Buses are Big Backup Batteries

May 17, 2018

Electric buses a good idea for climate and electric grid.
China ahead as is usual lately.


We often think of electricity as a one-way transaction. Need to toast a bagel, wash the sheets, or charge your phone? Your fuse box sends you the juice you need. Electric vehicles, though, have the capacity to send power back to the electrical grid using vehicle-to-grid (V2G) technology—and that’s good news for an aging grid already operating at full capacity.

Vehicle-to-grid does this by letting electric vehicle (EV) batteries switch between providing and consuming energy on an as-needed basis. As EV adoption rates steadily climb, this technology could help stabilize the electrical grid, lessen the need for new power plants, and reduce kids’ exposure to cancer-causing exhaust. Essentially, electric vehicles can be like a backup battery for your phone, but for the entire US power grid.


“You’re looking for a vehicle that’s plugged in a decent amount of hours each day,” Marc Trahand, chief operating officer of San Diego-based V2G startup Nuvve, told me on the phone. The bigger the battery, the bigger the potential to help the electrical grid and the people using it.

Enter school buses. There are approximately 500,000 buses in the US alone, and the majority of them are basically rolling cancer machines due to their diesel engines. in 2012, the World Health Organization said diesel exhaust can definitely cause lung cancer, and might also be associated with an increased risk of bladder cancer. Meanwhile, according to the American School Bus Council, the US’s school buses consume a combined $3.2 billion worth of diesel a year.

Lance Noel, a postdoctoral V2G researcher at the Center for Energy Technologies at Aarhus University in Denmark, said school buses are not only ripe for electrification, but also V2G technology because they’re only in use for a few hours at a time. “It’s a giant battery sitting in a parking lot for at least 18 hours a day,” he told me on the phone.

Using a bidirectional charger—that is, one that is able to charge and discharge power on command dynamically using smart software—these batteries can supplement the grid in peak-demand times, and act as storage when demand is low.

The technology was created by a professor and co-founder of Nuvve, Willett Kempton, who has been working on V2G at the University of Delaware since 1996. Today Nuvve, which wants to be the intermediary between EV owners and grids, is working with automakers such as Nissan and Mitsubishi to integrate bidirectionality into batteries and chargers.

The Japanese automakers’ interest was partly piqued by the 2011 Fukushima nuclear disaster that resulted in blackouts, according to Trahand. “They realized, ‘We have all these electric cars with quite a big capacity,’” he said, adding that a Nissan Leaf could probably light up 10 houses for an evening, or a single house for far longer.

At its core, V2G advocates for the democratization of energy markets by allowing small-time players to use their vehicles to provide electricity—either to the grid, to their neighbors, or to their own homes—and potentially earn a little bit of revenue while doing so. According to PJM Interconnection, a grid operator and wholesale electricity market in the eastern half of the US, V2G tests done with electric BMW Minis earned each car user about $100 a month. Electric-vehicle owners in the US who drive 15,000 miles a year and charge exclusively at home can expect to pay $540/year in electricity costs, according to Plug In America.

Single EVs can’t participate in this market on their own because they don’t produce enough power; they’d have to be aggregated with other vehicles to participate in the market. This is why fleets are especially attractive for V2G technology. School buses are a particularly interesting fleet to work with, not only because of their V2G capability and revenue-generating potential, but also because of their primary clientele: kids.

In the US, 25 million children collectively ride 62 billion miles a year in school buses. Many of these use diesel engines, which again have been shown to cause cancer. Kids of color and children from low-income households in particular are more likely to take transit or the school bus. Research published in the American Journal of Respiratory and Critical Care Medicine showed that diesel pollution is far worse inside of bus cabins than in the air around the vehicle. That same research shows that cleaner fuel policies positively impact children’s health.

While a grid that still largely depends on coal isn’t an ideal power source for any electric vehicle, V2G’s storage capabilities could actually help promote renewable energy like solar and wind—the output of which fluctuates depending on time of day and weather conditions—by offering unique energy storage solutions that are lacking on the existing grid.


The yellow diesel-powered school bus has shuttled generations of kids to and from school. But now some school districts are trying out electric, battery-powered buses, and you may see them on roads in our region in the not-too-distant future.

There are thousands of school buses in Virginia, Maryland and D.C., and pretty much all of them run on diesel.

“Inhaling diesel exhaust can cause respiratory diseases and worsen existing conditions,” says Matt Casale, with the United States Public Interest Research Group, which recently published a report urging school districts to ditch diesel. While diesel technology has improved in recent years, with new buses emitting far less, Casale says the exhaust is still dangerous for children. Kids, he says, are especially vulnerable because their lungs are still developing, and because they breathe more air per pound of body weight than adults.

“For kids there is no established safe level of exposure to diesel exhaust pollutants,” he says. Exposure to diesel exhaust can cause asthma or exacerbate it, and according to the EPA, it may cause cancer.

Electric buses have gotten a lot cheaper in recent years, with a dramatic decline in the cost of batteries. This year, school bus manufacturer Blue Bird is rolling out its first electric model, Thomas is making one that will come out in 2019. They’re still more expensive up-front, compared to diesel buses. According to the U.S. PIRG report, electric buses cost about twice as much ($230,000 compared to $110,000, including charging infrastructure), but over the lifetime of the bus they can save as much as $31,000 on fuel and maintenance.


Back in 1980, Shenzhen was just a modest fishing village of 30,000. Now a megalopolis of some 12 million, the city has undergone a remarkably rapid transformation—and so has its transit fleet. In an effort to control air pollution in this vast industrial region, the city began introducing electric buses in 2009. It has now become the first city to electrify 100 percent of its public buses. That’s a staggering 16,359 battery-powered vehicles, the world’s largest eco-friendly bus fleet.

Globally, there are an estimated 385,000 fully electric buses, and according to a recent Bloomberg New Energy Finance report, 99 percent of them are in China. As Shenzhen moves on to making all its taxis go electric as well, other Chinese cities are beginning to follow suit, replacing their gas-powered bus fleets by the hundreds.

Shenzhen is one of only a few cities in China to dramatically reduce its air pollution, and the government attributes much of this progress to bus electrification. It’s a strategy cities elsewhere are hoping to emulate, albeit at a much slower pace: London plans to go all-electric by 2030, while New York City is currently piloting five electric buses, with the aim to transition by 2040. Washington, D.C., just added 14 electric buses from the California-based company Proterra to the city’s circulator fleet.

4 Responses to “Buses are Big Backup Batteries”

  1. rhymeswithgoalie Says:

    The grade school near my home has this sign posted:


    I feel insufferably smug when I drive my Leaf past it.

  2. rhymeswithgoalie Says:

  3. MorinMoss Says:

    “New York City is currently piloting five electric buses, with the aim to transition by 2040”

    How embarrassing.
    BYD Europe’s managing director Isbrand Ho claims that everyone had a good laugh at the latest Chinese toy when they showed off their new model at an industry event in 2011.

    Chinese EV bus production numbers since: https://ibb.co/iKsgko
    In case the graphic doesn’t embed, it was a few thousand in 2011 and about 135000 in 2016, all but 10k of which were BEVs, the rest hybrid.

    Shenzhen region which borders Hong Kong now have a fleet of 12000 BEV buses and will mothball the few hundred remaining diesel dinosaurs by end of year.

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