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Beacon Power Reports Significant Progress Towards Commercial Flywheel System

The Smart Energy 25.

Beacon Power Corporation has assembled and spun up to more than 11,000 rpm the first pre-production unit of its fourth-generation Smart Energy 25 flywheel energy storage system. This is slightly more than two-thirds of the target maximum design speed and represents significant progress in the next-generation system’s development, according to the company.

Conventional approaches to frequency regulation—balancing grid power generation with load—vary the power output from fossil-fuel or hydro generators connected to the electric grid. A flywheel system, however, is a storage-based approach, and thus is of particular interest for use in conjunction with renewable power generation (wind, solar) where the primary power output is variable. (Earlier post.)

The Smart Energy 25 is designed to store 25 kilowatt-hours (kWh) of energy and to deliver 100 kW of power. The system, manufactured under multiple Beacon patents, is expected to store significantly more energy than any other commercial flywheel in the world known to Beacon Power.

The results increased the company’s confidence that the unit will meet full performance specifications in further testing before the end of Q1 2007, enabling it to be coupled with other such units to build a Smart Energy Matrix later that year.

This flywheel system is the cornerstone of our commercial Smart Energy Matrix, and we’re very pleased that our team was able to progress from specification to initial operation two months ahead of schedule. This accomplishment gives us greater confidence in achieving our milestone of generating first revenues from frequency regulation services before the end of 2007.

—Bill Capp, Beacon Power president and CEO

Upon completion of Beacon’s testing of this Smart Energy 25 unit, the Company plans to start production of units to build multiple Smart Energy Matrix systems, so as to supply commercial-level frequency regulation services. The goal is to manufacture and install a sufficient number of Smart Energy 25 flywheels to provide at least one megawatt of revenue-generating frequency regulation service before the end of 2007. Beacon also plans to expand production to achieve its goal of 10 to 20 megawatts of revenue-generating service by the end of 2008.


Thomas Pedersen

I think flywheels are a great solution to e.g. New York subway, where they can both deliver acceleration power and absorb braking power.

However, as nothing more than load smoothing, I think there are better/cheaper options. The best option, in my mind, is intelligent power consumption, both industrial and residential. There is a huge untapped market for intelligent power consumption. All that is required is an intelligent power meter that buys power according to the grid-price on a minute-by-minute basis, rather than a two-stage tariff. Once those are in place (first in new-builds and replacements), people and business will see the potential savings of fitting house-hold appliances with a $1 control chip that automatically cuts consumption to aircon, water-heater, dryer, etc. when the price is high, and uses more power when the price is low. This way it doesn't matter when the price is low; whether it's during daylight because of PVs or at night from nuclear power.

You would need an awful lot of 25 kWh units to reach the same regulation power.

Rafael Seidl

Thomas -

stationary flywheels and ultracap banks are used for ride-through power, i.e. masking power fluctuations of <30 seconds in one segment of the grid from other segments. Such fluctuations can occur when there is a failure in the supply chain and the network self-heals. It can also occur when a major consumer comes online, e.g. due to the inrush current of a (very) large electric motor in a factory or, a whole neighborhood coming back online after a power failure at a substation.

You mention another application, rail grids. In these, acceleration and recuperative braking events generate sharp but short-lived peaks and valley in the electricity demand of a given segment. Presently, a significant fraction of the recuperated energy actually has to be dissipated in snubber circuits because there is no available sink for it (the dynamics of the primary system do not permit a sufficiently rapid response). By installing ride-through energy stores, aggregate efficiency can be improved. Such stores can be located in basements with thick walls that will limit the damage in the event of an uncontrolled energy release.

It's also possible to install a flywheel energy store directly into a vehicle, provided you use a special suspension (e.g. gimball cage) and the energy interface is electrical rather than mechanical. This eliminates the internal gyroscopic moments that would otherwise massively stress the (magnetic) bearings and interfere with vehicle steering during rapid cornering and/or changes during hill descent angle. Even so, a fully charged flywheel represents a concentrated store of mechanical energy and hence, a potential crash safety hazard. Adding a sufficiently robust containment vessel typically leads to an substantial increase in bulk and weight, which is acceptable only in rail and special HDV applications (e.g. the Fraunhofer AutoTram).


My God, Rafael, you know some stuff. Thanks as always for your input!

Harvey D.

Thomas & Rafael:

Thank you both for valuable information concerning two very different problems with electrical energy distribution.

Short term negative/positive load variations are often best addressed at the source with the use a various smoothing devices.

Longer term variations, mainly local/regional high consumption peaks, could easily be addressed with smart meters as Thomas Pedersen mentionned. Similar meters are already in use in many European countries. Unfortunately, our North American culture (to do everything we want at any time) would not tolerate the installation and use of this common sense technology.

Our Power Supplier, with consumption peaks at around 35 000 megawatts but an average consumption of only 20 000 megawatts, prefers to buy power at very high price during cold winter days instead of temporarily turning off (during peaks hours) one or two million dryers and/or hot water heaters.

The main reasons blocking smart meters is customers resistance and our acquired culture. Even if nobody would notice that the hot water heater was automatically turned off for two hours or so many customers would complain and even sue the Power suppliers. The only way to make it work would be on a voluntary basis and/or by giving the participating users suffisant financial advantages with lower rates.


Thanks Raefael for the information about flywheels in transportaation related areas.

I contend the better use will be for storing excess solar energy captured during the day. A huge advantage of solar is that it can use the least valuable land in a given area. And flywheel storage can do the same (Large flywheel storage is best kept underground for saftey.)

Both solar and flywheel also have the merits of being useful almost anywhere and to any nation. And unlike other energy sources there is no need to quarrel about pollution, supply, or weapons production.


From time to time I tell of stories my father told me as a diesel engineer. One system was a flywheel energy storage device I believe the company was out of Utah.
As it was told to me to biggest problem (atleast 10-20 yrs ago) was exploding flywheels. The flywheels then were carbon/fiber graphite and other materials,maybe kevlar? But the point was the magnetic bearings vacuum sealed were problem free even back then. The flywheels spun 10,000's of RPM and were somewhat reliable but any jaring that took place exurted tremendous loads on the outer flywheel and the resulting instantanous release of energy and debree would cause a huge noise when colliding with the containment housing.

The way they tested the flywheels back then was to have timed runs followed visual amd X-Ray inspection of the flywheels. My father refured to seeing flywheels that have spiderweb like cracks growing from the center outward. When these cracks reached far enough out... BOOM! Like a huge steel drum! Maybe I am wrong but stationary large scale wharehouse style use of these flywheel devices seems the best. If memory serves correct even a few years back a 40lb flywheel assebly yeilded 80-100 HP/Hrs. For subways I'm with motor/generators with onboard ultracapacitors.


At 25 kwh per unit it would require too many to convert the output of a large solar array into a 24 hour constant average output. I didn't catch any mention of price/hiring charges or whether maintenance crew were needed. The risks of flywheel disintegration or fire in large battery banks is never mentioned by those whose say only nuclear is dangerous.


Curious as to why there is no discussion of intelligent meters purchasing off-peak power for localized storage. A 25Kwh ultracap or flywheel should readily handle higher consumption appliances during peak grid expense/usage, effectively lowering peak demand.

This begins to move residential power consumption to localized systems combining off peak grid with PV or other alternatives (community PV/storage banks.) With intelligent controllers such systems provide emergency/backup power locally, while decreasing reliance on peak grid use.

Granted there is expense here, however with the advent of BEV/PEV vehicles - localized power consumption and costs will eventually force the issue.


Rafael, Thomas,
The NY Transit (MTA) installed ordinary flywheels on some of their subway cars a while. The new cars (R142, R143, R160) will have electric regenrative braking. They may be able to retrofit some sort of regen system on their R62, R68 series when they come up for a rebuild.


Here is a pneumatic/hydraulic/electric hybrid propulsion system w/regenrative braking:


The NY Transit (MTA) installed ordinary flywheels on some of their subway cars a while back (during the early 80's). It was part of an experiment spured on by the energy crisis a decade earlier. They were removed after mediocre results.

Rafael Seidl

K, Aussie -
it's a lot cheaper to make wind and solar work in conjunction with already amortized hydro dams, at least at this early stage. Deliver electricity from the unpredictable sources whenever they are available, sell any excess to competitors otherwise running off natural gas (or use it to pump water uphill) and conserve hydro power for when there's neither a breeze nor sunshine. Renewables suppliers are on a grid, so they should use it.

Aussie -
anytime you store a lot of energy in one place (hydro dams, flywheels, fuel tanks, steam boilers, fuel rod assemblies etc.) you have to manage the risk by including active and passive safety features in the design. Nevertheless, Murphy's Law will strike at some point in time, causing loss of property and possible loss of life as well. Radioactivity is a special case because the damage continue to accumulate for a very long time.

Andy, Allen -
please don't forget that in the 80s (or even the 90s) engineers' ability to predict system behavior, especially wrt failure scenarios, was much more limited than it is today thanks to advances in affordable computing power and software. Also, composite matrix materials, power electronics and control circuits and electric motors (e.g. PM synchronous types) have advanced markedly in the same period.

Even so, flywheels do continue to pose very challenging design and manufacturing problems. For example, the Laval disc has to be produced in a high vacuum to prevent any risk of outgassing in operation. The bit about the need for explosion containment also still holds, which is why I believe they are best used in stationary system.


Here is a site for you:


Rafael, et al. I also think pumping water uphill can be a good way to store solar or wind. And it still makes sense where the hydro is already paid for. But too many areas simply don't have the potential for hydro, flat terrain, no water to speak of, or crowded areas where large lakes aren't going to be built.

That is why I began to think of flywheels. They are a pure engineering and manufacturing problem and don't require much land or maintenance. And have little or no impact on terrain, ecology, or politics.

Aside: Several decades ago I read of a Swedish plan to compress air and store it in underground quarries as a power reservoir. I think one problem was that the air became so hot it melted stone walls.


Thanks Allen,

The site was interesting, underscoring utilities' support for BEV/PHEV solutions especially. Like any very large system they avoid the localized generation/storage issues seeing them as decentralizing and competitive. But the power outages of three years ago in U.S. northeast produced a flood of desire to put "off-grid" supplemental systems in place.

Hybridization of energy systems should be part of the planetary prospectus. The vulnerability of centralized grids is one issue. The integration of residential/community PV and alternatives is another. EPRI and electric utils have to get on board with off-grid energy generation and storage for the big picture to work.

There will still be plenty of dividends for util investors - their product is no less than a significant "future fuel."


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Michael van Holst

Rather than placing these in the supply chain to stabilize power production, would they not be better located at point-of-use, where they would have the effect of averaging out the daily fluctuation in demand? Could these be priced viably for residential or commercial buildings?

Henry Gibson

In case someone comes back to this, Sodium sulphur batteries as well as vanadium flow batteries are available for stationary power fluctuations. Flywheels are very good for brief power peaks. Ordinary compressed air cylinders are being used for one UPS system. Batteries are still to expensive for energy storage in most cases. ..HG..

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