Performance evaluation of hybrid compressors for hydrogen storage and refuelling stations

Abstract

Hydrogen Refuelling stations demand hydrogen at a very high pressure of 700 bar. Presently, most of these stations rely on conventional mechanical compressors for hydrogen compression. However, conventional compressors necessitate frequent maintenance, consume significant electrical power, and entail higher costs and safety risks. Conversely, MH (metal hydride) compressors offer a solution to these drawbacks and present additional advantages, including their capability to operate using low-grade thermal energy. This underscores the potential for integrating energy storage solutions into hydrogen infrastructure, enhancing efficiency and sustainability. The present work investigates the prospects of minimizing the high compression costs of hydrogen (around 48 % of the total capital cost of the refuelling station) by using a hybrid compressor based on metal hydride technology. The hybrid compressor is designed in such a way that the initial compression stage up to 500 bar is facilitated by an MH compressor, followed by the second stage, which will elevate the pressure up to 1000 bar. Moreover, a comparative energy assessment of the hybrid and conventional compressors is carried out. The results show that the hybrid compressor significantly decreases electrical demand from 3.83 kWh/kg to 0.93 kWh/kg (75.7 % reduction) by incorporating the MH compressor. Therefore, this innovation leads to a substantial reduction in high-grade energy consumption. However, the system's reliance on low grade thermal energy input increases (∼27.2–30.05 kWh/kg). This low grade thermal energy can be supplied through solar thermal collectors or by utilizing the waste heat from any process, making the hybrid compression approach a promising solution for efficient compression systems in both hydrogen storage and refuelling applications.