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La Plata Electric hopes to shave peak wholesale costs by tapping battery of electric bus

by Allen Best

An electric bus that will begin shuttling students to and from schools in Durango later this year will have its own homework to do.

The school bus will be integrated into the local electrical grid. Between runs, but especially at night, when renewable energy is generally most plentiful, it will be recharged. It can also be recharged during the middle of the day.

Then, when demand for electricity peaks, the batteries in the bus can deliver electricity to the grid, shaving the maximum cost to the local utility, La Plata Electric Association, a cooperative.

Bi-directional charging, also called vehicle-to-grid, remains rare in Colorado but will likely become more common in the next several years as electrical utilities work to smooth the humps of high demand with supplies of relatively inexpensive renewables. Storage will be crucial.

“This is a really cutting-edge project, not just for this area but for the whole state,” said Jessica Matlock, chief executive of La Plata Electric, which has 34,500 members, fifth most among Colorado’s 22 electrical co-ops.

“Vehicle-to-grid installations are the future because they enable our grid to operate with a higher degree of flexibility,” Matlock explained. “This will equate to big cost savings by allowing La Plata Electric to avoid the purchase of expensive on-peak power while aligning the charge of the bus with times of less expensive renewable generation.”

Bi-directional charging stations have recently been installed at a recreation center in Boulder and the Alliance Center in Denver, the latter the home to many of Colorado’s environmental groups. This is the first for a bus. Durango School District 9 expects to take possession of the 81-passenger bus from Blue Bird, the manufacturer, no later than October.

This is from the May 12, 2021, issue of Big Pivots, an e-journal. To sign up, go to

For electrical utilities that want to dramatically decarbonize their electrical supplies, bi-directional charging offers one tool among several to better match renewable energy supplies with demands. Many utilities are interested.

Dominic May

“This is a glimpse of the future,” says Dominic May, who wears the unconventional title of “energy resource program architect” at La Plata Electric. He predicts batteries of buses and other vehicles will be an important strategy for figuring out to how to add more renewables into the grid. “I think storage is the key to renewables.”

The single battery of an electric car can deliver enough electricity to power a house for a couple of days if some of the major uses, like running the clothes dryer, can be delayed. As such, electric vehicles may help utilities avoid catastrophes such as paralyzed Texas in mid-February when power generation from natural gas plants and renewables was disrupted.

The school district in Durango plans to use the electric bus on in-town routes, partly to give it higher exposure. Following the morning route, the battery will be depleted by about 40%, less in warm-weather months. It can be recharged to full capacity in two-and-a-half to three hours. Following the afternoon run, it can re-charge for about an hour again.

Then, beginning at about 5 p.m. and continuing to 9 p.m., the battery will be tapped to augment the electricity in Durango. Peak demand charges levied by Tri-State Generation & Transmission, the wholesale supplier, predictably fall sometime in that window. That’s when demand for electricity by its member cooperatives in Colorado and adjoining states peaks.

As demand drops, the battery will be recharged. During the dark of night, when the wind tends to blow on the Great Plains, electricity prices typically plummet. Prices can also decline sharply during sunshine-splashed mid-days when solar panels generate maximum output.

Rates set by La Plata for direct current fast chargers, such as for cars or this bus, strongly encourage off-peak charging. Electricity drawn from the grid during off-peak times is 6.2 cents per kilowatt-hour; it’s almost four times higher during peak periods, 26 cents.

La Plata did its homework before donating $150,000. This will cover the $60,000 cost of the vehicle-to-grid fast charger, and help defray the $384,000 cost of the bus. A service upgrade will also be covered. The total projected cost is $450,000.

May says the cooperative expects to recoup its cost within 5 to 8 years because of the savings it will yield from lower energy costs charged by Tri-State.

Eventually a game changer

This is just the start. La Plata expects to use this first bus as a learning experience. Ultimately, says May, the cooperative expects to see more electric buses but also electric cars along with bi-directional chargers at home.

“In the long term, I think this will be a game changer,” he says. “The increase in renewables begets the storage question.”

Natural gas-burning peaker plants, can deliver electricity to meet peak demands, going on line in just minutes. However, they emit carbon dioxide and, in the supply line, methane, another and even more powerful greenhouse gas. Like many utilities, La Plata has pledged to decarbonize. Hydroelectric supplies don’t work well except in the limited case of pumped-storage hydro.

Vehicle-to-grid charging offers a “very obvious way to use both sides of the battery,” says May.

Holy Cross Energy, another electrical cooperative that serves the Vail-Aspen-Rifle area in Colorado, also expects to make use of bidirectional charging.

In the area of Basalt, a town served by Holy Cross, buses are parked 91% of the time, and most of the time they are parked near places with strong electrical infrastructure, says Chris Bilby, research and programs engineer for Holy Cross.

“It seems like a win for everyone.”

Aspen Country Day, a private school in the Holy Cross service territory, will begin using two electric buses this fall, but Holy Cross has no plans to tap their batteries as La Plata is doing in Durango.

Holy Cross instead plans to partner with the National Renewable Energy Laboratory to study the benefits to a microgrid of using mobile storage. The project is called ReORG and also includes a project in North Carolina.

Lack of common standards

Lack of standardization of bi-directional chargers holds Holy Cross back. In the case of the two-directional chargers installed in Denver and Boulder, only the Nissan Leaf is equipped with bi-directional charging capacities. In Durango, the bi-directional charger created by a company called Nuvve will work —at least for the time-being — only with the Blue Bird e-bus.

These chargers are extremely expensive and, given the absence of common standards, have limited pairings. In other words, the vehicles and the charging equipment have to “shake hands,” explains Bilby. Such hand-shaking will come in time, but not imminently.

Chris Bilby

“I think it’s coming, but we don’t have anything in the pipeline yet,” he says. For now, he says, the technology has advanced faster than adoption of standards. The International Organization for Standards (ISO) will set standards for this vehicle-to-grid technology, called V2G.

Several school districts across the country have embraced e-buses. One notable example is Virginia, where Dominion Energy has partnered with school districts to deliver 50 buses. The batteries of the buses can be tapped by Dominion, the electrical utility, to improve grid resiliency. School buses using vehicle-to-grid have also been put into service in California.

For a good overview of electric school bus fleets, the breakthroughs and challenges as of November 2020, see Green Tech Media story.

Bilby has studied the routes of the 250 to 300 school buses used in the Holy Cross service territory. In Aspen, the routes are compact, a maximum of 35 miles. In more rural areas, the routes can be up to 80 miles long.

In envisioning this future of vehicle-to-grid charging with school buses, Bilby also points to another twist. Often, the bus drivers are also teachers. This means that charging must also consider where the bus gets parked for the night, perhaps at the end of a road.

The closer frontier

For now, Holy Cross is exploring a more limited frontier. At Basalt Vista, a cutting-edge project that debuted in 2019 in the eponymously named town, cars can interface with house batteries. As such, the house can draw on the car battery for electricity.

In 2020, Holy Cross began expanding this concept in its Power + program. The concept is largely the same as the school bus batteries except that the Tesla Powerwall 2 batteries are stationary, attached to the houses or other buildings.

Members of Holy Cross—in cooperatives, customers are also owners of the utility—can store energy directly from the grid or energy generated from on-site solar. The batteries can provide backup power for the home. But the agreement with participating members is that Holy Cross can also tap the batteries, but always leaving at least 20% of capacity.

One benefit to Holy Cross is the greater ability to address loss of power supplies caused by wildfires or some other disruptions.

Holy Cross pays for installation costs of the batteries. Members have 10 years to pay back cost of the batteries.

In time, the program could be expanded to car or other vehicle batteries.

“This could be a huge win, not just for coops but for all the utilities,” says Bilby. “I think we all know that. But we’re just waiting.”

Allen Best
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