Dominion Energy has selected Thomas Built Buses, equipped with Proterra internals, for the 50 buses sought in a $13.5 million September 2019 request for proposal. The vehicles will be purchased through local bus company Sunny Merryman and deployed by the end of 2020. A second round of 1,005 buses is expected to be deployed by 2025.
The specific model being purchased is the Saf-T-Liner C2 Jouley, which is the electric version of the big yellow bus that most of us have come to know. The unit’s two speed transmission offers 295 peak horsepower over its 134-mile operating range, and 0-60mph in a whopping 49 seconds.
The Thomas Built Buses will utilize Proterra’s powertrain, Proterra’s battery and a Proterra 60kW bi-directional DC charger. The units feature a liquid cooled 220 kWh battery system that is partially charged by regenerative braking. Proterra offers over-the-air battery management software updates, and a power-save/economy mode to extend range when required.
A Dominion press release states that the selection criteria focused on battery and vehicle-to-grid (V2G) features and specifications, price, warranty, customer support, supplier footprint, supplier diversity and safety. The bus is charged using the standard SAE J1772 charging protocol and offers a bilateral V2G capability. The Proterra website suggests that a single bus can be recharged in less than 3 hours with the 60-kW hardware, with the hardware expandable to 4 buses that could be recharged over a 12-hour period.
An NREL analysis found, shown in the image to the left, that an average school bus route distance was just over 31 miles, and the daily distance traveled was 73 miles in a day, with a 99.7% cutoff on driving distance of 154 miles for the whole of the day. As well, the large majority of buses were on the road for fewer than 4 hours, and 99.7% for six hours or less.
A separate study suggests that in California, the state’s electric vehicle push by 2025 would generate a need for around 100,000 additional vehicle chargers, and could push the evening electrical peak higher by 1 GW of demand if these vehicles weren’t responsibly charged.
As part of the state’s broader push toward 100% clean energy (not just electricity), regulators have recently approved an SDG&E proposal to install 3,000 to 6,000 medium and heavy vehicle charging stations, as well as a V2G pilot where 10 school buses will be tested for use as grid assets.
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