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Harvesting the Energy Beneath Our Tires


Hanh-Phuc Le, Tuan Hoang and Long Tran of the PT-EGen team

Berkeley engineering grad students Hahn-Phuc Le, Tuan L. Hoang, and Long Tran were stuck in traffic one day near Berkeley. As cars crawled along the street, the engineers wondered, could they somehow harness energy from those heavy vehicles as they moved along the road? Their answer—yes—eventually led them to their big idea and a prize in UC Berkeley's Big Ideas Competition.

Held yearly, the Big Ideas Competition supports and awards students who develop innovative concepts that help advance the world's most pressing social issues. The contest categories include Clean & Sustainable Energy Alternatives, Financial Literacy, Global Poverty Alleviation, Maternal & Child Health and others.

Le, Hoang and Tran won one of two first prizes awarded in the Clean & Sustainable Energy Alternatives category for their proposal, "PT-E Generator: Harnessing the Energy of Moving Cars" (PT-EGen) and received a $5000 award. "We'll use the money to build our first prototype this summer," said Le. The team has picked out two potential testing sites—one in Berkeley and one in Albany.

PT-EGen will harness energy via a slightly inclined contact pad on the surface of the road. As cars drive over the pad, its mechanism will harness energy, convert that energy to electrical energy and store it in batteries or the grid, for example. Although a vehicle driving over the device will lose an infinitesimal amount of kinetic energy, that tiny loss in itself produces benefits.

"The device can slow down traffic flowing onto the highway and in other areas," said Hoang. By replacing traditional speed bumps with "smart" speed bumps near schools or hospitals for example, the PT-EGen can help manage traffic while harnessing energy to power street lights and speed meters in the area. In a city such as San Francisco, with its steep hills, the PT-EGen has the potential to produce a significant amount of energy while helping cars slow down. In addition to the application of the PT-EGen as a smart speed bump, the device can also be installed along highways with traffic flowing as usual.

Just how much energy could potentially be harvested? The team calculated that with several devices installed on a one-mile stretch of I-880 in one day, PT-EGen could harvest over 85MWh in one lane alone, with very little impact on moving vehicles. This energy could power 100 electric cars to each travel 100 miles.

The Green Corridor played its role in the Big Ideas win. "Carla [director of the Green Corridor] acted as our mentor," said Le. "She put us in touch with NREL [National Renewable Energy Laboratory], where we will produce parts for our prototype this summer. She also helped us find a test site." This collaboration with the Green Corridor will make it possible to create and test the PT-EGen device in the coming months. It's a big idea that could have a big impact.


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