technology today

Alan Pierce pierceaj@techtoday.us

Hi-Tech Flywheels Spin Kinetic Energy into Electricity

A flywheel is basically a heavy	exceeds that being generated by
disk, wheel, or drum rotating on a	the power plants, these high-tech
shaft. What causes a flywheel to spin	flywheels spin their stored kinetic
and what determines the thing it	energy back into electricity.
produces depends in many instances	To accomplish this task, each
on when in history it was used. Histo-	flywheel shaft is linked to a magneti-
		cally levitat-
		ed motor/
		generator.
		When
		electric-
Corp.		ity exceeds
		demand,
		the motor/
Power
		generator
Beacon
		acts as a
		motor to
courtesy
		spin up the
		speed of the
Photos
		flywheel.
		When
Photo 1—Aerial view of the new Beacon Power		demand
flywheel generating facility		exceeds
		electricity,
rians tell us that flywheels have been	the motor/generator acts as a genera-
in use since approximately 3500 B.C.	tor that allows the spinning flywheel
Since their invention, flywheels	to convert its kinetic energy back into
have stayed relevant because of	electricity as the flywheel slows under
their amazing ability to function as	the load of turning the
an energy intensifier, energy equal-	generator.
izer, and storage medium for energy	What makes this
derived from intermittent resources.	electricity very spe-
In ancient times, they were found on	cial is the fact that
potter’s wheels, water wheels, and	it is created without
spinning looms. In modern times, we	burning any fossil
find them in a seemingly infinite num-	fuels and the produc-
ber of places, including automobile	tion process doesn’t
engines, industrial machines, earth	create any green-
satellites, and even children’s toys.	house gasses. By
The U.S. electric grid is now be-	using flywheel tech-
ginning to adopt flywheel farms to	nology to meet spikes
store electricity as kinetic energy.	in demand, the need
Here, this ancient technology is used	to burn more fossil
as a mechanical battery. The basic	fuel at an existing
concept behind the flywheel battery	plant or the need to
is easy to understand. When elec-	build a new fossil fuel
tricity generation exceeds demand,	electricity-generating
the extra electric power is used to	plant is, at least for
spin high-tech flywheels to turn the	the moment, abated.
electricity into stored kinetic energy.	Photo 1 shows an
When the demand for electricity	aerial view of the new

10 techdirections ◆ © 2011 techdirections. Reprinted from the November 2011 issue.

fully operational Beacon Power 20 MW flywheel plant in Stephentown, NY.

Since July of this year, Beacon’s 160 flywheel generators in Ste- phentown have been taking excess electricity out of the New York State electric grid for storage as kinetic energy and then converting it back to electricity as it is needed. This activi- ty prevents electrical spikes and dips that can easily damage electronic equipment. The goal here is to keep the electric grid’s electricity output at a steady 60 Hz.

The need for off-grid energy stor- age and re-generation is significant, and a number of technologies are being used to address the need. Since flywheels have played a role in technology for over 5,000 years, I selected them as the off-grid energy storage system to explore in this col- umn. You might want your students to explore other off-grid technolo- gies. Topics for their research could include new emerging systems based on lithium-ion batteries, flow batter- ies, fuel cells, ultra-capacitors, and even molten salt batteries.

The goal of these off-grid systems is to prevent ac (alternating current) from fluctuating when demand quick- ly spikes up or down. What makes flywheels and other off-grid storage systems important is that they can act more quickly than the frequency

Photos 3 and 4—The Smart Energy 25 fly- wheel parts are fabricat- ed to extreme toleranc- es, carefully assembled, and tested to guarantee that they can withstand the extreme speeds that they will operate at.

regulators that currently accelerate and decelerate power plant turbines.

The Beacon Smart Energy 25 flywheel rotor assembly includes a carbon fiber composite rim, metal hub, metal shaft, motor/generator, and magnetic bearings all spinning together in a vacuum chamber. The system has been specifically de- signed to keep friction loss of energy to a minimum. See the schematic diagram (Photo 2) to see how all of these parts fit together.

The fabrication and assembly process demands extreme accuracy. (See Photos 3 and 4.) If parts are off in size or alignment, the unit would rip itself apart when it starts to spin at up to 16,000 revolutions per minute. This spinning speed equals about 1,500 miles per hour—twice the speed of sound. The reason the flywheel can spin so fast and thus

absorb so much energy is because all parts are fabricated to extreme toler- ances, they are rotating in a vacuum, and they are levitated by magnets so

they don’t touch the shaft that they spin around.

The need for off-grid energy stor- age is expected to explode as more of our future electricity needs are supplied by wind, solar, wave, and other new intermittent green energy power systems. These systems will definitely need a method for storing the energy they produce when it is abundant and then releasing it back into the system when the energy that they produce is not sufficient to meet needs. An off-grid system like one involving flywheels will need to jump into action when the wind doesn’t blow, the sun doesn’t shine, or ocean waves don’t have enough oomph for these green systems to supply signifi- cant electricity to the electric grid.

You can see a video that shows how the Beacon Smart Energy 25 fly- wheel works online at http://beacon power.com/includes/videos/flywheel- video.html?KeepThis=true&TB_ifram e=true&height=430&width=478. If you have problems with this link you will find the video on my website at www. technologytoday.us/page13.html.

Recalling the Facts

1.Why is the flywheel energy sys- tem described as a sustainable green technology?

2.It is very unusual to find a land- based system that can sustain Mach

2speeds. How does the Beacon Smart Energy 25 flywheel manage to spin so fast without ripping itself apart?

Alan Pierce, Ed.D., CSIT, is a tech- nology education consultant. Visit www.technologytoday.us for past col- umns and teacher resources.

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