Decarbonizing the energy supply chain: Ammonia as an energy carrier for renewable power systems
Chong Wei Ong, Nairen Chang, Meng‐Lin Tsai, Cheng‐Liang Chen
Abstract
Growing global awareness of global warming has led to a focus on reducing greenhouse gas emissions and promoting renewable energy. Energy storage is essential for ensuring a reliable power supply due to the intermittent nature of renewables. While green hydrogen (H 2 ) is considered a clean energy carrier, it faces challenges such as high cost, safety concerns, and low volumetric energy density. In contrast, safer and cost-effective ammonia (NH 3 ) offers higher volumetric energy density for storage. The study explores the Electricity-H 2 -NH 3 -H 2 -Electricity system, a promising low-carbon global renewable electricity transportation avenue. It involves an Aspen Plus process simulation, encompassing air separation, NH 3 synthesis, and H 2 generation from the NH 3 decomposition process. We analyze renewable energy sources, NH 3 transportation, process mass balance, and energy consumption and conduct economic and CO 2 analyses. Three scenarios (current, near future, sustainable future) with varying technology levels and costs are presented. The findings reveal that 11.044–9.349 MWh of renewable electricity in exporting countries generates 1 tonne of NH 3 , then split, with 0.17 tonnes combusted to provide heat for the decomposition process and the remaining 0.83 tonnes converted to produce 0.145 tonnes of H 2 . This H 2 is sent to fuel cells, yielding 1.711–2.436 MWh of imported electricity to the grid, with 575–141 USD/MWh cost. Additionally, the imported NH 3 and H 2 incur costs of 0.719–0.289 USD/kg and 5.993–2.362 USD/kg, respectively. Considering the heat integration of the fuel cells and NH 3 decomposition process, an additional 23 % of H 2 production is achieved (0.178 tonnes), and a 34 % increase in imported electricity is sent to the grid (2.370–3.259 MWh). This leads to a 27 % decrease in imported renewable energy costs (432–103 USD/MWh) and a 29 % reduction in H 2 costs (4.087–1.666 USD/kg); the ultimate CO 2 emission of the system is 318–36 kg/MWh.