Analysis of Zero-Emissions Options Leads to Detailed Plan for Electric Buses

The San Mateo County Transit District has an aggressive plan to achieve a zero-emissions bus fleet ahead of a California mandate for 2040. To meet this goal, the agency is planning on a rapid transition of more than 300 diesel bus fleet to zero-emissions, battery-electric buses. HDR is supporting the agency in its transition process which includes on-site support services such as program management, task management, and assistance with the development of the master plan that will guide infrastructure and vehicle implementation for the next 20 years. 

The Analysis

From the ground up, HDR has created a tool called the Zero+ Fleet Optimization that was used to conduct a detailed analysis on the SamTrans routes and fleet that allowed the team to understand the following: 

• Minimum, maximum and average amounts of energy required to power a battery electric bus fleet. 
• Estimated electrical power demand of the SamTrans fleet, hour-by-hour, 24/7, for each bus depot. 
• The effect of temperature and HVAC system on range energy consumption. 
• Battery depletion in the event of severe traffic congestion. 
• Estimated range losses due to battery aging/deterioration and timing. 
• Best operational, maintenance and charging methods to minimize peak load and demand.

HDR has helped analyze and identify a preferred charging approach that uses a managed charging system to peak energy demand from 29 megawatts down to 9 megawatts. With managed charging, up to three buses are assigned to a single charger, with each bus charging consecutively and prioritized based upon battery level and departure times. Using current utility rates, this could save nearly $350,000 a month in electric demand charges. The Zero+ Fleet Optimization model showed that prioritizing charging identified a significant reduction in fuel cost while maintaining the required bus availability for each depot. 

HDR also analyzed smart energy management tools and software to balance and adapt peak loads to time-of-use rate schedules. The strategic plan as provided by HDR would combine infrastructure development, smart energy applications and solar panels to provide lifelong energy cost savings to SamTrans and further support its sustainability goals.  

Innovative Clean Transit Plan

The Innovative Clean Transit Plan is the key document that will guide SamTrans toward its transition to zero-emissions buses. Our team worked alongside SamTrans staff to develop the Plan to identify a bus procurement schedule, infrastructure needs, staff training, and a high-level implementation strategy for how this should occur. The Plan includes a strategy for prioritizing Communities of Concern within the ZEB rollout, ensuring the process takes equity and community needs into account. This document also serves to satisfy the State of California’s requirement for ZEB planning, describing how SamTrans intends to exceed the goals outlined by the state, and ensuring that SamTrans is a regional leader in the implementation of ZEM technology.

What’s Next

The HDR team will continue to serve the San Mateo County community as program managers/owners representatives as the project moves from planning to execution, helping SamTrans to implement a complex program that will be one of the largest the agency has undertaken.