Increasing Compressed Gas Energy Storage Density Using CO₂–N₂ Gas Mixture

• Main Authors: Ahmad Abuheiba, Moonis R. Ally, Brennan Smith, Ayyoub Momen
• Format: Article
• Language: English
• Published: MDPI AG 2020-05-01
• Series: Energies
• Subjects: GLIDES; pumped storage; compressed air storage; vapor liquid equilibrium; binary mixture
• Online Access: https://www.mdpi.com/1996-1073/13/10/2431
• ISSN: 1996-1073

This paper demonstrates a new method by which the energy storage density of compressed air systems is increased by 56.8% by changing the composition of the compressed gas to include a condensable component. A higher storage density of 7.33 MJ/m³ is possible using a mixture of 88% CO₂ and 12% N₂ compared to 4.67 MJ/m³ using pure N₂. This ratio of gases representing an optimum mixture was determined through computer simulations that considered a variety of different proportions from pure CO₂ to pure N₂. The computer simulations are based on a thermodynamic equilibrium model that predicts the mixture composition as a function of volume and pressure under progressive compression to ultimately identify the optimal mixture composition (88% CO₂ + 12% N₂). The model and simulations predict that the optimal gas mixture attains a higher energy storage density than using either of the pure gases.