Using stimulus funds, two transit systems in California and Washington State pioneer a cleaner, greener and less expensive method of transportation
?| June 11, 2012?|
Better lithium ion batteries have led to an explosion in availability of plug-in passenger cars. And now, thanks to relatively cheap electricity and the simplicity of the electric drivetrain, electric vehicles have even more potential for use in the extremely cost-sensitive public transportation arena?a concept that is only just taking root.
In particular, two projects funded mostly by grants from the American Recovery and Reinvestment Act of 2009 (ARRA)?better known as the stimulus package?are pioneering new ways that public transit systems both large and small can think about total cost to operate buses and their environmental impact in the burgeoning era of cheaper, large format, lithium ion batteries.
Different needs, same goal
Spanning from Pasadena to Pomona in an area east of Los Angeles, Foothill Transit is a large bus operator serving about 14 million passengers per year over a 900-square-kilometer area. On the other end of the spectrum is LINK Transit, based in rural Wenatchee, Wash., which conveys just one million passengers annually?but unlike the compact footprint of Foothill Transit, its lower passenger volume is spread out over an area about 10 times larger.
Both public transit operators place significantly different demands on their buses, but each has trained its long-term vision on battery power as a way to reduce costs, improve operational efficiencies and reduce environmental impact. During multiple-year electric bus projects that were funded in 2009 but didn't pick up steam until 2010 (and in the case of LINK, still aren't fully in place), the operators are using different equipment and battery technology to see if their projections pan out in the real world. The projects were mostly funded by ARRA grants, with LINK receiving $2.9 million (of which all went to purchasing electric buses and associated charging equipment) and Foothill receiving $21.3 million (of which only a portion went to the buses and associated equipment).
Lithium ion batteries are still not energy dense enough hold more than the equivalent of between four and eight liters of gasoline in a battery package small enough to put on a bus. Nevertheless, inherent efficiencies in the electric drivetrain enable significant increases in fuel economy. Whereas a typical 12-meter-long, diesel-powered transit bus might return between one and two kilometers per liter, the electric ones that Foothill is running average the equivalent of 8.5 kpl. After some quick math it is apparent that 8.5 kpl combined with 7.5 liters of energy storage is not enough to fuel the hundreds of kilometers a bus might need to travel in a day. To get around this, both Foothill and LINK have added ultrafast charging stations in the middles of their buses' loops.
Foothill Transit operates three 12-meter long, 35-passenger buses built by Greenville, S.C.?based Proterra. Each relies on batteries that supply 72 kilowatt-hours and runs on a 27-kilometer-long loop that handles 5 percent of the yearly ridership. At specially built fast charging stations in the Pomona Transit Center the buses can fill up within 10 minutes on their normally scheduled layover, meaning they never have to travel more than 27 kilometers between full charges?about half what their rated battery capacity can provide. LINK's system is similar, although it uses five, Ebus-built, seven-meter long, 22-passenger trolleys with 28 kWh-batteries that travel on two separate eight-kilometer-long loops and can be filled in about seven minutes with a fast charge at the downtown Wenatchee Transit Center.
LINK originally planned to have its electric trolleys up and running by late 2010, but issues with the battery cooling system and manufacturing of the fast-charging station delayed full operation until later this year?although the trolleys are currently running for about two hours each day without fast charging. "There's nothing off-the-shelf about our trolleys," says Greg Pezoldt, special projects coordinator at LINK Transit. "As the first electric trolley of its kind, everything we have done with Ebus we've had to develop and sometimes redevelop. Even with the delays we're still excited about it, and we have an ultimate goal of electrifying the entirety of our Wenatchee and East Wenatchee routes."
Cost savings achieved
It is no wonder LINK is still bullish on the endeavor: Pezoldt says a comparable diesel-powered trolley would cost about $435,000 and each electric trolley built by Downey, Calif.?based Ebus costs significantly less at $370,000. On top of that, diesel fuel for the same trolley on the same route runs about $1,200 per month, whereas the inexpensive and green hydropowered electricity used for the Ebus trolley comes in at approximately $100 per month?less than one tenth the cost. The biggest question revolves around battery life, but even with the worst-case estimates, Pezoldt says LINK still comes out significantly ahead with electric bus operation in terms of lifetime fuel and maintenance costs.
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