Flywheels - storing electricity for instant demand - smoothing the load from wind energy

The California Energy Commission was created by the Legislature in 1974, and is the state's primary energy policy . A high priority is the development and application of new energy storage technologies - especially as the significant commitment to deploy renewable energy has placed new and complex demands on the state's electricity grid. - a problem not unique to CA.

On this last point it is essential to read ...
See Interim Report - System Disturbance on 4 November 2006 "union for the co-ordination of transmission of electricity" (UCTE) report on the 9 nation power outage across Europe on 4/11/06.

Section 5.1 Page 25

About 40% of the total generation units which tripped during the incident were wind power units. Moreover, 60 % of the wind stations connected to the grid at 22:09 tripped just after the frequency drop.

Sect 8.1 Page 51
"The events in the evening of 4 November 2006 have been the most severe disturbance in the more than 50-year history of UCTE regarding the number of involved TSOs and the amplitude of the registered frequency deviation."

Page 52
"During the disturbance, a significant amount of generation units tripped due to the frequency drop in the system which resulted in the increased imbalance. Most of this generation is connected to the distribution grid (especially wind and combined-heat-and-power)."

Massachusetts-based Beacon Power (NASDAQ: BCON) have developed and tested a novel 100 kilowatt scale-power vertical flywheel energy storage system which is a prototype for a planned 20 megawatt-level commercial system.

A flywheel energy storage system draws electrical energy from a primary source (say wind power), and stores it in a high-density rotating flywheel. The flywheel system is actually a kinetic, or mechanical battery, spinning at very high speeds (>20,000 rpm) to store energy that is instantly available on demand.

Modern electromechanical flywheels couple a motor generator with additional rotating mass. Depending on whether the application requires a long or a short discharge time, one may have a small motor generator coupled to a large rotating mass, or the reverse.

Energy storage in a flywheel is descriibed by the equation:

E = kMv[2]
E = energy; k is a constant based on the shape of the flywheel;
M = Flywheel mass
v = Rotational velocity of the flywheel (speed of rotation).

If the mass of the flywheel is doubled, the amount of energy is doubled.
If the speed of rotation is doubled , you quadruple the amount of energy.

Upon input power loss, the motor driving the flywheel acts as a generator. As the flywheel continues to rotate, this generator supplies power to the customer load.

The Beacon Power The Smart Energy Matrix flywheel design proposes an integrated system of 10 higher-power (25 kWh) flywheels, interconnected in a matrix to provide energy storage for utility-grade applications. This is designed to deliver megawatts of power for minutes, providing highly robust and responsive frequency and voltage regulation capabilities for increased grid reliability.

Flywheel technology also serves as a method to reduce electrical fluctuations and helps regulate the even flow of power (frequency regulation) on the grid. This can make massive cost savings alone as the California ISO, uses and pays for frequency regulation services every day. In 2005 alone , the value of regulation services purchased by four U.S. regional grid operators in open power markets was in excess of $600 million.

Flywheel based electrical storage systems, although often involving higher initital capital costs offer advantages for "sustainable" systems.

1. They do not incoroporate hazardous materials for production, nor create them during operation.

2. Low maintenance and long life.

3. Unlimited discharge / recharge cycles (qv batteries)

4. Can be installed underground to free space and improve visual environment.

5. Remote real time monitoring built in.

6. No degradation of performance with temperature / climate changes.

8. Beacon units have surpassed the Telcordia Level 4 earthquake test - the equivalent of a 7.6-Richter scale seismic disturbance for 40 seconds - without failure.

The 2005 California Energy Commission contract with Beacon Power has demonstrated the potential benefits of using flywheel energy storage for frequency regulation of the grid, became operational in 2005 and completed a series of performance tests and technical assessments prior to a six-month field trial phase on August 1, 2006 which will be completed by l January 31, 2007.

Bill Capp, Beacon Power president and CEO says that the California ISO trial proves that ,"new technologies will be required to maintain grid reliability while achieving ambitious goals for the deployment of renewable energy and the reduction of carbon emissions".

Other companies in the US supplying flywheel storage technology include ;

Active Power, located in Austin, Texas, has developed 2 flywheel power systems that can handle DC loads up to 250 kW and 500 kW, respectively, for short periods of time. In additon, the company has teamed with Caterpillar in the development of battery-free UPS systems.

AFS Trinity, in Livermore, California, produces flywheel power systems for stationary and mobile applications. (Good detailed and lengthy introduction to flywheel design, construction , use here)

Pentadyne, in Sun Valley, California, has developed a flywheel that supplies up to 120 kW of electricity for up to 20 seconds, or any other combination of 2400 kW-seconds.

Precise Power Systems, of Palmetto, Florida, is a developer of flywheel power systems for power protection applications.