Transporting hydrogen from its production site to a refueling station and ultimately into the tank of a consumer’s fuel cell electric vehicle (FCEV) is something of a chess game. FCEV chess masters must consider the various costs of an array of technologies and delivery systems that are available to serve growing market demands.
Hydrogen suppliers now can license a patented refueling method developed at the U.S. Department of Energy’s (DOE) Argonne National Laboratory as part of a calculated strategy to cost-effectively move hydrogen across the chessboard. Argonne used thermodynamic and flow dynamics computational tools to conduct early stage research simulating the performance of hydrogen fueling station components, which ultimately led to developing this strategy.
Last September, Argonne’s Amgad Elgowainy and Krishna Reddi received $749,000 from the DOE’s Office of Technology Transitions Commercialization Fund to help gain the technology early entry into the FCEV marketplace. Their partners in the project are FirstElement Fuel and PDC Machines, Inc.
“We wanted to minimize the cost of refueling station components while allowing drivers to refuel quickly.” — Amgad Elgowainy, team leader and energy systems analyst at Argonne.
“One of the strategy’s largest advantages is that it can significantly reduce the size of the compressor while meeting the increasing demand at the stations, and that’s a significant cost reduction,” said Erika Gupta, operations supervisor at DOE’s Fuel Cell Technologies Office (FCTO) within the Office of Energy Efficiency and Renewable Energy, which funded the research. “Anything we can do to lower the initial capital cost of building the station helps us accelerate station deployment.”
Hydrogen is one of the most abundant elements on Earth, yet only 6,000 motor vehicles worldwide harness this readily available molecule as a clean fuel source. All of the 31 retail refueling stations that dispense hydrogen in the United States are currently in California. An additional 12 are being deployed in the Northeast to support expected demand for FCEVs. Two of them have been commissioned to date in Connecticut and Rhode Island, where more are planned or are already under construction. As of December 2017, more than 3,500 FCEVs had been sold in California. The California Air Resources Board projects the number will increase to 13,400 by 2020, and to 37,400 by 2023.
“They are ramping up fast,” said Amgad Elgowainy, team leader and principal energy systems analyst at Argonne. Nevertheless, the lack of refueling stations remains a barrier to wider use of these vehicles.
Compressors account for approximately half the total equipment cost of a hydrogen refueling station. But Elgowainy and Reddi, an Argonne systems modeling and analysis engineer, have shown how to double or triple refueling capacity by using existing equipment more efficiently.
Elgowainy and Reddi described their pressure consolidation refueling method, the only one of its type in the world, in the Dec. 3, 2014 issue of the International Journal of Hydrogen Energy, and in several presentations thereafter.
Argonne’s method can especially benefit hydrogen refueling stations supplied by gaseous tube trailers, said Neha Rustagi, FCTO technology manager. “In any early and emerging market, we would expect gaseous tube trailers to have a large role because they’re often the lowest-cost approach to getting hydrogen to smaller stations,” Rustagi said.
Fast fueling (about 3 minutes) of standard onboard vehicle storage tanks is expensive. Refueling station owners must invest a great deal in compression, refrigeration and high-pressure storage equipment.
“We wanted to minimize the cost of refueling station components while allowing drivers to refuel quickly,” Elgowainy said.
During the consolidation process, hydrogen moves from one tube-trailer vessel into another, typically during low-demand periods, to prepare for the next peak-demand period. Compressor costs range from approximately $300,000 to $750,000 each, depending on their capacity. With Argonne’s pressure consolidation refueling method, stations can double or triple their capacity with the less-expensive compressors. This means that the capital cost of a refueling station with the capacity to dispense 450 kilograms (992 pounds) of hydrogen daily drops from $1.1 million to $650,000.
The researchers based their technology on a comprehensive hydrogen-station, cost-optimization performance model that simulates how hydrogen refueling stations operate. The model tracks and calculates the fuel mass and its temperature and pressure at any point in the refueling process.
The model simulated the refueling station with an hourly fueling-demand profile based on data from more than 400 Chevron gasoline refueling stations. The results show that, for any given tube-trailer compression strategy, consolidation can reduce the total investment cost for refueling stations by 40 percent. The model was robust enough to replicate data generated and measured in ongoing experiments at the DOE’s National Renewable Energy Laboratory in Golden, Colorado, Elgowainy said.