Enhanced hydrogen storage of a LaNi5 based reactor by using phase change materials

Abstract

Safe and efficient hydrogen storage technology is of great significance for large-scale hydrogen energy utilization. Using metal hydride (MH) materials such as LaNi5 for hydrogen storage is an effective way. In application, the heat and mass transfer characteristics in the reactor are one of the important factors and key problems affecting the hydrogen storage performance of MH. This paper proposes a novel hydrogen storage reactor installing a concentric finned tube heat exchanger and using phase change materials (PCM) by surrounding the reactor to improve heat transfer and hydrogen storage performance. A numerical model is built to describe transportation and reaction of two reactors with or without PCM. By comparison, the reactor surrounded by PCM has faster heat discharge and hydrogen absorption rate, and the absorption time is shortened by 50%. For the reactor with PCM, the optimal amount of PCM and the inlet velocity of heat transfer fluid (HTF) are investigated. The results show that the effective thermal conductivity of MH play a key role to improve heat transfer and reaction rate rather than that of PCM. Furthermore, increasing hydrogen supply pressure can effectively accelerate heat discharge and hydrogen absorption rate owning to larger temperature differences and improved reaction kinetics.