By Leah Elison
The Utah Transit Authority has begun testing three experimental buses that use both diesel and electric power to reduce emissions and improve performance.
The hybrid buses, which are not yet in production, alternate between diesel and electric power sources to maximize efficiency and harness energy that is usually lost as heat.
'This is the first step toward a newer technology,' said Kris McBride, UTA spokesman. 'Right now, everything is working well.'
The new buses, created by Allison Electric Drives, are expected to use 20 percent to 30 percent less fuel than a conventional bus and cut emissions by 50 percent, said McBride.
Experimental technology on the buses recovers excess energy that usually escapes the system as heat when a vehicle decelerates.
The energy charges batteries on the roof of the bus and runs two electric engines.
'You recapture energy that would normally be lost in breaking,' said Nathan Rues, a field engineer for Allison Electric Drives. 'Electricity is a pretty convenient form of energy.'
Computers, not bus operators, decide when to transition between diesel and electric power based on the speed and acceleration of the vehicle, Rues said.
The pairing of electricity and diesel is particularly advantageous because electrical engines work best when rotations per minute are low and torque is high, the opposite of internal combustion engines.
The computer will blend the two systems almost constantly, Rues said, although electricity will be the dominant power source when the bus is accelerating and decelerating.
'The electrical engines take a lot of pressure off the internal combustion engine,' Rues said. 'Electricity provides the most get up and go.'
With the electric engines, the new buses can accelerate significantly faster than the old buses, he said.
UTA buses can accelerate from 0 mph to 40 mph in 30 seconds; the new buses can reach the same speed in just 17 seconds.
'They have a lot of get up and go,' McBride said. 'In fact, they have quite a bit more get up and go than a normal bus.'
The new buses also cost quite a bit more than a normal bus, about $150,000 more per vehicle.
McBride said a federal grant paid for 80 percent of the $515,000 per vehicle, and once Allison Electric begins full production, the price should decrease.
Allison Electric allowed Salt Lake, as well as Seattle, Philadelphia, Minneapolis and Houston, to purchase the buses as part of its product testing.
'Anything we can learn we would rather learn now,' Rues said. 'We can drive it all we want, but we need real world experience.'
He said Allison tried to pick locations that would represent a variety of environmental conditions; Salt Lake was chosen because of its high altitude, extreme temperatures and dry climate.
The UTA wanted to participate so it could get a sneak peak at the new technology and assist in the development of environmentally friendly transportation.
'This is the first step to getting a complete hydrogen fuel-cell bus that does not rely on petroleum at all,' McBride said.
A bus powered by a hydrogen fuel cell would run completely on electricity.
Brigham Young University students have been studying electric vehicles that have engines similar to those used in UTA''s new buses, said Thomas Erekson, Director of School of Technology.
Erekson said hydrogen fuel cells have not yet been developed enough to be used in races, mostly because of difficulties in hydrogen storage and high costs.
'All this learning is going to be necessary and required for fuel cell vehicles,' Rues said.
Even if a vehicle is running on a fuel cell, it will still lose energy as it comes to a stop.
Rues said it is likely that batteries will be put into the fuel cell vehicles for the regenerative braking aspect.
'It is a gradual step,' he said. 'The battery technology and electric transmission will be very useful when the fuel cell technology is ready. We will not have to reinvent all of this; it''s a head start.'
When the technology does become available, UTA wants to convert its entire fleet of 596 buses, but at this point the change is not feasible, McBride said.
The three new buses will be used in the Salt Lake area so technicians will be close by to study the functionality of the buses.
Operators and riders will see no differences between the new buses and the old, except the paint job.