Best Practices: How to build resilience into electric bus plans

May 31, 2022
Without energy resilience complementing electric fleets, transit agencies risk disrupting service continuity during adverse weather events.

The potential for positive impact from electrifying transportation is immense – 27 percent of global greenhouse gas emissions stem from this sector, according to the U.S. Environmental Protection Agency. With momentum in personal electric vehicle (EV) adoption and commercial fleet electrification at an all-time high, it’s no surprise that transit agencies across the country have also started to adopt electric buses. And many are actively engaging energy experts to define their transition plans.

While there is tremendous potential, one of the challenges transit agencies are consistently facing is how to incorporate energy resilience into their electrification plans. As climate and weather patterns continue to shift, transit agencies risk service continuity during adverse weather events that lead to power outages. Microgrids are a proven resiliency solution agencies should consider in offsetting this risk and save on costs compared to grid-sourced energy.

Microgrids ensure energy resilience for electrified transit

Microgrids, like those that Enel X builds, orchestrate multiple distributed energy resources and optimize them as one single resource of energy. Rooftop solar is a cost-effective solution to bring power generation close to the source of the demand. Combining this local generation with a battery electric storage system (BESS) and an appropriate control system can maximize self-consumption, as well as reduce demand charges from the local utility. The integrated electric buses, while drawing power from the system when charging, can complement the effectiveness of the microgrid by storing electricity produced – essentially acting as a mobile battery on wheels.

With the appropriate energy management system, buses are charged to meet their defined route requirements, as well as optimize their storage benefit for the microgrid. The optimization software and interconnection into the microgrid act to create a self-sustained system which, in the event of a power outage, has the capability to island from the grid to keep the microgrid energized and the facility and buses operational for a pre-defined period.

Steps transit agencies should take to plan for a resilient, electric bus fleet

The technical complexity, large stationary infrastructure components and moving electric vehicles in this type of project require careful planning to proactively design resilience into transit depots. Key considerations should include:

  • Initiate this process in parallel with facility design. This allows for the equipment to be sized appropriately and be incorporated into the design of the facility in the most logical and cost-effective way. Retrofits require additional planning.
  • Complete a cost-benefit analysis to evaluate sustainability versus resilience. On-site solar plus BESS for sustainability has different cost implications in comparison to adding islanding controls and a larger BESS for resilience. This requires modeling and scenario planning unique to the end-use customer.
  • Fully assess and utilize incentives to offset high up-front capital investment. Consider the infrastructure funding bill for microgrid investments and transport electrification as well as the likely extension of solar plus storage investment tax credit (ITC) as instruments for significant cost offset. Also, commercial agreements can generate revenue streams by bidding the microgrid and EV fleet capacities into wholesale markets and utility programs to further offset project cost.
  • Consider a holistic energy management service that includes electric buses. A turnkey solution streamlines project development and the optimization of the chargers, software, BESS, solar array, electricity and the electric buses.

Building resilience into electrified transit operations will reduce a transit agency’s carbon footprint in line with its sustainability goals, reduce energy costs and provide a continuous energy supply to maintain operations at times when the grid is strained or experiencing an outage. To design this resilient system, transit operators should look for a partner with an advanced transit modeling system that overlays microgrid analysis with emergency operations requirements. This enables agencies to create an electrified transit system that can island from the grid and operate with continuity when unexpected weather events occur.


Brianna Walsh is e-city director with Enel X.

About the Author

Brianna Walsh | e-city director, Enel X.

Brianna Walsh is e-city director with Enel X.