Effects of cooling-recovery venting on the performance of cryo-compressed hydrogen storage for automotive applications

Cryo-compressed vessels have many advantages in storing hydrogen for automotive applications such as the large storing density and thermal endurance. However, the cooling power of venting hydrogen in the processes of venting and discharge is wasted. In this paper, a cooling-recovery venting method with a throttling valve is proposed for the cryo-compressed hydrogen storage. A thermodynamic model is established to analyze the behavior of hydrogen in the insulated pressure vessel with a throttling valve. Different initial pressures, release pressures and filling amounts of hydrogen in the vessel are studied in the processes of parking, discharge and driving. The parking time can be extended by 55% with a throttling valve in the vessels of 2 MPa release pressure. The parking time increase by recovering the cooling capacity is large for vessels of large filling density which also have longer parking time. Simulations of hydrogen storage during the actual driving are performed at different initial pressures. The throttling valve in the low-initial-pressure vessel can reduce the upper pressure limit of the vessel by 50% which helps to reduce the manufacturing costs. Considerable thermodynamic benefits can be utilized with the cooling-recovery venting during the driving process. This work provides guidelines for the design and optimization of cryo-compressed hydrogen storage system.