Recycling old buses into better than new by electric repowering

by Peter Corbett

America’s push to put cleaner and quieter buses on city streets, highways and in school zones is gaining speed.

New buses with hydrogen fuel cells and battery-electric systems are rolling out of a relatively small supply chain of manufacturers to transit agencies, school districts and bus operators. With demand exceeding supplies of new buses, look for busing providers to convert or repower at least some of their diesel fleets to battery-electric vehicles.

Making the old new again is a more affordable option, and delivery time is much faster, said Tim Reeser, CEO of Lightning Systems, a Loveland, Colorado-based developer of electric-vehicle drivetrains since 2008. “It can’t just be all new buses,” he said of the switch to electric buses. “Repowering has to be part of this proposition.”

In 2018, Lightning Systems converted a 35-foot Gillig transit bus from diesel to a battery-electric system for the city of Boulder, Colorado, at a cost of $260,000 for the 15-year-old bus.

A comparable new electric bus costs close to $750,000 on the low end. Boulder is buying four new electric buses at that price next year with federal funding and plans to convert nine more diesel buses to electric as funding is available, said Lyndsy Morse, a spokeswoman for Via Mobility Services, Boulder’s transit operating company.

The additional four repowered buses from Lightning Systems are priced at close to $400,000 each, she said.

“Still, it’s significantly cheaper to convert a bus than to buy a new one,” Morse said. “The electric bus is quieter than the old diesel bus, and it’s better for the environment. We got to recycle a bus instead of destroying it.”

Reeser noted it can take two years to take delivery of a new electric bus, while conversions can be done in about six months.

Environmental goals

Transit agencies are investing in costly new and repowered buses to curb greenhouse-gas emissions and meet clean-air regulations.

One of the most stringent new regulations was adopted last year in California. It requires all newly purchased transit buses in California be zero-emission vehicles by 2029 and all transit buses must be zero-emission by 2040. Hybrid and natural-gas-powered buses are not considered zero-emission vehicles under the state’s guidelines.

California has close to 12,000 transit buses, and only about 1,000 of those will be zero-emission vehicles as of 2020, up from 153 in 2018, according to the California Air Resources Board.

Repowering existing transit buses, which generally have a life span of about 12 years, is not as simple as swapping out an electric motor and drivetrain for the diesel engine and transmission.

Lightning Systems starts with any repairs to the bus chassis or other components that would be part of typical heavy maintenance. The electric motor is about one-third the size of the diesel engine. Removing it and the fuel tank creates space in the back of the bus for battery packs to power the electric bus.

Motorcoaches can be retrofitted with battery packs in the engine and luggage compartments. In addition to the rear of the bus (where the fuel tank was located), battery packs are installed behind the driver, under one row of seats at the front of the bus and on the roof. Crash-protection frames are built around the battery packs. The heat exchangers for the batteries’ thermal management system also are on the roof.

The company used 10 battery packs, each with 32 kilowatt hours of energy, on Boulder’s HOP transit bus, which serves downtown and the University of Colorado campus. That’s enough energy to give the bus a range of 160 miles, Reeser said.

Lightning Systems gets its lithium-ion batteries from Samsung and LG Chem Ltd. The water-tight battery packs have mechanical and electronic safeguards with thermal controls to keep them at ideal temperatures in summer and winter.

Winter conditions reduce the range about 30 percent, and range drops about 15 percent in high heat, since the heating and cooling system draws down the power supply.

New electronics and wiring are an important part of the conversion.

Lightning Systems also installed a regenerative braking system on the Boulder bus that generates energy when the driver releases the accelerator and applies the brakes. The braking system requires less frequent maintenance, and there’s additional savings from not having to do oil changes on electric buses.

Reeser said the big savings are in fuel costs, with an electric bus getting the equivalent of up to 20 miles per gallon, compared to 6 mpg for a diesel bus. “It takes about one-fifth of the energy to do the same job.”

Financing is a key element for the electrification of bus fleets, since up-front costs for new electric buses are significantly higher than for diesel buses. Operators can use fuel savings to offset the costs of financing a new electric bus or repowered bus, Reeser said.

However, industry analysts predict the price gap will narrow for diesel and electric buses. A Bloomberg New Energy Finance report from 2019 concluded that “electric buses will reach unsubsidized upfront cost parity with diesel buses by around 2030. By then, the battery pack in the average e-bus should account for around 8% of the total e-bus price—down from around 26% in 2016.”

If growing demand brings down e-bus battery prices, cost parity with diesel buses could be achieved by the mid-2020s, Bloomberg said.


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