Power Supply

In not quite two years, the school bus industry has endured several once in a lifetimes. First, the COVID-19 pandemic shut down schools and pretty much the rest of society. Supply chain disruptions, long bubbling under the surface, erupted. Now inflation has set a chokehold.

Amid these challenges, school districts are setting their sights on the mode of power for their next bus and fleet vehicles purchases, decisions that in some states are largely being made for them by politicians: Zero emissions, at least from the tailpipe.

For this industry, so far, zero emissions translate to battery electric school buses, though other renewable alternatives are showing promise. But for all the environmental and operational savings benefits of these electric vehicles, there is consensus even from the most ardent advocates they are not developed to the point required range, operational reliability, manufacturing output, grid resiliency, etc. for massive, wide scale adoption. Certainly, the numbers in the pipeline are impressive, spurred largely by federal and state grants.

Even then, money awarded might only cover a fraction of the eventual purchase price for buses. Electric school buses are becoming more expensive, due to suddenly increasing battery costs due to shortages in lithium. That spells unwelcomed news for school districts that win U.S. Environmental Protection Agency Clean School Bus Program rebate funds this fall, regardless, if their applications specified electric or not. Internal combustion engine school buses aren’t immune to increasing production costs and resulting vehicle surcharges.

“We’re not seeing any of those [surcharges] roll back yet, even though at least at the commodity level, some of those prices have retreated,” commented Steve Tam, vice president of commercial truck and bus analyst ACT Research. “Of course, this begs the question, is there a structural issue going on here whereby once the genie’s out of the bottle, it’s not going back in? I’m afraid there’s probably some validity to that thought.”

He added that progress is being made on supply chain constraints but not fast enough to allow manufacturers to reduce record backorders. The result will be continued delays in delivering on most new orders, which spells a dilemma for school districts and bus companies. “They’ve been denied replacement level kinds of volumes for the last two years,” Tam observed.

Patrick Couch, the senior vice president of technical services for alternative clean technology consultant Gladstein, Neandross & Associates, likened the current procurement cycles faced by school districts to having the capital spend-ing rug pulled out from beneath them. “The way they’re going to have to deal with this is, well, we were going to get 20 but now we’re going to have to get 16,” he explained. “What we typically see in those cases with a lot of fleets, but definitely the school bus fleets, is that they just try to keep the existing units that they have working, even though they’re past their service life.”

Considering at least 80 percent of the legacy fleet is powered by diesel, according to this magazine’s analysis of annual manufacturing data, replacement levels could be further impacted by the EPA’s proposed rulemaking to further reduce oxides of nitrogen emissions from heavy-duty engines. NOx emissions would be reduced by at least 47 to as much as 60 percent by 2045.

As reported in March, when the EPA solicited pub-lic comments to its proposal for updating the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program, engine and vehicle manufacturers would have two options to obtain compliance. The first would require reducing NOx emissions in model-year in two steps, beginning with an 82.5-percent reduction for model-year 2027-2030 engines to 0.02 grams per brake horsepower-hour (g/bhp-hr). Then, for model-year 2031, NOx reductions would reach 90 percent, though emissions could “drift” up to 0.040 g/bhp-hr during the useful extended life. The second option would implement standards with a single step in 2027.

Either option for diesel would be difficult if not impossible for OEMs to meet. In a response filed in May, Jackie Yeager, director of emissions and fuel efficiency policy for Cummins, wrote that company design target analysis with updated inputs from the EPA proposal showed that option one is not feasible for diesel and should warrant “no further consideration.”

In analyzing the effects of option two, Yeager wrote that compliance would be “challenging but achievable with advanced technologies in [model year] 2027.” This would mean the latest round of additional and costly enhancements to diesel systems, such as the dual selective catalytic reduction systems required since 2010. Yeager noted that SCR as well as cylinder deactivation are not currently in production for heavy-duty vehicles at the necessary emissions levels, “so considerable effort is still needed to develop, package and validate the new components, especially considering the more diverse drive trains and vehicle configurations, duty cycles, applications, and much longer useful life of heavy-duty vehicles.”

Even so, concerns remain about option two, as it relies on “optimistic assumptions,” added Melina Kennedy, Cummins’ vice president of product compliance and regulatory affairs, during a public hearing in April. She noted significantly increasing the useful life of engines at the same time as introducing new technology will further increase purchase prices for customers and “will likely impact” adoption.

“We would like to work with EPA and other stakeholders to agree on alternative solutions that ensure low in use emissions yet avoid high initial purchase prices,” she said.If the proposal goes through, some in the industry have questioned the ability to continue manufacturing diesel-powered school buses. One could argue that’s largely the point.

The latest CNG and propane engines already meet the EPA proposal requirements of 0.02 g/bhp-hr. But with so many diesel school buses on the road and amid escalating new prices, OEM and dealer support will continue to be paramount for decades to come, especially as renewable diesel as well as renewable CNG and propane becomes more widely available.

The Maintenance Option:
Savvy fleet managers for years have encouraged data analysis to drive decisions on when to continue operating an older bus or cutting bait of a depreciating asset and buying new, the latter which brings the added benefit of introducing the latest safety technology. But amid out-of-control new purchase costs, the industry is now being advised to double down on maintenance, no matter the fuel or energy, to keep buses in operation longer.

“You’re going to end up having to maintain your vehicles better than maybe you’ve done in the past because you’re going to have to make those vehicles last longer than they used to,” commented Robert Williams, the assistant director of fleet services for Cypress-Fairbanks Independent School District in Houston, which operates the largest student transportation operation in Texas.

“Even if you do have funds, and you’re able to buy, rather than 20 buses you are only able to buy 10. Well, that’s only 10 you are replacing. You really need to get rid of 20. You better maintain that fleet and take care of it.”

He added that a result could be some states and school districts being forced to relax replacement programs and again “carry those buses for 20 years” or even longer. Diesel powered school buses are built to last several decades. The same should hold true for other fuels and energy. But diesel buses of the 1970s, 1980s and 1990s were ultra high polluters. EPA mandates have reduced particulate matter and NOx by 98 percent from the late 1980s and projected through 2025.

Meanwhile, thousands of districts nationwide continue with new diesel purchases despite the trend toward zero or low-emissions alternatives. But diesel and forced regeneration is costing more and more to maintain, the main reason gasoline re-entered the Type C conventional space with a vengeance six years ago. New technology is addressing some of those costs, at least for model years 2017 and newer buses.

Just prior to the COVID-19 pandemic, Cummins and Zonar released Zonar OTAir. It is essentially a software update that allows Zonar to download from Cummins the latest engine control module data to address engine health and functionality in 2017 or newer models. When traditionally a fleet would need to perform an engine update, staff would have to schedule a work order for the affected buses and potentially remove them from service. The proper number of computer laptops would need to be available to plug into the engine, or the buses would need to be sent to an authorized dealer to perform the updates. With OTAir, all bus drivers or maintenance staff need is a cell phone or a tablet to access the Zonar app.

Michigan based school bus contractor Dean Transportation uses OTAir in about 450 of its over 1,650 school buses. “We found it that it certainly improves efficiency and allows us to keep our engines up to date in a more efficient manner than the traditional plug in and update,” said Christopher Dean, the company’s vice president of technology. “We can literally walk bus to bus, scan the QR code within the app, and start start the update. There is a real time savings there because, essentially, we can get 50 units all going at the same time.”

When OTAir was released, Zonar said the solution could save fleets about $120 per bus four times a year, citing the cost at the time of engine updates performed at a dealer. Fleet managers of 100 buses could therefore expect to save $48,000 a year.

It Will Take a Village:
The school bus industry needs a host of fuels to get where it needs to go. That’s where Cummins’ agnostic engine figures to move the needle and reduce costs at the same time. As widely reported on February, the company announced one engine platform for its B6.7 and L Series applications with unique cylinder heads to support CNG, diesel, gasoline, propane, and hydrogen.

Cummins is still eyeing a phased release of the new engine in the first half of 2024, with the first slated to be a 15-liter for Peterbuilt trucks. Gasoline will be the first B6.7 release for school buses, according to Cummins, likely followed by propane. Hydrogen will come next, at least for other medium duty vehicles. A hydrogen internal combustion engine is not thought to be a good candidate for school buses because it is cost prohibitive for school districts to implement and operate.

Daniel Gage, president of natural gas advocate NGVAmerica, noted that near-zero emissions CNG school buses more affordable than electric are already on the road. According to the federal government’s AFLEET emissions tool, the average cost of a battery electric bus is $300,000, though the latest figures School Transportation News received have ESB price tags trending over $400,000. “A natural gas unit is [currently] $130,000 per unit,” Gage added.

Plus, he pointed out, natural gas operates as a 1:1 replacement for gasoline or diesel, sharing a proven track record of extended range on a fully filled tank. “And range is not affected by severe hot or cold temperatures,” he added. “With similar range capabilities, no additional buses or drivers are required, an important consideration in today’s tight labor market where driver availability is a problem.”

Natural gas shares similar pump price savings with its propane cousin, especially as the federal Inflation Reduction Act extended the $0.50 per gallon equivalent tax credit, and savings to be had on maintenance, though the latter doesn’t come with the added infrastructure costs. Both fuels hold the distinction of being largely produced domestically, and they both have potential as renewable alternatives that can push the carbon index to zero or below.

“The propane industry has invested heavily in a renewable propane offering, which significantly reduces the carbon intensity of the fuel as compared to traditional propane,” said Todd Mouw, executive vice president of ROUSH CleanTech, which boasts the lion’s share of the over 20,000 propane powered school bus in operation nationwide. “It is commercially available today and supply and demand continue to grow. We are also looking at ways to blend renewable propane with renewable [dimethyl ether] to further reduce our environmental impact.

“All of these investments point to one thing … we believe that propane has a long runway over the next de-cade to help school districts meet their economic needs and sustainability goals.”

Editor’s Note: As reprinted in the October 2022 issue of School Transportation News.

Related: The Power to Control Energy
Related: Watch: School Budgets Affected by High Diesel Prices
Related: The Evidence is Clear: Electric School Buses are the Best Choice to Reduce Emissions
Related: Technology Lessons Learned From Chowchilla

May 2024

This month's issue features articles on how technology can further student safety and optimize transportation operations. Learn more about...

Buyer’s Guide 2024

Find the latest vehicle production data and budget reports, industry trends, and contact information for state, national and federal...


Is your district on a 4-day school week?
107 votes