The hydrogen revolution is in-progress, momentum builds all the time, and yet the same fundamental ‘chicken and egg’ conundrum still makes appearance in debates on this hot topic.
Fuel cell vehicles (FCVs) manufacturers are reluctant to mass manufacture and market cars without adequate hydrogen fuelling locations, while station providers are reluctant to build stations without enough FCVs to use them.
The growing market for fuel cell cars needs a robust network of hydrogen fuelling stations, but capital costs for those stations remain high.
gasworld understands an emerging solution from researchers at the US Department of Energy’s (DOE) Argonne National Laboratory could significantly cut costs and boost refueling capacity – helping hydrogen compete with gasoline at the pump.
The concept, called two-tier pressure consolidation, is aimed at lowering one of the biggest capital costs in a hydrogen fueling station: the compressor. By reimagining both the way hydrogen is stored and the way the compressor operates, the pressure consolidation strategy could slash the equipment costs of a new hydrogen station by up to 30%, or allow an existing station to double its fuelling capacity without buying a new compressor.
Argonne researchers have been evaluating the processes and costs of hydrogen delivery and refueling for more than a decade, with support and guidance from the Fuel Cell Technology Office (FCTO) within DOE’s Energy Efficiency and Renewable Energy (EERE) office. The pressure consolidation idea took shape in 2012, after a laboratory analysis showed that the compressor and storage accounted for more than half a station’s costs.
“This really triggered our thinking and curiosity,” says Amgad Elgowainy, a team leader and principal energy systems analyst at Argonne who leads the research. “How could you reduce that compression cost?”
Taking a closer look, the Argonne team found station compressors tended to be oversized and under-used. The equipment works hard at peak times to keep pressure high and gas flowing when customers are at the pump, but sits idle otherwise. And as pressure lowers across emptying hydrogen supply tanks, so does the station’s capacity to efficiently dispense the hydrogen.
“Some of the vehicles in a typical station design today will fail to get a full fill because of this declining pressure in tanks supplying the compressor,” Elgowainy notes, “which is a nightmare from a consumer perspective.”
The pressure consolidation approach works by dividing the supply storage into two tiers. During off-peak periods, instead of sitting idle, the compressor transfers hydrogen from the vessels in tier 2 to the vessels in tier 1.
When the compressor then replenishes another set of high-pressure buffer storage tanks that serve the fuelling pumps, it draws from tier 1 pressure vessels. Because of the off-peak pressure consolidation that has taken place, tier 1 is at a high pressure and the compressor is able to achieve a higher throughput than otherwise possible.
“It is not an invention of new equipment,” Elgowainy says. “It is an invention of a refuelling method.” The method can work with any supply storage, either stationary ground storage or hydrogen delivered in a tube trailer.
Because the compressor only operates at high pressures with the consolidation algorithm, stations can use a smaller, less expensive one. Pressure consolidation also enables a station to use far more of its hydrogen supply at a time – more than 80%, versus only about 60% at a typical station. That allows for fewer hydrogen deliveries, saving further costs and reducing disruptions to fueling operation.
Finally, the new approach helps extend the life and reliability of the compressor by running it more consistently, rather than it regularly starting and stopping as demand fluctuates.
The concept eventually could have applications beyond hydrogen, Elgowainy says, and benefit other gaseous fuels, such as compressed natural gas fuelling.
Argonne researchers have tested and refined the two-tier pressure consolidation concept at the National Renewable Energy Laboratory over the past three years. Now, thanks to an award from the Department of Energy’s Technology Commercialization Fund, they plan a real-world demonstration.
PDC Machines, a compressor manufacturer based in Warminster, Pennsylvania, is partnering with Argonne for this phase.
“The use of pressure consolidation has the real possibility of reducing hydrogen stations’ costs,” says PDC Vice-President Kareem Afzal. It also reduces a station’s physical footprint, “both of which are precious commodities at potential hydrogen station sites,” he adds.