, and feeder reconfiguration. The measures are used to address multiple uncertain stressors, including line failures, uncertain loads, distributed generation variability, and volatile electricity prices. Two case studies demonstrate that mobile ammonia-powered gensets and batteries are effective resilience-enhancing measures, especially when used together, due to their operational flexibility. Additionally, we find that ammonia-powered generators are well-suited to respond to line outages due to their large storage capacity. We also demonstrate the importance of considering multiple disruptions in resilience planning.