Article: Exergetic comparison of a novel to a conventional small-scale power-to-ammonia cycle Journal: International Journal of Exergy (IJEX) 2023 Vol.42 No.2 pp.127 - 158 Abstract: Green ammonia is a promising carbon-free energy vector and means to store hydrogen efficiently. Employing the software Aspen Plus®, this work presents an exergetic comparison of a novel small-scale power-to-ammonia system, to be tested in 2023 and designed for low investment cost and dynamic flexibility, to a conventional system. For a thorough evaluation six equations of state, one provided by an industry partner, as well as chemical exergies with and without excess values are compared. With 64.59%, the novel design has a 4.87% lower exergetic degree of efficiency. The difference can be attributed to the simplified design of the novel cycle, mainly to the use of an electrical preheater instead of an internal gas-gas heat exchanger and a recycle valve instead of a recycle compressor. However, an upcoming exergy economic analysis will show that the novel cycle is more economical overall, as its investment costs are lower. Inderscience Publishers - linking academia, business and industry through research

Title: Exergetic comparison of a novel to a conventional small-scale power-to-ammonia cycle

Authors: Pascal Koschwitz; Daria Bellotti; Cheng Liang; Bernd Epple

Addresses: Institute for Energy Systems and Technology, Technical University of Darmstadt, Otto-Berndt-Str. 2, 64287 Darmstadt, Germany ' Thermochemical Power Group, Dipartimento di Macchine Sistemi Energetici e Trasporti, University of Genova, Via Montallegro 1, 16145 Genova, Italy ' Proton Ventures B.V., Karel Doormanweg 5, NL-3115, JD, Schiedam, The Netherlands ' Institute for Energy Systems and Technology, Technical University of Darmstadt, Otto-Berndt-Str. 2, 64287 Darmstadt, Germany

Abstract: Green ammonia is a promising carbon-free energy vector and means to store hydrogen efficiently. Employing the software Aspen Plus®, this work presents an exergetic comparison of a novel small-scale power-to-ammonia system, to be tested in 2023 and designed for low investment cost and dynamic flexibility, to a conventional system. For a thorough evaluation six equations of state, one provided by an industry partner, as well as chemical exergies with and without excess values are compared. With 64.59%, the novel design has a 4.87% lower exergetic degree of efficiency. The difference can be attributed to the simplified design of the novel cycle, mainly to the use of an electrical preheater instead of an internal gas-gas heat exchanger and a recycle valve instead of a recycle compressor. However, an upcoming exergy economic analysis will show that the novel cycle is more economical overall, as its investment costs are lower.

Keywords: exergy analysis; power-to-ammonia; P2A; process design comparison; Aspen Plus® process simulation.

DOI: 10.1504/IJEX.2023.134607

International Journal of Exergy, 2023 Vol.42 No.2, pp.127 - 158

Received: 24 Mar 2023
Accepted: 27 Apr 2023
Published online: 30 Oct 2023 *

Title: Exergetic comparison of a novel to a conventional small-scale power-to-ammonia cycle

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