TransForum Vol. 3, No. 1

MODEL HELPS FOCUS FUEL CELL VEHICLE RESEARCH

It's midnight in Michigan, and somewhere outside Detroit an automotive engineer is staring at the ceiling, wondering how she's going to squeeze 1% more efficiency out of the fuel cell reformer she's been working on. Never mind 5% more from the next component on her list.

When it comes to designing fuel cell and other next-generation vehicles, the pressure is on. With the volatility of gas prices and ever more stringent emissions regulations, the automotive industry is being squeezed as never before to design and bring to market highly efficient, environmentally friendly, affordable cars and trucks. Playing an essential role in this effort is computer software that lets designers "try out" different system configurations, without the expense and delays of actually building numerous prototypes.

An example of this software is the General Computational toolkit (GCtool), a versatile simulation software package that was developed by Argonne for designing, analyzing, and comparing different power-plant configurations. This flexible software uses a modular approach to integrate many of the detailed thermodynamic and component models developed during decades of fuel cell and power system research at Argonne and elsewhere.

GCtool is easy to use. "An entire fuel cell system - everything necessary to go from fuel to electricity - is specified as a sequence of lines of simple code," says Romesh Kumar, who leads Argonne's fuel cell modeling efforts. From this input, the software generates a system schematic, and users can switch between the input window and the diagram until they are satisfied with the flows. According to Kumar, "You enter lines in the input window and then you look at the diagram and say, 'Oh, wait a minute - this isn't going where I wanted,' and you go back and change it." All the input, including lines specifying the fuel, feed rates, and component performance, can fit on one page for a relatively simple system. The user can modify all the system inputs - down to the density and thickness of a heat exchanger wall.

Sensitivity analyses, one of the things the software is often used for, can save automotive engineers a tremendous amount of time. Kumar explains: "We might see that a small difference in the fuel cell performance yields a big difference in the vehicle efficiency, which means the whole system is very sensitive to that. Whereas if we change the airflow by a factor of two, the efficiency may not change much - then we can say the system isn't much affected by airflow, and we can focus our efforts elsewhere."

By questioning all of their assumptions, Argonne's systems analysis team found a surprise hiding in the compressor/expander systems used to manage water and operating pressure in fuel cell systems - namely, that the efficiency of these systems is much more important to overall efficiency than expected.

The research for GCtool is supported by funding from the U.S. Department of Energy's Office of Transportation Technologies. As automotive fuel cell technology gets closer and closer to what promises to be a huge market, companies are naturally reluctant to reveal their research. The kind of analysis done at Argonne, because it can be made public, provides an important forum for discussion that can keep developers from working in isolation and spending energy, time, and money that could be devoted to more critical problems.

A variety of arrangements is available for licensing the technology. At present, about a dozen organizations outside of Argonne are using GCtool for systems analysis and evaluation. Some of these users are private-sector fuel cell companies and universities that assist DOE in the development of new fuel processing and fuel cell system technologies for automotive applications.