Navigating the Path to an Electric Bus Fleet

As the Department of Transportation's Federal Transit Agency (FTA) continues to invest in clean transportation technologies, the Center for Electromechanics (CEM) is playing an integral role in helping determine the future of transit buses. The ultimate goal is a highly efficient, zero-emission bus that is not only good for the environment and improves the nation's energy security, but also allows transit agencies to operate smoothly and more cost effectively.

H2 Bus

The path toward this goal resides in the electric bus. A bus powered by electricity has zero-emissions (at the source) and can be up to five times more efficient than traditional fossil fuel buses. However, current battery electric buses struggle to match the range of a diesel bus, and manufacturers offer several solutions, where battery chemistries, traction motors, and recharging facilities can differ from one vendor to the next. Often times, determining the best solution for the transit agency can be cumbersome and loaded with uncertainties.

The Center for Electromechanics (CEM) has partnered with the Center for Transportation and the Environment (CTE) to develop an analytical approach to evaluating the performance of an electric bus prior to procurement and deployment. This approach centers on CEM's expertise in power systems modeling. In this case, CEM builds dynamic computer models of the electric bus and simulates their performance using GPS data collected on routes determined by the transit agency. In these analyses, worst case and nominal duty cycles are defined, allowing the team to estimate overall energy consumption. The estimated energy consumption is then paired with electric utility rate models, which are determined by consulting local electric utility providers to determine the optimal charging rate model based on time of use, peak demand, and route scheduling. Often times, the optimal rate model will vary for each vendor's bus and charging scheme. The final step of the evaluation process includes an assessment of the overall life cycle cost, which includes energy consumption, as well as maintenance and periodic battery replacement.

Using this approach, the team is able to effectively predict the performance and life cycle cost of an electric bus prior to procurement and deployment; thereby allowing transit agencies to make informed and educated decisions when implementing an electric bus fleet and determining any necessary route or service modifications. Thus, the transit agency can avoid pitfalls and deploy an electric bus fleet that is setup for success!

bus energy graph

For more information please contact:
Mike Lewis

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