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Pentadyne Seeks Funding for Using Flywheels in Railway System to Save Power


Pentadyne Power, based in Los Angeles, is seeking $15 million in funding to launch a flywheel energy storage technology in electrified railroads, to save the energy consumed when the train leaves the station. They recycle the energy normally dissipated when a train brakes to accelerate a flywheel, and then they use the flywheel to help the train re-accelerate when it leaves.

Flywheel storage systems are already in use in New York’s subway system, but Pentadyne wants to implement the technology on a larger scale. Up to now, the company built UPS systems based on flywheels, so their expertise in this field is significant. UPS (Uninterruptible Power Supplies) are used to provide backup in case of grid outages. Knowing the fact that these outages last less than 15 seconds, and the immediate need of power is critical in applications like hospitals, data centers, etc. The 15 seconds are enough to let other, more powerful generators, like diesel ones to kick in.

Owning less than 10 percent share of the UPS market, flywheels are still a hope, considering that only five years ago their share was zero. Moreover, flywheels have a typical lifespan of about 20 years, while a lead-acid battery needs to be replaced every three to seven years.

The newest application of Pentadyne’s flywheel technology is energy storage and deployment for electric locomotives. The flywheel operates in place of a substation, delivering power to the train through the third rail.

“It’s the only device on the planet proven to capture the complete braking energy of the train and release it to move the train away from the station,” McGough said.

In August 2009, Pentadyne scored a $4 million contract to supply flywheels to the Long Island Railroad in New York. Pentadyne has also been in talks with municipal transit authorities (MTAs) in Prague, Warsaw, Beijing, Shenzhen, Washington, D.C., the San Francisco Bay Area, Los Angeles and New York, said their CEO, Mark McGough.

“These are among the MTAs interested in applying this technology, and it’s a fundamental reason we’re looking for more capital,” McGough said, speculating that rising demand for public transit is going to necessitate technologies that can provide more power to move additional passengers and train cars.

Flywheels are built from composite materials, which are very durable and can spin at tens of thousands of rotations per minute, storing the energy mechanically. That energy is then harvested through magnetic fields, and the whole process has an 85% efficiency and an instant response. To maintain their speed, flywheels run on magnetic bearings in voided chambers, so the friction is close to zero, and that’s why the energy needed to keep them spinning after they reached their “cruise speed” is minimum.

Flywheels have also been used in racing cars, promoting an avant-garde technology that is probably to be applied in street cars later. Also, they have various applications as grid backups with various companies developing them for the energy market.

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