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Feature                                                       Pages 35-39

 

Alternative Energy Busing    

School district fleets are giving road tests to all-electric vehicles and hybrids

BY SCOTT LAFEE

In 1965, the trade publication School Bus Fleet imagined what the “School Bus of the Future” might look like, complete with renderings by engineers at Wayne Works, one of the major manufacturers of school buses at the time.

The vehicle resembled “something from a Jetsons’ episode,” says the magazine’s current publisher, Frank Di Giacomo. It floated on a cushion of air, the driver perched in a plastic bubble from which he or she operated a “uni-control” that combined steering, acceleration and braking in a single system.

Electric bus
A new electric school bus.

Almost half a century later, the airborne school bus obviously has not yet arrived, but other, more grounded modes of alternative energy transportation may be taking off.

An estimated 25 million children (more than half of the nation’s K-12 student population) ride 480,000 school buses nationwide each year. All of those buses are painted yellow (by law) and almost all (95 percent) are powered by diesel fuel — an estimated 822 million gallons of the stuff, according to the American School Bus Council. At $4 per gallon, that works out to an annual $3.28 billion fuel bill.

In recent years, school districts have converted portions of their bus fleets to cleaner-burning, sometimes cheaper, alternative fossil fuels, such as compressed natural gas or propane. Others have adopted biodiesel, which combines regular diesel with fuel derived from organic sources, usually vegetable oils or animal fats. For example, the 135,000-student San Diego Unified School District, California’s second-largest district, recently announced plans to convert its 500-bus fleet to B20 (20 percent organic fuel) biodiesel by the end of the 2014-15 school year.

The number of biodiesel school buses on the road seems likely to grow, but the headline grabbers are two other technologies — all-electric vehicles and hybrids, which employ an electric motor working in tandem with a conventional internal combustion engine.

Sparking an Idea
The promise of electric-vehicles long has energized transportation designers and engineers. The first such vehicles — locomotives, then cars — debuted in the mid-19th century, but the technology never gained self-sustaining momentum and eventually was overrun by the cheaper, more powerful and more reliable internal combustion engine.

John Clements
John Clements of California's Kings Canyon Unified School District in front of the district's electric school bus.

The current electric-vehicle renaissance, based upon new, advanced battery technologies, broadly emphasizes automobiles, but a New York-based bus maker named Trans Tech, partnering with Smith Electric Vehicles of Kansas City, Mo., has introduced an all-electric, zero-emission school bus. The first bus, a 42-seat Type A, was delivered earlier this year to the sprawling and logistically challenging Kings Canyon Unified School District in California.

“This district covers almost 600 square miles, from the Central Valley floor at 230 feet up to 6,700 feet in the Sierra Nevada Mountains,” says transportation director John Clements. Of the 10,000 students enrolled in Kings Canyon, almost half ride district school buses.

Clements, who began as a bus driver with Kings Canyon 27 years ago, long pursued cleaner, greener buses. The district sits in a part of the state plagued by chronically poor air quality, the combined consequence of topography, weather, industrial agricultural practices and a growing regional population.

In the 1990s, Clements was involved in a demonstration electric-bus project, but the effort never actually got rolling. When Trans Tech executives visited his district a couple of years ago, he pushed hard for a second try and eventually helped advise the development of the eTrans bus.

The new electric bus, he says, will be used well within its current technological limits — 100 to 130 miles on a full battery charge, with a top speed of 60 mph. “The planned route will be two 20-mile loops, one in the morning, one in the afternoon, with lots of stopping and going in a small community,” Clements explains. “I’ve tested the route and finished at 73 percent battery capacity.”

He expects the bus to be an immediate money saver. Battery recharging will be done between the morning and afternoon routes or at night when electricity rates are lower. The anticipated cost: About $20 for a full recharge. Clements figures he’ll save the cost of the 16 gallons of diesel fuel he’s not using each day, roughly $60, plus reduced maintenance expenses. The bus requires no oil or transmission-fluid changes.

“I think it will pay for itself in time,” Clements says. “Electric technology has greatly improved. The batteries now are lithium-ion, just like cell phones. They should be reliable, and they’ll be under warranty.”

Of course, those savings won’t occur until the bus is actually in operation, which might not be for awhile. Though Clements proudly claims his district is the first in the nation to possess an electric school bus (the Plainview-Old Bethpage Central School District on New York’s Long Island hopes to have the second bus in operation this fall), Kings Canyon’s vehicle has yet to carry a student.

“Right now, it’s being shipped around the country to different shows and conferences and put on display,” Clements says. “But hopefully we’ll have it on the road by the last week in June, before school’s out.”

Trans Tech, meanwhile, expects to have full production of its eTrans bus in gear by the end of the year.

Mixed Results
If electric school buses are just getting started, hybrids already are in motion. Since the late 1990s, numerous school districts have experimented with the vehicles, which combine multiple power sources in a single drivetrain. 

READ MORE:

A Glossary of Alternative Busing Terms

Like the electric bus, hybrids have a comparatively high up-front cost, which has tended to limit interest and investment by school districts. The number of hybrid school buses currently on the road is estimated to be about 200. Most districts with hybrids have just one or two.

An exception is the 100,200-student Jefferson County Public Schools in Louisville, Ky., which boasts 32 hybrid buses in operation, each holding 66 passengers, with another 18 on order, according to Michael A. Mulheirn, the executive director for facilities/transportation.

Mulheirn says the district’s hybrid buses, representing 5.2 percent of the district’s total fleet, have been well-received by both drivers and riders, adding they “potentially improve fuel mileage by two miles per gallon” and appear to reduce maintenance costs.

Empirical data are scarce. Advanced Energy, a North Carolina-based advocacy group that has promoted the development and use of alternative energy systems like hybrid school buses since 1991, says its lab tests indicate a 10 to 75 percent improved fuel economy for plug-in hybrid buses over conventional diesel vehicles.

In 2008, researchers at Iowa State University’s Institute for Transportation collaborated with Advanced Energy to provide hybrid, 65-passenger buses to a pair of small school districts: the 1,600-student Nevada Community School District east of Ames, Iowa, and the 700-student Sigourney Community School District, midway between Des Moines and Davenport, Iowa. Each bus cost $217,000, but the school districts paid just $70,000, with the rest covered by grants and outside agencies, such as the New York State Energy Research and Development Authority. The funding included a three-year study of the buses’ performance.

The institute’s researchers published their findings in 2010: Average fuel economy for the Nevada hybrid bus was 9.12 miles per gallon, compared to 6.91 mpg for a standard diesel control bus, a 30 percent improvement. For Sigourney, the hybrid bus averaged 8.94 mpg compared to 6.42 for the control, a 36 percent improvement. The average cost per mile for the Nevada hybrid was 38 cents compared to 43 cents for the control; the Sigourney hybrid cost 28 cents compared to 34 cents for the control.

Uneven Performance
Fuel economy wasn’t the only concern. Diesel engines produce heavier, more particulate-laden emissions that health experts say place bus-riding children at greater respiratory risk. However, analyses of emissions for the two Iowa buses were inconclusive: The hybrids sometimes produced greater emissions than diesel buses, sometimes less.

More problematic, the researchers found, was the actual performance of the buses. In both vehicles, there were consistent problems with recharging the vehicles’ batteries, which resulted in the buses’ electric motors being knocked offline for months. The buses still ran, but it meant the V8 diesel engines shouldered the entire workload. They weren’t hybrids.

Shauna L. Hallmark, an associate professor in civil, construction and environmental engineering at Iowa State and co-author of the study, says the electrical issues were troublesome, but not beyond resolution. “We believe the battery problems were only related to the first set of buses on the market,” she says. “We have not seen any further studies showing that this continues to be the case.”

Hybrid bus
The Napa Valley Unified School District's
engine-off hyprid bus.

Ralph Knight agreed. As director of transportation for the 19,200-student Napa Unified School District in Northern  California, Knight is another longtime proponent of alternative-energy school vehicles. In 1998, he obtained the state’s first electric school bus, only the second in the nation.

“It got 60 miles out of a charge. It was a very big deal,” Knight recalls. But the vehicle was also something of a lemon. It broke down a lot. “The technology was new. We were always tinkering with it. If that bus was on the road one day a month, we were lucky.”

Nonetheless, the bus remained in service for 3½ years until its batteries finally “went belly-up,” Knight says. When it was running, the cost of operation was a paltry four cents per mile.

In the years since, Knight has converted a significant chunk of his 70-bus fleet to alternative energy sources. Thirty-seven buses run on compressed natural gas, which is cheaper than diesel, burns cleaner and is slightly more fuel efficient. Like hybrids, however, initial CNG vehicle costs are higher than standard diesel buses and require an investment in or access to specialized fueling stations.

Knight reserves his greatest enthusiasm, however, for his small but growing fleet of hybrids. The district obtained its first plug-in hybrid bus in 2007, part of a broader national pilot program. The $249,000, 55-seat bus gets 13 miles per gallon, double the fuel efficiency of a diesel. It’s still in service, and Napa Valley Unified recently purchased five 71-passenger hybrids from Thomas Built Buses, based in North Carolina.

Knight says current hybrid technology is much improved, but it’s still far from fool-proof, which means school transportation departments must be charged with learning how to maintain the new technology.

In 2007, the Austin Independent School District in Texas used a variety of federal and local grants to purchase a 72-passenger hybrid school bus. It gets 12-13 mpg, but it’s also plagued by electrical malfunctions.

“Overall, it runs pretty good,” said Kris Hafezizadeh, Austin’s director of transportation, “though right now it’s in the shop with an issue involving its battery pack. We’re trying to figure out what the problem is.”

The Road Ahead
Hybrid durability is a common, continuing concern. But Ewan Pritchard, program manager of the Advanced Transportation Energy Center at North Carolina State University, says technical advances have helped hybrids turn a corner, both in reliability and in fuel economy.

“I think we have seen the worst as far as initial costs [and] performance. It will only get better from here. I believe we will see paybacks of under five years within a few years and eventually paybacks of under two years.”

Indeed, Pritchard argues that school buses are the perfect use of hybrid and electric technologies, saying, “All-electric and plug-in (hybrids) make more sense for school buses than for any other vehicle, including commuter vehicles.” The reason lies in how they are used, in the distances, speeds and driving typically seen with school buses.

“Many of the districts that [experimented early with hybrid buses] did not perform as well as others because they went against our recommendations and put the buses on their longest routes. The logic they were using was that they could save more money by putting the highest miles on the most efficient bus,” Pritchard adds.

“Unfortunately, the buses were designed for the average bus usage — 44 miles or less per route, lower urban/suburban speeds like 35-45 mph. Hybrid buses do not get the type of benefits needed when driven at 55 mph for 20 miles at a constant speed. A district can see a 65 percent improvement in fuel economy if it is driven in stop-and-go traffic for 20 miles at 30 miles per hour, but will see more like 20 percent if driven wrongly.”

In other words, electric or hybrid buses work best on urban or suburban routes that are relatively short, do not require high speeds and involve lots of stopping and starting. (Kinetic energy created by braking is redirected back to the bus’ batteries.)

Uneasy Economics
The biggest drawback to hybrids at the moment isn’t technological but economical. They simply cost a lot. Few, if any, districts can afford to purchase them outright. Invariably, the buses are acquired with significant assistance from federal, state or local agencies and programs.

The Kings Canyon electric bus, for example, reportedly cost about $230,000 — $50,000 more than a similarly sized diesel bus. The district paid only a fraction of that price, however — about $15,000. The remaining funds were cobbled from four other funding sources, including a California state program that helps school districts purchase alternative energy vehicles, providing up to $40,000 per vehicle.

“There are lots of programs out there with money that promote alternative energy transportation, both government and private,” says Clements, the transportation director at Kings Canyon. “You have to look for them, but if you play your cards right, you can come pretty close to fully funding a vehicle.”

Certainly Clements is driving toward more hybrids and other alternative energy vehicles in his district. Advocates like him believe the vehicles’ time has arrived. And with fossil fuel prices rising inexorably and environmental and health concerns unresolved, they may be right. The next school bus you see also might be one you don’t really hear. At least until somebody figures out how to convert the abundant free energy of school bus riders into fuel that makes their school bus go, too.

Scott LaFee is a writer with the University of California, San Diego Health Sciences in San Diego, Calif. E-mail: scott.lafee@gmail.com

 

 

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