Techno-enviro-economic evaluation of decentralized solar ammonia production plant in India under various energy supply scenarios

The growing potential for ammonia as an energy carrier and the need to minimize environmental emissions have created a demand for green and decentralized ammonia production (power-to-ammonia) as an alternative to conventional processes. One of many alternatives is to use a Haber-Bosch process where hydrogen is synthesized using electrolysis, and nitrogen is obtained via an air separation unit utilizing electricity from various sources, having their own economic and environmental implications. This study presents a detailed economic and life cycle assessment comparing four different energy supply scenarios in India for decentralized ammonia production based on low pressure (80 bar). A 150 MW polymer electrolyte membrane water electrolyzer (PEMWE) modeled using the Aspen custom modeler is utilized for hydrogen generation, and subsequent ammonia production has been modeled using Aspen Plus (R). Energy consumption analysis indicates the power consumption of PEMWE to be 83.59 percent. The minimum levelized cost of ammonia, $1106/ton of ammonia, is obtained by combining a local solar plant and the grid. Moreover, ammonia production using a solar photovoltaic (SPV) plant has the minimum environmental impact, with a global warming potential of 0.305, compared to 13.98 kg of carbon dioxide equivalent produced per kg of ammonia using grid electricity. However, such plants are not economically viable in locations with very low solar availability. Combining an SPV system with battery energy storage has been found to be environmentally viable; however, it is the most expensive alternative of all the scenarios considered. The sale of oxygen can have an added benefit on the cost and may result in a levelized cost of $672/ton of ammonia in 2030 with a projected electrolyzer cost of $264/kW.