Jan 10, 2020

Electric school buses are batteries for the grid

Illustration: Sarah Grillo/Axios

Utility companies are helping cash-strapped school districts replace diesel buses with electric ones that have a secondary purpose: helping to manage electricity demand.

Why it matters: Electric buses are cleaner, but cost about three times more. Using them for energy storage can help close that cost gap and smooth out energy demand on the electric grid.

What's happening: Less than 1% of America's 480,000 school buses are electric today, but that's beginning to change.

  • Communities in California, Massachusetts and a few other states are testing electric school buses and charging infrastructure (in some cases, tapping funds disbursed from Volkswagen's diesel emissions settlement with the U.S. government).
  • Vehicle-to-grid (V2G) technology for school buses is still fairly new.
  • Michigan-based DTE Energy, for example, has a pilot with six buses in two school districts. It is testing charging infrastructure as well as V2G.

The most ambitious V2G effort comes from Dominion Energy, which is planning to deploy 1,050 electric school buses in Virginia over the next five years.

  • Dominion just ordered its first 50 electric buses from Thomas Built Buses, a division of Daimler Trucks North America.
  • The batteries and related EV technology are supplied by Proterra, a leading supplier of electric transit buses. The powertrain includes 220 kWh of total energy capacity and provides a 134-mile driving range — more than enough to deliver kids to and from school each day.
  • The buses can charge in about three hours with Proterra's 60kW DC fast-charging system.

Virginia school districts could save $700 per month — $8,400 per year — per bus in operating costs, says Mark Webb, Dominion's senior vice president and chief innovation officer.

  • "The hurdle is the upfront capital cost for the school district," which could take 15 years to recoup, even with lower operating costs, he said.
  • "We can step in and fill that void and they can capture the future benefits for the same upfront cost."

How it works: V2G technology is not a new concept, but the economics have been challenging.

  • V2G enables electric vehicles to store surplus energy from intermittent wind or solar sources during non-peak periods and feed power back to the grid when needed.
  • The problem is that passenger cars tend to move around, and their relatively small batteries can discharge only a small amount of electricity at a time.

A fleet of school buses is a better source of distributed power because their usage patterns are predictable.

  • They are idle at precisely the times when energy demand is at its peak — midday and during the hottest summer months.
  • By storing or drawing power from a fleet of parked school buses, utilities can avoid wasting surplus energy from renewables or cranking up a natural gas power plant, for example.

The bottom line: With 480,000 school buses on the roads, the impact could be huge, Ryan Popple, founder and CEO of Proterra, tells Axios. "If you fully electrify the school bus fleet, you're offsetting a couple of nuclear power plants."

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