Powering A City With Its Subways And Massive Spinning Wheels

Coming to a city near you soon: By adding giant flywheels to subway systems, cities are able to harness the power created by thousands of braking trains, using it to accelerate other trains or feeding it back into the grid.


Every time a train starts and stops, it draws or dissipates several megawatts of energy, enough to power more than a thousand homes. This happens thousands of time per day, every day, in commuter rail systems across the country. In fact, peak demand from New York’s rail system could power Birmingham, Alabama.

A more efficient system would hand off power from braking trains to those leaving the station. Modern trains run their electric motors in reverse to slow down then release the energy as heat or into a grid ill equipped to absorb the surge.

Energy storage could eliminate the problem.

Flywheels, an old technology finding ever more modern applications, may be that storage solution. Large spinning discs, held in frictionless magnetic bearings spinning at 20,000 to 50,000 revolutions per minute, are able to store energy, and send it back within seconds.

Flywheel technology is now breaking into the rail industry. Actually, it’s breaking back into the industry after a successful trial with the New York subway system in 2002 that went off the rails when the original train-flywheel company shuttered despite pending orders from the city.

Now the technology may be back on track. Vycon, which installs flywheels for other applications such as shipyard cranes, is approaching transit systems in the U.S.


“We were on the brink of really bringing flywheels into the rail industry [in 2002],” says Louis Romo, vice president of business development for Vycon. “Our business was just getting started, but that really messed things up.”

Ten years later, Seattle and L.A. have signaled interest in the technology, along with several other cash-strapped cities searching for simple energy solutions. It’s because it makes financial sense: The technology saves money, cuts energy use in half, removes expensive power substations, and allows trains to run more smoothly (unbelievable but true: schedules are often inconveniently staggered because not enough voltage is available to handle multiple train departures).

But, given the economic downturn, funding is tight. “Outside of the U.S. is where I have the most interest, in China and India,” says Romo. “The problem is that we don’t want our first install that far away.”

If flywheels don’t gain momentum in the U.S. again, we may have to go visit our economic rivals to ride the future of high-efficiency rail.

[Image: Flickr user Randy Pertiet]

Reach Michael J. Coren via Twitter or email.


About the author

Michael is a science journalist and co-founder of Publet: a platform to build digital publications that work on every device with analytics that drive the bottom line. He writes for FastCompany, The Economist, Foreign Policy and others on science, economics, and the environment. His favorite topics are wicked problems -- and discoveries such as how dung beetles rely on the light of the Milky Way to navigate (and all that says about the human condition on Earth)