METRO Goes Green with Hybrid Buses
Tuesday, January 23, 2007 11:06 AM
Hollywood celebrities are seeing green on the road – and now more of METRO will be doing likewise.
Cameron Diaz, Tom Hanks, Gwyneth Paltrow and Ed Begley Jr. are just some of the movie stars who are driving hybrid cars and using clean energy, according to Wired.
Starting in March, the first of 40 hybrid buses will be delivered to METRO, with all 40 here by June, said John Walsh, METRO’s senior director of bus maintenance. These diesel-electric hybrid buses are New Flyer buses with a hybrid drive systems manufactured by General Motors with the Allison Electric Parallel drive. Allison is a division of GM. 
METRO already has four, retrofitted hybrid buses on the road, but this new delivery will boost METRO’s clean energy buses to 3.5 percent of its fleet of 1,221 buses, said Andrew Skabowski, director of maintenance support functions.
The 40 hybrids will replace 30 buses.
“The negative perception that people have about buses is that they’re smelly, big, smoke-belching vehicles, and this changes all that,” said Walsh who masterminded New York’s program of hybrid buses before moving to Houston. “The noise signature goes down; the emissions are as clean as or cleaner than compressed natural gas. The operating cost goes down.”
While the New Flyer buses cost $120,000 more than a conventional bus, METRO expects to save 25 percent on fuel, said Walsh. “We will get that money back in six or seven years,” said Walsh, adding that the lifetime of a bus is 12 years.
Comparative fuel economy data shows that the average hybrid fuel economy is 4.33 mpg compared to the average conventional fuel economy of 3.58 mpg.
“This is an evolving and maturing technology. The good part is that there are a number of competitive systems out there that are becoming more and more robust. And as the market penetration increases, the cost differential will go down, the reliability will go up, and the performance improves – which is the natural evolution of technology,” said Walsh.
Here’s how a diesel-electric hybrid bus works.
From 0 to 20 miles per hour, the New Flyer hybrid bus uses electricity. “Then it uses a torque blend – blending the best of both worlds – the electric and mechanical function of the engine to prepare the vehicle. Once it’s up to 65 miles per hour, the internal combustion takes over,” explained James Blocker, METRO supervisor of advanced technology. “The reason is that the hybrid is most efficient at stop-and-go duty cycles, similar to what our buses do.”
When the bus driver stops pressing the accelerator, then regenerative braking occurs.
“It turns the hybrid system Motor B into a generator – and that in turn, slows the vehicle down and puts that energy back into the battery pack. Now when you’re ready to take off from the next stop, you put energy out again. You’re regenerating energy back into the battery pack every time the bus takes off and on,” said Blocker.
And that process extends the life of a bus’ brakes because the system uses the hybrid drive in lieu of the foundation brakes until the bus slows to 3 to 5 miles per hour. The foundation brake is one of the costliest items to maintain on a bus. It costs $1,800 to replace front and rear brakes.
“The braking energy that is normally wasted becomes energy that goes back into the battery pack,” said Walsh. “So brake pads don’t wear out as quickly.”
Here are the specifications of METRO’s new hybrid buses:
Manufacturer: New Flyer of America
Model: Low-Floor Bus
Quantity: 40
Seats: 39
Length: 40 feet
Year: 2006
Passengers should notice a pleasant difference on the hybrid buses.
“It will be much smoother. It will be quieter. Riders will certainly notice very little emissions besides the heat signature from the stack,” said Walsh.
And you might feel a little better knowing that you’re riding a green bus. How clean is it? METRO expects these reductions in emissions:
* 77% less particulate matter (PM)
* 56% less carbon monoxide (CO)
* 44% less oxides of nitrogen (NOx)
Since hydrocarbons are inherently low in diesel engines, the emission test results show up higher for that. These measurements are based on results from the National Renewable Energy Labs. Read the report here.
“Nothing is free. You’re making an investment, and the investment has some cost. What you look at is whether or not that cost is approximately equivalent to the standard propulsion system and whether or not you get some benefit,” said Walsh.
What will make METRO’s conversion to hybrid buses successful?
”The fact that the customers notice a difference,” said Walsh. “Besides knowing that it makes a difference that we’ve improved the regional air quality and we’re doing what we can to reduce our energy consumption."