ARGONNE PATENTED PRESSURE CONSOLIDATION REFUELING ALGORITHM

Deploying 700 bar hydrogen stations capable of multiple back-to-back T40 vehicle refueling involves high capital investment. The compression component alone comprises about half of the refueling station installed capital cost across various refueling station capacities (compressors for large stations ,e.g., ~500 kg/day cost ~ $1M). Argonne National Laboratory (ANL) has developed a novel hydrogen refueling station pressure consolidation method that increases the station refueling capacity by a factor of 2-3X, significantly improves the supply storage utilization, with a major reduction in refueling cost. The pressure consolidation method is ideal for expanding the refueling capacity of existing refueling stations, providing incremental, low-risk approach to capital investment as fuel cell vehicles are deployed in early markets. The proposed concept is projected to reduce the compression contribution to hydrogen cost (in terms of $/kgH2) by more than 50%.

Compressor operation principle
Schematic of compressor working principle

The pressure consolidation concept hinges on the principle that a compressor’s throughput is directly proportional to its suction pressure. This principle holds true for all volume displacement compressors (e.g., piston, diaphragm, rotary, etc.). Consolidating hydrogen between the supply storage pressure vessels (during low refueling demand periods) maintains higher pressure in selected vessels that feed the compressor (i.e., increases the compressor’s throughput) during high refueling demand periods. This increases the station’s capacity to sustain high hydrogen fueling rate at the dispensers during the peak demand periods. The pressure consolidation method also minimizes the idle time and reduces the on/off cycling of the compressor, and thus improves its utilization and reliability, and reduces its contribution to refueling cost. With pressure consolidation, a compressor that is typically used for a station capacity of 200 kg/day can be used to satisfy a station capacity of 800 kg/day by sustaining compressor suction pressure above 155 bar.

Compressor flow curve
PDC compressor flow curve showing required compressor throughput for different station refueling capacities

The table below shows an example of station performance indicated by its refueling capacity (or number of vehicle fillings) and supply storage (or tube-trailer payload) utilization with and without the pressure consolidation operation strategy. Implementing the consolidation strategy with PDC-13-7500/15000 compressor, rated at 8 kg/hr at 20 bar suction, can serve a station with daily demand of 500 kg/day and provides 79% utilization of a 600 kg supply storage (@ 250 bar). The same compressor only satisfies a station daily demand of 200 kg/day without pressure consolidation strategy for the same supply storage utilization.

Pressure Consolidation Result

The video below shows the status of the supply storage (with pressure consolidation) as vehicles are filled following a typical hourly demand profile.


Relevant Publications

  1. Reddi, K., Elgowainy, A., Rustagi, N., & Gupta, E., (2018) “Two-tier pressure consolidation operation method for hydrogen refueling station cost reduction”, International Journal of Hydrogen Energy (in press), https://doi.org/10.1016/j.ijhydene.2017.12.125.
  2. Elgowainy, A., and Reddi, K., (2017, August) “Enhanced methods for operating refueling station tube-trailers to reduce refueling cost.”, U.S. Patent No. 9,739,418.
  3. Elgowainy, A., Reddi, K., Sutherland, E., & Joseck, F. (2014). Tube-trailer consolidation strategy for reducing hydrogen refueling station costs. International Journal of Hydrogen Energy, 39(35), 20197-20206.