Spatial variation in cost of electricity-driven continuous ammonia production in the United States

Abstract

Cost-effective, low-carbon ammonia production is necessary for decarbonizing its existing uses, but could also enable decarbonization of other difficult-to-electrify end uses like shipping where energy density is a key criterion. Here, we assess the levelized cost of ammonia production (95% availability) at industrial-scale quantities (250 tonnes/day) in 2030 from integrating commercial technologies for renewable electricity generation, electrolysis, ammonia synthesis and energy storage. Our analysis accounts for the spatial and temporal variability in cost and emissions attributes of electricity supply from variable renewable energy (VRE) sources and the grid, and its implications on plant design, operations, cost and emissions. Based on 2030 technology cost and grid projections, we find that grid-connected ammonia in the midcontinental U.S. costs 0.54-0.64 $/kg, as compared to 0.3-0.4 $/kg for natural gas-based ammonia and depending on the generation mix of the grid, may have higher or lower CO2 emissions. Fully VRE-based ammonia production, even with simultaneous wind and PV utilization, is more expensive than grid connected outcomes, due to the need for storage to manage VRE intermittency and continuous ammonia production. Instead, using VRE and grid electricity for ammonia production under moderate carbon policy (50$/tonne CO2 price) in the midcontinental U.S. can achieve 55-100% CO2 emissions reduction per tonne of ammonia compared to natural gas routes and corresponds to levelized cost range of 0.54-0.63 $/kg NH3). Further cost reductions are shown to be possible if the ammonia synthesis loop can be made more flexible, which reduces the need for round- the-clock electricity supply and the substitute use of battery storage with ammonia storage.

Cost and Performance Targets for Fully Electrochemical Ammonia Production under Flexible Operation

“…We used the model to explore the system dynamics, ammonia synthesis cost, and performance requirements to achieve cost parity with both conventional fossil-fuel based ammonia production ($0.4-0.7/kg) and electrolytic hydrogen-coupled with Haber-Bosch based ammonia ($0.8-1.0/kg). 18 The flexible, fully electrochemical approach utilized little high-cost battery and hydrogen storage, instead utilizing inexpensive ammonia storage to counter the intermittent nature of renewable electricity generation.…”

“…Further details on VRE resource characterization are provided elsewhere. 18,57 Solar and wind capacity factors from 2011 were used for this study, as the weather patterns in that year were more representative of the average.…”

“…at costs of <1 $/kg NH3, with processes using renewable electricity-based-hydrogen coupled with the traditional Haber-Bosch process. Processes which utilize water-splitting derived hydrogen and traditional Haber-Bosch reactors report ammonia costs of 0.8-1.2 $/kg NH3, [18][19][20][21] though there are reports of ammonia costs in the 0.4-0.6 $/kg NH3 as well. 22 However, there are several drawbacks to these processes that could make a fully electrical ammonia production approach attractive.…”

“…On the basis of the above results, we sought to outline key targets for the economic viability of an electrochemical ammonia synthesis process. The cost target used for economic comparisons was one for ammonia produced via the thermochemical Haber–Bosch process using water-splitting-derived hydrogen as a feedstock; the cost of this ammonia is 0.8–1.0 $/kg . The flexible, fully electrochemical approach utilizes little high-cost battery and hydrogen storage, instead utilizing inexpensive ammonia storage to counter the intermittent nature of renewable electricity generation.…”

Spatial Variation in Cost of Electricity-Driven Continuous Ammonia Production in the United States

“…The findings reported here are adapted from the Master’s thesis submitted by A.B. to complete his thesis requirements, and previous versions of these case study results are archived in the university thesis repository . The authors thank Jack Morris at the MIT Energy Initiative for generating the renewable resource profiles for the various locations.…”