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Power Storage in Flywheels

Utility-scale flywheel power storage is becoming a reality at a new facility in Pennsylvania

Posted on Dec 12 2013 by Alex Wilson

The great thing about writing a regular blog is that reader feedback sometimes introduces me to new products and systems. So it was last week when I wrote about a company developing power grid electrical storage systems using lithium-ion battery technology.

From a reader, I learned about another, very different approach for storing electricity to make the utility grid more stable and resilient: flywheels.

Our company has written in the past about flywheel electrical storage for use in data centers to provide instantaneous back-up power that can last for a few minutes until back-up generators can be started up. But I had not been aware of utility-scale projects that were in operation.

How flywheel electricity storage works

The idea with a flywheel for power storage is that a small amount of electricity is used to keep a heavy mass rotating at a very high speed — 10,000 revolutions per minute (rpm) or faster. Then when power interruptions happen or some extra power is needed to stabilize the grid, that flywheel generates power, gradually slowing down in the process.

Those of us who read Popular Science have been hearing about the potential of flywheel energy storage for decades; for me, it has been one of those technologies that has been perpetually “just a few years away from commercialization.”

Beacon Power leading the way with flywheel storage

The energy storage company Beacon Power, located in Tyngsboro, Massachusetts (near Lowell), has been a technology leader with utility-scale flywheel power storage since its founding in 1997. In September 2013 the company put online the first 4 megawatts (MW) of a planned 20 MW flywheel energy storage facility in Hazle Township, Pennsylvania. The full system should be completed in the second quarter of 2014.

Beacon Power almost became another Solyndra story. (Solyndra was the solar panel manufacturer that went bankrupt after receiving a $535 million U.S. Department of Energy loan through the American Recovery and Reinvestment Act, giving the loan program a black eye and fanning the flames of right-wing opposition to renewable energy subsidies.) In 2010, Beacon Power received a $43 million loan from the same program, and then filed for bankruptcy in October 2011.

Beacon Power’s bankruptcy was, in part, the result of a change in federal regulations that delayed the requirement for grid operators to pay more for electricity from sources that could feed additional power into the grid very quickly — this affected Beacon Power’s cash flow. Fortunately, the private equity firm Rockland Capital stepped in and acquired Beacon Power and has now paid back most of the DOEUnited States Department of Energy. loan.

The company is back on its feet and moving full-steam ahead.

Stabilizing the utility grid with flywheel storage

The Pennsylvania flywheel energy storage facility can almost instantly (in less than one second) begin injecting significant amounts of electricity into the grid. This will help to stabilize the utility grid — the operation of which is a constant balancing act between supply and demand. Adding this capability — whether with a flywheel or a more conventional chemical battery — makes the grid less prone to blackouts and, thus, more resilient.

The flywheel system is modular, comprised of many of Beacon Power’s Smart Energy 25 flywheels, each of which can deliver up to 25 kilowatt-hours (kWh) of electricity. When delivering power at a capacity of 100 kW, full discharge takes about 15 minutes. When providing 150 kW (heavier power draw), full discharge occurs in 5 minutes with only 12.5 kWh delivered.

The flywheel itself, according to the Beacon Power website, has a rotating carbon-fiber composite rim, levitated on magnetic bearings so that it operates in a near-frictionless, vacuum-sealed environment. It rotates at 16,000 rpm and is designed for a 20-year life with 100,000 full-discharge cycles.

According to Beacon Power, the company’s flywheel power storage system “corrects imbalances more than twice as efficiently as traditional generators while consuming no new fuel, producing no emissions, and using no hazardous materials or water.”

The power grid of the future

Beacon Power’s flywheel system is one example of a variety of new energy storage technologies that promise to make tomorrow’s electric grid quite different from what we have today. As a higher percentage of renewable energy sources, such as wind and solar, feed power into the grid, it will become more and more important to have systems like this that can store power when there is excess available and deliver that power when needed.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. In 2012 he founded the Resilient Design Institute. To keep up with Alex’s latest articles and musings, you can sign up for his Twitter feed.

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Image Credits:

  1. Beacon Power
  2. Forbes Magazine
Thu, 12/12/2013 - 10:00

This would be great for an
by Chris Barnes

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This would be great for an off-grid system. Somehow I don't think that one of these units costs < $10,000 or so though :) Apparently the facility in PA doesn't trust that they won't simply explode, so they've build up dirt walls around each unit..?

Thu, 12/12/2013 - 21:57

Chris: these are fairly large
by Jin Kazama

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Chris: these are fairly large units encasing somewhat large power ... i don't believe it costs alot to burry them and it surely adds alot of safety factor to the installation ( vandal and security wise )

This kind of design should scale well to lower power output and storage,
could be a very green product to use in a relatively sunny environment to store daylight power for later use. Any words on efficiency and standby losses ?

Anyhow, i see this kind of product has a much greener way of doing things than li-ion and other batteries which use hazardous materials and are much harder to recycle.

If kept inside a building, you could probably reuse alot of the "flywheel storage" parts for an overhaul once its designed lifetime is reached.

Fri, 12/13/2013 - 13:26

by david congour

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I'm not an expert on flywheel storage, so take my opinion with a grain of salt; that being said...

I have two concerns:
1. As the speed increases, the amount of stored energy increases. What happens when a bearing fails, or the flywheel itself? Then you have a fragmentation bomb. Better be buried underground.
2. Not a safety concern, but an efficiency one: as speed/angular momentum increase, efficiency of transferring more energy into the flywheel goes down.

Not to put a damper on the idea, but it seems like there should be safer ways!?

Mon, 12/16/2013 - 12:31

Not to worry... (response to david congour)
by Dana Dorsett

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Energy storage flywheel technology is not new technology, and has a good safety record. Since at least the mid 1980 most storage flywheels have used carbon-fiber composite rather then metals as the mass, and when the bearings fail most of the deforming energy is spent converting the carbon-composites into a hot cloud of dust, not a spray of high velocity shrapnel.

I'm curious about how you would support the statement:

"as speed/angular momentum increase, efficiency of transferring more energy into the flywheel goes down."


Wed, 12/18/2013 - 18:51

Hydrogen storage?
by Sam Clarkson

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Where can I find a mine of information on setting up an off grid hydrogen cracker/fuel cell system for storing/regenerating off PV panels in a commercial situation?

Wed, 12/18/2013 - 19:27

Hydrogen storage
by Alex Wilson

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Twelve or thirteen years ago, Iceland was moving actively in researching this issue. From a quick Web search, it doesn't look like too much has happened recently, but that might be worth tracking down. Iceland produces a huge amount of hydro power and geothermal power, and they wanted to use excess electricity during off-peak periods to drive electrolysis, producing hydrogen that could be stored. Then the economy tanked, and I'm not sure what happened to that research initiative.

Sun, 12/22/2013 - 08:53

more density needed
by Hobbit _

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I looked into Beacon Power's offerings a while ago, and realized
that if you pack the same volume as one of their flywheel housings
full of Prius batteries you get about twice the energy storage
density. And that's with NiMH, and the same state-of-charge range
limits as the car maintains on its pack. Modern lithium-based
chemistry and tighter charge control would store even more. So
I'm not convinced.


Sun, 12/22/2013 - 09:18

Power storage technologies
by Alex Wilson

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Even if there aren't significant cost advantages of flywheel power storage compared with chemical battery storage (and I think there are for large, MW-scale systems), whenever we can justify the investment in multiple technologies for achieving the same ends we benefit. I believe that we will need to see costs come down substantially on the storage of electricity generated by renewable energy sources, and I don't know what technology (ies) will get us there, so I think it's great to see parallel development efforts into various battery technologies, pumped hydro storage, flywheels, compressed air storage, hydrogen production from electrolysis--you name it. Hopefully, there will be power storage technologies coming along that aren't even on the list yet.

To suggest that we should only invest in the one technology that seems the best today, in my opinion, is shortsighted. I say the more the merrier!

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