Single-tank storage versus multi-tank cascade system in hydrogen refueling stations for fuel cell buses

Many countries in Europe are investing in fuel cell bus technology with the expected mobilization of more than 1200 buses across Europe in the following years. The scaling-up will make indispensable a more effective design and management of hydrogen refueling stations to improve the refueling phase in terms of refueling time and dispensed quantity while containing the investment and operation costs. In the present study, a previously developed dynamic lumped model of a hydrogen refueling process, developed in MATLAB, is used to analyze tank-to-tank fuel cell buses (30–40 kgH2 at 350 bar) refueling operations comparing a single-tank storage with a multi-tank cascade system. The new-built Aalborg (DK) hydrogen refueling station serves as a case study for the cascade design. In general, a cascading refueling approach from multiple storage tanks at different pressure levels provides the opportunity for a more optimized management of the station storage, reducing the pressure differential between the refueling and refueled tanks throughout the whole refueling process, thus reducing compression energy. This study demonstrates the validity of these aspects for heavy-duty applications through the technical evaluation of the refueling time, gas heating, compression energy consumption and hydrogen utilization, filling the literature gap on cascade versus single tank refueling comparison. Furthermore, a simplified calculation of the capital and operating expenditures is conducted, denoting the cost-effectiveness of the cascade configuration under study. Finally, the effect of different pressure switching points between the storage tanks is investigated, showing that a lower medium pressure usage reduces the compression energy consumption and increases the station flexibility.