Can solar power fuel mass transit?

Bay Area Rapid Transit (BART) commissioned Arup and the Center for Sustainable Energy (CSE), a San Diego–based nonprofit, to determine whether solar energy could help power its system. Arup’s work looked at potential applications for solar-powered mass transit.

The solar potential across America and Germany
The solar potential across America and Germany
  • Updated: 04 December 2017
  • Author: Tony Bruzzone, Associate Prinicipal & Dahlia Chazam, Associate Principal | Integrated Planning

Why is this important? What are the potential implications for the future?

Moving more than 430,000 passengers across 107 miles of track each weekday requires a massive amount of energy, making BART one of Northern California's top 10 power consumers. The agency has been investigating ways to obtain more of this energy from renewable sources. As part of this effort, it asked Arup to consider the potential impact of placing photovoltaic (PV) arrays on its substantial real estate holdings.

After studying the technical and economic issues for a year, we concluded that BART could increase the amount of on-site solar by means of PV installations on stations, parking lots, maintenance facilities, and other properties.

Solar array
Areas such as parking lots could be covered with solar arrays

This has important implications for cities around the nation. Most of the United States receives enough sunshine to generate a substantial amount of solar power. (The country sees far more sun than Germany, which now gets over 7% of its overall power output from solar.) Transit agencies from coast to coast could therefore take advantage of PV generation.

But this would require them to contend with the mismatch between peak travel hours (morning and evening commute times) and peak solar hours (midday). Maximizing solar generation's potential would require energy storage as well as energy "wheeling," or exporting power around a system's internal power distribution network.

Our team initially considered this a drawback of solar due to the costs associated with energy storage. Upon further consideration, however, we determined that this solution confers unexpected benefits. By providing an independent power supply in the event of a grid failure, it makes transit systems more resilient.

What are the next steps for the research?

The research team recommended short-, medium-, and long-term strategies for maximizing BART's solar power potential.

Short-term suggestions included installing solar PV in low-risk, high-reward locations (e.g., parking lots for new stations) and adding energy storage capabilities. In the medium term, we recommended doubling PV installations and working to implement smart-grid technologies. Long-term advice included covering maintenance yards with PV arrays and working with the owners of adjacent properties — the Port of Oakland, for example — to realize mutual benefits through solar generation.

Arup is currently helping BART to pilot energy storage that may ultimately position the system to address misalignments between peak travel times and peak solar hours.

Moving beyond research

BART entered into an agreement with Solar City to install, operate, and maintain solar panels at the new, upcoming Antioch station as well as at the existing Lafayette Station. BART will purchase electricity generated from these two new installations, which once constructed will be the largest solar generation facilities on BART property. As an additional benefit to customers, the panel canopies will provide shade over a portion of the parking lots at each location. The cost of the project will be paid from the energy operating budget, and will cost a cumulative $3.75 million and $3.85 million at Antioch and Lafayette stations, respectively, over the 20-year term of the agreement.

First published on Doggerel