Argonne tests, creates fuel cells to power the future
FUEL REFORMER – This Argonne-developed reformer releases hydrogen from commonly available fuels to power fuel cells in cars.
Fuel cells are a key component of the nation's plan for a secure energy future. Fuel cells convert hydrogen gas into electricity and water. Since hydrogen can be produced from a variety of domestic resources, researchers are seeking cost-efficient ways to use it to meet the nation's growing energy needs and reduce the nation's oil reliance.
Argonne has been a leader in fuel-cell research for decades and is playing a critical role in increasing the technology's contributions to the nation's energy security.
Researchers have developed an R&D-award winning catalyst to convert fossil fuels to hydrogen for the earliest fuel-cell vehicles, designed new materials for fuel-cell production, and created computer modeling systems that have been adopted as Department of Energy (DOE) benchmarks and are being used to identify future research and development needs.
Fuel cell facts
|While not a common household term, fuel cells are not new. Sir William Grove first described a fuel cell in 1839, but they did not emerge as a practical power source until the 1960s when the U.S. space program adopted the technology to power spacecraft. While still used in the space shuttles, more down-to-earth applications include stationary generators for remote facilities and for hospital backup power. In the future, they will power cars, cell phones, laptop computers and home electrical and heating systems. With the emerging distributed generation, fuel cells may also add power to the nation's electrical grid.
DYNAMIC TEST – Assistant U.S. Secretary of Energy David Garman (left) watches as Argonne's Advanced Powertrain Test Facility engineers track a car being tested on the dynamometer behind the glass.
|Many challenges must be met before fuel cells become mainstream, however; these include hydrogen production, storage, distribution and safety.
For example, researchers need to find new methods to produce hydrogen for fuel cells. Current hydrogen-production technologies used in petroleum refining and fertilizer manufacturing require burning fossil fuel. Laboratory researchers are developing new, clean hydrogen production techniques covered in other stories in this issue.
A primary, short-term focus is on creating fuel-cell-powered cars and light trucks. DOE and USCAR – an industry consortium comprised of DaimlerChrysler, Ford and General Motors – are partners in FreedomCAR, an initiative to develop technology to power fuel-cell vehicles.
Almost all of the cars and trucks in this country are gasoline- and diesel- powered. Because transportation uses two-thirds of the 20 million gallons of oil Americans use daily, government officials see fuel cells as the best method to dramatically reduce dependence on foreign oil.
Argonne is leading a team of researchers from industry and from Los Alamos, Oak Ridge and Pacific Northwest national laboratories to develop a fast-starting reformer for converting gasoline to hydrogen as part of FreedomCAR. These partners are developing an integrated fuel processor that can start up from ambient temperatures in 30 seconds or less to full power. Fuel processor fabrication is scheduled to be completed in winter 2004, with testing to begin shortly thereafter.
Fuel-cell vehicles powered by hydrogen are projected to be clean and efficient. Water is the only waste product of a hydrogen-powered fuel cell. Since transportation is a major contributor to greenhouse gas emissions, fuel-cell vehicles are predicted to cut emissions up to 500 million metric tons of carbon equivalent each year by 2040. A hydrogen fuel-cell vehicle can be up to two and one-half times more energy efficient than a conventional gasoline-fueled, internal-combustion engine car.
Advanced vehicle's energy use
A recent Argonne study was commissioned by General Motors to examine energy use for advanced vehicle technologies. The study included the total fuel cycle from "wells-to-wheels" – that is considering all of the energy used to get the fuel from the source to driving. The technologies investigated ranged from gasoline, diesel and alternative-fuel engines to hybrid-electric, battery- and fuel-cell powered engines. The study showed that a fuel-cell powered hybrid vehicle running on cellulose-derived ethanol would emit the least amount of greenhouse gases among 75 different car-powering technologies.
Argonne conducted the analysis in partnership with BP, ExxonMobil and Shell using Argonne's Greenhouse gases, Regulated Emissions and Energy Use in Transportation (GREET) software. GREET was originally developed with support from offices within DOE's Energy Efficiency and Renewable Energy secretariat.
Not all car-owners will be able to "fill-it-up" with hydrogen when the first fuel-cell cars come on the market in the 2010s, because there won't be a nationwide hydrogen-supply infrastructure in place yet. Also, hydrogen-storage devices are heavy and bulky. While researchers are working on this problem, Argonne scientists have developed an alternative.
TUFFCELL – Argonne has developed TuffCell, a solid-oxide fuel cell to be used as an auxiliary power unit. Chemical engineer Joong-Myeon Bae works with a TuffCell sample.
A team of Argonne scientists and engineers has developed and patented a transitional technology. Their compact fuel processor reforms gasoline from the pump or other conventional fuels such as diesel, methanol or natural gas, into a hydrogen-rich gas to power fuel cells.
The fuel reformer works somewhat like catalytic converters in cars. In the gasoline reformer, vaporized gasoline is mixed with steam and air before traveling through a cylinder packed with the new Argonne catalyst. The result is a hydrogen-rich gas that is further processed in subsequent chemical steps and is then fed to the fuel cell.
The catalyst that drives the gasoline-to-hydrogen reaction is critical. The development of this catalyst benefited from Argonne's earlier work in developing advanced solid-oxide fuel-cell materials. "If these types of materials worked in a fuel cell," principal investigator Romesh Kumar said, "then they should work as catalysts in the reformer."
Researchers used metal and oxygen compounds similar to those used in fuel-cell research as a support and coated it with platinum compounds. When the gasoline-air-water mix contacts the catalyst, it forms hydrogen, along with other gases.
Scientists are working to shrink the size and cost of the reformer, particularly by improving catalyst activities and reducing the amount of expensive materials in them, such as platinum. Argonne's reforming catalyst has been licensed to Sud-Chemie in Louisville, Ky., a major supplier of catalysts to the petrochemical industry.
The Argonne reformer is energy efficient, capable of rapid start-up and shut-down, and is dynamically responsive to load changes. It is compact and operates at lower temperatures than other fuel processors being developed for reforming gasoline. Power demands can be handled by adjusting the feed rates to the reformer, much like today's fuel-injected internal combustion engines. DOE's Office of Hydrogen, Fuel Cells, and Infrastructure Technologies funds this research.
Another critical fuel-cell research area is materials - the devices have to be durable and inexpensive for general use. As one example, materials scientists have designed new metal supports for solid-oxide fuel cells that are stronger, deliver better performance, are easier to make and cost less than current designs.
POWER TEST – Chemist Laura Miller (foreground) prepares a TuffCell sample for testing its power output at various loads, which is a critical measure of a fuel cell's usefulness.
Used in Argonne's TuffCell, a new solid-oxide fuel-cell design, the stronger, metallic bi-polar plates replace the traditional, costly and fragile ceramic-cell supports. The metal supports are easier to make. In conventional processing, the ceramic supports are successively sintered - processed at high temperatures - as each of the four layers is added. In the TuffCell, only one high temperature step is used in the cell fabrication.
TuffCell could be used in auxiliary-power units for tractor-trailers. These trucks run their engines overnight to keep refrigeration units cool, or to provide electricity to the cab for lighting and appliances. Some states are banning truck idling, because of the vehicle emissions.
While this application seems small, use of TuffCell or other fuel cell-powered auxiliary-power units could prevent annual emissions of 22 tons of the greenhouse gas carbon dioxide, 1,024 pounds of nitrogen oxides and 390 pounds of carbon monoxide per truck per year; based on an Argonne study, these estimates assume that an average truck idles for 1,830 hours a year. There are about 500,000 such trucks now operating in the country.
Modeling fuel-cell powered cars
|Although fuel-cell vehicles are mechanically simpler than cars with conventional internal combustion engines and transmissions, many of their interactive systems still need to work together efficiently. To aid in this effort, Argonne researchers have developed several software tools based on the laboratory's years of experience in fuel-cell and transportation research. These tools are being used in industry, universities and other national laboratories as well.
The laboratory's General Computational toolkit (GCtool) is used for designing, analyzing and comparing different fuel-cell power-plant configurations. GCtool lets engineers try out different system configurations without the expense and delays of actually building prototypes. GCtool was adapted from earlier software that the laboratory created to model nuclear, space and shipboard service power.
Working with staff from the Nuclear Engineering Division, Chemical Engineering Division (CMT) researchers use GCtool to design fuel-cell systems. Their research has shown that more can be less.
"We found," said CMT Associate Director Jim Miller, "that focusing only on increasing the efficiency of the fuel processor - the component that converts hydrocarbon fuel into hydrogen for the fuel cell - may actually lower the overall system efficiency."
Kumar explained that just increasing the fuel-processor efficiency can steal energy from elsewhere in the system. Rather, the complete fuel-cell system must be considered in its entirety to ensure that the most efficient system is implemented.
The software also showed that the compressor/expander and heat and water recovery subsystems that manage water and operating pressure in fuel-cell systems play a more critical role in system efficiency than had been expected.
The whole car
Fuel-cell car designers need to simulate beyond the fuel-cell system to study energy storage requirements and other questions that must be addressed before large-scale commercialization. Engineers in Argonne's Center for Transportation Research have developed software that can be used to simulate and analyze almost all imaginable powertrains. Called Powertrain Systems Analysis Toolkit (PSAT), it was created in conjunction with Ford, General Motors and DaimlerChrysler.
The software analyzes fuel economy, emissions and performance for any driving cycle or profile for a broad range of vehicles from conventional to fuel-cell drivetrains and up to four-wheel-drive configurations.
FUEL PROCESSOR – Argonne's fuel processor turns petroleum-based fuels, such as gasoline, into hydrogen plus carbon monoxide and carbon dioxide.
GCtool and PSAT were modified to work together when DOE requested Argonne researchers to establish energy storage requirements for three vehicles using a projected fuel-cell technology.
GCtool is the benchmark system for evaluating fuel-cell system designs for DOE's Office of Hydrogen, Fuel Cells, and Infrastructure Technologies. The fuel cell modules in Argonne's PSAT software, and also in the National Renewable Energy Laboratory's Advanced Vehicle SimulatOR (ADVISOR) program, were derived from Argonne's GCtool simulations. GCtool has been licensed to more than a dozen organizations; its continued development is supported by DOE's Office of Energy Efficiency and Renewable Energy.
Fuel cell test facility
As fuel-cell technologies emerge, the laboratory's Fuel Cell Test Facility provides independent, standardized testing and evaluation. Argonne's facility is the only such facility in the national laboratory system, and it is one of the few in the nation that can test full, automotive-sized systems.
|From specific subsystems to fully integrated systems with their own fuel processing and air supply, a fuel cell's performance, operation and durability can be compared with competing technologies.
The test facility controls the temperature, pressure, humidity and flow rate of both fuel and air supplies. The fuel can be either pure hydrogen or a simulated reformate. Lab equipment can also monitor and evaluate the fuel cell's water management system. The facility will be updated to evaluate integrated fuel-cell systems including fuel reformers and energy storage devices.
Planning for the hydrogen-for-vehicles infrastructure is underway. Argonne's on-board reforming may be a transitional step, but is not considered the final solution. Hydrogen can be produced from a variety of sources including fossil fuels like coal or natural gas, biomass and water using either electricity (electrolysis) or high temperatures.
Because it has a relatively low energy density, hydrogen must be compressed, liquefied or adsorbed onto a highly reactive material before it can be distributed as a vehicular fuel. Each of these production sources and delivery forms has advantages and disadvantages.
Transportation analysts such as Argonne's Marianne Mintz are evaluating alternative combinations of production and delivery systems to determine the best ones in terms of cost, safety and energy efficiency. With so many variables and unknowns, Mintz plans to work with agent-based modelers in Argonne's Decision and Information Sciences Division. Leaders in the emerging field of complex adaptive systems, researchers there will be examining the behaviors and interactions of various agents that could be involved in producing and delivering hydrogen within a larger system. And with its many variables, the future of the hydrogen infrastructure is a complex system.
"Once the hard work of defining agents and modeling their decision processes is complete, agent-based modeling allows researchers to see the whole system with interdependencies previously unimaginable," said Mintz.
Argonne's fuel-cell research is making important contributions to the Freedom-CAR Partnership and the nation's energy security. FreedomCAR's goal is to develop practical and cost effective fuel-cell vehicle, fuel and infrastructure technologies. The plan is for fuel-cell vehicles to be cost-effective alternatives to gasoline-powered vehicles by 2015 and the choice of many consumers by 2020.