The Comeback King: Flywheels Make a Surprise Return to the 21st Century 0

John Rennie | Thu Dec 1 2011 |

The benefits of solar, wind, and other renewable energy sources are clear. Environmental progress, increased national security, and greater energy diversity are just some of the advantages these sustainable technologies provide. Still, a universally acknowledged challenge exists: the power renewable energy sources provide can fluctuate with literally every passing cloud.

One solution that could help utilities stabilize the load on regional and national power grids involves an old technology taken to a colossal new scale: flywheels for energy storage.

Meet the flywheel

Simple flywheels have been around for centuries, and were once a routine component of mechanical wristwatches and clocks. Like batteries, they are energy storage devices. But instead of stockpiling energy in chemical form, flywheels hold it in the kinetic energy of a spinning, low-friction rotor. The larger and heavier the rotor and the faster that it turns, the more energy is in the flywheel. Speeding up or slowing down the rotor transfers energy in and out of it.

The drawback of flywheels is that they tend to be more expensive to install than batteries and other devices, and they cannot yet begin to hold as much energy as storage systems based on water pumped uphill or on air compressed inside sealed chambers.

On the other hand, flywheels can be installed anywhere. Their storage efficiency, which exceeds 90 percent, beats that of most other devices, and they can last for 20 years and perhaps 100,000 cycles, which equals a projected lifetimes of about 20 years.

Utilities can park small surpluses of energy in the flywheels, then pull the energy back out as needed.

That combination of virtues could be exactly what utilities need to help with the challenge called frequency regulation. The supply of power on a grid should ideally equal the demand so that the frequency of the current holds steady. Utilities therefore constantly tweak the outputs of generators up and down slightly as needed to produce that match. Those adjustments hurt the generators’ efficiency, however, which adds cost.

Flywheels (and other storage devices) can help this situation. Instead of stepping the generators up and down, utilities can park small surpluses of energy in the flywheels, then pull the energy back out as needed.

According to William A. Franks, Director of International Business Development for Beacon Power, the flywheel can track the grid’s needs “very, very precisely” because it can respond within seconds, unlike alternatives such as fossil-fuel burning generators. “And if you can correct [the imbalance] sooner, you need less correction,” he says.

The rise and fall of Beacon Power

This past year, Beacon Power brought online a 20-megawatt flywheel facility—the world’s largest flywheel energy storage system—in Stephentown, New York.

The $60-million Smart Energy Matrix facility—which began operation in January and reached its full 20-megawatt capacity in June—harnesses 200 of the company’s advanced flywheel systems, which the company developed over the past decade in cooperation with the U.S. Department of Energy, the New York State Energy Research and Development Authority, and the California Energy Commission.

Flywheel system companies like Beacon stand to benefit from a proposed rule change that the Federal Energy Regulatory Commission announced last February under which grid operators would pay the operators of energy resources according to the quality of their service. Because flywheels can respond to the grid’s balancing needs much faster than fuel-burning generators can, they would collect extra revenue.

Beacon has stated that it’s hoping to continue to operate the Stephentown facility, which should bring in several million dollars annually.

Unfortunately, that rule change may be arriving too late to do Beacon much good, which has operated in the red throughout its 13-year history.

This past August, the Department of Energy guaranteed $43.5 million in loans to Beacon, but on Oct. 31, the company’s board announced it would reorganize under Chapter 11, declaring $72 million in assets and $47 million in debt. Beacon has stated that it’s hoping to continue to operate the Stephentown facility, which should bring in several million dollars annually.

It remains to be seen if Beacon’s bankruptcy will prompt investors, already wary of renewables, to become even more leery of flywheel technology.

“I think if it turns them off flywheels, they’d be doing themselves a disservice,” says Theodore O’Neill, a cleantech analyst for Wunderlich Securities. He describes the technology as “pretty darn robust” and, in his opinion, a better alternative than lithium-ion batteries for big grid applications. Beacon “just ran out of time” with investors, he says.

The great flywheel debate

Confidence in flywheels is far from universal. A white paper on energy storage released by the Electric Power Research Institute concluded that despite their longevity and speed advantages, flywheels might ultimately be too much more expensive for frequency regulation than competing alternatives on a dollars-per-kilowatt basis. Nevertheless, a number of companies other than Beacon, including Advanced Power, Vycon, and Amber Kinetics, are continuing to push flywheels forward.

Ed Chiao, CEO of two-year-old startup Amber Kinetics, for example, explains that his company is developing rotors out of strong, relatively lightweight steel that costs per pound only one-twentieth of what carbon fiber does.

Working with the less expensive and structurally simpler material will make flywheels much more cost competitive, he says, particularly at very large scales. The company is currently seeking partners and aiming for commercial product development and field installations in 2013.

Illustration by Chris DeLorenzo