Can electric buses serve as backup batteries on wheels?

A California pilot project is testing transit buses as a source of mobile backup power. If it works, they could replace dirty diesel generators during blackouts.

A large white public transit bus
A state-funded pilot project will test how AC Transit’s electric buses can be used to power an Oakland, Calif. public library that serves as a community resiliency center during grid outages. (AC Transit Media Affairs)
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Can electric buses become batteries on wheels, ready to back up public buildings during wildfires, heat waves and other grid emergencies? A new project in Oakland, California intends to find out. 

It’s called the V2B Oakland project, and it’s backed by $3.2 million in California Energy Commission funding, another $400,000 in matching funds from nonprofit West Oakland Environmental Indicators Project and regional transit operator AC Transit, and contributions from a long list of technology partners. 

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The goal is to prove out the technology and techniques to allow the thousands of electric buses coming onto U.S. roads in the coming years to be used in place of diesel generators for backup power when the grid fails, said Jason Hanlin, director of technology development at the Atlanta-based Center for Transportation and the Environment, which is taking a lead role on the project. 

V2B stands for vehicle-to-building,” and it’s one of many flavors of technology that tap electric-vehicle batteries to power homes, buildings or the broader power grid. For this project, the building is the West Oakland Branch of the Oakland Public Library, which is a place where local residents can take shelter during times of unhealthy heat or wildfire smoke. 

Oakland, like much of California and other parts of the country, is facing increased risk of losing grid power during heat waves and wildfires, Hanlin said. Having backup electricity for the air-conditioning and ventilation systems to keep indoor air cool and clean is vital, but backup generators or batteries dedicated to providing emergency power are expensive solutions. 

Mobile generators are available, but in a lot of cases, especially large emergencies, it’s very hard to get generators and engineers out there to hook them up” where they’re needed, he said. Battery-electric and hydrogen fuel-cell buses, by contrast, can be deployed extremely quickly,” as long as buildings are equipped with bidirectional chargers and control systems that can move power from buses to buildings. 

They’re also much cleaner than diesel generators, which is important for communities like West Oakland that suffer disproportionate levels of air pollution from highway, port and railroad traffic, Hanlin noted. 

And unlike diesel generators, buses don’t just sit around waiting for emergencies — they’re providing a valuable service the rest of the time, moving people around. The ability to provide backup power could make these buses even more valuable to the transit agencies and school districts buying them, he noted. 

The tricky part is getting hold of the technology that can turn buses into a seamless backup power system, Hanlin said. Back in 2019, when the Center for Transportation and the Environment worked with the U.S. Department of Transportation to study the potential for what it terms bus exportable power supply” to provide emergency backup power, the technologies weren’t quite ready yet, he said. 

But those technologies are becoming commercially available today. There are off-the-shelf’ components we can utilize, particularly on the power electronics side, to drive costs down,” he said. Other partners on the V2B Oakland project include bus manufacturer New Flyer, electrical equipment maker Schneider Electric, charging-software provider The Mobility House and the city of Oakland. 

And there are a lot more battery and fuel-cell-powered transit buses and school buses on the road than there were a few years ago, he said. Many more are set to arrive in the years to come, thanks to billions of dollars in federal grants and state incentives, along with the increasing cost-competitiveness of electric vehicles compared to their fossil-fueled counterparts.

A growing number of these electric buses are being tapped for vehicle-to-grid (V2G) services, making their batteries available for grid support when they’re plugged in. School buses are a particular target for V2G since they spend most of their time parked. 

And more bus fleets are deploying solar power, on-site batteries and power electronics control systems at the depots where they charge, creating microgrids that can keep themselves running when the grid goes down and reduce their demands on the grid to lower recharging costs. 

But so far, electric buses haven’t been tapped to support buildings during outages — at least, not to the same extent as have passenger EVs, which are being tested for vehicle-to-home backup power during blackouts. 

In that sense, V2B Oakland is a groundbreaking project for bidirectional power,” said Jana Gerber, Schneider Electric’s president of microgrids for North America. This brings safe havens to the community when there are outages.” 

Prepping buses and buildings to interconnent for backup power 

Schneider Electric has been working on other types of mobile backup power concepts, Gerber noted. One example is its work with the nonprofit Footprint Project to bring mobile solar-plus-battery systems to disaster recovery sites. 

AlphaStruxure, a joint venture of Schneider and private equity firm Carlyle Group, is building a multimegawatt microgrid for charging transit buses in Montgomery County, Maryland, said John Ahrens, program director of Schneider Electric’s Microgrid Competency Center. It’s also building a microgrid at the Port of Long Beach in California featuring a mobile battery on a trailer that can be moved to where it’s needed, he said. 

But moving batteries is just the first step to designing a backup power system, Ahrens added. Along with a source of power, power conversion and management systems are needed to match bus electricity output to building power demand. Schneider Electric’s Energy Control Center, a power-management and industrial-controls platform that’s being used at the Maryland AlphaStruxure site and at the V2B Oakland project, can quickly adjust the power use of devices such as air-conditioner compressors and ventilation fans to make sure they don’t draw more power than the buses can provide, he said. 

For buildings or devices that use less power, bidirectional EV chargers can provide similar capabilities on their own, said Sarah Woogen, head of U.S. operations and analytics for The Mobility House. The German company, which makes software for managing EV chargers, is providing its technology for the V2B Oakland project, one of its first forays into building backup power, although not its first project involving V2G services. 

The project will use EV chargers from Rhombus Energy Systems that can convert the direct current coming from bus batteries or fuel cells to alternating current that mimics distribution grid power, allowing a smooth transition from grid power to backup power. 

Using EV chargers instead of dedicated control platforms like Schneider’s Energy Control Center could reduce the cost of making buildings ready for backup power, Woogen said. What’s more, the EV chargers can be used for their primary purpose most of the time, when the grid is up and running.

Mobility House’s ChargePilot software adds another layer of protection against grid outages because it can keep the system running even when the chargers can’t communicate with a central control system due to internet outages, said Greg Hintler, Mobility House’s U.S. managing director. 

The bus manufacturer New Flyer will be testing its vehicles as backup systems at its Bay Area facility before they’re deployed to West Oakland, Hintler said. It’s also adding ports that will allow its hydrogen-fueled buses to export fuel-cell-generated power, a first for the company, he said. 

All that testing will take some time, according to Hanlin of the Center for Transportation and the Environment. The bidirectional charger and facility upgrades at the West Oakland library are expected to be done by late 2023 or early 2024. New Flyer expects its first battery electric buses to be ready to deliver power by mid-2023; the first hydrogen fuel-cell buses will roll out by late 2024

Throughout the project, the nonprofit group has built in a lot of technology transfer into the work,” Hanlin said. That includes analyzing the market opportunities for New Flyer to make bus-exportable power an option for other fleets, and reaching out to transit agencies, school districts and emergency-management authorities to coordinate how they can put these mobile backup-power resources to use. 

A growing fleet of big batteries on wheels 

Vehicle-to-building backup power is a new frontier for electric bus operators. But as the technology to enable it matures, the growing fleets of electric or hydrogen-fueled buses on U.S. roads could become an important resource, said Sean Leach, director of technology and platform management for Massachusetts-based startup Highland Electric Fleets.

As part of its business model offering electric school bus fleets as a service, Highland has been selling power from batteries in parked buses back to the grid. So far, it’s had two summers of revenue-generating grid participation at its flagship deployment in Beverly, Massachusetts. 

But Highland is also looking at ways to make these buses more active members of the community” providing V2G and an array of other services, he said. If you have a long-duration outage, just keep sending the buses, and when they’re drained, send them back to an area that isn’t in an outage to fill back up.”

Nuvve, a San Diego–based company that’s operating vehicle-to-grid charging depots for school bus fleets in California, Colorado, Illinois and other states, is also using electric school buses for V2G, said CEO Greg Poilasne. I think the idea of dispatching some of them — maybe all of them — in the case of an emergency makes sense. This is something we’re definitely interested in.” 

Electric transit buses tend to have even larger batteries than school buses, to keep them running over their relatively longer duty cycles, Hanlin pointed out. Each New Flyer battery-electric bus involved in the V2B Oakland project is expected to be able to provide up to six hours of backup power to the library, and each hydrogen fuel-cell bus could provide up to 11 hours. 

The bigger the vehicle, the more backup power is available. Nuvve is a partner on another project funded by a California Energy Commission grant that will test the capability of heavy-duty EVs owned by the California Department of Transportation to supply backup power at a Caltrans facility in Oakland. Another CEC-funded project will test battery-electric farm tractors as backup power sources in California’s Central Valley.

Like the Oakland V2G project, the Caltrans project will reduce local air pollution as well as build resiliency against climate-change-induced extreme weather. Many low-income communities of color share streets and fence lines with the freight industry and suffer deadly pollution from petroleum combustion,” Brian Beveridge, co-executive director of the West Oakland Environmental Indicators Project, said in a Tuesday statement. 

AC Transit, the Oakland transit operator, had five battery-electric buses and 22 hydrogen fuel-cell buses in its fleet as of the start of 2021 and plans to have a total of 70 zero-emissions buses in its fleet by 2023, according to 2021 report. Each zero-emissions transit bus eliminates about 1,690 tons of CO2, 10 tons of nitrogen oxides and 350 pounds of diesel particulate matter over an average 12-year lifespan, according to the U.S. Department of Transportation.

Using these buses to eliminate the emissions from diesel backup generators eliminates another 100 pounds of carbon dioxide and about 2.5 pounds of nitrogen dioxide for every hour of backup operation at the West Oakland library, Mobility House’s Woogen said. Given that California is struggling to reduce its dependence on fossil-fueled backup power during the grid outages the state sometimes initiates to reduce wildfire risk, every bit of pollution reduction helps.

Jeff St. John is director of news and special projects at Canary Media.