New York City tests a solar-powered electric-school-bus microgrid

New York City utility Con Edison will need to be able to charge about 10,000 electric school buses on its constrained power grid within the next 10 years or so. A $9 million pilot project in Brooklyn could help it figure out how to do that.

The project is starting small. Four battery-electric school buses are onsite today, with 12 more expected by the start of next school year. They’ll be bolstered by a 500-kilowatt solar array and a 2-megawatt-hour battery onsite, as well as by solar panels on some of the buses themselves.

But Con Edison hopes that these combinations of onsite clean power and smart charging will help keep grid stresses and costs in check at EV-charging depots across New York City and environs.

All the assets at the site in eastern Brooklyn — buses, solar panels, and batteries — can modulate when they pull power from the grid, as well as send power back to the grid when the utility needs it.

“We really think what we’re learning with these buses is something we can scale up, not just with school buses but with any fleet in our territory,” Roy Rada, Con Edison’s manager of EV demonstration projects, told Canary Media. ​“We think school buses are a first mover.”

Electric school buses are an ideal target for so-called vehicle-to-grid (V2G) services, Rada explained. On top of the health benefits they bring by replacing diesel-fueled buses that spew harmful exhaust, school buses operate on set daily schedules and spend most hours of the day — especially in the summer — parked and plugged in.

That means bus operators can pick and choose when to charge the buses to avoid stressing out Con Edison’s grid. They can also opt to discharge extra power stored in the buses’ batteries during hot summer evening hours, when New York City electricity demand tends to peak. Similar electric-bus V2G projects are being launched in multiple states, including California, Colorado, Illinois, Maryland, and Massachusetts.

Con Edison forecasts that grid demand from electric buses, trucks, and other commercial vehicles will add up to more than 100 megawatts by 2030, Rada said. Being able to control when those vehicles charge, or tap their spare capacity to relieve grid stresses, could be quite valuable.

Beyond systemwide impacts, individual charging depots can add up to megawatts of new electric load concentrated in discrete pockets of an already congested urban grid.

In fact, local grid congestion initially led First Student, the school transportation services provider that operates the depot, to start searching for onsite power resources that could supplant Con Edison’s grid supplies, said Kevin Matthews, First Student’s head of electrification.

“We’re looking at a depot that has its own challenges, and Con Ed has its own challenges getting electricity to us,” he said. With the new pilot project, ​“we’ve figured out a way to resolve that.”

Solar and batteries at the site were an obvious first step, Matthews said. A growing number of EV charging depots are installing solar and batteries to reduce their demand on the power grid.

First Student is adding a novel twist — solar panels on top of the school buses themselves. At 4 kilowatts of capacity per bus on six of its buses, those panels won’t provide that much of a boost, Matthews said. Still, they represent an interesting experiment in how to deliver extra solar power not just to bus batteries but — through the bidirectional chargers — to the larger depot battery and solar system, he noted.

All these systems will be integrated with Con Edison’s grid operations via software, he said. First Student and the utility haven’t yet picked which combination of software they’ll use to manage the interplay of onsite charging with grid needs, although several companies provide that kind of capability.

Adding up the benefits for utilities and EV fleet operators

All those technologies do add costs compared with simply plugging into Con Edison’s grid. But as the number of electric school buses grows from a few dozen today to thousands in the coming decade, these kinds of electric-bus-backed microgrids will become increasingly cost-effective, he said.

First Student, which is working with dozens of school districts across the country that have received federal electric-school-bus grants and rebates, is using other techniques to cut the cost of EV-charging deployments, Matthews noted. One example is the ​“trenchless” system it used at its Brooklyn site, which encases power conduits in hardened aboveground structures to avoid digging trenches in concrete and asphalt.

That approach, which First Student developed and which has been mirrored by other companies, reduces construction expenses by about 30 percent compared with a trenched deployment, he said. It also allows the company to reconfigure its power cabling layout in the future at much lower expense.

Utilities and EV-fleet-charging developers are equally eager to find ways to bring down the cost of integrating electric vehicles into their grids. Already, the fast-growing demand for charging power is overwhelming available grid capacity in California, which has the country’s most aggressive vehicle-electrification mandates. Similar issues are cropping up in New York City.

New York state is not too far behind California in its EV ambitions, with school buses a particular target. State law requires all school buses sold in New York to be zero-emissions by 2027 and calls for a complete conversion to zero-emissions school buses by 2035, Rada noted.

Con Edison offers incentives to reduce the cost of connecting medium- and heavy-duty EV-charging sites to the grid through a pilot program that’s expected to expand into a full-scale program in the coming years, Rada said. It also offers special charging rates to customers who charge during times when grid demand is low and avoid charging when it’s high.

But the sheer scale of the EV-charging load coming onto Con Edison’s grid will take a variety of strategies to manage, he said. ​“Today there are only like 20 electric school buses out there,” he said. But that number will eventually grow to encompass all the roughly 10,000 school buses in its service territory.

Matthews highlighted the potential for both utilities and EV-fleet operators to save money through these kinds of projects. A significant portion of the costs that utilities incur on their grids results from upgrading them to deliver power during the relatively rare number of hours per year when electricity demand peaks. Utilities pass on those upgrade costs to their customers at large.

If investing in solar, batteries, smart EV charging, and microgrid controls can reduce the need for some of those grid upgrades, that could be a win not just for EV-charging depots but for utility customers as a whole, Matthews said. The primary goal of this pilot project is to determine ​“what avoided cost the utility will have on the customer side of the microgrid,” he said, ​“and what avoided cost the fleet operator will have by being able to assist the utility.”