Electric buses are seen as a triple threat in the fight against climate change as they promote energy-efficient urban population density, reduce pollution by replacing multiple vehicles, and do not emit tailpipe emissions. However, the increasing popularity of electric buses poses challenges for cities, as their power grids may struggle to keep up with the increased demand. University of Utah engineering professor Xiaoyue Cathy Liu views this challenge as an opportunity to rethink public transportation systems and integrate them with other civic infrastructure. By integrating solar power generation and energy storage at bus depots, Liu proposes transforming them into energy hubs that produce more electricity than they consume, thus improving grid stability.
In a study published in the journal Nature Energy, Liu and her international collaborators analyzed the potential of integrating solar power at Beijing’s fleet of 27,000 electric buses. These buses, which make up the world’s largest public transportation system, are predominantly low- or no-emission vehicles. Recharging at more than 700 bus depots across 6,500 square miles, these vehicles place a heavy load on the region’s electrical grid, raising concerns about grid stability. By using advanced data science techniques, Liu and her team are investigating whether locally generated solar power can offset this demand, potentially making the depots energy producers and further stabilizing the grid.
The study utilizes a computer model of the Beijing bus network, incorporating real-world data on air temperature and solar irradiance at each depot over the course of 2020. By analyzing the rooftop surface area of each depot, the researchers can predict the electric output of solar panels that could be installed. However, the model is complicated by differences in supply and demand between depots, with busier depots able to maximize solar energy while more remote depots must manage excess electricity. Energy storage emerges as a critical factor in the model due to its expense, highlighting the need for smarter and strategic charging schedules to account for variable energy pricing schemes that impact economics.
Liu and her team aim to generalize their model to provide a framework for other countries interested in transforming their bus depots and civic infrastructure into energy hubs. By estimating the return-on-investment of such transformations, they hope to demonstrate the economic viability of integrating renewable energy sources into public transportation systems. Ultimately, their research seeks to not only address the immediate challenge of grid stability with the rapid deployment of electric buses but also to revolutionize the way urban transportation systems are powered and integrated with sustainable energy sources. Through innovative solutions like the integration of solar power at bus depots, cities can leverage public transportation infrastructure to contribute to a cleaner, more resilient energy future.
