More than ever, batteries dominate our lives as we plug in convenience items like phones, watches, and earbuds. Now chargers are appearing in garages for bigger items. Hello, Tesla, Bolt, and Leaf!
To spur this trend forward, the government got involved, pushing mass transit to transition to battery-based products as a way to mitigate climate change.
The California legislature mandated that all light- and medium-duty public vehicles be zero emission by 2040. It then accelerated that timeline to 2035. Going even further, the law said 2025 would be the last year to purchase a diesel vehicle.
Soon after, officials in Santa Clara County, which includes cities like San Jose and Palo Alto, sought help from power systems and battery experts as they considered what the mandate would mean to the Santa Clara Valley Transportation Authority (VTA), which operates public transit services like bus, paratransit, and light rail.
The impact of the state mandate will be highest for bus and paratransit vehicles, changing how VTA operates day to day. It will have to incorporate charging (and discharging) of buses into its daily operations, not to mention the purchase of charging equipment to ensure buses can run and complete their schedules on time.
The Lehigh University Western Regional Office connected county officials with Shalinee Kishore, Iacocca Professor of Electrical and Computer Engineering, an endowed chair at the university, who is also director of the Institute for Cyber Physical Infrastructure and Energy. The institute seeks to enable success for interdisciplinary research teams of faculty working in the areas of energy and infrastructure systems.
She is working with a team of faculty and students to assist VTA and, more broadly, other transit agencies with this major transportation transition to electric bus fleets.
The project
VTA bought the first set of electric buses about four years ago to conduct trial runs on routes and track key data points on battery use and miles. Charging is also being tested, both along the route and at the bus depot. The challenge in keeping the buses charged is the cost. Electricity prices vary greatly during the day and season. When the sun is out, prices drop as more people and companies rely on solar energy in places like California. But when the sun goes down, which is often when most buses are returning to the bus depots and need to be recharged, the rates are very high. The challenge VTA faces is two-fold — scheduling the buses to meet route schedules and customer demand while also having the power infrastructure in place to literally keep the buses moving. Solar panels need to be installed at bus depots to generate the green power for bus batteries during the day, but the challenge is storing it since the buses may not recharge till later in the day.
This is where more affordable large-scale battery storage systems come in. VTA is considering installing the systems along with solar panels to generate and store free solar energy in the day to help offset costs of charging buses later in the day. This has the added benefit of ensuring the buses are charged from green solar energy with truly zero emissions.
Lehigh’s role
Lehigh is partnering with VTA to help it study and plan the electric fleet rollout. One key aspect is helping VTA analyze data from its current electric buses and chargers. These new buses have many sensors that measure a variety of parameters every 5-10 minutes, like the bus battery-charge level, temperature inside the bus and outside the bus, how often the bus runs idle, how often the brakes are depressed, the air conditioning or heating settings, etc. These are all factors that can impact the battery’s load when driving. Lehigh faculty and students are analyzing the data to develop an electric bus energy-consumption model to help inform how the transit agency should grow its electric fleet and its charging, solar, and energy-storage infrastructure.
The Lehigh team also plans to assist VTA with community outreach to help educate the public about this initiative since it will impact routes and charging station stops. The public also needs to understand the benefits of zero-emissions transportation systems and clean-energy charging. There are a number of environmental and health benefits for people in low-income neighborhoods where diesel traffic traditionally has been routed.
The Western Regional Office, particularly Wendy Fong, has been crucial in connecting Lehigh to VTA and to these successful interactions. In the past four years of this collaboration, nearly 20 undergraduate students and nearly 10 graduate students have been involved in the project. Some of the undergraduates are part of computer science and business capstone projects. More recently, this initiative has led to offshoot projects. There are now master’s students in the Energy Systems Engineering program working on solar solutions in the Lehigh Valley to address the truck traffic from warehouse distribution centers.
The added dilemmas
This energy transition in the transportation sector has brought other opportunities and challenges with it. While this project focuses on transit bus fleets, the mandate impacts all public vehicles, including fire engines, police cars, and emergency medical transport. So each entity is facing the same transition. And these challenges apply to all kinds of entities outside California that are looking to reduce or eliminate emissions of their fleets.
Another obstacle in this transition lies in the battery on the buses. The standard diesel bus has a 25+ year lifespan whereas batteries in electric buses have a six-seven-year lifespan. After this time, the bus battery continues to work, but it loses the range required and discharges faster. Another avenue the Lehigh team is looking into is second-life opportunities for those batteries, repurposing them to serve as storage for solar energy generated on sunny days.
Finally, perhaps the most critical challenge in electrification of transit systems is the one that predates this transition. America is not enamored with public transportation, so ridership has steadily declined for decades. More recently, private entities like Uber and Lyft have created other options for urban riders. Remaining effective and affordable is important in the planning of operations and infrastructure during this major transition.
Endowed chair
Kishore’s endowed chair position has played a role in helping to spur this research project and collaboration with VTA. The endowed chair provided funds for computing equipment and software, travel to VTA, partnership event costs, conference attendance, and preliminary research. All this has helped initiate the project and enabled the team to pursue large teaming grants with VTA and other partners.