Innovative Braking Technology Helps Power Seattle’s Newest Streetcar Line
A streetcar vehicle travels along Jackson Street in Seattle. Michael Grass / RouteFifty.com
Onboard battery storage is allowing rail vehicles to travel offwire.
SEATTLE — It’s been a big week for transportation news in the Pacific Northwest’s largest city. Not only did local officials on Tuesday announce the opening date for Sound Transit’s University Link light-rail subway extension connecting downtown with the University of Washington via the Capitol Hill neighborhood—March 19—but the Seattle Department of Transportation, with its partners at Sound Transit and King County Metro, opened the delayed First Hill streetcar line for passenger service.
While some in the transit advocacy community may continue to debate whether the mixed-traffic streetcar project was a good investment compared to other transportation priorities in fast-growing Seattle, there is something quite innovative about First Hill line’s vehicles: they use an Onboard Energy Storage System, or OESS.
While Seattle’s Czech-made streetcar vehicles are powered via an overhead catenary wire that supplies electricity, just like those that power many King County Metro trolley-bus routes around hilly Seattle, they also harness energy produced through braking which recharges a battery.
So in the case of Seattle’s streetcar operations on the First Hill line, vehicles run on battery power for the inbound, mostly downhill trips to Pioneer Square. At the terminal station location at South Jackson Street and Occidental Avenue South, the streetcar’s pantograph rises to connect with the overhead power supply to recharge during the uphill, outbound trip to the Capitol Hill terminus.
Here’s how it works, according to the Seattle Department of Transportation:
Initial tests were performed on a test track at the factory where the first streetcar was completed in the Czech city of Ostrava. The streetcar operated off-wire for 3 miles, using 25% of the battery capacity of the OESS. Subsequent tests were performed on the Ostrava streetcar system. This allowed for uphill and downhill operation and simulation of traffic conditions that may be encountered in Seattle. During this testing, the streetcar operated on battery drive for distances as great as four miles and durations as long as 37 minutes. The testing also demonstrated that batteries recharge rapidly from regenerative braking and during operation on the OCS.
The test results indicate that the OESS will be more than adequate for the requirements of the First Hill line, and can also be used for significant segments of the planned Center City Connector streetcar extension.
While recharging rail vehicle batteries via braking isn’t a new technology, more and more streetcar and light-rail systems are using the regenerative braking technology, including the Dallas Area Rapid Transit system. Other U.S. rail systems in Philadelphia, Los Angeles and Portland, Oregon, use similar power generation and battery storage technologies.
As The New York Times reported recently, braking trains using the Southeastern Pennsylvania Transit Authority’s Market-Frankford subway line in Philadelphia actually pump energy into substations along the route and back into the grid. And that generates revenue for the agency, which has “saved about $40,000 in electricity costs for each substation and brought in revenue of $250,000 a year since it started running in 2012,” according to The Times.
Michael Grass is Executive Editor of Government Executive’s Route Fifty.
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