A road to inexpensive fuel-cell cars
Dr. Michael Gerhardt
I want you to think about how you got here today. Perhaps some of you are like me and drove, or maybe you took the bus. Unfortunately, many of these vehicles are powered by burning gasoline in an engine. This process produces carbon dioxide, a greenhouse gas that contributes to global warming and climate change. In fact, about a pound of carbon dioxide is emitted for each mile we drive. Imagine dumping a five pound bag of flour out the window every few minutes, but it also melts the ice caps.
But it doesn't have to be this way. We have the technology today to make cars that run on hydrogen gas. Using a device called a fuel cell we can extract electrical energy from a chemical reaction between hydrogen fuel and oxygen, with water (H2O) as the only byproduct.
And we can do this for the low, low price of $58,000 — that's the suggested retail price of Toyota's fuel cell car, the Mirai. That’s more expensive than a Tesla! Granted, there are some advantages: fuel cell cars can fuel up in five minutes, while a battery can take hours to fully charge. And the 300-mile range is better than all but the longest-range Teslas. But 58 grand is still too high a price for most people.
One of the reasons these cars cost so much is that we have to oversize the fuel cells and use expensive components to get enough power to push the car forward. Here at Berkeley Lab, I use computer simulations to understand what limits the performance of these cells and how to optimize them. Water, the product of the hydrogen reaction, plays a particularly important role.
Every fuel cell has a special plastic sheet, called a membrane, that helps keep the hydrogen and oxygen separated and controls the rate of the hydrogen reaction. But this membrane can only do its job when it's wet — if the membrane dries out, the cell dies of thirst. But we can't let too much water accumulate either, or it'll block the hydrogen and oxygen from entering the fuel cell, and the cell drowns.
My simulations predict how much water is formed, how much is too much, and how little is too little. This work allows us to optimize water management strategies to improve cell performance, which allows us to cut down on cost by using fewer cells to achieve the same power output. We can also understand how new membrane materials soak up and release water.
If we are successful, we’ll be able to use fewer cells with inexpensive materials to get the same horsepower. That would make fuel cell cars more affordable. And if we can put more of these cars on the road, we can stop dumping pounds of carbon dioxide into the atmosphere when we drive, and slow the harmful effects of global warming.