Abstract
Ammonia production currently contributes almost 11% of global industrial carbon dioxide emissions, or 1.3% of global emissions. In the context of global emission targets and growing demand, decarbo...
Highlights
Over the past decade, global carbon dioxide emissions have significantly increased at a rate of 2.4% per year.[1]
From the definition of levelized cost of ammonia (LCOA), the five key variables identified in having the most significant impact on LCOA can be separated into two groups: (a) production cost variables, i.e., levelized cost of electricity (LCOE) and electrolyzer capital expenditure (CAPEX) per kW of rated power, and (b) production process variables, i.e., renewable energy (RE) sources ratio, air separation unit (ASU)/Haber− Bosch (HB) process minimum power consumption (PMIN), and ASU/HB process maximum ramping rate
The results presented here corroborate Beerbühl et al.’s result of ±0.97 GBP/MWh resulting in ±10 GBP/tonne NH39 and correlate well with Institute for Sustainable Process Technology (ISPT)’s finding that a significant reduction in electrolyzer
Summary
Global carbon dioxide emissions have significantly increased at a rate of 2.4% per year.[1]. As part of the methodology we have made some assumptions to simplify the calculations: (1) the operation is assumed to be year round (justified by the impact that operational hours have on LCOA shown by ISPT18), (2) the electrolyzer can ramp instantaneously (0−100% load, justified by hourly resolution of the power data used and that Siemens’ SILYZER 300 has the ability to ramp at 10% rated power per second19), (3) the stored hydrogen can be consumed (“cannibalized”) as input to a PEM fuel cell (with 50% efficiency20) to meet a power deficit [this will be explained in detail as part of the power allocation algorithm (section 2.3.3), but this cannibalization to maintain ammonia synthesis is a costly method that would only be favored in islanded systems with neither grid connection nor alternative dispatchable power sources], (4) the electrical energy consumption for production of hydrogen (53.4 kWh/ kg21), nitrogen (0.119 kWh/kg12), and ammonia (0.600 kWh/ kg,[22] i.e., high-temperature synthesis) is constant, regardless of process load factor, and (5) currently, the model is only looking at the impact of RE intermittency on the process, so steady-state operation is assumed for each time period of operation (dependent on granularity of data). The methodology is largely dependent on the allocation of available RE power to the electrolyzer and ASU/HB units, and is split into seven steps
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