Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley have analyzed the cost, energy, and environmental implications of a fleet of self-driving electric vehicles operating in Manhattan.

Using models they built and data from more than 10 million taxi trips in New York City, they found that the cost of service provided by a fleet of shared automated electric vehicles (SAEVs) would be $0.29-$0.61 per revenue mile—an order of magnitude lower than the cost of service of present-day Manhattan taxis and $0.05–$0.08/mi lower than that of an automated fleet composed of any currently available hybrid or internal combustion engine vehicle (ICEV).

Required fleet size by battery range and charging network. Lines represent exponential fits for simulation results, which were collected at 10-mile intervals in the battery range. The minimum fleet size falls to 6,470 vehicles at battery ranges of 70 miles and greater. Credit: ACS, Bauer et al. Click to enlarge.

They estimated that SAEV costs would be lowest with a battery range of 50–90 miles, with either 66 chargers per square mile, rated at 11 kW or 44 chargers per square mile, rated at 22 kW. This finding highlights that currently available EV ranges would more than suffice, and that significant cost savings could result from reducing battery range from current levels.

The EV industry is focusing on the personal car market, trying to make the range as large as possible. The standard now is 200 miles. We suspected you wouldn’t need as much for taxis. We found plenty of times during the day when a portion of taxis could slip off to recharge, even if just for a few minutes. This greatly reduces the need to have a big battery and therefore drives down cost. It is dependent on having a fairly dense charging network.

—Jeffery Greenblatt, Berkeley Lab co-author

They further estimated that such an SAEV fleet drawing power from the current NYC power grid would reduce GHG emissions by 73% and energy consumption by 58% compared to an automated fleet of ICEVs. Their study is published in the ACS journal Environmental Science & Technology.

The researchers developed an agent-based model to simulate the movement of 7,000 taxis around Manhattan throughout the day. They also built models to analyze the cost of service and optimal placement of vehicle chargers.

Berkeley Lab and UC Berkeley researchers developed a model to analyze taxi trips provided by shared automated electric vehicles in Manhattan; blue represents an empty vehicle, green is charging, and red is occupied. Click to enlarge.

To put that density into perspective, Manhattan currently has about 500 chargers for public use, including Tesla chargers, said corresponding author Gordon Bauer of UC Berkeley’s Energy and Resources Group. “We found that we would need to at least triple that capacity,” Bauer said.

Greenblatt pointed out that there are still many barriers to the wider penetration of personal EV ownership, including high cost and limited range. However, by switching to a shared fleet that’s automated, electric service can be provided to people essentially now, he said.

He noted that shared vehicles are best suited for dense, urban environments.

The study was supported by DOE’s Vehicle Technologies Office (VTO) as part of its SMART Mobility Lab Consortium, managed by VTO’s Energy Efficient Mobility Systems Program.

Resources

• Gordon S. Bauer, Jeffery B. Greenblatt, and Brian F. Gerke (2018) “Cost, Energy, and Environmental Impact of Automated Electric Taxi Fleets in Manhattan” Environmental Science & Technology doi: 10.1021/acs.est.7b04732