Thermodynamic modeling of hydrogen-water system for high-pressure storage and mobility applications

Hydrogen is considered as an alternative to fossil fuels that is practically unlimited, do not possess intermittency problems as wind/solar, and leads to zero carbon-emissions in its pure form and thus improving the air quality with respect to many other alternatives such as fossil fuels (i.e., natural gas streams). It is also an essential component in most CO2 to hydrocarbon conversion techniques. However, due to its low volumetric energy density at ambient conditions, hydrogen should be compressed for practical storage and transportation purposes. One way to achieve this is through electrochemical compressors that avoid acoustic pollution and increase efficiency as compared to mechanical compressors. However, since water (a medium) is required for the conductivity of protons, it saturates the hydrogen to an extent that may exceeds the safety restrictions employed for transportation fuels. This necessitates for an accurate thermodynamic/PVT model to design the compressor and proper water removal process and therefore, for safe storage and mobility of hydrogen at high pressures. In this work, a PVT model for hydrogen-water system is developed based on traditional Peng and Robinson (PR) equation of state (EOS) with non-classical Huron-Vidal (HV) mixing rule. It is shown that the model captures the molecular interactions and compares very well with the experimental data available in literature. Most importantly, a robust workflow is developed to obtain the HV parameters from solubility data of a binary system and verified with experimental observations. The workflow can be utilized for other binary (including aqueous and saline) systems having polar and other complex interactions even when sparse data is available.