(415a) Ammonia and Methanol As Sustainable Energy Storage Vectors: A Techno-Economic and Environmental Comparative Analysis

Due to the increasing amount of CO₂ emissions, switching to more sustainable energy sources is becoming more and more pressing.¹At the same time, global energy consumption is forecasted to rise, increasing from about 585 EJ in 2019 to more than 1.5 times the current consumption in 2050.² Within this context, renewable power generation will play a crucial role worldwide through the potential deployment of wind and solar energy at any location of the globe.³ However, the intermittency of such renewable sources calls for sustainable energy storage solutions to deal with the peaks and fill the valleys in wind and solar power generation profiles. Batteries could help cope with the intermittent nature of these renewable energy sources. However, the limited availability of certain materials poses some challenges,⁴ making chemical storage an appealing alternative that is witnessing a surge in interest from the side of investors and policymakers.^5,6

Several chemicals have emerged as suitable energy vectors for stationary and mobile applications, such as hydrogen, ammonia, methanol, and synthetic natural gas (SNG).⁷ The efficient development of such technologies requires comprehensive analyses encompassing all the steps of chemical storage: (1) power-to-chemicals (P2C), (2) storage, and (3) chemicals-to-power (C2P).⁸

To shed light on the role of chemical storage in the energy transition, we evaluated ammonia and methanol energy storage technologies, focusing on the P2C and C2P steps. Electrolytic hydrogen was combined with nitrogen from air to yield ammonia with the Haber-Bosch process for ammonia energy storage.⁹ After a storage period, ammonia was then re-converted into electric energy with an ammonia power plant.¹⁰ Methanol was instead obtained from electrolytic hydrogen and CO₂ from the air, and then converted back to energy at a later stage with a suitable power plant.¹¹ Several scenarios were investigated differing in the storage conditions, covering a range of timeframes and applications. The simulations were implemented in Aspen Plus^® following literature sources.

The selected technologies were benchmarked against other chemical (i.e., hydrogen synthetic natural gas, SNG) and non-chemical storage alternatives (i.e., compressed air energy storage (CAES) and Li-ion batteries). We quantified energy efficiency, cost, and a set of life cycle assessment (LCA) metrics. The latter were evaluated following LCA principles and standard impact methods implemented in SimaPro v9.2,¹² encompassing damages on human health, ecosystems and resources.

Overall, this work sheds light on the potential role of chemicals in energy storage applications, highlighting the pros and cons of the available alternatives. From a broader perspective, this study aims to encourage further holistic analyses of power generation and storage, covering a range of economic and environmental implications.

References

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