Professor Jeffrey Allen of Michigan Technological University is nearing development of a mathematical model of the interior functions of a reliable hydrogen fuel cell. The new model should slash the research and development time and effort. The model keys on the fuel cells main problem, handling the water produced while in operation.
What sends the environmental crowd into joy is that a hydrogen fuel cell’s emission is water vapor. A fuel cell power plant only emitting water would be the nirvana of portable and mobile power. There is a huge “but” in the way.
A tiny amount of water will kill the reaction that drives a hydrogen fuel cell. Moving the water out is a difficult and as yet unresolved, engineering issue. Until it’s mastered reliably and at low cost, hydrogen fuel cells will remain a dead end. Even more concerning is fuel cells are actually stacked up cells to get to voltage, and just one cell in a water error kills the whole stack. Two decades of worrying away at ideas has brought no solution that can be mass-produced.
The water forms up in the fuel cell’s porous transport layer (PTL), which is not much thicker than a coffee filter. That’s where all the byproducts of the fuel cell’s power-generating reaction meet up with a catalyst and react to form the water vapor.
Allen, the John F. and Joan M. Calder Associate Professor in Mechanical Engineering at Michigan Tech points out it’s not easy to find out exactly what’s happening in the PTL. “Everything is compressed like crazy. You have to get the gases, hydrogen and air – to the catalyst, and you have to get the water away. Figuring out how to do this has largely been a matter of trial and error.”
Hope lies in the latest generation of hydrogen fuel-cell technologies that do an excellent job of managing water, but as new materials and designs enter the arena, the industry is again faced with a long, costly experimental process to determine the best configuration.
This is where Allen and his team with a new model come in. “There’s a whole new class of catalysts coming out, and we want to make sure it doesn’t take another 20 years to optimize the materials set,” says Allen.
Optimizing those up-and-coming materials to get rid of water is especially difficult, because the movement of water in the PTL appears to be random. “But that’s what we’re trying to predict,” he says.
The Michigan Tech press release writer puts it this way: at high flow rates, water spreads out evenly. But when the flow rate is low, as it is in an operating fuel cell, it spreads out in irregular shapes like an amoeba, a process called “fingering.” Other factors come into play as well, including how saturated the PTL is.
Allen’s team incorporated those variables into a mathematical model with the aim of forecasting the movement of water. Then they tested it using four different types of PTL and found that they could predict how water would behave with a high degree of accuracy.
“We were really excited,” Allen says. “This is the first time anyone has validated a model in a real sample. We’re at the point where, by adjusting just one parameter, we are able to duplicate experimental results exactly.”
The team is taking the model further by incorporating temperature and evaporation into their model to make it an even better tool for fuel cell designers.
The publication of the findings took place back in December of 2011 with the press release just getting out last week. The article, “Scaling Percolation in Thin Porous Layers,” published in the journal Physics of Fluids.
A polite reminder – hydrogen is a fuel not an energy source. While one hopes the good professor and his team can drive to an economical and reliable fuel cell, the cost of the hydrogen is going to make or break the hydrogen economy.
So far the main sources of hydrogen are from natural gas with CO2 remaining, electrolysis of water which needs a electricity source that so far suggests 150% of the hydrogen energy store is needed to get to the 100% energy store in the hydrogen.
Plus hydrogen remains the devil to contain. Hydrogen is the smallest atom and slips away almost at will. No really convincing storage schemes seem practical yet. And when it does escape, as it is highly reactive, the potential for accidents with serious personal injury and property damage is very high.
Still, Allen is leading to a good end. Should the hydrogen formation and energy carrier of choice get sensible as suggested by using methanol or ammonia, then fuel cells could drive demand to mass production.
We wish Allen great success and hope the example he’s setting will transfer to the other side of the fuel cell where much safer, simpler and lower cost fuel stores such as methanol can become fuel cell fuels. Then we should have some numbers on the cost to get hydrogen-energized work done.