CAR teams with COTA to predict electric bus range
When you think about public bus transportation, you likely think about where to get on, where to get off, and how much time it will take you to get from point A to point B. What you probably don’t think about is if the bus has enough fuel, if another bus is ready to go if the one you’re on breaks down, or the multitude of other details that need to be taken into account for your ride to go smoothly.
Until recently, these details were simple to handle because busses were powered by readily available fuels and have been for years, so the logistics were in place. But with new technologies that are enabling transit agencies like the Central Ohio Transit Authority (COTA) to incorporate electric busses into their fleet, a significant amount of planning, research and testing is being required for these scenarios to run smoothly.
For passenger vehicles, one of the major concerns with electric busses is range anxiety, which is consumer fear that busses don’t have enough battery power to go the distance they need to. Unlike traditional gas-powered busses, which require only a few minutes to refuel, and can be done conveniently, electric busses can take hours to charge and there may not be a charging station nearby. These factors can impact which routes electric busses can be deployed to.
COTA came to the Center for Automotive Research (CAR) with the question, “How do we work with and predict electric range of busses in a wide variety of operating conditions?”
“Leveraging information provided by COTA such as bus routes, passenger demands, and historic data on weather and traffic conditions, CAR is developing prediction tools that use basic measurements collected on buses during service to forecast the energy consumed and the available range of the battery pack,” said Mechanical Engineering Professor, Marcello Canova. “This information is critical to COTA, as well as all transit agencies, for making important decisions on how to best allocate electric buses on their services and route options.”
Factors that impact battery life include weather, number of passengers, driver aggressiveness, traffic, and health and age of the battery pack.
“The idea of the project is to come up with predictive models,” said CAR’s Senior Associate Director David Cooke. “Commonly in research projects, we have tons of information and data, and we have the capability to run experimental tests with our facilities at CAR, but in this case, we are looking to maximize the prediction capabilities with limited amounts of data.”
A combination of modeling and simulation along with physical testing is being used to make these predictions, which can then be used for multiple busses in the future.
“Because we have access to the heavy-duty chassis dynamometer at CAR, we have the ability of designing and running some tests to understand the bus energy usage,” said Stephanie Stockar, assistant professor in the Department of Mechanical and Aerospace Engineering. “However, extensive testing is very time consuming and requires an electric bus to be taken off service. In addition, it might not provide a full picture of the bus operation as we would not be able to fully reproduce what happens on the road (temperature, road conditions, passenger loads). Instead, we are using a combination of physics-based models and data-driven methods to extract as much information as possible by fusing basic measurements collected on-road and data collected through targeted and controlled testing.”
CAR has worked frequently with medium and heavy-duty vehicles as part of its commercial testing program as well as the FTA LoNo program, but this is one of the first opportunities to work on-site with full battery electric busses. “COTA is getting electric busses on routes and in their daily operations,” said Cooke. “We are helping them think through and understand what reasonable expectations are over different conditions. It’s an exciting opportunity to partner with COTA on this project.”