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Storing Wind Power for Electricity

Wind Powered Electricity When the Wind Doesn't Blow

There are many problems that must be addressed when planning a wind farm. Most can be solved through proper site selection. The problem of the variability of the wind can only be partially addressed this way. The true solution to the wind variability problem can only be found in storing wind power. There are a number of storage solutions possible.

There are actually two types of wind variability problem. The first is the minor variation in wind speed. This causes variations in the production of electricity; variations that must be evened out to control the power network.  The second is the sudden starting and stopping of wind flow. These sudden changes can result in the crash of the electrical system.

Flywheels for Storage of Momentum         

Flywheels are a classical tool for the temporary storage of energy. Energy is applied to a specially designed heavy wheel. The wheel is designed to turn with minimal energy losses to friction. To get the stored energy out the turning wheel it is hooked up to other machinery.

In a wind farm the heavy wheel is at the hub of each wind mill (NAS, Environmental Impact of Wind-Energy Projects). The large mass makes the windmill slow to accelerate up to speed and slow to come to a stop. This inertia spreads out the increase and decrease in electrical production during the minor changes in wind speed typical in a normal environment.

Batteries for Electrical Storage

Everyone is familiar with using batteries to store electricity. The problem is that the amount of energy that must be stored to compensate for the sudden loss of wind is huge. They typical lead-acid car battery is simply not designed to take that type load and discharge time. A new technology is needed.

A Japanese company, NGK Insulators, has designed a sodium-sulfur battery for this type application. They are installing a 20-module battery at a wind farm near Luverne, MN. It will be able to store 7.2 megawatt-hours of electricity. The 80-ton battery is the size of two semi-trailers. "Fully charged, the battery could power 500 homes for more than seven hours."

Hydrogen for Chemical Storage

Hydrogen has been mentioned as a power storage medium for large solar power systems. It can also be used to store power for wind farms. The excess electricity produced during windy periods would be used to produce hydrogen from water by electrolysis. When the wind flow stopped, the hydrogen would be fed to a fuel cell to produce electricity. 

Air Pressure for Wind Storage

Another method of energy storage would be to use compressed air storage. Excess electricity from the wind farm would power compressors that would fill large pressure tanks with high pressure air. When the flow of wind stopped, the air in the tanks would be used to turn high-speed turbine generators. A German company, RWE Power, is working on a system to increase the efficiency of compressed air storage.

For wind power work as a major part of the electrical power generation system certain problems must be overcome. One of the largest is the smoothing out the variations in electrical generation rates due to wind variation. A number of different storage options exist; each with different strengths and weaknesses. The selection of the appropriate storage system is an important part of wind farm design.

References

  • http://hsdailywire.com/single.php?id=5286
  • http://hsdailywire.com/single.php?id=5657
Submitted by SuperGreenMe on Oct 31, 2008