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.

George Karbowski, director of operations and maintenance at Foothill Transit, concurs with Pezoldt. Although the price of electricity in southern California does not enable as much savings as LINK's—about 68 cents per kilometer for diesel versus about 31 cents per kilometer  for electricity—Karbowski says anecdotal evidence suggests the company is saving greatly in other areas.

"Given that our electric buses do not charge in the yard, they are actually available for up to three extra hours each day because they don't have to wait in the refueling line," he says. "Also, a typical diesel bus requires an inspection every 45 days that uses $1,100 in supplies and 10 man-hours. Our Proterra buses take three hours and don't use any filters, oils or spark plugs—or anything like that—and have much lower preventative maintenance costs." Karbowski also attributes lower lifetime brake-associated costs to the regenerative braking system in the bus, which uses the braking force of its electric motor to generate electricity, saving the physical brakes from as much wear and tear.

Greener transit
Although both operators are focused on saving money and increasing operational efficiency as the driving goals of their electric bus programs, they readily tout the green aspects of their projects as well. Aside from having zero tailpipe emissions, both types of buses use some of the cleanest electricity in the world. In Wenatchee more than 96 percent of its power comes from seven dams within 160 kilometers and—at a residential rate of 2.2 cents per kWh—is also some of the cheapest electricity in the country, thanks to the well-established public utility traditions of the region. California already has more than 20 percent of its electricity coming from solar, wind and hydropower, and has set a statewide goal of 33 percent renewable power consumption by 2020. But Foothill has gone even farther by purchasing 100 percent renewable energy credits to provide all the power for its electric buses.

Both transit operators plan on expanding their electric bus service and have received additional grants from the Transit Investments for Greenhouse Gas and Energy Reduction (TIGGER) program—an offshoot of the stimulus package. With an additional $2.5 million from TIGGER, LINK plans to buy five more Ebus trolleys and three additional fast-charging stations. With $10 million more, Foothill plans to buy between nine and 11 additional Proterra buses, resulting in the full electrification of an entire bus route.

Although Foothill and LINK have funded the vast majorities of their projects with federal grant money to this point—and have hedged against the risk inherent in being pioneers with that money—both say the buses and associated equipment are now at the point where they compare very well in terms of up-front costs with purchasing new diesel—or even compressed natural gas–powered buses.

The Ebus trolleys already cost less than comparable diesel-powered ones, and even the larger 12-meter-long Proterra buses carry a reasonable price tag. "Our initial purchase of Proterra buses cost us about $1.2 million each, but it will likely cost us $800,000 each for this next batch," Karbowski says. "Compare that to approximately $650,000 for a compressed natural gas bus and it's getting closer. With higher volume it will likely be completely on par soon."

Early results being what they are, other public transit operators have come knocking with an interest in the emerging technology. According to Pezoldt, Wenatchee's much larger neighbor to the west, Seattle, is learning a thing or two from LINK's experience and plans to invest in the technology in the next couple of years. In California Proterra just inked a deal with the San Joaquin Regional Transit District for two more of its battery-powered buses. Given that the pioneers' experiences have not revealed a downside yet, it's no wonder interest is rising quickly.