Friday, April 2, 2010
What scientists call the "First Law" tells us that energy in our daily lives is neither created nor destroyed -- only transformed. It's the chemical energy bound up in natural gas and oxygen that makes heat in your furnace, or electrical energy in my toaster that burns my bagels each morning.
But although energy is never destroyed, it certainly can be "wasted" or put to purposes we people just don't appreciate. My favorite example of that is an overheating pickup engine's radiator, boiling over vigorously on a mountain grade in the summer time.
My four cylinder "little rig," as we say in the rural West, gets about 31 miles per gallon on the highway. I like them apples! But wouldn't it be grand if that figure could be doubled? We would not be defeating the First Law, just using energy transformations more efficiently. And I'm glad to say I've seen a prototype of a device I think could do that -- and economically, too. The little engine that could is called a fuel cell. There are several types of them; I'll just concentrate on two, first the one that's simpler but expensive, then the more complex but practical one that may revolutionize our world.
I've taught freshmen college students about the first one. It runs like a battery, you could say, but one that never needs charging because it uses fuel. Fuel cells have advantages over batteries. Batteries are very heavy (come to my house and carry in the boat battery in the fall or back out in the spring if you doubt this statement). And batteries, for what they weigh, don't put out much oomph.
The simple kind of fuel cell draws in pure hydrogen gas to an anode (negative) plate, with oxygen fed at the same time along the cathode (positive) plate of the device. There has to be a membrane and a chemical "soup" in the middle of the cell, but what matters for our purposes is that if you connect the negative to the positive parts you get an electrical current. You can run a light bulb, power a fan, or do any other form of work you care to with the resulting electricity. And the great thing about the fuel cell just described is that its only waste product is pure water.
But fuel cells like this are expensive. The catalyst inside them is made of platinum. And the hydrogen gas fuel is pretty scary stuff -- hydrogen burns explosively with even the smallest spark. That's one reason why, although engineers have long been able to make desktop fuel cells for special applications (or showing students the principles of how they work), your car isn't running on one today.
But what if there were a second-generation fuel cell that ran not on hydrogen, but on mundane fuel like gasoline, diesel -- or even coal or processed plant matter? All those materials could supply hydrogen to the fuel cell, even though not in pure form. And if they were consumed in the controlled manner fuel cells use to oxidize fuel, they would produce electricity, again like a battery.
Here at Washington State University Dr. Jeongmin Ahn and his students are developing these "solid oxide fuel cells." One of the great things about this next generation fuel cell is that is doesn't require platinum as a catalyst, using much cheaper nickel instead. Another feature of the fuel cells that knocks my socks off is that one model can run on waste heat. That's important, and here's why.
A standard car is about 25 percent efficient, meaning it uses 25 percent of the gas you put into it to get you from Point A to Point B, but it wastes 75 percent of the gas as heat! If a good measure of that waste can be fed into a fuel cell, it can help to power the car using an electrical motor -- a new sort of hybrid vehicle.
"We can double the miles per gallon of cars using that technology," Ahn said to me. "Easily."
I surely like the sound of that.
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