Zero-emissions bus (ZEB) technology is playing a substantial role in the United States’ vision to decarbonize the transportation sector by 2050, but restructuring a bus network requires more than just replacing a diesel tank with a battery pack. A transit agency in Los Angeles will have an entirely different transition plan for an electrified fleet versus one in Chicago or Toronto.
To address these challenges, STV developed the Performance and Evaluation of Electric Bus Routes (PEER) analysis tool, our in-house software that analyzes an agency’s bus network in a battery electric bus (BEB) environment.
PEER acts as an energy consumption modeling and data analysis tool, where we can quantify an agency’s vehicles, maintenance facilities or depots, operating schedule and enterprise on a holistic level. It can simulate everything an agency’s buses do in a day—all its routes, schedules and stops, as well as all vehicles within its fleet and any environmental impact from weather changes to elevation, and more.
When working with clients looking to invest in a zero-emissions infrastructure, our team recommends first conducting a PEER analysis to better inform a program’s direction. Other energy consumption metrics that are regularly used by agencies or consultants are empirical tests like Altoona or pilot programs with a small amount of ZEB vehicles. They both can provide a good benchmark estimate of how much energy a vehicle might take to complete a certain route or select number of miles.
PEER’s analysis, though, is more complex.
PEER simulates electric vehicles within an agency’s entire context, looking at a bus’s exact location along its route, as well as temperature changes, route elevations, passenger loading and more. Designed as a physics-based model, PEER is capable of custom simulations fed by numerous inputs from an agency and STV, which are then delivered into agency-specific results.
Our insights run the gamut, including route and block energy consumption, bus scheduling, fleet transition, technology comparisons like BEBs versus hydrogen fuel cell electric buses (FCEB), energy costs and charging infrastructure requirements.
PEER can replicate a bus’s path with second-by-second accuracy, plotting energy consumption to determine how long a battery can power a bus on its daily route before needing to recharge. It can even determine the additional energy needed to fuel the HVAC systems that heat the buses in the winter, auxiliary loads to open doors and light the vehicle, or how extreme heat impacts battery charging.
Recently, the Northeastern U.S. experienced a major heat wave, prompting New York City to activate its heat emergency plan. With increasing temperatures causing planned blackouts or load shedding, a transit agency needs to consider how to charge their buses during these periods. PEER accounts for typical load shedding, which occurs within the afternoon to early evening utility demand charge window. STV recently completed PEER analysis for a transit agency to see how that affects its potential BEB fleet, where we were able to predict that even by eliminating bus charging during that demand charge window, an entire bus schedule could still be completed.
Another insight we can provide through PEER is whether an agency chooses battery electric or hydrogen fuel cell vehicles, also known as fuel-cell emissions buses (FCEBs). Transforming a fossil fuel bus network into a zero-emissions network—whether it’s operating battery-powered or hydrogen-powered vehicles—is a massive endeavor for agencies.
PEER allows them to select the best path forward so that they can accurately plan capital. It simulates this BEBs versus FCEBs comparison, revealing what an agency’s zero-emissions fleet could be like with either technology, as well as the benefits of a mixed fleet of BEBs and FCEBs. Fuel cells can be refueled within 40 minutes, whereas batteries take much longer. PEER can also evaluate degradation. Battery capacity declines over time, but, while you can continue to refill a tank with hydrogen, a fuel cell’s efficiency decreases as it converts hydrogen to electricity.
Once PEER outputs its unique analysis for an agency, STV’s vehicle experts deliver a final report to clients that provides them with a comprehensive path forward to restructure their fleet procurements and their bus schedules. We have validated the tool across real-world data, from hundreds of trips across multiple agencies in various geographical locations.
PEER unmasks the unknowns of a bus network’s lifecycle, helping an agency understand what it will be like if they continue to run on diesel, or switch to BEBs, FCEBs, or even BEBs with a diesel heater. We’re helping agencies future-proof their fleets for the next 10 to 30 years, and we see PEER as the best tool to help them plan for the future.
