On November 5, a shoebox-sized vehicle with the intriguing name of “Green Rock Eating Monster” will try to take Salt Lake City by storm with a hail of hydrogen electrons. The little vehicle, which runs on clean green hydrogen, is the University of Massachusetts Amherst entry in the national Chem-E-Car Competition, sponsored by the American Institute of Chemical Engineers (AIChE) at its Annual Student Conference in Salt Lake City.
As part of the simple, elegant design of the Green Monster, one chemical reaction both starts and stops the car. “The way this car works is that it has a fuel cell that’s fed hydrogen,” explains UMass team leader John Vergara, “and then the fuel cell takes the electrons from the hydrogen and puts them in a circuit, and those electrons run an electric motor on the car.”
In essence, when the vehicle runs out of hydrogen, it just stops.
The Green Monster is essentially the same vehicle that finished 10th out of 34 entries in last November’s national Chem-E-Car competition, except that the UMass team of 12 chemical engineering students has made it more lean, more mean, and more green.
“I think we have a better chance of winning this year than we did last year just because the machine is simpler and there aren’t as many variables,” says Vergara. “I’m pretty confident.”
The Chem-E-Car Competition requires each team to build a self-propelled model car that, driven only by a chemical reaction, travels a pre-set distance while carrying a pre-determined volume of water. The catch is that competitors learn only minutes before the competition the exact distance their car must travel and the volume of water it must carry. All the teams get two runs apiece so that, ideally, they can learn from their mistakes during the initial run and make adjustments in the next.
The key parts on the Green Monster are a little hydrogen tank, about five inches long and an inch in diameter, which uses aluminum hydride powder to absorb hydrogen, a fuel cell, an electric motor, and a potentiometer that controls the power to the motor and keeps it constant. The UMass team built the vehicle by taking an RC Hobbies remote control model and customizing it in the Chemical Engineering Department shop to use environmentally friendly hydrogen as fuel.
One engineering innovation made by the UMass team has to do with gear ratio. “We use a very low gear ratio,” says Vergara, “so that when the load, or volume of water, is added during the competition, it won’t affect how far the car goes. That makes the amount of water irrelevant. All we have to account for during the competition is how far the car goes.”
The way the car is designed is that the distance it travels depends on the amount of hydrogen inside the hydrogen tank, and the amount of hydrogen depends on how much pressure is in the tank. That pressure is controlled by charging the hydrogen tank to a certain PSI, or pound-force per square inch. Accordingly, the team has run hundreds of test drives with the Green Monster to determine how far each PSI reading will propel the vehicle.
“If the competition judges want our car to go 50 feet, we know that’s about 95 PSI,” says Vergara. “So all we need to do is charge the hydrogen tank with that pressure and we know how far our car should go.”
How accurate is this system? “I believe that, by the competition,” says Vergara, “we will be able to charge the hydrogen tank to a certain PSI and get the predicted distance within plus or minus six inches.”
The UMass team competing in Salt Lake City will include Vergara, Adam Ramey, Stephanie Polgar, Yung Chan, Gayla Berg, and Oksana Kopina.
The official rules of the Chem-E-Car competition state that “Team members design and construct a chemically powered vehicle within certain size constraints. This vehicle must be designed to also carry a specified cargo. The teams will be told at the time of the competition the distance that the car must travel and the specified cargo that the vehicle will carry. The winner will be determined by a combined score, for traveling the correct distance, and for creativity. Teams compete at the regional conferences, and the winner of each regional conference will compete at the national conference.”
The national first-, second-, and third-place prizes will be awarded for $2,000, $1,000, and $500 respectively. The 2010 Annual Student Conference, held from November 5 to 8 at the Salt Palace Convention Center, is billed by AIChE as “four days of career information, social events, competitions, and fun.” (November 2010)